KCa3.1 ion channel is expressed by component cells of lymphangioleiomyomatosis (LAM) nodules

Introduction: LAM is a rare lung disease characterised by progressive cystic destruction of the lung. There is no effective treatment. The hallmark lesion of LAM is the LAM nodule, a complex structure consisting of proliferating smooth muscle-like ‘LAM cells’, fibroblasts, lymphatic endothelial and inflammatory cells. KCa3.1 ion channels are implicated in several cell processes including proliferation, migration, differentiation and collagen secretion. We hypothesise that KCa3.1-dependent cell processes in LAM cells and LAM associated fibroblasts (LAFs) contribute to the development of LAM nodules and the accompanying lung damage. Methods: TSC null LAM cells and primary LAFs were obtained from the National Centre for LAM, Nottingham. We examined these cells for the presence of KCa3.1 channels using qRT-PCR and whole-cell patch clamp electrophysiology, and used immunohistochemistry to detect KCa3.1 in LAM tissue. We also examined the effects of KCa3.1 blockers on the formation of 3D LAM spheroids resulting from LAM cell and LAF co-culture. Results: Both LAM cells and LAFs (N=3 donors) expressed KCa3.1 mRNA. At rest, both LAM cells and LAFs displayed similar membrane currents with slight outward rectification at positive potentials. Both cell types responded to the KCa3.1 channel opener 1-EBIO with the development of characteristic KCa3.1 whole cell currents, which were blocked by the selective KCa3.1 blocker senicapoc. Immunoreactive KCa3.1 was present in LAM tissue, and inhibition of KCa3.1 channels inhibited the formation of LAM spheroids dose-dependently. Conclusion: LAM cells and primary LAFs express functional KCa3.1 channels which may contribute to the development of LAM nodules.