| Implantation of stem cells into the diseased heart has shown initial promise, but the underlying mechanisms of functional improvement are not completely understood. The physiological cardiac environment is both chemically and mechanically dynamic. In order to understand how these stimuli influence stem cell behavior, the development of in vitro assays of cellular response to these factors was proposed. We describe the initial development of a quasi-three-dimensional (Q3D) experimental system that merges live cell imaging in chemically perfused buffers with mechanical manipulation of cellular attachments to a polymer microstructure. Specifically, the ubiquitous messenger intracellular calcium [Ca2+]int, is monitored as a global measure of cell activity and physiological significance. Next, both chemical and mechanical methodologies were used to investigate stem cell calcium response, allowing prediction of cell behavior upon implantation into their therapeutic milieu. To this end, an analysis of intracellular calcium activation for in vitro MDSCs was performed with the motivation of providing a better understanding the signaling properties of pre-implant MDSCs which leads to better understanding of their potential signaling response in vivo. Of particular interest was how MDSCs might couple to host cells in the engraftment site from a signaling perspective. Calcium signal transduction data from in vitro imaging assay in fibroblasts as well as calcium data from chemically and mechanically stimulated muscle-derived stem cell (MDSC) response is presented. Interestingly, while MDSCs responded vigorously to a small group of chemical calcium agonists, the response was minimal to a panel of other chemical agonists as well as commonly used biomechanical techniques. One potential explanation is that prior to division, expansion, and differentiation in vivo MDSCs shield themselves from the diverse signaling environment found in vivo by responding minimally to most agonists. |
