Characterization of cultured bladder smooth muscle cells: Assessment of invitro contractility

Purpose: The contractile properties of in vitro cultured bladder smooth mus cle cells (SMC) are unknown. This study characterized the in vitro contract ile response of human and rat bladder SMC to several pharmacological agonis ts known to induce in vivo contraction of intact bladder muscle. Materials and Methods: Human and rat bladder SMC were seeded separately wit hin attached collagen lattices. Contractility of SMC was analyzed by measur ing alterations in lattice diameter after exposure and release to the follo wing contractile agonists: carbachol (10(-7) - 10(-3) M), calcium-ionophore (10 mu M), lysophosphatidic acid (LPA) (1 mu M), endothelin (0.1 mu M), KC l (3.33 mM) angiotensin II (10 mu M), and serotonin (100 mu M). Results wer e recorded as a mean reduction of the lattice diameter. In addition, immuno histochemical analysis for phenotypic markers of smooth muscle cell differe ntiation was performed on bladder SMC cultured within collagen lattices. Hu man palmar fascia fibroblasts, which have been previously well characterize d by in vitro contractility and immunohistochemistry, were tested in parall el and used as controls for all the above experiments. Results: Human SMC had significant contractile responses to calcium-ionopho re (31% +/- 4 relative percent contraction, p <0.05), LPA (34% +/- 4, p <0. 05), and endothelin (37 +/- 5%, p <05). There was no significant contractio n in response to carbachol, angiotensin II, KCI, or serotonin. Rat bladder SMC had a similar contractile response but did not contract in response to endothelin. In contrast to human and rat bladder SMC, fibroblasts did not c ontract to calcium-ionophore. Conclusions: In vitro cultured bladder SMC demonstrate loss of contractile response to normal in vivo pharmacologic agonists. Both human and rat bladd er SMC can be distinguished in vitro from fibroblasts based upon their lack of contractile response to calcium-ionophore. These results demonstrate th e ability to further characterize cultured bladder SMC with in vitro contra ctility. Further characterization is essential if we are to advance our und erstanding of the clinical applicability of in vitro studies utilizing cult ured bladder SMC.