CCL22-expressing Stem Cell-derived Islet Grafts Recruit Regulatory T Cells in Mice

Cell therapy using human donor or stem cell-derived islets (SC-islets) to replace lost insulin-producing beta (β) cells holds great promise for type 1 diabetes. Recruiting regulatory T cells (Treg) through chemokine signaling could mitigate allo- and autoimmune attack on transplanted β-cells, potentially obviating the need for immunosuppressants. We hypothesized that SC-islets genetically engineered to secrete the chemokine C-C motif chemokine ligand 22 (CCL22) would attract Treg to the site of transplantation and may ultimately prolong graft survival.

We engineered human embryonic stem cells to express CCL22 and differentiated them into SC-islets. CCL22 + SC-islets were assessed for gene and protein markers of endocrine cells and tested for function in vitro by glucose-stimulated insulin secretion assay, and in vivo by transplanting SC-islets into immune-deficient, streptozotocin-treated diabetic mice. Next, CCL22 bioactivity was confirmed by Transwell Treg migration assay. Treg migration was tracked using bioluminescent imaging of mice with CCL22 + SC-islet grafts and infused with luciferase-expressing Treg.

The expression of CCL22 did not adversely impact the differentiation into SC-islets, as confirmed by gene and protein analysis and functional tests in vitro and in vivo. CCL22 + SC-islets induced Treg migration in vitro, with specificity to CCL22 confirmed by a C-C motif chemokine receptor type 4 antagonist. Furthermore, CCL22 + SC-islet grafts recruited human Treg to the transplant site.

CCL22 + SC-islets are functional and capable of attracting Treg. By recruiting Treg, CCL22 + SC-islets may create a tolerogenic immune environment for SC-islets after transplantation.