High-Efficiency, Prevascularization-Free Macroencapsulation System for Subcutaneous Transplantation of Pancreatic Islets for Enhanced Diabetes Treatment.

Pancreatic islet macroencapsulation systems for subcutaneous transplantation have garnered significant attention as a therapy for Type I diabetes due to their minimal invasiveness and low complication rates. However, the low vascular density of subcutaneous tissue threatens the long-term survival of islets. To address this issue, prevascularized systems are introduced but various challenges remain, including system complexity and vascular-cell immunogenicity. Here, a novel prevasculature-free macroencapsulation system designed as a multilayer sheet, which ensures sufficient mass transport even in regions with sparse vasculature, is presented. Islets are localized in top/bottom micro-shell layers (≈300 µm thick) to maximize proximity to the surrounding host vasculature. These sheets, fabricated via bioprinting using rat islets and alginate-based bio-ink, double islet viability and optimize islet density, improving insulin secretion function by 240%. The subcutaneous transplantation of small islet masses (≈250 islet equivalent) into diabetic nude mice enable rapid (<1 day) recovery of blood glucose, which remain stable for >120 days. Additionally, antifibrotic drug-loaded multilayer sheets facilitate blood glucose regulation by rat islets at the subcutaneous sites of diabetic immunocompetent mice for >35 days. Thus, this macroencapsulation system can advance the treatment of Type I diabetes and is also effective for islet xenotransplantation in subcutaneous tissue.