Endothelial autophagy and Endothelial-to-Mesenchymal Transition (EndoMT) in eEPC treatment of ischemic AKI.
BACKGROUND
Autophagy enables cells to digest endogenous/exogenous waste products, thus potentially prolonging the cellular lifespan. Early endothelial progenitor cells (eEPCs) protect mice from ischemic acute kidney injury (AKI). The mid-term prognosis in AKI critically depends on vascular rarefication and interstitial fibrosis with the latter partly being induced by mesenchymal transdifferentiation of endothelial cells (EndoMT). This study aimed to determine the impact of eEPC preconditioning with different autophagy inducing agents [suberoylanilide hydroxamic acid (SAHA)/temsirolimus] in ischemic AKI.


METHODS
Male C57/Bl6 N mice were subjected to bilateral renal ischemia (40 min). Animals were injected with either untreated, or SAHA- or temsirolimus-pretreated syngeneic murine eEPCs at the time of reperfusion. Mice were analyzed 48 h and 4 weeks later. In addition, cultured eEPCs were treated with transforming growth factor (TGF)-β ± SAHA, autophagy (perinuclear LC3-II), and stress-induced premature senescence (SIPS-senescence-associated β-galactosidase, SA-β-Gal), and were evaluated 96 h later.


RESULTS
Cultured eEPCs showed reduced perinuclear density of LC3-II + vesicles and elevated levels of SA-β-Gal after treatment with TGF-β alone, indicating impaired autophagy and aggravated SIPS. These effects were completely abrogated by SAHA. Systemic administration of either SAHA or tems pretreated eEPCs resulted in elevated intrarenal endothelial p62 at 48 h and 4 weeks, indicating stimulated endothelial autophagy. This effect was most pronounced after injection of SAHA-treated eEPCs. At 4 weeks endothelial expression of mesenchymal alpha-smooth muscle actin (αSMA) was reduced in animals receiving untreated and SAHA-pretreated cells. In addition, SAHA-treated cells reduced fibrosis at week 4. Tems in contrast aggravated EndoMT. Postischemic renal function declined after renal ischemia and remained unaffected in all experimental cell treatment groups.


CONCLUSIONS
In ischemic AKI, intrarenal endothelial autophagy may be stabilized by systemic administration of pharmacologically preconditioned eEPCs. Early EPCs can reduce postischemic EndoMT and fibrosis in the mid-term. Autophagy induction in eEPCs either increases or decreases the mesenchymal properties of intrarenal endothelial cells, depending on the substance being used. Thus, endothelial autophagy induction in ischemic AKI, mediated by eEPCs is not a renoprotective event per se.
Clinic of Nephrology and Rheumatology, University Medical Center of Göttingen, Robert-Koch-Straße 40, 37075, Göttingen, Germany. d.patschan@gmail.com.
Daniel
D
Patschan
Clinic of Nephrology and Rheumatology, University Medical Center of Göttingen, Robert-Koch-Straße 40, 37075, Göttingen, Germany.
Katrin
K
Schwarze
Clinic of Nephrology and Rheumatology, University Medical Center of Göttingen, Robert-Koch-Straße 40, 37075, Göttingen, Germany.
Elvira
E
Henze
Clinic of Nephrology and Rheumatology, University Medical Center of Göttingen, Robert-Koch-Straße 40, 37075, Göttingen, Germany.
Susann
S
Patschan
Clinic of Nephrology and Rheumatology, University Medical Center of Göttingen, Robert-Koch-Straße 40, 37075, Göttingen, Germany.
Gerhard Anton
GA
Müller
D000199:Actins / Q000378:metabolism; D058186:Acute Kidney Injury / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D000818:Animals; D001343:Autophagy / Q000187:drug effects*; D002478:Cells, Cultured; D004195:Disease Models, Animal; D066026:Endothelial Progenitor Cells / Q000187:drug effects* / Q000378:metabolism / Q000637:transplantation*; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects*; D005355:Fibrosis; D006877:Hydroxamic Acids / Q000494:pharmacology*; D007511:Ischemia / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D007668:Kidney / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D008810:Mice, Inbred C57BL; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D010641:Phenotype; D020123:Sirolimus / Q000031:analogs & derivatives* / Q000494:pharmacology; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D000077337:Vorinostat; D001616:beta-Galactosidase / Q000378:metabolism
D000199:Actins; D006877:Hydroxamic Acids; C480860:Map1lc3b protein, mouse; D008869:Microtubule-Associated Proteins; D016212:Transforming Growth Factor beta; C544013:alpha-smooth muscle actin, mouse; D000077337:Vorinostat; C401859:temsirolimus; D001616:beta-Galactosidase; D020123:Sirolimus
AKI; EPCs; EndoMT; Endothelial autophagy