Study On The Effect And Mechanism Of FTY720 In Attenuating Fibrotic Scar Formation After Spinal Cord Injury

Purpose:This study aimed to investigate the whether FTY720 reduces fibrotic scarring by inhibiting IFN-γafter spinal cord injury(SCI).Methods:A spinal cord crush injury C57BL/6J mouse was established.Western blot was used to detect the IFN-γexpression level before SCI and at 3,7,14,28 day post injury(dpi)after SCI.In situ injection of Human serum albumin(HSA)and IFN-γin the normal spinal cord was used to explore the effects of IFN-γin PDGFRβ~+fibrotic scarring and CD68~+inflammation response.FTY720 is a sphingosine-1-phosphate receptor(S1PR)modulator,W146 is a S1PR antagonist.FTY720 or W146 was injected intraperitoneally daily after the SCI was used to reduce T cell-derived IFN-γ.In situ injection of IFN-γand HSA immediately followed by treatment with FTY720(Saline+HSA group,FTY720+HSA group,FTY720+IFN-γgroup)after SCI to further determine whether FTY720 inhibits fibrotic scarring via the IFN-γpathway.Immunofluorescence staining was performed to detect the IFN-γdistribution,explore cellular source of IFN-γ,and to evaluate CD3~+T cell,PDGFRβ~+fibrotic scar,IFN-γ/IFN-γR signaling,CD68~+inflammation response,GFAP~-lesion size and NF~+axon regeneration at 14 or 28 days post-injury(dpi).Basso Mouse Scale(BMS)and footprint analysis were used to assess the neurological recovery at 28 dpi.Results:After SCI,IFN-γwas distributed around fibroblasts at 3,7,14,and 28 dpi.Moreover,IFN-γwas mainly secreted by T cells,the percentage of co-staining was as high as about 65%.In situ injection of IFN-γinto the normal spinal cord resulted in the fibrotic scar formation and inflammation response.After SCI the intraperitoneal injection of FTY720 and W146 both significantly reduced T cell infiltration,attenuated fibrotic scarring via inhibiting IFN-γ/IFN-γR pathway,while in situ injection of IFN-γdiminished the effect of FTY720 on reducing fibrotic scarring.FTY720 treatment inhibited CD68~+macrophages/microglia infiltration and inflammation.FTY720 treatment decreased GFAP~-lesion size.FTY720 treatment increased regeneration of NF~+and 5-HT~+axons and survival of Neu N~+neurons,improved BMS scores and had better results in footprint analysis,promoted axon regeneration and neurological recovery after SCI.Conclusions:Our study demonstrates that the inhibition of T cell-derived IFN-γby FTY720 suppressed fibrotic scarring and contributed to neurological recovery after SCI.