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Reorganization of corticospinal tract fibers after spinal cord injury in adult macaques.

Nakagawa H, Ninomiya T, Yamashita T, Takada M - Sci Rep (2015)

Bottom Line: When anterograde tract tracing with biotinylated dextran amine was performed to identify the intraspinal reinnervation of sprouting CST fibers, it was found that the laminar distribution of CST fibers was changed.Instead, few, if any, CST fibers were distributed in the dorsal laminae.The present results indicate that CST fibers below the lesion site after SCI in macaques are reorganized in conjunction with the recovery of dexterous manual movements.

View Article: PubMed Central - PubMed

Affiliation: 1] Systems Neuroscience Section, Primate Research Institute, Kyoto University, Inuyama, Aichi 484-8506, Japan [2] Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan.

ABSTRACT
Previous studies have shown that sprouting of corticospinal tract (CST) fibers after spinal cord injury (SCI) contributes to recovery of motor functions. However, the neuroanatomical mechanism underlying the functional recovery through sprouting CST fibers remains unclear. Here we investigated the pattern of reorganization of CST fibers below the lesion site after SCI in adult macaques. Unilateral lesions were made at the level between the C7 and the C8 segment. The extent of spontaneous recovery of manual dexterity was assessed with a reaching/grasping task. The impaired dexterous manual movements were gradually recovered after SCI. When anterograde tract tracing with biotinylated dextran amine was performed to identify the intraspinal reinnervation of sprouting CST fibers, it was found that the laminar distribution of CST fibers was changed. The sprouting CST fibers extended preferentially into lamia IX where the spinal motor neuron pool was located, to innervate the motor neurons directly. Instead, few, if any, CST fibers were distributed in the dorsal laminae. The present results indicate that CST fibers below the lesion site after SCI in macaques are reorganized in conjunction with the recovery of dexterous manual movements.

No MeSH data available.


Related in: MedlinePlus

Immunohistochemical analyses of the sites of BDA injections in the MI and the distribution of BDA-labeled CST fibers.(a) Sites of BDA injections in MI regions representing the forelimb, trunk, and hindlimb (denoted with stars). (b) Example of the injection site in the forelimb region. Scale bar: 1 mm. (c) Higher-power magnification of a rectangular area in b. Scale bar: 50 μm. (d,i,n) Representative transverse sections through the C6 (d) and C8 (i) segments in an SCI model (MoA) and the C8 segment (n) in a normal control (MoE). Scale bar: 1 mm. (f–h) Higher-power magnification of rectangular areas in e. (k–m) Higher-power magnification of rectangular areas in j. (p–r) Higher-power magnification of rectangular areas in o. f,k,p: Laterally-situated CST fibers. g,l,q: Laminae IV to VI. h,m,r: Lamina XI. Scale bar: 100 μm.
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f3: Immunohistochemical analyses of the sites of BDA injections in the MI and the distribution of BDA-labeled CST fibers.(a) Sites of BDA injections in MI regions representing the forelimb, trunk, and hindlimb (denoted with stars). (b) Example of the injection site in the forelimb region. Scale bar: 1 mm. (c) Higher-power magnification of a rectangular area in b. Scale bar: 50 μm. (d,i,n) Representative transverse sections through the C6 (d) and C8 (i) segments in an SCI model (MoA) and the C8 segment (n) in a normal control (MoE). Scale bar: 1 mm. (f–h) Higher-power magnification of rectangular areas in e. (k–m) Higher-power magnification of rectangular areas in j. (p–r) Higher-power magnification of rectangular areas in o. f,k,p: Laterally-situated CST fibers. g,l,q: Laminae IV to VI. h,m,r: Lamina XI. Scale bar: 100 μm.

Mentions: In our SCI model in which a border region between the C7 and the C8 segment was lesioned (Fig. 1a), part of the gray matter in the medial aspect was left intact to retain a route of sprouting CST fibers. The extent of spinal cord lesions in a transverse section was 61.1%, 55.5%, 71.3%, and 71.5% of the total area on the lesioned side in MoA–MoD, respectively (Fig. 1b,c). In each case, dorsolaterally-situated CST fibers were fully removed (Fig. 1b,c). The spinal cord lesions in MoB and MoC infringed, to some extent, upon the C7 segment per se. Results of anterograde tract tracing with biotinylated dextran amine (BDA) indicated that CST fibers travelling through the dorsolateral funiculus were not observed at all below the lesion site in any of the four monkeys (see Fig. 3k). Ventrally-situated CST fibers through other descending tracts appeared to be preserved in the three monkeys except MoD (Fig. 1c). The rubrospinal tract region was largely damaged in all cases, and the reticulospinal tract region was damaged partly in MoA–MoC and completely in MoD (Fig. 1b,c).


Reorganization of corticospinal tract fibers after spinal cord injury in adult macaques.

Nakagawa H, Ninomiya T, Yamashita T, Takada M - Sci Rep (2015)

Immunohistochemical analyses of the sites of BDA injections in the MI and the distribution of BDA-labeled CST fibers.(a) Sites of BDA injections in MI regions representing the forelimb, trunk, and hindlimb (denoted with stars). (b) Example of the injection site in the forelimb region. Scale bar: 1 mm. (c) Higher-power magnification of a rectangular area in b. Scale bar: 50 μm. (d,i,n) Representative transverse sections through the C6 (d) and C8 (i) segments in an SCI model (MoA) and the C8 segment (n) in a normal control (MoE). Scale bar: 1 mm. (f–h) Higher-power magnification of rectangular areas in e. (k–m) Higher-power magnification of rectangular areas in j. (p–r) Higher-power magnification of rectangular areas in o. f,k,p: Laterally-situated CST fibers. g,l,q: Laminae IV to VI. h,m,r: Lamina XI. Scale bar: 100 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4487234&req=5

f3: Immunohistochemical analyses of the sites of BDA injections in the MI and the distribution of BDA-labeled CST fibers.(a) Sites of BDA injections in MI regions representing the forelimb, trunk, and hindlimb (denoted with stars). (b) Example of the injection site in the forelimb region. Scale bar: 1 mm. (c) Higher-power magnification of a rectangular area in b. Scale bar: 50 μm. (d,i,n) Representative transverse sections through the C6 (d) and C8 (i) segments in an SCI model (MoA) and the C8 segment (n) in a normal control (MoE). Scale bar: 1 mm. (f–h) Higher-power magnification of rectangular areas in e. (k–m) Higher-power magnification of rectangular areas in j. (p–r) Higher-power magnification of rectangular areas in o. f,k,p: Laterally-situated CST fibers. g,l,q: Laminae IV to VI. h,m,r: Lamina XI. Scale bar: 100 μm.
Mentions: In our SCI model in which a border region between the C7 and the C8 segment was lesioned (Fig. 1a), part of the gray matter in the medial aspect was left intact to retain a route of sprouting CST fibers. The extent of spinal cord lesions in a transverse section was 61.1%, 55.5%, 71.3%, and 71.5% of the total area on the lesioned side in MoA–MoD, respectively (Fig. 1b,c). In each case, dorsolaterally-situated CST fibers were fully removed (Fig. 1b,c). The spinal cord lesions in MoB and MoC infringed, to some extent, upon the C7 segment per se. Results of anterograde tract tracing with biotinylated dextran amine (BDA) indicated that CST fibers travelling through the dorsolateral funiculus were not observed at all below the lesion site in any of the four monkeys (see Fig. 3k). Ventrally-situated CST fibers through other descending tracts appeared to be preserved in the three monkeys except MoD (Fig. 1c). The rubrospinal tract region was largely damaged in all cases, and the reticulospinal tract region was damaged partly in MoA–MoC and completely in MoD (Fig. 1b,c).

Bottom Line: When anterograde tract tracing with biotinylated dextran amine was performed to identify the intraspinal reinnervation of sprouting CST fibers, it was found that the laminar distribution of CST fibers was changed.Instead, few, if any, CST fibers were distributed in the dorsal laminae.The present results indicate that CST fibers below the lesion site after SCI in macaques are reorganized in conjunction with the recovery of dexterous manual movements.

View Article: PubMed Central - PubMed

Affiliation: 1] Systems Neuroscience Section, Primate Research Institute, Kyoto University, Inuyama, Aichi 484-8506, Japan [2] Department of Molecular Neuroscience, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan.

ABSTRACT
Previous studies have shown that sprouting of corticospinal tract (CST) fibers after spinal cord injury (SCI) contributes to recovery of motor functions. However, the neuroanatomical mechanism underlying the functional recovery through sprouting CST fibers remains unclear. Here we investigated the pattern of reorganization of CST fibers below the lesion site after SCI in adult macaques. Unilateral lesions were made at the level between the C7 and the C8 segment. The extent of spontaneous recovery of manual dexterity was assessed with a reaching/grasping task. The impaired dexterous manual movements were gradually recovered after SCI. When anterograde tract tracing with biotinylated dextran amine was performed to identify the intraspinal reinnervation of sprouting CST fibers, it was found that the laminar distribution of CST fibers was changed. The sprouting CST fibers extended preferentially into lamia IX where the spinal motor neuron pool was located, to innervate the motor neurons directly. Instead, few, if any, CST fibers were distributed in the dorsal laminae. The present results indicate that CST fibers below the lesion site after SCI in macaques are reorganized in conjunction with the recovery of dexterous manual movements.

No MeSH data available.


Related in: MedlinePlus