Kidney Week

Abstract: SA-PO477

Myosin Activation as a Novel Therapeutic Strategy to Treat PKD in Human Kidney Organoids and Mice

Session Information

• Cystic Kidney Diseases: Basic/Translational
  November 09, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidneys

• 1001 Genetic Diseases of the Kidneys: Cystic

Authors

• Helms, Louisa, University of Washington, Seattle, Washington, United States

Louisa Helms,

• Gomez, Ivan G., University of Washington, Seattle, Washington, United States

Ivan G. Gomez,

• Cruz, Nelly M., University of Washington, Seattle, Washington, United States

Nelly M. Cruz,

• Freedman, Benjamin S., University of Washington, Seattle, Washington, United States

Benjamin S. Freedman,

Background

Polycystic kidney disease (PKD) is an autosomal dominant disorder that manifests from loss of function mutations in PKD1 or PKD2, encoding the proteins polycystin-1 (PC1) and polycystin-2 (PC2) respectively. The function of these proteins remain poorly understood and no curative therapeutics have been developed. Blebbistatin, a myosin inhibitor, was found to rapidly increase cyst proliferation in stem cell derived kidney organoids lacking PC1 or PC2. We hypothesize that non-muscle myosin II (NMII) activation will increase tubule epithelial cell contracility to reduce and prevent cystogenesis in PKD organoids and mice.

Methods

Stem cell derived kidney organoids genetically lacking PC1 or PC2 were differentiated over 18 days, picked, placed in suspension, and treated with blebbistatin or EMD, a small molecule myosin activator, every two days for two weeks. Organoids were measured for area, cystic index, stained for NMII, and toxicologically assessed. Pkd1^RC/RC mice at 20 weeks were intra-peritoneally injected with EMD every two days for four weeks, with blood urea nitrogen (BUN) levels measured. Post-sacrifice, mice kidneys were dissected, imaged, measured for weight and cyst number and histologically analyzed.

Results

In pre-cystic PC2 null organoids, EMD was able to reduce the total number of cysts in the organoids, as well as inhibiting the growth of cysts treated with blebbistatin in tandem. Cystic PC1 null organoids were treated with EMD resulting in the halt of cyst progression and gradual cyst reduction. NMII was enriched at the apical surface of tubules and showed dramatic stretching upon cyst initiation. No added toxicity was observed from EMD treatment. In Pkd1^RC/RC mice treated with EMD, EMD reduced the total burden of cysts, and reduced total kidney weight and BUN levels relative to their vehicle treated counterparts.

Conclusion

We have discovered a myosin activator that can prevent cysts from progressing in pre-cystic organoids, reduce cysts in post-cystic organoids, and shows efficacy in the Pkd1^RC/RC mouse model. Collectively, this supports our hypothesis that NMII contractility counteracts PKD cyst formation by stabilizing tubules. Myosin activation has significant potential to spur therapeutic progress for PKD in humans, and elucidate new mechanisms linking myosin to PKD pathogenesis.