Abstract: FR-PO175

Osteopontin Deficiency Ameliorates Alport Pathology by Preventing DNM3-Mediated Cholesterol Influx and Mitochondrial Energetic Deficit

Session Information

  • Mitochondriacs and More
    November 03, 2017 | Location: Hall H, Morial Convention Center
    Abstract Time: 10:00 AM - 10:00 AM

Category: Genetic Diseases of the Kidney

  • 802 Non-Cystic Mendelian Diseases

Authors

  • Ding, Wen, University of Miami Miller School of Medicine, Miami, Florida, United States
  • Yousefi, Keyvan, University of Miami-Miller School of Medicine, Miami, Florida, United States
  • Goncalves, Stefania, University of Miami Miller School of Medicine, Miami, Florida, United States
  • Goldstein, Bradley J., University of Miami, Miami, Florida, United States
  • Sabater, Alfonso L, Bascom Palmer Eye Institute, Miami, Florida, United States
  • Mendez, Armando, UM, Miami, Florida, United States
  • Shehadeh, Lina, University of Miami, Miami, Florida, United States
Background

Clinical implications of Alport Syndrome consist of proteinuria, hypertension, progressive renal failure, high frequency sensorineural hearing loss and ocular anomalies. Osteopontin (OPN) has not been studied in Alport Syndrome. We elected to investigate the role of OPN in Alport pathology.

Methods

At 8-9 weeks of age, WT, OPN-/-, COL4A3-/-, COL4A3-/-OPN+/-, COL4A3-/-OPN-/-, and COL4A3-/-LDLR+/- mice (n=7-25/group) were studied. Renal OPN protein expression was studied by immunofluoresce. KIM-1 protein expression and EdU and TUNEL staining were analyzed by immunofluorescence. Blood pressure was recorded by a tail cuff. Basement membrane morphology in kidneys, cochleas, and retinas was analyzed by electron microscopy. Optical coherence tomography was used to study corneal dimensions. 100ug DiI-LDL was injected via tail vein in Alport and wild type mice and kidneys were studied after 2 hours. Bioenergetics assays were performed on DNM3-over-expressing human tubular epithelial HK2 cells (or their isolated mitochondria) using a flux analyzer.

Results

We found that OPN is highly expressed in the renal tubules (not glomeruli) of the Alport mouse and plays a causative pathological role. OPN genetic deletion ameliorated albuminuria, hypertension, tubulointerstitial proliferation, renal apoptosis, lenticonus, and cochlear and retinal structural deficits in the Alport mouse. We found extensive cholesterol accumulation and increased protein expression of DNM3 and LDLR in Alport renal tubules. Increased pathological cholesterol influx was confirmed by a remarkably increased 50 fold uptake of injected DiI-LDL cholesterol by Alport renal tubules, and by the extended lifespan of the Alport mice when crossed with the LDLR-/- mice with defective cholesterol influx. Over-expressing DNM3 in HK2 cells resulted in elevated LDLR protein expression and defective fatty acid based- mitochondrial respiration, and impaired phosphorylating respiration, resting respiration, and maximal uncoupling respiration relative to the scrambled groups. All results reported here were statistically significant (at least p<0.05).

Conclusion

Our results suggest a new pathway in Alport pathology where renal tubular OPN causes DNM3-mediated enhanced cholesterol influx and reduced mitochondrial respiration.

Funding

  • Other NIH Support