Evaluation of cardioplegic solutions for preserving cardiac cells in isolated rat heart assays

Introduction. Cardioplegic solutions are employed during heart surgery to halt myocardial contraction. Their main purpose is to minimize myocardial oxygen demand by inducing electromechanical quiescence and cooling of the heart, thereby reducing ischemic effects. This process helps prevent degenerative changes, decreases the metabolic demands of the cardiac muscle, and protects cardiac myocytes from apoptosis and cell death [1]. Ischemic injury in the heart can be characterized by various molecular alterations within cells. BCL-2 family proteins play a crucial role in regulating mitochondrial apoptosis, either facilitating or preventing cell death [2]. In addition, FOS proteins have been associated with cell transformation, differentiation, proliferation [3]. The BNIP2 gene interacts with various proteins to protect cells from externally induced cell death [4]. Meanwhile, HIF1α serves as a key regulator of cellular and systemic homeostasis in response to hypoxia [5]. Aim. To assess the effects of three different cardioplegic solutions on immature rat heart tissues, we analyzed gene expression associated with the cell cycle, proliferation, apoptosis resistance, and hypoxia response. Methods. The animals were sacrificed, and the heart was removed through a median sternotomy, then transferred to a cold perfusion buffer. Within 5 min, the heart was mounted on a Langendorff system and perfused retrogradely. Cardioplegia was administered using St. Thomas (CP1), Custodiol HTK (CP2), or del Nido (CP3) solutions, with re-plegia intervals of 30 min (CP1), 90 min (CP3), or a single dose (CP2). As a positive control, fully perfused heart tissue was used (K-PRF). Ventricular biopsies were homogenized in liquid nitrogen to extract total RNA, which was then reverse-transcribed and analyzed for gene expression using TaqMan assays. 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, CP1, and CP2 groups (P<0.05). In all cases, FOS expression was significantly decreased compared to the K-PRF after CP1 and CP2 treatment. 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 exhibited the most effective cell-protective properties, comparable to heart perfusion. However, further studies are required to assess the electrophysiological and metabolic changes in heart tissue.