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Transplanted human bone marrow cells generate new brain cells
Journal of the Neurological Sciences 233 (2005) 121 – 123 www.elsevier.com/locate/jns
Transplanted human bone marrow cells generate new brain cells Barbara J. Craina,*, Simon D. Tranb, Eva Mezeyc a
b
Department of Pathology, The Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD, 21205, USA National Institute of Dental and Craniofacial Research, Gene Therapy and Therapeutics Branch, National Institutes of Health, Bethesda, MD, USA c National Institute of Neurological Disorders and Stroke, Basic Neuroscience Program, National Institutes of Health, Bethesda, MD, USA Available online 21 April 2005
Abstract Multiple studies have reported that adult cells of bone marrow origin can differentiate into muscle, skin, liver, lung, epithelial cells, and neurons. To determine whether such cells might produce neurons and other cells in the human brain, we examined paraffin sections from female patients who had received bone marrow transplants from male donors. Y-chromosomes were labeled using autoradiography and fluorescent in situ hybridization. Neurons and astrocytes were identified histologically and immunohistochemically in neocortex, hippocampus, striatum, and cerebellum. However, most labeled cells in both gray and white matter appeared to be glia. Others have suggested that such Y-labeling represents fusion between host and donor cells, rather than true transdifferentiation. The possibilities of fusion and microchimerism were therefore examined using buccal epithelial cells as a model system. The female patients in this study had received either bone marrow or stem cell (CD34+ enriched) transplants from their brothers. Double labeling for X- and Y-chromosomes showed that Y-labeled buccal cells could not be explained by fusion. Genotyping studies of one patient, her brother, and her son ruled out the possibility of microchimerism. Whether, and under what circumstances, some form of bone marrow transplantation might provide adequate number of cells capable of replacing lost brain cells or enhancing their function will require additional studies. D 2005 Elsevier B.V. All rights reserved. Keywords: Human; Bone marrow transplantation; Neurons; Glia; Buccal epithelium; Cell fusion; Transdifferentiation
Progenitor cells in the bone marrow primarily produce red blood cells, white blood cells, and platelets. However, in the last few years multiple studies in rodents have reported that adult cells of bone marrow origin can differentiate into muscle, skin, liver, lung, and neurons [1–10]. Similar studies in humans have reported that transplanted bone marrow cells may form cardiac myocytes, hepatocytes, and epithelial cells of skin and GI tract in humans [11–14]. We therefore wondered whether cells of bone marrow origin might be capable of producing neurons and other cells in the human brain. To address this question, we examined paraffin-embedded tissue from female patients who had received bone marrow transplants from male donors [15]. Four transplant patients were included in this study. Their ages at transplantation were 9 months, 10 years, 20 years, and 34 years; the infant survived for 10 months, while the others each survived for approx* Corresponding author. Fax: +1 410 955 9777. E-mail address: [email protected] (B.J. Crain). 0022-510X/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jns.2005.03.017
imately 2 months. Technically satisfactory results were obtained in three of the patients, including the youngest. Males and females without transplants served as positive and negative controls. This study was approved by the Joint Committee on Clinical Investigation at The Johns Hopkins University School of Medicine. Brain regions examined in each case included neocortex, striatum, hippocampus, and cerebellum. Sections were stained using either fluorescent in situ histochemistry (FISH) or a radiolabel to identify Ychromosomes [15]. FISH sections were counterstained with DAPI to label nuclei. Some FISH sections were also immunostained for neurons using either a nuclear marker, NeuN (ChemiCon), or a potassium channel antibody, Kv2.1 (Alomone, Jerusalem), which labels neuronal cytoplasm. Immunostaining for the astrocytic marker glial fibrillary acidic protein was also performed (GFAP). Sections were then examined by both conventional and confocal microscopy. As would be expected, white blood cells within blood vessels were readily labeled with the Y-chromosome
122
B.J. Crain et al. / Journal of the Neurological Sciences 233 (2005) 121 – 123
markers. Careful examination also showed cells with Ychromosomes in the brain parenchyma. Some of the Ylabeled cells in neocortex had the appearance of pyramidal cells, as evidenced by their nuclear size and chromatin pattern and their prominent apical dendrites oriented towards the pial surface. Immunohistochemistry for NeuN and Kv2.1 also confirmed the presence of Y-labeled neurons within hippocampus, neocortex, and striatum. Confocal microscopy confirmed that the Y-chromosomes were indeed localized within the nuclei of the NeuN- and Kv2.1-labeled cells [15]. To get an estimate of the number of labeled cells within the brain, the total number of DAPI-labeled nuclei and the total number of Y-labeled nuclei were counted in sections from two of the cases. In Case #1, 182,000 nuclei were counted, with 519 Y-labeled nuclei, including 19 neurons. In Case #3, 196,700 nuclei were counted, with 1842 Y-labeled nuclei and just 5 neurons. Overall, the numbers of labeled cells (including neurons) were about 10-fold lower than in rodent studies (2 –5/10 000 vs. 50/10 000) [2,7,15]. What were the nonneuronal parenchymal cells? Some Ychromosomes were identified within blood vessel walls, although DAPI nuclear staining alone could not determine whether the Y-labeling was over endothelial or smooth muscle nuclei. Most of the nonneuronal cells with Ychromosomes had the nuclear size and chromatin patterns of either oligodendroglia or astrocytes. Microglia were likely labeled as well, as they are the only glia of documented hematopoetic origin [16], although resting microglia cannot be identified by their nuclear characteristics. So far, the only immunohistochemistry for glia has been with an antibody to GFAP. This marker labeled few cells overall; a handful of these apparently had Y-labeling, but these cells have not been examined by confocal microscopy to confirm their double-labeling. Clearly these studies of astrocytes need to be expanded, and studies with antibodies against oligodendroglia and microglia performed, as more of these parenchymal cells must be identified. A striking feature of the Y-labeled brain sections was the nonrandom distribution of labeled cells, which often appeared in clusters [15]. The clusters contained both neuronal and nonneuronal cells. Whether such clusters represent division and subsequent divergent differentiation of individual precursor cells or whether they represent sites where multiple precursors entered through a break in the blood –brain barrier cannot be determined. The origin of Y-labeled cells in material such as ours is controversial. One obvious possibility is that these cells represent transdifferentiation of bone marrow stem cells, mesenchymal stem cells, or some other undefined cell type. However, there are at least two other theoretical possibilities: fusion of bone marrow cells with existing brain parenchymal cells [17 – 19] and microchimerism resulting from exchange of cells between the patient and a previous male fetus [20]. Rigorous experimental analysis of these possibilities is not possible when the cells of
interest are relatively few and scattered, and when the sections are as thin as the ones required for the above studies. We therefore turned to another model system to address these issues. The model chosen was the buccal epithelium. The buccal epithelium is a homogeneous population of squamous cells that forms the inner surface of the cheek. Scraping (swabbing) this surface is a noninvasive way of sampling this population in living subjects. Cells obtained in this fashion are viewed as a monolayer of non-overlapping cells. Furthermore, each cell is seen in its entirety, so its entire genome is available for analysis. Buccal swabs were obtained from five females, ages 31– 56 years, who had received either a bone marrow transplant or a CD34-enriched stem cell transplant from their HLAidentical brothers four to six years previously [21]. Normal males and females served as controls. This study was approved by the Institutional Review Board of the National Institute of Dental and Craniofacial Research (NIDCR), National Institutes of Health. As in the previous study, the Y-chromosome was visualized by autoradiography and by FISH. The mean number of Y-labeled cells was 5.8% (range 1.4– 11%), a relatively high percentage of Y-labeled cells that may reflect the normally rapid turnover rate of this cell population. The cells had the morphology of normal squamous cells and were immunolabeled for cytokeratin 16, an intermediate filament found in squamous epithelial cells and absent from cryopreserved donor bone marrow. Their function was normal, as evidenced by the fact that the subjects’ buccal mucosa was intact and without infections or other lesions. Four criteria have been proposed to show plasticity of adult stem cells [22,23]. The first criteria that cells be clonal was not met here, as marrow-derived cells other than CD34+ cells might have been transplanted. However, the other three criteria were all met: the transplanted cells were isolated and transplanted without in vitro culturing; the phenotype of the transdifferentiated cells was shown anatomically, molecularly, and functionally; and the frequency of transdifferentiation was determined. We also examined the possibilities of fusion [17 – 19] and microchimerism [20] directly. To evaluate the possibility of fusion between bone marrow cells and buccal cells, some preparations were simultaneously labeled with FISH probes for both X- and Y-chromosomes. Over 9700 cells were examined in five patients. Virtually all were either XX or XY. The only exceptions were a single XXY cell and a single XXXY cell (21). Thus, fusion could not explain the presence of Y-chromosomes in this cell population. The possibility of microchimerism associated with a previous pregnancy could also be eliminated. Genotyping was performed on DNA extracted from buccal cells of a female patient with a bone marrow transplant and on DNA extracted from peripheral blood samples taken from her donor brother and from her son [21]. Four Y-chromosomal markers were examined (289, 388, 390, and 391). The
B.J. Crain et al. / Journal of the Neurological Sciences 233 (2005) 121 – 123
patient’s buccal cells and her brother’s blood had the same genotypes. However, the patient_s son had different alleles for two of the markers, indicating that the patient’s Ychromosome-positive cells could not have arisen as a result of microchimerism. In contrast to the above results in buccal cells, studies of Y-labeled hepatocytes in mice missing the enzyme fumarylacetoacetate hydrolase (Fah) indicate that the latter develop as a result of fusion [17]. It is possible that the results in liver may be related in some way to the fact that hepatocytes are frequently polyploid and therefore not generalizable to all cell types. It should also be noted that the ‘‘fused’’ hepatocytes were functional and able to express Fah [17]. Whether the Y-labeled brain cells identified in our studies can eventually be manipulated for clinical purposes remains to be determined. The number of labeled cells documented in the present study is low, so that the presence of Y-labeled neurons in our patients must be considered as ‘‘proof of principle’’ rather than as documentation of widespread supplementation of host cells. Whether, and under what circumstances, such transplantation might provide adequate number of cells capable of replacing lost host cells or enhancing their function will require additional studies.
References [1] Bittner RE, Schofer C, Weipoltshammer K, Ivanova S, Streubel B, Hauser E, et al. Recruitment of bone-marrow-derived cells by skeletal and cardiac muscle in adult dystrophic mdx mice. Anat Embryol (Berl) 1999;199(5):391 – 6. [2] Brazelton TR, Rossi FM, Keshet GI, Blau HM. From marrow to brain: expression of neuronal phenotypes in adult mice. Science 2000; 290(5497):1775 – 9. [3] Eglitis MA, Mezey E. Hematopoietic cells differentiate into both microglia and macroglia in the brains of adult mice. Proc Natl Acad Sci U S A 1997;94(8):4080 – 5. [4] Ferrari G, Cusella-De Angelis G, Coletta M, Paolucci E, Stornaiuolo A, Cossu G, et al. Muscle regeneration by bone marrow-derived myogenic progenitors. Science 1998;279(5356):1528 – 30. [5] Gussoni E, Soneoka Y, Strickland CD, Buzney EA, Khan MK, Flint AF, et al. Dystrophin expression in the mdx mouse restored by stem cell transplantation. Nature 1999;401(6751):390 – 4.
123
[6] Mahmood A, Lu D, Yi L, Chen JL, Chopp M. Intracranial bone marrow transplantation after traumatic brain injury improving functional outcome in adult rats. J Neurosurg 2001;94(4):589 – 95. [7] Mezey E, Chandross KJ, Harta G, Maki RA, McKercher SR. Turning blood into brain: cells bearing neuronal antigens generated in vivo from bone marrow. Science 2000;290(5497):1779 – 82. [8] Orlic D, Kajstura J, Chimenti S, Jakoniuk I, Anderson SM, Li B, et al. Bone marrow cells regenerate infarcted myocardium. Nature 2001; 410(6829):701 – 5. [9] Theise ND, Badve S, Saxena R, Henegariu O, Sell S, Crawford JM, et al. Derivation of hepatocytes from bone marrow cells in mice after radiation-induced myeloablation. Hepatology 2000;31(1):235 – 40. [10] Theise ND, Nimmakayalu M, Gardner R, Illei PB, Morgan G, Teperman L, et al. Liver from bone marrow in humans. Hepatology 2000;32(1):11 – 6. [11] Quaini F, Urbanek K, Beltrami AP, Finato N, Beltrami CA, NadalGinard B, et al. Chimerism of the transplanted heart. N Engl J Med 2002;346(1):5 – 15. [12] Korbling M, Katz RL, Khanna A, Ruifrok AC, Rondon G, Albitar M, et al. Hepatocytes and epithelial cells of donor origin in recipients of peripheral-blood stem cells. N Engl J Med 2002;346(10):738 – 46. [13] Lagasse E, Connors H, Al-Dhalimy M, Reitsma M, Dohse M, Osborne L, et al. Purified hematopoietic stem cells can differentiate into hepatocytes in vivo. Nat Med 2000;6(11):1229 – 34. [14] Alison MR, Poulsom R, Jeffery R, Dhillon AP, Quaglia A, Jacob J, et al. Hepatocytes from non-hepatic adult stem cells. Nature 2000; 406(6793):257. [15] Mezey E, Key S, Vogelsang G, Szalayova I, Lange GD, Crain B. Transplanted bone marrow generates new neurons in human brains. Proc Natl Acad Sci U S A 2003;100(3):1364 – 9. [16] Hickey WF, Kimura H. Perivascular microglial cells of the CNS are bone marrow-derived and present antigen in vivo. Science 1988; 239(4837):290 – 2. [17] Vassilopoulos G, Wang PR, Russell DW. Transplanted bone marrow regenerates liver by cell fusion. Nature 2003;422(6934):901 – 4. [18] Ying QL, Nichols J, Evans EP, Smith AG. Changing potency by spontaneous fusion. Nature 2002;416(6880):545 – 8. [19] Terada N, Hamazaki T, Oka M, Hoki M, Mastalerz DM, Nakano Y, et al. Bone marrow cells adopt the phenotype of other cells by spontaneous cell fusion. Nature 2002;416(6880):542 – 5. [20] Nelson JL. Microchimerism: incidental byproduct of pregnancy or active participant in human health? Trends Mol Med 2002;8(3): 109 – 13. [21] Tran SD, Pillemer SR, Dutra A, Barrett AJ, Brownstein MJ, Key S, et al. Differentiation of human bone marrow-derived cells into buccal epithelial cells in vivo: a molecular analytical study. Lancet 2003; 361(9363):1084 – 8. [22] Anderson DJ, Gage FH, Weissman IL. Can stem cells cross lineage boundaries? Nat Med 2001;7(4):393 – 5. [23] Wells WA. Is transdifferentiation in trouble? J Cell Biol 2002;157(1): 15 – 8.
Transplanted human bone marrow cells generate new brain cells Barbara J. Craina,*, Simon D. Tranb, Eva Mezeyc a
b
Department of Pathology, The Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD, 21205, USA National Institute of Dental and Craniofacial Research, Gene Therapy and Therapeutics Branch, National Institutes of Health, Bethesda, MD, USA c National Institute of Neurological Disorders and Stroke, Basic Neuroscience Program, National Institutes of Health, Bethesda, MD, USA Available online 21 April 2005
Abstract Multiple studies have reported that adult cells of bone marrow origin can differentiate into muscle, skin, liver, lung, epithelial cells, and neurons. To determine whether such cells might produce neurons and other cells in the human brain, we examined paraffin sections from female patients who had received bone marrow transplants from male donors. Y-chromosomes were labeled using autoradiography and fluorescent in situ hybridization. Neurons and astrocytes were identified histologically and immunohistochemically in neocortex, hippocampus, striatum, and cerebellum. However, most labeled cells in both gray and white matter appeared to be glia. Others have suggested that such Y-labeling represents fusion between host and donor cells, rather than true transdifferentiation. The possibilities of fusion and microchimerism were therefore examined using buccal epithelial cells as a model system. The female patients in this study had received either bone marrow or stem cell (CD34+ enriched) transplants from their brothers. Double labeling for X- and Y-chromosomes showed that Y-labeled buccal cells could not be explained by fusion. Genotyping studies of one patient, her brother, and her son ruled out the possibility of microchimerism. Whether, and under what circumstances, some form of bone marrow transplantation might provide adequate number of cells capable of replacing lost brain cells or enhancing their function will require additional studies. D 2005 Elsevier B.V. All rights reserved. Keywords: Human; Bone marrow transplantation; Neurons; Glia; Buccal epithelium; Cell fusion; Transdifferentiation
Progenitor cells in the bone marrow primarily produce red blood cells, white blood cells, and platelets. However, in the last few years multiple studies in rodents have reported that adult cells of bone marrow origin can differentiate into muscle, skin, liver, lung, and neurons [1–10]. Similar studies in humans have reported that transplanted bone marrow cells may form cardiac myocytes, hepatocytes, and epithelial cells of skin and GI tract in humans [11–14]. We therefore wondered whether cells of bone marrow origin might be capable of producing neurons and other cells in the human brain. To address this question, we examined paraffin-embedded tissue from female patients who had received bone marrow transplants from male donors [15]. Four transplant patients were included in this study. Their ages at transplantation were 9 months, 10 years, 20 years, and 34 years; the infant survived for 10 months, while the others each survived for approx* Corresponding author. Fax: +1 410 955 9777. E-mail address: [email protected] (B.J. Crain). 0022-510X/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jns.2005.03.017
imately 2 months. Technically satisfactory results were obtained in three of the patients, including the youngest. Males and females without transplants served as positive and negative controls. This study was approved by the Joint Committee on Clinical Investigation at The Johns Hopkins University School of Medicine. Brain regions examined in each case included neocortex, striatum, hippocampus, and cerebellum. Sections were stained using either fluorescent in situ histochemistry (FISH) or a radiolabel to identify Ychromosomes [15]. FISH sections were counterstained with DAPI to label nuclei. Some FISH sections were also immunostained for neurons using either a nuclear marker, NeuN (ChemiCon), or a potassium channel antibody, Kv2.1 (Alomone, Jerusalem), which labels neuronal cytoplasm. Immunostaining for the astrocytic marker glial fibrillary acidic protein was also performed (GFAP). Sections were then examined by both conventional and confocal microscopy. As would be expected, white blood cells within blood vessels were readily labeled with the Y-chromosome
122
B.J. Crain et al. / Journal of the Neurological Sciences 233 (2005) 121 – 123
markers. Careful examination also showed cells with Ychromosomes in the brain parenchyma. Some of the Ylabeled cells in neocortex had the appearance of pyramidal cells, as evidenced by their nuclear size and chromatin pattern and their prominent apical dendrites oriented towards the pial surface. Immunohistochemistry for NeuN and Kv2.1 also confirmed the presence of Y-labeled neurons within hippocampus, neocortex, and striatum. Confocal microscopy confirmed that the Y-chromosomes were indeed localized within the nuclei of the NeuN- and Kv2.1-labeled cells [15]. To get an estimate of the number of labeled cells within the brain, the total number of DAPI-labeled nuclei and the total number of Y-labeled nuclei were counted in sections from two of the cases. In Case #1, 182,000 nuclei were counted, with 519 Y-labeled nuclei, including 19 neurons. In Case #3, 196,700 nuclei were counted, with 1842 Y-labeled nuclei and just 5 neurons. Overall, the numbers of labeled cells (including neurons) were about 10-fold lower than in rodent studies (2 –5/10 000 vs. 50/10 000) [2,7,15]. What were the nonneuronal parenchymal cells? Some Ychromosomes were identified within blood vessel walls, although DAPI nuclear staining alone could not determine whether the Y-labeling was over endothelial or smooth muscle nuclei. Most of the nonneuronal cells with Ychromosomes had the nuclear size and chromatin patterns of either oligodendroglia or astrocytes. Microglia were likely labeled as well, as they are the only glia of documented hematopoetic origin [16], although resting microglia cannot be identified by their nuclear characteristics. So far, the only immunohistochemistry for glia has been with an antibody to GFAP. This marker labeled few cells overall; a handful of these apparently had Y-labeling, but these cells have not been examined by confocal microscopy to confirm their double-labeling. Clearly these studies of astrocytes need to be expanded, and studies with antibodies against oligodendroglia and microglia performed, as more of these parenchymal cells must be identified. A striking feature of the Y-labeled brain sections was the nonrandom distribution of labeled cells, which often appeared in clusters [15]. The clusters contained both neuronal and nonneuronal cells. Whether such clusters represent division and subsequent divergent differentiation of individual precursor cells or whether they represent sites where multiple precursors entered through a break in the blood –brain barrier cannot be determined. The origin of Y-labeled cells in material such as ours is controversial. One obvious possibility is that these cells represent transdifferentiation of bone marrow stem cells, mesenchymal stem cells, or some other undefined cell type. However, there are at least two other theoretical possibilities: fusion of bone marrow cells with existing brain parenchymal cells [17 – 19] and microchimerism resulting from exchange of cells between the patient and a previous male fetus [20]. Rigorous experimental analysis of these possibilities is not possible when the cells of
interest are relatively few and scattered, and when the sections are as thin as the ones required for the above studies. We therefore turned to another model system to address these issues. The model chosen was the buccal epithelium. The buccal epithelium is a homogeneous population of squamous cells that forms the inner surface of the cheek. Scraping (swabbing) this surface is a noninvasive way of sampling this population in living subjects. Cells obtained in this fashion are viewed as a monolayer of non-overlapping cells. Furthermore, each cell is seen in its entirety, so its entire genome is available for analysis. Buccal swabs were obtained from five females, ages 31– 56 years, who had received either a bone marrow transplant or a CD34-enriched stem cell transplant from their HLAidentical brothers four to six years previously [21]. Normal males and females served as controls. This study was approved by the Institutional Review Board of the National Institute of Dental and Craniofacial Research (NIDCR), National Institutes of Health. As in the previous study, the Y-chromosome was visualized by autoradiography and by FISH. The mean number of Y-labeled cells was 5.8% (range 1.4– 11%), a relatively high percentage of Y-labeled cells that may reflect the normally rapid turnover rate of this cell population. The cells had the morphology of normal squamous cells and were immunolabeled for cytokeratin 16, an intermediate filament found in squamous epithelial cells and absent from cryopreserved donor bone marrow. Their function was normal, as evidenced by the fact that the subjects’ buccal mucosa was intact and without infections or other lesions. Four criteria have been proposed to show plasticity of adult stem cells [22,23]. The first criteria that cells be clonal was not met here, as marrow-derived cells other than CD34+ cells might have been transplanted. However, the other three criteria were all met: the transplanted cells were isolated and transplanted without in vitro culturing; the phenotype of the transdifferentiated cells was shown anatomically, molecularly, and functionally; and the frequency of transdifferentiation was determined. We also examined the possibilities of fusion [17 – 19] and microchimerism [20] directly. To evaluate the possibility of fusion between bone marrow cells and buccal cells, some preparations were simultaneously labeled with FISH probes for both X- and Y-chromosomes. Over 9700 cells were examined in five patients. Virtually all were either XX or XY. The only exceptions were a single XXY cell and a single XXXY cell (21). Thus, fusion could not explain the presence of Y-chromosomes in this cell population. The possibility of microchimerism associated with a previous pregnancy could also be eliminated. Genotyping was performed on DNA extracted from buccal cells of a female patient with a bone marrow transplant and on DNA extracted from peripheral blood samples taken from her donor brother and from her son [21]. Four Y-chromosomal markers were examined (289, 388, 390, and 391). The
B.J. Crain et al. / Journal of the Neurological Sciences 233 (2005) 121 – 123
patient’s buccal cells and her brother’s blood had the same genotypes. However, the patient_s son had different alleles for two of the markers, indicating that the patient’s Ychromosome-positive cells could not have arisen as a result of microchimerism. In contrast to the above results in buccal cells, studies of Y-labeled hepatocytes in mice missing the enzyme fumarylacetoacetate hydrolase (Fah) indicate that the latter develop as a result of fusion [17]. It is possible that the results in liver may be related in some way to the fact that hepatocytes are frequently polyploid and therefore not generalizable to all cell types. It should also be noted that the ‘‘fused’’ hepatocytes were functional and able to express Fah [17]. Whether the Y-labeled brain cells identified in our studies can eventually be manipulated for clinical purposes remains to be determined. The number of labeled cells documented in the present study is low, so that the presence of Y-labeled neurons in our patients must be considered as ‘‘proof of principle’’ rather than as documentation of widespread supplementation of host cells. Whether, and under what circumstances, such transplantation might provide adequate number of cells capable of replacing lost host cells or enhancing their function will require additional studies.
References [1] Bittner RE, Schofer C, Weipoltshammer K, Ivanova S, Streubel B, Hauser E, et al. Recruitment of bone-marrow-derived cells by skeletal and cardiac muscle in adult dystrophic mdx mice. Anat Embryol (Berl) 1999;199(5):391 – 6. [2] Brazelton TR, Rossi FM, Keshet GI, Blau HM. From marrow to brain: expression of neuronal phenotypes in adult mice. Science 2000; 290(5497):1775 – 9. [3] Eglitis MA, Mezey E. Hematopoietic cells differentiate into both microglia and macroglia in the brains of adult mice. Proc Natl Acad Sci U S A 1997;94(8):4080 – 5. [4] Ferrari G, Cusella-De Angelis G, Coletta M, Paolucci E, Stornaiuolo A, Cossu G, et al. Muscle regeneration by bone marrow-derived myogenic progenitors. Science 1998;279(5356):1528 – 30. [5] Gussoni E, Soneoka Y, Strickland CD, Buzney EA, Khan MK, Flint AF, et al. Dystrophin expression in the mdx mouse restored by stem cell transplantation. Nature 1999;401(6751):390 – 4.
123
[6] Mahmood A, Lu D, Yi L, Chen JL, Chopp M. Intracranial bone marrow transplantation after traumatic brain injury improving functional outcome in adult rats. J Neurosurg 2001;94(4):589 – 95. [7] Mezey E, Chandross KJ, Harta G, Maki RA, McKercher SR. Turning blood into brain: cells bearing neuronal antigens generated in vivo from bone marrow. Science 2000;290(5497):1779 – 82. [8] Orlic D, Kajstura J, Chimenti S, Jakoniuk I, Anderson SM, Li B, et al. Bone marrow cells regenerate infarcted myocardium. Nature 2001; 410(6829):701 – 5. [9] Theise ND, Badve S, Saxena R, Henegariu O, Sell S, Crawford JM, et al. Derivation of hepatocytes from bone marrow cells in mice after radiation-induced myeloablation. Hepatology 2000;31(1):235 – 40. [10] Theise ND, Nimmakayalu M, Gardner R, Illei PB, Morgan G, Teperman L, et al. Liver from bone marrow in humans. Hepatology 2000;32(1):11 – 6. [11] Quaini F, Urbanek K, Beltrami AP, Finato N, Beltrami CA, NadalGinard B, et al. Chimerism of the transplanted heart. N Engl J Med 2002;346(1):5 – 15. [12] Korbling M, Katz RL, Khanna A, Ruifrok AC, Rondon G, Albitar M, et al. Hepatocytes and epithelial cells of donor origin in recipients of peripheral-blood stem cells. N Engl J Med 2002;346(10):738 – 46. [13] Lagasse E, Connors H, Al-Dhalimy M, Reitsma M, Dohse M, Osborne L, et al. Purified hematopoietic stem cells can differentiate into hepatocytes in vivo. Nat Med 2000;6(11):1229 – 34. [14] Alison MR, Poulsom R, Jeffery R, Dhillon AP, Quaglia A, Jacob J, et al. Hepatocytes from non-hepatic adult stem cells. Nature 2000; 406(6793):257. [15] Mezey E, Key S, Vogelsang G, Szalayova I, Lange GD, Crain B. Transplanted bone marrow generates new neurons in human brains. Proc Natl Acad Sci U S A 2003;100(3):1364 – 9. [16] Hickey WF, Kimura H. Perivascular microglial cells of the CNS are bone marrow-derived and present antigen in vivo. Science 1988; 239(4837):290 – 2. [17] Vassilopoulos G, Wang PR, Russell DW. Transplanted bone marrow regenerates liver by cell fusion. Nature 2003;422(6934):901 – 4. [18] Ying QL, Nichols J, Evans EP, Smith AG. Changing potency by spontaneous fusion. Nature 2002;416(6880):545 – 8. [19] Terada N, Hamazaki T, Oka M, Hoki M, Mastalerz DM, Nakano Y, et al. Bone marrow cells adopt the phenotype of other cells by spontaneous cell fusion. Nature 2002;416(6880):542 – 5. [20] Nelson JL. Microchimerism: incidental byproduct of pregnancy or active participant in human health? Trends Mol Med 2002;8(3): 109 – 13. [21] Tran SD, Pillemer SR, Dutra A, Barrett AJ, Brownstein MJ, Key S, et al. Differentiation of human bone marrow-derived cells into buccal epithelial cells in vivo: a molecular analytical study. Lancet 2003; 361(9363):1084 – 8. [22] Anderson DJ, Gage FH, Weissman IL. Can stem cells cross lineage boundaries? Nat Med 2001;7(4):393 – 5. [23] Wells WA. Is transdifferentiation in trouble? J Cell Biol 2002;157(1): 15 – 8.