Stem cell therapy is a regenerative medicine technique consisting in introducing new cells into a damaged tissue in order to restore it. In this paper we present our multidisciplinary approach about the possible use of the Human Mesenchymal Stem Cells in treating heart failure. A multidisciplinary team composed by biologists, mathematicians, cardiologists and bioengineers was selected in order to investigate the feasibility of repairing the necrotic tissue damaged by myocardial infarction by means of Mesenchymal Stem Cells and to implement a new software simulator able to reproduce cells implantation, migration and proliferation. In the first step, biologists and cardiologists studied the Human Mesenchymal Stem Cells and measured selected parameters. Stem cells were isolated and cultured in order to study their growth and characterization. In the second step, mathematicians and bioengineers developed a new numerical model based on the studies and the data measured during in vitro experiments. The first version of the software simulator named MiStTher is able to give a first qualitative description of the stem cell therapy in some simplified schemes.