IntroductionOne of the main causes of death in the world, and in Mexico, is myocardial infarction (MI). During myocardial infarction the cardiac muscle undergoes hypoxia which leads to the death of cardiomyocytes, consequently of the muscle tissue that replaces the fibrous collagen scar and compromises cardiac function. Since this only affects the infarcted area, many patients would benefit from small pieces of muscle for transplantation. Cardiac tissue engineering promises to bring significant advances in the treatment of these patients. One of the foundations of this field is the development of materials that can support cell growth and mechanically assist the cardiac wall. Therefore, studying the cellular response to a material can help determine whether it will produce cytotoxic effects and whether it has adequate physicochemical properties to promote cell adhesion and growth (4). Previous work has shown that polyurethanes have favorable properties for supporting cells for cardiac tissue engineering. Parrag et al, for example, cultured murine embryonic stem cell-derived cardiomyocytes on polyurethane films with good cell survival rates. Sca-1+/CD45- cardiac progenitor cells (CPCs) have been shown to be responsible for cardiac homeostasis and represent a suitable cell source for cardiac tissue engineering (8, 9), making them ideal as a cell line. target cell since they are could repopulate the material in vitro and then differentiate in vivo. We performed cellular studies on putrescine-based biodegradable elastomeric polyurethane ureas to measure the proliferation of sca-1+/CD45- cells and the cytotoxicity of the materials. These studies represent the preliminary work needed to move forward in using these materials to create tissue-engineered cardiac patches. Materials and methods Synthesis We synthesized four… paper halves… CPCs on films of these materials and found they have slower proliferation rates than those of the TCPS control, which we attributed to the release of putrescine analogs. However, the mechanical properties and cell survival results suggest that these PUUs could have promising use as scaffold materials for cardiac tissue engineering applications such as a cardiac patch. Acknowledgments The authors would like to thank the Consejo Nacional de Ciencia y tecnología (CONACYT) of Mexico for financial support; A. Paredes-Puerto received a scholarship from CONACYT. We would also like to thank the Laboratory of Biomimetic Materials and Tissue Engineering at UC Berkeley for the use of the facilities and funding provided to A. Paredes-Puerto. We also thank Dr. Jianqin Ye for obtaining the original cardiac progenitor cells at UCSF that we subsequently used for this work.