Infusing pancreatic islets into the portal vein currently represents the preferred approach for islet transplantation, despite considerable loss of islet mass almost immediately after implantation. Therefore, approaches that obviate direct intravascular placement are urgently needed. A promising candidate for extrahepatic placement is the omentum. We aimed to develop an extracellular matrix skeleton from the native pancreas that could provide a microenvironment for islet survival in an omental flap. To that end, we compared different decellularization approaches, including perfusion through the pancreatic duct, gastric artery, portal vein, and a novel method through the splenic vein. Decellularized skeletons were compared for size, residual DNA content, protein composition, histology, electron microscopy, and MR imaging after repopulation with isolated islets. Compared to the other approaches, pancreatic perfusion via the splenic vein provided smaller extracellular matrix skeletons, which facilitated transplantation into the omentum, without compromising other requirements, such as the complete depletion of cellular components and the preservation of pancreatic extracellular proteins. Repeated MR imaging of iron-oxide-labeled pancreatic islets showed that islets maintained their position in vivo for 49 days. Advanced environmental scanning electron microscopy demonstrated that islets remained integrated with the pancreatic skeleton. This novel approach represents a proof-of-concept for long-term transplantation experiments.
- Publikační typ
- časopisecké články MeSH
- Publikační typ
- abstrakt z konference MeSH
BACKGROUND: Transplantation of pancreatic islets into subcutaneous cavities in diabetic rats may be as or even more effective than transplantation into the portal vein. Identifying the optimal timing of the individual steps in this procedure is critical. METHODS: Macroporous scaffolds were placed in the subcutaneous tissue of diabetic male Lewis rats for 7 or 28 d and the healing of the tissue inside the scaffolds was monitored. A marginal syngeneic graft comprising 4 islets/g of recipient body weight was transplanted at the best timing focusing mainly on vascularization. Recipients were monitored for blood glucose levels and tolerance tests. Histological examination was performed in all implanted scaffolds. The presence of individual endocrine cells was analyzed in detail. RESULTS: Blood glucose levels remained within the physiological range in all recipients until the end of experiment as well as body weight increase. Coefficients of glucose assimilation were normal or slightly reduced with no statistically significant differences between the groups 40 and 80 d after transplantation. Histological analysis revealed round viable islets in the liver similar to those in pancreas, but alpha cells practically disappeared, whereas islets in the scaffolds formed clusters of cells surrounded by rich vascular network and the alpha cells remained partially preserved. CONCLUSIONS: Subcutaneous transplantation of pancreatic islets is considerably less invasive but comparably efficient as commonly used islet transplantation into the portal vein. In consideration of alpha and beta cell ratio, the artificial subcutaneous cavities represent a promising site for future islet transplantation therapy.
- MeSH
- experimentální diabetes mellitus * chirurgie MeSH
- krevní glukóza MeSH
- krysa rodu rattus MeSH
- Langerhansovy ostrůvky * krevní zásobení chirurgie MeSH
- potkani inbrední LEW MeSH
- subkutánní tkáň MeSH
- transplantace Langerhansových ostrůvků * metody MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Transplantace Langerhansových ostrůvků představuje zavedenou metodu léčby pacientů s diabetem 1. typu se syndromem porušeného vnímání hypoglykemie, u kterých selhává použití moderních technologických postupů. Nejčastěji se jedná o radiointervenční metodu, při které se suspenze pankreatických ostrůvků podává perkutánně zavedeným katétrem do větve portální žíly. Ačkoliv se na rozdíl od orgánové transplantace pankreatu jedná o výkon jen minimálně invazivní, řada technických problémů zůstává nevyřešena. Mezi možné komplikace patří zejména krvácení a trombóza portální žíly. Na rozdíl od svého přirozeného umístění disperzně ve tkáni exokrinního pankreatu jsou izolované transplantované ostrůvky v jaterním parenchymu vystaveny bezprostřední hypoxii, přímému působení toxinů a imunosupresivních léčiv. Přímý kontakt s krví příjemce vyvolává bezprostřední zánětlivou reakci, tzv. IBMIR (instant blood mediated inflammatory reaction), díky které i více než polovina transplantovaných buněk po aplikaci zaniká. Velikost ostrůvkového štěpu je proto často nedostatečná a řada pacientů potřebuje po výkonu určité množství exogenního inzulinu. To všechno jsou důvody, proč hledáme pro ostrůvkový štěp jiné místo transplantace s příznivějšími podmínkami pro dlouhodobé přežívání. V experimentálním i klinickém výzkumu byla zkoušena různá aplikační místa, jejichž výhody a nevýhody shrneme v tomto sdělení. Jako nejnadějnější se v současné době jeví transplantace do velkého omenta, která již byla na několika pracovištích klinicky použita.
Pancreatic islets transplantation is an established treatment method for type 1 diabetic patients with the hypoglycemia unawareness syndrome in whom a therapy with modern technologies fails. Islet transplantation is most commonly done using an interventional radiology method: a tissue suspension of pancreatic islets is applied into a branch of the portal vein through a percutaneously installed catheter. Although being minimally invasive unlike pancreas organ transplant, this method is associated with many technical difficulties. Possible complications of the procedure include hemorrhage and portal vein thrombosis. Unlike their natural dispersed localization in exocrine pancreas, isolated pancreatic islets are exposed to hypoxia, toxins and immunosuppressive drugs in the liver parenchyma. Direct contact with the recipient’s blood causes an instant blood mediated inflammatory reaction (IBMIR) resulting in the death of more than half of the pancreatic islets shortly after their application. Therefore the size of the islet graft is often insufficient and a number of transplanted patients require administration of exogenous insulin. All of these are reasons for seeking an alternative transplantation site with more hospitable conditions for long-term islet survival. Various transplantation sites have been tested in experimental and clinical research. The advantages and disadvantages of some of them are summarized in this paper. Currently, transplantation into the greater omentum seems most promising, which has already been used in clinical practice at several institutions.
- Klíčová slova
- syndrom porušeného vnímání hypoglykemie,
- MeSH
- diabetes mellitus 1. typu chirurgie MeSH
- lidé MeSH
- omentum MeSH
- transplantace Langerhansových ostrůvků * metody MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- práce podpořená grantem MeSH
- přehledy MeSH
PURPOSE: The liver is the most widely used site for pancreatic islet transplantation. However, several site-specific limitations impair functional success, with instant blood-mediated inflammatory reaction being the most important. The aim of this study was to develop a preclinical model for placement of the islet graft into a highly vascularized omental flap using a fibrin gel. For this purpose, we tested islet viability by bioluminescence imaging (BLI). PROCEDURES: Pancreatic islets were isolated from luciferase-positive and luciferase-negative rats, mixed at a 1:1 ratio, placed into a plasma-thrombin bioscaffold, and transplanted in standard (10 pancreatic islets/g wt; n = 10) and marginal (4 pancreatic islets/g wt; n = 7) numbers into the omentums of syngeneic diabetic animals. For the control, 4 pancreatic islets/g were transplanted into the liver using the standard procedure (n = 7). Graft viability was tested by bioluminescence at days 14, 30, 60, and 90 post transplant. Glucose levels, intravenous glucose tolerance, and serum C-peptide were assessed regularly. RESULTS: Nonfasting glucose levels < 10 mmol/l were restored in all animals. While islet viability in the omentum was clearly detected by stable luminescence signals throughout the whole study period, no signals were detected from islets transplanted into the liver. The bioluminescence signals were highly correlated with stimulated C-peptide levels detected at 80 days post transplant. Glucose tolerance did not differ among the 3 groups. CONCLUSIONS: We successfully tested a preclinical model of islet transplantation into the greater omentum using a biocompatible scaffold made from autologous plasma and human thrombin. Both standard and marginal pancreatic islet numbers in a gel-form bioscaffold placed in the omentum restored glucose homeostasis in recipients with diabetes. Bioluminescence was shown promising as a direct proof of islet viability.
- MeSH
- krysa rodu rattus MeSH
- Langerhansovy ostrůvky diagnostické zobrazování MeSH
- luminiscenční měření metody MeSH
- molekulární zobrazování metody MeSH
- omentum diagnostické zobrazování MeSH
- přežívání štěpu fyziologie MeSH
- transplantace Langerhansových ostrůvků * MeSH
- viabilita buněk fyziologie MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The effectiveness of cell transplantation can be improved by optimization of the transplantation site. For some types of cells that form highly oxygen-demanding tissue, e.g., pancreatic islets, a successful engraftment depends on immediate and sufficient blood supply. This critical point can be avoided when cells are transplanted into a bioengineered pre-vascularized cavity which can be formed using a polymer scaffold. In our study, we tested surface-modified poly(lactide-co-caprolactone) (PLCL) capsular scaffolds containing the pro-angiogenic factor VEGF. After each modification step (i.e., amination and heparinization), the surface properties and morphology of scaffolds were characterized by ATR-FTIR and XPS spectroscopy, and by SEM and AFM. All modifications preserved the gross capsule morphology and maintained the open pore structure. Optimized aminolysis conditions decreased the Mw of PLCL only up to 10% while generating a sufficient number of NH2 groups required for the covalent immobilization of heparin. The heparin layer served as a VEGF reservoir with an in vitro VEGF release for at least four weeks. In vivo studies revealed that to obtain highly vascularized PLCL capsules (a) the optimal VEGF dose for the capsule was 50 μg and (b) the implantation time was four weeks when implanted into the greater omentum of Lewis rats; dense fibrous tissue accompanied by vessels completely infiltrated the scaffold and created sparse granulation tissue within the internal cavity of the capsule. The prepared pre-vascularized pouch enabled the islet graft survival and functioning for at least 50 days after islet transplantation. The proposed construct can be used to create a reliable pre-vascularized pouch for cell transplantation.
- MeSH
- bioinženýrství * MeSH
- experimentální diabetes mellitus chemicky indukované metabolismus patologie MeSH
- fyziologická neovaskularizace * MeSH
- injekce intraperitoneální MeSH
- krevní glukóza analýza MeSH
- krysa rodu rattus MeSH
- molekulární struktura MeSH
- polyestery chemie metabolismus MeSH
- potkani inbrední LEW MeSH
- streptozocin aplikace a dávkování MeSH
- tobolky chemie metabolismus MeSH
- transplantace Langerhansových ostrůvků * MeSH
- vaskulární endoteliální růstové faktory chemie metabolismus MeSH
- velikost částic MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
PURPOSE: Combining specific and quantitative F-19 magnetic resonance imaging (MRI) with sensitive and convenient optical imaging provides complementary information about the distribution and viability of transplanted pancreatic islet grafts. In this study, pancreatic islets (PIs) were labeled with positively charged multimodal nanoparticles based on poly(lactic-co-glycolic acid) (PLGA-NPs) with encapsulated perfluoro-15-crown-5-ether and the near-infrared fluorescent dye indocyanine green. PROCEDURES: One thousand and three thousand bioluminescent PIs were transplanted into subcutaneous artificial scaffolds, which served as an alternative transplant site. The grafts were monitored using in vivo F-19 MR, fluorescence, and bioluminescence imaging in healthy rats for 2 weeks. RESULTS: Transplanted PIs were unambiguously localized in the scaffolds by F-19 MRI throughout the whole experiment. Fluorescence was detected in the first 4 days after transplantation only. Importantly, in vivo bioluminescence correlated with the F-19 MRI signal. CONCLUSIONS: We developed a trimodal imaging platform for in vivo examination of transplanted PIs. Fluorescence imaging revealed instability of the fluorescent dye and its limited applicability for longitudinal in vivo studies. A correlation between the bioluminescence signal and the F-19 MRI signal indicated the fast clearance of PLGA-NPs from the transplantation site after cell death, which addresses a major issue with intracellular imaging labels. Therefore, the proposed PLGA-NP platform is reliable for reflecting the status of transplanted PIs in vivo.
- MeSH
- endocytóza MeSH
- fluor chemie MeSH
- fluorescence MeSH
- Langerhansovy ostrůvky diagnostické zobrazování MeSH
- luminiscenční měření * MeSH
- magnetická rezonanční tomografie * MeSH
- modely u zvířat MeSH
- molekulární zobrazování * MeSH
- potkani inbrední LEW MeSH
- potkani transgenní MeSH
- přežití tkáně MeSH
- tkáňové podpůrné struktury chemie MeSH
- transplantace Langerhansových ostrůvků * MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Instant Blood-Mediated Inflammatory Reaction (IBMIR) is a major cause of graft loss during pancreatic islet transplantation, leading to a low efficiency of this treatment method and significantly limiting its broader clinical use. Within the procedure, transplanted islets obstruct intrahepatic portal vein branches and consequently restrict blood supply of downstream lying liver tissue, resulting typically in ischemic necrosis. The extent of ischemic lesions is influenced by mechanical obstruction and inflammation, as well as subsequent recanalization and regeneration capacity of recipient liver tissue. Monitoring of immediate liver perfusion impairment, which is directly related to the intensity of post-transplant inflammation and thrombosis (IBMIR), is essential for improving therapeutic and preventive strategies to improve overall islet graft survival. In this study, we present a new experimental model enabling direct quantification of liver perfusion impairment after pancreatic islet transplantation using ligation of hepatic arteries followed by contrast-enhanced magnetic resonance imaging (MRI). The ligation of hepatic arteries prevents the contrast agent from circumventing the portal vein obstruction and enables to discriminate between well-perfused and non-perfused liver tissue. Here we demonstrate that the extent of liver ischemia reliably reflects the number of transplanted islets. This model represents a useful tool for in vivo monitoring of biological effect of IBMIR-alleviating interventions as well as other experiments related to liver ischemia. This technical paper introduces a novel technique and its first application in experimental animals.
- MeSH
- embolie * komplikace diagnóza MeSH
- ischemie * diagnostické zobrazování etiologie MeSH
- játra * krevní zásobení diagnostické zobrazování patologie MeSH
- krysa rodu rattus MeSH
- magnetická rezonanční angiografie metody MeSH
- přežívání štěpu MeSH
- reprodukovatelnost výsledků MeSH
- teoretické modely MeSH
- transplantace Langerhansových ostrůvků škodlivé účinky MeSH
- vena portae * MeSH
- vylepšení obrazu metody MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Publikační typ
- abstrakt z konference MeSH
