Introduction: Diabetes mellitus is a chronic, globally prevalent disease caused by dysfunction of pancreatic islet cells. Standard treatments, including insulin therapy and islet transplantation, do not fully restore physiological glycemic control or promote tissue regeneration. This has fueled the development of 3D bioprinted pancreatic organoids that mimic the structure and function of native islets. These constructs offer great promise for disease modeling, drug testing, and regenerative medicine. Using multicellular organoids composed of α, β, endothelial, and stromal cells allows better replication of the physiological microenvironment. Moreover, the addition of decellularized extracellular matrix (dECM) to bioinks has been shown to improve cell viability and endocrine function.
 

Aim: This study aimed to evaluate the viability and functionality of 3D bioprinted pancreatic organoids, designed to mimic islets of Langerhans, using bioinks with and without dECM.
 

Materials & Methods: Organoids were fabricated via inkjet-based 3D bioprinting using two bioink formulations: (1) base hydrogel containing 10% (w/v) gelatin methacrylate (GELMA), 1% (w/v) hyaluronic acid methacrylate (HAMA), 0.25% (w/v) LAP, and 10% cell suspension (5×10⁶ cells/mL); (2) the same formulation enriched with dECM. Four cell types were used: αTC-1 (α cells), βTC-tet (β cells), HUVECs (endothelial cells), and L929 (fibroblasts). Six organoid variants were created:

• V1–V2: αTC-1:βTC-tet (ratios 1:2 and 1:3)
• V3–V4: αTC-1:βTC-tet + HUVECs (50% and 25%)
• V5–V6: αTC-1:βTC-tet + HUVECs:L929 (50% and 25%)

Organoids were cultured for 28 days. Analyses included FDA/PI viability staining, microscopy, H&E staining, and immunohistochemistry for insulin, glucagon, CD31, and vimentin. β-cell functionality was assessed via glucose-stimulated insulin secretion (GSIS).

Results: All organoid variants maintained viability throughout 28 days. dECM-enriched bioinks significantly improved cell survival, with FDA/PI staining indicating near-complete viability in those constructs. Non-dECM variants showed slightly lower viability, but still adequate for testing. V5 and V6 formed spheroid-like aggregates as early as day 7. Immunohistochemical analysis confirmed the presence of α and β cells, endothelial structures, and fibroblast populations. All groups secreted insulin in response to glucose, with the V6 construct (dECM-enriched, with vascular and stromal cells) demonstrating the highest secretion on day 28 (170 ng/mL under high-glucose conditions). In contrast, V1 and V2 (lacking vascular/stromal components and/or dECM) showed significantly reduced β-cell functionality.
 

Conclusion: 3D bioprinted pancreatic organoids composed of α, β, endothelial, and fibroblast cells successfully mimic native islet architecture and function. The use of dECM-enhanced bioinks improves both cell viability and insulin secretion. These findings support the potential of such organoids as platforms for diabetes modeling, drug screening, and future cell-based regenerative therapies.