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Einstein SA, Steyn LV, Weegman BP, Suszynski TM, Sambanis A, O'Brien TD, Avgoustiniatos ES, Firpo MT, Graham ML, Janecek J, Eberly LE, Garwood M, Putnam CW, Papas KK. Hypoxia within subcutaneously implanted macroencapsulation devices limits the viability and functionality of densely loaded islets. FRONTIERS IN TRANSPLANTATION 2023; 2:1257029. [PMID: 38993891 PMCID: PMC11235299 DOI: 10.3389/frtra.2023.1257029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 10/20/2023] [Indexed: 07/13/2024]
Abstract
Introduction Subcutaneous macroencapsulation devices circumvent disadvantages of intraportal islet therapy. However, a curative dose of islets within reasonably sized devices requires dense cell packing. We measured internal PO2 of implanted devices, mathematically modeled oxygen availability within devices and tested the predictions with implanted devices containing densely packed human islets. Methods Partial pressure of oxygen (PO2) within implanted empty devices was measured by noninvasive 19F-MRS. A mathematical model was constructed, predicting internal PO2, viability and functionality of densely packed islets as a function of external PO2. Finally, viability was measured by oxygen consumption rate (OCR) in day 7 explants loaded at various islet densities. Results In empty devices, PO2 was 12 mmHg or lower, despite successful external vascularization. Devices loaded with human islets implanted for 7 days, then explanted and assessed by OCR confirmed trends proffered by the model but viability was substantially lower than predicted. Co-localization of insulin and caspase-3 immunostaining suggested that apoptosis contributed to loss of beta cells. Discussion Measured PO2 within empty devices declined during the first few days post-transplant then modestly increased with neovascularization around the device. Viability of islets is inversely related to islet density within devices.
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Affiliation(s)
- Samuel A Einstein
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States
- Department of Radiology, The Pennsylvania State University, Hershey, PA, United States
| | - Leah V Steyn
- Department of Surgery, University of Arizona, Tucson, AZ, United States
| | - Bradley P Weegman
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States
- Sylvatica Biotech Inc., North Charleston, SC, United States
| | - Thomas M Suszynski
- Department of Plastic Surgery, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Athanassios Sambanis
- Department of Chemical & Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, United States
| | - Timothy D O'Brien
- Veterinary Population Medicine Department, University of Minnesota, Saint Paul, MN, United States
- Department of Medicine, Stem Cell Institute, University of Minnesota, Minneapolis, MN, United States
| | | | - Meri T Firpo
- Department of Medicine, Stem Cell Institute, University of Minnesota, Minneapolis, MN, United States
| | - Melanie L Graham
- Veterinary Population Medicine Department, University of Minnesota, Saint Paul, MN, United States
- Department of Surgery, Preclinical Research Center, University of Minnesota, Saint Paul, MN, United States
| | - Jody Janecek
- Department of Surgery, Preclinical Research Center, University of Minnesota, Saint Paul, MN, United States
| | - Lynn E Eberly
- Division of Biostatistics, University of Minnesota, Minneapolis, MN, United States
| | - Michael Garwood
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States
| | - Charles W Putnam
- Department of Surgery, University of Arizona, Tucson, AZ, United States
| | - Klearchos K Papas
- Department of Surgery, University of Arizona, Tucson, AZ, United States
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Song M, Fitch ZW, Samy KP, Martin BM, Gao Q, Patrick Davis R, Leopardi FV, Huffman N, Schmitz R, Devi GR, Collins BH, Kirk AD. Coagulation, inflammation, and CD46 transgene expression in neonatal porcine islet xenotransplantation. Xenotransplantation 2021; 28:e12680. [PMID: 33619844 DOI: 10.1111/xen.12680] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 12/17/2020] [Accepted: 02/12/2021] [Indexed: 12/20/2022]
Abstract
BACKGROUND Thrombosis is a known consequence of intraportal islet transplantation, particularly for xenogeneic islets. To define the origins of thrombosis after islet xenotransplantation and relate it to early inflammation, we examined porcine islets transplanted into non-human primates using a dual-transplant model to directly compare islet characteristics. METHODS α1,3-Galactosyltransferase gene-knockout (GTKO) islets with and without expression of the human complement regulatory transgene CD46 (hCD46) were studied. Biologically inert polyethylene microspheres were used to examine the generic pro-thrombotic effects of particle embolization. Immunohistochemistry was performed 1 and 24 hours after transplantation. RESULTS Xeno-islet transplantation activated both extrinsic and intrinsic coagulation pathways. The intrinsic pathway was also initiated by microsphere embolization, while extrinsic pathway tissue factor (TF) and platelet aggregation were more specific to engrafted islets. hCD46 expression significantly reduced TF, platelet, fibrin, and factor XIIIa accumulation in and around islets but did not alter intrinsic factor activation. Layers of TF+ cells emerged around islets within 24 hours, particularly co-localized with vimentin, and identified as CD3+ and CD68+ cells inflammatory cells. CONCLUSIONS These findings detail the origins of thrombosis following islet xenotransplantation, relate it to early immune activation, and suggest a role for transgenic hCD46 expression in its mitigation. Layers of TF-positive inflammatory cells and fibroblasts around islets at 24 hours may have important roles in the progressive events of thrombosis, inflammatory cell recruitment, rejection, and the ultimate outcome of transplanted grafts. These suggest that the strategies targeting these elements could yield more progress toward successful xenogeneic islet engraftment and survival.
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Affiliation(s)
- Mingqing Song
- Department of Surgery, Duke University School of Medicine, Durham, NC, USA
| | - Zachary W Fitch
- Department of Surgery, Duke University School of Medicine, Durham, NC, USA
| | - Kannan P Samy
- Department of Surgery, Duke University School of Medicine, Durham, NC, USA
| | - Benjamin M Martin
- Department of Surgery, Emory University School of Medicine, Atlanta, GA, USA
| | - Qimeng Gao
- Department of Surgery, Duke University School of Medicine, Durham, NC, USA
| | | | - Francis V Leopardi
- Department of Surgery, Duke University School of Medicine, Durham, NC, USA
| | - Niki Huffman
- Department of Surgery, Duke University School of Medicine, Durham, NC, USA
| | - Robin Schmitz
- Department of Surgery, Duke University School of Medicine, Durham, NC, USA
| | - Gayathri R Devi
- Department of Surgery, Duke University School of Medicine, Durham, NC, USA
| | - Bradley H Collins
- Department of Surgery, Duke University School of Medicine, Durham, NC, USA
| | - Allan D Kirk
- Department of Surgery, Duke University School of Medicine, Durham, NC, USA
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