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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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Transplanted GDAs promote regeneration of rubrospinal axons. (a) Confocal montage scanned through a depth of 60 μm, showing a small population of BDA+ rubrospinal tract (RST) axons (green) that have traversed a GDA-bridged (red) lesion of the dorsolateral funiculus and entered caudal white matter at 8 days after injury. The majority of RST axons, however, have sprouted to within 300 μm of the lesion center (LC) but failed to extend beyond the site of injury. Note the absence of BDA-labeled axons within the dorsal-most regions of the injury site. (b) Confocal montage showing the complete failure of axotomized BDA+ RST axons to cross control lesions at 8 days after injury and that the majority of axons have remained within rostral lesion margins at a distance of 500–800 μm from the lesion center (LC). (c) At 5 weeks after injury and transplantation, a small population of BDA+ RST axons have traversed GDA-bridged injury sites and extended within caudal white matter. Note that BDA+ axons have also sprouted into the dorsal regions of the lesion center and even extended beyond the pial surface (arrowhead; see also the high-power image in (d)). Note the lower levels of GFAP immunoreactivity (red) in more ventral regions of the injury margins and center, coincident with the presence of BDA+ axons. (e) Two examples of RST axons displaying growth cones within white matter 2 mm caudal to a GDA-treated lesion, at 5 weeks after transplantation. Note the collateral branch (asterisk). (f) Confocal image of a BDA+ terminal field-like axonal plexus within layer 5 spinal cord gray matter, immediately adjacent to the dorsolateral funiculus white matter at 5 weeks after injury and transplantation. In contrast, in all GDA-transplanted rats and controls injected with medium alone at 8 days after injury, no BDA labeling was observed within gray matter beyond the injury site. Scale bars: (a-c) 200 μm; (d) 100 μm; (e) 5 μm; (f) 10 μm.
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Figure 8: Transplanted GDAs promote regeneration of rubrospinal axons. (a) Confocal montage scanned through a depth of 60 μm, showing a small population of BDA+ rubrospinal tract (RST) axons (green) that have traversed a GDA-bridged (red) lesion of the dorsolateral funiculus and entered caudal white matter at 8 days after injury. The majority of RST axons, however, have sprouted to within 300 μm of the lesion center (LC) but failed to extend beyond the site of injury. Note the absence of BDA-labeled axons within the dorsal-most regions of the injury site. (b) Confocal montage showing the complete failure of axotomized BDA+ RST axons to cross control lesions at 8 days after injury and that the majority of axons have remained within rostral lesion margins at a distance of 500–800 μm from the lesion center (LC). (c) At 5 weeks after injury and transplantation, a small population of BDA+ RST axons have traversed GDA-bridged injury sites and extended within caudal white matter. Note that BDA+ axons have also sprouted into the dorsal regions of the lesion center and even extended beyond the pial surface (arrowhead; see also the high-power image in (d)). Note the lower levels of GFAP immunoreactivity (red) in more ventral regions of the injury margins and center, coincident with the presence of BDA+ axons. (e) Two examples of RST axons displaying growth cones within white matter 2 mm caudal to a GDA-treated lesion, at 5 weeks after transplantation. Note the collateral branch (asterisk). (f) Confocal image of a BDA+ terminal field-like axonal plexus within layer 5 spinal cord gray matter, immediately adjacent to the dorsolateral funiculus white matter at 5 weeks after injury and transplantation. In contrast, in all GDA-transplanted rats and controls injected with medium alone at 8 days after injury, no BDA labeling was observed within gray matter beyond the injury site. Scale bars: (a-c) 200 μm; (d) 100 μm; (e) 5 μm; (f) 10 μm.

Mentions: GDA transplantation was also beneficial for CNS neurons, as demonstrated by analysis of rubrospinal tract (RST) axons within injuries to the right-side dorsolateral funiculus of the spinal cord and their corresponding neuronal cell bodies within the left-side red nucleus of the brain (Figure 1d). Severe injury to this descending, somatic motor control pathway disrupts the ability of rats to step rhythmically and coordinate accurate fore- and hind-limb placement. In animals in which the dorsolateral funiculus was transected, GDAs again filled the site of injury, integrated into host tissue and realigned host astrocytes. In animals receiving no GDAs, there was a complete absence of RST axons within the lesion centers (Figure 8b). The majority of BDA+ axons in control injury sites had dystrophic endings and remained between 500 and 800 μm from lesion centers (Figure 8b). In sharp contrast, in four out of six animals receiving GDA transplants, BDA-labeled RST axons were readily observable within lesion centers (Figure 8a) and also within caudal white matter up to 1.5 mm beyond the site of injury. In addition, the majority of axotomized RST axons within GDA-transplanted animals were observed interacting with GDAs in rostral lesion margins and had sprouted to within 300 μm of lesion centers (Figure 8a). Those axons that had grown into caudal white matter in GDA-bridged injuries were invariably observed in the ventral half of the injury sites, which correlated with regions of GDA transplants that more often continuously spanned the injury site (Figure 8a). In the two out of six GDA-recipient animals in which GDA grafts did not span sites of injury (see also Figure 4b), no BDA axons were observed within white matter beyond the site of injury (data not shown).


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)

Transplanted GDAs promote regeneration of rubrospinal axons. (a) Confocal montage scanned through a depth of 60 μm, showing a small population of BDA+ rubrospinal tract (RST) axons (green) that have traversed a GDA-bridged (red) lesion of the dorsolateral funiculus and entered caudal white matter at 8 days after injury. The majority of RST axons, however, have sprouted to within 300 μm of the lesion center (LC) but failed to extend beyond the site of injury. Note the absence of BDA-labeled axons within the dorsal-most regions of the injury site. (b) Confocal montage showing the complete failure of axotomized BDA+ RST axons to cross control lesions at 8 days after injury and that the majority of axons have remained within rostral lesion margins at a distance of 500–800 μm from the lesion center (LC). (c) At 5 weeks after injury and transplantation, a small population of BDA+ RST axons have traversed GDA-bridged injury sites and extended within caudal white matter. Note that BDA+ axons have also sprouted into the dorsal regions of the lesion center and even extended beyond the pial surface (arrowhead; see also the high-power image in (d)). Note the lower levels of GFAP immunoreactivity (red) in more ventral regions of the injury margins and center, coincident with the presence of BDA+ axons. (e) Two examples of RST axons displaying growth cones within white matter 2 mm caudal to a GDA-treated lesion, at 5 weeks after transplantation. Note the collateral branch (asterisk). (f) Confocal image of a BDA+ terminal field-like axonal plexus within layer 5 spinal cord gray matter, immediately adjacent to the dorsolateral funiculus white matter at 5 weeks after injury and transplantation. In contrast, in all GDA-transplanted rats and controls injected with medium alone at 8 days after injury, no BDA labeling was observed within gray matter beyond the injury site. Scale bars: (a-c) 200 μm; (d) 100 μm; (e) 5 μm; (f) 10 μm.
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Figure 8: Transplanted GDAs promote regeneration of rubrospinal axons. (a) Confocal montage scanned through a depth of 60 μm, showing a small population of BDA+ rubrospinal tract (RST) axons (green) that have traversed a GDA-bridged (red) lesion of the dorsolateral funiculus and entered caudal white matter at 8 days after injury. The majority of RST axons, however, have sprouted to within 300 μm of the lesion center (LC) but failed to extend beyond the site of injury. Note the absence of BDA-labeled axons within the dorsal-most regions of the injury site. (b) Confocal montage showing the complete failure of axotomized BDA+ RST axons to cross control lesions at 8 days after injury and that the majority of axons have remained within rostral lesion margins at a distance of 500–800 μm from the lesion center (LC). (c) At 5 weeks after injury and transplantation, a small population of BDA+ RST axons have traversed GDA-bridged injury sites and extended within caudal white matter. Note that BDA+ axons have also sprouted into the dorsal regions of the lesion center and even extended beyond the pial surface (arrowhead; see also the high-power image in (d)). Note the lower levels of GFAP immunoreactivity (red) in more ventral regions of the injury margins and center, coincident with the presence of BDA+ axons. (e) Two examples of RST axons displaying growth cones within white matter 2 mm caudal to a GDA-treated lesion, at 5 weeks after transplantation. Note the collateral branch (asterisk). (f) Confocal image of a BDA+ terminal field-like axonal plexus within layer 5 spinal cord gray matter, immediately adjacent to the dorsolateral funiculus white matter at 5 weeks after injury and transplantation. In contrast, in all GDA-transplanted rats and controls injected with medium alone at 8 days after injury, no BDA labeling was observed within gray matter beyond the injury site. Scale bars: (a-c) 200 μm; (d) 100 μm; (e) 5 μm; (f) 10 μm.
Mentions: GDA transplantation was also beneficial for CNS neurons, as demonstrated by analysis of rubrospinal tract (RST) axons within injuries to the right-side dorsolateral funiculus of the spinal cord and their corresponding neuronal cell bodies within the left-side red nucleus of the brain (Figure 1d). Severe injury to this descending, somatic motor control pathway disrupts the ability of rats to step rhythmically and coordinate accurate fore- and hind-limb placement. In animals in which the dorsolateral funiculus was transected, GDAs again filled the site of injury, integrated into host tissue and realigned host astrocytes. In animals receiving no GDAs, there was a complete absence of RST axons within the lesion centers (Figure 8b). The majority of BDA+ axons in control injury sites had dystrophic endings and remained between 500 and 800 μm from lesion centers (Figure 8b). In sharp contrast, in four out of six animals receiving GDA transplants, BDA-labeled RST axons were readily observable within lesion centers (Figure 8a) and also within caudal white matter up to 1.5 mm beyond the site of injury. In addition, the majority of axotomized RST axons within GDA-transplanted animals were observed interacting with GDAs in rostral lesion margins and had sprouted to within 300 μm of lesion centers (Figure 8a). Those axons that had grown into caudal white matter in GDA-bridged injuries were invariably observed in the ventral half of the injury sites, which correlated with regions of GDA transplants that more often continuously spanned the injury site (Figure 8a). In the two out of six GDA-recipient animals in which GDA grafts did not span sites of injury (see also Figure 4b), no BDA axons were observed within white matter beyond the site of injury (data not shown).

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