Preservation of contractile characteristics of human myocardium in multi-day cell culture.

Functional studies of different human cell types have been successfully conducted under in vitro conditions. Despite many efforts, it has not been possible to develop a human myocardial preparation in which contractile function can be studied over several days. We hypothesize that by mimicking the in vivo situation in an in vitro environment we can preserve viability and function of human myocardial preparations over several days. From explanted hearts of patients undergoing cardiac transplantation, multicellular preparations were dissected and mounted in a sterile muscle chamber. Muscles were stimulated at 0.5 or 1 Hz at 1.75 mmol/l Ca(2+), a pH of 7.4 and at 37 degrees C, and kept contracting isometrically for 2-6 days. This study shows for the first time that contractile function of human myocardial tissue can be preserved over several days; active force development had not significantly changed after 48 h (10.6+/-1.2 at t=0 v 11.4+/-2.8 mN/mm(2)at t=48, n=10), nor had diastolic force (1.0+/-0.1 v 0.9+/-0.1 mN/mm(2)). After at least 48 h, the contractile response to stimulation with 1 micromol/l isoproterenol was clearly present: developed force increased to 631+/-146% of control values, while half-relaxation time declined to 57+/-6% (n=7). In addition, both pharmacological responses and regulatory physiological behavior, such as post-rest potentiation and force-frequency relationships, are preserved. This technique allows the study of the regulation of contractile function of human myocardium in vitro and may be used to link changes in protein expression to consequent changes in myocardial contraction.