The purinergic component of human bladder smooth muscle cells' proliferation and contraction under physiological...

To investigate whether cyclic stretch induces proliferation and contraction of human smooth muscle cells (HBSMCs), mediated by P2X purinoceptor 1 and 2 and the signal transduction mechanisms of this process.

HBSMCs were seeded on silicone membrane and stretched under varying parameters; (equibiaxial elongation: 2.5%, 5%, 10%, 15%, 20%, 25%), (Frequency: 0.05Hz, 0.1Hz, 0.2Hz, 0.5Hz, 1Hz). 5-Bromo-2-deoxyuridine assay was employed for proliferative studies. Contractility of the cells was determined using collagen gel contraction assay. After optimal physiological stretch was established; P2X1 and P2X2 were analyzed by real time polymerase chain reaction and Western Blot. Specificity of purinoceptors was maintained by employing specific inhibitors; (NF023 for P2X1, and A317491for P2X2), in some experiments.

Optimum proliferation and contractility were observed at 5% and 10% equibiaxial stretching respectively, applied at a frequency of 0.1Hz; At 5% stretch, proliferation increased from 0.837±0.026 (control) to 1.462±0.023%, p<0.05. Mean contraction at 10% stretching increased from 31.7±2.3%, (control) to 78.28 ±1.45%, p< 0.05. Expression of P2X1 and P2X2 was upregulated after application of stretch. Inhibition had effects on proliferation (1.232±0.051, p<0.05 NF023) and (1.302±0.021, p<0.05 A314791) while contractility was markedly reduced (68.24±2.31, p<0.05 NF023) and (73.2±2.87, p<0.05 A314791). These findings shows that mechanical stretch can promote magnitude-dependent proliferative and contractile modulation of HBSMCs in vitro, and P2X1 and 2 are at least partially responsible in this process.