A novel two-step procedure to expand cardiac Sca-1+ cells clonally.

Resident cardiac stem cells (CSCs) are characterized by their capacity to self-renew in culture, and are multipotent for forming normal cell types in hearts. CSCs were originally isolated directly from enzymatically digested hearts using stem cell markers. However, long exposure to enzymatic digestion can affect the integrity of stem cell markers on the cell surface, and also compromise stem cell function. Alternatively resident CSCs can migrate from tissue explant and form cardiospheres in culture. However, fibroblast contamination can easily occur during CSC culture. To avoid these problems, we developed a two-step procedure by growing the cells before selecting the Sca-1+ cells and culturing in cardiac fibroblast conditioned medium, they avoid fibroblast overgrowth.