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Chaban R, Habibabady Z, Hassanein W, Connolly MR, Burdorf L, Redding E, Laird C, Ranek J, Braileanu G, Sendil S, Cheng X, Sun W, O’Neill NA, Kuravi K, Hurh S, Ayares DL, Azimzadeh AM, Pierson RN. Knock-out of N-glycolylneuraminic acid attenuates antibody-mediated rejection in xenogenically perfused porcine lungs. Xenotransplantation 2022; 29:e12784. [PMID: 36250568 PMCID: PMC11093624 DOI: 10.1111/xen.12784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 07/27/2022] [Accepted: 09/13/2022] [Indexed: 01/15/2023]
Abstract
BACKGROUND Antibody-mediated rejection has long been known to be one of the major organ failure mechanisms in xenotransplantation. In addition to the porcine α1,3-galactose (α1,3Gal) epitope, N-Glycolylneuraminic acid (Neu5Gc), a sialic acid, has been identified as an important porcine antigen against which most humans have pre-formed antibodies. Here we evaluate GalTKO.hCD46 lungs with an additional cytidine monophospho-N-acetylneuraminic acid hydroxylase (CMAH) gene knock-out (Neu5GcKO) in a xenogeneic ex vivo perfusion model METHODS: Eleven GalTKO.hCD46.Neu5GcKO pig lungs were perfused for up to 6 h with fresh heparinized human blood. Six of them were treated with histamine (H) blocker famotidine and 1-thromboxane synthase inhibitor Benzylimidazole (BIA) and five were left untreated. GalTKO.hCD46 lungs without Neu5GcKO (n = 18: eight untreated and 10 BIA+H treated) served as a reference. Functional parameters, blood, and tissue samples were collected at pre-defined time points throughout the perfusion RESULTS: All but one Neu5GcKO organs maintained adequate blood oxygenation and "survived" until elective termination at 6 h whereas two reference lungs failed before elective termination at 4 h. Human anti-Neu5Gc antibody serum levels decreased during the perfusion of GalTKO.hCD46 lungs by flow cytometry (∼40% IgM, 60% IgG), whereas antibody levels in Neu5GcKO lung perfusions did not fall (IgM p = .007; IgG p < .001). Thromboxane elaboration, thrombin generation, and histamine levels were significantly reduced with Neu5GcKO lungs compared to reference in the untreated groups (p = .007, .005, and .037, respectively); treatment with BIA+H masked these changes. Activation of platelets, measured as CD62P expression on circulating platelets, was lower in Neu5GcKO experiments compared to reference lungs (p = .023), whereas complement activation (as C3a rise in plasma) was not altered. MCP-1 and lactotransferin level elevations were blunted in Neu5GcKO lung perfusions (p = .007 and .032, respectively). Pulmonary vascular resistance (PVR) rise was significantly attenuated and delayed in untreated GalTKO.hCD46.Neu5GcKO lungs in comparison to the untreated GalTKO.hCD46 lungs (p = .003) CONCLUSION: Additional Neu5GcKO in GalTKO.hCD46 lungs significantly reduces parameters associated with antibody-mediated inflammation and activation of the coagulation cascade. Knock-out of the Neu5Gc sialic acid should be beneficial to reduce innate immune antigenicity of porcine lungs in future human recipients.
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Affiliation(s)
- Ryan Chaban
- Center for Transplantation Sciences and Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
- Department of Cardiovascular Surgery, University Hospital of Mainz, Mainz, Germany
| | - Zahra Habibabady
- Center for Transplantation Sciences and Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Wessam Hassanein
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Margaret R. Connolly
- Center for Transplantation Sciences and Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Lars Burdorf
- Center for Transplantation Sciences and Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
- Revivicor, Inc., Blacksburg, Virgina, USA
| | - Emily Redding
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Christopher Laird
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Jolene Ranek
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Gheorghe Braileanu
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Selin Sendil
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Xiangfei Cheng
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Wenji Sun
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Natalie A. O’Neill
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | | | - Sunghoon Hurh
- Department of Biomedical Sciences, Korea University College of Medicine, Seoul, Korea
| | | | - Agnes M. Azimzadeh
- Center for Transplantation Sciences and Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Richard N. Pierson
- Center for Transplantation Sciences and Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
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Petitpas K, Habibabady Z, Ritchie V, Connolly MR, Burdorf L, Qin W, Kan Y, Layer JV, Crabtree JN, Youd ME, Westlin WF, Magnani DM, Pierson RN, Azimzadeh AM. Genetic modifications designed for xenotransplantation attenuate sialoadhesin-dependent binding of human erythrocytes to porcine macrophages. Xenotransplantation 2022; 29:e12780. [PMID: 36125388 PMCID: PMC10152518 DOI: 10.1111/xen.12780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2022] [Revised: 08/11/2022] [Accepted: 09/01/2022] [Indexed: 01/15/2023]
Abstract
The phenomenon of diminishing hematocrit after in vivo liver and lung xenotransplantation and during ex vivo liver xenoperfusion has largely been attributed to action by resident liver porcine macrophages, which bind and destroy human erythrocytes. Porcine sialoadhesin (siglec-1) was implicated previously in this interaction. This study examines the effect of porcine genetic modifications, including knockout of the CMAH gene responsible for expression of Neu5Gc sialic acid, on the adhesion of human red blood cells (RBCs) to porcine macrophages. Wild-type (WT) porcine macrophages and macrophages from several strains of genetically engineered pigs, including CMAH gene knockout and several human transgenes (TKO+hTg), were incubated with human RBCs and "rosettes" (≥3 erythrocytes bound to one macrophage) were quantified by microscopy. Our results show that TKO+hTg genetic modifications significantly reduced rosette formation. The monoclonal antibody 1F1, which blocks porcine sialoadhesin, significantly reduced rosette formation by WT and TKO+hTg macrophages compared with an isotype control antibody. Further, desialation of human RBCs with neuraminidase before addition to WT or TKO+hTg macrophages resulted in near-complete abrogation of rosette formation, to a level not significantly different from porcine RBC rosette formation on porcine macrophages. These observations are consistent with rosette formation being mediated by binding of sialic acid on human RBCs to sialoadhesin on porcine macrophages. In conclusion, the data predict that TKO+hTg genetic modifications, coupled with targeting of porcine sialoadhesin by the 1F1 mAb, will attenuate erythrocyte sequestration and anemia during ex vivo xenoperfusion and following in vivo liver, lung, and potentially other organ xenotransplantation.
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Affiliation(s)
- Kaitlyn Petitpas
- MGH, Center for Transplantation Sciences, Boston, Massachusetts, USA
| | - Zahra Habibabady
- MGH, Center for Transplantation Sciences, Boston, Massachusetts, USA
| | - Veronica Ritchie
- MGH, Center for Transplantation Sciences, Boston, Massachusetts, USA
| | | | - Lars Burdorf
- MGH, Center for Transplantation Sciences, Boston, Massachusetts, USA
| | - Wenning Qin
- eGenesis Inc., Cambridge, Massachusetts, USA
| | - Yinan Kan
- eGenesis Inc., Cambridge, Massachusetts, USA
| | | | | | | | | | | | - Richard N Pierson
- MGH, Center for Transplantation Sciences, Boston, Massachusetts, USA
| | - Agnes M Azimzadeh
- MGH, Center for Transplantation Sciences, Boston, Massachusetts, USA
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Immune disguise: the mechanisms of Neu5Gc inducing autoimmune and transplant rejection. Genes Immun 2022; 23:175-182. [PMID: 36151402 DOI: 10.1038/s41435-022-00182-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2022] [Revised: 08/16/2022] [Accepted: 09/05/2022] [Indexed: 11/08/2022]
Abstract
Organ (stem cell) transplantation is the most effective treatment for advanced organ failure. Neu5Gc (N-hydroxyacetylneuraminic acid) is a pathogenic non-human sialic acid, which is very similar to the molecular structure of Neu5Ac (N-acetylneuraminic acid) in human body. Neu5Gc has the function of "immune disguise", which is the main obstacle to transplantation. Gene knockout such as cytidine monophosphate-N-acetylneuraminidase (CMAH) reduces donor antigenicity, making xenotransplantation from fiction to reality. Exploring the immune disguise event in this emerging field has become a hot topic in the research of transplantation immune tolerance mechanism.
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Cimeno A, Kuravi K, Sorrells L, Dandro A, Sendil S, Burdorf L, Parsell DM, Eyestone W, Phelps C, Ayares D, Azimzadeh AM, Pierson RN, Barth RN, LaMattina JC. hEPCR.hTBM.hCD47.hHO-1 with donor clodronate and DDAVP treatment improves perfusion and function of GalTKO.hCD46 porcine livers perfused with human blood. Xenotransplantation 2022; 29:e12731. [PMID: 35166407 PMCID: PMC10249003 DOI: 10.1111/xen.12731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 07/15/2021] [Accepted: 01/12/2022] [Indexed: 11/29/2022]
Abstract
INTRODUCTION Platelet sequestration, inflammation, and inappropriate coagulation cascade activation are prominent in liver xenotransplant models and are associated with poor outcomes. Here, we evaluate a cassette of six additional genetic modifications to reduce anti-pig antibody binding (α-1,3-galactosyl transferase knockout [GalTKO]) and target coagulation dysregulation (human endothelial protein C receptor [hEPRC] and thrombomodulin [hTBM]), complement pathway regulation (human membrane cofactor protein, hCD46), inflammation heme oxygenase 1 [hHO-1]), and a self-recognition receptor (integrin-associated protein [hCD47]), as well as donor pharmacologic treatments designed to blunt these phenomena. METHODS Livers from GaltKO.hCD46 pigs ("2-gene," n = 3) and GalTKO.hCD46 pigs also transgenic for hEPRC, hTBM, hCD47, and hHO-1 ("6-gene," n = 4) were perfused ex vivo with whole human blood. Six-gene pigs were additionally pretreated with desmopressin (DDAVP) and clodronate liposomes to deplete vWF and kupffer cells, respectively. RESULTS The average perfusion times increased from 304 (±148) min in the 2-gene group to 856 (±61) min in the 6-gene group (p = .010). The average heparin administration was decreased from 8837 U/h in the 2-gene to 1354 U/h in the 6-gene group (p = .047). Platelet sequestration tended to be delayed in the 6-gene group (p = .070), while thromboxane B2 (TXB2, a platelet activation marker) levels were lower over the first hour (p = .044) (401 ± 124 vs. 2048 ± 712 at 60 min). Thrombin production as measured by F1+2 levels tended to be lower in the 6-gene group (p = .058). CONCLUSIONS The combination of the hEPCR.hTBM.hCD47.hHO-1 cassette along with donor pig DDAVP and clodronate liposome pretreatment was associated with prolonged function of xenoperfused livers, reduced coagulation pathway perturbations, and decreased TXB2 elaboration, and reflects significant progress to modulate liver xenograft injury in a pig to human model.
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Affiliation(s)
- Arielle Cimeno
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | | | | | - Amy Dandro
- Revivicor, Inc., Blacksburg, Virginia, USA
| | - Selin Sendil
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Lars Burdorf
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
- Division of Cardiac Surgery, Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Dawn M. Parsell
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | | | | | | | - Agnes M. Azimzadeh
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
- Division of Cardiac Surgery, Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Richard N. Pierson
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
- Division of Cardiac Surgery, Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Rolf N. Barth
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - John C. LaMattina
- Department of Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
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Habibabady ZA, Sendil S, Ellett F, Pollok F, Elias GF, French BM, Sun W, Braileanu G, Burdorf L, Irimia D, Pierson RN, Azimzadeh AM. Human erythrocyte fragmentation during ex-vivo pig organ perfusion. Xenotransplantation 2022; 29:e12729. [PMID: 35112383 PMCID: PMC8995366 DOI: 10.1111/xen.12729] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 12/22/2021] [Accepted: 01/10/2022] [Indexed: 01/25/2023]
Abstract
Platelet sequestration is a common process during organ reperfusion after transplantation. However, instead of lower platelet counts, when using traditional hemocytometers and light microscopy, we observed physiologically implausible platelet counts in the course of ex-vivo lung and liver xenograft organ perfusion studies. We employed conventional flow cytometry (FC) and imaging FC (AMINS ImageStream X) to investigate the findings and found platelet-sized fragments in the circulation that are mainly derived from red blood cell membranes. We speculate that this erythrocyte fragmentation contributes to anemia during in-vivo organ xenotransplant.
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Affiliation(s)
- Zahra A. Habibabady
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD,Center for Transplantation Sciences and Department of Surgery, Massachusetts General Hospital and Harvard School of Medicine, Boston, MA
| | - Selin Sendil
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD
| | - Felix Ellett
- Center for Engineering in Medicine and Surgery, Massachusetts General Hospital, Harvard School of Medicine, and Shriners Burns Hospital, Boston, MA
| | - Franziska Pollok
- Center for Transplantation Sciences and Department of Surgery, Massachusetts General Hospital and Harvard School of Medicine, Boston, MA,Department of Anesthesiology, University Hospital Hamburg-Eppendorf, Hamburg, Germany
| | - Gabriela F. Elias
- Center for Transplantation Sciences and Department of Surgery, Massachusetts General Hospital and Harvard School of Medicine, Boston, MA
| | - Beth M. French
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD
| | - Wenji Sun
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD
| | - Gheorghe Braileanu
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD
| | - Lars Burdorf
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD,Center for Transplantation Sciences and Department of Surgery, Massachusetts General Hospital and Harvard School of Medicine, Boston, MA
| | - Daniel Irimia
- Center for Engineering in Medicine and Surgery, Massachusetts General Hospital, Harvard School of Medicine, and Shriners Burns Hospital, Boston, MA
| | - Richard N. Pierson
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD,Center for Transplantation Sciences and Department of Surgery, Massachusetts General Hospital and Harvard School of Medicine, Boston, MA
| | - Agnes M. Azimzadeh
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD,Center for Transplantation Sciences and Department of Surgery, Massachusetts General Hospital and Harvard School of Medicine, Boston, MA
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Lamm V, Ekser B, Vagefi PA, Cooper DK. Bridging to Allotransplantation-Is Pig Liver Xenotransplantation the Best Option? Transplantation 2022; 106:26-36. [PMID: 33653996 PMCID: PMC10124768 DOI: 10.1097/tp.0000000000003722] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In the past 20 y, the number of patients in the United States who died while waiting for a human donor liver totaled >52 000. The median national wait time for patients with acute liver failure and the most urgent liver transplant listing was 7 d in 2018. The need for a clinical "bridge" to allotransplantation is clear. Current options for supporting patients with acute liver failure include artificial liver support devices, extracorporeal liver perfusion, and hepatocyte transplantation, all of which have shown mixed results with regard to survival benefit and are largely experimental. Progress in the transplantation of genetically engineered pig liver grafts in nonhuman primates has grown steadily, with survival of the pig graft extended to almost 1 mo in 2017. Further advances may justify consideration of a pig liver transplant as a clinical bridge to allotransplantation. We provide a brief history of pig liver xenotransplantation, summarize the most recent progress in pig-to-nonhuman primate liver transplantation models, and suggest criteria that may be considered for patient selection for a clinical trial of bridging by genetically engineered pig liver xenotransplantation to liver allotransplantation.
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Affiliation(s)
- Vladimir Lamm
- Division of Gastroenterology, Department of Medicine, Washington University School of Medicine, St. Louis, MO
| | - Burcin Ekser
- Division of Transplant Surgery, Department of Surgery, Indiana University School of Medicine, Indianapolis, IN
| | - Parsia A. Vagefi
- Division of Surgical Transplantation, Department of Surgery, University of Texas Southwestern Medical Center, Dallas, TX
| | - David K.C. Cooper
- Xenotransplantation Program, Department of Surgery, University of Alabama at Birmingham, Birmingham, AL
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Connolly MR, Kuravi K, Burdorf L, Sorrells L, Morrill B, Cimeno A, Vaught T, Dandro A, Sendil S, Habibabady ZA, Monahan J, Li T, LaMattina J, Eyestone W, Ayares D, Phelps C, Azimzadeh AM, Pierson RN. Humanized von Willebrand factor reduces platelet sequestration in ex vivo and in vivo xenotransplant models. Xenotransplantation 2021; 28:e12712. [PMID: 34657336 PMCID: PMC10266522 DOI: 10.1111/xen.12712] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 08/05/2021] [Accepted: 09/07/2021] [Indexed: 01/14/2023]
Abstract
The transplantation of organs across species offers the potential to solve the shortage of human organs. While activation of human platelets by human von Willebrand factor (vWF) requires vWF activation by shear stress, contact between human platelets and porcine vWF (pvWF) leads to spontaneous platelet adhesion and activation. This non-physiologic interaction may contribute to the thrombocytopenia and coagulation pathway dysregulation often associated with xenotransplantation of pig organs in nonhuman primates. Pigs genetically modified to decrease antibody and complement-dependent rejection (GTKO.hCD46) were engineered to express humanized pvWF (h*pvWF) by replacing a pvWF gene region that encodes the glycoprotein Ib-binding site with human cDNA orthologs. This modification corrected for non-physiologic human platelet aggregation on exposure to pig plasma, while preserving in vitro platelet activation by collagen. Organs from pigs with h*pvWF demonstrated reduced platelet sequestration during lung (p ≤ .01) and liver (p ≤ .038 within 4 h) perfusion ex vivo with human blood and after pig-to-baboon lung transplantation (p ≤ .007). Residual platelet sequestration and activation were not prevented by the blockade of canonical platelet adhesion pathways. The h*pvWF modification prevents physiologically inappropriate activation of human or baboon platelets by porcine vWF, addressing one cause of the thrombocytopenia and platelet activation observed with xenotransplantation.
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Affiliation(s)
- Margaret R Connolly
- Massachusetts General Hospital, Center for Transplantation Sciences, Boston, Massachusetts, USA
| | | | - Lars Burdorf
- Massachusetts General Hospital, Center for Transplantation Sciences, Boston, Massachusetts, USA
- University of Maryland School of Medicine, Baltimore, Maryland, USA
| | | | | | - Arielle Cimeno
- University of Maryland School of Medicine, Baltimore, Maryland, USA
| | | | | | - Selin Sendil
- University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Zahra A Habibabady
- Massachusetts General Hospital, Center for Transplantation Sciences, Boston, Massachusetts, USA
- University of Maryland School of Medicine, Baltimore, Maryland, USA
| | | | - Tiezheng Li
- University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - John LaMattina
- University of Maryland School of Medicine, Baltimore, Maryland, USA
| | | | | | | | - Agnes M Azimzadeh
- Massachusetts General Hospital, Center for Transplantation Sciences, Boston, Massachusetts, USA
- University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Richard N Pierson
- Massachusetts General Hospital, Center for Transplantation Sciences, Boston, Massachusetts, USA
- University of Maryland School of Medicine, Baltimore, Maryland, USA
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Profiling Human CD55 Transgene Performance Assist in Selecting Best Suited Specimens and Tissues for Swine Organ Xenotransplantation. BIOLOGY 2021; 10:biology10080747. [PMID: 34439979 PMCID: PMC8389641 DOI: 10.3390/biology10080747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 07/28/2021] [Accepted: 07/30/2021] [Indexed: 11/17/2022]
Abstract
Simple Summary The unbalance between availability and needs of human organs has drawn researchers’ attention to xenotransplantation as an option to cope with this shortage. Pig organs have received substantial attention for being comparable to human’s; nevertheless, compatibility constrains still block clinical applications. Transgenesis of human complement regulatory proteins, including the CD55 gene and its product the decay-accelerating factor (DAF), has been proposed to overcome xenorejection. This line of research has obtained interesting results along the years; however, most works assessing the impact of this strategy for xenotransplantation are limited to analyzing gene expression and assessing resistance to conventional serum challenge hemolysis assays, which provide somewhat reduced information prior to surgery. In this work, we tried to expand the analysis of the hCD55 transgene performance beyond common practice and into a better molecular understanding of its impact in xenotransplantation. We determined hCD55 gene expression, as well as hDAF protein presence, in different organs from five transgenic pigs, comparing readings from organs worthy for transplantation and other non-valuable organs and tissues. We also assessed the ability of transgenic cells, compared to non-transgenic, to withstand hemolysis and cytolysis. Finally, we made an effort to establish potential correlations between the hCD55 mRNA and hDAF protein levels detected. Abstract Xenotransplantation of pig organs receives substantial attention for being comparable to human’s. However, compatibility constraints involving hyper-acute rejection (HAR) still block clinical applications. Transgenesis of human complement regulatory proteins has been proposed to overcome xenorejection. Pigs expressing human-CD55 have been widely tested in experimental surgery. Still, no standardized method has been developed to determine tissue expression of human decay-accelerating factor (DAF), hCD55’s product, or to predict the ability to overpass HAR. Here we describe objective procedures addressing this need. Organs and tissues from five hCD55 transgenic pigs were collected and classified according to their xenotransplantation value. The ability to overcome HAR was assessed by classical complement pathway hemolysis assays. Quantitative PCR mRNA expression and Western blot protein level studies were performed. Real-time cytotoxicity assays (RTCA) on fibroblast cultures exposed to baboon and human sera informed on longer-term rejection dynamics. While greater hCD55/DAF expression correlated with better performance, the results obtained varied among specimens. Interestingly, the individual with highest mRNA and protein levels showed positive feedback for hCD55 transcript after challenge with human and baboon sera. Moreover, hCD55 expression correlated to DAF levels in the liver, lung and intestine, but not in the heart. Moreover, we found significant correlations among valuable and non-valuable tissues. In sum, the methodology proposed allows us to characterize the hCD55 transgene functioning and performance. Moreover, the correlations found could allow us to predict hCD55/DAF expression in surrogate tissues, thus eliminating the need for direct biopsies, resulting in preservation of organ integrity before xenotransplantation.
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Li T, Lv Y, Sun R, Yang YG, Hu Z, Lv G. Incompatibility between recipient CD47 and donor SIRPα is not a key risk factor for thrombocytopenia or anemia following rat liver xenotransplantation in mice. Xenotransplantation 2020; 28:e12657. [PMID: 33111471 DOI: 10.1111/xen.12657] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 08/10/2020] [Accepted: 10/13/2020] [Indexed: 12/31/2022]
Abstract
Liver xenotransplantation (LXT) is greatly impeded by severe thrombocytopenia, anemia, and coagulopathy. Hepatic phagocytic cells are thought to play an important role in LXT-induced thrombocytopenia and anemia. In this study, we investigated whether the lack of recipient CD47-donor SIRPα interaction, which is known to induce xenograft rejection by macrophages, exacerbates platelet and RBC depletion following LXT. We first addressed this question in the absence of anti-donor immune responses using a syngeneic mouse liver transplantation (LT) model. Neither wild-type (WT) nor CD47KO B6 mice developed thrombocytopenia following LT from WT B6 donors. Although a moderate decline in RBCs was detected following LT, there was no significant difference in RBC counts between WT and CD47KO recipients. Because mouse CD47 is cross-reactive with rat SIRPα, we then compared thrombocytopenia and anemia between WT and CD47KO mice following rat LXT. Unlike syngeneic mouse LT, significant thrombocytopenia and anemia were detected following rat LXT. However, the severities of both platelet and RBC depletions were comparable between WT and CD47KO recipients. Furthermore, WT and CD47KO recipients showed a similar extent of early platelet activation. Our results indicate that CD47-SIRPα signaling does not significantly affect the loss of platelets or RBCs following LXT, suggesting that the limited cross-reactivity between recipient CD47 and donor SIRPα is not a significant risk factor for LXT-induced thrombocytopenia and anemia.
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Affiliation(s)
- Ting Li
- Key Laboratory of Organ Regeneration and Transplantation of the Ministry of Education, The First Hospital of Jilin University, Changchun, China.,Department of Hepatobiliary and Pancreatic Surgery, The First Hospital of Jilin University, Changchun, China.,National-Local Joint Engineering Laboratory of Animal Models for Human Diseases, Changchun, China
| | - Yanan Lv
- Key Laboratory of Organ Regeneration and Transplantation of the Ministry of Education, The First Hospital of Jilin University, Changchun, China.,National-Local Joint Engineering Laboratory of Animal Models for Human Diseases, Changchun, China
| | - Renren Sun
- Key Laboratory of Organ Regeneration and Transplantation of the Ministry of Education, The First Hospital of Jilin University, Changchun, China.,National-Local Joint Engineering Laboratory of Animal Models for Human Diseases, Changchun, China
| | - Yong-Guang Yang
- Key Laboratory of Organ Regeneration and Transplantation of the Ministry of Education, The First Hospital of Jilin University, Changchun, China.,National-Local Joint Engineering Laboratory of Animal Models for Human Diseases, Changchun, China.,International Center of Future Science, Jilin University, Changchun, China
| | - Zheng Hu
- Key Laboratory of Organ Regeneration and Transplantation of the Ministry of Education, The First Hospital of Jilin University, Changchun, China.,National-Local Joint Engineering Laboratory of Animal Models for Human Diseases, Changchun, China
| | - Guoyue Lv
- Key Laboratory of Organ Regeneration and Transplantation of the Ministry of Education, The First Hospital of Jilin University, Changchun, China.,Department of Hepatobiliary and Pancreatic Surgery, The First Hospital of Jilin University, Changchun, China.,National-Local Joint Engineering Laboratory of Animal Models for Human Diseases, Changchun, China
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11
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Yehuda S, Padler-Karavani V. Glycosylated Biotherapeutics: Immunological Effects of N-Glycolylneuraminic Acid. Front Immunol 2020; 11:21. [PMID: 32038661 PMCID: PMC6989436 DOI: 10.3389/fimmu.2020.00021] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2019] [Accepted: 01/07/2020] [Indexed: 12/14/2022] Open
Abstract
The emerging field of biotherapeutics provides successful treatments for various diseases, yet immunogenicity and limited efficacy remain major concerns for many products. Glycosylation is a key factor determining the pharmacological properties of biotherapeutics, including their stability, solubility, bioavailability, pharmacokinetics, and immunogenicity. Hence, an increased attention is directed at optimizing the glycosylation properties of biotherapeutics. Currently, most biotherapeutics are produced in non-human mammalian cells in light of their ability to produce human-like glycosylation. However, most mammals produce the sialic acid N-glycolylneuraminic acid (Neu5Gc), while humans cannot due to a specific genetic defect. Humans consume Neu5Gc in their diet from mammalian derived foods (red meat and dairy) and produce polyclonal antibodies against diverse Neu5Gc-glycans. Moreover, Neu5Gc can metabolically incorporate into human cells and become presented on surface or secreted glycans, glycoproteins, and glycolipids. Several studies in mice suggested that the combination of Neu5Gc-containing epitopes and anti-Neu5Gc antibodies could contribute to exacerbation of chronic inflammation-mediated diseases (e.g., cancer, cardiovascular diseases, and autoimmunity). This could potentially become complicated with exposure to Neu5Gc-containing biotherapeutics, bio-devices or xenografts. Indeed, Neu5Gc can be found on various approved and marketed biotherapeutics. Here, we provide a perspective review on the possible consequences of Neu5Gc glycosylation of therapeutic protein drugs due to the limited published evidence of Neu5Gc glycosylation on marketed biotherapeutics and studies on their putative effects on immunogenicity, drug efficacy, and safety.
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Affiliation(s)
- Sharon Yehuda
- Department of Cell Research and Immunology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Vered Padler-Karavani
- Department of Cell Research and Immunology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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Li Q, Shaikh S, Iwase H, Long C, Lee W, Zhang Z, Wang Y, Ayares D, Cooper DKC, Hara H. Carbohydrate antigen expression and anti-pig antibodies in New World capuchin monkeys: Relevance to studies of xenotransplantation. Xenotransplantation 2019; 26:e12498. [PMID: 30770572 DOI: 10.1111/xen.12498] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2018] [Revised: 11/23/2018] [Accepted: 12/06/2018] [Indexed: 02/06/2023]
Abstract
BACKGROUND Old World non-human primates (OWNHPs) are used for preclinical pig-to-NHP studies. However, like pigs, OWNHPs express Neu5Gc, and therefore do not develop natural anti-Neu5Gc antibodies. New World NHPs (NWNHPs) have been reported not to express Neu5Gc. We investigated the potential of NWNHPs in xenotransplantation research. METHODS We investigated expression of Gal, Neu5Gc, and Sda antigens on RBCs and PBMCs from humans, selected OWNHPs, and capuchin monkeys (a NWNHP). Serum anti-Gal and anti-Neu5Gc IgM and IgG levels were measured by ELISA. Binding of primate serum IgM and IgG to pig RBCs was measured by flow cytometry. RESULTS (a) Neither humans, OWNHPs, or capuchin monkeys expressed Gal on their RBCs, but capuchins expressed Gal on PBMCs. Humans and capuchins did not express Neu5Gc on either RBCs or PBMCs, but OWNHPs expressed Neu5Gc on both cells. Sda was not expressed on any RBCs or PBMCs. (b) By ELISA, human and OWNHP, but not capuchin, sera showed IgM and IgG binding to Gal. Human and capuchin, but not OWNHP, sera demonstrated some binding to Neu5Gc. (c) Anti-Sda IgM/IgG antibodies were detected in OWNHP sera. Knockout of Sda on pig RBCs did not significantly reduce human and capuchin antibody binding. CONCLUSION Capuchin monkeys could be surrogates for humans in experiments using RBCs, islets, neuronal cells, etc, from triple-knockout pigs (but may be too small to be used as recipients of pig organ grafts).
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Affiliation(s)
- Qi Li
- Department of Surgery, Xenotransplantation Program, University of Alabama at Birmingham, Birmingham, Alabama.,Second Affiliated Hospital, University of South China, Hengyang City, China
| | - Sahar Shaikh
- Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Hayato Iwase
- Department of Surgery, Xenotransplantation Program, University of Alabama at Birmingham, Birmingham, Alabama.,Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Cassandra Long
- Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Whayoung Lee
- Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Zhongqiang Zhang
- Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, Pennsylvania.,Department of Organ Transplantation and General Surgery, Second Xiangya Hospital of Central South University, Changsha, China
| | - Yi Wang
- Second Affiliated Hospital, University of South China, Hengyang City, China.,Transplantation Institute of Hainan Medical University, Haikou, China
| | | | - David K C Cooper
- Department of Surgery, Xenotransplantation Program, University of Alabama at Birmingham, Birmingham, Alabama.,Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Hidetaka Hara
- Department of Surgery, Xenotransplantation Program, University of Alabama at Birmingham, Birmingham, Alabama.,Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, Pennsylvania
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Zhang X, Li X, Yang Z, Tao K, Wang Q, Dai B, Qu S, Peng W, Zhang H, Cooper DKC, Dou K. A review of pig liver xenotransplantation: Current problems and recent progress. Xenotransplantation 2019; 26:e12497. [PMID: 30767272 DOI: 10.1111/xen.12497] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 01/01/2019] [Accepted: 01/07/2019] [Indexed: 12/14/2022]
Abstract
Pig liver xenotransplantation appears to be more perplexing when compared to heart or kidney xenotransplantation, even though great progress has been achieved. The relevant molecular mechanisms involved in xenogeneic rejection, including coagulopathy, and particularly thrombocytopenia, are complex, and need to be systematically investigated. The deletion of expression of Gal antigens in the liver graft highlights the injurious impact of nonGal antigens, which continue to induce humoral rejection. Innate immunity, particularly mediated by macrophages and natural killer cells, interplays with inflammation and coagulation disorders. Kupffer cells and liver sinusoidal endothelial cells (LSECs) together mediate leukocyte, erythrocyte, and platelet sequestration and phagocytosis, which can be exacerbated by increased cytokine production, cell desialylation, and interspecies incompatibilities. The coagulation cascade is activated by release of tissue factor which can be dependent or independent of the xenoreactive immune response. Depletion of endothelial anticoagulants and anti-platelet capacity amplify coagulation activation, and interspecies incompatibilities of coagulation-regulatory proteins facilitate dysregulation. LSECs involved in platelet phagocytosis and transcytosis, coupled with hepatocyte-mediated degradation, are responsible for thrombocytopenia. Adaptive immunity could also be problematic in long-term liver graft survival. Currently, relevant evidence and study results of various genetic modifications to the pig donor need to be fully determined, with the aim of identifying the ideal transgene combination for pig liver xenotransplantation. We believe that clinical trials of pig liver xenotransplantation should initially be considered as a bridge to allotransplantation.
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Affiliation(s)
- Xuan Zhang
- Department of Hepatobiliary Surgery, Xijing Hospital, The Fourth Military Medical University, Xi'an, China
| | - Xiao Li
- Department of Hepatobiliary Surgery, Xijing Hospital, The Fourth Military Medical University, Xi'an, China
| | - Zhaoxu Yang
- Department of Hepatobiliary Surgery, Xijing Hospital, The Fourth Military Medical University, Xi'an, China
| | - Kaishan Tao
- Department of Hepatobiliary Surgery, Xijing Hospital, The Fourth Military Medical University, Xi'an, China
| | - Quancheng Wang
- Department of Hepatobiliary Surgery, Xijing Hospital, The Fourth Military Medical University, Xi'an, China
| | - Bin Dai
- Department of Hepatobiliary Surgery, Xijing Hospital, The Fourth Military Medical University, Xi'an, China
| | - Shibin Qu
- Department of Hepatobiliary Surgery, Xijing Hospital, The Fourth Military Medical University, Xi'an, China
| | - Wei Peng
- Department of Hepatobiliary Surgery, Xijing Hospital, The Fourth Military Medical University, Xi'an, China
| | - Hong Zhang
- Department of Hepatobiliary Surgery, Xijing Hospital, The Fourth Military Medical University, Xi'an, China
| | - David K C Cooper
- Xenotransplantation Program, Department of Surgery, University of Alabama at Birmingham, Birmingham, Alabama
| | - Kefeng Dou
- Department of Hepatobiliary Surgery, Xijing Hospital, The Fourth Military Medical University, Xi'an, China
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14
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Zhang Q, Wang Y, Zheng Q, Li J. Analysis of O-Acetylated Sialic Acids in Dried Blood Spots. Anal Chem 2019; 91:2744-2751. [DOI: 10.1021/acs.analchem.8b04420] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Qiwei Zhang
- Key Laboratory of Optoelectronic Chemical Materials and Devices of Ministry of Education, Institute for Interdisciplinary Research,
Institute of Environment and Health, Jianghan University, Wuhan 430056, China
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Haidian District, Beijing 100085, China
| | - Yawei Wang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Haidian District, Beijing 100085, China
| | - Qi Zheng
- Key Laboratory of Optoelectronic Chemical Materials and Devices of Ministry of Education, Institute for Interdisciplinary Research,
Institute of Environment and Health, Jianghan University, Wuhan 430056, China
| | - Jianjun Li
- National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario, Canada K1A 0R6
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Eshmuminov D, Leoni F, Schneider MA, Becker D, Muller X, Onder C, Hefti M, Schuler MJ, Dutkowski P, Graf R, Rudolf von Rohr P, Clavien PA, Bautista Borrego L. Perfusion settings and additives in liver normothermic machine perfusion with red blood cells as oxygen carrier. A systematic review of human and porcine perfusion protocols. Transpl Int 2018; 31:956-969. [PMID: 29928775 DOI: 10.1111/tri.13306] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 06/10/2018] [Accepted: 06/18/2018] [Indexed: 12/30/2022]
Abstract
Liver machine perfusion (MP) at normothermic temperature (NMP) is a promising way to preserve and evaluate extended criteria donor livers. Currently, no consensus exists in methodology and perfusion protocols. Here, the authors performed a systematic literature search to identify human and porcine studies reporting on liver NMP with red blood cells. A qualitative synthesis was performed concerning technical aspects of MP, fluid composition, gas supply, and liver positioning. Thirty-seven publications including 11 human and 26 porcine studies were considered for qualitative synthesis. Control mode, pressure, flow, perfusate additives, and targeted blood gas parameters varied across human as well as porcine studies. For future analyses, it is advisable to report flow adjusted to liver weight and exact pressure parameters including mean, systolic, and diastolic pressure. Parenteral nutrition and insulin addition was common. Parenteral nutrition included amino acids and/or glucose without lipids. Taurocholic acid derivatives were used as bile flow promoters. However, short-term human NMP without taurocholic acid derivatives seems to be possible. This finding is relevant due to the lack of clinical grade bile salts. Near physiological oxygen tension in the perfusate is doable by adjusting gas flows, while blood gas parameters regulation needs more detailed description.
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Affiliation(s)
- Dilmurodjon Eshmuminov
- Department of Surgery, Swiss HPB and Transplantation Center, University Hospital Zurich, Zurich, Switzerland
| | - Filippo Leoni
- Department of Surgery, Swiss HPB and Transplantation Center, University Hospital Zurich, Zurich, Switzerland
| | - Marcel André Schneider
- Department of Surgery, Swiss HPB and Transplantation Center, University Hospital Zurich, Zurich, Switzerland
| | - Dustin Becker
- Wyss Zurich - ETH Zurich/University of Zurich, Zurich, Switzerland
| | - Xavier Muller
- Department of Surgery, Swiss HPB and Transplantation Center, University Hospital Zurich, Zurich, Switzerland
| | - Christopher Onder
- Institute for Dynamic Systems and Control, ETH Zurich, Zurich, Switzerland
| | - Max Hefti
- Wyss Zurich - ETH Zurich/University of Zurich, Zurich, Switzerland
| | - Martin J Schuler
- Wyss Zurich - ETH Zurich/University of Zurich, Zurich, Switzerland
| | - Philipp Dutkowski
- Department of Surgery, Swiss HPB and Transplantation Center, University Hospital Zurich, Zurich, Switzerland
| | - Rolf Graf
- Department of Surgery, Swiss HPB and Transplantation Center, University Hospital Zurich, Zurich, Switzerland
| | | | - Pierre-Alain Clavien
- Department of Surgery, Swiss HPB and Transplantation Center, University Hospital Zurich, Zurich, Switzerland
| | - Lucia Bautista Borrego
- Department of Surgery, Swiss HPB and Transplantation Center, University Hospital Zurich, Zurich, Switzerland
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Taylor TR, Burlak C. Xenotransplantation literature update, November/December 2017. Xenotransplantation 2018; 25. [PMID: 29427359 DOI: 10.1111/xen.12389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 01/17/2018] [Indexed: 11/28/2022]
Affiliation(s)
- Travis R Taylor
- Department of Medical Microbiology and Immunology, University of Toledo Medical Center, Toledo, OH, USA
| | - Christopher Burlak
- Schultz Diabetes Institute, Department of Surgery, University of Minnesota, Minneapolis, MN, USA
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Cimeno A, French BM, Powell JM, Phelps C, Ayares D, O'Neill NA, Laird CT, Pierson RN, Azimzadeh AM, Barth RN, LaMattina JC. Synthetic liver function is detectable in transgenic porcine livers perfused with human blood. Xenotransplantation 2017; 25. [PMID: 29067741 DOI: 10.1111/xen.12361] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 09/21/2017] [Accepted: 09/26/2017] [Indexed: 12/27/2022]
Abstract
In addition to immune barriers, molecular incompatibilities between species are predicted to limit pig liver survival in primate xenotransplantation models. Assessment and measurement of synthetic function of genetically modified porcine livers after ex vivo perfusion with human blood have not previously been described. Eight porcine livers from α1,3-galactosyl transferase knockout and human membrane cofactor (GalTKO.hCD46), six livers from GalTKO.hCD46 and N-glycolylneuraminic acid knockout (GalTKO.hCD46.Neu5GcKO), and six livers from GalTKO.hCD46 with humanized decay-accelerating factor (hCD55), endothelial protein C receptor (hEPCR), tissue factor pathway inhibitor (hTFPI), and integrin-associated protein (hCD47) (GalTKO.hCD46.hCD55.hEPCR.hTFPI.hCD47) pigs were perfused with human blood under physiologic conditions. Timed blood samples were tested for liver enzymes and for pig-specific albumin production via Western blot. Porcine albumin levels increased with time in all experiments. By densitometry, GalTKO.hCD46.Neu5GcKO livers had the highest albumin levels, measured both as total produced, and when controlled for perfusion duration, compared to GalTKO.hCD46 (P = .068) and GalTKO.hCD46.hCD55.hEPCR.hTFPI.hCD47 livers (P = .04). Porcine livers perfused with human blood demonstrated the synthetic ability to produce albumin in all cases. GalTKO.hCD46.Neu5GcKO pig livers demonstrated the most robust albumin production. This suggests that the Neu5GcKO phenotype provides a protective effect on the graft due to decreased human antibody recognition and graft injury.
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Affiliation(s)
- Arielle Cimeno
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Beth M French
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Jessica M Powell
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA
| | | | | | - Natalie A O'Neill
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Christopher T Laird
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Richard N Pierson
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Agnes M Azimzadeh
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Rolf N Barth
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA
| | - John C LaMattina
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA
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