Abstract: TH-PO590

Macrophage Depletion Leads to Temporal and Spatial Changes in miRNA Profiles That Drive Fibrosis in Autosomal Dominant Polycystic Kidney Disease (ADPKD)

Session Information

Category: Genetic Diseases of the Kidney

  • 801 Cystic Kidney Diseases

Authors

  • Patil, Ameya P., Medical College of Wisconsin, Wauwatosa, Wisconsin, United States
  • Sweeney, William E., Medical College of Wisconsin, Wauwatosa, Wisconsin, United States
  • Pan, Cynthia G., Medical College of Wisconsin, Wauwatosa, Wisconsin, United States
  • Avner, Ellis D., Medical College of Wisconsin, Wauwatosa, Wisconsin, United States
Background

In ADPKD, the decline in kidney function correlates with onset of fibrosis. Such fibrosis begins in peri-cystic areas (PA) between multiple cysts. Key factors involved in process of fibrosis include macrophages (Ø) at a cellular level and miRNAs at a molecular level. We hypothesize that localized changes in miRNA’s and Ø phenotypes drive fibrosis in ADPKD, and provide potential targets for future therapeutic intervention.

Methods

Cystic kidneys from mcwPkd1(nl/nl) mice and age matched controls at postnatal days (PN) 21, 28, 42 and 56 were evaluated. These stages encompasses the disease process from maximum cyst growth and total kidney volume (TKV) at PN28 to dramatically reduced TKV due to fibrosis at PN56. Clodronate, which eliminates Ø, was administered from PN14 to PN56. FFPE fixed cystic kidneys at PN 56 following clodronate treatment were analyzed with serial sections for miRNA, mRNA analysis and trichrome (TriC) and compared to age-matched untreated cystic kidneys. Øs and Ø phenotypes were analyzed by flow cytometry, IHC and IF in serial sections and following clodronate treatment.

Results

Flow cytometry reveals significant increase in Øs from PN21 to PN28. At PN21, Øs located in PAs express predominantly INOS, a marker for M1 Øs. Between PN28 and PN56, Øs predominantly express arginase, a marker of M2 Øs. These findings correlate directly with increasing TriC staining in PAs and the decline in renal function. As expected, clodronate treatment :1) depleted Øs in both spleen and kidney; 2) resulted in significantly less TriC positivity; and 3) inhibited the decrease in TKV. miRNA analysis of serial sections in both treated and untreated cystic kidney showed a total of 158 miRNA’s that were differentially expressed with 85 upregulated in treated kidneys. mRNA analysis on the same section was significant for differentially expressed AKT1 and EGF, 11 and 6.4-fold respectively.

Conclusion

(1) In this unique model of ADPKD; changes in Ø number and phenotype play a key role in fibrosis; (2) Changes in miRNA profiles after macrophage elimination with clodronate provide unique miRNA targets that may guide future therapeutic intervention; (3) This profile correlates with change in EGF and AKT which play critical roles in ADPKD.