Effects of regulatory factors on engineered cardiac tissue in vitro.

We tested the hypothesis that supplemental regulatory factors can improve the contractile properties and viability of cardiac tissue constructs cultured in vitro. Neonatal rat heart cells were cultured on porous collagen sponges for up to 8 days in basal medium or medium supplemented with insulin-like growth factor-I (IGF), insulin-transferrin-selenium (ITS), platelet-derived growth factor-BB (PDGF), or angiopoietin-1 (ANG). IGF and ITS enhanced contractile properties of the 8-day constructs significantly more than with unsupplemented controls according to contractile amplitude and excitation threshold, and IGF also significantly increased the amount of cardiac troponin-I and enhanced cell viability according to different assays (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), lactate dehydrogenase (LDH), and terminal deoxynucleotidyl transferase biotin-2'-deoxyuridine 5'-triphosphate nick end labeling (TUNEL)). PDGF significantly increased the contractile amplitude of 4-day constructs and enhanced cell viability according to MTT, LDH, and TUNEL; ANG enhanced cell viability according to the LDH assay. Our results demonstrate that supplemental regulatory molecules can differentially enhance properties of cardiac tissue constructs and imply that these constructs can provide a platform for systematic in vitro studies of the effects of complex stimuli that occur in vivo to improve our basic understanding of cardiogenesis and identify underlying mechanisms that can potentially be exploited to enhance myocardial regeneration.