Purpose/Objective: Bioprinting human islets (HI) for beta-cell replacement therapy for treating type 1 diabetes (T1D) holds immense potential but faces challenges due to shear-induced HI damage, reduced functionality, and HI aggregation. Previous studies have mainly focused on animal-derived islets, with limited research addressing HI-specific bioink optimization and bioprinting parameters. This study aims to develop a scalable HI bioprinting methodology that preserves islet viability, functionality, and construct structural integrity for clinical applications.

Methodology: HI were bioprinted in clinically applicable alginate-based bioinks, supplemented with decellularized human pancreatic extracellular matrix (dECM). Bioinks were optimized for rheological behavior, shear-thinning properties, and mechanical stability. Constructs were printed with an extrusion-based bioprinter using optimized parameters to minimize HI shear stress. Viability and functionality were assessed via live/dead assays, glucose-stimulated insulin secretion (GSIS), and immunostaining over 21 days in culture. Construct pore size and mechanical stability were evaluated for structural integrity, while high-density bioprinting (10,000 iEQ/mL) addressed scalability challenges.

Results: The optimized bioprinting parameters resulted in over 90% viability of HI (2,500 iEQ/mL, N=3 donors), with stable stimulus index (SI) comparable to free islets over 7 days. High-density printing demonstrated the potential for volumetric tissue manufacturing. The printing conditions resulted in over 90% viability and a significantly higher SI on day 21 compared to free islets (3.7 ± 0.6 vs. 2.6 ± 0.4). dECM-enriched constructs demonstrated long-term HI viability, with a significant absence of glucagon-insulin co-expressing cells.

Conclusions/significance: This study has established a HI bioprinting platform for T1D therapy, by optimizing bioink formulations and printing parameters that resulted in enhanced HI viability, functionality, and construct structural stability. Functional high-density HI constructs were also successfully printed, paving the way for therapeutic applications. This strategy could address the delivery system requirements of various groups developing clinically relevant beta-cell replacement therapies.