Exosome loaded immunomodulatory biomaterials alleviate local immune response in immunocompetent diabetic mice post islet xenotransplantation

摘要

a Non-fasting blood glucose levels in C57/BL6 STZ-induced diabetic mice (n = 5 mice) shows that transplantation of 1500 IEQ rat islets within AlgXO provided euglycemia in diabetic mice for >170 days, whereas the CTRL microcapsules failed in <1 month. To further confirm that the glycemic correction is merely due to transplants and not pancreatic regeneration in STZ-induced diabetic mice, we washed the i.p. cavity of mice and removed the explants after 105 days of transplantation (n = 2 mice). Within 18 h of graft removal, mice blood glucose elevated and remained hyperglycemic for the rest of their lifetime (dashed green line). Separate i.p. transplantation of islets within CTRL microcapsules and XOs provided normoglycemia for ~70 days (black line, n = 4 mice). b We further tested the efficacy of AlgXO transplants in response to oral glucose tolerance test (OGTT). One month after transplantation, similar to STZ mice (n = 6 mice), CTRL microcapsules failed to regulate the glucose levels (n = 4 mice), whereas AlgXO transplants successfully reversed hyperglycemia event induced by glucose challenge (n = 6 mice), with similar trend as non-diabetic controls. c The average time to reach normoglycemia after an OGTT for non-diabetic mice was 65 ± 27 min and for mice with AlgXO transplants was 103 ± 32 min (n = 6 mice). d After 1 month, both CTRL and AlgXO (from 1500 IEQ group) transplants were removed through washing the i.p. cavity. Next, microcapsules were analyzed for the immune infiltration (also known as pericapsular cell growth) with laser-scanning confocal microscopy. Some cells were CD11b+ and some of the CD11b+ cells were expressing MHCII biomarker. All the collected CTRL microcapsules were found to have pericapsular cells attached to the surface, while the percentage of AlgXO transplants with pericapsular growth was 9.4% ± 3.6%, which was significantly lower than CTRL transplants (p < 0.0001). Scale bars are 200 μm for the dark field and 100 μm for the florescent channels. e The pericapsular cytokine and chemokines present released in the pericapsular area of implants. Results are mean ± SD, and statistical significance is calculated through unpaired t-test with Welch’s correction. 1: STZ injection; 2: Diabetes induction period; 3: Transplantation; 4: Graft removal.