- Email: [email protected]
Targeting Epigenetics to Speed Up Repair
Cell Stem Cell
Previews Targeting Epigenetics to Speed Up Repair Eric Soler1,* and Frank Grosveld2,* 1INSERM
UMR967 CEA/DSV/iRCM, 92265 Fontenay-aux-Roses, France of Cell Biology, Erasmus Medical Center, Rotterdam, The Netherlands *Correspondence: [email protected] (E.S.), [email protected] (F.G.) http://dx.doi.org/10.1016/j.stem.2014.04.018 2Department
In this issue of Cell Stem Cell, Palii et al. reveal that TAL1 is a master regulator of adhesion and migration networks in human endothelial progenitors and that ex vivo treatment with the histone deacetylase inhibitor TSA enables their faster vascularization after ischemic injury. Ischemia is a restriction of tissue blood precursor of endothelial and hemato- due to survival or proliferation defects of supply due to vessel dysfunction, leading poietic lineages during early embryo- the ECFCs but was caused by typical to a shortage of oxygen and tissue dam- genesis. In particular, TAL1 is required endothelial cell properties. They were age. When treating ischemia it is impera- for remodeling of the vasculature during unable to form capillary-like structures tive to restore blood flow quickly in order development, but its potential contribu- after plating on Matrigel and collagen to reestablish oxygen supply and reduce tion to the revascularization properties and showed impaired adhesion properorgan damage. Using endothelial progen- of injected ECFCs was unknown. Brand ties. Moreover, in a Boyden chamber itors to regenerate a defective vasculature and colleagues knocked down TAL1 assay, their migration was severely and increase the rate of vascular repair is expression in ECFCs derived from human reduced toward the chemokine SDF-1 a major goal of cell-based regenerative cord blood and showed their inability to due to reduced expression of the chemotherapies (Figure 1). Endothelial colony- engraft in ischemic muscles and improve kine receptor CXCR4. forming cells (ECFCs) (Yoder et al., 2007) blood flow recovery in a mouse model of Genome-wide mapping of TAL1 bindare particularly suitable for such therapy hindlimb ischemia. This lack of capacity ing sites in ECFCs by chromatin immunoand they can relatively easily be obtained to promote revascularization was not precipitation coupled to high-throughput from human cord blood sequencing (ChIP-Seq) reand peripheral blood. They vealed strong association of can differentiate into endoTAL1 with genes involved in thelial capillary-like structures blood vessel development in vitro, form new functionally and critical regulatory pathactive human blood vessels ways linked to vascular funcin vivo, and enhance revascutions such as PDGF and larization in mouse models of VEGF signaling pathways. ischemia (Pelosi et al., 2014, The analysis of genes funcBenslimane-Ahmim et al., tionally dependent on TAL1 2011). However, the molein ECFCs confirmed its cular mechanisms at play in involvement in the regulation these processes remained of endothelial cell migration largely uncharacterized. In and adhesion via the activathis issue of Cell Stem Cell, tion of multiple effector genes Palii et al. provide an in-depth directly impacting ECFC characterization of the critical functions. For example, the role played by the transcripendothelial-specific junction tion factor TAL1, or SCL, in molecule gene CHD5, the the vascular repair function cell-cell contact molecule of human ECFCs (Palii et al., Ephrin B2 ligand (EFNB2), 2014). and a number of transcription TAL1, a class II basic helixfactors essential for endoloop-helix transcription facthelial functions (e.g. SOX7 Figure 1. Enhanced Recovery from Ischemic Injury by ECFCs Pretreated with TSA tor, is a well-known regulator and HOXA9) are regulated Ischemic injury results in interrupted or lower blood supply to affected tissue. of human hematopoiesis, by TAL1. Interestingly, the Injection of ECFCs helps rescue the blood flow by generating new vasculature with recognized roles in regulatory sequences of at the site of injury. The transcription factor TAL1 is a key factor controlling this process in ECFCs. TAL1 positively regulates target genes by cooperating with T cell leukemia (Palii et al., these targets are already the histone acetyl transferase p300. This action is turned down by histone 2011, Sanda et al., 2012). bound by TAL1 very early in deacetylases (HDACs). Treatment with TSA, an HDAC inhibitor, modifies the TAL1 also plays a key role in development when the debalance between TAL1/p300 and HDACs and enhances TAL1 target gene the hemangioblast, a bipotent velopmental choice between expression in ECFCs, resulting in faster recovery after ischemic injury. Cell Stem Cell 14, May 1, 2014 ª2014 Elsevier Inc. 553
Cell Stem Cell
Previews cardiac, endothelial, and hematopoietic precursor cells still has to be made (Mylona et al., 2013). The mechanism of activation of endothelial genes by TAL1 was further analyzed, based on knowledge of its regulatory functions derived from erythroid cells. Similar to what was known from the erythroid lineage, the p300 histone acetyl transferase (HAT) was shown to co-occupy TAL1 chromatin binding sites in ECFCs and to be required for the expression of TAL1 target genes. Furthermore, p300 binding appears to be dependent on the presence of TAL1 because p300 is lost upon TAL1 knockdown, concomitant with a decrease in histone H3 acetylation and decreased transcriptional activity of target genes. Therefore TAL1 recruits p300 to activate its target genes in ECFCs. Gene regulatory mechanisms involve a balance of activators such as the p300 HATs and repressors such as histone deacetylases (HDACs) at regulatory sites (Wang et al., 2009). Brand and colleagues therefore sought to shift this balance toward activation by using the HDAC inhibitor TSA on ECFCs to increase TAL1-dependent gene transcription. They observe that histone H3 acetylation and the binding of p300 HAT were increased in ex vivo TSA-treated ECFCs, which appears to confirm that the balance of HAT/HDAC has been changed. Genes involved in ECFC migration are activated after TSA treatment, leading to increased migration kinetics in a TAL1-dependent manner. This effect was confirmed in vivo by transplanting ECFCs pretreated with TSA into ischemic mouse muscles, which resulted in a dramatic increase in the rate of blood flow recovery (4 days as compared with 10 days with non-TSA treated cells). Thus, ex vivo treatment with TSA improved the kinetics of ECFC-mediated vascular repair in vivo and was associated with increased arteriole density and
decreased necrosis. Because the speed of blood flow recovery is one of the most critical parameters in clinical settings, pretreatment of ECFCs with HDAC inhibitors could be a useful strategy to improve cell-based therapies. The use of epigenetic drugs ex vivo in clinical settings therefore appears promising and offers the advantage of providing a transient ‘‘functional boost’’ to therapeutic cells prior to injection to maximize their clinical potential. Although the authors do not show which HDACs are involved and where they bind, the observed effect is likely due to a displacement of the ratio between HATs and HDACs at TAL1 chromatin binding sites. Because they observe the presence of GATA sites, a number of good candidate HDACs may be the same as those known in the hematopoietic system (van Riel et al., 2012). A topic for future investigation is which, if any, of these (tissue-specific) cofactors mentioned above mediates or regulates TAL1 function in ECFCs. They may represent new leads to further manipulate the function of TAL1 complexes through additional candidate targets. Clearly, additional questions will have to be resolved before any clinical application can be considered. The most important one will be whether the ex vivo TSA priming and subsequent transplantation protocol would be sufficiently fast to result in therapeutic effects for the most common causes of ischemia. Second, it remains to be seen whether heterologous transplants may result in immunological reactions, requiring treatment with immunosuppressants. It is encouraging, however, that HDAC inhibitors may have the capacity to inhibit rejection by the immune system, at least in some heterologous transplant settings (Sugimoto et al., 2014). Nevertheless, it may be useful to store ECFCs to be able to provide an
554 Cell Stem Cell 14, May 1, 2014 ª2014 Elsevier Inc.
autologous transplant quickly when needed, especially if TSA-primed ECFCs would retain their efficiency after cryopreservation. Such a solution may be useful in a hospital setting for patients with ischemic conditions that develop slowly or for those known to be at high risk for developing ischemia. REFERENCES Benslimane-Ahmim, Z., Heymann, D., Dizier, B., Lokajczyk, A., Brion, R., Laurendeau, I., Bie`che, I., Smadja, D.M., Galy-Fauroux, I., ColliecJouault, S., et al. (2011). J. Thromb. Haemost. 9, 834–843. Mylona, A., Andrieu-Soler, C., Thongjuea, S., Martella, A., Soler, E., Jorna, R., Hou, J., Kockx, C., van Ijcken, W., Lenhard, B., and Grosveld, F. (2013). Blood 121, 2902–2913. Published online Feb 6, 2013. http://dx.doi.org/10.1182/blood2012-11-467654. Palii, C.G., Perez-Iratxeta, C., Yao, Z., Cao, Y., Dai, F., Davison, J., Atkins, H., Allan, D., Dilworth, F.J., Gentleman, R., et al. (2011). EMBO J. 30, 494–509. Palii, C., Ulesevic, B., Fraineu, S., Prackeviciene, E., Griffith, A., Chu, A., Faralli, H., Li, Y., McNeill, B., Sun, J., et al. (2014). Cell Stem Cell 14, this issue, 644–657. Pelosi, E., Castelli, G., and Testa, U. (2014). Blood Cells Mol. Dis. 52, 186–194. Sanda, T., Lawton, L.N., Barrasa, M.I., Fan, Z.P., Kohlhammer, H., Gutierrez, A., Ma, W., Tatarek, J., Ahn, Y., Kelliher, M.A., et al. (2012). Cancer Cell 22, 209–221. Sugimoto, K., Itoh, T., Takita, M., Shimoda, M., Chujo, D., Sorelle, J.A., Naziruddin, B., Levy, M.F., Shimada, M., and Matsumoto, S. (2014). Transpl. Int. 27, 408–415. van Riel, B., Pakozdi, T., Brouwer, R., Monteiro, R., Tuladhar, K., Franke, V., Bryne, J.C., Jorna, R., Rijkers, E.J., van Ijcken, W., et al. (2012). Mol. Cell. Biol. 32, 3814–3822. Published online Jul 16, 2012. http://dx.doi.org/10.1128/MCB.05938-11. Wang, Z., Zang, C., Cui, K., Schones, D.E., Barski, A., Peng, W., and Zhao, K. (2009). Cell 138, 1019– 1031. Yoder, M.C., Mead, L.E., Prater, D., Krier, T.R., Mroueh, K.N., Li, F., Krasich, R., Temm, C.J., Prchal, J.T., and Ingram, D.A. (2007). Blood 109, 1801–1809.
Previews Targeting Epigenetics to Speed Up Repair Eric Soler1,* and Frank Grosveld2,* 1INSERM
UMR967 CEA/DSV/iRCM, 92265 Fontenay-aux-Roses, France of Cell Biology, Erasmus Medical Center, Rotterdam, The Netherlands *Correspondence: [email protected] (E.S.), [email protected] (F.G.) http://dx.doi.org/10.1016/j.stem.2014.04.018 2Department
In this issue of Cell Stem Cell, Palii et al. reveal that TAL1 is a master regulator of adhesion and migration networks in human endothelial progenitors and that ex vivo treatment with the histone deacetylase inhibitor TSA enables their faster vascularization after ischemic injury. Ischemia is a restriction of tissue blood precursor of endothelial and hemato- due to survival or proliferation defects of supply due to vessel dysfunction, leading poietic lineages during early embryo- the ECFCs but was caused by typical to a shortage of oxygen and tissue dam- genesis. In particular, TAL1 is required endothelial cell properties. They were age. When treating ischemia it is impera- for remodeling of the vasculature during unable to form capillary-like structures tive to restore blood flow quickly in order development, but its potential contribu- after plating on Matrigel and collagen to reestablish oxygen supply and reduce tion to the revascularization properties and showed impaired adhesion properorgan damage. Using endothelial progen- of injected ECFCs was unknown. Brand ties. Moreover, in a Boyden chamber itors to regenerate a defective vasculature and colleagues knocked down TAL1 assay, their migration was severely and increase the rate of vascular repair is expression in ECFCs derived from human reduced toward the chemokine SDF-1 a major goal of cell-based regenerative cord blood and showed their inability to due to reduced expression of the chemotherapies (Figure 1). Endothelial colony- engraft in ischemic muscles and improve kine receptor CXCR4. forming cells (ECFCs) (Yoder et al., 2007) blood flow recovery in a mouse model of Genome-wide mapping of TAL1 bindare particularly suitable for such therapy hindlimb ischemia. This lack of capacity ing sites in ECFCs by chromatin immunoand they can relatively easily be obtained to promote revascularization was not precipitation coupled to high-throughput from human cord blood sequencing (ChIP-Seq) reand peripheral blood. They vealed strong association of can differentiate into endoTAL1 with genes involved in thelial capillary-like structures blood vessel development in vitro, form new functionally and critical regulatory pathactive human blood vessels ways linked to vascular funcin vivo, and enhance revascutions such as PDGF and larization in mouse models of VEGF signaling pathways. ischemia (Pelosi et al., 2014, The analysis of genes funcBenslimane-Ahmim et al., tionally dependent on TAL1 2011). However, the molein ECFCs confirmed its cular mechanisms at play in involvement in the regulation these processes remained of endothelial cell migration largely uncharacterized. In and adhesion via the activathis issue of Cell Stem Cell, tion of multiple effector genes Palii et al. provide an in-depth directly impacting ECFC characterization of the critical functions. For example, the role played by the transcripendothelial-specific junction tion factor TAL1, or SCL, in molecule gene CHD5, the the vascular repair function cell-cell contact molecule of human ECFCs (Palii et al., Ephrin B2 ligand (EFNB2), 2014). and a number of transcription TAL1, a class II basic helixfactors essential for endoloop-helix transcription facthelial functions (e.g. SOX7 Figure 1. Enhanced Recovery from Ischemic Injury by ECFCs Pretreated with TSA tor, is a well-known regulator and HOXA9) are regulated Ischemic injury results in interrupted or lower blood supply to affected tissue. of human hematopoiesis, by TAL1. Interestingly, the Injection of ECFCs helps rescue the blood flow by generating new vasculature with recognized roles in regulatory sequences of at the site of injury. The transcription factor TAL1 is a key factor controlling this process in ECFCs. TAL1 positively regulates target genes by cooperating with T cell leukemia (Palii et al., these targets are already the histone acetyl transferase p300. This action is turned down by histone 2011, Sanda et al., 2012). bound by TAL1 very early in deacetylases (HDACs). Treatment with TSA, an HDAC inhibitor, modifies the TAL1 also plays a key role in development when the debalance between TAL1/p300 and HDACs and enhances TAL1 target gene the hemangioblast, a bipotent velopmental choice between expression in ECFCs, resulting in faster recovery after ischemic injury. Cell Stem Cell 14, May 1, 2014 ª2014 Elsevier Inc. 553
Cell Stem Cell
Previews cardiac, endothelial, and hematopoietic precursor cells still has to be made (Mylona et al., 2013). The mechanism of activation of endothelial genes by TAL1 was further analyzed, based on knowledge of its regulatory functions derived from erythroid cells. Similar to what was known from the erythroid lineage, the p300 histone acetyl transferase (HAT) was shown to co-occupy TAL1 chromatin binding sites in ECFCs and to be required for the expression of TAL1 target genes. Furthermore, p300 binding appears to be dependent on the presence of TAL1 because p300 is lost upon TAL1 knockdown, concomitant with a decrease in histone H3 acetylation and decreased transcriptional activity of target genes. Therefore TAL1 recruits p300 to activate its target genes in ECFCs. Gene regulatory mechanisms involve a balance of activators such as the p300 HATs and repressors such as histone deacetylases (HDACs) at regulatory sites (Wang et al., 2009). Brand and colleagues therefore sought to shift this balance toward activation by using the HDAC inhibitor TSA on ECFCs to increase TAL1-dependent gene transcription. They observe that histone H3 acetylation and the binding of p300 HAT were increased in ex vivo TSA-treated ECFCs, which appears to confirm that the balance of HAT/HDAC has been changed. Genes involved in ECFC migration are activated after TSA treatment, leading to increased migration kinetics in a TAL1-dependent manner. This effect was confirmed in vivo by transplanting ECFCs pretreated with TSA into ischemic mouse muscles, which resulted in a dramatic increase in the rate of blood flow recovery (4 days as compared with 10 days with non-TSA treated cells). Thus, ex vivo treatment with TSA improved the kinetics of ECFC-mediated vascular repair in vivo and was associated with increased arteriole density and
decreased necrosis. Because the speed of blood flow recovery is one of the most critical parameters in clinical settings, pretreatment of ECFCs with HDAC inhibitors could be a useful strategy to improve cell-based therapies. The use of epigenetic drugs ex vivo in clinical settings therefore appears promising and offers the advantage of providing a transient ‘‘functional boost’’ to therapeutic cells prior to injection to maximize their clinical potential. Although the authors do not show which HDACs are involved and where they bind, the observed effect is likely due to a displacement of the ratio between HATs and HDACs at TAL1 chromatin binding sites. Because they observe the presence of GATA sites, a number of good candidate HDACs may be the same as those known in the hematopoietic system (van Riel et al., 2012). A topic for future investigation is which, if any, of these (tissue-specific) cofactors mentioned above mediates or regulates TAL1 function in ECFCs. They may represent new leads to further manipulate the function of TAL1 complexes through additional candidate targets. Clearly, additional questions will have to be resolved before any clinical application can be considered. The most important one will be whether the ex vivo TSA priming and subsequent transplantation protocol would be sufficiently fast to result in therapeutic effects for the most common causes of ischemia. Second, it remains to be seen whether heterologous transplants may result in immunological reactions, requiring treatment with immunosuppressants. It is encouraging, however, that HDAC inhibitors may have the capacity to inhibit rejection by the immune system, at least in some heterologous transplant settings (Sugimoto et al., 2014). Nevertheless, it may be useful to store ECFCs to be able to provide an
554 Cell Stem Cell 14, May 1, 2014 ª2014 Elsevier Inc.
autologous transplant quickly when needed, especially if TSA-primed ECFCs would retain their efficiency after cryopreservation. Such a solution may be useful in a hospital setting for patients with ischemic conditions that develop slowly or for those known to be at high risk for developing ischemia. REFERENCES Benslimane-Ahmim, Z., Heymann, D., Dizier, B., Lokajczyk, A., Brion, R., Laurendeau, I., Bie`che, I., Smadja, D.M., Galy-Fauroux, I., ColliecJouault, S., et al. (2011). J. Thromb. Haemost. 9, 834–843. Mylona, A., Andrieu-Soler, C., Thongjuea, S., Martella, A., Soler, E., Jorna, R., Hou, J., Kockx, C., van Ijcken, W., Lenhard, B., and Grosveld, F. (2013). Blood 121, 2902–2913. Published online Feb 6, 2013. http://dx.doi.org/10.1182/blood2012-11-467654. Palii, C.G., Perez-Iratxeta, C., Yao, Z., Cao, Y., Dai, F., Davison, J., Atkins, H., Allan, D., Dilworth, F.J., Gentleman, R., et al. (2011). EMBO J. 30, 494–509. Palii, C., Ulesevic, B., Fraineu, S., Prackeviciene, E., Griffith, A., Chu, A., Faralli, H., Li, Y., McNeill, B., Sun, J., et al. (2014). Cell Stem Cell 14, this issue, 644–657. Pelosi, E., Castelli, G., and Testa, U. (2014). Blood Cells Mol. Dis. 52, 186–194. Sanda, T., Lawton, L.N., Barrasa, M.I., Fan, Z.P., Kohlhammer, H., Gutierrez, A., Ma, W., Tatarek, J., Ahn, Y., Kelliher, M.A., et al. (2012). Cancer Cell 22, 209–221. Sugimoto, K., Itoh, T., Takita, M., Shimoda, M., Chujo, D., Sorelle, J.A., Naziruddin, B., Levy, M.F., Shimada, M., and Matsumoto, S. (2014). Transpl. Int. 27, 408–415. van Riel, B., Pakozdi, T., Brouwer, R., Monteiro, R., Tuladhar, K., Franke, V., Bryne, J.C., Jorna, R., Rijkers, E.J., van Ijcken, W., et al. (2012). Mol. Cell. Biol. 32, 3814–3822. Published online Jul 16, 2012. http://dx.doi.org/10.1128/MCB.05938-11. Wang, Z., Zang, C., Cui, K., Schones, D.E., Barski, A., Peng, W., and Zhao, K. (2009). Cell 138, 1019– 1031. Yoder, M.C., Mead, L.E., Prater, D., Krier, T.R., Mroueh, K.N., Li, F., Krasich, R., Temm, C.J., Prchal, J.T., and Ingram, D.A. (2007). Blood 109, 1801–1809.