Objective:To investigate the effects of small interference RNA (siRNA) against ribosomal protein L22(RPL22) on ET-1 induced proliferation of human pulmonary arterial smooth muscle cells (HPASMC). Methods:The experimental models of primary cultured HPASMC induced by ET-1 were established in vitro. HPASMC were transfected with siRNA-RPL22,incubated in smooth muscle cell culture medium (SMCM). The mRNA and protein expresson levels of RPL22 in HPASMC were measured by real-time PCR and Western blot,respectively. The HPASMC proliferation was evaluated by PCNA expression and flow cytometry analysis. Results:Compared with control groups,RPL22 expression in HPASMC was significantly inhibited after siRNA-RPL22 transfection(P < 0.05),and HPASMC proliferation was significantly inhibited after siRNA-RPL22 transfection. Conclusion:The data suggest that interruption of RPL22 expression can inhibit HPASMC proliferation. It’s a novel finding needs to be further explored.