Mechanoregulation of intracellular Ca2+ in human autosomal recessive polycystic kidney disease cyst-lining renal epithelial cells

Mutations of cilia-expressed proteins are associated with an attenuated shear-induced increase in intracellular Ca2+ concentration ([Ca2+](i)) in renal epithelial cell lines derived from murine models of autosomal recessive polycystic kidney disease (ARPKD). We hypothesized that human ARPKD cyst-lining renal epithelial cells also exhibited dysregulated mechanosensation. To test this, conditionally immortalized cell lines derived from human fetal ARPKD cyst-lining (pool and clone 5E) cell lines with low levels of fibrocystin/polyductin expression and age-matched normal collecting tubule [human fetal collecting tubule (HFCT) pool and clone 2C] cell lines were grown in culture, loaded with a Ca2+ indicator dye, and subjected to laminar shear. Clonal cell lines were derived from single cells present in pools of cells from cyst-lining and collecting tubules, microdissected from human kidney. Resting and peak [Ca2+](i) were similar between ARPKD 5E and pool, and HFCT 2C and pool; however, the flow-induced peak [Ca2+](i) was greater in ARPKD 5E (700 +/- 87 nM, n = 21) than in HFCT 2C (315 +/- 58 nM, n = 12; P < 0.01) cells. ARPKD 5E cells treated with Gd3+, an inhibitor of nonselective cation channels, inhibited but did not abolish the shear-induced [Ca2+](i) transient. Cilia were similar to 20% shorter in ARPKD than HFCT cells, but no difference in ciliary localization or total cellular expression of polycystin-2, a mechanosenory Gd3+-sensitive cation channel, was detected between ARPKD and HFCT cells. The intracellular Ca2+ stores were similar between cells. In summary, human ARPKD cells exhibit an exaggerated Gd3+-sensitive mechano-induced Ca2+ response compared with controls; whether this represents dysregulated polycystin-2 activity in ARPKD cells remains to be explored.