Evaluation of Cardioplegic Solutions for Preserving Cardiac Cells in Isolated Rat Heart Assays

Introduction Cardioplegic solutions are used to stop myocardial contraction during heart surgery. Their primary goal is to reduce myocardial oxygen demand by creating electro-mechanical quiescence and cooling the heart, which reduces ischemic effects. This helps prevent degenerative changes, lowers the metabolic demands of the cardiac muscle, and prevents apoptosis and cell death in cardiac myocytes. [1]. Various alterations in molecular processes within cells can be used to define ischemic injury in heart. BCL-2 family proteins are important modulators of mitochondrial apoptosis, either promoting or inhibiting cell death [2]. Cell transformation, differentiation, and proliferation have all been linked to FOS proteins [3]. By interacting with various proteins, the BNIP2 gene protects cells from exogenously induced cell death [4]. HIF1α acts as a master regulator of the cellular and systemic homeostatic response to hypoxia [5]. Aim To evaluate three different cardioplegic solutions in immature rat heart tissues, we measured the expression of genes related to the cell cycle, proliferation, apoptosis resistance, and hypoxia response. Methods Animals were sacrificed, and the heart was excised via median sternotomy, transferred to cold perfusion buffer, and within 5 minutes, the heart was mounted on a Langendorff system. Cardioplegia was administered using St. Thomas (CP1), Custodiol HTK (CP2), or del Nido (CP3) solutions, with re-plegia intervals of 30 minutes (CP1), 90 minutes (CP3), or a single dose (CP2). The control group was regarded as non-CP tissue (CP0). As a positive control, fully perfused heart tissue was used (K-PRF). Ventricular biopsies were homogenized in liquid nitrogen in order to extract total RNA. RNA was reverse-transcribed and analyzed for gene expression using TaqMan assays. Data were normalized to GAPDH gene and analyzed with GraphPad Prism 9. Results CP3-treated tissue had an average 50% lower BAX/BCL2 ratio than CP1 and CP2 tissue, however, these changes were not statistically significant. Following CP treatment, HIF1α gene was significantly overexpressed CP3 group compared to CP0, CP1, and CP2 groups (P<0.01). In all cases, FOS expression was significantly increased compared to the CP0. After 2 and 4 h of incubation with CP3 solution, FOS gene expression remained substantially higher compared to CP1 (P<0.05) and CP2 (P<0.05). Similar results were observed in BNIP2 gene expression. Based on gene expression, CP3 treated cardiac tissue was comparable to K-PRF heart tissue in all timestamps. Conclusions The CP3 solution demonstrated the best cell-protective properties, comparable to heart perfusion. However, further research is needed to evaluate the electrophysiological and metabolic changes in heart tissue.