CCN5 attenuates profibrotic phenotypes of fibroblasts through the Smad6-CCN2 pathway: Potential role in epidural fibrosis

Abstract

Epidural fibrosis is characterized by the development of dense and thick scar tissue adjacent to the dural mater and ranked as the major contributor for post-operative pain recurrence after laminectomy or discectomy. Recently, CCN5 exhibited an inhibitory effect on connective tissue growth factor (CTGF)/CCN2 (a critical regulator for fibrotic disease)-mediated fibrogenesis. However, its function in epidural fibrosis and the underlying mechanisms involved remain to be determined. In this study, an obvious downregulation of CCN5 was observed in scar tissues from laminectomized rats, concomitant with a marked upregulation of CCN2, suggesting a potential negative regulatory role of CCN5 in fibrogenesis. Furthermore, CCN5 overexpression notably mitigated transforming growth factor-β1-enhanced fibroblast viability and proliferation. Of note, CCN5 upregulation inhibited the switch of fibroblasts into myofibroblasts as its overexpression abrogated the expression of the myofibroblast marker, α-smooth muscle actin (α-SMA). CCN5 upregulation also reduced an increase in collagen type I, α1 (COL1A1) and total collagen concentrations. Additionally, CCN5 over expression decreased CCN2 expression and increased Smad6 phosphorylation. Mechanism analysis revealed that blocking Smad6 signaling significantly ameliorated the inhibitory effect of CCN5 on the CCN2 levels, accompanied by the reduction in cell proliferation and collagen production. These results confirm that CCN5 exerts an anti-fibrotic function by regulating the Smad6-CCN2 pathway, thereby indicating a potential approach for ameliorating epidural fibrosis after laminectomy.

Honokiol protects against epidural fibrosis by inhibiting fibroblast proliferation and extracellular matrix overproduction in rats post‑laminectomy

“…CTGF has been reported to mediate the TGF-β1-induced upregulation of collagen type I in fibroblasts ( 51 ). An increased CTGF expression in epidural scar tissue plays a key role in EF development by stimulating TGF-β1-induced fibroblast proliferation and ECM production, as well as collagen and fibronectin synthesis ( 13 ). As was expected, it was found that TGF-β1 treatment significantly stimulated the production of CTGF at both the gene and protein levels, which was reversed by honokiol in a dose-dependent manner.…”

Foxf2 and Smad6 co‐regulation of collagen 5A2 transcription is involved in the pathogenesis of intrauterine adhesion

“…In epidural fibrosis, CCN5 exerts anti-fibrotic effects by regulating the Smad6-CCN2 pathway. 42 Foxf2 and Smad6 play crucial roles in the production of collagen.…”

CCN5/WISP2 and metabolic diseases

“…There is mounting evidence that CCN5/WISP2 is anti-fibrotic and counteracts the effects of several fibrotic markers such as CTGF and α-SMA (Xu et al 2015a ; Xu et al 2015b ). In rat scar tissue, where epidural fibrosis was examined, CTGF was upregulated while CCN5/WISP2 was downregulated on both mRNA and protein level.…”

“…Blocking Smad6 phosphorylation ameliorated the inhibitory effect of CCN5/WISP2 on CTGF. When the Smad6 pathway was blocked using siRNA, cell proliferation was once again increased in Ccn5/Wisp2 -overexpressing cells following TGFβ1 stimulation (Xu et al 2015b ). CCN5/WISP2 also normalized the increased Akt phosphorylation induced by TGFβ in cardiac fibroblasts, consistent with the findings seen in fibroblasts of the lung (Jeong et al 2016 ; Zhang et al 2014 ).…”