Functional Assessment and Extended Culture of Human Pediatric Cardiac Tissue Slices for Preclinical Testing

Background: Living human myocardial slices preserve native tissue architecture, but their application to pediatric cardiac physiology or prolonged functional testing remains limited. We adapted a passive culture method for small surgical myocardial specimens obtained from patients with congenital heart disease (CHD). Methods: Atrial and ventricular specimens were obtained from 41 cardiac surgery patients (7.7{+/-}11.1 years; 1 day-49 years). Myocardial tissue was sectioned into slices and studied acutely, or maintained under free floating, rocking cell culture conditions without electrical or mechanical stimulation. Calcium transients were recorded in response to external pacing (0.2-2 Hz) at baseline, and after isoproterenol or norepinephrine exposure. Selected preparations underwent viability, histological, and gene expression analyses. Results: Pacing evoked calcium transients were recorded from all four cardiac chambers, exhibiting expected frequency-dependent shortening. Mean interslice and intraslice coefficients of variation were 11.1% and 7.6%. Viability was 85.8 {+/-} 5.6% post-slicing and 78.8 {+/-} 5.0% after 3-5 hours. Calcium transients remained detectable through 178 days in atrial and 119 days in ventricular slices. Calcium transient durations were relatively stable during extended culture. Beta-adrenergic agonists shortened calcium transient durations (isoproterenol: 32% atrial, 25% ventricular at 0.3 Hz); responses to isoproterenol persisted to approximately 120 days in selected atrial slices and 60 days in ventricular slices. Selected histological features were preserved, although some extracellular matrix and apoptosis related transcripts changed. Conclusions: Small surgical specimens support repeated physiological measurements and pharmacological testing during extended passive culture, providing a platform for human developmental and disease-specific cardiac research.