Allograft Viability Research Articles

5. Viability and Functional Outcomes of Limb Allografts Following Sub-normothermic Plasma and Red Blood Cell Based Perfusion

5. Viability and Functional Outcomes of Limb Allografts Following Sub-normothermic Plasma and Red Blood Cell Based Perfusion

Design of a Multiparametric Perfusion Bioreactor System for Evaluating Sub-Normothermic Preservation of Rat Abdominal Wall Vascularized Composite Allografts.

Static cold storage (SCS), the current clinical gold standard for organ preservation, provides surgeons with a limited window of time between procurement and transplantation. In vascularized composite allotransplantation (VCA), this time limitation prevents many viable allografts from being designated to the best-matched recipients. Machine perfusion (MP) systems hold significant promise for extending and improving organ preservation. Most of the prior MP systems for VCA have been built and tested for large animal models. However, small animal models are beneficial for high-throughput biomolecular investigations. This study describes the design and development of a multiparametric bioreactor with a circuit customized to perfuse rat abdominal wall VCAs. To demonstrate its concept and functionality, this bioreactor system was employed in a small-scale demonstrative study in which biomolecular metrics pertaining to graft viability were evaluated non-invasively and in real time. We additionally report a low incidence of cell death from ischemic necrosis as well as minimal interstitial edema in machine perfused grafts. After up to 12 h of continuous perfusion, grafts were shown to survive transplantation and reperfusion, successfully integrating with recipient tissues and vasculature. Our multiparametric bioreactor system for rat abdominal wall VCA provides an advanced framework to test novel techniques to enhance normothermic and sub-normothermic VCA preservations in small animal models.

Comparison of the effects of normothermic machine perfusion and cold storage preservation on porcine intestinal allograft regenerative potential and viability

Intestinal transplantation (IT) is the final treatment option for intestinal failure. Static cold storage (CS) is the standard preservation method used for intestinal allografts. However, CS and subsequent transplantation induce ischemia-reperfusion injury (IRI). Severe IRI impairs epithelial barrier function, including loss of intestinal stem cells (ISC), critical to epithelial regeneration. Normothermic machine perfusion (NMP) preservation of kidney and liver allografts minimizes CS-associated IRI; however, it has not been used clinically for IT. We hypothesized that intestine NMP would induce less epithelial injury and better protect the intestine’s regenerative ability when compared with CS. Full-length porcine jejunum and ileum were procured, stored at 4 °C, or perfused at 34 °C for 6 hours (T6), and transplanted. Histology was assessed following procurement (T0), T6, and 1 hour after reperfusion. Real-time quantitative reverse transcription polymerase chain reaction, immunofluorescence, and crypt culture measured ISC viability and proliferative potential. A greater number of NMP-preserved intestine recipients survived posttransplant, which correlated with significantly decreased tissue injury following 1-hour reperfusion in NMP compared with CS samples. Additionally, ISC gene expression, spheroid area, and cellular proliferation were significantly increased in NMP-T6 compared with CS-T6 intestine. NMP appears to reduce IRI and improve graft regeneration with improved ISC viability and proliferation.

45: Comparison of the Effects of Normothermic Machine Perfusion and Cold Storage Preservation on Porcine Intestinal Allograft Regenerative Potential and Viability

45: Comparison of the Effects of Normothermic Machine Perfusion and Cold Storage Preservation on Porcine Intestinal Allograft Regenerative Potential and Viability

Orthopaedic Surgery.

Yazdi, Allen; Dib, Aseel BS; Elphingstone, Joseph; Momaya, Amit MD; Brabston, Eugene W Author Information

A New Osteogenic Membrane to Enhance Bone Healing: At the Crossroads between the Periosteum, the Induced Membrane, and the Diamond Concept

The lack of viability of massive bone allografts for critical-size bone defect treatment remains a challenge in orthopedic surgery. The literature has reviewed the advantages of a multi-combined treatment with the synergy of an osteoconductive extracellular matrix (ECM), osteogenic stem cells, and growth factors (GFs). Questions are still open about the need for ECM components, the influence of the decellularization process on the latter, the related potential loss of function, and the necessity of using pre-differentiated cells. In order to fill in this gap, a bone allograft surrounded by an osteogenic membrane made of a decellularized collagen matrix from human fascia lata and seeded with periosteal mesenchymal stem cells (PMSCs) was analyzed in terms of de-/recellularization, osteogenic properties, PMSC self-differentiation, and angiogenic potential. While the decellularization processes altered the ECM content differently, the main GF content was decreased in soft tissues but relatively increased in hard bone tissues. The spontaneous osteogenic differentiation was necessarily obtained through contact with a mineralized bone matrix. Trying to deepen the knowledge on the complex matrix-cell interplay could further propel these tissue engineering concepts and lead us to provide the biological elements that allow bone integration in vivo.

Untargeted metabolomics of perfusate and their association with hypothermic machine perfusion and allograft failure

Although hypothermic machine perfusion (HMP) is associated with improved kidney graft viability and function, the underlying biological mechanisms are unknown. Untargeted metabolomic profiling may identify potential metabolites and pathways that can help assess allograft viability and contribute to organ preservation. Therefore, in this multicenter study, we measured all detectable metabolites in perfusate collected at the beginning and end of deceased-donor kidney perfusion and evaluated their associations with graft failure. In our cohort of 190 kidney transplants, 33 (17%) had death-censored graft failure over a median follow-up of 5.0 years (IQR 3.0-6.1 years). We identified 553 known metabolites in perfusate and characterized their experimental and biological consistency through duplicate samples and unsupervised clustering. After perfusion-time adjustment and false discovery correction, six metabolites in post-HMP perfusate were significantly associated with death-censored graft failure, including alpha-ketoglutarate, 3-carboxy-4-methyl-5-propyl-2-furanpropanoate, 1-carboxyethylphenylalanine, and three glycerol-phosphatidylcholines. All six metabolites were associated with an increased risk of graft failure (Hazard Ratio per median absolute deviation range 1.04-1.45). Four of six metabolites also demonstrated significant interaction with donation after cardiac death with notably greater risk in the donation after cardiac death group (Hazard Ratios up to 1.69). Discarded kidneys did not have significantly different levels of any death-censored graft failure-associated metabolites. On interrogation of pathway analysis, production of reactive oxygen species and increased metabolism of fatty acids were upregulated in kidneys that subsequently developed death-censored graft failure. Thus, further understanding the role of these metabolites may inform the HMP process and help improve the objective evaluation of allograft offers, thereby reducing the discard of potentially viable organs.

Topographical Characterization of the Young, Healthy Human Femoral Medial Condyle.

The medial femoral condyle of the knee exhibits some of the highest incidences of chondral degeneration. However, a dearth of healthy human tissues has rendered it difficult to ascertain whether cartilage in this compartment possesses properties that predispose it to injuries. Assessment of young, healthy tissue would be most representative of the tissue's intrinsic properties. This work examined the topographical differences in tribological, tensile, and compressive properties of young (n = 5, 26.2 ± 5.6 years old), healthy, human medial femoral condyles, obtained from viable allograft specimens. Corresponding to clinical incidences of pathology, it was hypothesized that the lowest mechanical properties would be found in the posterior region of the medial condyle, and that tissue composition would correspond to the established structure-function relationships of cartilage. Young's modulus, ultimate tensile strength, aggregate modulus, and shear modulus in the posterior region were 1.0-, 2.8-, 1.1-, and 1.0-fold less than the values in the anterior region, respectively. Surprisingly, although glycosaminoglycan content is thought to correlate with compressive properties, in this study, the aggregate and shear moduli correlated more robustly to the amount of pyridinoline crosslinks per collagen. Also, the coefficient of friction was anisotropic and ranged 0.22-0.26 throughout the condyle. This work showed that the posteromedial condyle displays lower tensile and compressive properties, which correlate to collagen crosslinks and may play a role in this region's predisposition to injuries. Furthermore, new structure-function relationships may need to be developed to account for the role of collagen crosslinks in compressive properties.

Hyperspectral Imaging for Viability Assessment of Human Liver Allografts During Normothermic Machine Perfusion.

Twenty-five deceased donor liver allografts were included in the study. During NMP, graft viability was assessed conventionally and by means of HSI. Images of liver parenchyma were acquired at 1, 2, and 4 h of NMP, and subsequently analyzed using a specialized HSI acquisition software to compute oxygen saturation, tissue hemoglobin index, near-infrared perfusion index, and tissue water index. To analyze the association between HSI parameters and perfusate lactate as well as perfusate pH, we performed simple linear regression analysis. Perfusate lactate at 1, 2, and 4 h NMP was 1.5 [0.3-8.1], 0.9 [0.3-2.8], and 0.9 [0.1-2.2] mmol/L. Perfusate pH at 1, 2, and 4 h NMP was 7.329 [7.013-7.510], 7.318 [7.081-7.472], and 7.265 [6.967-7.462], respectively. Oxygen saturation predicted perfusate lactate at 1 and 2 h NMP (R2 = 0.1577, P = 0.0493; R2 = 0.1831, P = 0.0329; respectively). Tissue hemoglobin index predicted perfusate lactate at 1, 2, and 4 h NMP (R2 = 0.1916, P = 0.0286; R2 = 0.2900, P = 0.0055; R2 = 0.2453, P = 0.0139; respectively). HSI may serve as a noninvasive tool for viability assessment during NMP. Further evaluation and validation of HSI parameters are warranted in larger sample sizes.

P11.02: Application of Ex-vivo Normothermic Machine Perfusion To Assess Renal Allograft Viability Following Renal Vein Thrombosis

Background: Ex-vivo Normothermic Machine perfusion (NMP) has been shown to improve transplantation outcomes and assess the viability of discarded grafts. We report an application of NMP in assessing renal allograft viability in a case of renal vein thrombosis (RVT) following deceased renal transplantation in the immediate postoperative period. Method: A 44-year-old female patient of unknown cause chronic kidney disease, on maintenance haemodialysis since 2018, underwent a deceased donor renal transplant from a young adult male donor after negative virtual crossmatch with CIT of 7 hrs 8 min. She had a history of fistula failure on multiple occasions and one abortion; her pro-coagulant workup was negative. She was on peritoneal dialysis for the past year, and she had multiple anti-HLA antibody specificities in class I and II loci (highest MFI 9709). She received Induction ATG, tacrolimus, mycophenolate, and steroids. The surgical procedure required reconstruction of the right renal vein. Allograft function was immediate and good with nadir creatinine 1.0mg/ml on postoperative day 6. On day 7, she had rapid onset anuria. Ultrasonogram showed clots in the graft pelvis with flow reversal, and CT angiogram showed RVT. On surgical re-exploration, the graft was congested, and the renal vein had an occlusive thrombus. After explantation and thrombectomy, the graft was placed on the Organ AssistTM using a red cell-based perfusate. It was perfused for six hours to check for graft viability on which there was the restoration of blood flow as evidenced by improving vascular resistance (peak 3mmHg/ml/min dropping to 1.3mmHg/ml/min) and blood flow (20ml/min rising to 220ml/min) and stabilization of lactate levels with a good macroscopic appearance. However, there was persistent haemorrhagic urine output despite an adequate and steady increase in renal blood flow. Result: Despite demonstrating viability on NMP, the allograft could not be re-implanted due to haemorrhagic urine output on NMP, given the potential for bleeding and the hemodynamic instability in the recipient. The recipient was discharged on day 18 on dialysis. The allograft nephrectomy specimen showed isolated vascular acute T cell-mediated rejection- C4d negative with superimposed venous thrombosis. Conclusion: EVNMP can help decision making in complex situations where graft viability assessment is not readily apparent. Received Funding from PGIMER Chandigarh.

Circulating Metabolites in Relation to the Kidney Allograft Function in Posttransplant Patients.

End-stage kidney disease is preferably treated by kidney transplantation. The suboptimal function of the allograft often results in misbalances in kidney-controlled processes and requires long-term monitoring of allograft function and viability. As the kidneys are organs with a very high metabolomic rate, a metabolomics approach is suitable to describe systematic changes in post-transplant patients and has great potential for monitoring allograft function, which has not been described yet. In this study, we used blood plasma samples from 55 patients after primary kidney transplantation identically treated with immunosuppressants with follow-up 50 months in the mean after surgery and evaluated relative levels of basal plasma metabolites detectable by NMR spectroscopy. We were looking for the correlations between circulating metabolites levels and allograft performance and allograft rejection features. Our results imply a quantitative relationship between restricted renal function, insufficient hydroxylation of phenylalanine to tyrosine, lowered renal glutamine utilization, shifted nitrogen balance, and other alterations that are not related exclusively to the metabolism of the kidney. No link between allograft function and energy metabolism can be concluded, as no changes were found for glucose, glycolytic intermediates, and 3-hydroxybutyrate as a ketone body representative. The observed changes are to be seen as a superposition of changes in the comprehensive inter-organ metabolic exchange, when the restricted function of one organ may induce compensatory effects or cause secondary alterations. Particular differences in plasma metabolite levels in patients with acute cellular and antibody-mediated allograft rejection were considered rather to be related to the loss of kidney function than to the molecular mechanism of graft rejection since they largely follow the alterations observed by restricted allograft function. In the end, we showed using a simple mathematical model, multilinear regression, that the basal plasmatic metabolites correlated with allograft function expressed by the level of glomerular filtration rate (with creatinine: p-value = 4.0 × 10−26 and r = 0.94, without creatinine: p-value = 3.2 × 10−22 and r = 0.91) make the noninvasive estimation of the allograft function feasible.

93. The Effects of Subnormothermic Plasma and Red Blood Cell Based Perfusion on the Function and Viability of Limb Allografts

Purpose: Vascularized composite allotranplantation (VCA) is an evolving area of modern transplantation medicine to reconstruct composite tissue defects such as abdominal wall, face, and limb. One of the challenges in VCA is the narrow window of tolerable ischemia time which limits the number of available donors and imposes a single center transplantation approach. Current standard of care, static cold storage, is only effective for short periods and may result in severe tissue damage and acute rejection when prolonged. Ex-situ perfusion has the potential to overcome these challenges by extending allowable pre-transplantation ischemia time. However, optimum perfusate composition, preservation temperature, and hemodynamic parameters of perfusion are still debated. Over the past decade, the benefits of addition of fresh plasma in hemorrhagic shock resuscitation and attenuation of subsequent reperfusion injury have been recognized. Whether these observations are due to high or low molecular weight (HMW and LMW, respectively) plasma proteins require further investigation. This study investigated the effects of the addition of plasma on the viability of perfused limb allografts with prolonged ischemia time. Methods: All limb transplantations were performed orthotopically between male Lewis rats (200-250 g). In group 1, amputated limbs were transplanted immediately to determine the effects of surgical trauma. In group 2, amputated limbs were preserved at 4°C simulating the clinical standard of care. In other groups, amputated limbs were perfused for 6 hours at 20° to 22°C using one of the following perfusates groups and transplanted to another recipient (in less than 90 minutes): RBC only (G3), RBC + whole plasma (G4), RBC + LMW plasma (G5), RBC + HMW plasma (G6). At 3 months post-transplantation, surviving recipients had end-point assessment using electromyography where compound muscle action potentials (CMAP) and extensor digitorum longus (EDL) muscle force generation were compared to contralateral healthy limb. Muscle and nerve histology samples were collected at the end of EMG testing. Results: Recipients in the group perfused with RBC and HMW plasma proteins had severe reperfusion injury and did not survive beyond 3 days. Among surviving recipients, the addition of whole plasma did not appear to improve amplitude and latency on gastrocnemius and EDL muscles compared to immediately transplanted limbs. Groups perfused with RBC only and RBC with LMW plasma demonstrated excellent amplitude and latencies on both muscle groups, with no significant difference compared to immediately transplanted limbs (p>0.05). The EDL muscle in these groups also generated similar tetanic and twitch forces compared to the immediate transplantation group (p>0.05). Conclusion: Ex-situ perfusion at 20° to 22°C for 6 hours using RBC and LMW plasma appears to protect both fast and slow twitch muscles, and improve axonal regeneration and myelin sheath thickness to a degree comparable with the immediately transplanted group.

The Viable Disc Tissue Allograft Supplementation (VAST) Randomized Controlled Trial in Patients with Chronic Discogenic Low Back Pain: Correlating Age with Clinical Outcome

The Viable Disc Tissue Allograft Supplementation (VAST) Randomized Controlled Trial in Patients with Chronic Discogenic Low Back Pain: Correlating Age with Clinical Outcome

Viable Disc Tissue Allograft Supplementation in the Treatment of Painful Degenerated Intervertebral Discs: The One Year Results of a Randomized Control Trial

Viable Disc Tissue Allograft Supplementation in the Treatment of Painful Degenerated Intervertebral Discs: The One Year Results of a Randomized Control Trial

A Retrospective Analysis of Clinical Use and Outcomes Using Viable Placental Membrane Allografts in Chronic Wounds

Viable placental membrane (vPM) has been shown to decrease time to healing, adverse wound events, and wound-related infections. Wound research exclusion criteria commonly exclude wound types other than diabetic foot ulcers and venous leg ulcers (VLUs), comorbidities including peripheral arterial disease (PAD) and uncontrolled diabetes mellitus (DM), and wounds with exposed bone or tendon. This retrospective research study evaluated the clinical use and outcomes of the vPM with living mesenchymal stem cells used in chronic wound management in the community hospital outpatient department setting with the goal of comparing real-world use and outcomes of the product with use and outcomes described in the chronic wound literature. A retrospective analysis on vPM treatments at a Wisconsin academic health system's community hospitals. Participants included all patients who received vPM therapy between July 1, 2016, and August 21, 2019. A total of 89 patients received vPM treatment during the study period (mean age, 70 years; 69% male [n = 61], 31% female [n = 28]). Wound types were 54% diabetic or neuropathic foot ulcers (n = 48), 17% VLUs (n = 15), 7% pressure injuries (n = 6), and 22% atypical wounds (n = 20). The average wound duration prior to vPM initiation was 104 days. Average wound size at presentation was 6.9 cm2. Of study participants 54% had PAD (n = 48), 63% had DM (n = 56), 33.7% had DM and PAD (n = 30), and 17% had exposed bone or tendon (n = 15). Average adjusted time to healing after initiation of vPM was 81.2 days. The percentage of wounds healed 12 weeks after initiation of vPM treatment was 57%. Effectiveness of vPM observed in controlled trials also was observed in this real-world study on vPM for multiple wound types, patients with comorbidities including PAD and uncontrolled DM, and wounds with exposed bone or tendon. Results of this study were not statistically different from those reported in the literature. More randomized controlled trials are needed to explore the efficacy of vPM on patient presentations common to wound healing centers.

Osteochondral allograft transplantation in the knee, after prolonged fresh storage at 37 °C. Determination of viability of human cartilage allografts, indications, technique, and evidence. Follow up 10 years

BackgroundOsteochondral allografts (OA) kept fresh for a long time, are presented as a viable option for the treatment of large chondral and osteochondral lesions. GoalsChondrocyte viability decreases substantially when allografts are stored for more than 15 days. The objective of this work is to validate the viability and clinical and functional results of OA transplantation stored at 37 °C in a cell culture medium, applied in cartilage defects of the knee, defining the means and limits of allograft storage, among 15 and 28 days after extraction. Patients and MethodThis study presents the results of 20 consecutive patients, operated between 2003 and 2019, who underwent a fresh-preserved osteochondral allograft, implanted on cartilage defects of the femoral condyle and patella. The minimum follow-up time was 10 years and the maximum 17. The mean age of the patients was 29 (14−44).The clinical control data were collected using IKDC, International Knee Documentation Committee (knee-specific), KOOS, Knee injury and Osteoarthritis Outcome Score protocols. Likewise, the degree of satisfaction was evaluated. Cartilage control was performed using the International Cartilage Repair Society Score (ICRS) and the Oswestry Arthroscopy Score (OAS). Radiological evaluations were performed using MRI and helical CT. ResultsStatistically significant improvements, P < .0001, were observed for the (IKDC) (30–65); the 5 components of the KOOS protocol, (pain, 66–85); Specific symptoms, (72–82); Activities of daily living, 74–91; Sports and recreational function, from 37 to 70, related to the knee, Quality of life, (25–60). Regarding the degree of satisfaction, 89% answered being satisfied or very satisfied.The ICRS and OAS results, all patients went from grade IV to grade I, except for one who is currently in IV.The incorporation of the graft in the recipient area occurred at three months, verified by helical CT and MRI. ConclusionOsteochondral allograft transplants stored fresh at 37 °C are established as a long-term solution for the treatment of localized osteochondral defects in the knee.

91. The viable disc tissue allograft supplementation (VAST) randomized controlled trial in patients with chronic discogenic low back pain: Correlating age with clinical outcome

<h3>BACKGROUND CONTEXT</h3> The development of chronic low back pain (LBP) results from internal disc disruption within the nucleus pulposus and is the most common etiology of LBP in young to middle-age adults. A viable disc tissue allograft has been developed to supplement tissue loss associated with degenerative lumbar disc disease and the development of chronic discogenic LBP. <h3>PURPOSE</h3> In this study, the clinical outcomes of patients in the VAST study were analyzed on the basis of patient age (above and below the median age of all patients). <h3>STUDY DESIGN/SETTING</h3> Randomized, controlled, multicenter study in US. <h3>PATIENT SAMPLE</h3> A total of 218 patients with chronic low back pain secondary to single-level or two-level degenerative disc disease were enrolled in the study. Patients had back pain for a minimum of 6 months that was recalcitrant to nonoperative treatment modalities. Inclusion criteria also included pretreatment VASPI ≥ 40 and ODI Score ≥ 40. <h3>OUTCOME MEASURES</h3> Oswestry Disability Index (ODI) and visual analog scale of pain intensity (VASPI), neurological exam and adverse events. Plain film radiographs and magnetic resonance (MR) imaging scans were used to assess disc space height and spinal alignment and to determine the degree of disc degeneration. <h3>METHODS</h3> Prospective, multicentered, blinded, randomized clinical trial for subjects with single or two-level degenerative lumbar disc disease was conducted. Patients had back pain for a minimum of 6 months, which was recalcitrant to nonoperative treatment modalities. Patients were blinded and randomized to receive intradiscal injections of either viable disc allograft or saline, or to continue nonblinded with nonsurgical management (NSM). The NSM group could cross over to the allograft group after 3 months. All patients crossed over into the investigational allograft treatment group. Patient data based on age comparing younger patients (19-42 years, 104 patients) to older patients (43-73 years, 114 patients) across all three groups were analyzed. Statistical analyses were performed based on 12-month post treatment improvements in ODI and VAS. <h3>RESULTS</h3> In the younger patient group, a significantly larger improvement in ODI of 29.7 points in the allograft treated group and 45.0 points in the cross over group was observed vs 17.4 points with the saline group (Overall p-value =.004). This effect was also observed in multiple responder analyses with a significantly higher percentage of allograft-treated patients demonstrating ≥15 and ≥20-point improvements in ODI vs the saline group. 69.1% of the younger patients treated with viable allograft vs 35.3% of the saline group showed clinically meaningful improvement of ODI ≥20-points (Overall p-value=.004). No significant interaction between treatment and age in VAS, and no significant benefits of allograft treatment on VAS in younger vs older patients was observed. Adverse events were reported in 30.9%, 10.5% and 17.6% of younger patients in the allograft, placebo, and conservative care groups, respectively (overall p value=0.155), compared to 28.8%, 15.8%, and 9.1% of older patients in these groups (overall p value=0.136), most commonly back pain. <h3>CONCLUSIONS</h3> This subgroup analysis indicates that younger patients (≤ 42 years) have more favorable clinical outcome vs older patients at 12 months. This data suggests that a viable disc tissue injection can effectively treat chronic discogenic LBP nonsurgically with meaningful results demonstrated in a younger patient population. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

O-39: Comparison of the Effects of Normothermic Machine Perfusion and Cold Storage Preservation on Porcine Intestinal Allograft Regenerative Potential and Viability

O-39: Comparison of the Effects of Normothermic Machine Perfusion and Cold Storage Preservation on Porcine Intestinal Allograft Regenerative Potential and Viability

Overview of Imaging Modalities in Evaluation of Bone Allograft Viability

The goal of this review is to assess the importance of various imaging modalities which can be used in assessing the viability and integrity of the bone allograft. As it is widely in use in majority of major and minor reconstructive procedures.

Ex situ heart perfusion: The past, the present, and the future

Despite the advancements in medical treatment, mechanical support, and stem cell therapy, heart transplantation remains the most effective treatment for selected patients with advanced heart failure. However, with an increase in heart failure prevalence worldwide, the gap between donor hearts and patients on the transplant waiting list keeps widening. Ex situ machine perfusion has played a key role in augmenting heart transplant activities in recent years by enabling the usage of donation after circulatory death hearts, allowing longer interval between procurement and implantation, and permitting the safe use of some extended-criteria donation after brainstem death hearts. This exciting field is at a hinge point, with 1 commercially available heart perfusion machine, which has been used in hundreds of heart transplantations, and a number of devices being tested in the pre-clinical and Phase 1 clinical trial stage. However, no consensus has been reached over the optimal preservation temperature, perfusate composition, and perfusion parameters. In addition, there is a lack of objective measurement for allograft quality and viability. This review aims to comprehensively summarize the lessons about ex situ heart perfusion as a platform to preserve, assess, and repair donor hearts, which we have learned from the pre-clinical studies and clinical applications, and explore its exciting potential of revolutionizing heart transplantation.