Abstract 16630: Role of GPCR Signaling in Cardiac Progenitor Cells
Rationale: A better understanding of the signaling mechanisms controlling endogenous cardiac progenitor cell (CPC) proliferation, survival and differentiation would provide considerable insight into the use of pharmacological interventions to enhance CPC function and improve current treatments of heart failure.
Objective: To elucidate the effects of G-protein coupled receptor (GPCR) signalling on CPC function.
Methods and Results: Adult c-kit+ CPCs were isolated from adult mice. A GPCR TaqMan array was used to identify the receptors present in the cells. The complement of GPCRs on CPCs differed significantly from that of adult cardiomyocytes. We focused on exploring lysophospholipid (S1P and LPA) receptors as they have been implicated in non-cardiac stem cell function. Whereas S1P1R predominates in cardiomyocytes, the S1P2R is the most highly expressed in CPCs. S1P and LPA stimulated robust (∼3 fold) increases in CPC proliferation. When CPCs were pre-treated with the C3 exoenzyme to inhibit RhoA function proliferation in response to S1P was inhibited 50%. Treating with, siRNA for RhoA or for the S1P2 or S1P3 receptor (the subtypes known to activate RhoA) inhibited S1P induced proliferation while removal of the S1P1 receptor (which couple predominately to Gi) did not. S1P also attenuated CPC cell death induced by oxidative stress as assessed by TUNEL staining. To examine regulation of CPC differentiation, cells were treated with dexamethasone (Dex) with or without S1P or LPA for 3 days. Differentiation was analysed for lineage marker expression by qtPCR (cardiac-GATA4, MEF2c; smooth muscle-GATA6). S1P did not induce MEF2c or GATA6 transcription when compared to Dex alone. In contrast LPA induced CPC differentiation towards a cardiac lineage without affecting smooth muscle differentiation. The LPA receptor subtypes and signalling pathways promoting proliferation and differentiation are under study.
Conclusion: GPCR activation by lysophosholipids, inflammatory mediators expected to be elevated in the ischemic or injured heart, regulates CPC proliferation, survival and differentiation through tractable and distinct pathways that could be critical to CPC mediated repair.
- © 2012 by American Heart Association, Inc.