Introduction: Prior research in our laboratory identified miR-146b as an important negative regulator of sex-specific renal pathology which is mediated by female gonadal hormones (1). Female miR-146b knockout (KO) Sprague Dawley rats with 5/6 nephrectomy (5/6Nx) exhibited exaggerated remnant kidney hypertrophy and fibrosis when compared to wild-type (WT) controls, and this was prevented if ovaries were removed (Ovx) during surgery (1). We hypothesized that 5/6Nx-related proximal tubule (PT) pathology, specifically dilation, would be similarly impacted by the loss of miR-146b and/or ovarian hormones. Further, we explored renal gene expression changes involved with cell proliferation in these models. Methods: Trichrome-stained kidney sections from female WT and miR-146b-/- rats that received sham or 5/6Nx surgery with or without Ovx (1) were scored for PT dilation (10 random fields/section). The analysis was performed in a blinded manner. The percentage of severely dilated tubules in each surgical group was analyzed using two-way ANOVA by genotype and reported as mean±SEM. Bulk RNA sequencing was performed on pooled kidney RNA (n= 3 animal samples per pool x 2 pools /study group), as previously described (2). Transcript expression Mki67, Mybl2, Plk1, Reg1a, and Azgp1 were compared between groups to assess molecular markers of cell proliferation. Results: In intact female rats, 5/6Nx caused an increase in the percentage of severely dilated PTs regardless of genotype, and this increase was significantly augmented in miR-146b KO rats (WT 30.72±12.71% vs. KO 82.74±4.55%). Ovx reduced PT dilation to 12.90±6.95% in KO and 14.13±7.08% (non-significant) in WT rats. Several dilated tubules exhibited an unexpected hyperplastic (stratified) epithelial phenotype (WT 4.37±1.94% in WT rats vs KO 10.19±2.45%), which was also nearly eliminated with Ovx. Proliferation markers Mki67, Mybl2, Plk1, and Reg1a were significantly increased by 5/6Nx in WT and miR-146b rats, while proliferation inhibitor Azgp1 was reduced. Expression of Azgp1 was lower in KO than WT 5/6Nx rats, and Ovx augmented Azp1 expression only in KO rats. Conclusion: Our results indicate a novel role of miR-146b and ovarian hormones in regulation of severe tubular dilation and cell proliferation, while also identifying hyperplasic/stratified epithelial phenotype in several tubules. These findings offer insight into how the intact ovarian hormones exacerbate 5/6Nx-related renal pathology in miR-146b KO compared to WT females. Citations:1) Paterson MR, et al. miR-146b-5p has a sex-specific role in renal and cardiac pathology in a rat model of chronic kidney disease. Kidney Int. 2019 Dec;96(6):1332-13452) Nasci VL, et al. Transcriptomic analysis identifies novel candidates in cardiorenal pathology mediated by chronic peritoneal dialysis. Sci Rep. 2023 Jun 21;13(1):10051. Support or Funding Information MCW Cardiovascular Center FY23 Pilot Award, T32 HL134643 This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Nguyen et al. (Fri,) studied this question.