Initial characterization of exstrophy bladder smooth muscle cells in culture

Previous studies have suggested that exstrophic bladder smooth muscle cells grown in culture show contractility similar to that of normal bladder smooth muscle cells. Despite this similar contractility, other cellular characteristics may vary between exstrophic and normal bladder smooth muscle cells.

Primary cultures of bladder smooth muscle cells were established from patients with bladder exstrophy (14) and vesicoureteral reflux as a control (10). Expression of smooth muscle specific α-actin and heavy chain myosin was determined with immunohistochemistry. Response of smooth muscle cells to high potassium Krebs solution or acetylcholine (0.1 mM) was assessed using a calcium sensitive fluorescent dye. Intracellular calcium concentration was measured after 48 hours in basal media. Cell migration in basal media during 24 hours was determined using transwell assays. Baseline proliferation and response to 10% fetal bovine serum were assessed with bromodeoxyuridine incorporation assays.

More than 95% of exstrophy and control smooth muscle cells stained positive for actin and myosin. Functional integrity was verified in each exstrophy and control cell line by response to high potassium Krebs solution or acetylcholine. The intracellular calcium concentration was lower in exstrophy smooth muscle cells than in control smooth muscle cells (71 vs 136 nM, p <0.001). More exstrophy cells migrated than control cells (37% vs 18%, p = 0.004). There was no statistically significant difference in proliferation between exstrophy and control smooth muscle cells in basal or growth media.

Cultured exstrophy smooth muscle cells demonstrate some differences in baseline characteristics compared to control cells. Differences in migration and intracellular calcium may have implications for in vivo detrusor function and tissue engineering.