The effects of LSD1 inhibition on self-renewal and differentiation of human induced pluripotent stem cells.

Human induced pluripotent stem cells (hiPSCs) are capable of unlimited self-renewal and can generate nearly all cells in the body. Changes induced by different LSD1 activities on the regulation of hiPSC self-renewal and differentiation and the mechanism underlying such changes were determined. We used two different LSD1 inhibitors (phenelzine sulfate and tranylcypromine) and RNAi technique to inhibit LSD1 activity, and we obtained hiPSCs showing 71.3%, 53.28%, and 31.33% of the LSD1 activity in normal hiPSCs. The cells still maintained satisfactory self-renewal capacity when LSD1 activity was at 71.3%. The growth rate of hiPSCs decreased and cells differentiated when LSD1 activity was at approximately 53.28%. The hiPSCs were mainly arrested in the G0/G1 phase and simultaneously differentiated into endodermal tissue when LSD1 activity was at 31.33%. Teratoma experiments showed that the downregulation of LSD1 resulted in low teratoma volume. When LSD1 activity was below 50%, pluripotency of hiPSCs was impaired, and the teratomas mainly comprised endodermal and mesodermal tissues. This phenomenon was achieved by regulating the critical balance between histone methylation and demethylation at regulatory regions of several key pluripotent and developmental genes.

Immunogenicity of allogeneic mesenchymal stem cells transplanted via different routes in diabetic rats.

Due to their hypoimmunogenicity and unique immunosuppressive properties, mesenchymal stem cells (MSCs) are considered one of the most promising adult stem cell types for cell therapy. Although many studies have shown that MSCs exert therapeutic effects on several acute and subacute conditions, their long-term effects are not confirmed in chronic diseases. Immunogenicity is a major limitation for cell replacement therapy, and it is not well understood in vivo. We evaluated the immunogenicity of allogeneic MSCs in vivo by transplanting MSCs into normal and diabetic rats via the tail vein or pancreas and found that MSCs exhibited low immunogenicity in normal recipients and even exerted some immunosuppressive effects in diabetic rats during the initial phase. However, during the later stage in the pancreas group, MSCs expressed insulin and MHC II, eliciting a strong immune response in the pancreas. Simultaneously, the peripheral blood mononuclear cells in the recipients in the pancreas group were activated, and alloantibodies developed in vivo. Conversely, in the tail vein group, MSCs remained immunoprivileged and displayed immunosuppressive effects in vivo. These data indicate that different transplanting routes and microenvironments can lead to divergent immunogenicity of MSCs.

The immunoregulation effect of alpha 1-antitrypsin prolong ß-cell survival after transplantation.

Islet transplantation has considerable potential as a cure for diabetes. However, the difficulties that arise from inflammation and the immunological rejection of transplants must be addressed for islet transplantation to be successful. Alpha 1-antitrypsin (AAT) inhibits the damage on ß cells caused by inflammatory reactions and promotes ß-cell survival and proliferation. This protein also induces specific immune tolerance to transplanted ß cells. However, whether the expression of AAT in ß cells themselves could eliminate or decrease immunological rejection of transplants is not clear. Therefore, we established a ß cell line (NIT-hAAT) that stably expresses human AAT. Interestingly, in a cytotoxic T lymphocyte (CTL)-killing assay, we found that hAAT reduced apoptosis and inflammatory cytokine production in NIT-1 cells and regulated the Th1/Th2 cytokine balance in vitro. In vivo transplantation of NIT-hAAT cells into mice with diabetes showed hAAT inhibited immunological rejection for a short period of time and increased the survival of transplanted ß cells. This study demonstrated that hAAT generated remarkable immunoprotective and immunoregulation effects in a model of ß cell islet transplantation for diabetes model.