Abstract 11163: Abi Gene Family, Member 3 (NESH) Binding Protein (ABI3bp) Regulates Cardiac Progenitor Cell (CPC) Differentiation and Proliferation
INTRODUCTION: The mammalian heart contains three major cell types, cardiomyocytes, smooth muscle cells, and endothelial cells, all of which are believed to derive from a common cardiac progenitor cell (CPC). Recent reports have shown the therapeutic potential of CPCs in the human heart following injury. We have identified Abi3bp as a protein important for CPC differentiation and proliferation.
METHODS: CPCs were isolated from wild-type and Abi3bp knockout mice. Stable knockdown of Abi3bp was achieved in wild-type CPCs by shRNA. Differentiation and proliferation were assessed by qPCR, immunocytochemistry, and/or flow cytometry. Activation of Akt and ERK pathways was assessed by immunoblot analysis.
RESULTS: Abi3bp knockdown increased CPC proliferation in vitro as determined by cell counting (n=3, p<0.001). Subsequent analysis of the cell cycle using a BrdU FACS method indicated that Abi3bp knockdown increased the number of CPCs in S-phase (n=3, p<0.001). In vivo, knockout of the Abi3bp gene was associated with an increased number and proliferation of CPCs (n=3, p<0.05). CPCs were cultured in differentiation media containing ascorbic acid for 14 days. Abi3bp mRNA levels increased ~100-fold (n=3, p<0.001) during CPC differentiation. Knockout of Abi3bp caused a marked inhibition in the expression of early (Gata4, Mef2C) and late (Troponin-T) cardiomyocyte markers as determined by qPCR and immunostaining (n=3, p<0.01). Similar findings were observed with shRNA mediated knockdown of Abi3bp in wild-type CPCs. Inhibition of the Abi3bp receptor integrin-beta1 via a blocking antibody prevented CPC cardiac cell differentiation (n=3, p<0.05). Abi3bp knockout CPCs cultured under differentiating conditions were found to have significantly higher levels of phospho-ERK than their wild-type counterparts (n=3, p<0.01); however phospho-Akt levels were reduced when compared to wild-type CPCs (n=3, p<0.01).
CONCLUSION: In short, we have identified Abi3bp as a novel protein that is important for CPC differentiation and proliferation.
- © 2013 by American Heart Association, Inc.