New potent conditioning agent to improve cardiac function and reduce injury in a preclinical model of donation after circulatory death

Organ donation after circulatory death (DCD) is considered a potential solution to address limited availability of suitable organs such as lungs, kidneys and liver, but due a period of prolonged warm ischemia and the risk of tissue injury, the heart is systematically discarded for transplantation. Our group was the first to demonstrate that Celastrol, a triterpenoid C29H38O4 with HSP90 modulating activity alleviates ischemia/reperfusion (I/R)-induced cardiac cell death through activation of heat shock response and antioxidant response, and preserves myocardial viability and heart function in ex vivo and in vivo models. A synthetic Celastrol-like compound exhibiting superior infarct sparing effects will be evaluated in a pre-clinical model of DCD heart mimicking the clinical set up of induced hypoxic cardiac death by hemodynamic collapse, followed by conditioning in an ex vivo heart perfusion (EVHP) system. Male Lewis rats were anesthetized, ventilated, heparinized and right carotid was cannulated for blood pressure measurements. DCD protocol was initiated by discontinuation of ventilation, and circulatory death was declared when systolic blood pressure was <30 mmHg. Following 15 minutes of global warm ischemia, cardioplegia was perfused through the carotid catheter during five minutes at constant pressure (60 mmHg) and 37°C. Heart was rapidly harvested, then mounted in an ex vivo Langendorff EVHP system with constant pressure for 60 min of conditioning. Test compound (10-8M) or vehicle (DMSO) were infused in the cardioplegia and during the first 10 minutes of reperfusion in the EVHP. Hemodynamics were precisely recorded using a LV balloon and pressure transducer. Results show that treatment with the compound significantly preserves LV contractility (maximum +dP/dt) and relaxation (minimum -dP/dt), along with generated pressure compared to vehicle treated DCD hearts, see Figure. Treatment abrogates ischemic injury as demonstrated by a significant reduction of infarct size (TTC staining of heart sections) of 7+/-3% vs 19+/-4% (P=0.03), Troponin T content in the coronary effluent at 60 min of 325+/-132 vs 520+/-201 ng/L/g of tissue (P ns) and decreased mRNA expression ratio of Bax/Bcl-2 (p=0.05). With the recent identification of several molecular targets activating survival signaling pathways, along with technological development of ex vivo human organ perfusion systems, there is a clear opportunity to use pharmaco-conditioning to improve organ repair and function. Cardiac conditioning using EVHP system might allow the use of DCD hearts in selected cases, improving availability for transplantation.