Expression of heat shock protein 27 correlates with actin cytoskeletal dynamics and contractility of cultured human bladder smooth muscle cells

Heat shock protein 27 (HSP27) is one of the most important chaperone proteins that modulates smooth muscle contraction. Here we investigated the effects of HSP27 expression on cytoskeleton dynamics and contractile function of human bladder smooth muscle cells (BSMCs) in vitro. Cultured human BSMCs were transfected with lentiviral vectors expressing either HSP27 or HSP27-siRNAs. Normal BSMCs cells and cells transfected with the empty lentivirus were used as control. Cells were then cultured on Flexcell flexible membrane dishes and mechanical stretch (14.8% elongation) was applied. The stretch caused significant disruption of actin cytoskeletal structure and decrease in F/G-actin ratio in BSMCs with HSP27 over-expression, knock-down and control groups (P<0.05) as indicated by phalloidin-FITC staining. It was also shown that the structure of actin filaments in HSP27 over-expressed cells recovered and F/G-actin ratio significantly increased at 12 h after stretching compared to unstretched cells (P<0.05), but not in HSP27 knock-down cells, suggesting that HSP27 promoted the recovery of cytoskeletal structure in BSMCs from stretch-induced injury. In addition, the contractile force of BSMCs was enhanced by over-expression of HSP27 and attenuated by knock-down of HSP27 (P<0.05), suggesting a pivotal role of HSP27 in regulating bladder smooth muscle contraction.