In vivo studies on insulin permeability of an immunoisolation device intended for islet transplantation using the microdialysis technique

In this study, insulin was injected into Theracyte(TM) immunoisolation devi ces to analyze changes in the permeability of the device over time after im plantation. The recovery of insulin was studied after subcutaneous implanta tion of the devices in rats, using the microdialysis technique. The area un der the insulin cocnetration vs. time curves (AUC) after insulin injection in devices implanted 1 day previously did not differ significantly from the AUC after subcutaneous injection. At 1 2 and 4 weeks after implantation, t he recovery of insulin was significantly reduced, but at 3 months, the AUC was not significantly different from that in the control group. Histologica l examination showed that the number of vascular profiles within 15 mu m of the device were significantly higher at 2, 4 weeks and 3 months after tran splantation when compared to numbers at 1 week. The design of the device al lows transplantation of cells at a chosen time point after its implantation . Delayed filling of the device would allow neovascularization of the devic e surface before graft implanatation and we suggest that such a schedule mi ght improve function of the encapsulated graft.