- Email: [email protected]
Skeletal muscle-resident MSCs and bone formation
BON-10776; No. of pages: 5; 4C: 2, 4 Bone xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Bone
Review
2Q1
Skeletal muscle-resident MSCs and bone formation
3Q3
Dario R. Lemos, Christine Eisner, Fabio M.V. Rossi ⁎
4 5
Biomedical Research Centre, The University of British Columbia, 2222 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada Faculty of Medicine, The University of British Columbia, 317-2194 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
6
a r t i c l e
7 8 9 10 11
Article history: Received 29 January 2015 Revised 28 May 2015 Accepted 17 June 2015 Available online xxxx
12 13 24 14 15 16
Keywords: Skeletal muscle MSC Bone formation Fracture repair
a b s t r a c t
R O
i n f o
E . . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
C
. . . . . . . .
E
. . . . . . . .
R
1. Growing up together . . . . . . . . . 2. Keeping in touch . . . . . . . . . . . 3. A cellular source for ectopic ossification 4. A role for inflammatory cytokines . . . 5. Telling them apart . . . . . . . . . . 6. Local potential . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . .
T
Contents
. . . . . . . .
. . . . . . . .
N C O
39
1. Growing up together
41
Skeletal muscle and bone arise from the paraxial mesoderm. Maturation and delamination of the somites result in compartmentalization and differentiation of these two lineages; the axial skeleton arises from the sclerotome, skeletal muscle precursors from the myotome and the connective tendons arise from the syndetome; a developmentally distinct somitic compartment [1,2]. During early embryogenesis multiple regulatory interactions take place between these compartments. For example the myotome releases secreted factors including FGF4 and FGF6 (Fig. 1 A1), which induce Sox9 and Scx expression in sclerotome cells (Fig. 1 A2) and thus play an instructive role in pushing them toward differentiation into chondrocytes and tenocytes, respectively [3]. Interactions between skeletal muscle and bone continue in
44 45 46 47 48 49 50 51 52
U
40
42 43
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
0 0 0 0 0 0 0 0
R
31 32 33 34 35 36 37 38
17 18 19 20 21 22 23
D
P
Recent research has highlighted the importance of bone and muscle interactions during development and regeneration. There still remains, however, a large gap in the current understanding of the cells and mechanisms involved in this interplay. In particular, how muscle-derived cells, specifically mesenchymal stromal cells (MSCs), can impact bone regeneration or lead to pathologic ectopic bone formation is unclear. Here, a review is given of the evidence supporting the contribution of muscle-derived MSC to bone regeneration and suggesting a critical role for the inflammatory milieu. This article is part of a Special Issue entitled “Muscle Bone Interactions”. © 2015 Published by Elsevier Inc.
28 26 25 27 30 29
O
1Q2
F
journal homepage: www.elsevier.com/locate/bone
⁎ Corresponding author at: Biomedical Research Centre, The University of British Columbia, 2222 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada. E-mail address: [email protected] (F.M.V. Rossi).
late development and in the postnatal period when muscle contractions shape skeletal morphogenesis by modulating the organization of chondrocyte intercalation, thus shaping the cartilaginous template that guides skeletal formation (Fig. 1 B1) [4]. Load-bearing muscle contractions also influence the morphology of mature bone by stimulating mechanosensing osteocytes, helping to regulate bone turnover, and ultimately affecting bone mass and strength (Fig. 1 B2) [5].
53
2. Keeping in touch
60
Bone is a renewable tissue that undergoes continuous remodelling throughout life and possesses the capacity to regenerate after injury. Bone fracture healing is a complex process that recapitulates embryonic bone development and typically involves both intramembranous and endochondral bone formation [6]. Intramembranous bone formation occurs under the periosteum and involves differentiation of osteoblasts and direct deposition of bone matrix, while endochondral bone formation, which occurs adjacent to the fracture site and surrounding soft
61
http://dx.doi.org/10.1016/j.bone.2015.06.013 8756-3282/© 2015 Published by Elsevier Inc.
Please cite this article as: D.R. Lemos, et al., Skeletal muscle-resident MSCs and bone formation, Bone (2015), http://dx.doi.org/10.1016/ j.bone.2015.06.013
54 55 56 57 58 59
62 63 64 65 66 67 68
2
D.R. Lemos et al. / Bone xxx (2015) xxx–xxx
PRE-NATAL
Myotome
Tenocytes
A2
Scx Sox9
Sclerotome
Chondrocytes
POST-NATAL
B2
Mechanosensing and Bone Turnover
Bone Damage
TNF-α IL-6
Muscle Resident MSC
E
ADULT
D
P
Bone
Osteoblast
C
E R
Skeletal Patterning
Skeletal Muscle Contractions
Muscle Damage
Differentiation
Ossification
Differentiation Migration
E
Blood Ectopic Bone Formation Vessel
Inflammation? HSCs? Ectopic Bone Marrow Formation
N
C
O
R
Ossification, Bone Repair
Tendons
C
T
D
B1
R O
Cartilage
F
A1 FGF4 FGF6
O
Transverse Section of Embryo
69 70 71 72 73 74 75 76 77 78 79 80 81 82
U
Fig. 1. Overview of the relationships between bone and muscle during development and in the regenerative process.
tissues, relies heavily on soft callus formation, vascularization and the formation of a cartilaginous matrix that is replaced by woven bone [7]. Osteoblasts, the cells responsible for depositing the new bone matrix, play a crucial role in both forms of bone formation and derive from the mesenchyme, through differentiation of fibroblast-like mesenchymal progenitor cells. While mesenchymal stem cells (MSCs) present in the bone marrow have long been believed to be the source of osteoprogenitors [8,9], several lines of evidence support the contribution of mesenchymal progenitors residing in surrounding tissues to this lineage. The pro-osteogenic role of surrounding tissues was first suggested by studies showing that open fractures heal slower than closed fractures. Two tissues that are in close proximity to bone, the fascio-cutaneous tissue and the skeletal muscle, can drastically improve the outcome of its regeneration [10,11].
A pro-regenerative role for skeletal muscle has also been reported in experimental studies in which the use of muscle-flap coverage in canine and murine tibial fracture models has been shown to increase both the strength of the union and bone mineral content at the fracture site [10, 12]. This has been attributed at least in part to the increased vascularization of the fracture site induced by the apposition of muscle tissue [13, 14]. However, growing evidence supports the novel notion that the mesenchymal compartment of the skeletal muscle, which harbours mesenchymal stem and progenitor cells [15], may constitute a source of osteogenic cells. In support of this hypothesis, Lee et al. (2000) first identified a population of muscle-derived CD34+: Sca-1+: CD45-progenitor cells with osteogenic potential [16]. However a shortcoming of this early study resides in the fact that since no clonal analysis or lineage tracing was preformed, the methodology used to isolate and study these
Please cite this article as: D.R. Lemos, et al., Skeletal muscle-resident MSCs and bone formation, Bone (2015), http://dx.doi.org/10.1016/ j.bone.2015.06.013
83 84 85 86 87 88 89 90 91 92 93 94 95 96
D.R. Lemos et al. / Bone xxx (2015) xxx–xxx
4. A role for inflammatory cytokines
149
It has been proposed that in the case of traumatic bone injury, the contribution of bone-resident progenitors to fracture repair is reduced due to a concomitant loss of the adjacent periosteal and marrow tissues [25], which contain the majority of osteogenic stem cells [26]. In this scenario, multi-potent mesenchymal stromal cells (MMSCs) could migrate from adjacent skeletal muscle to the site of injury guided by proinflammatory cytokines [25]. In fact, two cytokines, TNF-a and IL-6, have been recently suggested to act as both chemoattractants and pro-osteogenic factors in fractures (Fig. 1 D) [25]. Specifically, musclederived stromal cell migration and ALP activity were shown to be
121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146
150 151 152 153 154 155 156 157 158
C
119 120
E
117 118
R
116
R
114 115
N C O
112 113
U
110 111
5. Telling them apart
178
Despite the recent advances, several gaps remain in our knowledge of muscle and bone interactions during regeneration. Understanding the precise contribution of cells from muscle to bone has been impossible due to a lack of lineage-tracing tools capable of distinguishing mesenchymal progenitor cells derived from different sites. Whether a marker allowing such distinction may be found depends on whether multipotent stromal cells from distinct anatomical locations are actually developmentally distinct, or whether, on the contrary, they represent a diffused cell system, just like endothelium, that can arise from multiple developmental origins but is functionally convergent to the point of being near indistinguishable based on single markers [29]. Essential to solving this conundrum is a deeper comparative analysis between muscle and bone-derived MMSCs to identify markers that might help distinguish the two populations. Thus, tracing muscle and bone-derived MMSCs would potentially permit distinction between the actual contributions of each population to the regenerative process. In this regard, some of the remaining questions are whether muscle-derived MMSCs always contribute to bone regeneration regardless of the extent of injury, or whether overlying muscle damage needs to be associated with the bone injury for muscle-derived MMSC contribution. As mentioned above, Tie2 can be used to identify a population of mesenchymal progenitors with osteogenic potential within the skeletal muscle. The limitations of this marker, however, reside in that it also labels endothelial cells, an issue that can be solved by using additional markers such as VE-cadherin and CD31 [21]. Other markers, such as TCF4, which labels muscle resident fibroblasts [30,31], or PDGFRα, which in turn labels a population of multipotent mesenchymal fibro/adipogenic progenitors (FAPs) with latent osteogenic potential [23,24], have not yet been explored. An advantage of tracing MSCs with PDGFRα is that, in the muscle, it is uniquely present in mesenchymal progenitors (Fig. 2a), with undetected expression in endothelial, myogenic and immune cells. On the other hand, BMMSCs express PDGFRα as well [32], which would make it a poor tool for distinguishing the two MSC populations (Fig. 2b).
179 180
6. Local potential
212
Despite the fact that they are not unique in their ability to differentiate into osteoblasts, a property that may be unique to BMMSCs, is their capacity to organize haematopoiesis. This property was first described by Friedenstein in his early studies on BMMSCs [33]. BMMSCs play an important role in regulating the haematopoietic stem cell (HSC) niche via BMP [34] and Angiopoietin 1/Tie2 signalling [35]. This property is; reminiscent of the trophic role played by their muscle resident counterparts during skeletal muscle regeneration [23]. More in-detail analysis
213
F
148
108 109
O
147
The question of whether muscle-resident MSCs can give rise to bone as a consequence of pathologically overactive signalling pathways is crucially relevant for patients affected by Fibrodysplasia Ossificans Progressiva (FOP). With an incidence of 1 in every 2 million people, FOP results from an autosomal dominant allele carrying a missense mutation in the BMP Type 1 receptor, Alk2 (ACVRI) [17]. In these patients, muscle, tendons and ligaments become ossified either spontaneously or more often, following injury [18]. This replacement of the original tissues with heterotopic bone causes severe and progressive loss of mobility. An important step toward identifying the cellular substrate of FOP and potentially modelling the disease has recently been taken. By means of lineage tracing using Tie2::Cre/R26R mice, Lounev et al. (2009) identified a population of muscle-resident Tie2 + progenitor cells that are capable of osteogenic differentiation in response to BMP stimulation in situ (Fig. 1 C) [19]. These progenitors can differentiate into osteogenic cells in the context of regenerating skeletal muscles of NseBMP4 mice, in which BMP4 is exogenously expressed at the cholinergic innervations of neuromuscular junctions [19,20]. Further characterization of this Tie2+ cell population has shown that the sub-fraction of cells contributing to ectopic bone formation is CD31−:CD45−:PDGFRa+:Sca-1+ [21], a marker combination that has been recently described to identify MSCs in mouse [22–24]. Similar to what was described by Lee et al., these muscle-resident CD31 −:CD45 −:PDGFRa +:Sca-1 + mesenchymal progenitors form heterotopic bone in response to exogenous BMP2 [21]. Eight days after intramuscular BMP2 injection into Tie2::Cre/R26 NG mice, in which Tie2 + cells can be traced by means of GFP expression, Sox9-expressing, Tie2 +:CD31 − cells with chondroprogenitor characteristics are found in the interstitial spaces among the fibres [21]. By 15 days after the injection, the ectopic cartilage is replaced by bone and Tie2 +:CD31 − cells found in the area of heterotopic ossification express the osteoblast marker Osx (Sp7) [21]. The results suggest that this pathological process recapitulates developmental endochondral ossification, although an important ontogenetic distinction between normotopic bone and heterotopic BMP2-induced ossifications can be made in that normotopic bone does not appear to derive from Tie2-expressing osteogenic progenitors [19]. Importantly, 90% of the CD31 −:Tie2 + progenitors were also PDGFRa +:Sca-1 + and cells expressing the same markers were observed spontaneously differentiating into adipocytes in vivo, indicating that this population is multi-potent [21].
R O
107
103
159 160
P
3. A cellular source for ectopic ossification
101 102
induced in vitro by conditioned media from fractured bone cultures, and both responses could be inhibited by antibodies against TNF-a and IL-6 [25]. A dose-dependent effect of TNF-a on muscle-derived MMSC has been reported, with low concentrations acting as a chemoattractant and medium concentrations inducing osteogenic differentiation [25]. The role of TNF-a in bone fracture healing was also proposed based on the observation that in TNF-a receptor p55/p75 knockout mice fracture healing is delayed [27]. In particular, the early stages of the regenerative process (chondrogenesis and endochondrial tissue resorption) are significantly affected in these animals, suggesting a role for this cytokine in MMSC chondrogenic differentiation [27]. On the other hand, impaired IL-6 signalling results in callus persistence with lower mineral/ matrix ratios [28], which could be consistent with a proposed role on osteogenic progenitors. Altogether, this body of data suggests that muscle-derived MMSCs may contribute to bone regeneration by migrating to the site of injury and differentiating into osteoblasts, a process that can be hijacked and give rise to ectopic bone formation within muscle in pathological situations (Figs. 1 C, D).
D
106
99 100
T
104 105
cells did not guarantee a homogenous cell population. The osteogenic capacity of Sca-1+ cells was shown in vitro, upon BMP-2 stimulation, and in vivo, in experiments in which the cells were modified to express recombinant human BMP-2 and transplanted into the hindlimb of SCID mice [16]. In summary, this study showed that muscle contains a population that, under the appropriate conditions, can give rise to osteogenic progeny. Importantly, however, no evidence was provided that this could happen under physiological conditions in vivo—i.e. in the absence of pharmacological amounts of exogenous growth factors-.
E
97 98
3
Please cite this article as: D.R. Lemos, et al., Skeletal muscle-resident MSCs and bone formation, Bone (2015), http://dx.doi.org/10.1016/ j.bone.2015.06.013
161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177
181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211
214 215 216 217 218 219 220
4
D.R. Lemos et al. / Bone xxx (2015) xxx–xxx
B
F
A
O
BM
R O
CB
234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262
263
Conclusion
276
In sum, the body of experimental evidence strongly indicates that muscle-resident MSCs can differentiate into osteoblasts and give rise to bone, yet questions still remain as to what physiological signals and events drive those cells into the osteogenic lineage in vivo. Here, a role for the haematopoietic system is evident, contributing not only to the recruitment of MSCs but possibly to the activation of the osteogenic programme as well. Given the great influence of haematopoietic cells on the osteogenic activity of muscle resident-MSCs, a better understanding of the inflammatory milieu both in regeneration and disease is at this point absolutely necessary.
277
References
287
E
D
the final ossicle. Most recently, a distinct population of Gremlin-1 positive self-renewing stem cells capable of contributing to bone, cartilage and reticular stroma during development and in bone regeneration, but not to adipogenesis or to perisinusoidal mesenchymal cells has been described [42]. These cells are likely to be distinct from the mesenchymal progenitors found in muscle, which resemble perisinusoidal cells in their perivascular location, trophic properties and in that they are strongly adipogenic and incapable of spontaneous osteogenic differentiation in vitro [23]. Whether there is a lineage relationship between these two types of mesenchymal stem cells, and whether the induction of osteogenic potential in muscle-resident FAPs requires the formation of osteochondrogenic progenitors as an intermediate are currently unclear [43].
T
C
E
232 233
R
230 231
R
228 229
O
226 227
C
224 225
of the BMMSC population has distinguished the existence of two subpopulations based on the expression of the cell adhesion molecule CD146 [36]. Thus, CD146high cells are both osteogenic and capable of generating a haematopoietic niche, whereas CD146lo cells remain exclusively osteogenic [36]. The activity of BMMSCs, in turn, is regulated by parathyroid hormone (PTH) and PTH-related protein (PTHrP) via the PTH receptor (PPR) [37,38]. In addition to PTH/PTHrP signalling, BMMSC activity is also regulated by erythropoietin (EPO), via Stat-5 signalling [39]. Expression of EPO-R in BMMSCs has been shown to be required for bone marrow organization in subcutaneous xenotransplantation experiments in vivo [39]. Unlike the well-characterized BMMSCs, the specific characteristics of skeletal muscle MSCs remain largely obscure, in particular regarding their heterogeneity. Here again, questions arise regarding potential similarities with BMMSCs, at both the phenotypic and functional levels. Whereas local BMP2 delivery results in expression of osteoblast markers and ectopic ossification [19], no evidence has been provided that the bony structures harbour a haematopoietic niche. One possibility is that ectopic haematopoiesis does develop but only transiently, as suggested by the work of Kawai et al. [40]. Kawai reported that intramuscular BMP delivery leads not only to ectopic ossification, but also to bone marrow formation [40]. The ectopic bone marrow, however, is transient, with the stroma differentiating into adipose tissue within two weeks after formation [40]. Another possibility is that development—and perhaps maintenance—of an ectopic bone marrow is dependent upon the immune cell milieu present in the tissue (Fig. 1 E1–3). It has been shown that progression of FOP can be greatly delayed during the stage of aplastic anemia that develops as a consequence of the immunosuppressive therapy preceding bone marrow transplantation [41]. This clinical observation suggested that the immune system plays a central role in the development of FOP, but it also triggered the question of how much, if at all, haematopoietic stem cells (HSCs) could contribute to ectopic bone formation. Experiments involving transplantation of bone marrow cells from Rosa26RLacZ mice into mice treated with intramuscular rhBMP4 were carried out by Kaplan et al. [41]. The data indicated that haematopoietic cells are involved in the early stages of ectopic ossification, during the development of the fibroproliferative response, but not during the chondrogenic stage of anlagen formation [41]. Haematopoietic cells later return to the site of lesion to repopulate the ectopic ossicles [41]. Most importantly however, at no point throughout the process were haematopoietic cells observed contributing to the nascent structure or
N
222 223
U
221
P
Fig. 2. The distribution of PDGFRα-expressing cells in transgenic PDGFRα: H2b-EGFP/Cdh5:Cre/Rosa TdTomato mice reveals similarities between the distribution of these mesenchymal progenitors in bone and muscle. A) Skeletal muscle; B) bone. Green (nuclear H2b-EGFP) labels mesenchymal cells, most of which are associated with the vasculature in both tissues. Red (VE-cadherin Cre-driven TdTomato) represents vasculature. Blue = Dapi. BM = bone marrow. CB = compact bone.
[1] A.E. Brent, R. Schweitzer, C.J. Tabin, A somitic compartment of tendon progenitors, Cell 113 (2003) 235–248. [2] J. Dubrulle, O. Pourquie, Welcome to syndetome: a new somitic compartment, Dev Cell 4 (2003) 611–612. [3] A.E. Brent, T. Braun, C.J. Tabin, Genetic analysis of interactions between the somitic muscle, cartilage and tendon cell lineages during mouse development, Development 132 (2005) 515–528. [4] Y. Shwartz, Z. Farkas, T. Stern, A. Aszódi, E. Zelzer, Dev Biol 370 (2012) 154–163. [5] R.J. Wood, E.C. O'Neill, Resistance training in type II diabetes mellitus: impact on areas of metabolic dysfunction in skeletal muscle and potential impact on bone, J Nutr Metab 2012 (2012) 1–13. [6] T.A. Einhorn, The cell and molecular biology of fracture healing, Clin Orthop Relat Res (1998) S7–S21. [7] R. Dimitriou, E. Tsiridis, P.V. Giannoudis, Current concepts of molecular aspects of bone healing, Injury 36 (2005) 1392–1404. [8] P. Bianco, P.G. Robey, P.J. Simmons, Mesenchymal stem cells: revisiting history, concepts, and assays, Cell Stem Cell 2 (2008) 313–319.
Please cite this article as: D.R. Lemos, et al., Skeletal muscle-resident MSCs and bone formation, Bone (2015), http://dx.doi.org/10.1016/ j.bone.2015.06.013
264 265 266 267 268 269 270 271 272 273 274 275
278 279 280 281 282 283 284 285 286
288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304
D.R. Lemos et al. / Bone xxx (2015) xxx–xxx
E
D
P
R O
O
F
[26] C. Colnot, Skeletal cell fate decisions within periosteum and bone marrow during bone regeneration, J Bone Miner Res 24 (2009) 274–282. [27] L.C. Gerstenfeld, T.-J. Cho, T. Kon, T. Aizawa, A. Tsay, J. Fitch, et al., Impaired fracture healing in the absence of TNF-α signaling: the role of TNF-α in endochondral cartilage resorption, J Bone Miner Res 18 (2003) 1584–1592. [28] X. Yang, B.F. Ricciardi, A. Hernandez-Soria, Y. Shi, N. Pleshko Camacho, M.P.G. Bostrom, Callus mineralization and maturation are delayed during fracture healing in interleukin-6 knockout mice, Bone 41 (2007) 928–936. [29] D.R. Lemos, B. Paylor, C. Chang, A. Sampaio, T.M. Underhill, F.M.V. Rossi, Functionally convergent white adipogenic progenitors of different lineages participate in a diffused system supporting tissue regeneration, Stem Cells 30 (2012) 1152–1162. [30] M.M. Murphy, J.A. Lawson, S.J. Mathew, D.A. Hutcheson, G. Kardon, Satellite cells, connective tissue fibroblasts and their interactions are crucial for muscle regeneration, Development 138 (2011) 3625–3637. [31] S.J. Mathew, J.M. Hansen, A.J. Merrell, M.M. Murphy, J.A. Lawson, D.A. Hutcheson, et al., Connective tissue fibroblasts and Tcf4 regulate myogenesis, Development 138 (2010) 371–384. [32] S. Morikawa, Y. Mabuchi, Y. Kubota, Y. Nagai, K. Niibe, E. Hiratsu, et al., Prospective identification, isolation, and systemic transplantation of multipotent mesenchymal stem cells in murine bone marrow, J Exp Med 206 (2009) 2483–2496. [33] A. Friedenstein, R.K. Chailakhyan, N.V. Latsinik, A.F. Panasyuk, I.V. Keiliss-Borok, Stromal cells responsible for transferring the microenvironment of the hematopoietic tissues, Transplantation 17 (1974) 331–340. [34] J. Zhang, C. Niu, L. Ye, H. Huang, X. He, W.-G. Tong, et al., Identification of the haematopoietic stem cell niche and control of the niche size, Nat Cell Biol 425 (2003) 836–841. [35] F. Arai, A. Hirao, M. Ohmura, H. Sato, S. Matsuoka, K. Takubo, et al., Tie2/ angiopoietin-1 signaling regulates hematopoietic stem cell quiescence in the bone marrow niche, Cell 118 (2004) 149–161. [36] B. Sacchetti, A. Funari, S. Michienzi, S. Di Cesare, S. Piersanti, I. Saggio, et al., Selfrenewing osteoprogenitors in bone marrow sinusoids can organize a hematopoietic microenvironment, Cell 131 (2007) 324–336. [37] L.M. Calvi, G.B. Adams, K.W. Weibrecht, J.M. Weber, D.P. Olson, M.C. Knight, et al., Osteoblastic cells regulate the haematopoietic stem cell niche, Nat Cell Biol 425 (2003) 841–846. [38] K.A. Moore, I.R. Lemischka, Stem cells and their niches, Science 311 (2006) 1880–1885. [39] T. Yamaza, Y. Miura, K. Akiyama, Y. Bi, W. Sonoyama, S. Gronthos, et al., Mesenchymal stem cell-mediated ectopic hematopoiesis alleviates aging-related phenotype in immunocompromised mice, Blood 113 (2009) 2595–2604. [40] M. Kawai, H. Hattori, K. Yasue, H. Mizutani, M. Ueda, T. Kaneda, et al., Development of hemopoietic bone marrow within the ectopic bone induced by bone morphogenic protein, Blood Cells Mol Dis 20 (1994) 191–199. [41] F.S. Kaplan, D.L. Glaser, E.M. Shore, R.J. Pignolo, M. Xu, Y. Zhang, et al., Hematopoietic stem-cell contribution to ectopic skeletogenesis, J Bone Joint Surg Am 89 (2007) 347. [42] D.L. Worthley, M. Churchill, J.T. Compton, Y. Tailor, M. Rao, Y. Si, et al., Gremlin 1 identifies a skeletal stem cell with bone, cartilage, and reticular stromal potential, Cell 160 (2015) 269–284. [43] C.K.F. Chan, E.Y. Seo, J.Y. Chen, D. Lo, A. McArdle, R. Sinha, et al., Identification and specification of the mouse skeletal stem cell, Cell 160 (2015) 285–298.
N C O
R
R
E
C
T
[9] A.J. Friedenstein, Osteogenic stem cells in bone marrow, in: J.N. Heersche, J.A. Kanis (Eds.),Bone and Mineral Research, vol. 7, Elsevier, Amsterdam 1990, pp. 243–272. [10] L.E. Harry, A. Sandison, E.M. Paleolog, U. Hansen, M.F. Pearse, J. Nanchahal, Comparison of the healing of open tibial fractures covered with either muscle or fasciocutaneous tissue in a murine model, J Orthop Res 26 (2008) 1238–1244. [11] H.S. Byrd, G. Cierny, J.B. Tebbetts, The management of open tibial fractures with associated soft-tissue loss: external pin fixation with early flap coverage, Plast Reconstr Surg 68 (1981) 73–82. [12] R.R. Richards, M.D. McKee, C.B. Paitich, G.I. Anderson, J.T. Bertoia, A comparison of the effects of skin coverage and muscle flap coverage on the early strength of union at the site of osteotomy after devascularization of a segment of canine tibia, J Bone Joint Surg 73 (1991) 1323–1330. [13] R.R. Richards, E.C. Orsini, J.L. Mahoney, R. Verschuren, The influence of muscle flap coverage on the repair of devascularized tibial cortex: an experimental investigation in the dog, Plast Reconstr Surg 79 (1987) 946–958. [14] R.R. Richards, E.H. Schemitsch, Effect of muscle flap coverage on bone blood flow following devascularization of a segment of tibia: an experimental investigation in the dog, J Orthop Res 7 (1989) 550–558. [15] R.N. Judson, R.N. Judson, R.-H. Zhang, R.-H. Zhang, F.M.A. Rossi, F.M.A. Rossi, Tissueresident mesenchymal stem/progenitor cells in skeletal muscle: collaborators or saboteurs? FEBS J 280 (2013) 4100–4108. [16] J.Y. Lee, Z. Qu-Petersen, B. Cao, S. Kimura, R. Jankowski, J. Cummins, et al., Clonal isolation of muscle-derived cells capable of enhancing muscle regeneration and bone healing, J Cell Biol 150 (2000) 1085–1100. [17] E.M. Shore, M. Xu, G.J. Feldman, D.A. Fenstermacher, T.-J. Cho, I.H. Choi, et al., A recurrent mutation in the BMP type 1 receptor ACVR1 causes inherited and sporadic fibrodysplasia ossificans progressiva, Nat Genet 38 (2006) 525–527. [18] F.S. Kaplan, S.A. Chakkalakal, E.M. Shore, Fibrodysplasia ossificans progressiva: mechanisms and models of skeletal metamorphosis, Dis Model Mech 5 (2012) 756–762. [19] V.Y. Lounev, R. Ramachandran, M.N. Wosczyna, M. Yamamoto, A.D.A. Maidment, E.M. Shore, et al., Identification of progenitor cells that contribute to heterotopic skeletogenesis, J Bone Joint Surg Am 91 (2009) 652. [20] L. Kan, M. Hu, W.A. Gomes, J.A. Kessler, Transgenic mice overexpressing BMP4 develop a fibrodysplasia ossificans progressiva (FOP)-like phenotype, Am J Pathol 165 (2004) 1107–1115. [21] M.N. Wosczyna, A.A. Biswas, C.A. Cogswell, D.J. Goldhamer, Multipotent progenitors resident in the skeletal muscle interstitium exhibit robust BMP-dependent osteogenic activity and mediate heterotopic ossification, J Bone Miner Res 27 (2012) 1004–1017. [22] D.D. Houlihan, Y. Mabuchi, S. Morikawa, K. Niibe, D. Araki, S. Suzuki, et al., Isolation of mouse mesenchymal stem cells on the basis of expression of Sca-1 and PDGFR-a, Nat Protoc 7 (2012). [23] A.W.B. Joe, L. Yi, A. Natarajan, F. Le Grand, L. So, J. Wang, et al., Muscle injury activates resident fibro/adipogenic progenitors that facilitate myogenesis, Nat Cell Biol 12 (2010) 153–163. [24] A. Uezumi, T. Ito, D. Morikawa, N. Shimizu, T. Yoneda, M. Segawa, et al., Fibrosis and adipogenesis originate from a common mesenchymal progenitor in skeletal muscle, J Cell Biol 124 (2011) 3654–3664. [25] G.E. Glass, J.K. Chan, A. Freidin, M. Feldmann, N.J. Horwood, J. Nanchahal, TNF-alpha promotes fracture repair by augmenting the recruitment and differentiation of muscle-derived stromal cells, Proc Natl Acad Sci U S A 108 (2011) 1585–1590.
U
305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 408
5
Please cite this article as: D.R. Lemos, et al., Skeletal muscle-resident MSCs and bone formation, Bone (2015), http://dx.doi.org/10.1016/ j.bone.2015.06.013
357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407
Contents lists available at ScienceDirect
Bone
Review
2Q1
Skeletal muscle-resident MSCs and bone formation
3Q3
Dario R. Lemos, Christine Eisner, Fabio M.V. Rossi ⁎
4 5
Biomedical Research Centre, The University of British Columbia, 2222 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada Faculty of Medicine, The University of British Columbia, 317-2194 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
6
a r t i c l e
7 8 9 10 11
Article history: Received 29 January 2015 Revised 28 May 2015 Accepted 17 June 2015 Available online xxxx
12 13 24 14 15 16
Keywords: Skeletal muscle MSC Bone formation Fracture repair
a b s t r a c t
R O
i n f o
E . . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
C
. . . . . . . .
E
. . . . . . . .
R
1. Growing up together . . . . . . . . . 2. Keeping in touch . . . . . . . . . . . 3. A cellular source for ectopic ossification 4. A role for inflammatory cytokines . . . 5. Telling them apart . . . . . . . . . . 6. Local potential . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . .
T
Contents
. . . . . . . .
. . . . . . . .
N C O
39
1. Growing up together
41
Skeletal muscle and bone arise from the paraxial mesoderm. Maturation and delamination of the somites result in compartmentalization and differentiation of these two lineages; the axial skeleton arises from the sclerotome, skeletal muscle precursors from the myotome and the connective tendons arise from the syndetome; a developmentally distinct somitic compartment [1,2]. During early embryogenesis multiple regulatory interactions take place between these compartments. For example the myotome releases secreted factors including FGF4 and FGF6 (Fig. 1 A1), which induce Sox9 and Scx expression in sclerotome cells (Fig. 1 A2) and thus play an instructive role in pushing them toward differentiation into chondrocytes and tenocytes, respectively [3]. Interactions between skeletal muscle and bone continue in
44 45 46 47 48 49 50 51 52
U
40
42 43
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
0 0 0 0 0 0 0 0
R
31 32 33 34 35 36 37 38
17 18 19 20 21 22 23
D
P
Recent research has highlighted the importance of bone and muscle interactions during development and regeneration. There still remains, however, a large gap in the current understanding of the cells and mechanisms involved in this interplay. In particular, how muscle-derived cells, specifically mesenchymal stromal cells (MSCs), can impact bone regeneration or lead to pathologic ectopic bone formation is unclear. Here, a review is given of the evidence supporting the contribution of muscle-derived MSC to bone regeneration and suggesting a critical role for the inflammatory milieu. This article is part of a Special Issue entitled “Muscle Bone Interactions”. © 2015 Published by Elsevier Inc.
28 26 25 27 30 29
O
1Q2
F
journal homepage: www.elsevier.com/locate/bone
⁎ Corresponding author at: Biomedical Research Centre, The University of British Columbia, 2222 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada. E-mail address: [email protected] (F.M.V. Rossi).
late development and in the postnatal period when muscle contractions shape skeletal morphogenesis by modulating the organization of chondrocyte intercalation, thus shaping the cartilaginous template that guides skeletal formation (Fig. 1 B1) [4]. Load-bearing muscle contractions also influence the morphology of mature bone by stimulating mechanosensing osteocytes, helping to regulate bone turnover, and ultimately affecting bone mass and strength (Fig. 1 B2) [5].
53
2. Keeping in touch
60
Bone is a renewable tissue that undergoes continuous remodelling throughout life and possesses the capacity to regenerate after injury. Bone fracture healing is a complex process that recapitulates embryonic bone development and typically involves both intramembranous and endochondral bone formation [6]. Intramembranous bone formation occurs under the periosteum and involves differentiation of osteoblasts and direct deposition of bone matrix, while endochondral bone formation, which occurs adjacent to the fracture site and surrounding soft
61
http://dx.doi.org/10.1016/j.bone.2015.06.013 8756-3282/© 2015 Published by Elsevier Inc.
Please cite this article as: D.R. Lemos, et al., Skeletal muscle-resident MSCs and bone formation, Bone (2015), http://dx.doi.org/10.1016/ j.bone.2015.06.013
54 55 56 57 58 59
62 63 64 65 66 67 68
2
D.R. Lemos et al. / Bone xxx (2015) xxx–xxx
PRE-NATAL
Myotome
Tenocytes
A2
Scx Sox9
Sclerotome
Chondrocytes
POST-NATAL
B2
Mechanosensing and Bone Turnover
Bone Damage
TNF-α IL-6
Muscle Resident MSC
E
ADULT
D
P
Bone
Osteoblast
C
E R
Skeletal Patterning
Skeletal Muscle Contractions
Muscle Damage
Differentiation
Ossification
Differentiation Migration
E
Blood Ectopic Bone Formation Vessel
Inflammation? HSCs? Ectopic Bone Marrow Formation
N
C
O
R
Ossification, Bone Repair
Tendons
C
T
D
B1
R O
Cartilage
F
A1 FGF4 FGF6
O
Transverse Section of Embryo
69 70 71 72 73 74 75 76 77 78 79 80 81 82
U
Fig. 1. Overview of the relationships between bone and muscle during development and in the regenerative process.
tissues, relies heavily on soft callus formation, vascularization and the formation of a cartilaginous matrix that is replaced by woven bone [7]. Osteoblasts, the cells responsible for depositing the new bone matrix, play a crucial role in both forms of bone formation and derive from the mesenchyme, through differentiation of fibroblast-like mesenchymal progenitor cells. While mesenchymal stem cells (MSCs) present in the bone marrow have long been believed to be the source of osteoprogenitors [8,9], several lines of evidence support the contribution of mesenchymal progenitors residing in surrounding tissues to this lineage. The pro-osteogenic role of surrounding tissues was first suggested by studies showing that open fractures heal slower than closed fractures. Two tissues that are in close proximity to bone, the fascio-cutaneous tissue and the skeletal muscle, can drastically improve the outcome of its regeneration [10,11].
A pro-regenerative role for skeletal muscle has also been reported in experimental studies in which the use of muscle-flap coverage in canine and murine tibial fracture models has been shown to increase both the strength of the union and bone mineral content at the fracture site [10, 12]. This has been attributed at least in part to the increased vascularization of the fracture site induced by the apposition of muscle tissue [13, 14]. However, growing evidence supports the novel notion that the mesenchymal compartment of the skeletal muscle, which harbours mesenchymal stem and progenitor cells [15], may constitute a source of osteogenic cells. In support of this hypothesis, Lee et al. (2000) first identified a population of muscle-derived CD34+: Sca-1+: CD45-progenitor cells with osteogenic potential [16]. However a shortcoming of this early study resides in the fact that since no clonal analysis or lineage tracing was preformed, the methodology used to isolate and study these
Please cite this article as: D.R. Lemos, et al., Skeletal muscle-resident MSCs and bone formation, Bone (2015), http://dx.doi.org/10.1016/ j.bone.2015.06.013
83 84 85 86 87 88 89 90 91 92 93 94 95 96
D.R. Lemos et al. / Bone xxx (2015) xxx–xxx
4. A role for inflammatory cytokines
149
It has been proposed that in the case of traumatic bone injury, the contribution of bone-resident progenitors to fracture repair is reduced due to a concomitant loss of the adjacent periosteal and marrow tissues [25], which contain the majority of osteogenic stem cells [26]. In this scenario, multi-potent mesenchymal stromal cells (MMSCs) could migrate from adjacent skeletal muscle to the site of injury guided by proinflammatory cytokines [25]. In fact, two cytokines, TNF-a and IL-6, have been recently suggested to act as both chemoattractants and pro-osteogenic factors in fractures (Fig. 1 D) [25]. Specifically, musclederived stromal cell migration and ALP activity were shown to be
121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146
150 151 152 153 154 155 156 157 158
C
119 120
E
117 118
R
116
R
114 115
N C O
112 113
U
110 111
5. Telling them apart
178
Despite the recent advances, several gaps remain in our knowledge of muscle and bone interactions during regeneration. Understanding the precise contribution of cells from muscle to bone has been impossible due to a lack of lineage-tracing tools capable of distinguishing mesenchymal progenitor cells derived from different sites. Whether a marker allowing such distinction may be found depends on whether multipotent stromal cells from distinct anatomical locations are actually developmentally distinct, or whether, on the contrary, they represent a diffused cell system, just like endothelium, that can arise from multiple developmental origins but is functionally convergent to the point of being near indistinguishable based on single markers [29]. Essential to solving this conundrum is a deeper comparative analysis between muscle and bone-derived MMSCs to identify markers that might help distinguish the two populations. Thus, tracing muscle and bone-derived MMSCs would potentially permit distinction between the actual contributions of each population to the regenerative process. In this regard, some of the remaining questions are whether muscle-derived MMSCs always contribute to bone regeneration regardless of the extent of injury, or whether overlying muscle damage needs to be associated with the bone injury for muscle-derived MMSC contribution. As mentioned above, Tie2 can be used to identify a population of mesenchymal progenitors with osteogenic potential within the skeletal muscle. The limitations of this marker, however, reside in that it also labels endothelial cells, an issue that can be solved by using additional markers such as VE-cadherin and CD31 [21]. Other markers, such as TCF4, which labels muscle resident fibroblasts [30,31], or PDGFRα, which in turn labels a population of multipotent mesenchymal fibro/adipogenic progenitors (FAPs) with latent osteogenic potential [23,24], have not yet been explored. An advantage of tracing MSCs with PDGFRα is that, in the muscle, it is uniquely present in mesenchymal progenitors (Fig. 2a), with undetected expression in endothelial, myogenic and immune cells. On the other hand, BMMSCs express PDGFRα as well [32], which would make it a poor tool for distinguishing the two MSC populations (Fig. 2b).
179 180
6. Local potential
212
Despite the fact that they are not unique in their ability to differentiate into osteoblasts, a property that may be unique to BMMSCs, is their capacity to organize haematopoiesis. This property was first described by Friedenstein in his early studies on BMMSCs [33]. BMMSCs play an important role in regulating the haematopoietic stem cell (HSC) niche via BMP [34] and Angiopoietin 1/Tie2 signalling [35]. This property is; reminiscent of the trophic role played by their muscle resident counterparts during skeletal muscle regeneration [23]. More in-detail analysis
213
F
148
108 109
O
147
The question of whether muscle-resident MSCs can give rise to bone as a consequence of pathologically overactive signalling pathways is crucially relevant for patients affected by Fibrodysplasia Ossificans Progressiva (FOP). With an incidence of 1 in every 2 million people, FOP results from an autosomal dominant allele carrying a missense mutation in the BMP Type 1 receptor, Alk2 (ACVRI) [17]. In these patients, muscle, tendons and ligaments become ossified either spontaneously or more often, following injury [18]. This replacement of the original tissues with heterotopic bone causes severe and progressive loss of mobility. An important step toward identifying the cellular substrate of FOP and potentially modelling the disease has recently been taken. By means of lineage tracing using Tie2::Cre/R26R mice, Lounev et al. (2009) identified a population of muscle-resident Tie2 + progenitor cells that are capable of osteogenic differentiation in response to BMP stimulation in situ (Fig. 1 C) [19]. These progenitors can differentiate into osteogenic cells in the context of regenerating skeletal muscles of NseBMP4 mice, in which BMP4 is exogenously expressed at the cholinergic innervations of neuromuscular junctions [19,20]. Further characterization of this Tie2+ cell population has shown that the sub-fraction of cells contributing to ectopic bone formation is CD31−:CD45−:PDGFRa+:Sca-1+ [21], a marker combination that has been recently described to identify MSCs in mouse [22–24]. Similar to what was described by Lee et al., these muscle-resident CD31 −:CD45 −:PDGFRa +:Sca-1 + mesenchymal progenitors form heterotopic bone in response to exogenous BMP2 [21]. Eight days after intramuscular BMP2 injection into Tie2::Cre/R26 NG mice, in which Tie2 + cells can be traced by means of GFP expression, Sox9-expressing, Tie2 +:CD31 − cells with chondroprogenitor characteristics are found in the interstitial spaces among the fibres [21]. By 15 days after the injection, the ectopic cartilage is replaced by bone and Tie2 +:CD31 − cells found in the area of heterotopic ossification express the osteoblast marker Osx (Sp7) [21]. The results suggest that this pathological process recapitulates developmental endochondral ossification, although an important ontogenetic distinction between normotopic bone and heterotopic BMP2-induced ossifications can be made in that normotopic bone does not appear to derive from Tie2-expressing osteogenic progenitors [19]. Importantly, 90% of the CD31 −:Tie2 + progenitors were also PDGFRa +:Sca-1 + and cells expressing the same markers were observed spontaneously differentiating into adipocytes in vivo, indicating that this population is multi-potent [21].
R O
107
103
159 160
P
3. A cellular source for ectopic ossification
101 102
induced in vitro by conditioned media from fractured bone cultures, and both responses could be inhibited by antibodies against TNF-a and IL-6 [25]. A dose-dependent effect of TNF-a on muscle-derived MMSC has been reported, with low concentrations acting as a chemoattractant and medium concentrations inducing osteogenic differentiation [25]. The role of TNF-a in bone fracture healing was also proposed based on the observation that in TNF-a receptor p55/p75 knockout mice fracture healing is delayed [27]. In particular, the early stages of the regenerative process (chondrogenesis and endochondrial tissue resorption) are significantly affected in these animals, suggesting a role for this cytokine in MMSC chondrogenic differentiation [27]. On the other hand, impaired IL-6 signalling results in callus persistence with lower mineral/ matrix ratios [28], which could be consistent with a proposed role on osteogenic progenitors. Altogether, this body of data suggests that muscle-derived MMSCs may contribute to bone regeneration by migrating to the site of injury and differentiating into osteoblasts, a process that can be hijacked and give rise to ectopic bone formation within muscle in pathological situations (Figs. 1 C, D).
D
106
99 100
T
104 105
cells did not guarantee a homogenous cell population. The osteogenic capacity of Sca-1+ cells was shown in vitro, upon BMP-2 stimulation, and in vivo, in experiments in which the cells were modified to express recombinant human BMP-2 and transplanted into the hindlimb of SCID mice [16]. In summary, this study showed that muscle contains a population that, under the appropriate conditions, can give rise to osteogenic progeny. Importantly, however, no evidence was provided that this could happen under physiological conditions in vivo—i.e. in the absence of pharmacological amounts of exogenous growth factors-.
E
97 98
3
Please cite this article as: D.R. Lemos, et al., Skeletal muscle-resident MSCs and bone formation, Bone (2015), http://dx.doi.org/10.1016/ j.bone.2015.06.013
161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177
181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211
214 215 216 217 218 219 220
4
D.R. Lemos et al. / Bone xxx (2015) xxx–xxx
B
F
A
O
BM
R O
CB
234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262
263
Conclusion
276
In sum, the body of experimental evidence strongly indicates that muscle-resident MSCs can differentiate into osteoblasts and give rise to bone, yet questions still remain as to what physiological signals and events drive those cells into the osteogenic lineage in vivo. Here, a role for the haematopoietic system is evident, contributing not only to the recruitment of MSCs but possibly to the activation of the osteogenic programme as well. Given the great influence of haematopoietic cells on the osteogenic activity of muscle resident-MSCs, a better understanding of the inflammatory milieu both in regeneration and disease is at this point absolutely necessary.
277
References
287
E
D
the final ossicle. Most recently, a distinct population of Gremlin-1 positive self-renewing stem cells capable of contributing to bone, cartilage and reticular stroma during development and in bone regeneration, but not to adipogenesis or to perisinusoidal mesenchymal cells has been described [42]. These cells are likely to be distinct from the mesenchymal progenitors found in muscle, which resemble perisinusoidal cells in their perivascular location, trophic properties and in that they are strongly adipogenic and incapable of spontaneous osteogenic differentiation in vitro [23]. Whether there is a lineage relationship between these two types of mesenchymal stem cells, and whether the induction of osteogenic potential in muscle-resident FAPs requires the formation of osteochondrogenic progenitors as an intermediate are currently unclear [43].
T
C
E
232 233
R
230 231
R
228 229
O
226 227
C
224 225
of the BMMSC population has distinguished the existence of two subpopulations based on the expression of the cell adhesion molecule CD146 [36]. Thus, CD146high cells are both osteogenic and capable of generating a haematopoietic niche, whereas CD146lo cells remain exclusively osteogenic [36]. The activity of BMMSCs, in turn, is regulated by parathyroid hormone (PTH) and PTH-related protein (PTHrP) via the PTH receptor (PPR) [37,38]. In addition to PTH/PTHrP signalling, BMMSC activity is also regulated by erythropoietin (EPO), via Stat-5 signalling [39]. Expression of EPO-R in BMMSCs has been shown to be required for bone marrow organization in subcutaneous xenotransplantation experiments in vivo [39]. Unlike the well-characterized BMMSCs, the specific characteristics of skeletal muscle MSCs remain largely obscure, in particular regarding their heterogeneity. Here again, questions arise regarding potential similarities with BMMSCs, at both the phenotypic and functional levels. Whereas local BMP2 delivery results in expression of osteoblast markers and ectopic ossification [19], no evidence has been provided that the bony structures harbour a haematopoietic niche. One possibility is that ectopic haematopoiesis does develop but only transiently, as suggested by the work of Kawai et al. [40]. Kawai reported that intramuscular BMP delivery leads not only to ectopic ossification, but also to bone marrow formation [40]. The ectopic bone marrow, however, is transient, with the stroma differentiating into adipose tissue within two weeks after formation [40]. Another possibility is that development—and perhaps maintenance—of an ectopic bone marrow is dependent upon the immune cell milieu present in the tissue (Fig. 1 E1–3). It has been shown that progression of FOP can be greatly delayed during the stage of aplastic anemia that develops as a consequence of the immunosuppressive therapy preceding bone marrow transplantation [41]. This clinical observation suggested that the immune system plays a central role in the development of FOP, but it also triggered the question of how much, if at all, haematopoietic stem cells (HSCs) could contribute to ectopic bone formation. Experiments involving transplantation of bone marrow cells from Rosa26RLacZ mice into mice treated with intramuscular rhBMP4 were carried out by Kaplan et al. [41]. The data indicated that haematopoietic cells are involved in the early stages of ectopic ossification, during the development of the fibroproliferative response, but not during the chondrogenic stage of anlagen formation [41]. Haematopoietic cells later return to the site of lesion to repopulate the ectopic ossicles [41]. Most importantly however, at no point throughout the process were haematopoietic cells observed contributing to the nascent structure or
N
222 223
U
221
P
Fig. 2. The distribution of PDGFRα-expressing cells in transgenic PDGFRα: H2b-EGFP/Cdh5:Cre/Rosa TdTomato mice reveals similarities between the distribution of these mesenchymal progenitors in bone and muscle. A) Skeletal muscle; B) bone. Green (nuclear H2b-EGFP) labels mesenchymal cells, most of which are associated with the vasculature in both tissues. Red (VE-cadherin Cre-driven TdTomato) represents vasculature. Blue = Dapi. BM = bone marrow. CB = compact bone.
[1] A.E. Brent, R. Schweitzer, C.J. Tabin, A somitic compartment of tendon progenitors, Cell 113 (2003) 235–248. [2] J. Dubrulle, O. Pourquie, Welcome to syndetome: a new somitic compartment, Dev Cell 4 (2003) 611–612. [3] A.E. Brent, T. Braun, C.J. Tabin, Genetic analysis of interactions between the somitic muscle, cartilage and tendon cell lineages during mouse development, Development 132 (2005) 515–528. [4] Y. Shwartz, Z. Farkas, T. Stern, A. Aszódi, E. Zelzer, Dev Biol 370 (2012) 154–163. [5] R.J. Wood, E.C. O'Neill, Resistance training in type II diabetes mellitus: impact on areas of metabolic dysfunction in skeletal muscle and potential impact on bone, J Nutr Metab 2012 (2012) 1–13. [6] T.A. Einhorn, The cell and molecular biology of fracture healing, Clin Orthop Relat Res (1998) S7–S21. [7] R. Dimitriou, E. Tsiridis, P.V. Giannoudis, Current concepts of molecular aspects of bone healing, Injury 36 (2005) 1392–1404. [8] P. Bianco, P.G. Robey, P.J. Simmons, Mesenchymal stem cells: revisiting history, concepts, and assays, Cell Stem Cell 2 (2008) 313–319.
Please cite this article as: D.R. Lemos, et al., Skeletal muscle-resident MSCs and bone formation, Bone (2015), http://dx.doi.org/10.1016/ j.bone.2015.06.013
264 265 266 267 268 269 270 271 272 273 274 275
278 279 280 281 282 283 284 285 286
288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304
D.R. Lemos et al. / Bone xxx (2015) xxx–xxx
E
D
P
R O
O
F
[26] C. Colnot, Skeletal cell fate decisions within periosteum and bone marrow during bone regeneration, J Bone Miner Res 24 (2009) 274–282. [27] L.C. Gerstenfeld, T.-J. Cho, T. Kon, T. Aizawa, A. Tsay, J. Fitch, et al., Impaired fracture healing in the absence of TNF-α signaling: the role of TNF-α in endochondral cartilage resorption, J Bone Miner Res 18 (2003) 1584–1592. [28] X. Yang, B.F. Ricciardi, A. Hernandez-Soria, Y. Shi, N. Pleshko Camacho, M.P.G. Bostrom, Callus mineralization and maturation are delayed during fracture healing in interleukin-6 knockout mice, Bone 41 (2007) 928–936. [29] D.R. Lemos, B. Paylor, C. Chang, A. Sampaio, T.M. Underhill, F.M.V. Rossi, Functionally convergent white adipogenic progenitors of different lineages participate in a diffused system supporting tissue regeneration, Stem Cells 30 (2012) 1152–1162. [30] M.M. Murphy, J.A. Lawson, S.J. Mathew, D.A. Hutcheson, G. Kardon, Satellite cells, connective tissue fibroblasts and their interactions are crucial for muscle regeneration, Development 138 (2011) 3625–3637. [31] S.J. Mathew, J.M. Hansen, A.J. Merrell, M.M. Murphy, J.A. Lawson, D.A. Hutcheson, et al., Connective tissue fibroblasts and Tcf4 regulate myogenesis, Development 138 (2010) 371–384. [32] S. Morikawa, Y. Mabuchi, Y. Kubota, Y. Nagai, K. Niibe, E. Hiratsu, et al., Prospective identification, isolation, and systemic transplantation of multipotent mesenchymal stem cells in murine bone marrow, J Exp Med 206 (2009) 2483–2496. [33] A. Friedenstein, R.K. Chailakhyan, N.V. Latsinik, A.F. Panasyuk, I.V. Keiliss-Borok, Stromal cells responsible for transferring the microenvironment of the hematopoietic tissues, Transplantation 17 (1974) 331–340. [34] J. Zhang, C. Niu, L. Ye, H. Huang, X. He, W.-G. Tong, et al., Identification of the haematopoietic stem cell niche and control of the niche size, Nat Cell Biol 425 (2003) 836–841. [35] F. Arai, A. Hirao, M. Ohmura, H. Sato, S. Matsuoka, K. Takubo, et al., Tie2/ angiopoietin-1 signaling regulates hematopoietic stem cell quiescence in the bone marrow niche, Cell 118 (2004) 149–161. [36] B. Sacchetti, A. Funari, S. Michienzi, S. Di Cesare, S. Piersanti, I. Saggio, et al., Selfrenewing osteoprogenitors in bone marrow sinusoids can organize a hematopoietic microenvironment, Cell 131 (2007) 324–336. [37] L.M. Calvi, G.B. Adams, K.W. Weibrecht, J.M. Weber, D.P. Olson, M.C. Knight, et al., Osteoblastic cells regulate the haematopoietic stem cell niche, Nat Cell Biol 425 (2003) 841–846. [38] K.A. Moore, I.R. Lemischka, Stem cells and their niches, Science 311 (2006) 1880–1885. [39] T. Yamaza, Y. Miura, K. Akiyama, Y. Bi, W. Sonoyama, S. Gronthos, et al., Mesenchymal stem cell-mediated ectopic hematopoiesis alleviates aging-related phenotype in immunocompromised mice, Blood 113 (2009) 2595–2604. [40] M. Kawai, H. Hattori, K. Yasue, H. Mizutani, M. Ueda, T. Kaneda, et al., Development of hemopoietic bone marrow within the ectopic bone induced by bone morphogenic protein, Blood Cells Mol Dis 20 (1994) 191–199. [41] F.S. Kaplan, D.L. Glaser, E.M. Shore, R.J. Pignolo, M. Xu, Y. Zhang, et al., Hematopoietic stem-cell contribution to ectopic skeletogenesis, J Bone Joint Surg Am 89 (2007) 347. [42] D.L. Worthley, M. Churchill, J.T. Compton, Y. Tailor, M. Rao, Y. Si, et al., Gremlin 1 identifies a skeletal stem cell with bone, cartilage, and reticular stromal potential, Cell 160 (2015) 269–284. [43] C.K.F. Chan, E.Y. Seo, J.Y. Chen, D. Lo, A. McArdle, R. Sinha, et al., Identification and specification of the mouse skeletal stem cell, Cell 160 (2015) 285–298.
N C O
R
R
E
C
T
[9] A.J. Friedenstein, Osteogenic stem cells in bone marrow, in: J.N. Heersche, J.A. Kanis (Eds.),Bone and Mineral Research, vol. 7, Elsevier, Amsterdam 1990, pp. 243–272. [10] L.E. Harry, A. Sandison, E.M. Paleolog, U. Hansen, M.F. Pearse, J. Nanchahal, Comparison of the healing of open tibial fractures covered with either muscle or fasciocutaneous tissue in a murine model, J Orthop Res 26 (2008) 1238–1244. [11] H.S. Byrd, G. Cierny, J.B. Tebbetts, The management of open tibial fractures with associated soft-tissue loss: external pin fixation with early flap coverage, Plast Reconstr Surg 68 (1981) 73–82. [12] R.R. Richards, M.D. McKee, C.B. Paitich, G.I. Anderson, J.T. Bertoia, A comparison of the effects of skin coverage and muscle flap coverage on the early strength of union at the site of osteotomy after devascularization of a segment of canine tibia, J Bone Joint Surg 73 (1991) 1323–1330. [13] R.R. Richards, E.C. Orsini, J.L. Mahoney, R. Verschuren, The influence of muscle flap coverage on the repair of devascularized tibial cortex: an experimental investigation in the dog, Plast Reconstr Surg 79 (1987) 946–958. [14] R.R. Richards, E.H. Schemitsch, Effect of muscle flap coverage on bone blood flow following devascularization of a segment of tibia: an experimental investigation in the dog, J Orthop Res 7 (1989) 550–558. [15] R.N. Judson, R.N. Judson, R.-H. Zhang, R.-H. Zhang, F.M.A. Rossi, F.M.A. Rossi, Tissueresident mesenchymal stem/progenitor cells in skeletal muscle: collaborators or saboteurs? FEBS J 280 (2013) 4100–4108. [16] J.Y. Lee, Z. Qu-Petersen, B. Cao, S. Kimura, R. Jankowski, J. Cummins, et al., Clonal isolation of muscle-derived cells capable of enhancing muscle regeneration and bone healing, J Cell Biol 150 (2000) 1085–1100. [17] E.M. Shore, M. Xu, G.J. Feldman, D.A. Fenstermacher, T.-J. Cho, I.H. Choi, et al., A recurrent mutation in the BMP type 1 receptor ACVR1 causes inherited and sporadic fibrodysplasia ossificans progressiva, Nat Genet 38 (2006) 525–527. [18] F.S. Kaplan, S.A. Chakkalakal, E.M. Shore, Fibrodysplasia ossificans progressiva: mechanisms and models of skeletal metamorphosis, Dis Model Mech 5 (2012) 756–762. [19] V.Y. Lounev, R. Ramachandran, M.N. Wosczyna, M. Yamamoto, A.D.A. Maidment, E.M. Shore, et al., Identification of progenitor cells that contribute to heterotopic skeletogenesis, J Bone Joint Surg Am 91 (2009) 652. [20] L. Kan, M. Hu, W.A. Gomes, J.A. Kessler, Transgenic mice overexpressing BMP4 develop a fibrodysplasia ossificans progressiva (FOP)-like phenotype, Am J Pathol 165 (2004) 1107–1115. [21] M.N. Wosczyna, A.A. Biswas, C.A. Cogswell, D.J. Goldhamer, Multipotent progenitors resident in the skeletal muscle interstitium exhibit robust BMP-dependent osteogenic activity and mediate heterotopic ossification, J Bone Miner Res 27 (2012) 1004–1017. [22] D.D. Houlihan, Y. Mabuchi, S. Morikawa, K. Niibe, D. Araki, S. Suzuki, et al., Isolation of mouse mesenchymal stem cells on the basis of expression of Sca-1 and PDGFR-a, Nat Protoc 7 (2012). [23] A.W.B. Joe, L. Yi, A. Natarajan, F. Le Grand, L. So, J. Wang, et al., Muscle injury activates resident fibro/adipogenic progenitors that facilitate myogenesis, Nat Cell Biol 12 (2010) 153–163. [24] A. Uezumi, T. Ito, D. Morikawa, N. Shimizu, T. Yoneda, M. Segawa, et al., Fibrosis and adipogenesis originate from a common mesenchymal progenitor in skeletal muscle, J Cell Biol 124 (2011) 3654–3664. [25] G.E. Glass, J.K. Chan, A. Freidin, M. Feldmann, N.J. Horwood, J. Nanchahal, TNF-alpha promotes fracture repair by augmenting the recruitment and differentiation of muscle-derived stromal cells, Proc Natl Acad Sci U S A 108 (2011) 1585–1590.
U
305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 408
5
Please cite this article as: D.R. Lemos, et al., Skeletal muscle-resident MSCs and bone formation, Bone (2015), http://dx.doi.org/10.1016/ j.bone.2015.06.013
357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407