Introduction: While whole-organ pancreas and islet allotransplantations offer effective alternatives for type 1 diabetes (T1D) treatment, their clinical use is limited by the shortage of human donors. Xenotransplantation is a potential solution to this challenge, with porcine pancreases emerging as an up-and-coming alternative source of islets. While neonatal or juvenile piglets are becoming increasingly favored for obtaining pancreatic islets, no optimal age for clinical application has been established. Debates continue regarding the islet size and function, which are mostly considered immature and are thus referred to as islet cell clusters (ICCs). Aim: This study investigated the ICC size heterogeneity in tissue samples from six juvenile porcine pancreases, all 14 days of age.
Methods: The abundance of ICCs of different sizes (defined as small, intermediate, and large) was assessed in large images of pancreas sections. Automated workflows using NIS Elements software were developed to measure and cluster areas of immunofluorescent-stained beta- and alpha-cells, and to quantify the proportions of insulin- and glucagon-positive regions within the different-sized clusters.
Results: Small, well-developed islets (~100 μm) were consistently identified across all juvenile pancreases, with a density of 6.2 ± 2.5 clusters/mm² (Mean ± S.D.). Homogeneous numbers of intermediate-sized (14.3 ± 4.6 clusters/mm²) and small-sized (72.2 ± 12.6 clusters/mm²) clusters were also observed. Insulin staining predominated in small and intermediate clusters (4-fold higher than glucagon), while large clusters exhibited significantly more glucagon staining, consistent with characteristics of mature islets.
Conclusion: Although further studies are needed to confirm the clinical suitability of juvenile porcine ICCs, our findings suggest that 14-day-old piglets already possess significant amounts of small, mature islets. Optimizing islet isolation techniques, such as gradient centrifugation used in human islet isolation, may enable efficient purification of small and more mature islets from juvenile porcine pancreases for transplantation.