Bilateral Renal Auto-Transplantation for Retroperitoneal Sarcomas: Is It Underutilized?

Sarcomas are a rare tumor of mesenchymal origin. The liposarcoma is the most common sarcoma of the retroperitoneum. Liposarcomas are typically low grade, and present at an advanced stage and a large size. We report a case of a large retroperitoneal liposarcoma, approximately 50 kg, encasing both kidneys, which was managed via a two-stage resection and staged renal auto-transplantation into the intra-peritoneal pelvis. The patient maintained normal renal function throughout, and remains disease free two years post-resection. Renal auto-transplantation with pelvic placement may facilitate improved margin-free resection. Renal relocation may allow the use of curative-intent ablative therapies such as radiofrequency ablation and radiation in cases of retroperitoneal recurrence.

Orthotopic Transplantation of the Full-length Porcine Intestine After Normothermic Machine Perfusion.

Successful intestinal transplantation is currently hindered by graft injury that occurs during procurement and storage, which contributes to postoperative sepsis and allograft rejection. Improved graft preservation may expand transplantable graft numbers and enhance posttransplant outcomes. Superior transplant outcomes have recently been demonstrated in clinical trials using machine perfusion to preserve the liver. We hypothesized that machine perfusion preservation of intestinal allografts could be achieved and allow for transplantation in a porcine model. Methods: Using a translational porcine model, we developed a device for intestinal perfusion. Intestinal samples were collected at the time of organ procurement, and after 6 h of machine perfusion for gross and histologic evaluation, hourly chemistry panels were performed on the perfusate and were used for protocol optimization. Following transplantation, porcine recipient physical activity, systemic blood parameters, and vital signs were monitored for 2 d before sacrifice. Results: In initial protocol development (generation 1, n = 8 grafts), multiple metabolic, electrolyte, and acid-base derangements were measured. These factors coincided with graft and mesenteric edema and luminal hemorrhage and were addressed with the addition of dialysis. In the subsequent protocol (generation 2, n = 9 grafts), differential jejunum and ileum perfusion were observed resulting in gross evidence of ileal ischemia. Modifications in vasodilating medications enhanced ileal perfusion (generation 3, n = 4 grafts). We report successful transplantation of 2 porcine intestinal allografts after machine perfusion with postoperative clinical and gross evidence of normal gut function. Conclusions: This study reports development and optimization of machine perfusion preservation of small intestine and successful transplantation of intestinal allografts in a porcine model.

Two Compartment Evaluation of Liver Grafts During Acellular Room Temperature Machine Perfusion (acRTMP) in a Rat Liver Transplant Model.

Background: Subnormothermic machine perfusion (SNMP) of liver grafts is currently less clinically developed than normothermic and hypothermic approaches, but may have logistical advantages. At intermediate temperatures, the oxygen demand of the graft is low enough to be satisfied with an acellular perfusate, obviating the need for oxygen carrying molecules. This intermediate metabolic rate, however, is sufficient to support the production of bile, which is emerging as an important indicator of graft injury and viability. In this study, we hypothesized that the biliary compartment would be more sensitive than perfusate in detecting graft injury during SNMP. Methods: To test this hypothesis in a rat model, we performed liver transplants with DCD and control liver grafts after 1 h of acellular room temperature machine perfusion (acRTMP) or static cold storage (SCS). Point of care liver function tests were measured in biliary and perfusate samples after 1 h of machine perfusion. Following transplantation, rats were sacrificed at 24 h for assessment of post-transplant graft function and histology. Results: All point-of-care liver function tests were significantly more concentrated in the biliary compartment than the perfusate compartment during acRTMP. DCD liver grafts could be distinguished from control liver grafts by significantly higher markers of hepatocyte injury (AST, ALT) in the biliary compartment, but not in the perfusate compartment. Classical markers of cholangiocyte injury, such as gammy-glut amyl transferase (GGT), amylase (AML), and alkaline phosphatase were detectable in the biliary compartment, but not in the perfusate compartment. In comparison to SCS, graft preservation by acRTMP produced a significant survival benefit in DCD liver transplantation (75 vs. 0%, p < 0.0030). Conclusion: Together, these findings demonstrate that during acRTMP, the biliary compartment may be a more sensitive indicator of graft injury than the perfusate compartment. Moreover, acRTMP provides superior graft preservation to SCS in rat DCD liver transplantation.

Anti-thymoglobulin induction improves neonatal porcine xenoislet engraftment and survival.

Porcine islet xenotransplantation is a viable strategy to treat diabetes. Its translation has been limited by the pre-clinical development of a clinically available immunosuppressive regimen. We tested two clinically relevant induction agents in a non-human primate (NHP) islet xenotransplantation model to compare depletional versus nondepletional induction immunosuppression. Neonatal porcine islets were isolated from GKO or hCD46/GKO transgenic piglets and transplanted via portal vein infusion in diabetic rhesus macaques. Induction therapy consisted of either basiliximab (n = 6) or rhesus-specific anti-thymocyte globulin (rhATG, n = 6), combined with a maintenance regimen using B7 costimulation blockade, tacrolimus with a delayed transition to sirolimus, and mycophenolate mofetil. Xenografts were monitored by blood glucose levels and porcine C-peptide measurements. Of the six receiving basiliximab induction, engraftment was achieved in 4 with median graft survival of 14 days. All six receiving rhATG induction engrafted with significantly longer xenograft survival at 40.5 days (P = 0.03). These data suggest that depletional induction provides superior xenograft survival to nondepletional induction, in the setting of a costimulation blockade-based maintenance regimen.

Coagulation, inflammation, and CD46 transgene expression in neonatal porcine islet xenotransplantation.

BACKGROUND: Thrombosis is a known consequence of intraportal islet transplantation, particularly for xenogeneic islets. To define the origins of thrombosis after islet xenotransplantation and relate it to early inflammation, we examined porcine islets transplanted into non-human primates using a dual-transplant model to directly compare islet characteristics. METHODS: α1,3-Galactosyltransferase gene-knockout (GTKO) islets with and without expression of the human complement regulatory transgene CD46 (hCD46) were studied. Biologically inert polyethylene microspheres were used to examine the generic pro-thrombotic effects of particle embolization. Immunohistochemistry was performed 1 and 24 hours after transplantation. RESULTS: Xeno-islet transplantation activated both extrinsic and intrinsic coagulation pathways. The intrinsic pathway was also initiated by microsphere embolization, while extrinsic pathway tissue factor (TF) and platelet aggregation were more specific to engrafted islets. hCD46 expression significantly reduced TF, platelet, fibrin, and factor XIIIa accumulation in and around islets but did not alter intrinsic factor activation. Layers of TF+ cells emerged around islets within 24 hours, particularly co-localized with vimentin, and identified as CD3+ and CD68+ cells inflammatory cells. CONCLUSIONS: These findings detail the origins of thrombosis following islet xenotransplantation, relate it to early immune activation, and suggest a role for transgenic hCD46 expression in its mitigation. Layers of TF-positive inflammatory cells and fibroblasts around islets at 24 hours may have important roles in the progressive events of thrombosis, inflammatory cell recruitment, rejection, and the ultimate outcome of transplanted grafts. These suggest that the strategies targeting these elements could yield more progress toward successful xenogeneic islet engraftment and survival.

The role of human CD46 in early xenoislet engraftment in a dual transplant model.

BACKGROUND: Membrane cofactor protein CD46 attenuates the complement cascade by facilitating cleavage of C3b and C4b. In solid organ xenotransplantation, organs expressing CD46 have been shown to resist hyperacute rejection. However, the incremental value of human CD46 expression for islet xenotransplantation remains poorly defined. METHODS: This study attempted to delineate the role of CD46 in early neonatal porcine islet engraftment by comparing Gal-knocked out (GKO) and hCD46-transgenic (GKO/CD46) islets in a dual transplant model. Seven rhesus macaques underwent dual transplant and were sacrificed at 1 hour (n = 4) or 24 hours (n = 3). Both hemilivers were recovered and fixed for immunohistochemistry (CD46, insulin, neutrophil elastase, platelet, IgM, IgG, C3d, C4d, CD68, Caspase 3). Quantitative immunohistochemical analysis was performed using the Aperio Imagescope. RESULTS: Within 1 hour of intraportal infusion of xenografts, no differences were observed between the two types of islets in terms of platelet, antibody, or complement deposition. Cellular infiltration and islet apoptotic activity were also similar at 1 hour. At 24 hours, GKO/CD46 islets demonstrated significantly less platelet deposition (P = 0.01) and neutrophil infiltration (P = 0.01) compared to GKO islets. In contrast, C3d (P = 0.38) and C4d (P = 0.45) deposition was equal between the two genotypes. CONCLUSIONS: Our findings suggest that expression of hCD46 on NPIs potentially provides a measurable incremental survival advantage in vivo by reducing early thrombo-inflammatory events associated with instant blood-mediated inflammatory reaction (IBMIR) following intraportal islet infusion.

Secondary lymphoid tissue and costimulation-blockade resistant rejection: A nonhuman primate renal transplant study.

Naïve T cell activation requires antigen presentation combined with costimulation through CD28, both of which optimally occur in secondary lymphoid tissues such as lymph nodes and the spleen. Belatacept impairs CD28 costimulation by binding its ligands, CD80 and CD86, and in doing so, impairs de novo alloimmune responses. However, in most patients belatacept is ineffective in preventing allograft rejection when used as a monotherapy, and adjuvant therapy is required for control of costimulation-blockade resistant rejection (CoBRR). In rodent models, impaired access to secondary lymphoid tissues has been demonstrated to reduce alloimmune responses to vascularized allografts. Here we show that surgical maneuvers, lymphatic ligation, and splenectomy, designed to anatomically limit access to secondary lymphoid tissues, control CoBRR and facilitate belatacept monotherapy in a nonhuman primate model of kidney transplantation without adjuvant immunotherapy. We further demonstrate that animals sustained on belatacept monotherapy progressively develop an increasingly naïve T and B cell repertoire, an effect that is accelerated by splenectomy and lost at the time of belatacept withdrawal and rejection. These pilot data inform the role of secondary lymphoid tissues on the development of CoBRR and the use of costimulation molecule-focused therapies.

Circulating mitochondria in organ donors promote allograft rejection.

The innate immune system is a critical regulator of the adaptive immune responses that lead to allograft rejection. It is increasingly recognized that endogenous molecules released from tissue injury and cell death are potent activators of innate immunity. Mitochondria, ancestrally related to bacteria, possess an array of endogenous innate immune-activating molecules. We have recently demonstrated that extracellular mitochondria are abundant in the circulation of deceased organ donors and that their presence correlates with early allograft dysfunction. Here we demonstrate the ability of mitochondria to activate endothelial cells (ECs), the initial barrier between a solid organ allograft and its host. We find that mitochondria exposure leads to the upregulation of EC adhesion molecules and their production of inflammatory cytokines and chemokines. Additionally, mitochondrial exposure causes dendritic cells to upregulate costimulatory molecules. Infusion of isolated mitochondria into heart donors leads to significant increase in allograft rejection in a murine heterotopic heart transplantation model. Finally, co-incubation of human peripheral blood mononuclear cells with mitochondria-treated ECs results in increased numbers of effector (IFN-γ+ , TNF-α+ ) CD8+ T cells. These data indicate that circulating extracellular mitochondria in deceased organ donors may directly activate allograft ECs and promote graft rejection in transplant recipients.

Corrigendum to "The Role of Costimulation Blockade in Solid Organ and Islet Xenotransplantation".

[This corrects the article DOI: 10.1155/2017/8415205.].

The Role of Costimulation Blockade in Solid Organ and Islet Xenotransplantation.

Pig-to-human xenotransplantation offers a potential bridge to the growing disparity between patients with end-stage organ failure and graft availability. Early studies attempting to overcome cross-species barriers demonstrated robust humoral immune responses to discordant xenoantigens. Recent advances have led to highly efficient and targeted genomic editing, drastically altering the playing field towards rapid production of less immunogenic porcine tissues and even the discussion of human xenotransplantation trials. However, as these humoral immune barriers to cross-species transplantation are overcome with advanced transgenics, cellular immunity to these novel xenografts remains an outstanding issue. Therefore, understanding and optimizing immunomodulation will be paramount for successful clinical xenotransplantation. Costimulation blockade agents have been introduced in xenotransplantation research in 2000 with anti-CD154mAb. Most recently, prolonged survival has been achieved in solid organ (kidney xenograft survival > 400 days with anti-CD154mAb, heart xenograft survival > 900 days, and liver xenograft survival 29 days with anti-CD40mAb) and islet xenotransplantation (>600 days with anti-CD154mAb) with the use of these potent experimental agents. As the development of novel genetic modifications and costimulation blocking agents converges, we review their impact thus far on preclinical xenotransplantation and the potential for future application.

Memory T cells in organ transplantation: progress and challenges.

Antigen-experienced T cells, also known as memory T cells, are functionally and phenotypically distinct from naive T cells. Their enhanced expression of adhesion molecules and reduced requirement for co-stimulation enables them to mount potent and rapid recall responses to subsequent antigen encounters. Memory T cells generated in response to prior antigen exposures can cross-react with other nonidentical, but similar, antigens. This heterologous cross-reactivity not only enhances protective immune responses, but also engenders de novo alloimmunity. This latter characteristic is increasingly recognized as a potential barrier to allograft acceptance that is worthy of immunotherapeutic intervention, and several approaches have been investigated. Calcineurin inhibition effectively controls memory T-cell responses to allografts, but this benefit comes at the expense of increased infectious morbidity. Lymphocyte depletion eliminates allospecific T cells but spares memory T cells to some extent, such that patients do not completely lose protective immunity. Co-stimulation blockade is associated with reduced adverse-effect profiles and improved graft function relative to calcineurin inhibition, but lacks efficacy in controlling memory T-cell responses. Targeting the adhesion molecules that are upregulated on memory T cells might offer additional means to control co-stimulation-blockade-resistant memory T-cell responses.

Islet cell xenotransplantation: a serious look toward the clinic.

Type I diabetes remains a significant clinical problem in need of a reliable, generally applicable solution. Both whole organ pancreas and islet allotransplantation have been shown to grant patients insulin independence, but organ availability has restricted these procedures to an exceptionally small subset of the diabetic population. Porcine islet xenotransplantation has been pursued as a potential means of overcoming the limits of allotransplantation, and several preclinical studies have achieved near-physiologic function and year-long survival in clinically relevant pig-to-primate model systems. These proof-of-concept studies have suggested that xenogeneic islets may be poised for use in clinical trials. In this review, we examine recent progress in islet xenotransplantation, with a critical eye toward the gaps between the current state of the art and the state required for appropriate clinical investigation.

Impact of recipient age on whole organ pancreas transplantation.

AIM: The goal of this study was to assess the impact of recipient age on post-transplant outcome. METHODS: All pancreas transplants performed at Indiana University between 2003 and 2011 were reviewed. Demographic data were compared using standard chi-square and ANOVA testing. Standard Cox regression survival analysis was performed using a direct entry method for covariates. RESULTS: Patients (n = 405) were divided by decade: <30 yr (n = 37), 30-39 (n = 109), 40-49 (n = 156), 50-59 (n = 85), and ≥ 60 yr of age (n = 18). Group demographics did not differ except for median ischemia time, which was between 7.0 and 8.5 h (p = 0.02). Early graft loss and one yr graft and patient survival were similar between the groups. Long-term patient survival demonstrated a trend toward decreased five-yr survival with increasing recipient age (p = NS). Graft survival at five yr by Cox regression was the lowest for the <30 yr group (74%), while all other groups were similar around 80% (p = NS). CONCLUSION: No statistically significant differences in pancreas transplant outcomes were demonstrated when recipients were stratified by recipient age. These results suggest that older recipients can successfully undergo pancreas transplantation and expect five-yr outcomes similar to those seen in younger recipients.

Kidney paired donation.

Kidney paired donation (KPD) was first suggested in 1986, but it was not until 2000 when the first paired donation transplant was performed in the USA. In the past decade, KPD has become the fastest growing source of transplantable kidneys, overcoming the barrier faced by living donors deemed incompatible with their intended recipients. This review provides a basic overview of the concepts and challenges faced by KPD as we prepare for a national pilot program with the United Network for Organ Sharing. Several different algorithms have been creatively implemented in the USA and elsewhere to transplant paired donors, each method uniquely contributing to the success of KPD. As the paired donor pool grows, the problem of determining allocation strategies that maximize equity and utility will become increasingly important as the transplant community seeks to balance quality and quantity in choosing the best matches. Financing for paired donation is a major issue, as philanthropy alone cannot support the emerging national system. We also discuss the advent of altruistic or non-directed donors in KPD, and the important role of chains in addition to exchanges. This review is designed to provide insight into the challenges that face the emerging national KPD system in the USA, now 5 years into its development.

Altruistic donation through the Alliance for Paired Donation.

Kidney paired donation is an evolving strategy for overcoming the incompatibility barrier inherent in living donor kidney transplantation. As evidence of the growing interest in this new approach, more than 800 paired donation transplants have been performed in the United States as of February 2010, greater than half of which were performed in 2008 and 2009. Recent advances in this field have incorporated non-directed or altruistic donors to initiate chains of transplants that are either performed simultaneously, or by utilizing "bridge donors" who continue a nonsimultaneous chain at a later date. In this report from the Alliance for Paired Donation, we summarize our experience with altruistic and bridge donors. The program has utilized 6 altruistic-donor initiated chains that have resulted in 22 transplants and have generated 16 bridge donors. In addition, we report our experience with website registrations and national media exposure that has resulted in over 3500 registrations on the APD website, with 37% expressing interest in altruistic donation. We discuss the financial barriers to paired donation in America, and suggest a solution similar to the CMS-approved organ procurement organization standard acquisition charges for deceased donors. Finally, we propose a new approach to integrate paired donation and deceased donors that would allow altruistic living donors to benefit patients on the waiting list without willing, but incompatible donors and simultaneously eliminate the risk of reneging in nonsimultaneous extended altruistic donor chains. We call this new approach a "reverse list exchange".