Introduction: Intraportal (IP) islet cell transplants can restore metabolic control in type 1 diabetes patients, but limitations raise the need for establishing a functional beta cell mass (FBM) in a confined extrahepatic site.
Methods: This study reports on function and composition of omental (OM) implants after placement of islet cell grafts with similar beta cell mass as in our IP-protocol (25.106 beta cells/kg body weight)
Results: Four of seven C-peptide-negative recipients achieved low beta cell function (hyperglycemic clamp [HGC] 28 percent of controls) until laparoscopy, 26 months later, for OM-biopsy and concomitant IP-transplant with similar beta cell dose. This IP-transplant increased HGC-values to 1540 percent. OM-biopsies reflected the composition of initial grafts, exhibiting varying proportions of endocrine- cell-enriched clusters with more beta than alpha cells and leucocyte pole, non-endocrine cytokeratin- positive clusters surrounded by leucocytes, and scaffold remnants with foreign body reaction. OM- implants on a polyglactin-thrombin-fibrinogen-scaffold presented larger endocrine clusters with infiltrating endothelial cells and corresponded to the higher HGC-values. No activation of cellular immunity to GAD/IA2 was measured post-OM-transplant.
Conclusion: Establishment of a metabolically adequate FBM in omentum may require a higher beta cell number in grafts but also elimination of their immunogenic non-endocrine components as well as local conditioning that favors endocrine cell engraftment and function.