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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.

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.

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Endogenous sensory axon regeneration across GDA-transplanted dorsal column injuries at 8 days after lesion and transplantation. (a) A montaged, low-magnification confocal image scanned from a single 25-μm thick sagittal section, showing BDA-labeled ascending dorsal column axons (green) that have entered, grown within and exited a hPAP+ (red) GDA-transplanted dorsal column lesion. LC, lesion center. (b) A high-magnification image of a rostral graft/host interface showing BDA+ axons exiting the GDA graft and entering host white matter. A few axons were observed to have turned away from the interface and grown back towards the lesion center (arrowhead). (c) In control lesions, the vast majority of BDA+ axons have formed dystrophic endings and failed to leave the caudal margins of the lesion, marked by hypertrophic GFAP+ astrocytes (red). (d) A high-magnification image showing numerous BDA+ axons that have successfully crossed the host/graft interface at the caudal lesion margin. A few cut axons (arrowheads) have, however, failed to leave the caudal lesion interface and can be seen to have turned and/or formed dystrophic endings, particularly in regions containing few hPAP+ GDAs (red). (e) BDA+ axons located near the pial surface and ventral regions of cuneate white matter at 1.5 mm rostral to a GDA-bridged lesion site. (f) BDA+ axon growth cones in white matter 1.5 mm rostral to the lesion site often display streamlined growth cones indicative of rapid growth. Scale bars: (a,c) 100 μm; (b-e) 50 μm; (f) 5 μm (top) and 10 μm (bottom).
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Figure 3: Endogenous sensory axon regeneration across GDA-transplanted dorsal column injuries at 8 days after lesion and transplantation. (a) A montaged, low-magnification confocal image scanned from a single 25-μm thick sagittal section, showing BDA-labeled ascending dorsal column axons (green) that have entered, grown within and exited a hPAP+ (red) GDA-transplanted dorsal column lesion. LC, lesion center. (b) A high-magnification image of a rostral graft/host interface showing BDA+ axons exiting the GDA graft and entering host white matter. A few axons were observed to have turned away from the interface and grown back towards the lesion center (arrowhead). (c) In control lesions, the vast majority of BDA+ axons have formed dystrophic endings and failed to leave the caudal margins of the lesion, marked by hypertrophic GFAP+ astrocytes (red). (d) A high-magnification image showing numerous BDA+ axons that have successfully crossed the host/graft interface at the caudal lesion margin. A few cut axons (arrowheads) have, however, failed to leave the caudal lesion interface and can be seen to have turned and/or formed dystrophic endings, particularly in regions containing few hPAP+ GDAs (red). (e) BDA+ axons located near the pial surface and ventral regions of cuneate white matter at 1.5 mm rostral to a GDA-bridged lesion site. (f) BDA+ axon growth cones in white matter 1.5 mm rostral to the lesion site often display streamlined growth cones indicative of rapid growth. Scale bars: (a,c) 100 μm; (b-e) 50 μm; (f) 5 μm (top) and 10 μm (bottom).

Mentions: Transplantation of GDAs into stab-wound lesions of the dorsal column white matter pathways of adult rat spinal cord (Figure 1a–c) resulted in the growth of the majority of the cut ascending dorsal column axons into the lesion center (Figures 2 and 3a), with 66% of these axons extending further beyond the lesion site into adjacent white matter (Figures 2 and 3a,b,e,f). In order to minimize labeling of spared axons, a discrete population of ascending axons aligned with the lesion site was traced en passage with a single biotinylated dextran amine (BDA) injection caudal to GDA-transplanted or control stab injuries of the right-hand dorsal column cuneate and gracile white matter pathways (Figure 1c; see the Glossary box for an explanation of terms). Previous studies have shown that about 30–40% of ascending dorsal column axons projecting to the dorsal column nuclei arise from postsynaptic dorsal column neurons in spinal laminar 4 and that 25% of ascending dorsal column axons are also propriospinal in origin [43,44]. Indeed, it is thought that only 15% of primary afferents of dorsal root ganglion (DRG) neurons entering the spinal cord at lumbar levels reach the cervical spinal cord and that most leave dorsal column white matter within two to three segments of entering [45]. Therefore our en passage labeling of dorsal column axons at the cervical level included significant proportions of axons from both DRG neurons and CNS spinal neurons.


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)

Endogenous sensory axon regeneration across GDA-transplanted dorsal column injuries at 8 days after lesion and transplantation. (a) A montaged, low-magnification confocal image scanned from a single 25-μm thick sagittal section, showing BDA-labeled ascending dorsal column axons (green) that have entered, grown within and exited a hPAP+ (red) GDA-transplanted dorsal column lesion. LC, lesion center. (b) A high-magnification image of a rostral graft/host interface showing BDA+ axons exiting the GDA graft and entering host white matter. A few axons were observed to have turned away from the interface and grown back towards the lesion center (arrowhead). (c) In control lesions, the vast majority of BDA+ axons have formed dystrophic endings and failed to leave the caudal margins of the lesion, marked by hypertrophic GFAP+ astrocytes (red). (d) A high-magnification image showing numerous BDA+ axons that have successfully crossed the host/graft interface at the caudal lesion margin. A few cut axons (arrowheads) have, however, failed to leave the caudal lesion interface and can be seen to have turned and/or formed dystrophic endings, particularly in regions containing few hPAP+ GDAs (red). (e) BDA+ axons located near the pial surface and ventral regions of cuneate white matter at 1.5 mm rostral to a GDA-bridged lesion site. (f) BDA+ axon growth cones in white matter 1.5 mm rostral to the lesion site often display streamlined growth cones indicative of rapid growth. Scale bars: (a,c) 100 μm; (b-e) 50 μm; (f) 5 μm (top) and 10 μm (bottom).
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Figure 3: Endogenous sensory axon regeneration across GDA-transplanted dorsal column injuries at 8 days after lesion and transplantation. (a) A montaged, low-magnification confocal image scanned from a single 25-μm thick sagittal section, showing BDA-labeled ascending dorsal column axons (green) that have entered, grown within and exited a hPAP+ (red) GDA-transplanted dorsal column lesion. LC, lesion center. (b) A high-magnification image of a rostral graft/host interface showing BDA+ axons exiting the GDA graft and entering host white matter. A few axons were observed to have turned away from the interface and grown back towards the lesion center (arrowhead). (c) In control lesions, the vast majority of BDA+ axons have formed dystrophic endings and failed to leave the caudal margins of the lesion, marked by hypertrophic GFAP+ astrocytes (red). (d) A high-magnification image showing numerous BDA+ axons that have successfully crossed the host/graft interface at the caudal lesion margin. A few cut axons (arrowheads) have, however, failed to leave the caudal lesion interface and can be seen to have turned and/or formed dystrophic endings, particularly in regions containing few hPAP+ GDAs (red). (e) BDA+ axons located near the pial surface and ventral regions of cuneate white matter at 1.5 mm rostral to a GDA-bridged lesion site. (f) BDA+ axon growth cones in white matter 1.5 mm rostral to the lesion site often display streamlined growth cones indicative of rapid growth. Scale bars: (a,c) 100 μm; (b-e) 50 μm; (f) 5 μm (top) and 10 μm (bottom).
Mentions: Transplantation of GDAs into stab-wound lesions of the dorsal column white matter pathways of adult rat spinal cord (Figure 1a–c) resulted in the growth of the majority of the cut ascending dorsal column axons into the lesion center (Figures 2 and 3a), with 66% of these axons extending further beyond the lesion site into adjacent white matter (Figures 2 and 3a,b,e,f). In order to minimize labeling of spared axons, a discrete population of ascending axons aligned with the lesion site was traced en passage with a single biotinylated dextran amine (BDA) injection caudal to GDA-transplanted or control stab injuries of the right-hand dorsal column cuneate and gracile white matter pathways (Figure 1c; see the Glossary box for an explanation of terms). Previous studies have shown that about 30–40% of ascending dorsal column axons projecting to the dorsal column nuclei arise from postsynaptic dorsal column neurons in spinal laminar 4 and that 25% of ascending dorsal column axons are also propriospinal in origin [43,44]. Indeed, it is thought that only 15% of primary afferents of dorsal root ganglion (DRG) neurons entering the spinal cord at lumbar levels reach the cervical spinal cord and that most leave dorsal column white matter within two to three segments of entering [45]. Therefore our en passage labeling of dorsal column axons at the cervical level included significant proportions of axons from both DRG neurons and CNS spinal neurons.

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