Fig. 6.

MR-L2 inhibits cyst formation in human models of ADPKD. (A) Treatment with the PDE4-selective inhibitor, rolipram, exacerbates the expansion of cysts formed by the OX161 cell line when grown in 3D culture. Data are expressed as a percentage of vehicle [0.1% (vol/vol) DMSO] control treatment and displayed as mean ± SEM of all cysts measured in each condition. (B) MR-L2 suppresses the formation of PGE2-stimulated OX161 cell cysts in a concentration-dependent manner. Mean cyst size is shown as a percentage of the PGE2-alone treatment group, where MR-L2 reduces mean cyst size to below unstimulated [0.1% (vol/vol) DMSO] levels. (C) Primary human cells from a patient with ADPKD were cultured from single kidney cysts. MR-L2 suppresses the spontaneous cyst formation of diseased primary human kidney epithelial cells. Cyst number decreases in response to MR-L2 treatment. Error bars represent the SD of four treatments. (D) MR-L2 suppresses the vasopressin-exacerbated, ADPKD-driven, cyst formation of diseased primary human kidney epithelial cells. Cyst number decreases in response to MR-L2 treatment. Error bars represent the SD of four treatments. (E and F) Primary human ADPKD cell viability was not adversely affected by MR-L2 treatment, as assessed using a luminescence-based detection of ATP as a function of living cells. Data are displayed in relative luminescence units, with error bars representing the SD of four treatments. (G) Composite confocal microscopy of primary human cystic cultures under treatment with 10 nM vasopressin and concentrations of MR-L2. Cystic structures are seen as spherical, lumen-forming, cellular outgrowths. Epithelial tubules and supporting cellular matrices are also present within the cultures but are not overtly affected by the presence of MR-L2 (additional imaging available in SI Appendix, Fig. S4).