Dirk Ysebaert

Correlation between beta cell mass and glycemic control in type 1 diabetic recipients of islet cell graft.

Islet grafts can induce insulin independence in type 1 diabetic patients, but their function is variable with only 10% insulin indepence after 5 years. We investigated whether cultured grafts with defined β cell number help standardize metabolic outcome. Nonuremic C-peptide-negative patients received an intraportal graft with 0.5–5.0 × 106 β cells per kilogram of body weight (kgBW) under antithymocyte globulin and mycophenolate mofetil plus tacrolimus. Metabolic outcome at posttransplant (PT) month 2 was used to decide on a second graft under maintenance mycophenolate mofetil/tacrolimus. Graft function was defined by C-peptide >0.5 ng/ml and reduced insulin needs, metabolic control by reductions in HbA1c, glycemia coefficient of variation, and hypoglycemia. At PT month 2, graft function was present in 16 of 17 recipients of >2 × 106 β cells per kgBW versus 0 of 5 with lower number. The nine patients with C-peptide >1 ng/ml and glycemia coefficient of variation of <25% did not receive a second graft; five of them were insulin-independent until PT month 12. The 12 others received a second implant; it achieved insulin-independence at PT month 12 when the first and second graft contained >2 × 106 β cells per kgBW. Of the 20 recipients of at least one graft with >2 × 106 β cells per kgBW, 17 maintained graft function and metabolic control up to PT month 12. At PT month 12, β cell function in insulin-independent patients ranged around 25% of age-matched control values. Thus, 1-year metabolic control can be reproducibly achieved and standardized by cultured islet cell grafts with defined β cell number.

Reporter gene-expressing bone marrow-derived stromal cells are immune-tolerated following implantation in the central nervous system of syngeneic immunocompetent mice

BackgroundCell transplantation is likely to become an important therapeutic tool for the treatment of various traumatic and ischemic injuries to the central nervous system (CNS). However, in many pre-clinical cell therapy studies, reporter gene-assisted imaging of cellular implants in the CNS and potential reporter gene and/or cell-based immunogenicity, still remain challenging research topics.ResultsIn this study, we performed cell implantation experiments in the CNS of immunocompetent mice using autologous (syngeneic) luciferase-expressing bone marrow-derived stromal cells (BMSC-Luc) cultured from ROSA26-L-S-L-Luciferase transgenic mice, and BMSC-Luc genetically modified using a lentivirus encoding the enhanced green fluorescence protein (eGFP) and the puromycin resistance gene (Pac) (BMSC-Luc/eGFP/Pac). Both reporter gene-modified BMSC populations displayed high engraftment capacity in the CNS of immunocompetent mice, despite potential immunogenicity of introduced reporter proteins, as demonstrated by real-time bioluminescence imaging (BLI) and histological analysis at different time-points post-implantation. In contrast, both BMSC-Luc and BMSC-Luc/eGFP/Pac did not survive upon intramuscular cell implantation, as demonstrated by real-time BLI at different time-points post-implantation. In addition, ELISPOT analysis demonstrated the induction of IFN-γ-producing CD8+ T-cells upon intramuscular cell implantation, but not upon intracerebral cell implantation, indicating that BMSC-Luc and BMSC-Luc/eGFP/Pac are immune-tolerated in the CNS. However, in our experimental transplantation model, results also indicated that reporter gene-specific immune-reactive T-cell responses were not the main contributors to the immunological rejection of BMSC-Luc or BMSC-Luc/eGFP/Pac upon intramuscular cell implantation.ConclusionWe here demonstrate that reporter gene-modified BMSC derived from ROSA26-L-S-L-Luciferase transgenic mice are immune-tolerated upon implantation in the CNS of syngeneic immunocompetent mice, providing a research model for studying survival and localisation of autologous BMSC implants in the CNS by real-time BLI and/or histological analysis in the absence of immunosuppressive therapy.

Differences in Baseline Lymphocyte Counts and Autoreactivity Are Associated With Differences in Outcome of Islet Cell Transplantation in Type 1 Diabetic Patients

OBJECTIVE The metabolic outcome of islet cell transplants in type 1 diabetic patients is variable. This retrospective analysis examines whether differences in recipient characteristics at the time of transplantation are correlated with inadequate graft function. RESEARCH DESIGN AND METHODS Thirty nonuremic C-peptide–negative type 1 diabetic patients had received an intraportal islet cell graft of comparable size under an ATG-tacrolimus–mycophenolate mofetil regimen. Baseline patient characteristics were compared with outcome parameters during the first 6 posttransplant months (i.e., plasma C-peptide, glycemic variability, and gain of insulin independence). Correlations in univariate analysis were further examined in a multivariate model. RESULTS Patients that did not become insulin independent exhibited significantly higher counts of B-cells as well as a T-cell autoreactivity against insulinoma-associated protein 2 (IA2) and/or GAD. In one of them, a liver biopsy during posttransplant year 2 showed B-cell accumulations near insulin-positive β-cell aggregates. Higher baseline total lymphocytes and T-cell autoreactivity were also correlated with lower plasma C-peptide levels and higher glycemic variability. CONCLUSIONS Higher total and B-cell counts and presence of T-cell autoreactivity at baseline are independently associated with lower graft function in type 1 diabetic patients receiving intraportal islet cells under ATG-tacrolimus–mycophenolate mofetil therapy. Prospective studies are needed to assess whether control of these characteristics can help increase the function of islet cell grafts during the first year posttransplantation.

Plasmid-based genetic modification of human bone marrow-derived stromal cells: analysis of cell survival and transgene expression after transplantation in rat spinal cord

BackgroundBone marrow-derived stromal cells (MSC) are attractive targets for ex vivo cell and gene therapy. In this context, we investigated the feasibility of a plasmid-based strategy for genetic modification of human (h)MSC with enhanced green fluorescent protein (EGFP) and neurotrophin (NT)3. Three genetically modified hMSC lines (EGFP, NT3, NT3-EGFP) were established and used to study cell survival and transgene expression following transplantation in rat spinal cord.ResultsFirst, we demonstrate long-term survival of transplanted hMSC-EGFP cells in rat spinal cord under, but not without, appropriate immune suppression. Next, we examined the stability of EGFP or NT3 transgene expression following transplantation of hMSC-EGFP, hMSC-NT3 and hMSC-NT3-EGFP in rat spinal cord. While in vivo EGFP mRNA and protein expression by transplanted hMSC-EGFP cells was readily detectable at different time points post-transplantation, in vivo NT3 mRNA expression by hMSC-NT3 cells and in vivo EGFP protein expression by hMSC-NT3-EGFP cells was, respectively, undetectable or declined rapidly between day 1 and 7 post-transplantation. Further investigation revealed that the observed in vivo decline of EGFP protein expression by hMSC-NT3-EGFP cells: (i) was associated with a decrease in transgenic NT3-EGFP mRNA expression as suggested following laser capture micro-dissection analysis of hMSC-NT3-EGFP cell transplants at day 1 and day 7 post-transplantation, (ii) did not occur when hMSC-NT3-EGFP cells were transplanted subcutaneously, and (iii) was reversed upon re-establishment of hMSC-NT3-EGFP cell cultures at 2 weeks post-transplantation. Finally, because we observed a slowly progressing tumour growth following transplantation of all our hMSC cell transplants, we here demonstrate that omitting immune suppressive therapy is sufficient to prevent further tumour growth and to eradicate malignant xenogeneic cell transplants.ConclusionIn this study, we demonstrate that genetically modified hMSC lines can survive in healthy rat spinal cord over at least 3 weeks by using adequate immune suppression and can serve as vehicles for transgene expression. However, before genetically modified hMSC can potentially be used in a clinical setting to treat spinal cord injuries, more research on standardisation of hMSC culture and genetic modification needs to be done in order to prevent tumour formation and transgene silencing in vivo.

Liver transplantation from donation after cardiac death donors: initial Belgian experience 2003–2007

The Belgian experience with donation after cardiac death (DCD) liver transplantation (LT) was retrospectively reviewed, particularly evaluating patient and graft survivals, and biliary complications. From 2003 to 2007, 58 DCD‐LT were performed in Belgium. Mean procurement total warm ischemia time was 25 ± 2 min (mean ± SEM). Mean cold ischemia time was 451 ± 18 min. Mean follow‐up was 23 ± 2.2 months. Post‐transplant peak aspartate aminotransminases was 2241 ± 338 UI/l. Patient survivals at 1 month, 1 and 3 years, were 91.3%, 83.3% and 66.9% respectively. Graft survivals at 1 month, 1 and 3 years, were 84.4%, 72.4% and 48.8% respectively. Two patients (3.4%) developed primary nonfunction. Regarding the biliary complications, seven grafts (12%) were lost because of intrahepatic cholangiopathy, and 12 other patients (20.6%) developed bile duct stenoses requiring endoscopic and/or surgical management. The rate of symptomatic ischemic biliary lesions for grafts surviving more than 3 months was 38% (19/50). Although DCD organ donors may be a source of viable liver grafts, results were inferior to those obtained with donation after brain death LT in this series. Prognostic criteria have to be developed to improve results of DCD‐LT.

Diagnostic and therapeutic double-balloon enteroscopy after small bowel Roux-en-Y reconstructive surgery.

Background: Roux-en-Y reconstruction excludes the afferent limb and the biliopancreatic system from conventional endoscopic access. Postoperative problems in these excluded gastrointestinal systems are therefore often dealt with surgically. We investigated the usefulness of the therapeutic double-balloon enteroscope to perform interventional endoscopic procedures in the excluded segment of the gastrointestinal tract after Roux-en-Y reconstruction. Methods: 30 procedures were performed in 22 patients with Roux-en-Y reconstruction after enterobiliary anastomosis, gastrectomy or bariatric gastric bypass. All procedures were performed with the therapeutic double-balloon enteroscope, under general anesthesia and with fluoroscopic control. Results: ERCP at the enterobiliary anastomosis was successful in 90% (n = 10) of the procedures. ERCP at the intact papilla was successful in 60% (n = 5). Enterocutaneous fistula closure after (sub)total gastrectomy was performed in 2 procedures. Successful diagnostic procedures encompassed intubation of the excluded stomach after bariatric gastric bypass (89%, n = 9) or the afferent limb after Roux-en-Y reconstruction (75%, n = 4). The overall success rate in accessing the aimed excluded segment with the double-balloon enteroscope was 87%. Interventional procedures were able to avoid surgery in 65%. One retroperitoneal perforation occurred during ERCP which was conservatively treated. Conclusions: Excluded gastrointestinal segments after Roux-en-Y reconstruction can be accessed with a substantial success rate using double-balloon enteroscopy. Therapeutic interventions like ERCP can prevent surgery in the majority of patients.

Dendritic cells: cellular mediators for immunological tolerance.

In general, immunological tolerance is acquired upon treatment with non-specific immunosuppressive drugs. This indiscriminate immunosuppression of the patient often causes serious side-effects, such as opportunistic infectious diseases. Therefore, the need for antigen-specific modulation of pathogenic immune responses is of crucial importance in the treatment of inflammatory diseases. In this perspective, dendritic cells (DCs) can have an important immune-regulatory function, besides their notorious antigen-presenting capacity. DCs appear to be essential for both central and peripheral tolerance. In the thymus, DCs are involved in clonal deletion of autoreactive immature T cells by presenting self-antigens. Additionally, tolerance is achieved by their interactions with T cells in the periphery and subsequent induction of T cell anergy, T cell deletion, and induction of regulatory T cells (Treg). Various studies have described, modulation of DC characteristics with the purpose to induce antigen-specific tolerance in autoimmune diseases, graft-versus-host-disease (GVHD), and transplantations. Promising results in animal models have prompted researchers to initiate first-in-men clinical trials. The purpose of current review is to provide an overview of the role of DCs in the immunopathogenesis of autoimmunity, as well as recent concepts of dendritic cell-based therapeutic opportunities in autoimmune diseases.

Allogeneic stromal cell implantation in brain tissue leads to robust microglial activation

Although adult and embryonic stem cell‐based therapy for central nervous system (CNS) injury is being developed worldwide, less attention is given to the immunological aspects of allogeneic cell implantation in the CNS. The latter is of major importance because, from a practical point of view, future stem cell‐based therapy for CNS injury will likely be performed using well‐characterised allogeneic stem cell populations. In this study, we aimed to further describe the immunological mechanism leading to rejection of allogeneic bone marrow‐derived stromal cells (BM‐SC) after implantation in murine CNS. For this, we first investigated the impact of autologous and allogeneic BM‐SC on microglia activation in vitro. Although the results indicate that both autologous and allogeneic BM‐SC do not activate microglia themselves in vitro, they also do not inhibit activation of microglia after exogenous stimuli in vitro. Next, we investigated the impact of allogeneic BM‐SC on microglia activation in vivo. In contrast to the in vitro observations, microglia become highly activated in vivo after implantation of allogeneic BM‐SC in the CNS of immune‐competent mice. Moreover, our results suggest that microglia, rather than T‐cells, are the major contributors to allograft rejection in the CNS.

Clinical potential of intravenous neural stem cell delivery for treatment of neuroinflammatory disease in mice

While neural stem cells (NSCs) are widely expected to become a therapeutic agent for treatment of severe injuries to the central nervous system (CNS), currently there are only few detailed preclinical studies linking cell fate with experimental outcome. In this study, we aimed to validate whether IV administration of allogeneic NSC can improve experimental autoimmune encephalomyelitis (EAE), a well-established animal model for human multiple sclerosis (MS). For this, we cultured adherently growing luciferase-expressing NSCs (NSC-Luc), which displayed a uniform morphology and expression profile of membrane and intracellular markers, and which displayed an in vitro differentiation potential into neurons and astrocytes. Following labeling with green fluorescent micron-sized iron oxide particles (f-MPIO-labeled NSC-Luc) or lentiviral transduction with the enhanced green fluorescent protein (eGFP) reporter gene (NSC-Luc/eGFP), cell implantation experiments demonstrated the intrinsic survival capacity of adherently cultured NSC in the CNS of syngeneic mice, as analyzed by real-time bioluminescence imaging (BLI), magnetic resonance imaging (MRI), and histological analysis. Next, EAE was induced in C57BL/6 mice followed by IV administration of NSC-Luc/eGFP at day 7 postinduction with or without daily immunosuppressive therapy (cyclosporine A, CsA). During a follow-up period of 20 days, the observed clinical benefit could be attributed solely to CsA treatment. In addition, histological analysis demonstrated the absence of NSC-Luc/eGFP at sites of neuroinflammation. In order to investigate the absence of therapeutic potential, BLI biodistribution analysis of IV-administered NSC-Luc/eGFP revealed cell retention in lung capillaries as soon as 1-min postinjection, resulting in massive inflammation and apoptosis in lung tissue. In summary, we conclude that IV administration of NSCs currently has limited or no therapeutic potential for neuroinflammatory disease in mice, and presumably also for human MS. However, given the fact that grafted NSCs have an intrinsic survival capacity in the CNS, their therapeutic exploitation should be further investigated, and—in contrast to several other reports—will most likely be highly complex.

A view on beta cell transplantation in diabetes

Abstract: Organ donors also offer a source of insulin‐producing tissue that might be used for the treatment of diabetes. Clinical protocols for transplantation of this tissue aim for the prevention of chronic diabetes complications without introducing new serious side effects. Pancreas and islet cell transplantation are discussed in this perspective. The future of islet cell implants looks favorable but depends on finding ways to induce immune tolerance to the donor beta cells. Clinical trials can take advantage of relevant progress in animal models. In a limited study, recipient treatment with antilymphocyte antibodies and culture of donor cell preparations appeared useful to induce a state of operational immune tolerance in type 1 diabetic patients, as indirectly judged by graft survival and by analysis of auto‐ and alloreactivities in recipients. Use of cultured beta cell preparations also allows donor cell recruitment from suboptimal donor organs and increases the degree of standardization and quality control of islet cell grafts. The future of these grafts will depend on the development of techniques for the neogenesis of beta cells.