Abstract 553: Loss Of Endothelial Bag3 Does Not Worsen Ischemia Induced Myopathy

Chronic limb threatening ischemia (CLTI), the most severe manifestation of peripheral artery disease, isaccompanied by high rates of limb amputation and death. There is a pressing need for novel therapydevelopment in these patients, which will require a thorough understanding of the individual cellularcontributions to ischemic limb pathology. BAG3 is a multifunctional adaptor protein that regulatesdiverse cellular functions. Mutations in BAG3 now appear to be one of the most common to causedisease in the clinical setting, including predisposing Black patients to cardiovascular disease. Wepreviously identified a coding variant in Bag3 that contributes to ischemic muscle necrosis after murinehindlimb ischemia (HLI) that was rescued by gene therapy, although we do not know which cell typesrequire Bag3 individually to mount efficient responses to ischemia. We hypothesized that vascularendothelial cell Bag3 would be required for both the restoration of blood flow and muscle function afterHLI. To test this hypothesis, we generated an inducible genetic model of endothelial cell Bag3 deletion(Cdh5(PAC)-CreERT2;Bag3 -/- ). At 20 weeks of age, mice were administered either tamoxifen (KO; n =20) orvehicle (CON, n =28) and evaluated at baseline or subjected to HLI for 7-days. Endothelial cell specific Bag3 deletion was validated first by genotyping and then by qRT-PCR in flow sorted cells. KO did notalter animal body weights, heart or skeletal muscle wet weights, physiologic muscle function (extensordigitorum longus absolute or specific force) or muscle histology (no regression of limb muscle tissuevascular cells) at baseline when compared with CON. After HLI, KO did not cause limb tissue necrosis,reduce limb blood flow recovery (laser doppler perfusion imaging) or physiologic muscle function, anddid not worsen histological damage to the limb muscle when compared with CON. Our study providesevidence for the first time that loss of endothelial cell Bag3 does not exacerbate myopathy and delaylimb blood flow recovery after hindlimb ischemia and suggests that the benefits of Bag3 gene therapymay be driven by the muscle cell compartment of the ischemic limb.