MG53 in Kidney Injury and Fibrosis

Background: MG53 (TRIM72) is a muscle-predominant protein and functions as a circulating myokine that appears to confer tissue protection during ischemia-reperfusion (I/R) acute kidney injury and UUO-mediated kidney fibrosis. We discovered the functional duality of MG53 in kidney protection serving as a membrane repair protein and modulating the immune response during kidney inflammation. To further identify whether elevated level of either circulating MG53 or kidney proximal tubule-specific MG53 over-expression impact on kidney injury and fibrosis, we generated transgenic ctPA-MG53 mouse strain for conditional circulation and kidney MG53 over-expression to facilitate studying the role of MG53 in kidney disease and its impact on AKI-to-CKD transition. Methods: We generated mouse strain “TRE-STOPflox-tPA-MG53” (“ctPA-MG53”) as conditional MG53 over-expression in kidney PTE cells and circulation. This mouse strain was bred to PEPCKcre (kidney PTE expression) mice. We examined and confirmed the doxycycline (DOX) induction of the ctPA-MG53 of kidney overexpression. We characterized these mouse strains – Control: “X/Y, ctPA-MG53” and the conditional overexpression “PEPCKcre/Y, ctPAMG53” on a DOX time-dependent MG53 expression. We established a kidney bilateral (bIRI) mouse model to study AKI-to-CKD transition. Additionally, using Lenti-viral gene transduction system, we successfully engineered in human PTE HKC8 cells with scramble knockdown, MG53 knockdown and MG53 overexpressing HKC8 cells as an in vitro system to study the cellular mechanisms. Results: The transgenic “PEPCKcre/Y, ctPAMG53” mice follow a DOX-dependent and PTE specific MG53 induction. One week of DOX will induce a greater than 20-fold increase in kidney MG53 (protein) levels in proximal tubule cells and simultaneously high level of circulating MG53. Initial characterization of tissue expression of MG53 indicated an elevation in liver as well. We also did initial kidney functional characterization on these transgenic mice on DOX time-dependent induction. We subjected engineered HKC8 cells to various oxidative stress inducers and showed that MG53 over-expression confers better cell survival upon ROS stimulation. Conclusion: We have established an in vivo animal system to study the impact of MG53 in AKI-to-CKD progression. We also established an in vitro system to investigate MG53 in ROS protection and its cellular mechanism. Funding: NIDDK Support - NIDDK Support, NIDDK Support