Improving the efficacy of cell-based cardiac repair - Project Summary. Outcomes of heart repair with unmodified mesenchymal stem cells (MSCs) have been suboptimal. While developmental studies indicate a role of Wnt11 in cardiogenesis, Wnt11 signaling in apoptosis, angiogenesis, inflammation, and cardiac biology in adult organisms remains largely unexplored. We hypothesize that Wnt11-treated MSCs will induce superior infarct repair through greater MSC retention and survival, and manifold salubrious molecular effects on the myocardium. This hypothesis will be tested in cultured MSCs in vitro and a mouse model of reperfused myocardial infarction (MI) in vivo. To enhance the translational relevance of findings, human bone marrow MSCs and CD34+ humanized mice will also be used for key experiments. Aim 1 will examine whether recombinant Wnt11 (rWnt11) will render MSCs resistant to apoptosis and washout. Murine bone marrow MSCs will be cultured in medium alone (control) or with rWnt11, and expression of adhesion molecules, susceptibility to apoptosis, and the underlying molecular changes will be examined. The impact of rWnt11 on MSC retention will be tested in vivo following intramyocardial injection of EGFP+ MSCs after MI. Aim 2 will elucidate molecular mechanisms underlying the reparative benefits induced by rWnt11-treated MSCs. Angiogenic potential will be assessed by morphology, transcription factors and structural proteins. The role of Wnt/Planar Cell Polarity and Wnt/Ca2+ pathways will be interrogated using specific inhibitors. The impact of rWnt11 treatment on the expression of inflammation modulating molecules will be tested. The impact of rWnt11 on MSC secretome and the miRNA cargo in MSC extracellular vesicles will be analyzed. Aim 3 will establish whether transplantation of rWnt11-treated MSCs will induce superior infarct repair in vivo, and further identify the mechanistic basis in a definitive fashion. MSCs cultured in medium alone or with rWnt11 will be injected into the infarct borderzone 2 d after a reperfused MI. Serial echo and a terminal hemodynamic study will be performed to assess global and regional LV function and structure. LV anatomy, infarct size, myocyte hypertrophy, and fibrosis will be assessed by morphometry in myocardial sections. The effects of rWnt11-treated MSCs on myocyte apoptosis, angiogenesis, myocyte proliferation, calcium handling and gap junction proteins, myocardial inflammation, macrophage populations, and oxidative stress will be determined quantitatively at both early and late time-points. Focused proteomic analysis will identify novel myocardial protein modifications. In a comprehensive and thoroughly mechanistic fashion, these studies will establish whether rWnt11 treatment can improve MSC-induced infarct repair. The impact will be two-fold: (i) the generation of an effective cellular product for heart repair that can be produced easily in a GMP facility will have major therapeutic potential for patients with ischemic heart disease; and (ii) extensive molecular studies will yield novel biological insights about Wnt11 signaling in adult cells, and may also discover additional therapeutic targets to further enhance Wnt11-based cellular reparative strategies.
