EPITHELIAL RXFP1 EXPRESSION IN MODELS OF INHERITED CYSTIC KIDNEY DISEASE
Carol Deaton, Heather Ward.
University of New Mexico, Albuquerque, NM.
Autosomal dominant polycystic kidney disease (ADPKD) has no cure and affects approximately 600,000 Americans, with therapy costing more than $2 billion per year. Mutant proteins linked to ADPKD cause up-regulated cellular proliferation, which contributes to renal cyst growth, fibrosis, and, ultimately, end-stage kidney failure. The relaxin-H2 hormone decreases proliferation in non-epithelial cell types indicating possible mitigation of ADPKD pathogenesis. Therefore, we treated cystic Cy/+ male rats with relaxin-H2 for two weeks and found that renal function was improved and cellular proliferation and cyst area were decreased in relaxin-treated animals compared to vehicle controls. Thus, we hypothesized that the relaxin-H2 receptor, RXFP1, is expressed on cystic renal epithelia and is therapeutically activated by relaxin-H2 ligand. To test our hypothesis, we used immunohistochemical, immunofluorescent, and spectral imaging techniques to evaluate RXFP1 expression in multiple cystic kidney disease models. We identified RXFP1 on the apical surface of renal cysts in all tested models. Furthermore, we determined RXFP1 expression was not limited to specific tubule segments. Considering relaxin-mediated activation of RXFP1 inhibits TGF-β receptor signaling, we predicted that activation of downstream transcription factor, SMAD2, would be decreased in cystic rats treated with relaxin-H2. Thus, we developed a spectral imaging protocol to quantify nuclear expression of active, phosphorylated SMAD2. Our protocol will allow us to detect changes in cellular signaling within tissue sections. Conclusively, our findings regarding RXFP1 expression on cystic kidney epithelia indicate that RXFP1 is a potential therapeutic target for reducing pathogenic cellular proliferation in ADPKD.