A quantitative viability metric for liver transplantation using Resonance Raman Spectroscopy - PROJECT SUMMARY Organ transplantation is a life-saving treatment for end-stage organ disease; however, there is a severe shortage of donor organs whereby only ~36% of wait-listed patients receive a transplant. At the same time, many vital organs that may be transplantable are discarded - some estimates suggest that up to 25% of recovered organs are not ultimately transplanted, and there are additional pools of unrecovered organs that are only marginally damaged. However, because of their uncertain viability and the high cost of an unsuccessful transplant, none of these potential organs are used while transplantation of just a fraction could dramatically reduce the organ shortage. A particularly large target of untapped donor organs are marginally injured warm ischemic organs from Donation after Circulatory Death (DCD). While these organs have been correlated to lower survival rates and increased post-transplant complications, machine perfusion technology holds the promise of reconditioning some of these organs, thereby dramatically increasing availability. However, a critical bottleneck that impacts experimental and clinical advances in reconditioning organs are developing non-objective metrics that can definitively ascertain if an organ is viable prior to transplantation. Clinically, since organ allocation is already severely restricted by time, these criteria need to be defined for each organ rapidly and preferably in real-time. Experimentally, access to flexible platforms would increase the scale and number of researchers that can tackle these difficult problems. In response to this need, we propose to develop a novel imaging platform that will use Resonance Raman Spectroscopy (RRS) to quantify mitochondrial redox state on tissue surfaces/biopsies and mitochondrial breakdown products in the perfusate. Our approach is unique in organ transplantation assessment since: 1) results are obtained in less than 3 minutes and are non-destructive, and 2) offers the flexibility required for diverse organ systems, significantly increasing the impact of the proposed work. While we will target diverse transplantable organs, we focus our initial efforts on liver through execution of two specific aims. We will develop a benchtop RRS device with the capacity to integrate several types of measurements on livers, including biopsies, surface measurements, and perfusate samples. In Specific Aim 1, we will apply and validate the biopsy cell and extendable arm that enables liver biopsies and surface measurements to calculate the ratio of reduced to total mitochondria (defined as Resonance Raman Reduced Mitochondrial Ratio, 3RMR). In Specific Aim 2, we will apply and validate the perfusate cell that is compatible with the same benchtop RRS device to quantify mitochondrial breakdown products in real-time from the perfusate (defined as the Perfusate Viability Index, PVI). In SA1-2, we will define the 3RMR/PVI threshold values that if exceeded will indicate irreversible liver injury, beginning with rigorous studies in rodents before measuring samples from discarded human DCD livers during machine perfusion.
