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Background: Pig islet xenotransplantation is a potential treatment for type 1 diabetes. We have shown that maintenance immunosuppression is required to protect genetically modified (GM) porcine islet xenografts from T cell‐mediated rejection in baboons. Local expression of a depleting anti‐CD2 monoclonal antibody (mAb) by the xenograft may provide an alternative solution. We have previously reported the generation of GGTA1 knock‐in transgenic pigs expressing the chimeric anti‐CD2 mAb diliximab under an MHC class I promoter (MHCIP). In this study, we generated GGTA1 knock‐in pigs in which MHCIP was replaced by the β‐cell‐specific porcine insulin promoter (PIP), and compared the pattern of diliximab expression in the two lines. Methods: A PIP‐diliximab knock‐in construct was prepared and validated by transfection of NIT‐1 mouse insulinoma cells. The construct was knocked into GGTA1 in wild type (WT) porcine fetal fibroblasts using CRISPR, and knock‐in cells were used to generate pigs by somatic cell nuclear transfer (SCNT). Expression of the transgene in MHCIP‐diliximab and PIP‐diliximab knock‐in pigs was characterised at the mRNA and protein levels using RT‐qPCR, flow cytometry, ELISA and immunohistochemistry. Islets from MHCIP‐diliximab and control GGTA1 KO neonatal pigs were transplanted under the kidney capsule of streptozotocin‐diabetic SCID mice. Results: NIT‐1 cells stably transfected with the PIP‐diliximab knock‐in construct secreted diliximab into the culture supernatant, confirming correct expression and processing of the mAb in β cells. PIP‐diliximab knock‐in pigs showed a precise integration of the transgene within GGTA1. Diliximab mRNA was detected in all tissues tested (spleen, kidney, heart, liver, lung, pancreas) in MHCIP‐diliximab pigs, but was not detectable in PIP‐diliximab pigs. Likewise, diliximab was present in the serum of MHCIP‐diliximab pigs, at a mean concentration of 1.8 μg/mL, but was not detected in PIP‐diliximab pig serum. An immunohistochemical survey revealed staining for diliximab in all organs of MHCIP‐diliximab pigs but not of PIP‐diliximab pigs. Whole genome sequencing (WGS) of a PIP‐diliximab pig identified a missense mutation in the coding region for the dixilimab light chain. This mutation was also found to be present in the fibroblast knock‐in clone used to generate the PIP‐diliximab pigs. Islet xenografts from neonatal MHCIP‐diliximab pigs restored normoglycemia in diabetic immunodeficient mice, indicating no overt effect of the transgene on islet function, and demonstrated expression of diliximab in situ. Conclusion: Diliximab was widely expressed in MHCIP‐diliximab pigs, including in islets, consistent with the endogenous expression pattern of MHC class I. Further investigation is required to determine whether the level of expression in islets from the MHCIP‐diliximab pigs is sufficient to prevent T cell‐mediated islet xenograft rejection. The unexpected absence of diliximab expression in the islets of PIP‐diliximab pigs was probably due to a mutation in the transgene arising during the generation of the knock‐in cells used for SCNT. [ABSTRACT FROM AUTHOR]

Necroptosis, a pathway of regulated necrosis, involves recruitment and activation of RIPK1, RIPK3 and MLKL, leading to cell membrane rupture, cell death and release of intracellular contents causing further injury and inflammation. Necroptosis is believed to play an important role in the pathogenesis of kidney ischemia-reperfusion injury (IRI). However, the dynamics of necroptosis in kidney IRI is poorly understood, in part due to difficulties in detecting phosphorylated MLKL (pMLKL), the executioner of the necroptosis pathway. Here, we investigated the temporal and spatial activation of necroptosis in a mouse model of unilateral warm kidney IRI, using a robust method to stain pMLKL. We identified the period 3-12 hrs after reperfusion as a critical phase for the activation of necroptosis in proximal tubular cells. After 12 hrs, the predominant pattern of pMLKL staining shifted from cytoplasmic to membrane, indicating progression to the terminal phase of necroptotic cell death. Mlkl-ko mice exhibited reduced kidney inflammation at 12 hrs and lower serum creatinine and tubular injury at 24 hrs compared to wild-type littermates. Interestingly, we observed increased apoptosis in the injured kidneys of Mlkl-ko mice, suggesting a relationship between necroptosis and apoptosis in kidney IRI. Together, our findings confirm the role of necroptosis and necroinflammation in kidney IRI, and identify the first 3 hrs following reperfusion as a potential window for targeted treatments. [ABSTRACT FROM AUTHOR]

Transplantation of human embryonic stem cell (ESC) derived beta‐like cells and xenotransplantation of porcine islets are two potential cures for type 1 diabetes (T1D). We have previously reported the isolation of porcine ESCs and have also separately shown that islets from genetically modified pigs can effectively cure diabetes in a preclinical baboon model. Here we discuss the possibility of combining these technologies to produce gene‐edited porcine ESC‐derived islets as an alternative for treating T1D, which may offer several advantages compared with these approaches. [ABSTRACT FROM AUTHOR]

Extracellular purine nucleotides and nucleosides released from activated or injured cells influence multiple aspects of cardiac physiology and pathophysiology. Ectonucleoside triphosphate diphosphohydrolase-1 (ENTPD1; CD39) hydrolyzes released nucleotides and thereby regulates the magnitude and duration of purinergic signaling. However, the impact of CD39 activity on post-myocardial infarction (MI) remodeling is incompletely understood. We measured the levels and activity of ectonucleotidases in human left ventricular samples from control and ischemic cardiomyopathy (ICM) hearts and examined the impact of ablation of Cd39 expression on post-myocardial infarction remodeling in mice. We found that human CD39 levels and activity are significantly decreased in ICM hearts (n = 5) compared with control hearts (n = 5). In mice null for Cd39, cardiac function and remodeling are significantly compromised in Cd39−/−mice following myocardial infarction. Fibrotic markers including plasminogen activator inhibitor-1 (PAI-1) expression, fibrin deposition, α-smooth muscle actin (αSMA), and collagen expression are increased in Cd39−/−hearts. Importantly, we found that transforming growth factor β1 (TGF-β1) stimulates ATP release and induces Cd39 expression and activity on cardiac fibroblasts, constituting an autocrine regulatory pathway not previously appreciated. Absence of CD39 activity on cardiac fibroblasts exacerbates TGF-β1 profibrotic responses. Treatment with exogenous ectonucleotidase rescues this profibrotic response in Cd39−/− fibroblasts. Together, these data demonstrate that CD39 has important interactions with TGF-β1-stimulated autocrine purinergic signaling in cardiac fibroblasts and dictates outcomes of cardiac remodeling following myocardial infarction. Our results reveal that ENTPD1 (CD39) regulates TGF-β1-mediated fibroblast activation and limits adverse cardiac remodeling following myocardial infarction. NEW & NOTEWORTHY We show that CD39 is a critical modulator of TGF-β1-mediated fibroblast activation and cardiac remodeling following myocardial infarction via modulation of nucleotide signaling. TGF-β1-induced CD39 expression generates a negative feedback loop that attenuates cardiac fibroblast activation. In the absence of CD39 activity, collagen deposition is increased, elastin expression is decreased, and diastolic dysfunction is worsened. Treatment with ecto-apyrase attenuates the TGF-β1-induced profibrotic cardiac fibroblast phenotype, revealing a novel approach to combat post-myocardial infarction cardiac fibrosis. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Introduction: After orthotopic cardiac xenotransplantation, the combination of both the inflammatory responses to the exposure of a recipient to the xenogeneic organ and the use of cardiopulmonary bypass has been assumed to cause detrimental side effects. These have been described not only to affect the transplanted organ (heart) itself, but also the recipient's lungs. In this article, we summarize how these possible detrimental processes can be minimized or even avoided. Methods: Data from eight pig‐to‐baboon orthotopic cardiac xenotransplantation experiments were analyzed with a special focus on early (within the first week) postoperative organ dysfunction and systemic inflammatory responses. Non‐ischemic heart preservation and the careful management of the heart‐lung machine were deemed essential to guarantee not only the immediate function of the transplanted xenogeneic organ but also the prompt recovery of the recipient. Results: After weaning from cardiopulmonary bypass, very low catecholamine amounts were needed to ensure an adequate pump function and cardiac output. Central venous oxygen saturation and serum lactate levels remained within normal ranges. All animals were successfully weaned from ventilation within the first postoperative hours. Serum parameters of the transplants and native kidneys and livers were initially slightly elevated or always normal, as were hemoglobin, LDH, and platelet measurements. Markers of systemic inflammation, C‐reactive protein, and IL‐6 were slightly elevated, but the reactions caused no lasting damage. Conclusion: Consistent short‐term and long‐term results were achieved after orthotopic cardiac pig‐to‐baboon transplantation without detrimental inflammatory responses or signs of multiorgan failure. In comparison to allogeneic procedures, non‐ischemic heart preservation was important for successful immediate organ function, as was the management of the heart‐lung machine. Thus, we believe that genetically modified porcine hearts are ready for use in the clinical setting. [ABSTRACT FROM AUTHOR]

A number of reviews have been written recently celebrating the 25th anniversary of the birth of Dolly the cloned sheep and the effect this breakthrough has had on various fields of research. However, arguably the biggest impact Dolly has had is on the field of xenotransplantation, described here based on our own experience and that of others. [ABSTRACT FROM AUTHOR]