Aims of Study
Transplantation / regenerative strategies hold the key to a potential cure for millions of children with type 1 diabetes and hence is of huge relevance to paediatric surgeons. Islet transplantation has been very successful in selected adults, but the current requirement for systemic immunosuppression prevents its implementation in children. Development of novel implantable islet-containing devices that secrete drugs locally to the islets offers real translational potential. This study aimed to investigate the impact of the immunosuppressant Tacrolimus and the anti-TNF agent Etanercept (commonly used agents) on human islet integrity.
Isolated human islets (n=8) were cultured in hypoxia (2% O2) for 3–4 days at 37ºC in CMRL 1066 supplemented with either 12.5 ng/mL of Tacrolimus and/or 5 µg/mL of Etanercept. Subsequently, detailed islet characterisation was performed and data normalised to sham-treated controls.
5µg/mL of Etanercept applied alone or combined with Tacrolimus protected islet yield (153±9%), fragmentation (64±5%) and viability (122±11%) (P<0.001 vs. controls). Tacrolimus alone neither improved islet viability (105±2%, P<0.05 vs. Etanercept), nor islet loss (118±3%, P<0.05) nor fragmentation (84±4%, P<0.05). Etanercept-treated islets had the highest insulin stimulation index (3.6±0.8) compared with controls (1.5±0.2, P<0.001) and Tacrolimus used alone (2.1±0.2, P<0.05) or when combined with Etanercept (2.0±0.1, P<0.05). TNFa gene expression of Tacrolimus-treated islets was increased (176±55%, P<0.05) compared with controls (101±1%) and Etanercept-treated islets (118±27%). TNFa mRNA correlated with the Bax/Bcl2 mRNA ratio after Tacrolimus (1.9±0.5) and ETA (0.9±0.2, P<0.01) treatment.
This is the first study to investigate the effects of Etanercept on isolated human islets. The anti-inflammatory impact of Etanercept is strongly expressed and provides significant protection for human islets exposed to hypoxia. This agent will be tested in locally-secreting islet devices.