Therapeutic strategy for instant blood-mediated inflammatory reaction after islet transplantation / 器官移植

As an effective procedure for type 1 diabetes mellitus and end-stage type 2 diabetes mellitus, islet transplantation could enable those patients to obtain proper control of blood glucose levels. Instant blood-mediated inflammatory reaction (IBMIR) is a nonspecific inflammation during early stage after islet transplantation. After IBMIR occurs, coagulation cascade, complement system activation and inflammatory cell aggregation may be immediately provoked, leading to loss of a large quantity of transplant islets, which severely affects clinical efficacy of islet transplantation. How to alleviate the islet damage caused by IBMIR is a hot topic in islet transplantation. Heparin and etanercept, an inhibitor of tumor necrosis factor-α, are recommended as drugs for treating IBMIR following islet transplantation. Recent studies have demonstrated that multiple approaches and drugs may be adopted to mitigate the damage caused by IBMIR to the islets. In this article, the findings in clinical and preclinical researches were reviewed, aiming to provide reference for the management of IBMIR after islet transplantation.

Research progress on islet protection and functional maintenance / 器官移植

Islet transplantation is a promising treatment of diabetes mellitus and its complications. Nevertheless, dysfunction post-transplantation, rejection and shortage of donors are the bottleneck issues in the field of islet transplantation. Optimizing the preservation method of pancreas plays a positive role in obtaining a sufficient quantity of effective islets and maintaining their functions. During the culture stage, anti-rejection and anti-apoptosis treatment of islets, including mesenchymal stem cell (MSC), MSC-derived exosomes, anti-apoptosis drugs and gene modification, may become major approaches for islet protection and functional maintenance in clinical islet transplantation. Use of anti-instant blood-mediated inflammatory reaction (IBMIR) drugs after islet transplantation also plays a critical role in protecting islet function. In this article, the whole process from islet preparation to islet transplantation was illustrated, and relevant strategies of islet protection and functional maintenance were reviewed, aiming to provide reference for improving the quality of donors to compensate for the shortage of absolute quantity of donors and elevating the efficiency of islet transplantation.

Xenotransplantation of Genetically Modified Neonatal Pig Islets Cures Diabetes in Baboons.

Xenotransplantation using porcine donors is rapidly approaching clinical applicability as an alternative therapy for treatment of many end-stage diseases including type 1 diabetes. Porcine neonatal islet cell clusters (NICC) have normalised blood sugar levels for relatively short periods in the preclinical diabetic rhesus model but have met with limited success in the stringent baboon model. Here we report that NICC from genetically modified (GM) pigs deleted for αGal and expressing the human complement regulators CD55 and CD59 can cure diabetes long-term in immunosuppressed baboons, with maximum graft survival exceeding 22 months. Five diabetic baboons were transplanted intraportally with 9,673 - 56,913 islet equivalents (IEQ) per kg recipient weight. Immunosuppression consisted of T cell depletion with an anti-CD2 mAb, tacrolimus for the first 4 months, and maintenance with belatacept and anti-CD154; no anti-inflammatory treatment or cytomegalovirus (CMV) prophylaxis/treatment was given. This protocol was well tolerated, with all recipients maintaining or gaining weight. Recipients became insulin-independent at a mean of 87 ± 43 days post-transplant and remained insulin-independent for 397 ± 174 days. Maximum graft survival was 675 days. Liver biopsies showed functional islets staining for all islet endocrine components, with no evidence of the inflammatory blood-mediated inflammatory reaction (IBMIR) and minimal leukocytic infiltration. The costimulation blockade-based immunosuppressive protocol prevented an anti-pig antibody response in all recipients. In conclusion, we demonstrate that genetic modification of the donor pig enables attenuation of early islet xenograft injury, and in conjunction with judicious immunosuppression provides excellent long-term function and graft survival in the diabetic baboon model.

Protective role of expression of human complement regulatory protein hCD55 in islet xenotransplantation / 器官移植

Objective To validate whether the expression of human cluster of differentiation 55 (hCD55) protein in porcine islet cells could inhibit the activation of complement components in human serum. Methods Four adult pigs with WT (wild type), GTKO [α-1, 3-galactosyltransferase (GGTA1) knockout], GTKO/hCD55 and hCD55 genotypes were selected. Islet cells were isolated from WT, GTKO and GTKO/hCD55 pigs, and the purity and insulin secretion function were detected. The expression of hCD55 at the DNA, RNA and protein levels was analyzed by agarose gel electrophoresis, reverse transcription polymerase chain reaction (RT-PCR) and flow cytometry, respectively. Complement-dependent cytotoxicity assay and complement deposition assay were performed under the incubation conditions with fresh human serum. Results The purity of isolated porcine islet cells from three genotype pigs was > 75%, and the glycemic index was > 1. The expression of hCD55 messenger RNA(mRNA) and protein in GTKO/hCD55 porcine islet cells decreased the deposition of human complement component C3c and membrane-attacking complex C5b-9, and reduced the cytotoxicity. Conclusions The expression of hCD55 protein in porcine islet cells could inhibit the activation of human complement and reduce complement-mediated killing effect, indicating that hCD55 protein could exert complement protection effect on porcine islet cells. These findings provide theoretical basis for the application of hCD55 in islet xenotransplantation.

Selection of Tissue Factor-Deficient Cell Transplants as a Novel Strategy for Improving Hemocompatibility of Human Bone Marrow Stromal Cells.

Intravascular transplantation of tissue factor (TF)-bearing cells elicits an instant blood-mediated inflammatory reaction (IBMIR) resulting in thrombotic complications and reduced engraftment. Here we studied the hemocompatibility of commonly used human white adipose tissue (WAT), umbilical cord (UC) and bone marrow stromal cells (BMSC) and devised a possible strategy for safe and efficient stromal cell transplantation. Methods: Stromal cell identity, purity, and TF expression was tested by RTQ-PCR, flow cytometry and immunohistochemistry. Pro-coagulant activity and fibrin clot formation/stabilization was measured In Vitro by viscoelastic rotational plasma-thromboelastometry and in vivo by injecting sorted human stromal cells intravenously into rats. The impact of TF was verified in factor VII-deficient plasma and by sort-depleting TF/CD142+ BMSC. Results: We found significantly less TF expression by a subpopulation of BMSC corresponding to reduced pro-coagulant activity. UC and WAT stroma showed broad TF expression and durable clotting. Higher cell numbers significantly increased clot formation partially dependent on coagulation factor VII. Depleting the TF/CD142+ subpopulation significantly ameliorated BMSC's hemocompatibility without affecting immunomodulation. TF-deficient BMSC did not produce thromboembolism in vivo, comparing favorably to massive intravascular thrombosis induction by TF-expressing stromal cells. Conclusion: We demonstrate that plasma-based thromboelastometry provides a reliable tool to detect pro-coagulant activity of therapeutic cells. Selecting TF-deficient BMSC is a novel strategy for improving cell therapy applicability by reducing cell dose-dependent IBMIR risk. The particularly strong pro-coagulant activity of UC and WAT preparations sounds an additional note of caution regarding uncritical systemic application of stromal cells, particularly from non-hematopoietic extravascular sources.

Developmental endothelial locus-1 modulates platelet-monocyte interactions and instant blood-mediated inflammatory reaction in islet transplantation.

Platelet-monocyte interactions are strongly implicated in thrombo-inflammatory injury by actively contributing to intravascular inflammation, leukocyte recruitment to inflamed sites, and the amplification of the procoagulant response. Instant blood-mediated inflammatory reaction (IBMIR) represents thrombo-inflammatory injury elicited upon pancreatic islet transplantation (islet-Tx), thereby dramatically affecting transplant survival and function. Developmental endothelial locus-1 (Del-1) is a functionally versatile endothelial cell-derived homeostatic factor with anti-inflammatory properties, but its potential role in IBMIR has not been previously addressed. Here, we establish Del-1 as a novel inhibitor of IBMIR using a whole blood-islet model and a syngeneic murine transplantation model. Indeed, Del-1 pre-treatment of blood before addition of islets diminished coagulation activation and islet damage as assessed by C-peptide release. Consistently, intraportal islet-Tx in transgenic mice with endothelial cell-specific overexpression of Del-1 resulted in a marked decrease of monocytes and platelet-monocyte aggregates in the transplanted tissues, relative to those in wild-type recipients. Mechanistically, Del-1 decreased platelet-monocyte aggregate formation, by specifically blocking the interaction between monocyte Mac-1-integrin and platelet GPIb. Our findings reveal a hitherto unknown role of Del-1 in the regulation of platelet-monocyte interplay and the subsequent heterotypic aggregate formation in the context of IBMIR. Therefore, Del-1 may represent a novel approach to prevent or mitigate the adverse reactions mediated through thrombo-inflammatory pathways in islet-Tx and perhaps other inflammatory disorders involving platelet-leukocyte aggregate formation.

A hybrid of cells and pancreatic islets toward a new bioartificial pancreas.

Cell surface engineering using single-stranded DNA-poly(ethylene glycol)-conjugated phospholipid (ssDNA-PEG-lipid) is useful for inducing cell-cell attachment two and three dimensionally. In this review, we summarize our recent techniques for cell surface engineering and their applications to islet transplantation. Because any DNA sequence can be immobilized onto the cell surface by hydrophobic interactions between ssDNA-PEG-lipid and the cellular membrane without impairing cell function, a cell-cell hybrid can be formed through the DNA hybridization. With this technique, it would be possible to create three-dimensional hybrid structures of pancreatic islets coated with various accessory cells, such as patients' own cells, mesenchymal and adipose-derived stem cells, endothelial progenitor cells, neural crest stem cells or regulatory T cells, which might significantly improve the outcome of islet transplantation in diabetic patients.

The role and regulation of complement activation as part of the thromboinflammation elicited in cell therapies.

Cell therapies in which the cells come into direct contact with blood and other body fluids are emerging treatment procedures for patients with various diseases, such as diabetes mellitus, liver insufficiency, and graft-versus-host disease. However, despite recent progress, these procedures are associated with tissue loss caused by thromboinflammatory reactions. These deleterious reactions involve the activation of the complement and coagulation cascades and platelet and leukocyte activation, ultimately resulting in clot formation and damage to the implanted cells. In this concept review, we discuss the basic mechanisms underlying the thrombininflammatory process, with special reference to the engagement of complement and emerging strategies for the therapeutic regulation of these reactions that include the use of selective systemic inhibitors and various procedures to coat the surfaces of the cells. The coating procedures may also be applied to other treatment modalities in which similar mechanisms are involved, including whole organ transplantation, treatment with biomaterials in contact with blood, and extracorporeal procedures.

Current Strategies for Successful Islet Xenotransplantation / 대한이식학회지

Diabetes mellitus is increasing all over the world and is a serious health problem. Pancreatic islet transplantation is promising treatment for diabetes mellitus, but an imbalance between deceased pancreas donors and recipients limited the widespread clinical application. Therefore, pig islets could be used as an alternative islet source in transplantation. However, a big hurdle to clinical application of islet xenotransplantation is the instant blood mediated inflammatory reaction (IBMIR), which is characterized by activation of the coagulation cascade, platelets and complement systems. Innate immune cells infiltrate the islets in the process of IBMIR and thereby accelerate the early graft loss. Characteristics of IBMIR in islet xenotransplantion are very different from the rejection in solid organ xenotransplantation. Therefore, we focus on the molecules for surmounting IBMIR in order to accomplish successful islet xenotransplantation. To prevent the IBMIR in islet xenotransplantation, development of genetic modified pigs containing anti-coagulant, anti-thrombosis and complement regulatory genes, or capsulation of islet with biomaterials for blocking immune response around islet surface can be tried. Galpha-Gal knockout pigs and the diverse transgenic pigs for complement regulatory protein or anti-coagulant genes have been developed for xenotransplantation. This review summarized on characteristics of rejection in islet xenotransplantation and discusses the strategies for overcoming the rejection.