Marta Vadori

In vitro and in vivo effects of the carbon monoxide-releasing molecule, CORM-3, in the xenogeneic pig-to-primate context.

Abstract: Background:  Carbon monoxide (CO) interferes with inflammatory and apoptotic processes associated with ischemia–reperfusion injury and graft rejection. Here, the in vitro effects of carbon monoxide releasing molecule‐3 (CORM‐3), a novel water‐soluble carbonyl CO carrier, have been investigated on porcine aortic endothelial cells (PAEC) and primate peripheral blood mononuclear cells (PBMC). Furthermore, the pharmacodynamics and pharmacotolerance of CORM‐3 after administration of single and multiple doses in the primate have been assessed in view of its potential application in pig‐to‐primate xenotransplantation models.

Cell Therapy for Parkinson's Disease: A Translational Approach to Assess the Role of Local and Systemic Immunosuppression

Neural transplantation is a promising therapeutic approach for neurodegenerative diseases; however, many patients receiving intracerebral fetal allografts exhibit signs of immunization to donor antigens that could compromise the graft. In this context, we intracerebrally transplanted mesencephalic pig xenografts into primates to identify a suitable strategy to enable long‐term cell survival, maturation, and differentiation. Parkinsonian primates received WT or CTLA4‐Ig transgenic porcine xenografts and different durations of peripheral immunosuppression to test whether systemic plus graft‐mediated local immunosuppression might avoid rejection. A striking recovery of spontaneous locomotion was observed in primates receiving systemic plus local immunosuppression for 6 mo. Recovery was associated with restoration of dopaminergic activity detected both by positron emission tomography imaging and histological examination. Local infiltration by T cells and CD80/86+ microglial cells expressing indoleamine 2,3‐dioxigenase were observed only in CTLA4‐Ig recipients. Results suggest that in this primate neurotransplantation model, peripheral immunosuppression is indispensable to achieve the long‐term survival of porcine neuronal xenografts that is required to study the beneficial immunomodulatory effect of local blockade of T cell costimulation.

Immunological Challenges and Therapies in Xenotransplantation

Xenotransplantation, or the transplantation of cells, tissues, or organs between different species, was proposed a long time ago as a possible solution to the worldwide shortage of human organs and tissues for transplantation. In this setting, the pig is currently seen as the most likely candidate species. In the last decade, progress in this field has been remarkable and includes a better insight into the immunological mechanisms underlying the rejection process. Several immunological hurdles nonetheless remain, such as the strong antibody-mediated and innate or adaptive cellular immune responses linked to coagulation derangements, precluding indefinite xenograft survival. This article reviews our current understanding of the immunological mechanisms involved in xenograft rejection and the potential strategies that may enable xenotransplantation to become a clinical reality in the not-too-distant future.

Clinicopathological findings in non-human primate recipients of porcine renal xenografts: quantitative and qualitative evaluation of proteinuria.

Immunological and histopathological features in pig‐to‐primate renal xenotransplantation are widely studied. Only limited data have been reported about clinicopathological findings in primate recipients of life‐supporting renal xenografts. In human medicine, proteinuria represents a common complication in kidney transplantation and is associated with impaired graft survival. The detection of low molecular weight proteins of tubular origin is considered an early method for predicting potential graft rejection. In this study, the presence and the significance of quantitative and qualitative proteinuria were evaluated in xenotransplanted non‐human primates in which kidney function was supported only by the transplanted organ.

Translational research for Parkinson׳s disease: The value of pre-clinical primate models.

Animal models have been highly questioned for their ability to predict the efficacy of different therapeutic strategies for neurodegenerative diseases. The increasing number of phase I/II clinical trials that fail to proceed to further stages of drug development has discredited the pertinence of such investigations. However, critical analysis of the data has often revealed errors and partially explained the lack of efficacy, opening the way to a refinement in designing pre-clinical studies. In parallel, many promising methods of drug delivery to the brain such as gene therapy or cell therapy have considerably advanced thanks to the clinical failures in the past 10 years. As methodological advances appear and knowledge becomes available, scientists will be faced with the choice of how to test new strategies or re-test old ones. With the hardening of social views and legislation regarding animal experimentation, there is increasing pressure to find alternative methods of assessment that predict efficacy (such as computational based models), or to perform efficacy trials directly in patients and only safety assays in animals. In this review we will focus on Parkinson׳s disease and on the impact of a body of data issued from NHP studies. We will attempt to critically examine the advantages and limitations of various approaches from the perspective of the animal model used to address specific questions.

High viral frequency in children with gastroesophageal reflux-related chronic respiratory disorders.

In the pediatric population chronic respiratory disorders (CRDs) include many pathological entities in which gastroesophageal reflux (GER) may play a role in the induction or persistence of clinical symptoms. It is not well established whether infective agents may be present in lung aspiration. The aim of the work was to investigate whether different infective agents could be found in children with GER‐related CRDs.

Thromboelastographic evaluation of coagulative profiles in pig-to-monkey kidney xenotransplantation.

Activation of the clotting cascade is central in acute xenograft rejection (AHXR) that occurs when pig organs are transplanted into primates. The coagulopathy reported in this model is a very complex process that involves simultaneously coagulation factors, platelets and phospholipid‐bearing cells (i.e., leukocytes, red blood cells, and endothelial cells). Choosing whole blood for coagulation analysis theoretically appears more favorable compared with plasma. Whole blood rotation thromboelastometry (ROTEM®) is a point‐of‐care global coagulation analyzer able to evaluate the characteristics of clot formation and lysis by dynamic monitoring. The aim of this study was to record thromboelastographic profiles, performed by ROTEM®, in a series of immunosuppressed nephrectomized primates that received a life‐supporting kidney.

In vitro and in vivo immunomodulatory effects of cobalt protoporphyrin administered in combination with immunosuppressive drugs.

BACKGROUND Immunosuppressive strategies are designed to take advantage of potential synergies between drugs to possibly decrease the risk of side-effects. In the present study, the ability of Cobalt protoporphyrin (CoPP) to potentiate the effect of the immunosuppressive drugs mycophenolate sodium (MPS) or cyclosporin A (CsA) was explored in vitro and in vivo. METHODS In vitro analyses of proliferation and apoptosis were performed on primate T cell cultures, following incubation with the immunosuppressive drugs MPS or CsA, alone or in combination with CoPP. In vivo the effect of CoPP and CsA combination therapy was assessed in a rat heterotopic cardiac allotransplantation model. RESULTS In vitro results suggest that co-administration of CoPP with CsA or MPS increases immunosuppressive effects of these drugs when combined with CoPP. In particular, the co-administration of CoPP with CsA resulted in the synergistic induction of lymphocyte apoptosis. In vivo, animals immunosuppressed with CsA (1.5 mg/kg) or CoPP (20 mg/kg) alone, had a median survival of 7 or 8 days, respectively. In contrast, animals immunosuppressed with CsA (1.5 mg/kg) combined with CoPP (20 mg/kg) had significantly prolonged median survival (12 days), compared to recipients treated with CsA or CoPP alone (p<0.05). CONCLUSION Our in vitro and in vivo studies demonstrate that CoPP can potentiate the immunomodulatory effects of CsA, ultimately extending allograft survival.

Expression of recipient cytomegalovirus in immunosuppressed and xenotransplanted Macaca fascicularis may be related to more severe gastrointestinal lesions

Xenotransplantation is a potential answer to the current organ shortage, but the risk of infections related to overimmunosuppression is an important parameter that may predict the recipients long‐term survival. Cytomegalovirus (CMV) in xenotransplanted and immunosuppressed primates is a well‐known cause of disease particularly affecting the gastrointestinal (GI) tract and a zoonotic concern.

Current status of neuronal cell xenotransplantation

Neural cell transplantation has long been considered as an option for the treatment of neurodegenerative disorders. To date, several patients with Parkinsons and Huntingtons diseases have been treated with human fetal-derived neurons with disparate results. However, the limited efficacy to date combined with the scarce availability of human fetal tissues and ethical concerns render this procedure inapplicable to a wide population scale. With a view to overcoming these shortcomings, transplantation of pig-derived cell precursors has been proposed and applied in preclinical and clinical trials. Recently long-term survival (more than 18 months) associated with clinical efficacy has been reported following transplantation of genetically engineered porcine neural precursors in fully immunosuppressed primate recipients. Despite the promising results obtained to date, several questions remain unanswered. In particular, the ideal xenogeneic cell-products to transplant, the extent of the immune response against the implanted xenograft and the most suitable therapeutic strategies to improve engraftment are all issues that still need to be thoroughly addressed. The present review describes the current knowledge in the pig-to-primate xenotransplantation field. In this context, recent data on human-to-nonhuman primate xenogeneic stem cell-based treatments for neurological disorders are discussed.