EFFECTS OF INSIDE-OUT SUBMITOCHONDRIAL PARTICLES (IO-SMPS) ON MITOCHONDRIA ISOLATED FROM A PORCINE EX VIVO MODEL OF DONATION AFTER CARDIOCIRCULATORY DEATH (DCD) HEART

When it comes to heart transplantation, donation after brain death (DBD) has become the standard of care as this method is supported by many advantages, mainly due to the possibility to easily assess donor heart function before retrieval and sensibly shorten the detrimental period of warm ischemia. Lately, however, the ever-increasing number of patients in waitlist for heart transplantation has pushed the interest of researchers to find new methods to increase the donor pool [1], including heart donation after cardiocirculatory death (DCD). The latter, nonetheless, shows several disadvantages including a longer period of warm ischemia, long-term outcomes uncertainty, and lack of standardized reliable biomarkers and physiological parameters predictive of function and transplantability of DCD hearts [2]. One of the earliest cardiomyocytes degenerations starting after cardiac death is borne by mitochondria that are involved in some distinct types of cell death. Therefore, studying such events may help better understanding the physiological processes underlying DCD heart transplantability, eventually leading to definition of useful biomarkers. To achieve this, the focus of this work was the F₁Fₒ-ATPase complex, considered as the leading candidate responsible for the opening of a channel though the inner membrane called mitochondrial permeability transition pore (mPTP) when the natural cofactor (Mg²+) is replaced with the physio- pathological cofactor (Ca²+) [3]. Specifically, trying to preserve mitochondrial bioener getics and integrity, we assessed the efficacy of IO-SMPs (inside-out submitochondrial particles) obtained by swine hearts isolated by stepwise centrifugation from mitochondria [4], on an ex-vivo porcine model of DCD heart (20 min of no touch after cardiac arrest followed by 2h of warm ischemia). We evaluated the effect of IO-SMPs on Oxidative Phosphorylation and their influence on mitochondria calcium retention capacity (CRC), an indirect index of mPTP opening, as already highlighted in other studies. Studies are currently ongoing, but the preliminary results show that IO-SMPs are capable of delaying the mPTP opening when swine heart mitochondria are exposed to Ca²+. Overall, this study represents a first step towards an in-depth characterization of the physiological process activated by a prolonged warm ischemia within mitochondria, and investigates the potential beneficial effects of IO-SMPs, that may be applicable to all DCD solid organs