Effect of sustained hydrostatic pressure on rat bladder smooth muscle cell function.
OBJECTIVE
To test a hypothesis that bladder smooth muscle cells (BSMCs) shift their phenotype from contractile to synthetic in response to elevated hydrostatic pressure. Although mechanical stimuli are needed for development of the bladder, the exact mechanisms for this process are poorly understood.


METHODS
Rat BSMCs were exposed to 7.5 cm H(2)O of hydrostatic pressure in custom-made columns to a maximum of 48 hours. After exposure to pressure, the smooth muscle cells were fixed, stained, and imaged to quantify cell morphology and proliferation. Additionally, Western blotting was used to quantify extracellular signal-regulated kinase (ERK(1/2)) activation as well as phenotype marker proteins, alpha-smooth muscle actin, and SM-22.


RESULTS
Compared with the control, BSMCs exposed to hydrostatic pressure exhibited a more spread morphology after 4 hours and the expression of activated ERK(1/2) was a maximum of two-fold at 1.5-3 hours. Moreover, cell density of BSMCs exposed to hydrostatic pressure exhibited an increase after 48 hours when compared with their respective controls. In contrast, alpha-smooth muscle actin and SM-22 expression was similar in the control and in cells exposed to hydrostatic pressure for 48 hours.


CONCLUSIONS
The morphologic and proliferative changes of BSMC in response to hydrostatic pressure possibly indicate a phenotypic shift from contractile to synthetic. Moreover, the activation of ERK(1/2) intracellular signaling pathway may represent a potential mechanism for the pressure-induced BSMC proliferation. The comparable levels of contractile proteins observed in both control and pressure group BSMCs suggest that not all the phenotype markers are regulated concomitantly by a single stimulus.
Department of Bioengineering, Rhodes Engineering Research Center, Clemson University, Clemson, South Carolina 29634-0905, USA.
Margaret Rebecca
MR
Drumm
Brittany D
BD
York
Jiro
J
Nagatomi
D000818:Animals; D002478:Cells, Cultured; D005260:Female; D006874:Hydrostatic Pressure; D009130:Muscle, Smooth / Q000166:cytology* / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D001743:Urinary Bladder / Q000166:cytology* / Q000502:physiology*