Calcium signaling in cultured human detrusor smooth muscle cells from patients with interstitial cystitis

Abstract

The objectives of this study were (1) to isolate and culture detrusor smooth muscle cells (DSMCs) from patients with interstitial cystitis (IC), and (2) to study the growth characteristics and intracellular calcium signaling in single DSMCs. Detrusor muscle biopsies were obtained from 8 women with diagnosed IC according to National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) criteria and 10 women with benign noninvasive bladder diseases undergoing cystoscopy. DSMCs were cultured using explant technique. Only 60% to 80% of explants from each IC patient resulted in growth compared with 80% to 99% in controls. The time to reach confluence after trypsination was 4 to 6 weeks for DSMCs from IC patients compared with 2 to 4 weeks for controls. There was no difference in immunohistochemical staining for smooth muscle α-actin. Transmission electron microscopy showed that the ultrastructural features were those of smooth muscle cells. The measurements of cytosolic free calcium [Ca2+]i were performed using fura-2 and fluorescence ratio microscopy. The calcium responses to histamine, leukotriene D4(LTD4), and substance P was investigated. The increase in [Ca2+]i after stimulation with these agonists either alone or together was the same. Furthermore, DSMCs from both IC patients and controls showed spontaneous calcium oscillations. Some cell preparations from 4 IC patients showed abnormally high spontaneous increases in [Ca2+]i . The spontaneous oscillations were abolished in calcium-free medium. We conclude that stimulation with histamine, LTD4, and substance P induced similar increases in [Ca2+]i, but DSMCs from IC patients showed a slower growth rate and abnormal spontaneous Ca2+ oscillations compared with controls.