Platelet Lysate Hydrogel-based 3D platform for culturing cardiomyocytes derived from human induced pluripotent stem cells

Cardiovascular diseases (CVDs) represent one of the major burdens to the healthcare systems and are the leading cause of death worldwide. Appropriate medication can enable the patients to overcome the disease and improve their quality of life. However, discovery and development of new drugs is a slow and costly process, with cardiotoxicity representing not only one of the most serious causes of attrition during drug development but also a dangerous side effect induced by several medications. Historically the study of the cardiac tissue and the development of new treatments have been hindered by the heart’s lack of accessibility and poor regenerative capacity. The advent of hiPSC technologies and the possibility to derive cardiac cells from patients and healthy donors have provided an unlimited source of cardiomyocytes that can be used both in research and in clinical settings. Nevertheless, the functional immaturity of hPSC-derived cardiomyocytes (hPSC-CMs) greatly hinders their use in several applications, such as cardiotoxicity prediction, cell replacement therapies and the study of cardiac pathophysiology. Different approaches have been investigated to enhance hPSC-CMs maturity, including to provide the cells with a 3D microenvironment that mimics the complexity of the cardiac tissue. However, most of the materials employed in cardiac engineering fail to fully recapitulate favourable microenvironments for cardiac tissue formation and maturation. The aim of this study was to investigate for the first time the suitability of human methacryloyl platelet lysate (PLMA) hydrogels to support the 3D culture and maturation of hiPSC-CMs. PLMA is a photopolymerizable biomaterial derived from human blood with unique structural and biochemical properties. Here, beating hiPSC cardiomyocyte aggregates, obtained by a novel 3D differentiation protocol, were embedded in PLMA hydrogels and maintained in culture for 15 days. hiPSC-CM aggregates remained alive and preserved their contractile activity in the hydrogel, moreover, they displayed good cell-matrix interaction, evidenced by cell sprouting within the matrix. PLMA hydrogels proved to be a favourable 3D support for hiPSC-CMs, able to support cell viability, provide proper anchorage to cardiomyocytes and sustain the repetitive mechanical stretch induced by their contractions. Over time in culture, cells from the aggregates migrated and invaded the matrix. Immunocytochemistry analysis revealed that in the sprouting area collagen I and fibronectin were present, along with a small percentage of cTnT+ cells. These findings suggest that hiPSC-CMs effectively integrated with the biomaterial. PLMA hydrogels display exceptional mechanical and biochemical properties that are expected not only to sustain cardiomyocyte culture and maintenance, as it was demonstrated here, but also to favour cardiac maturation. However, much additional work is required to elucidate the impact of PLMA encapsulation on hiPSC-CM maturation. Its human origin, ease to use and cost-effectiveness make PLMA a suitable candidate for applications that go far beyond cell culture. Being possible to derive PLMA from patients own blood, this promising biomaterial could be used in future applications in conjugation with hiPSC-CMs to obtain patient-specific cardiac engineered tissues suitable not only for cardiotoxicity assessment but also for regenerative strategies and disease modelling.