Promoted Differentiation of Mesenchymal Stem Cells using a Stretchable Piezoelectric Substrate for Regeneration of Myocardium and Skeletal Muscle

Abstract

In native muscle microenvironment, electrical and mechanical stimuli exist in the form of action potential and muscle contraction. Here we developed a cell culture system that can mimic the in vivo microenvironment and provide these stimuli to cultured cells and investigated whether the stimulation can promote myogenic differentiation of human mesenchymal stem cells (hMSCs). Ex vivo induction of myogenic differentiation of MSCs prior to implantation would potentiate therapeutic efficacy of stem cell therapies for muscle diseases, since MSCs rarely undergo myogenic differentiation following implantation. In muscle microenvironments, electric pulse and cyclic mechanical strain are sequentially produced. However, no study has applied the pulsatile mechanoelectric cues (PMEC) to stimulate myogenic differentiation of MSCs ex vivo. Stretchable and piezoelectric substrate (SPS) was fabricated by polydimethylsiloxane spin-coating on aligned ZnO nanorods. PMEC were provided to hMSCs cultured on SPS by subjecting SPS to cyclic stretching and bending, resulting in significantly promoted myogenic differentiation of hMSCs as well as intracellular signaling related to the differentiation. There are three types of muscle in human body: cardiac muscle, skeletal muscle, and smooth muscle. In the present study, we have focused on hMSCs differentiation into cardiac muscle cells and skeletal muscle cells in part 3 and 4, respectively. In part 3, bone marrow-derived hMSCs were induced to differentiate into cardiomyocytes to confirm the efficiency of PMEC for myogenic differentiation. Furthermore, in part 4, human umbilical cord blood MSCs were induced to differentiate into skeletal myocyte on pNIPAAm-engrafted thermosensitive SPS (TSPS). Following differentiation ex vivo, the cells were detached from TSPS in the form of cell-sheet fragments by changing the temperature to 4°C. The injection of cell-sheet fragments of differentiated cells into injured skeletal muscle in mice showed improved cell retention and muscle regeneration compared to injection of either undifferentiated cells or differentiated/dissociated cells. Our system may provide a tool for study of electrical and mechanical regulation of stem cells and be utilized to potentiate stem cell therapies.