Assessing cardiomyocyte proliferative capacity in the newt heart and primary culture

Unlike humans, adult newts possess extraordinary abilities to functionally regenerate lost and injured organs, including cardiac muscle. The most remarkable feature of mature newt cardiomyocytes is their ability to reenter the cell cycle, undergo cell division, and serve as a reservoir for progenitor cells. There are, however, a number of unsolved questions concerning the cellular and molecular mechanisms that underlie this plasticity; for example, we still lack a deeper understanding of the cell-inherent properties of newt cardiomyocytes and to what degree they differ from their mammalian counterparts. Along with considerable morphological changes at the wound site, a striking feature shared by different regenerating tissues in the newt is an extensive and dynamic remodeling of the extracellular environment. The dynamic signaling between cardiomyocytes and extracellular environment is of eminent importance in the control of the differentiated state of the cell, but the molecular details remain elusive. In this chapter, we describe methods to assess cardiomyocyte proliferation in vivo and enrich primary cardiomyocytes from newt hearts to study their behavior, taking extracellular matrix components into consideration.