MicroRNA-21 is a key determinant in IL-11/Stat3 anti-apoptotic signalling pathway in preconditioning of skeletal myoblasts

We have previously shown that preconditioning of stem and progenitor cells promotes their survival post-engraftment in the infarcted heart. The present study was designed to (i) delineate the role of microRNA-21 (miR-21) in interleukin-11 (IL-11) signalling during preconditioning of skeletal myoblasts (MY) and (ii) study the long-term fate of preconditioned MY ((MY)-M-PC) post-transplantation in the infarcted heart. We report that pharmacological preconditioning of MY with diazoxide showed robust expression of IL-11 and activation of extracellular signal-regulated kinase 1/2 (Erk1/2) and signal transducers and activators of transcription-3 (Stat3) with concomitantly increased miR-21. These molecular events improved cytoprotection of (MY)-M-PC under oxidant stress in vitro which was compromised by pre-treatment of (MY)-M-PC with IL-11-specific siRNA, Erk1/2 blocker, or anti-miR-21. In vivo studies for sry-gene detection in a female rat heart model of acute myocardial infarction showed two-fold higher survival of male donor (MY)-M-PC 4 and 7 days post-engraftment. Long-term fate of the engrafted cells was determined at 4 months after transplantation. Immunohistological studies revealed that in comparison with non-PCMY, (MY)-M-PC improved angiogenic response in the heart which was evident from a higher number of blood vessels per surface area (0.155 mm(2)) and myogenic differentiation of (MY)-M-PC in the heart. Indices of myocardial contractility including ejection fraction and fractional shortening showed significant improvement in (MY)-M-PC-treated animals. miR-21 is a key regulator of Erk1/2-Stat3 signalling downstream of IL-11 during preconditioning of MY. The therapeutic benefits of (MY)-M-PC were stable and persisted until 4 months of observation.