Immunological Characterization of Human Umbilical Cord Lining Derived Cells and their Therapeutic Application in a Diabetic Mouse Model

This study describes the immunological characterization of a novel primary epithelial cell-type from the human umbilical cord. Two types of cells can be derived from the umbilical cord lining membrane, termed cord lining epithelial cells (CLECs) and cord lining mesenchymal cells (CLMCs). Preliminary immunophenotyping showed that CLECs but not CLMCs express significant levels of HLA-G isoforms and HLA-E, two MHC-Ib molecules with immunosuppressive functions which mediate immune tolerance during pregnancy. Further detailed immunological analysis using in vitro/ex vivo assays (including mixed leukocyte reactions) showed that CLECs inhibit human allogeneic and mitogen stimulated T-lymphocyte responses with a concomitant reduction in pro-inflammatory cytokines. Using a transwell co-culture system, it was demonstrated that these immunoregulatory effects were mediated by soluble factors secreted by CLECs, in a dose-dependent manner. HLA-G functional studies showed that the effects of CLEC secreted products could be inhibited by an HLA-G blocking antibody, thus demonstrating a significant and important role for soluble HLA-G. However, this immunoregulation by CLECs did not involve induction of T cell apoptosis or expansion of regulatory T cells. In in vivo studies in immunocompetent mice, transplanted CLECs could be maintained for extended periods while acute xeno-rejection rapidly destroyed primary keratinocytes, a control human epithelial cell type. Viable CLECs could be retrieved from the subcutaneous transplant site two weeks after original transplantation and re-cultured. Additionally, CLECs delayed the rejection of keratinocytes and extended their survival when co-transplanted, indicating an ability to protect adjacent human cell types that would otherwise be rejected if transplanted alone. In a preliminary study of ex vivo gene therapy, CLECs transduced with a modified human proinsulin gene were transplanted intra-peritoneally into streptozotocin (STZ) induced diabetic mice, resulting in significantly lower levels of serum glucose compared to control mice. This is the first detailed study in which the immunological properties of CLECs have been comprehensively investigated and a potential therapeutic application for CLECs has been tested in the treatment of a type 1 diabetes mouse model.

Author dc:creator

• ZHOU YUE

• Umbilical cord lining cell, HLA-G, immune regulation, tolerance, cell transplantation