3.5 | Mechanical stretching stress induces WISP-1 expression in LF cells
Growing evidence has suggested that WISP-1 is involved in the process of fibrosis in various organs (Sharma et al., 2010; Scotton et al., 2009). In the previous study, we found that WISP-1 was markedly upregulated in hypertrophic LF tissuse and highly associated with several fibrosis-relevant factors, including collagen expression, LF thickness and fibrosis score. As is known, mechanical stress is the main cause of LF degeneration (Yoshiiwa et al., 2016; Fukui et al., 2015). Therefore, we suspected that mechanical stress may be the cause resulted in he abnormal expression of WISP-1 in hypertrophic LF tissuse and hereinafter refer to the LF fibrosis. To ascertain this, we constructed an experimental device in which repeated cyclic mechanical stretching stimulation was applied to LF fibroblasts obtained from patients with LSCS. The strength of the stretching stimulation was estimated from the ratio of stimulation-induced cellular elongation to intrinsic cellular size before stimulation. We examined whether WISP-1 mRNA levels were increased by stretching stimulation of 5% and 10% elongation for 24h. As expected, WISP-1 mRNA expression in LF fibroblasts was markedly elevated by stretching stimulation, and the increase in WISP-1 expression tended to depend on the strength of the stretching stimulation (Figure 5A). Furthermore, immunofluorescence staining indicated that the expression of WISP-1 increased by 6h, 12h, and 24 h of mechnical stretching (10% elongation, Figure 5B). Consistently, the levels of WISP-1 mRNA and protein (Figure 5C) in LF cells were elevated in a time-dependent manner under the action of mechanical stretching (10% elongation).