Hyaluronan Synthase-1 Contributes to Tubulointerstitial Fibrosis in a Murine Model of CKD

Background: Chronic kidney disease (CKD) is characterized by progressive tubulo-interstitial fibrosis leading to end-stage kidney disease. Mechanisms that initiate tubulo-interstitial fibrosis remains to be fully defined. We previously demonstrated that hyaluronan (HA) expression was increased in murine models of CKD and deletion of HA synthase-1 (HAS-1), an enzyme that synthesizes HA, attenuated histopathological changes and mediators of inflammation and fibrosis. This study compared transcriptomic profiling and molecular pathways in wild-type (WT) and HAS-1 knockout (KO) mice with CKD. Methods: CKD was induced in male WT and HAS-1 KO mice by feeding with casein-based chow containing 0.2% adenine for 12 weeks, after which time kidneys were harvested. Mice fed casein-based chow served as non-CKD controls. Total RNA was extracted from renal cortical tissue and subjected to bulk RNA-sequencing. Differentially expressed genes (DEGs) were identified based on ±1.2-fold change and adjusted p-value < 0.05 . Enrichment analyses were conducted for GO category genes and KEGG pathways. Results: Transcriptomic analysis identified a total of 11,783 DEGs (6,322 up-regulated genes and 5,461 down-regulated genes) in WT CKD mice compared to WT control mice (padj <0.05). Genes that were up-regulated included col1a1, col1a2, col3a1, dcn, fn1, lama2, lamb3, and lamc2 (padj<0.001). WT CKD mice showed GO enrichment in categories related to extracellular matrix (ECM) organization, immune response regulation and fibroblast proliferation (padj<0.001), and KEGG pathways such as cytokine-cytokine receptor interaction, ECM-receptor interaction, PI3K/AKT and MAPK signaling (padj<0.001). These GO and KEGG pathways were significantly altered in HAS-1 KO CKD mice (padj<0.001). Western blot analysis revealed increased phosphorylation of PI3K/AKT and p38 MAPK in WT CKD mice, which was significantly reduced in HAS-1 KO CKD mice. Conclusion: Our findings suggest that increased HAS-1 activity contributes to tubulo-interstitial fibrosis through up-regulation of ECM organization and induction of PI3K/AKT and p38 MAPK signaling. Funding: Government Support – Non-U.S.