Effects of aging and hypoxia on the proliferation of cultured rat pulmonary arterial smooth muscle cells

Objective To study the effects of aging and hypoxia on the proliferative behavior of cultured pulmonary arterial smooth muscle cells (PASMCs). Methods PASMCs isolated from aged (18-24 months) and young (3-4 months) rats were divided, according to the different treatments the cells were subjected to, into young and aged normoxic groups (groups A and B) and young and aged hypoxic groups (groups C and D) respectively. MTT cell proliferation assay, 3 H-TdR incorporation assay, flow cytometriy and immunocytochemical analysis were respectively employed to observe the proliferative behavior. Results Compared with the cells from young rats, PASMCs from aged rats had a higher proliferation rate, more 3 H-TdR incorporation, increased mitotic cell ratio, reduced amount of the total protein, and elevated content of proliferating cell nuclear antigen (PCNA). In comparison with normoxic condition, hypoxia elicited higher proliferation rate of the cells with inhibition of 3H-TdR incorporation that was subsequently increased. Higher percentage of mitotic cells, less total protein amount and increased PCNA were also observed in response to hypoxia. Conclusions Aging and hypoxia may directly induce PASMC proliferation, and in aging PASMCs, the proliferation is the most obvious in response to hypoxic stimulation.