Chronic sciatic nerve compression induces fibrosis in dorsal root ganglia.

In the present study, pathological alterations in neurons of the dorsal root ganglia (DRG) were investigated in a rat model of chronic sciatic nerve compression. The rat model of chronic sciatic nerve compression was established by placing a 1 cm Silastic tube around the right sciatic nerve. Histological examination was performed via Masson's trichrome staining. DRG injury was assessed using Fluoro Ruby (FR) or Fluoro Gold (FG). The expression levels of target genes were examined using reverse transcription­quantitative polymerase chain reaction, western blot and immunohistochemical analyses. At 3 weeks post­compression, collagen fiber accumulation was observed in the ipsilateral area and, at 8 weeks, excessive collagen formation with muscle atrophy was observed. The collagen volume fraction gradually and significantly increased following sciatic nerve compression. In the model rats, the numbers of FR­labeled DRG neurons were significantly higher, relative to the sham­operated group, however, the numbers of FG­labeled neurons were similar. In the ipsilateral DRG neurons of the model group, the levels of transforming growth factor­ß1 (TGF­ß1) and connective tissue growth factor (CTGF) were elevated and, surrounding the neurons, the levels of collagen type I were increased, compared with those in the contralateral DRG. In the ipsilateral DRG, chronic nerve compression was associated with significantly higher levels of phosphorylated (p)­extracellular signal­regulated kinase 1/2, and significantly lower levels of p­c­Jun N­terminal kinase and p­p38, compared with those in the contralateral DRGs. Chronic sciatic nerve compression likely induced DRG pathology by upregulating the expression levels of TGF­ß1, CTGF and collagen type I, with involvement of the mitogen­activated protein kinase signaling pathway.