Hi1a, an ASIC1a Inhibitor, Significantly Improves the Tolerance of Donor Allografts to Ischaemia in a Rodent Model of DCD Heart Transplantation

Purpose ASIC1a has been demonstrated to play a critical role in acidosis-induced neuronal injury following cerebral ischaemia, however its role in the heart is poorly understood. Given similar pathophysiology, this project sought to investigate the cardioprotective effects of Hi1a, a novel ASIC1a inhibitor, derived from funnel web spider venom, in the context of donor allograft preservation. Methods Studies utilized a working rodent model of DCD heart preservation. Following asphyxia, hearts were retrieved from male Wistar rats (350-425g) after a 10 min warm ischaemic time (WIT) followed by 2 min stand-off, mimicking a clinical DCD withdrawal. Hearts were then flushed with either Celsior alone, Celsior + Hi1a (CHi1a), or Celsior + Hi1a, GTN and EPO (n=7/group). Allografts were reperfused ex-vivo in resting Langendorff mode for 30 min, prior to assessment of cardiac function in working mode for 30 min. Results Recovery of aortic flow (AF), pulse pressure (PP), and cardiac output (CO) was significantly improved in the CHi1a group and CHi1a + GTN, EPO group when compared to Celsior alone (p<0.006 and p<0.0001 respectively, for all parameters). Furthermore, LDH measurements from coronary effluent during working reperfusion demonstrated that allografts treated with CHi1a + GTN, EPO had a significantly reduced LDH level when compared to Celsior alone (p=0.008). In fact, the LDH level at 30 mins of working reperfusion in this group was comparable to a heart at baseline, prior to any ischaemic insult. Conclusion Supplementation of Celsior with either Hi1a as a single supplement, or in combination with GTN and EPO significantly improved cardiac allograft function following warm ischaemia. Both the functional and biochemical results demonstrate profound cardioprotective effects of Hi1a. These results suggest the potential of Hi1a, or other ASIC1a inhibitors to increase the tolerable WIT during DCD retrieval, leading to further increases in heart transplant volume. ASIC1a has been demonstrated to play a critical role in acidosis-induced neuronal injury following cerebral ischaemia, however its role in the heart is poorly understood. Given similar pathophysiology, this project sought to investigate the cardioprotective effects of Hi1a, a novel ASIC1a inhibitor, derived from funnel web spider venom, in the context of donor allograft preservation. Studies utilized a working rodent model of DCD heart preservation. Following asphyxia, hearts were retrieved from male Wistar rats (350-425g) after a 10 min warm ischaemic time (WIT) followed by 2 min stand-off, mimicking a clinical DCD withdrawal. Hearts were then flushed with either Celsior alone, Celsior + Hi1a (CHi1a), or Celsior + Hi1a, GTN and EPO (n=7/group). Allografts were reperfused ex-vivo in resting Langendorff mode for 30 min, prior to assessment of cardiac function in working mode for 30 min. Recovery of aortic flow (AF), pulse pressure (PP), and cardiac output (CO) was significantly improved in the CHi1a group and CHi1a + GTN, EPO group when compared to Celsior alone (p<0.006 and p<0.0001 respectively, for all parameters). Furthermore, LDH measurements from coronary effluent during working reperfusion demonstrated that allografts treated with CHi1a + GTN, EPO had a significantly reduced LDH level when compared to Celsior alone (p=0.008). In fact, the LDH level at 30 mins of working reperfusion in this group was comparable to a heart at baseline, prior to any ischaemic insult. Supplementation of Celsior with either Hi1a as a single supplement, or in combination with GTN and EPO significantly improved cardiac allograft function following warm ischaemia. Both the functional and biochemical results demonstrate profound cardioprotective effects of Hi1a. These results suggest the potential of Hi1a, or other ASIC1a inhibitors to increase the tolerable WIT during DCD retrieval, leading to further increases in heart transplant volume.