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Qi B, Ding Y, Zhang Y, Kou L, Zhao YZ, Yao Q. Biomaterial-assisted strategies to improve islet graft revascularization and transplant outcomes. Biomater Sci 2024; 12:821-836. [PMID: 38168805 DOI: 10.1039/d3bm01295f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Islet transplantation holds significant promise as a curative approach for type 1 diabetes (T1D). However, the transition of islet transplantation from the experimental phase to widespread clinical implementation has not occurred yet. One major hurdle in this field is the challenge of insufficient vascularization and subsequent early loss of transplanted islets, especially in non-intraportal transplantation sites. The establishment of a fully functional vascular system following transplantation is crucial for the survival and secretion function of islet grafts. This vascular network not only ensures the delivery of oxygen and nutrients, but also plays a critical role in insulin release and the timely removal of metabolic waste from the grafts. This review summarizes recent advances in effective strategies to improve graft revascularization and enhance islet survival. These advancements include the local release and regulation of angiogenic factors (e.g., vascular endothelial growth factor, VEGF), co-transplantation of vascular fragments, and pre-vascularization of the graft site. These innovative approaches pave the way for the development of effective islet transplantation therapies for individuals with T1D.
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Affiliation(s)
- Boyang Qi
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, China.
| | - Yang Ding
- The Second School of Medicine, Wenzhou Medical University, Wenzhou, China
| | - Ying Zhang
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, China.
| | - Longfa Kou
- The Second Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province, China
| | - Ying-Zheng Zhao
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, China.
| | - Qing Yao
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, China.
- Cixi Biomedical Research Institute, Wenzhou Medical University, Zhejiang, China
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2
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Cheng P, Jian Q, Fu Z, Deng R, Ma Y. Inhibition of DAI refrains dendritic cells from maturation and prolongs murine islet and skin allograft survival. Front Immunol 2023; 14:1182851. [PMID: 37197662 PMCID: PMC10183602 DOI: 10.3389/fimmu.2023.1182851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Accepted: 04/17/2023] [Indexed: 05/19/2023] Open
Abstract
Introduction Central to allograft rejection is the T cell-mediated adaptive immune response initiated by activated dendritic cells (DCs). Previous studies have shown that the DNA-dependent activator of IFN regulatory factors (DAI) is involved in the maturation and activation of DCs. Therefore, we hypothesized that inhibition of DAI could prevent DCs from maturation and prolong murine allograft survival. Methods Donor mouse bone marrow-derived dendritic cells (BMDCs) were transduced with the recombinant adenovirus vector (AdV-DAI-RNAi-GFP) to inhibit DAI expression (DC-DAI-RNAi), and the immune cell phenotype and function of DC-DAI-RNAi upon lipopolysaccharide (LPS) stimulation were evaluated. Then DC-DAI-RNAi was injected into recipient mice before islet transplantation and skin transplantation. The survival times of islet and skin allograft were recorded and the proportions of T cell subsets in spleen and secretion levels of cytokines in serum were measured. Results We identified that DC-DAI-RNAi inhibited the expression of main co-stimulatory molecules and MHC-II, exhibited strong phagocytic ability, and secreted high levels of immunosuppressive cytokines and low levels of immunostimulating cytokines. Recipient mice treated with DC-DAI-RNAi had longer islet and skin allograft survival times. In the murine islet transplantation model, we observed an increase in Treg cells proportion, a reduction in Th1 and Th17 cells proportions in spleen, and similar trends in their secreted cytokines in serum in the DC-DAI-RNAi group. Conclusion Inhibition of DAI by adenovirus transduction inhibits the maturation and activation of DCs, affects the differentiation of T cell subsets as well as their secreted cytokines, and prolongs allograft survival.
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Affiliation(s)
- Pengrui Cheng
- Organ Transplant Center, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Organ Donation and Transplant Immunology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial International Cooperation Base of Science and Technology (Organ Transplantation), The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Qian Jian
- Organ Transplant Center, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Organ Donation and Transplant Immunology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial International Cooperation Base of Science and Technology (Organ Transplantation), The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Zongli Fu
- Organ Transplant Center, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Organ Donation and Transplant Immunology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial International Cooperation Base of Science and Technology (Organ Transplantation), The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Ronghai Deng
- Organ Transplant Center, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Organ Donation and Transplant Immunology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial International Cooperation Base of Science and Technology (Organ Transplantation), The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- *Correspondence: Ronghai Deng, ; Yi Ma,
| | - Yi Ma
- Organ Transplant Center, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial Key Laboratory of Organ Donation and Transplant Immunology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- Guangdong Provincial International Cooperation Base of Science and Technology (Organ Transplantation), The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- *Correspondence: Ronghai Deng, ; Yi Ma,
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Challenges with Cell-based Therapies for Type 1 Diabetes Mellitus. Stem Cell Rev Rep 2022; 19:601-624. [PMID: 36434300 DOI: 10.1007/s12015-022-10482-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/13/2022] [Indexed: 11/27/2022]
Abstract
Type 1 diabetes (T1D) is a chronic, lifelong metabolic disease. It is characterised by the autoimmune-mediated loss of insulin-producing pancreatic β cells in the islets of Langerhans (β-islets), resulting in disrupted glucose homeostasis. Administration of exogenous insulin is the most common management method for T1D, but this requires lifelong reliance on insulin injections and invasive blood glucose monitoring. Replacement therapies with beta cells are being developed as an advanced curative treatment for T1D. Unfortunately, this approach is limited by the lack of donated pancreatic tissue, the difficulties in beta cell isolation and viability maintenance, the longevity of the transplanted cells in vivo, and consequently high costs. Emerging approaches to address these limitations are under intensive investigations, including the production of insulin-producing beta cells from various stem cells, and the development of bioengineered devices including nanotechnologies for improving islet transplantation efficacy without the need for recipients taking toxic anti-rejection drugs. These emerging approaches present promising prospects, while the challenges with the new techniques need to be tackled for ultimately clinical treatment of T1D. This review discussed the benefits and limitations of the cell-based therapies for beta cell replacement as potential curative treatment for T1D, and the applications of bioengineered devices including nanotechnology to overcome the challenges associated with beta cell transplantation.
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S. A. F, K. S. C, L. D, M. G, S. P, R. L. L, C. A. H. Engineering Vascularized Islet Macroencapsulation Devices: An in vitro Platform to Study Oxygen Transport in Perfused Immobilized Pancreatic Beta Cell Cultures. Front Bioeng Biotechnol 2022; 10:884071. [PMID: 35519615 PMCID: PMC9061948 DOI: 10.3389/fbioe.2022.884071] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 04/01/2022] [Indexed: 02/01/2023] Open
Abstract
Islet encapsulation devices serve to deliver pancreatic beta cells to type 1 diabetic patients without the need for chronic immunosuppression. However, clinical translation is hampered by mass transport limitations causing graft hypoxia. This is exacerbated in devices relying only on passive diffusion for oxygenation. Here, we describe the application of a cylindrical in vitro perfusion system to study oxygen effects on islet-like clusters immobilized in alginate hydrogel. Mouse insulinoma 6 islet-like clusters were generated using microwell plates and characterized with respect to size distribution, viability, and oxygen consumption rate to determine an appropriate seeding density for perfusion studies. Immobilized clusters were perfused through a central channel at different oxygen tensions. Analysis of histological staining indicated the distribution of viable clusters was severely limited to near the perfusion channel at low oxygen tensions, while the distribution was broadest at normoxia. The results agreed with a 3D computational model designed to simulate the oxygen distribution within the perfusion device. Further simulations were generated to predict device performance with human islets under in vitro and in vivo conditions. The combination of experimental and computational findings suggest that a multichannel perfusion strategy could support in vivo viability and function of a therapeutic islet dose.
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Affiliation(s)
- Fernandez S. A.
- Department of Chemical Engineering, McGill University, Montréal, QC, Canada
| | - Champion K. S.
- Department of Chemical Engineering, McGill University, Montréal, QC, Canada
| | - Danielczak L.
- Department of Chemical Engineering, McGill University, Montréal, QC, Canada
| | - Gasparrini M.
- Human Islet Transplant Laboratory, McGill University Health Centre, Montréal, QC, Canada
| | - Paraskevas S.
- Human Islet Transplant Laboratory, McGill University Health Centre, Montréal, QC, Canada
- Department of Surgery, McGill University Health Centre, Montréal, QC, Canada
| | - Leask R. L.
- Department of Chemical Engineering, McGill University, Montréal, QC, Canada
- Department of Biomedical Engineering, McGill University, Montréal, QC, Canada
| | - Hoesli C. A.
- Department of Chemical Engineering, McGill University, Montréal, QC, Canada
- Department of Biomedical Engineering, McGill University, Montréal, QC, Canada
- *Correspondence: Hoesli C. A.,
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Three-dimensional Vascularized β-cell Spheroid Tissue Derived From Human Induced Pluripotent Stem Cells for Subcutaneous Islet Transplantation in a Mouse Model of Type 1 Diabetes. Transplantation 2022; 106:48-59. [PMID: 34905762 DOI: 10.1097/tp.0000000000003745] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
BACKGROUND Islet transplantation is an effective replacement therapy for type 1 diabetes (T1D) patients. However, shortage of donor organ for allograft is obstacle for further development of the treatment. Subcutaneous transplantation with stem cell-derived β-cells might overcome this, but poor vascularity in the site is burden for success in the transplantation. We investigated the effect of subcutaneous transplantation of vascularized β-cell spheroid tissue constructed 3-dimensionally using a layer-by-layer (LbL) cell-coating technique in a T1D model mouse. METHODS We used MIN6 cells to determine optimal conditions for the coculture of β-cell spheroids, normal human dermal fibroblasts, and human umbilical vein endothelial cells, and then, under those conditions, we constructed vascularized spheroid tissue using human induced pluripotent stem cell-derived β-cells (hiPS β cells). The function of insulin secretion of the vascularized hiPS β-cell spheroid tissue was evaluated in vitro. Furthermore, the function was investigated in T1D model NOD/SCID mice subcutaneously transplanted with the tissue. RESULTS In vitro, the vascularized hiPS β-cell spheroid tissue exhibited enhanced insulin secretion. The vascularized hiPS β-cell spheroid tissue also significantly decreased blood glucose levels in diabetic immunodeficient mice when transplanted subcutaneously. Furthermore, host mouse vessels were observed in the explanted vascularized hiPS β-cell spheroid tissue. CONCLUSIONS Vascularized hiPS β-cell spheroid tissue decreased blood glucose levels in the diabetic mice. This therapeutic effect was suggested due to host angiogenesis in the graft. This method could lead to a promising regenerative treatment for T1D patients.
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Lee SM, Kim D, Kwak KM, Khin PP, Lim OK, Kim KW, Kim BJ, Jun HS. Comparison of the Effects of Liraglutide on Islet Graft Survival Between Local and Systemic Delivery. Cell Transplant 2021; 29:963689720971245. [PMID: 33172296 PMCID: PMC7784585 DOI: 10.1177/0963689720971245] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Islet transplantation has emerged as a promising treatment for type 1 diabetes mellitus. Liraglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist, protects beta cells after islet transplantation by improving glycemic control through several mechanisms. In this study, we compared the effects of local pretreatment and systemic treatment with liraglutide on islet transplantation in a diabetic mouse model. Streptozotocin (STZ)-induced diabetic C57BL/6 mice were transplanted with syngeneic islets under the kidney capsule. Isolated islets were either locally treated with liraglutide before transplantation or mice were treated systemically by intraperitoneal injection after islet transplantation. Local pretreatment of islets with liraglutide was more effective in increasing body weight, decreasing hemoglobin A1c levels, and lowering blood glucose levels in STZ-diabetic mice transplanted with islets. Local pretreatment was also more effective in increasing insulin secretion and islet survival in STZ-diabetic mice. Histological analysis of the transplantation site revealed fewer apoptotic cells following local pretreatment compared with systemic injection of liraglutide. These findings indicate that liraglutide administered once locally before transplantation might have superior effects on islet preservation than systemic administration.
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Affiliation(s)
- Song Mi Lee
- College of Pharmacy and Gachon Institute Pharmaceutical Science, Gachon University, Yeonsu-gu, Incheon, Korea.,Lee Gil Ya Cancer and Diabetes Institute, Gachon University, Yeonsu-gu, Incheon, Korea.,Both the authors contributed equally to this article
| | - Donghee Kim
- Lee Gil Ya Cancer and Diabetes Institute, Gachon University, Yeonsu-gu, Incheon, Korea.,Both the authors contributed equally to this article
| | - Kyung Min Kwak
- Lee Gil Ya Cancer and Diabetes Institute, Gachon University, Yeonsu-gu, Incheon, Korea
| | - Phyu Phyu Khin
- College of Pharmacy and Gachon Institute Pharmaceutical Science, Gachon University, Yeonsu-gu, Incheon, Korea.,Lee Gil Ya Cancer and Diabetes Institute, Gachon University, Yeonsu-gu, Incheon, Korea
| | - Oh Kyung Lim
- Department of Rehabilitation Medicine, Gachon University Gil Medical Center, Namdong-gu, Incheon, Korea
| | - Kwang-Won Kim
- Department of Internal Medicine, Gachon University Gil Medical Center, Namdong-gu, Incheon, Korea
| | - Byung-Joon Kim
- Department of Internal Medicine, Gachon University Gil Medical Center, Namdong-gu, Incheon, Korea
| | - Hee-Sook Jun
- College of Pharmacy and Gachon Institute Pharmaceutical Science, Gachon University, Yeonsu-gu, Incheon, Korea.,Lee Gil Ya Cancer and Diabetes Institute, Gachon University, Yeonsu-gu, Incheon, Korea.,Gil Medical Research Institute, Gil Hospital, Namdong-gu, Incheon, Korea
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7
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Tissue Engineering Strategies for Improving Beta Cell Transplantation Outcome. CURRENT TRANSPLANTATION REPORTS 2021. [DOI: 10.1007/s40472-021-00333-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Abstract
Purpose of Review
Beta cell replacement therapy as a form of islet transplantation is a promising alternative therapy with the possibility to make selected patients with type 1 diabetes (T1D) insulin independent. However, this technique faces challenges such as extensive activation of the host immune system post-transplantation, lifelong need for immunosuppression, and the scarcity of islet donor pancreas. Advancement in tissue engineering strategies can improve these challenges and allow for a more widespread application of this therapy. This review will discuss the recent development and clinical translation of tissue engineering strategies in beta cell replacement therapy.
Recent Findings
Tissue engineering offers innovative solutions for producing unlimited glucose responsive cells and fabrication of appropriate devices/scaffolds for transplantation applications. Generation of pancreatic organoids with supporting cells in biocompatible biomaterials is a powerful technique to improve the function of insulin-producing cell clusters. Fabrication of physical barriers such as encapsulation strategies can protect the cells from the host immune system and allow for graft retrieval, although this strategy still faces major challenges to fully restore physiological glucose regulation.
Summary
The three main components of tissue engineering strategies including the generation of stem cell-derived insulin-producing cells and organoids and the possibilities for therapeutic delivery of cell-seeded devices to extra-hepatic sites need to come together in order to provide safe and functional insulin-producing devices for clinical beta cell replacement therapy.
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8
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Ren A, Li Z, Zhang X, Deng R, Ma Y. Inhibition of Dectin-1 on Dendritic Cells Prevents Maturation and Prolongs Murine Islet Allograft Survival. J Inflamm Res 2021; 14:63-73. [PMID: 33469336 PMCID: PMC7812029 DOI: 10.2147/jir.s287453] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Accepted: 12/24/2020] [Indexed: 01/15/2023] Open
Abstract
Introduction The ability of dendritic cells (DCs) to initiate an immune response or induce immune tolerance depends on their maturation status. Dendritic-cell-associated C-type lectin 1 (Dectin-1) plays a key role in the differentiation, activation, and maturation of DCs. Therefore, we hypothesized that inhibition of Dectin-1 could prevent DC maturation and induce immune tolerance of transplanted organs. Methods DCs were transduced with a recombinant lentiviral vector to inhibit Dectin-1 and then were injected into a murine recipient before islet transplantation. C57BL/6 mice (H-2b) were treated with lentiviral vector-Dectin-1-RNAi-DC (DC-Dectin-1-RNAi group), lentiviral vector-GFP DCs (DC-GFP group), and PBS (control group). Pancreatic islet transplantation was performed and graft survival was recorded. The proportions of regulatory T cells, Th1 cells, and Th17 cells in the spleen and draining lymph nodes, and serum levels of interleukin (IL)-10, IL-17, and interferon (INF)-γ were measured. Results The inhibition of Dectin-1 resulted in low expression of MHC-II and costimulatory molecules in DCs. Murine recipients treated with DC-Dectin-1-RNAi had longer islet allograft survival time, a reduction in the levels of Th1 and Th17 cells and secreted cytokines, and an increase of Treg cells. Conclusion The inhibition of Dectin-1 by recombinant lentiviral vector Dectin-1-RNAi inhibits the maturation and activation of DCs, affects the differentiation of T cell subsets, and prolongs allograft survival.
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Affiliation(s)
- Ao Ren
- Organ Transplant Center, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China.,Guangdong Provincial Key Laboratory of Organ Donation and Transplant Immunology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China.,Guangdong Provincial International Cooperation Base of Science and Technology (Organ Transplantation), The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China
| | - Zhongqiu Li
- Organ Transplant Center, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China.,Guangdong Provincial Key Laboratory of Organ Donation and Transplant Immunology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China.,Guangdong Provincial International Cooperation Base of Science and Technology (Organ Transplantation), The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China
| | - Xuzhi Zhang
- Organ Transplant Center, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China.,Guangdong Provincial Key Laboratory of Organ Donation and Transplant Immunology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China.,Guangdong Provincial International Cooperation Base of Science and Technology (Organ Transplantation), The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China
| | - Ronghai Deng
- Organ Transplant Center, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China.,Guangdong Provincial Key Laboratory of Organ Donation and Transplant Immunology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China.,Guangdong Provincial International Cooperation Base of Science and Technology (Organ Transplantation), The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China
| | - Yi Ma
- Organ Transplant Center, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China.,Guangdong Provincial Key Laboratory of Organ Donation and Transplant Immunology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China.,Guangdong Provincial International Cooperation Base of Science and Technology (Organ Transplantation), The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, People's Republic of China
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Lee YN, Yi HJ, Goh H, Park JY, Ferber S, Shim IK, Kim SC. Spheroid Fabrication Using Concave Microwells Enhances the Differentiation Efficacy and Function of Insulin-Producing Cells via Cytoskeletal Changes. Cells 2020; 9:cells9122551. [PMID: 33261076 PMCID: PMC7768489 DOI: 10.3390/cells9122551] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 11/11/2020] [Accepted: 11/24/2020] [Indexed: 01/21/2023] Open
Abstract
Pancreatic islet transplantation is the fundamental treatment for insulin-dependent diabetes; however, donor shortage is a major hurdle in its use as a standard treatment. Accordingly, differentiated insulin-producing cells (DIPCs) are being developed as a new islet source. Differentiation efficiency could be enhanced if the spheroid structure of the natural islets could be recapitulated. Here, we fabricated DIPC spheroids using concave microwells, which enabled large-scale production of spheroids of the desired size. We prepared DIPCs from human liver cells by trans-differentiation using transcription factor gene transduction. Islet-related gene expression and insulin secretion levels were higher in spheroids compared to those in single-cell DIPCs, whereas actin–myosin interactions significantly decreased. We verified actin–myosin-dependent insulin expression in single-cell DIPCs by using actin–myosin interaction inhibitors. Upon transplanting cells into the kidney capsule of diabetic mouse, blood glucose levels decreased to 200 mg/dL in spheroid-transplanted mice but not in single cell-transplanted mice. Spheroid-transplanted mice showed high engraftment efficiency in in vivo fluorescence imaging. These results demonstrated that spheroids fabricated using concave microwells enhanced the engraftment and functions of DIPCs via actin–myosin-mediated cytoskeletal changes. Our strategy potentially extends the clinical application of DIPCs for improved differentiation, glycemic control, and transplantation efficiency of islets.
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Affiliation(s)
- Yu Na Lee
- Asan Medical Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.N.L.); (H.J.Y.); (H.G.); (J.Y.P.)
- Asan Medical Center, Department of Medical Science, Asan Medical Institute of Convergence Science and Technology (AMIST), University of Ulsan College of Medicine, Seoul 05505, Korea
| | - Hye Jin Yi
- Asan Medical Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.N.L.); (H.J.Y.); (H.G.); (J.Y.P.)
- Asan Medical Center, Department of Medical Science, Asan Medical Institute of Convergence Science and Technology (AMIST), University of Ulsan College of Medicine, Seoul 05505, Korea
| | - Hanse Goh
- Asan Medical Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.N.L.); (H.J.Y.); (H.G.); (J.Y.P.)
| | - Ji Yoon Park
- Asan Medical Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.N.L.); (H.J.Y.); (H.G.); (J.Y.P.)
- Department of Chemistry, Wesleyan University, Middletown, CT 06457, USA
| | - Sarah Ferber
- Regenerative Medicine, Stem Cell and Tissue Engineering Center, Sheba Medical Center, Tel-Hashomer 52621, Israel;
- Dia-Cure, Acad. Nicolae Cajal Institute of Medical Scientific Research, Titu Maiorescu University, 022328 Bucharest, Romania
- Orgenesis Ltd., Ness-Ziona 7403631, Israel
- Department of Human Genetics, Sackler School of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
| | - In Kyong Shim
- Asan Medical Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.N.L.); (H.J.Y.); (H.G.); (J.Y.P.)
- Asan Medical Center, Department of Medical Science, Asan Medical Institute of Convergence Science and Technology (AMIST), University of Ulsan College of Medicine, Seoul 05505, Korea
- Correspondence: or (I.K.S.); (S.C.K.); Tel.: +82-2-3010-4173 (I.K.S.); +82-2-3010-3936 (S.C.K.)
| | - Song Cheol Kim
- Asan Medical Center, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul 05505, Korea; (Y.N.L.); (H.J.Y.); (H.G.); (J.Y.P.)
- Asan Medical Center, Department of Medical Science, Asan Medical Institute of Convergence Science and Technology (AMIST), University of Ulsan College of Medicine, Seoul 05505, Korea
- Asan Medical Center, Department of Surgery, University of Ulsan College of Medicine, Seoul 05505, Korea
- Correspondence: or (I.K.S.); (S.C.K.); Tel.: +82-2-3010-4173 (I.K.S.); +82-2-3010-3936 (S.C.K.)
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10
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Vlahos AE, Kinney SM, Kingston BR, Keshavjee S, Won SY, Martyts A, Chan WC, Sefton MV. Endothelialized collagen based pseudo-islets enables tuneable subcutaneous diabetes therapy. Biomaterials 2020; 232:119710. [DOI: 10.1016/j.biomaterials.2019.119710] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 12/13/2019] [Accepted: 12/18/2019] [Indexed: 10/25/2022]
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11
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Espona-Noguera A, Ciriza J, Cañibano-Hernández A, Orive G, Hernández RM, Saenz del Burgo L, Pedraz JL. Review of Advanced Hydrogel-Based Cell Encapsulation Systems for Insulin Delivery in Type 1 Diabetes Mellitus. Pharmaceutics 2019; 11:E597. [PMID: 31726670 PMCID: PMC6920807 DOI: 10.3390/pharmaceutics11110597] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 11/05/2019] [Accepted: 11/06/2019] [Indexed: 12/11/2022] Open
Abstract
: Type 1 Diabetes Mellitus (T1DM) is characterized by the autoimmune destruction of β-cells in the pancreatic islets. In this regard, islet transplantation aims for the replacement of the damaged β-cells through minimally invasive surgical procedures, thereby being the most suitable strategy to cure T1DM. Unfortunately, this procedure still has limitations for its widespread clinical application, including the need for long-term immunosuppression, the lack of pancreas donors and the loss of a large percentage of islets after transplantation. To overcome the aforementioned issues, islets can be encapsulated within hydrogel-like biomaterials to diminish the loss of islets, to protect the islets resulting in a reduction or elimination of immunosuppression and to enable the use of other insulin-producing cell sources. This review aims to provide an update on the different hydrogel-based encapsulation strategies of insulin-producing cells, highlighting the advantages and drawbacks for a successful clinical application.
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Affiliation(s)
- Albert Espona-Noguera
- NanoBioCel Group, Laboratory of Pharmaceutics, School of Pharmacy, University of the Basque Country (UPV/EHU), Paseo de la Universidad 7, 01006 Vitoria-Gasteiz, Spain; (A.E.-N.); (J.C.); (A.C.-H.); (R.M.H.)
- Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), 01006 Vitoria-Gasteiz, Spain
| | - Jesús Ciriza
- NanoBioCel Group, Laboratory of Pharmaceutics, School of Pharmacy, University of the Basque Country (UPV/EHU), Paseo de la Universidad 7, 01006 Vitoria-Gasteiz, Spain; (A.E.-N.); (J.C.); (A.C.-H.); (R.M.H.)
- Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), 01006 Vitoria-Gasteiz, Spain
| | - Alberto Cañibano-Hernández
- NanoBioCel Group, Laboratory of Pharmaceutics, School of Pharmacy, University of the Basque Country (UPV/EHU), Paseo de la Universidad 7, 01006 Vitoria-Gasteiz, Spain; (A.E.-N.); (J.C.); (A.C.-H.); (R.M.H.)
- Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), 01006 Vitoria-Gasteiz, Spain
| | - Gorka Orive
- NanoBioCel Group, Laboratory of Pharmaceutics, School of Pharmacy, University of the Basque Country (UPV/EHU), Paseo de la Universidad 7, 01006 Vitoria-Gasteiz, Spain; (A.E.-N.); (J.C.); (A.C.-H.); (R.M.H.)
- Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), 01006 Vitoria-Gasteiz, Spain
- University Institute for Regenerative Medicine and Oral Implantology - UIRMI (UPV/EHU-Fundación Eduardo Anitua), 01006 Vitoria, Spain
- Singapore Eye Research Institute, The Academia, 20 College Road, Discovery Tower, Singapore 169856, Singapore
| | - Rosa María Hernández
- NanoBioCel Group, Laboratory of Pharmaceutics, School of Pharmacy, University of the Basque Country (UPV/EHU), Paseo de la Universidad 7, 01006 Vitoria-Gasteiz, Spain; (A.E.-N.); (J.C.); (A.C.-H.); (R.M.H.)
- Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), 01006 Vitoria-Gasteiz, Spain
| | - Laura Saenz del Burgo
- NanoBioCel Group, Laboratory of Pharmaceutics, School of Pharmacy, University of the Basque Country (UPV/EHU), Paseo de la Universidad 7, 01006 Vitoria-Gasteiz, Spain; (A.E.-N.); (J.C.); (A.C.-H.); (R.M.H.)
- Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), 01006 Vitoria-Gasteiz, Spain
| | - Jose Luis Pedraz
- NanoBioCel Group, Laboratory of Pharmaceutics, School of Pharmacy, University of the Basque Country (UPV/EHU), Paseo de la Universidad 7, 01006 Vitoria-Gasteiz, Spain; (A.E.-N.); (J.C.); (A.C.-H.); (R.M.H.)
- Biomedical Research Networking Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), 01006 Vitoria-Gasteiz, Spain
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12
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Chen YJ, Yamazoe T, Leavens KF, Cardenas-Diaz FL, Georgescu A, Huh D, Gadue P, Stanger BZ. iPreP is a three-dimensional nanofibrillar cellulose hydrogel platform for long-term ex vivo preservation of human islets. JCI Insight 2019; 4:124644. [PMID: 31672937 DOI: 10.1172/jci.insight.124644] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 09/20/2019] [Indexed: 01/12/2023] Open
Abstract
Islet transplantation is an effective therapy for achieving and maintaining normoglycemia in patients with type 1 diabetes mellitus. However, the supply of transplantable human islets is limited. Upon removal from the pancreas, islets rapidly disintegrate and lose function, resulting in a short interval for studies of islet biology and pretransplantation assessment. Here, we developed a biomimetic platform that can sustain human islet physiology for a prolonged period ex vivo. Our approach involved the creation of a multichannel perifusion system to monitor dynamic insulin secretion and intracellular calcium flux simultaneously, enabling the systematic evaluation of glucose-stimulated insulin secretion under multiple conditions. Using this tool, we developed a nanofibrillar cellulose hydrogel-based islet-preserving platform (iPreP) that can preserve islet viability, morphology, and function for nearly 12 weeks ex vivo, and with the ability to ameliorate glucose levels upon transplantation into diabetic hosts. Our platform has potential applications in the prolonged maintenance of human islets, providing an expanded time window for pretransplantation assessment and islet studies.
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Affiliation(s)
- Yi-Ju Chen
- Gastroenterology Division, Department of Medicine.,Department of Cell and Developmental Biology, and.,Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.,Genetic Resource Science, The Jackson Laboratory, Bar Harbor, Maine, USA
| | | | - Karla F Leavens
- Center for Cellular and Molecular Therapeutics, Department of Pathology and Laboratory Medicine.,Division of Endocrinology, Department of Pediatrics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Fabian L Cardenas-Diaz
- Center for Cellular and Molecular Therapeutics, Department of Pathology and Laboratory Medicine
| | - Andrei Georgescu
- Department of Bioengineering, School of Engineering and Applied Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Dongeun Huh
- Department of Bioengineering, School of Engineering and Applied Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Paul Gadue
- Center for Cellular and Molecular Therapeutics, Department of Pathology and Laboratory Medicine
| | - Ben Z Stanger
- Gastroenterology Division, Department of Medicine.,Department of Cell and Developmental Biology, and.,Abramson Family Cancer Research Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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13
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Abstract
Background It has been proposed that islet transplants comprised primarily of small rather than large islets may provide better graft function, due to their lower susceptibility to hypoxic damage. Our aim was to determine whether islet size correlated with in vivo graft function in islet transplant recipients with C peptide–negative type 1 diabetes when islets have undergone pretransplant islet culture. Methods Human pancreatic islets were isolated, cultured for 24 hours and infused by standardized protocols. Ninety-minute stimulated C-peptide concentrations were determined during a standard meal tolerance test 3 months posttransplant. The islet isolation index (IEq/islet number) was determined immediately after isolation and again before transplantation (after tissue culture). This was correlated with patient insulin requirement or stimulated C-peptide. Results Changes in insulin requirement did not significantly correlate with islet isolation index. Stimulated C-peptide correlated weakly with IEq at isolation (P = 0.40) and significantly with IEq at transplantation (P = 0.018). Stimulated C-peptide correlated with islet number at isolation (P = 0.013) and more strongly with the islet number at transplantation (P = 0.001). In contrast, the correlation of stimulated C-peptide and islet isolation index was weaker (P = 0.018), and this was poorer at transplantation (P = 0.034). Using linear regression, the strongest association with graft function was islet number (r = 0.722, P = 0.001). Islet size was not related to graft function after adjusting for islet volume or number. Conclusions These data show no clear correlation between islet isolation index and graft function; both small and large islets are suitable for transplantation, provided the islets have survived a short culture period postisolation. By analyzing the insulin requirements from 25 islet transplantation recipients, Hughes et al determined the strongest association with graft function was islet number while islet size was not related to graft function after adjusting for islet volume or number.
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14
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Huang HH, Harrington S, Stehno-Bittel L. The Flaws and Future of Islet Volume Measurements. Cell Transplant 2018; 27:1017-1026. [PMID: 29954219 PMCID: PMC6158542 DOI: 10.1177/0963689718779898] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 03/09/2018] [Accepted: 04/01/2018] [Indexed: 11/17/2022] Open
Abstract
When working with isolated islet preparations, measuring the volume of tissue is not a trivial matter. Islets come in a large range of sizes and are often contaminated with exocrine tissue. Many factors complicate the procedure, and yet knowledge of the islet volume is essential for predicting the success of an islet transplant or comparing experimental groups in the laboratory. In 1990, Ricordi presented the islet equivalency (IEQ), defined as one IEQ equaling a single spherical islet of 150 μm in diameter. The method for estimating IEQ was developed by visualizing islets in a microscope, estimating their diameter in 50 μm categories and calculating a total volume for the preparation. Shortly after its introduction, the IEQ was adopted as the standard method for islet volume measurements. It has helped to advance research in the field by providing a useful tool improving the reproducibility of islet research and eventually the success of clinical islet transplants. However, the accuracy of the IEQ method has been questioned for years and many alternatives have been proposed, but none have been able to replace the widespread use of the IEQ. This article reviews the history of the IEQ, and discusses the benefits and failings of the measurement. A thorough evaluation of alternatives for estimating islet volume is provided along with the steps needed to uniformly move to an improved method of islet volume estimation. The lessons learned from islet researchers may serve as a guide for other fields of regenerative medicine as cell clusters become a more attractive therapeutic option.
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Affiliation(s)
- Han-Hung Huang
- Angelo State University, Texas Tech University System, San Angelo, TX, USA
| | | | - Lisa Stehno-Bittel
- Likarda, LLC, Kansas City, MO, USA
- University of Kansas Medical Center, Kansas City, KS, USA
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15
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Buchwald P, Bernal A, Echeverri F, Tamayo-Garcia A, Linetsky E, Ricordi C. Fully Automated Islet Cell Counter (ICC) for the Assessment of Islet Mass, Purity, and Size Distribution by Digital Image Analysis. Cell Transplant 2018; 25:1747-1761. [PMID: 27196960 DOI: 10.3727/096368916x691655] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
For isolated pancreatic islet cell preparations, it is important to be able to reliably assess their mass and quality, and for clinical applications, it is part of the regulatory requirement. Accurate assessment, however, is difficult because islets are spheroid-like cell aggregates of different sizes (<50 to 500 μm) resulting in possible thousandfold differences between the mass contribution of individual particles. The current standard manual counting method that uses size-based group classification is known to be error prone and operator dependent. Digital image analysis (DIA)-based methods can provide less subjective, more reproducible, and better-documented islet cell mass (IEQ) estimates; however, so far, none has become widely accepted or used. Here we present results obtained using a compact, self-contained islet cell counter (ICC3) that includes both the hardware and software needed for automated islet counting and requires minimal operator training and input; hence, it can be easily adapted at any center and could provide a convenient standardized cGMP-compliant IEQ assessment. Using cross-validated sample counting, we found that for most human islet cell preparations, ICC3 provides islet mass (IEQ) estimates that correlate well with those obtained by trained operators using the current manual SOP method ( r2 = 0.78, slope = 1.02). Variability and reproducibility are also improved compared to the manual method, and most of the remaining variability (CV = 8.9%) results from the rearrangement of the islet particles due to movement of the sample between counts. Characterization of the size distribution is also important, and the present digitally collected data allow more detailed analysis and coverage of a wider size range. We found again that for human islet cell preparations, a Weibull distribution function provides good description of the particle size.
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Affiliation(s)
- Peter Buchwald
- Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL, USA.,Molecular and Cellular Pharmacology, Miller School of Medicine, University of Miami, Miami, FL, USA
| | | | | | | | - Elina Linetsky
- Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Camillo Ricordi
- Diabetes Research Institute, Miller School of Medicine, University of Miami, Miami, FL, USA
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16
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Shalaly ND, Ria M, Johansson U, Åvall K, Berggren PO, Hedhammar M. Silk matrices promote formation of insulin-secreting islet-like clusters. Biomaterials 2016; 90:50-61. [PMID: 26986856 DOI: 10.1016/j.biomaterials.2016.03.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 02/26/2016] [Accepted: 03/01/2016] [Indexed: 11/29/2022]
Abstract
Ex vivo expansion of endocrine cells constitutes an interesting alternative to be able to match the unmet need of transplantable pancreatic islets. However, endocrine cells become fragile once removed from their extracellular matrix (ECM) and typically become senescent and loose insulin expression during conventional 2D culture. Herein we develop a protocol where 3D silk matrices functionalized with ECM-derived motifs are used for generation of insulin-secreting islet-like clusters from mouse and human primary cells. The obtained clusters were shown to attain an islet-like spheroid shape and to maintain functional insulin release upon glucose stimulation in vitro. Furthermore, in vivo imaging of transplanted murine clusters showed engraftment with increasing vessel formation during time. There was no sign of cell death and the clusters maintained or increased in size throughout the period, thus suggesting a suitable cluster size for transplantation.
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Affiliation(s)
- Nancy Dekki Shalaly
- Division of Protein Technology, School of Biotechnology, KTH Royal Institute of Technology, S-106 91 Stockholm, Sweden
| | - Massimiliano Ria
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital, S-17176 Stockholm, Sweden
| | - Ulrika Johansson
- Division of Protein Technology, School of Biotechnology, KTH Royal Institute of Technology, S-106 91 Stockholm, Sweden
| | - Karin Åvall
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital, S-17176 Stockholm, Sweden
| | - Per-Olof Berggren
- The Rolf Luft Research Center for Diabetes and Endocrinology, Karolinska Institutet, Karolinska University Hospital, S-17176 Stockholm, Sweden
| | - My Hedhammar
- Division of Protein Technology, School of Biotechnology, KTH Royal Institute of Technology, S-106 91 Stockholm, Sweden; Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, S-750 07 Uppsala, Sweden.
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17
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Han S, Englander EW, Gomez GA, Rastellini C, Quertermous T, Kundu RK, Greeley GH. Pancreatic Islet APJ Deletion Reduces Islet Density and Glucose Tolerance in Mice. Endocrinology 2015; 156:2451-60. [PMID: 25965959 DOI: 10.1210/en.2014-1631] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Protection and replenishment of a functional pancreatic β-cell mass (BCM) are key goals of all diabetes therapies. Apelin, a small regulatory peptide, is the endogenous ligand for the apelin receptor (APJ) receptor. The apelin-APJ signaling system is expressed in rodent and human islet cells. Apelin exposure has been shown to inhibit and to stimulate insulin secretion. Our aim was to assess the influence of a selective APJ deletion in pancreatic islet cells on islet homeostasis and glucose tolerance in mice. Cre-LoxP strategy was utilized to mediate islet APJ deletion. APJ deletion in islet cells (APJ(Δislet)) resulted in a significantly reduced islet size, density and BCM. An ip glucose tolerance test showed significantly impaired glucose clearance in APJ(Δislet) mice. APJ(Δislet) mice were not insulin resistant and in vivo glucose-stimulated insulin secretion was reduced modestly. In vitro glucose-stimulated insulin secretion showed a significantly reduced insulin secretion by islets from APJ(Δislet) mice. Glucose clearance in response to ip glucose tolerance test in obese APJ(Δislet) mice fed a chronic high-fat (HF) diet, but not pregnant APJ(Δislet) mice, was impaired significantly. In addition, the obesity-induced adaptive elevations in mean islet size and fractional islet area were reduced significantly in obese APJ(Δislet) mice when compared with wild-type mice. Together, these findings demonstrate a stimulatory role for the islet cell apelin-APJ signaling axis in regulation of pancreatic islet homeostasis and in metabolic induced β-cell hyperplasia. The results indicate the apelin-APJ system can be exploited for replenishment of BCM.
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Affiliation(s)
- Song Han
- Department of Surgery (S.H., E.W.E., G.A.G., C.R., G.H.G.), University of Texas Medical Branch, Galveston, Texas 77555; and School of Medicine (T.Q., R.K.K.), Division of Cardiovascular Medicine, Stanford University, Stanford, California 94305
| | - Ella W Englander
- Department of Surgery (S.H., E.W.E., G.A.G., C.R., G.H.G.), University of Texas Medical Branch, Galveston, Texas 77555; and School of Medicine (T.Q., R.K.K.), Division of Cardiovascular Medicine, Stanford University, Stanford, California 94305
| | - Guillermo A Gomez
- Department of Surgery (S.H., E.W.E., G.A.G., C.R., G.H.G.), University of Texas Medical Branch, Galveston, Texas 77555; and School of Medicine (T.Q., R.K.K.), Division of Cardiovascular Medicine, Stanford University, Stanford, California 94305
| | - Cristiana Rastellini
- Department of Surgery (S.H., E.W.E., G.A.G., C.R., G.H.G.), University of Texas Medical Branch, Galveston, Texas 77555; and School of Medicine (T.Q., R.K.K.), Division of Cardiovascular Medicine, Stanford University, Stanford, California 94305
| | - Thomas Quertermous
- Department of Surgery (S.H., E.W.E., G.A.G., C.R., G.H.G.), University of Texas Medical Branch, Galveston, Texas 77555; and School of Medicine (T.Q., R.K.K.), Division of Cardiovascular Medicine, Stanford University, Stanford, California 94305
| | - Ramendra K Kundu
- Department of Surgery (S.H., E.W.E., G.A.G., C.R., G.H.G.), University of Texas Medical Branch, Galveston, Texas 77555; and School of Medicine (T.Q., R.K.K.), Division of Cardiovascular Medicine, Stanford University, Stanford, California 94305
| | - George H Greeley
- Department of Surgery (S.H., E.W.E., G.A.G., C.R., G.H.G.), University of Texas Medical Branch, Galveston, Texas 77555; and School of Medicine (T.Q., R.K.K.), Division of Cardiovascular Medicine, Stanford University, Stanford, California 94305
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