RÉSUMÉ
Mesenchymal stem cells (MSC) are of interest for cell therapy since their secreted factors mediate immunomodulation and support tissue regeneration. This study investigated the direct humoral interactions between MSC and pancreatic ß-cells using human telomerase-immortalized MSC (hMSC-TERT) and rat insulinoma-derived INS-1E ß-cells. hMSC-TERT supported survival of cocultured INS-1E ß-cells during cellular stress by alloxan (ALX) and streptozotocin (STZ), but not in response to IL-1ß. Accordingly, hMSC-TERT had no effect on inflammatory cytokine-related signalling via NF-kB and p-JNK but maintained p-Akt and upregulated p-ERK1/2. Inhibition of either p-Akt or p-ERK1/2 did not abolish protection by hMSC-TERT but activated the respective non-inhibited pathway. This suggests that one pathway compensates for the other. Main results were confirmed in mouse islets except hMSC-TERT-mediated upregulation of p-ERK1/2. Therefore, MSC promote ß-cell survival by preservation of p-Akt signalling and further involve p-ERK1/2 activation in certain conditions such as loss of p-Akt or insulinoma background.
Sujet(s)
Cellules à insuline/enzymologie , Cellules à insuline/anatomopathologie , Insuline/biosynthèse , Système de signalisation des MAP kinases , Cellules souches mésenchymateuses/cytologie , Protéines proto-oncogènes c-akt/métabolisme , Stress physiologique , Alloxane , Animaux , Caspase-3/métabolisme , Caspase-7/métabolisme , Mouvement cellulaire/effets des médicaments et des substances chimiques , Survie cellulaire/effets des médicaments et des substances chimiques , Cytoprotection/effets des médicaments et des substances chimiques , Humains , Interleukine-1 bêta/pharmacologie , Système de signalisation des MAP kinases/effets des médicaments et des substances chimiques , Souris de lignée C57BL , Facteur de transcription NF-kappa B/métabolisme , Phosphorylation/effets des médicaments et des substances chimiques , Poly(ADP-ribose) polymerases/métabolisme , Rat Wistar , Streptozocine , Stress physiologique/effets des médicaments et des substances chimiques , Telomerase/métabolismeRÉSUMÉ
Islet cell transplantation is a promising option for the restoration of normal glucose homeostasis in patients with type 1 diabetes. Because graft volume is a crucial issue in islet transplantations for patients with diabetes, we evaluated a new method for increasing functional tissue yield in xenogeneic grafts of encapsulated islets. Islets were labeled with three different superparamagnetic iron oxide nano particles (SPIONs; dextran-coated SPION, siloxane-coated SPION, and heparin-coated SPION). Magnetic separation was performed to separate encapsulated islets from the empty capsules, and cell viability and function were tested. Islets labeled with 1000 µg Fe/ml dextran-coated SPIONs experienced a 69.9% reduction in graft volume, with a 33.2% loss of islet-containing capsules. Islets labeled with 100 µg Fe/ml heparin-coated SPIONs showed a 46.4% reduction in graft volume, with a 4.5% loss of capsules containing islets. No purification could be achieved using siloxane-coated SPIONs due to its toxicity to the primary islets. SPION labeling of islets is useful for transplant purification during islet separation as well as in vivo imaging after transplantation. Furthermore, purification of encapsulated islets can also reduce the volume of the encapsulated islets without impairing their function by removing empty capsules.
Sujet(s)
Séparation cellulaire/méthodes , Composés du fer III , Transplantation d'ilots de Langerhans/méthodes , Ilots pancréatiques/cytologie , Magnétisme , Nanoparticules , Transplantation hétérologue/méthodes , Animaux , Numération cellulaire , Survie cellulaire/physiologie , Dextrane , Héparine , Humains , Ilots pancréatiques/physiologie , Imagerie par résonance magnétique , Rats , Rat Wistar , SiloxanesRÉSUMÉ
We describe the results of the first study to show that adult rat and human islets can be protected against xenogenic rejection in immunocompetent diabetic mice by encapsulating them in a novel alginate-based microcapsule system with no additional permselective membrane. Nonencapsulated islets lost function within 4-8 days after being transplanted into diabetic Balb/c mice, whereas transplanted encapsulated adult rat or human islets resulted in normoglycemia for >7 months. When rat islet grafts were removed 10 and 36 weeks after transplantation, the mice became immediately hyperglycemic, thus demonstrating the efficacy of the encapsulated islets. The explanted capsules showed only a mild cellular reaction on their surface and a viability of >85%, and responded to a glucose stimulus with a 10-fold increase in insulin secretion. Furthermore, transplanted mice showed a slight decrease in the glucose clearance rate in response to intraperitoneal glucose tolerance tests 3-16 weeks after transplantation; after 16 weeks, the rate remained stable. Similar results were obtained for encapsulated human islets. Thus we provide the first evidence of successful transplantation of microencapsulated human islets. In conclusion, we have developed a novel microcapsule system that enables survival and function of adult rat and human islets in immunocompetent mice without immunosuppression for >7 months.
Sujet(s)
Alginates/composition chimique , Diabète/thérapie , Acide glucuronique/composition chimique , Survie du greffon/physiologie , Acides hexuroniques/composition chimique , Transplantation d'ilots de Langerhans/méthodes , Ilots pancréatiques/physiologie , Adulte , Animaux , Glycémie/métabolisme , Capsules/composition chimique , Humains , Insuline/métabolisme , Sécrétion d'insuline , Ilots pancréatiques/métabolisme , Mâle , Souris , Souris de lignée BALB C , Rats , Facteurs tempsRÉSUMÉ
Optimising microencapsulation technology towards the effective clinical transplantation has created the need for highly biocompatible alginates. Therefore, in this study the biocompatibility of different beads prepared from alginates with varying average molecular weight was examined. In some experiments the beads were covered with a multilayer membrane surrounded by an alginate layer. First of all, we found that beads made of a lower weight average alginate elicted a much stronger fibrotic response compared to beads made of a higher weight average alginate (LV-alginate > MV-alginate). The results were confirmed by the observation that the extent of tissue fibrosis was significantly increased in multilayer capsules made of an alginate with a lower weight average (core and surface LV-alginate, Mw 0.7-1 * 10(6) g/mol, viscosity of a 0.1% solution 1-2.5 mPa s(-1)) compared to multilayer capsules made of an alginate with a higher weight average (core and surface MV-alginate; Mw 1.2-1.3 * 10(6) g/mol, viscosity of a 0.1% solution 5-7 mPa s(-1)). It should be stressed, that the pro-fibrotic effect of the LV-alginate alginate in the core was only partially reversed by a MV-alginate on the surface of the multilayer capsules. On the basis of the raised data, it can be assumed that the molecular weight average of the alginates have an decisive effect on the biocompatibility. Therefore, it seems to be recommendable to reduce the low molecular weight fractions of the alginate during the purification process to improve the biocompatibility.