Introduction: β-cell replacement is an attractive treatment for type-1-diabetes (T1D), but toxic immunosuppressive drugs are needed. We aimed to deliver allogeneic β-cell therapies without anti‐rejection drugs using a bioengineered device that combines microencapsulation of β-cells and 3D scaffolds printed using melt-electrospin-writing (MEW).
Methods: Mouse β-cell (MIN6) clusters, islets from QS mice and human islet-like clusters (ILC) differentiated for 28 days from embryonic stem cells (hESC) were encapsulated in 2.2% ultra-pure alginate. Viability and glucose stimulated insulin secretion were assessed. Cells were encapsulated and seeded within MEW scaffolds. Devices were transplanted subcutaneously in immune-deficient (NOD⁄SCID) or immune-competent (BALB/c) mice made diabetic with low-dose streptozotocin (n=6-8⁄group). Blood glucose level (BGL) and glucose tolerance were tested. Vascularity inside grafts was quantified over 4 weeks by 3D-doppler ultrasound. Once BGL normalized, grafts were removed for examination. Insulin and C-peptide in plasma, pancreata and grafts were measured by ELISA.
Results: Cell viability and insulin secretion were unaffected by encapsulation. Transplantation of encapsulated MIN6 within MEW scaffolds lowered BGL (from 30 ± 3 to 5 ± 2mmol⁄L) and improved glucose tolerance in diabetic NOD⁄SCID and BALB⁄c strains within 25-41 days. Long-term BGL normalization (60-100 days) in BALB⁄c mice was achieved with QS islets in a device pre-vascularised for 3 weeks. Inflammatory infiltration of neutrophils (myeloperoxidase+), macrophages (CD68+) and B-lymphocytes (CD19+) were present on MEW scaffolds but not on microcapsules, which had infrequent pro-fibrotic walling (α-SMA+). In diabetic NOD⁄SCID mice receiving 2000 ILC, human C-peptide was measurable and no teratoma was detected for at least 83 days. BGL were lowered to almost normal in NOD⁄SCID mice receiving encapsulated ILC intraperitoneally, with C-peptide levels being > in recipients of subcutaneous grafts.
Conclusion: Allogeneic β-cell therapy for T1D without immunosuppression can be delivered using our bioengineered device. It is safe to implant β-cells differentiated from hESC.