Introduction: Islet transplantation can restore glycemic homeostasis in a subset of patients with type 1 diabetes but is limited by a shortage of human donors and the need for multiple donors per recipient. Neonatal porcine islets (NPIs) are a promising alternative, providing a scalable, reproducible source of islets from genetically modified pigs. Porcine pancreases could be transported to Good Manufacturing Practice (GMP) facilities specialized for NPI isolation. Static cold storage with University of Wisconsin (UW) solution is the standard for pancreas preservation, supporting viability for up to 12-hours. Extending this duration to 24-hours could expand xenotransplantation applications by allowing longer transport times. This study examines the impact of 24-hour cold storage of neonatal porcine pancreases (2-5 days old) in UW solution on islet recovery and NPI function.
Methods: Pancreases from both male and female neonatal piglets (n = 16 / treatment) were either digested immediately post-surgery (fresh) or stored in UW at 4°C for 24-hours before islet isolation. After a week of culture, islets were assessed for glucose-stimulated insulin secretion (GSIS), DNA content, insulin content, and morphology. Functionality was further tested by transplanting 3000 NPIs under the kidney capsule of male and female streptozotocin-induced diabetic B6.129S7-Rag^1tm1Mom/J mice (Fresh: n = 24; UW: n = 25) post-culture. Data expressed as mean ± SEM.
Results: Cell recovery based on total DNA content per pancreas was similar in both groups (Fresh: 90.50 ± 10.28 μg vs. UW: 82.45 ± 6.02 μg; p = ns). In contrast, the total cellular insulin content per pancreas was significantly higher in the fresh group (8.82 ± 1.29 μg vs. UW: 3.84 ± 0.49 μg; p < 0.01). The proportion of β-cells (Fresh: 22.08 ± 1.76% vs. UW: 16.41 ± 1.26%; p < 0.05), and calculated β-cell recovery was significantly lower in UW (Fresh: 2.60×10⁶ ± 0.23 vs. UW: 1.85×10⁶ ± 0.15; p < 0.05). The in vitro glucose-stimulated insulin secretion, remained consistent, with similar percent insulin release at low (Fresh: 0.049 ± 0.006% vs. UW: 0.053 ± 0.007%; p = ns) and high glucose concentrations (Fresh: 0.098 ± 0.014% vs. UW: 0.111 ± 0.015%; p = ns). Stimulation indices were comparable, at 2.00 ± 0.18 and 2.12 ± 0.08 (p = ns) in the fresh and UW groups respectively. The reversal rates of diabetes in the transplanted mice were comparable between fresh and UW, suggesting that UW treatment does not impair in vivo function.
Conclusions: 24-hour hypothermic storage of neonatal pig pancreases in UW solution did not impair NPI recovery. In vitro and in vivo function was not impaired despite significantly lower insulin content, β-cell composition and number. This supports the feasibility of transporting porcine pancreases to expand xenogeneic donor islet availability.