Sobreexpressió de lAntagonista del Receptor dInterleucina 1 (IL-1Ra) en els illots pancreàtics .Efectes sobre viabilitat, funció i regeneració de les cèl·lules beta.
SUMMARY: BACKGROUND AND AIMS: IL-1beta could contribute to the dramatic beta cell loss that takes place after islet transplantation. It is known that exposure to sustained hyperglycemia has a deleterious effect on transplanted islets. Moreover, it has been recently reported that IL-1beta expression is increased in islets exposed to high glucose levels. IL-1Ra is a naturally occurring inhibitor of IL-1 action and its overexpression protects pancreatic islets from the deleterious effects of IL-1â on beta cell replication, apoptosis and function. The aim of this study was to determine whether viral gene transfer of the IL-1Ra gene into rat islets ex vivo could have a beneficial effect on beta cell replication and mass of transplanted islets. METHODS: Lewis rat islets were infected for 2h with 6.25 × 106 pfu of Ad-IL-1Ra and streptozotocin-diabetic Lewis rats were transplanted with 500 Ad-IL-1Ra infected islets (Ad-IL-1Ra group) or 500 uninfected islets (control group) under the kidney capsule. Grafts were removed 3 (n = 12), 10 (n = 12) and 28 (n = 12) days after transplantation and beta cell replication, apoptosis and mass were determined. RESULTS: 500 islets is an insufficient mass to restore normoglycemia and therefore, all animals but one (IL-1Ra group) remained hyperglycemic until the end of the study. Beta cell replication (determined by BrdU incorporation) was significantly increased in Ad-IL-1Ra group on days 3 (0.78 ± 0.23%), 10 (1.15 ± 0.16%) and 28 (1.22 ± 0.2%) after islet transplantation compared to beta cell replication in normal pancreas (0.24 ± 0.04%; p< 0.05). In contrast, in control group, beta cell replication was not increased on day 3 after transplantation (0.41 ± 0.11%), and although it increased on day 10 (0.89 ± 0.18%; p< 0.01) it was reduced again on day 28 (0.59 ± 0.10%) in agreement with previous reports of limited beta cell replication with persistent hyperglycemia. Beta cell apoptosis (determined by TUNEL method) was significantly increased in transplanted islets from both groups compared to pancreas. Although Ad-IL-1Ra group showed lower beta cell apoptotic levels than control group, differences did not reach statistical significance. The initially transplanted â-cell mass (1.34 ± 0.03 mg) was similarly reduced in both control (0.32 ± 0.06 mg) and Ad-IL-1Ra groups (0.45 ± 0.10 mg) (p<0.001) on day 3 after transplantation. In Ad-IL-1Ra islet grafts, beta cell mass increased after 10 (1.04 ± 0.091 mg; p< 0.010) and 28 (0.8 ± 0.24 mg) days of transplantation. In contrast, beta cell mass of control group was also increased on day 10 after transplantation (0.69 ± 0.12 mg), but it dropped again on day 28 (0.41 ± 0.05 mg) paralleling with the evolution of beta cell replication in this group. CONCLUSIONS: Islets overexpressing IL-1Ra showed an increased beta cell replication and a preserved beta cell mass after transplantation, that was maintained even after longterm exposure to hyperglycemia.
Advisor:Montanya Mias, Eduard
School:Universitat de Barcelona
Source Type:Master's Thesis
Date of Publication:02/14/2007