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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

Patterns of laminar distribution of anterogradely-labeled CST fibers in an SCI model (MoA) and a normal control (MoE).(a) Distribution of CST fibers in the C6 segment above the lesion site (intact control) in MoA. (b,c) Distributions of CST fibers in the C8 (b) and T1 (c) segments below the lesion site in MoA (upper row) and MoE (lower row). In each segment, the laminar parcellation is depicted in a representative transverse section. (d) Histograms showing the ratio of BDA-labeled axons in each lamina to the total in the C8 and T1 segments in the SCI group and normal control. (e) Histograms showing the ratio of BDA-labeled axons in the C6, C8 and T1 segments in the SCI group. Error bars denote SEM, n = 3. Dunnet test, *P < 0.05.
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f4: Patterns of laminar distribution of anterogradely-labeled CST fibers in an SCI model (MoA) and a normal control (MoE).(a) Distribution of CST fibers in the C6 segment above the lesion site (intact control) in MoA. (b,c) Distributions of CST fibers in the C8 (b) and T1 (c) segments below the lesion site in MoA (upper row) and MoE (lower row). In each segment, the laminar parcellation is depicted in a representative transverse section. (d) Histograms showing the ratio of BDA-labeled axons in each lamina to the total in the C8 and T1 segments in the SCI group and normal control. (e) Histograms showing the ratio of BDA-labeled axons in the C6, C8 and T1 segments in the SCI group. Error bars denote SEM, n = 3. Dunnet test, *P < 0.05.

Mentions: To investigate the distribution pattern of sprouting CST fibers after SCI at the level between the C7 and the C8 segments, data obtained from anterograde tract tracing of CST fibers and terminal button-like swellings were analyzed in the C8 and T1 segments (below the lesion site), in comparison with the intact C6 segment and the normal C8 and T1 segments. In these control cases, anterogradely-labeled CST fibers after BDA injections into the contralateral primary motor cortex (MI; Fig. 3a–c) were distributed extensively over dorsal laminae, though they were located primarily in lamina VII and then in lamina IX (Figs 3d–h,n–r and 4a–e). A much smaller number of BDA-labeled CST fibers were found in both of the C8 and T1 segments in the SCI group than in the control cases (C6: C8, P = 0.038; C6: T1, P = 0.04; Figs 3d–r and 4a–e). Consistent with the distribution in the control cases, about half of the labeled CST fibers in these segments were distributed in lamina VII. In remarkable contrast with the control cases, the ratio of CST fiber labels in lamina IX after SCI went up to 36.5 ± 4.5 (C8) and 36.0 ± 0.2 (T1) of the total (C6, 21.4 ± 0.9). However, those in dorsal laminae were largely reduced to a few percent of the total (C6: C8, P = 0.028; C6: T1, P = 0.032; Fig. 4a–e). The values for laminae I–VI in the C6, C8, and T1 segments were 15.6 ± 1.1, 4.1 ± 0.4 and 5.0 ± 0.6, respectively.


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

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

Patterns of laminar distribution of anterogradely-labeled CST fibers in an SCI model (MoA) and a normal control (MoE).(a) Distribution of CST fibers in the C6 segment above the lesion site (intact control) in MoA. (b,c) Distributions of CST fibers in the C8 (b) and T1 (c) segments below the lesion site in MoA (upper row) and MoE (lower row). In each segment, the laminar parcellation is depicted in a representative transverse section. (d) Histograms showing the ratio of BDA-labeled axons in each lamina to the total in the C8 and T1 segments in the SCI group and normal control. (e) Histograms showing the ratio of BDA-labeled axons in the C6, C8 and T1 segments in the SCI group. Error bars denote SEM, n = 3. Dunnet test, *P < 0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Patterns of laminar distribution of anterogradely-labeled CST fibers in an SCI model (MoA) and a normal control (MoE).(a) Distribution of CST fibers in the C6 segment above the lesion site (intact control) in MoA. (b,c) Distributions of CST fibers in the C8 (b) and T1 (c) segments below the lesion site in MoA (upper row) and MoE (lower row). In each segment, the laminar parcellation is depicted in a representative transverse section. (d) Histograms showing the ratio of BDA-labeled axons in each lamina to the total in the C8 and T1 segments in the SCI group and normal control. (e) Histograms showing the ratio of BDA-labeled axons in the C6, C8 and T1 segments in the SCI group. Error bars denote SEM, n = 3. Dunnet test, *P < 0.05.
Mentions: To investigate the distribution pattern of sprouting CST fibers after SCI at the level between the C7 and the C8 segments, data obtained from anterograde tract tracing of CST fibers and terminal button-like swellings were analyzed in the C8 and T1 segments (below the lesion site), in comparison with the intact C6 segment and the normal C8 and T1 segments. In these control cases, anterogradely-labeled CST fibers after BDA injections into the contralateral primary motor cortex (MI; Fig. 3a–c) were distributed extensively over dorsal laminae, though they were located primarily in lamina VII and then in lamina IX (Figs 3d–h,n–r and 4a–e). A much smaller number of BDA-labeled CST fibers were found in both of the C8 and T1 segments in the SCI group than in the control cases (C6: C8, P = 0.038; C6: T1, P = 0.04; Figs 3d–r and 4a–e). Consistent with the distribution in the control cases, about half of the labeled CST fibers in these segments were distributed in lamina VII. In remarkable contrast with the control cases, the ratio of CST fiber labels in lamina IX after SCI went up to 36.5 ± 4.5 (C8) and 36.0 ± 0.2 (T1) of the total (C6, 21.4 ± 0.9). However, those in dorsal laminae were largely reduced to a few percent of the total (C6: C8, P = 0.028; C6: T1, P = 0.032; Fig. 4a–e). The values for laminae I–VI in the C6, C8, and T1 segments were 15.6 ± 1.1, 4.1 ± 0.4 and 5.0 ± 0.6, respectively.

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