Intravesical pressure induces hyperplasia and hypertrophy of human bladder smooth muscle cells mediated by muscarinic receptors

PurposeBladder outlet obstruction with intravesical pressures exceeding 40 cmH2O results in a progressive increase in wall thickness, eventually causing low compliance. We investigated whether intravesical pressure induces hypertrophy and/or hyperplasia of human bladder smooth muscle cells (HBSMC) mediated by a muscarinic (M) receptor, and evaluated the relationship between intravesical pressure and M receptor antagonists.Materials and methodsHBSMC were exposed to 40 cmH2O pressure and/or acetylcholine (10 nM–100 μM) for 24 h. Cells exposed to hydrostatic pressure were treated with either 1 μM AF-DX 16 (M2 antagonist), 1 μM 4-DAMP (M3 antagonist) or 1 μM atropine (both M2 and M3 antagonists). DNA and protein synthesis of HBSMC were measured by 3H-thymidine and leucine incorporation assays, respectively.Results3H-thymidine incorporation increased following exposure to increasing concentrations of acetylcholine (at 100 μM, P < 0.05). When cells were exposed to 40 cmH2O for 24 h, 3H-thymidine incorporation increased by 31.4%, 33.3% and 39.5% in 1 μM, 10 μM and 100 μM of acetylcholine, respectively. With exposure to 100 μM acetylcholine, a hydrostatic pressure of 40 cm, and both of these together, 3H-thymidine incorporation increased by 16.7%, 25.9% and 39.4%, respectively, and leucine incorporation increased by 66.5%, 66.5% and 81.8%, respectively (P < 0.05). Antimuscarinic agents had no apparent effect on the proliferative rate of cells grown at atmospheric pressure, but there was a dramatic decrease in thymidine and leucine incorporation for cells that were simultaneously exposed to increased hydrostatic pressure, most pronounced when the combined M2/M3 receptor antagonist was applied.ConclusionsIntravesical pressure may induce hypertrophy/hyperplasia of HBSMC mediated by M receptors. Early use of an M receptor antagonist in cases of high intravesical pressure may have a positive effect on bladder compliance.