Effects of FABP7 on functional recovery after spinal cord injury in adult mice

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OBJECTIVE

Elucidating the mechanisms of neuronal injury is crucial for the development of spinal cord injury (SCI) treatments. Brain-type fatty acid–binding protein 7 (FABP7) is expressed in the adult rodent brain, especially in astrocytes, and has been reported to play a role in astrocyte function in various types of brain damage; however, its role after SCI has not been well studied. In this study, the authors evaluated the expression change of FABP7 after SCI using a mouse spinal cord compression model and observed the effect of FABP7 gene knockout on neuronal damage and functional recovery after SCI.

METHODS

Female FABP7 knockout (KO) mice with a C57BL/6 background and their respective wild-type littermates were subjected to SCI with a vascular clip. The expression of FABP7, neuronal injury, and functional recovery after SCI were analyzed in both groups of mice.

RESULTS

Western blot analysis revealed upregulation of FABP7 in the wild-type mice, which reached its peak 14 days after SCI, with a significant difference in comparison to the control mice. Immunohistochemistry also showed upregulation of FABP7 at the same time points, mainly in proliferative astrocytes. The number of surviving ventral neurons in the FABP7-KO mice at 28 days after SCI was significantly lower than that observed in the wild-type mice. In addition, motor functional recovery in the FABP7-KO mice was significantly worse than that of the wild-type mice.

CONCLUSIONS

The findings of this study indicate that FABP7 could have a neuroprotective role that might be associated with modulation of astrocytes after SCI. FABP7 could potentially be a therapeutic target in the treatment of SCI.

ABBREVIATIONS BMS = Basso Mouse Scale; FABP = fatty acid–binding protein; GFAP = glial fibrillary acidic protein; KO = knockout; NeuN = neuronal nuclei; PUFA = polyunsaturated fatty acid; SCI = spinal cord injury.

Article Information

Correspondence Hiroyuki Kinouchi: Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo, Yamanashi, Japan. hkinouchi@yamanashi.ac.jp.

INCLUDE WHEN CITING Published online May 3, 2019; DOI: 10.3171/2019.2.SPINE18844.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Effects of FABP7-KO on neuronal survival 28 days after SCI. A and B: Representative photomicrographs showing unilateral ventral horn neurons in the wild-type control mice (A) and the FABP7-KO control mice (B). C and D: Representative photomicrographs showing loss of unilateral ventral horn neurons in the wild-type mice (C) and the FABP7-KO mice (D) 28 days after SCI. Sections were stained with NeuN 1000 µm caudal to the lesion center. The number of bilateral ventral horn neurons was calculated in the rectangular frame (dashed box; 250 × 340 µm). Asterisk shows the central canal. Scale bar = 50 µm. E: Quantification of ventral horn neuronal survival at different levels from the lesion center. Neuronal survival in the FABP7-KO mice was significantly less than that seen in the wild-type mice. Four mice were tested in each group. *p < 0.05 (wild-type vs FABP7-KO). Error bars indicate SEM. C1000 = 1000 µm caudal to the lesion center; C2000 = 2000 µm caudal to the lesion center; R1000 = 1000 µm rostral to the lesion center; R2000 = 2000 µm rostral to the lesion center. Figure is available in color online only.

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    Effects of FABP7-KO on astrogliosis. A and B: Representative photomicrographs showing GFAP staining in wild-type mice (A) and FABP7-KO mice (B) at 1000 µm caudal to the lesion center. The area of GFAP immunoreactivity was calculated in the rectangular frame (dashed box; 500 × 700 µm). C: There were no significant differences in GFAP immunoreactivity between the FABP7-KO and the wild-type mice at any distance point from the lesion center. The values are shown in proportion to the area of the rectangle. Error bars indicate SEM. Figure is available in color online only.

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    Expression of FABP7 in SCI. A: Western blot analysis of the spinal cord after injury in wild-type mice. β-actin was used as an internal control. B: Quantification of Western blot analysis showing a significant increase in FABP7 expression on day 14 after SCI. Four mice were tested per time point. Error bars indicate SEM. *p < 0.05 (vs control). d = day.

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    Expression of FABP7 in the gray matter around the ventral horn of the spinal cord. A–F: Double immunofluorescence labeling of the control (A–C) and injured (D–F) spinal cords at 1000 µm caudal to the center of the lesion for GFAP and FABP7 14 days after injury. Note that expression of FABP7 (green) in reactive astrocytes (red) was remarkably increased along with the enhancement of GFAP after injury. Scale bars = 50 µm. G: Quantification of FABP7 expression seen in a 250 × 340–µm rectangular portion of the bilateral ventral horns showing a significant increase on day 14 after SCI. Four mice were tested in each group. Error bars indicate SEM. *p < 0.05 (vs control). Figure is available in color online only.

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    Time course of locomotor recovery after SCI. Locomotor recovery was assessed using the BMS. The wild-type mice show significant improvement in locomotor performance compared with the FABP7-KO mice. Ten mice were tested in each group. *p < 0.05. Error bars indicate SEM.

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