| Summary |
Cardiac muscle lacks the ability to repair after myocardial injury due to the nonproliferative qualities of cardiomyocytes. In recent years, significant improvement has been made in techniques involving cellular transplantation into damaged cardiac tissue, i.e. cellular cardiomyoplasty. Many cell types have been proposed for use in cellular cardiomyoplasty one type being the bone marrow derived mesenchymal stem cell. The goal of this study was to evaluate the effects of growth factors and mechanical strain on mesenchymal stem cell survival and differentiation to further the study of cell transplantation therapies for injured myocardium. It is hypothesized that pretreatment of mesenchymal stem cells with growth factors before transplantation might improve the therapeutic effectiveness of cellular cardiomyoplasty therapy. Additionally, mimicking a cardiovascular micro-environment via cyclic uniaxial mechanical strain may aid in the development and remodeling of mesenchymal stem cells by activating stretch-response genes committing a larger number of mesenchymal stem cells to a cardiogenic fate. The expression of the cardiac specific transcription factors and proteins in human mesenchymal stem cells treated with growth factors and/or mechanical strain were evaluated at 48 hrs and 7 days. Quantitative real time PCR analysis showed treatment with both growth factors and strain increased myocardin expression at 48 hrs. Treatment with growth factors alone resulted in a decrease in myocardin expression at 48 hrs. At 7 days a significant decrease in TRPAl expression was measured in cells treated with growth factors and strain. Western blot protein analysis showed significant increases measured in Cx43 at 7 days in cells treated with growth factors and strain. In the growth factor and strain treated groups an increase in proliferation was measured at 48 hrs with a subsequent decrease at 7 days. Other cardiac specific proteins and transcription factors analyzed such as Nkx2.5, Mef2C, Tbx5, N-cadherin, SERCA2, Ct-I, Sarcomeric alpha Actinin were undetected or remained unchanged suggesting that this combination of growth factor and strain treatment did not direct the hMSCs toward a fully functional cardiomyocyte phenotype in 7 days. Different combinations, concentrations and possible additions of other growth factors along with longer incubations ¡periods may be necessary to develop hMSCs full gene program necessary to commit to a cardiogenic fate. |
