Abstract 617: Phenotype as a Basis for Selection of BM-MSC-Derived SMCs for Regenerative Repair of Abdominal Aortic Aneurysms

Abstract

Abdominal aortic aneurysms (AAA) are a leading cause of death in the elderly with over 150,000 new diagnoses annually in the US. They involve bulging of the abdominal aorta due to chronic proteolytic degradation of the wall structural extracellular matrix (ECM), mainly elastin and collagen. There are currently no established medical management approaches for treating small AAAs and early surgical intervention provides no benefit. AAA growth arrest and regression are also prevented by inherently poor auto regenerative repair of elastic matrix by adult vascular smooth muscle cells (SMCs). We have identified bone marrow mesenchymal stem cell-derived SMCs (BM-SMCs) as superior cell types for regenerative cell therapy due to their high elastogenicity and pro-elastogenic and anti-proteolytic effects on AAA SMCs. In this study we investigated if and how phenotypic coordinates of BM-SMCs on a contractile to synthetic phenotypic continuum impact their above functional benefits. BM-SMC subpopulations were generated under 2% & 10% v/v FBS conditions in presence of transforming growth factor beta-1 (TGFβ), with or without platelet derived growth factor (PDGF-BB) under low & high glucose conditions. Phenotypic coordinates of the BM-SMCs were established by analysis of SMC marker (alpha SM actin (αSMA), SM22, caldesmon, smoothelin, MHC) expression with RT-PCR, western blotting, and immunofluorescence (IF) staining. Elastogenicities of the cell subpopulations were compared by analysis of tropoelastin and matrix elastin synthesis (Fastin assay), crosslinking (ELISA for desmosine), IF, and TEM; contractile properties were compared via a carbachol assay and whole cell patch-clamp for intracellular Ca 2+ /K + activity. Overall, our results indicate that 10% FBS + TGF with/without PDGF express higher contractile markers and higher elastic matrix yield when compared to controls (aortic SMCs and MSCs) and other test cases. Together with ongoing studies that are evaluating pro-elastogenic and anti-proteolytic effects of our generated BM-SMCs on AAA SMCs in non-contact coculture, we believe that the results are promising towards identifying superior elastogenic cell sources for a regenerative cell therapy for AAAs, which we are validating in a rat AAA model.