Protein kinase C activation stimulates mesenchymal stem cell adhesion through activation of focal adhesion kinase

Emerging evidence suggests that cell therapy with mesenchymal stem cells (MSCs) has beneficial effects on the injured heart. However, the decreased survival and/or adhesion of MSCs under ischemic conditions limits the application of cell transplantation as a therapeutic modality. We investigated a potential method of increasing the adhesion ability of MSCs to improve their efficacy in the ischemic heart. Treatment of MSCs with PKC activator, phorbol 12-myristate 13-acetate (PMA), increased cell adhesion and spreading in a dose-dependent method and significantly decreased detachment. When MSCs were treated with PKC inhibitor, that is, rottlerin, adhesion of MSCs was slightly diminished, and detachment was also decreased compared to the treatment with PMA. MSCs treated with both PMA and rottlerin behaved similarly to normal controls. In 3D matrix cardiogel, treatment with PMA increased the number of MSCs compared to the control group and MSCs treated with rottlerin. Expressions of focal adhesion kinase, cytoskeleton-associated proteins, and integrin subunits were clearly demonstrated in PMA-treated MSCs by immunoblotting and/or immunocytochemistry. The effect of PKC activator treatment on MSCs was validated in vivo. Following injection into rat hearts, the PMA-treated MSCs exhibited significantly higher retention in infarcted myocardium compared to the MSC group. Infarct size, fibrosis area, and apoptotic cells were reduced, and cardiac function was improved in rat hearts injected with PMA-treated MSCs compared to sham and/or MSC-implanted group. These results indicate that PKC activator is a potential target for niche manipulation to enhance adhesion of MSCs for cardiac regeneration.