Objective      To investigate the effect of low expression of heat shock protein 27 (HSP27) on actin skeleton structure and contraction function of human bladder smooth muscle cells (BSMCs) in vitro.       Methods      To inhibit the expression of HSP27

3 pairs of siRNA were designed

inserted into lentiviral vector pGreenPuro and transferred into human BSMCs. Phalloidin staining and F-actin/G-actin ratio detection were used to observe the actin skeleton structure and polymerization status in the cultured BSMCs. The bladder smooth muscle fibers were reconstructed by culturing BSMCs with collagens to evaluate the contractile force.       Results      Lentiviral vector pGreenPuro-sh-HSP27 was successfully constructed and transferred into the cultured BSMCs effectively. Low-expression of HSP27 caused significant disruption of actin skeleton structure and decrease of F-actin/G-actin ratio (0.116±0.001) in BSMCs compared with the normal control (8.717±0.500

P0.05). The contractile force(3.8±0.2 mg) of the reconstructed fibers was significantly attenuated by low-expression of HSP27 compared to the normal control (8.4±0.6 mg

P0.05) in the stimulation of 80 mmol/L KCl.       Conclusion      Low expression of HSP27 can impair contractile force of human BSMCs through altering the actin skeleton structure.