Abstract 12638: The Activation of STAT3 via CamKII is Critical for the Induction of Cardiac Differentiation by Wnt11 in Bone Marrow Mesenchymal Stem Cells
Wnt11, a member of the evolutionarily conserved Wnt family of glycoproteins, plays important roles in cellular migration, proliferation, and differentiation during embryogenesis. Although Wnt11 induces cardiac differentiation in bone marrow cells, the underlying molecular mechanisms remain unclear. We hypothesized that Wnt11-induced cardiac differentiation of mesenchymal stem cells (MSCs) involves calcium-calmodulin dependent kinase II (CamKII), which is activated via the noncanonical Wnt-Calcium pathway. Murine MSCs were isolated by adhesion to plastic and propagated in culture. For Wnt11 exposure, MSCs were cultured on the bottom of plates with Wnt11-secreting 293 cells on inserts. Empty vector-bearing 293 cells served as controls. Exposure to Wnt11 increased the levels of both phosphorylated (activated) CamKII and p-STAT3 in MSCs (Fig. 1A). The addition of CamKII-bearing plasmids to culture increased p-STAT3 levels in MSCs in a dose-dependent fashion, indicating that CamKII can induce robust STAT3 activation in MSCs (Fig. 1B). Further, when Wnt11-exposed MSC homogenates were immunoprecipitated with anti-CamKII antibodies and immunoblotted for p-STAT3, the blots revealed physical association of CamKII with p-STAT3 (Fig. 1C), indicating a novel signaling paradigm in MSCs. Finally, the critical role of STAT3 in Wnt11-induced cardiac differentiation was confirmed with the use of a selective STAT3 inhibitor WP1066, which prevented the Wnt11-induced increase in cardiac transcription factor Nkx2.5 in MSCs (Fig. 1D). Consistently, in MSCs cultured in presence of Wnt11, the addition of STAT3 inhibitor WP1066 decreased the number of MSCs expressing cardiac-specific troponin T (Fig. 1E). We conclude that the activation of STAT3 via CamKII plays an essential role in the induction of cardiomyocytic differentiation of MSCs by Wnt11. This information may be utilized for effective cardiogenic priming of MSCs prior to transplantation for cardiac repair.
- © 2012 by American Heart Association, Inc.