Evolution of Pancreas Transplantation At A Single Institution-50+ Years and 2,500 Transplants.

OBJECTIVE: To describe the evolution of pancreas transplantation, including improved outcomes and factors associated with improved outcomes over the past five decades. BACKGROUND: The world's first successful pancreas transplant was performed in December 1966 at the University of Minnesota. As new modalities for diabetes treatment mature, we must carefully assess the current state of pancreas transplantation to determine its ongoing role in patient care. METHODS: A single-center retrospective review of 2,500 pancreas transplants performed over >50 years in bivariate and multivariable models. Transplants were divided into six eras; outcomes are presented for the entire cohort and by era. RESULTS: All measures of patient and graft survival improved progressively through the six transplant eras. The overall death censored (DC) pancreas graft half-lives were >35 years for simultaneous pancreas and kidney (SPK), 7.1 years for pancreas after kidney (PAK), and 3.3 years for pancreas transplants alone (PTA). The 10-year DC pancreas graft survival rate in the most recent era was 86.9% for SPK recipients, 58.2% for PAK recipients, and 47.6% for PTA. Overall graft loss was most influenced by patient survival in SPK transplants, whereas graft loss in PAK and PTA recipients was more often due to graft failures. Predictors of improved pancreas graft survival were primary transplants, bladder drainage of exocrine secretions, younger donor age, and shorter preservation time. CONCLUSIONS: Pancreas outcomes have significantly improved over time via sequential, but overlapping, advances in surgical technique, immunosuppressive protocols, reduced preservation time, and the more recent reduction of immune-mediated graft loss.

On Chip Sorting of Stem Cell-Derived ß Cell Clusters Using Traveling Surface Acoustic Waves.

There is a critical need for sorting complex materials, such as pancreatic islets of Langerhans, exocrine acinar tissues, and embryoid bodies. These materials are cell clusters, which have highly heterogeneous physical properties (such as size, shape, morphology, and deformability). Selecting such materials on the basis of specific properties can improve clinical outcomes and help advance biomedical research. In this work, we focused on sorting one such complex material, human stem cell-derived ß cell clusters (SC-ß cell clusters), by size. For this purpose, we developed a microfluidic device in which an image detection system was coupled to an actuation mechanism based on traveling surface acoustic waves (TSAWs). SC-ß cell clusters of varying size (∼100-500 µm in diameter) were passed through the sorting device. Inside the device, the size of each cluster was estimated from their bright-field images. After size identification, larger clusters, relative to the cutoff size for separation, were selectively actuated using TSAW pulses. As a result of this selective actuation, smaller and larger clusters exited the device from different outlets. At the current sample dilutions, the experimental sorting efficiency ranged between 78% and 90% for a separation cutoff size of 250 µm, yielding sorting throughputs of up to 0.2 SC-ß cell clusters/s using our proof-of-concept design. The biocompatibility of this sorting technique was also established, as no difference in SC-ß cell cluster viability due to TSAW pulse usage was found. We conclude the proof-of-concept sorting work by discussing a few ways to optimize sorting of SC-ß cell clusters for potentially higher sorting efficiency and throughput. This sorting technique can potentially help in achieving a better distribution of islets for clinical islet transplantation (a potential cure for type 1 diabetes). Additionally, the use of this technique for sorting islets can help in characterizing islet biophysical properties by size and selecting suitable islets for improved islet cryopreservation.

CPA toxicity screening of cryoprotective solutions in rat hearts.

In clinical practice, donor hearts are transported on ice prior to transplant and discarded if cold ischemia time exceeds ∼5 h. Methods to extend these preservation times are critically needed, and ideally, this storage time would extend indefinitely, enabling improved donor-to-patient matching, organ utilization, and immune tolerance induction protocols. Previously, we demonstrated successful vitrification and rewarming of whole rat hearts without ice formation by perfusion-loading a cryoprotective agent (CPA) solution prior to vitrification. However, these hearts did not recover any beating even in controls with CPA loading/unloading alone, which points to the chemical toxicity of the cryoprotective solution (VS55 in Euro-Collins carrier solution) as the likely culprit. To address this, we compared the toxicity of another established CPA cocktail (VEG) to VS55 using ex situ rat heart perfusion. The CPA exposure time was 150 min, and the normothermic assessment time was 60 min. Using Celsior as the carrier, we observed partial recovery of function (atria-only beating) for both VS55 and VEG. Upon further analysis, we found that the VEG CPA cocktail resulted in 50 % lower LDH release than VS55 (N = 4, p = 0.017), suggesting VEG has lower toxicity than VS55. Celsior was a better carrier solution than alternatives such as UW, as CPA + Celsior-treated hearts spent less time in cardiac arrest (N = 4, p = 0.029). While we showed substantial improvement in cardiac function after exposure to vitrifiable concentrations of CPA by improving both the CPA and carrier solution formulation, further improvements will be required before we achieve healthy cryopreserved organs for transplant.

Transportability of causal inference under random dynamic treatment regimes for kidney-pancreas transplantation.

A difficult decision for patients in need of kidney-pancreas transplant is whether to seek a living kidney donor or wait to receive both organs from one deceased donor. The framework of dynamic treatment regimes (DTRs) can inform this choice, but a patient-relevant strategy such as "wait for deceased-donor transplant" is ill-defined because there are multiple versions of treatment (i.e., wait times, organ qualities). Existing DTR methods average over the distribution of treatment versions in the data, estimating survival under a "representative intervention." This is undesirable if transporting inferences to a target population such as patients today, who experience shorter wait times thanks to evolutions in allocation policy. We, therefore, propose the concept of a generalized representative intervention (GRI): a random DTR that assigns treatment version by drawing from the distribution among strategy compliers in the target population (e.g., patients today). We describe an inverse-probability-weighted product-limit estimator of survival under a GRI that performs well in simulations and can be implemented in standard statistical software. For continuous treatments (e.g., organ quality), weights are reformulated to depend on probabilities only, not densities. We apply our method to a national database of kidney-pancreas transplant candidates from 2001-2020 to illustrate that variability in transplant rate across years and centers results in qualitative differences in the optimal strategy for patient survival.

Challenges, highlights, and opportunities in cellular transplantation: A white paper of the current landscape.

Although cellular transplantation remains a relatively small field compared to solid organ transplantation, the prospects for advancement in basic science and clinical care remain bountiful. In this review, notable historical events and the current landscape of the field of cellular transplantation are reviewed with an emphasis on islets (allo- and xeno-), hepatocytes (including bioartificial liver), adoptive regulatory immunotherapy, and stem cells (SCs, specifically endogenous organ-specific and mesenchymal). Also, the nascent but rapidly evolving field of three-dimensional bioprinting is highlighted, including its major processing steps and latest achievements. To reach its full potential where cellular transplants are a more viable alternative than solid organ transplants, fundamental change in how the field is regulated and advanced is needed. Greater public and private investment in the development of cellular transplantation is required. Furthermore, consistent with the call of multiple national transplant societies for allo-islet transplants, the oversight of cellular transplants should mirror that of solid organ transplants and not be classified under the unsustainable, outdated model that requires licensing as a drug with the Food and Drug Administration. Cellular transplantation has the potential to bring profound benefit through progress in bioengineering and regenerative medicine, limiting immunosuppression-related toxicity, and providing markedly reduced surgical morbidity.

Survival benefit of the homologous kidney allograft in simultaneous pancreas-kidney transplants and its potential protective role.

The superior death-censored graft survival of the pancreas allograft in simultaneous pancreas kidney transplants (SPK) over pancreas alone transplants (PTA) has long been recognized. Using data from the Scientific Registry of Transplant Recipients (SRTR) and a high-volume pancreas transplant program, we investigated the possible protective role of the kidney allograft in SPK transplants. We analyzed 19 043 primary pancreas transplants between 2000 and 2020, including 735 transplants performed at the University of Minnesota. SPK transplants demonstrated a superior death-censored graft survival over pancreas after kidney (PAK) and simultaneous pancreas and living donor kidney (SPLK) transplants, which both demonstrated better survival than PTA transplants. This effect was not affected by mode or duration of renal replacement therapy prior to transplant. Furthermore, we found that HLA match at the B-locus between the prior kidney and current pancreas allografts demonstrated a protective effect (HR .54; 95% confidence interval .29-1.00), with a 2-antigen match demonstrating superior death-censored graft survival to a 1- or 0-antigen match. We propose that a homologous kidney allograft in SPK transplants affords protection to the pancreas allograft-likely through a combination of better surveillance for rejection and direct immunoprotection offered by the same-donor kidney.

Influence of the procurement surgeon on transplanted abdominal organ outcomes: An SRTR analysis to evaluate regional organ procurement collaboration.

Single-center studies have demonstrated regional organ procurement collaboration to reduce travel redundancy and improve procurement efficiency. We studied deceased donor kidney, liver, and pancreas transplants performed in the United States between 2002 and 2014 using the Scientific Registry of Transplant Recipients (SRTR). We compared graft failure (GF), death-censored graft failure (DCGF), and patient death (PD) between organs procured by surgeons from the recipient's center (transplant procurement team [TPT]) versus surgeons from a different center (NTPT). Primary nonfunction (PNF) was assessed for liver and kidney and delayed graft function (DGF) for kidney using mixed-effects logistic modeling. There were 64 906 liver (61.6% TPT), 118 152 kidney (26.1% TPT), 10 832 simultaneous pancreas kidney (SPK; 56.6% TPT), and 4378 solitary pancreas (SP; 34.0% TPT) transplants. When compared to NTPT, DCGF for organs procured by TPT was significantly less for liver (adjusted HR: 0.93; 95% CI: 0.88-0.98) and marginally significant for kidney (0.97; 0.93-1.00) and SPK (0.90; 0.82-1.00), and not significant for SP (0.98; 0.86 -1.11). DGF for TPT kidney was significantly lower (adjusted OR 0.91; 0.87-0.95). Albeit modest, our findings demonstrate a difference between locally procured organs and those procured by the implanting team. Elucidating the etiology of these differences will enhance regional organ procurement collaboration.

Delivery of transplant care among Hmong kidney transplant recipients: Outcomes from a single institution.

Kidney transplantation entails well-coordinated complex care delivery. Patient-provider cultural and linguistic discordance can lead to healthcare disparities. We analyzed kidney transplantation outcomes among our institution's Hmong recipients using a retrospective cohort study. From 1995 to 2015, 2164 adult (age ≥18) recipients underwent kidney transplantation at our institution; 78 self-identified as Hmong. Survival rates were analyzed and compared to Caucasian recipients (n = 2086). Fifty (64.1%) Hmong recipients consistently requested interpreters. Mean follow-up was 9.8 years for both groups. Hmong recipients (N = 78) were on average younger at transplant (45.7 vs 49.7 years; P = 0.02), more likely to be female (56% vs 38%; P = 0.001), and had higher gravidity (5.0 vs 1.9 births; P < 0.001). There were 13 (16.7%) Hmong living donor recipients, who were younger (32.8 vs 42.9 years; P = 0.006) at transplant compared to Caucasians (1429, 68.5%). Hmong 1- and 5-year patient survival was 100%; Caucasians, 97.1% and 88% (P < 0.001). Hmong 1- and 5-year graft survival was 98.7% and 84.9%; Caucasians 94.8% and 80.9% (P = 0.013). One- and 5-year rejection-free survival showed no difference (88.9% vs 82.4%; 86.7% vs 83.4%, P = 0.996). Despite cultural and linguistic differences between Hmong recipients and providers, we found no evidence of inferiority in KT outcomes in the Hmong population.

Age alone is not a contraindication to kidney donation: Outcomes of donor nephrectomy in the elderly.

With increasing organ demand, living kidney donation from older donors (>60-years-old) has become more common. Between 1975 and 2014, 3752 donor nephrectomies (DN) were performed at University of Minnesota; 167 (4.5%) were >60-years-old Short- and long-term outcomes were compared between contemporaneous >60-years-old and <60-years-old donors. On univariate analysis, >60-years-old were more likely to have had prior abdominal surgery and hypertension; and less likely to smoke. Baseline estimated glomerular filtration rate (eGFR) was lower in >60-years-old (80 ± 16 vs 101 ± 26 mL/min/1.73 m2 ; P < .001). Intraoperative and postoperative complications were similar, except a higher prevalence of <30 day ileus (3% vs 7%; P = .021) and longer postoperative length of stay (LOS) (4.2 vs 4.6 days; P = .005). On multivariate analysis, <30 day ileus and LOS continued to be significantly greater for >60-years-old After >20 years post-DN, systolic blood pressure was significantly higher among >60-years-old (142 vs 125 mm Hg; P < .001) and HTN was diagnosed earlier (9 vs 14 years). After donation, eGFR was significantly lower for >60-years-old but slope of eGFR and rates of end-stage renal disease (ESRD) were not significantly different >20 years post-DN. Thus, kidney donation among carefully selected >60-years-old poses minimal perioperative risks and no added risk of long-term ESRD.

Incidence and magnitude of post-transplant cardiovascular disease after pediatric kidney transplantation: Risk factor analysis of 1058 pediatric kidney transplants at the university of Minnesota.

BACKGROUND: KT recipients have increased the risk of CVD. The incidence of post-transplant CVEs among pediatric recipients has not been well-characterized. PATIENTS AND METHODS: Between 1963 and 2015, 884 pediatric (age: 0-17 years old) recipients received 1058 KTs at our institution. The cumulative incidence of CVEs was analyzed. Statistical models were used to estimate risk factors for developing post-transplant CVEs. RESULTS: Overall median patient survival was 33 years (IQR: 18.7-47). A total of 362 CVEs occurred in 161 (18.3%) patients at a median age of 20.5 years. Arrhythmias (18%) were most common. Cumulative risk of post-transplant CVEs was 9% at 10 years, 17% at 20 years, 25% at 30 years, and 36% at 40 years. Development of post-transplant CVEs was associated with increased mortality (HR 2.25 [95% CI 1.61-3.14]); of those who developed a CVE and died, 22/51 (43.1%) died of CVD. Multivariable risk factors for post-transplant CVEs included a history of pretransplant CVD (aHR 1.92 [1.18-3.13] and graft failure (4.57 [3.13-6.67]). DISCUSSION: A pretransplant history of CVD and a failed graft are significant risk factors for the development of post-transplant CVE. CVD increases the risk of post-transplant death or graft loss.

Cryopreservation by vitrification: a promising approach for transplant organ banking.

PURPOSE OF REVIEW: The objective of this review is to describe the physical and biological barriers to organ cryopreservation, historic approaches for conventional cryopreservation and evolving techniques for ice-free cryopreservation by vitrification. RECENT FINDINGS: Vitrification is a process whereby a biologic substance is cooled to cryogenic temperatures without the destructive phase transition of liquid to solid ice. Recent advances in cryoprotective solutions, organ perfusion techniques and novel heating technologies have demonstrated the potential for vitrification and rewarming organs on a scale applicable for human transplantation. SUMMARY: Successful strategies for organ cryopreservation could enable organ banking, which would recast the entire process in which organs are recovered, allocated, stored and prepared for transplant.

Significant arterial complications after pancreas transplantation-A single-center experience and review of literature.

Arterial fistulas and pseudoaneurysms are rarely described significant arterial complications associated with pancreas transplantation that sometimes present with herald or catastrophic bleeding. We herein describe our institutional case series with a focus on management and outcomes. Of 2256 pancreas transplants, 24 arterial complications were identified in 23 recipients. Chart review was performed to describe the clinical characteristics, treatments, and outcomes of the complications (pseudoaneurysm, arterial enteric/cystic/ureteric fistula, or arteriovenous fistula). Of these 23 patients, 57% had a failed allograft at the time of the complication. Nine patients underwent primary surgical repair of 10 complications, 13 were treated by endovascular methods, and one patient by medical management. In total, 3 embolized patients rebled, 2 of which had failed allografts prior to treatment. Of those with graft function that were treated by embolization alone, all retained graft function. Diagnosis of arterial complications requires a high degree of suspicion and should involve early systemic angiography to evaluate the pancreatic vasculature. Management can be endovascular or surgical and should be individualized. We report our center's evolution from a predominantly surgical to endovascular approach as a definitive vs stabilizing therapy, with selective coiling mostly reserved for well-defined peripheral lesions in patients with a functioning allograft.

Optimizing outcomes in pancreas transplantation: Impact of organ preservation time.

Recent changes to pancreas graft allocation policy have increased the number of organs available for regional and distant sharing, which results in a corresponding increase in preservation time. We sought to systematically assess the impact of cold ischemia time (CIT) on outcomes post-transplant. A retrospective review of 1253 pancreas transplants performed at a single transplant center was performed to correlate CIT to transplant outcomes. The rate of technical failure (TF) increased with 20+ hours of CIT, with a 2.7-fold to 6.2-fold increased rate of TF for pancreas after kidney (PAK), simultaneous pancreas and kidney (SPK), and pancreas transplants overall. Long-term graft survival was best with <12 hours of CIT; graft failure increased 1.2-fold to 1.4-fold with 12-24 hours of CIT and 2.2-fold with 24+ hours. CIT had less influence on the pancreas transplant alone category than either SPK or PAK and had markedly more influence on grafts from older (age >25 years) and overweight (body mass index >25) donors. In the final analysis, grafts with <12 hours of CIT performed the best overall, and strategies that reduce CIT (such as early allocation, pre-recovery cross-matching, and chartered flights for organs) should be considered whenever possible.

Conduction-Dominated Cryomesh for Organism Vitrification.

Vitrification-based cryopreservation is a promising approach to achieving long-term storage of biological systems for maintaining biodiversity, healthcare, and sustainable food production. Using the "cryomesh" system achieves rapid cooling and rewarming of biomaterials, but further improvement in cooling rates is needed to increase biosystem viability and the ability to cryopreserve new biosystems. Improved cooling rates and viability are possible by enabling conductive cooling through cryomesh. Conduction-dominated cryomesh improves cooling rates from twofold to tenfold (i.e., 0.24 to 1.2 × 105  °C min-1 ) in a variety of biosystems. Higher thermal conductivity, smaller mesh wire diameter and pore size, and minimizing the nitrogen vapor barrier (e.g., vertical plunging in liquid nitrogen) are key parameters to achieving improved vitrification. Conduction-dominated cryomesh successfully vitrifies coral larvae, Drosophila embryos, and zebrafish embryos with improved outcomes. Not only a theoretical foundation for improved vitrification in µm to mm biosystems but also the capability to scale up for biorepositories and/or agricultural, aquaculture, or scientific use are demonstrated.

Evidence that Cd101 is an autoimmune diabetes gene in nonobese diabetic mice.

We have previously proposed that sequence variation of the CD101 gene between NOD and C57BL/6 mice accounts for the protection from type 1 diabetes (T1D) provided by the insulin-dependent diabetes susceptibility region 10 (Idd10), a <1 Mb region on mouse chromosome 3. In this study, we provide further support for the hypothesis that Cd101 is Idd10 using haplotype and expression analyses of novel Idd10 congenic strains coupled to the development of a CD101 knockout mouse. Susceptibility to T1D was correlated with genotype-dependent CD101 expression on multiple cell subsets, including Foxp3(+) regulatory CD4(+) T cells, CD11c(+) dendritic cells, and Gr1(+) myeloid cells. The correlation of CD101 expression on immune cells from four independent Idd10 haplotypes with the development of T1D supports the identity of Cd101 as Idd10. Because CD101 has been associated with regulatory T and Ag presentation cell functions, our results provide a further link between immune regulation and susceptibility to T1D.

Model-Guided Design and Optimization of CPA Perfusion Protocols for Whole Organ Cryopreservation.

Vitrification could enable long-term organ preservation, but only after loading high-concentration, potentially toxic cryoprotective agents (CPAs) by perfusion. In this paper, we combine a two-compartment Krogh cylinder model with a toxicity cost function to theoretically optimize the loading of CPA (VMP) in rat kidneys as a model system. First, based on kidney perfusion experiments, we systematically derived the parameters for a CPA transport loading model, including the following: Vb = 86.0% (ra = 3.86 µm), Lp = 1.5 × 10-14 m3/(N·s), ω = 7.0 × 10-13 mol/(N·s), σ = 0.10. Next, we measured the toxicity cost function model parameters as α = 3.12 and ß = 9.39 × 10-6. Combining these models, we developed an improved kidney-loading protocol predicted to achieve vitrification while minimizing toxicity. The optimized protocol resulted in shorter exposure (25 min or 18.5% less) than the gold standard kidney-loading protocol for VMP, which had been developed based on decades of empirical practice. After testing both protocols on rat kidneys, we found comparable physical and biological outcomes. While we did not dramatically reduce toxicity, we did reduce the time. As our approach is now validated, it can be used on other organs lacking defined toxicity data to reduce CPA exposure time and provide a rapid path toward developing CPA perfusion protocols for other organs and CPAs.

Current practice and novel approaches in organ preservation.

Organ transplantation remains the only treatment option for patients with end-stage organ failure. The last decade has seen a flurry of activity in improving organ preservation technologies, which promise to increase utilization in a dramatic fashion. They also bring the promise of extending the preservation duration significantly, which opens the doors to sharing organs across local and international boundaries and transforms the field. In this work, we review the recent literature on machine perfusion of livers across various protocols in development and clinical use, in the context of extending the preservation duration. We then review the next generation of technologies that have the potential to further extend the limits and open the door to banking organs, including supercooling, partial freezing, and nanowarming, and outline the opportunities arising in the field for researchers in the short and long term.

Cryopreservation of Whole Rat Livers by Vitrification and Nanowarming.

Liver cryopreservation has the potential to enable indefinite organ banking. This study investigated vitrification-the ice-free cryopreservation of livers in a glass-like state-as a promising alternative to conventional cryopreservation, which uniformly fails due to damage from ice formation or cracking. Our unique "nanowarming" technology, which involves perfusing biospecimens with cryoprotective agents (CPAs) and silica-coated iron oxide nanoparticles (sIONPs) and then, after vitrification, exciting the nanoparticles via radiofrequency waves, enables rewarming of vitrified specimens fast enough to avoid ice formation and uniformly enough to prevent cracking from thermal stresses, thereby addressing the two main failures of conventional cryopreservation. This study demonstrates the ability to load rat livers with both CPA and sIONPs by vascular perfusion, cool them rapidly to an ice-free vitrified state, and rapidly and homogenously rewarm them. While there was some elevation of liver enzymes (Alanine Aminotransferase) and impaired indocyanine green (ICG) excretion, the nanowarmed livers were viable, maintained normal tissue architecture, had preserved vascular endothelium, and demonstrated hepatocyte and organ-level function, including production of bile and hepatocyte uptake of ICG during normothermic reperfusion. These findings suggest that cryopreservation of whole livers via vitrification and nanowarming has the potential to achieve organ banking for transplant and other biomedical applications.

Vitrification and nanowarming enable long-term organ cryopreservation and life-sustaining kidney transplantation in a rat model.

Banking cryopreserved organs could transform transplantation into a planned procedure that more equitably reaches patients regardless of geographical and time constraints. Previous organ cryopreservation attempts have failed primarily due to ice formation, but a promising alternative is vitrification, or the rapid cooling of organs to a stable, ice-free, glass-like state. However, rewarming of vitrified organs can similarly fail due to ice crystallization if rewarming is too slow or cracking from thermal stress if rewarming is not uniform. Here we use "nanowarming," which employs alternating magnetic fields to heat nanoparticles within the organ vasculature, to achieve both rapid and uniform warming, after which the nanoparticles are removed by perfusion. We show that vitrified kidneys can be cryogenically stored (up to 100 days) and successfully recovered by nanowarming to allow transplantation and restore life-sustaining full renal function in nephrectomized recipients in a male rat model. Scaling this technology may one day enable organ banking for improved transplantation.

Solid Organ Transplant Graft-Versus-Host Disease in a Kidney/Pancreas Transplant Patient: Use of Chimerism Testing and a Rare Presentation of Cutaneous GVHD.

Introduction. Solid organ transplant graft-versus-host disease (SOT-GVHD) is a rare phenomenon in which recipients of solid organ transplant develop GVHD due to the presence of donor lymphocytes in the graft. SOT-GVHD most often occurs in patients receiving small bowel or liver transplants. Diagnosis is typically via identification of lymphocytic infiltration on histopathology and molecular demonstration of donor T cell chimerism in the target organ. The gastrointestinal (GI) system is the most common target of SOT-GVHD, and one estimate places long-term survival of patients with SOT-GVHD at 20% at 5 years. In this report, we present the case of a patient with sequential kidney and pancreas transplant who developed SOT-GVHD targeting host lymphocytes, skin, and liver, with a long period of stability before treatment with antithymocyte globulin. Peripheral blood chimerism testing was used to track response to therapy. Remarkably, he survived 1.5 years despite recurrent infections before dying of unrelated causes.