Cryopreservation of human adult ventricular tissue for the preparation of viable myocardial slices

Abstract

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): REGeRNA Myocardial slices are ultra-thin slices of living adult myocardium which can be cultured. As a multicellular 3-D culture model, myocardial slices offer a novel opportunity to investigate how adult cardiomyocytes (CMs) interact with other cardiac cell types and the extracellular matrix, while providing long-term preservation of CMs cytoarchitecture and electrical phenotype. Additionally, myocardial slices are a new tool in drug discovery by allowing to test chronic treatments, as opposed to isolated CMs which are limited to acute timepoints. Despite their benefits over other cardiac preparations, myocardial slices also have several limitations, of which one is the quality of the slices. The main determinant of myocardial slice quality is the procedure by which the cardiac tissue block is handled. Current methods depend on the preparation of slices directly after tissue excision, therefore limiting the moment when the experiment is performed. We developed a protocol for the cryopreservation of human adult ventricular tissue allowing preparation of viable myocardial slices afterwards. Fresh and cryopreserved cardiac tissue from donor hearts was processed and evaluated for viability, tissue integrity, and inflammatory markers using molecular biology and histological assays. The tissue samples retained viability, biomass, and tissue and vascular integrity following cryopreservation compared to fresh tissue. Additionally, we compared myocardial slices obtained from fresh or cryopreserved tissue and cultured for 24 hours. Histologically, normal cytomorphological features and gap junctions between CMs were preserved in all slices. Comparable retention of tissue viability and structural integrity post cryopreservation (4-6 weeks) and culture (up to 7 days) was observed in cardiac samples from 3 additional donors. In summary, cold storage extends the time-interval between sample collection and slice preparation, allowing for more long-term, complex endpoints. Moreover, efficient banking of cryopreserved cardiac samples from various donors and disease states is critical for regular use of myocardial tissue slices in drug discovery and development. Additional research on the effects of cryopreservation on different cardiac cell types will allow to improve donor organ management to extend the donor pool and increase utilization rate.