Expression of cardiac specific genes and functional testing of engineered cardiac tissues

Abstract

Engineered cardiac tissues (ECT) may be useful for screening novel therapies if biologically similar to natural myocardium. To examine functional and molecular characteristics of ECT, 2 groups were created from cells in collagen I and Matrigel: ECT1=neonatal rat cardiomyocytes (NRCM 15M cells/ml) and ECT2=NRCM-depleted plus rat mesenchymal stem cells (7.5M NRCM/ml+0.75M MSC/ml). By functional analysis with field stimulation (12V, 5ms pulse, 1–7Hz) all ECT exhibited a negative force-frequency relation resembling rat myocardium, with no significant loss of developed force for NRCM-depleted MSC-supplemented ECT2. Real-time PCR analysis was performed for molecular cardiac markers α- and β-myosin heavy chain (αMHC, βMHC) and cardiac sarcoplasmic reticulum Ca++ ATPase (SERCA2a). Normalized to NRCM cell suspension (ΔΔCT method) fold-changes in expression were αMHC 4.7±1.3, βMHC 0.52±0.26, SERCA2 0.81±0.21 for ECT1 (N=2, mean±SD) which did not differ significantly from αMHC 5.1±1.5, βMHC 0.66±0.79, SERCA2 0.53±0.37 for ECT2 (N=3, P>0.05). Thus, MSC-treatment compensated for 50% reduction in NRCM. Though fetal markers remained, both ECT groups reflected a maturing cardiac phenotype. Funded by NIH R21-HL095980.