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Astrocytes derived from glial-restricted precursors promote spinal cord repair.

Davies JE, Huang C, Proschel C, Noble M, Mayer-Proschel M, Davies SJ - J. Biol. (2006)

Bottom Line: We reasoned therefore that pre-differentiation of embryonic neural precursors to astrocytes, which are thought to support axon growth in the injured immature CNS, would be more beneficial for CNS repair.In sharp contrast, undifferentiated GRPs failed to suppress scar formation or support axon growth and locomotor recovery.Pre-differentiation of glial precursors into GDAs before transplantation into spinal cord injuries leads to significantly improved outcomes over precursor cell transplantation, providing both a novel strategy and a highly effective new cell type for repairing CNS injuries.

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Affiliation: Department of Neurosurgery, Baylor College of Medicine, 1709 Dryden Street, Suite 750, Houston, Texas 77030, USA. jdavies@bcm.edu

ABSTRACT

Background: Transplantation of embryonic stem or neural progenitor cells is an attractive strategy for repair of the injured central nervous system. Transplantation of these cells alone to acute spinal cord injuries has not, however, resulted in robust axon regeneration beyond the sites of injury. This may be due to progenitors differentiating to cell types that support axon growth poorly and/or their inability to modify the inhibitory environment of adult central nervous system (CNS) injuries. We reasoned therefore that pre-differentiation of embryonic neural precursors to astrocytes, which are thought to support axon growth in the injured immature CNS, would be more beneficial for CNS repair.

Results: Transplantation of astrocytes derived from embryonic glial-restricted precursors (GRPs) promoted robust axon growth and restoration of locomotor function after acute transection injuries of the adult rat spinal cord. Transplantation of GRP-derived astrocytes (GDAs) into dorsal column injuries promoted growth of over 60% of ascending dorsal column axons into the centers of the lesions, with 66% of these axons extending beyond the injury sites. Grid-walk analysis of GDA-transplanted rats with rubrospinal tract injuries revealed significant improvements in locomotor function. GDA transplantation also induced a striking realignment of injured tissue, suppressed initial scarring and rescued axotomized CNS neurons with cut axons from atrophy. In sharp contrast, undifferentiated GRPs failed to suppress scar formation or support axon growth and locomotor recovery.

Conclusion: Pre-differentiation of glial precursors into GDAs before transplantation into spinal cord injuries leads to significantly improved outcomes over precursor cell transplantation, providing both a novel strategy and a highly effective new cell type for repairing CNS injuries.

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GDA transplantation suppresses neurocan and NG2 immunoreactivity. (a) At 4 days after injury, control lesion margins display dense neurocan immunoreactivity (green) mainly associated with fine, GFAP- processes and to a lesser extent with GFAP+ astrocyte cell bodies (red). (b) Neurocan immunoreactivity at 4 days after injury and transplantation is greatly reduced in margins of hPAP+ GDA-transplanted lesions. (c) At 8 days after injury and GDA transplantation, neurocan immunoreactivity within lesion margins has increased compared with the 4-day time point. Note, however, that intra-lesion hPAP+ GDAs continue not to be immunoreactive to neurocan. (d-f) GDA-transplanted lesion centers (e,f) at 4 days after injury show a marked reduction in NG2 immunoreactivity (red) compared with (d) control lesions. hPAP+ cells are stained green. (g-i) Although overall NG2 immunoreactivity has increased within the center of GDA-transplanted lesions (h,i) at 8 days after injury compared with (e,f) the 4-day time point, it is reduced compared with the more uniformly distributed NG2 immunoreactivity within the center of control lesions at 8 days after injury. Scale bars: (a,b,g) 100 μm; (c,h,i) 50 μm; (d-f) 200 μm.
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Figure 7: GDA transplantation suppresses neurocan and NG2 immunoreactivity. (a) At 4 days after injury, control lesion margins display dense neurocan immunoreactivity (green) mainly associated with fine, GFAP- processes and to a lesser extent with GFAP+ astrocyte cell bodies (red). (b) Neurocan immunoreactivity at 4 days after injury and transplantation is greatly reduced in margins of hPAP+ GDA-transplanted lesions. (c) At 8 days after injury and GDA transplantation, neurocan immunoreactivity within lesion margins has increased compared with the 4-day time point. Note, however, that intra-lesion hPAP+ GDAs continue not to be immunoreactive to neurocan. (d-f) GDA-transplanted lesion centers (e,f) at 4 days after injury show a marked reduction in NG2 immunoreactivity (red) compared with (d) control lesions. hPAP+ cells are stained green. (g-i) Although overall NG2 immunoreactivity has increased within the center of GDA-transplanted lesions (h,i) at 8 days after injury compared with (e,f) the 4-day time point, it is reduced compared with the more uniformly distributed NG2 immunoreactivity within the center of control lesions at 8 days after injury. Scale bars: (a,b,g) 100 μm; (c,h,i) 50 μm; (d-f) 200 μm.

Mentions: In both dorsal column axon regeneration experiments, the linearity of axonal growth we observed, particularly within lesion margins (Figures 3c,d and 5a), prompted us to examine the underlying tissue organization. Transplantation of dissociated GDAs was associated not only with a significant reduction in astrogliosis but also with a striking reorganization of host astrocyte cell bodies and processes within lesion margins (Figures 5a and 6b,d and Additional data file 1). To examine host astrocytes, we took advantage of an unexpected downregulation of GFAP in the transplanted GDAs at 4 and 8 days after transplantation (Figure 6b) to identify host astrocytes with anti-GFAP immunostaining. Intra-lesion GDAs did, however, remain positive for the astrocyte lineage markers S100 and vimentin (Additional data file 2) and did not express the oligodendrocyte lineage antigens NG2 (Figure 7e,h) or proteolipid protein (data not shown). GFAP+ host astrocytes within the margins of control medium-injected lesions (Figures 3c, 6a,c and Additional data file 3), and in animals receiving GRP cell transplants (Figure 5b,c) exhibited the characteristic hypertrophic cell bodies of adult reactive astrocytes and formed a dense mass of numerous, ramified, misaligned processes typical of astrogliotic scar tissue. In contrast, in animals receiving GDA transplants, host GFAP+ astrocyte processes within lesion margins were now oriented toward lesion centers (Figures 5a and 6b,d and Additional data file 1).


Astrocytes derived from glial-restricted precursors promote spinal cord repair.

Davies JE, Huang C, Proschel C, Noble M, Mayer-Proschel M, Davies SJ - J. Biol. (2006)

GDA transplantation suppresses neurocan and NG2 immunoreactivity. (a) At 4 days after injury, control lesion margins display dense neurocan immunoreactivity (green) mainly associated with fine, GFAP- processes and to a lesser extent with GFAP+ astrocyte cell bodies (red). (b) Neurocan immunoreactivity at 4 days after injury and transplantation is greatly reduced in margins of hPAP+ GDA-transplanted lesions. (c) At 8 days after injury and GDA transplantation, neurocan immunoreactivity within lesion margins has increased compared with the 4-day time point. Note, however, that intra-lesion hPAP+ GDAs continue not to be immunoreactive to neurocan. (d-f) GDA-transplanted lesion centers (e,f) at 4 days after injury show a marked reduction in NG2 immunoreactivity (red) compared with (d) control lesions. hPAP+ cells are stained green. (g-i) Although overall NG2 immunoreactivity has increased within the center of GDA-transplanted lesions (h,i) at 8 days after injury compared with (e,f) the 4-day time point, it is reduced compared with the more uniformly distributed NG2 immunoreactivity within the center of control lesions at 8 days after injury. Scale bars: (a,b,g) 100 μm; (c,h,i) 50 μm; (d-f) 200 μm.
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Figure 7: GDA transplantation suppresses neurocan and NG2 immunoreactivity. (a) At 4 days after injury, control lesion margins display dense neurocan immunoreactivity (green) mainly associated with fine, GFAP- processes and to a lesser extent with GFAP+ astrocyte cell bodies (red). (b) Neurocan immunoreactivity at 4 days after injury and transplantation is greatly reduced in margins of hPAP+ GDA-transplanted lesions. (c) At 8 days after injury and GDA transplantation, neurocan immunoreactivity within lesion margins has increased compared with the 4-day time point. Note, however, that intra-lesion hPAP+ GDAs continue not to be immunoreactive to neurocan. (d-f) GDA-transplanted lesion centers (e,f) at 4 days after injury show a marked reduction in NG2 immunoreactivity (red) compared with (d) control lesions. hPAP+ cells are stained green. (g-i) Although overall NG2 immunoreactivity has increased within the center of GDA-transplanted lesions (h,i) at 8 days after injury compared with (e,f) the 4-day time point, it is reduced compared with the more uniformly distributed NG2 immunoreactivity within the center of control lesions at 8 days after injury. Scale bars: (a,b,g) 100 μm; (c,h,i) 50 μm; (d-f) 200 μm.
Mentions: In both dorsal column axon regeneration experiments, the linearity of axonal growth we observed, particularly within lesion margins (Figures 3c,d and 5a), prompted us to examine the underlying tissue organization. Transplantation of dissociated GDAs was associated not only with a significant reduction in astrogliosis but also with a striking reorganization of host astrocyte cell bodies and processes within lesion margins (Figures 5a and 6b,d and Additional data file 1). To examine host astrocytes, we took advantage of an unexpected downregulation of GFAP in the transplanted GDAs at 4 and 8 days after transplantation (Figure 6b) to identify host astrocytes with anti-GFAP immunostaining. Intra-lesion GDAs did, however, remain positive for the astrocyte lineage markers S100 and vimentin (Additional data file 2) and did not express the oligodendrocyte lineage antigens NG2 (Figure 7e,h) or proteolipid protein (data not shown). GFAP+ host astrocytes within the margins of control medium-injected lesions (Figures 3c, 6a,c and Additional data file 3), and in animals receiving GRP cell transplants (Figure 5b,c) exhibited the characteristic hypertrophic cell bodies of adult reactive astrocytes and formed a dense mass of numerous, ramified, misaligned processes typical of astrogliotic scar tissue. In contrast, in animals receiving GDA transplants, host GFAP+ astrocyte processes within lesion margins were now oriented toward lesion centers (Figures 5a and 6b,d and Additional data file 1).

Bottom Line: We reasoned therefore that pre-differentiation of embryonic neural precursors to astrocytes, which are thought to support axon growth in the injured immature CNS, would be more beneficial for CNS repair.In sharp contrast, undifferentiated GRPs failed to suppress scar formation or support axon growth and locomotor recovery.Pre-differentiation of glial precursors into GDAs before transplantation into spinal cord injuries leads to significantly improved outcomes over precursor cell transplantation, providing both a novel strategy and a highly effective new cell type for repairing CNS injuries.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neurosurgery, Baylor College of Medicine, 1709 Dryden Street, Suite 750, Houston, Texas 77030, USA. jdavies@bcm.edu

ABSTRACT

Background: Transplantation of embryonic stem or neural progenitor cells is an attractive strategy for repair of the injured central nervous system. Transplantation of these cells alone to acute spinal cord injuries has not, however, resulted in robust axon regeneration beyond the sites of injury. This may be due to progenitors differentiating to cell types that support axon growth poorly and/or their inability to modify the inhibitory environment of adult central nervous system (CNS) injuries. We reasoned therefore that pre-differentiation of embryonic neural precursors to astrocytes, which are thought to support axon growth in the injured immature CNS, would be more beneficial for CNS repair.

Results: Transplantation of astrocytes derived from embryonic glial-restricted precursors (GRPs) promoted robust axon growth and restoration of locomotor function after acute transection injuries of the adult rat spinal cord. Transplantation of GRP-derived astrocytes (GDAs) into dorsal column injuries promoted growth of over 60% of ascending dorsal column axons into the centers of the lesions, with 66% of these axons extending beyond the injury sites. Grid-walk analysis of GDA-transplanted rats with rubrospinal tract injuries revealed significant improvements in locomotor function. GDA transplantation also induced a striking realignment of injured tissue, suppressed initial scarring and rescued axotomized CNS neurons with cut axons from atrophy. In sharp contrast, undifferentiated GRPs failed to suppress scar formation or support axon growth and locomotor recovery.

Conclusion: Pre-differentiation of glial precursors into GDAs before transplantation into spinal cord injuries leads to significantly improved outcomes over precursor cell transplantation, providing both a novel strategy and a highly effective new cell type for repairing CNS injuries.

Show MeSH
Related in: MedlinePlus