Involvement of Shh/Gli1 signaling in the permeability of blood-spinal cord barrier and locomotion recovery after spinal cord contusion

Shh/Gli1 signaling plays important roles in development of spinal cord. How it is involved in spinal cord injury (SCI) remains unclear. In this study, we explored the roles of Shh/Gli1 signaling in SCI by using Shh signaling reporter Gli1(lz) mice and Gli1 mutant Gli1(lz/lz) mice. For detecting the Shh/Gli1 signaling after SCI, X-gal staining and double-immunostaining of Shh/PDGFR-beta, Shh/GFAP and LacZ/GFAP was conducted at 3 days post injury (dpi) on Gli1(lz) mice. To investigate the effects of Gil1 mutation on pathological changes after SCI, astrocytic proliferation and the content of intra-parenchymal Evans Blue were evaluated at 7dpi in wild-type and Gli1(lz/lz )mice. Furthermore, locomotor recovery was assessed by BMS scoring at 1, 3, 5 and 7dpi. The results of X-gal staining and immunohistochemistry showed that Shh/Gli1 signaling was mainly activated in reactive astrocytes after SCI. The 5-bromo-2-deoxyuridine (BrdU) incorporation assay showed that mutation of Gil1 did not affect the proliferation of astrocytes. However, the leakage of Evans Blue was significantly increased in the injured cord of Gli1(lz/lz )mice compared to wild-type mice. In addition, locomotor recovery was significantly impaired in the Gli1(lz/lz) mice. The findings demonstrated that Shh/Gli1 signaling could be induced in reactive astrocytes by SCI, and plays important role in permeability of blood-spinal cord barrier (BSCB) and locomotor recovery after SCI.