Expression of Pdx-1 in bone marrow mesenchymal stem cells promotes differentiation of islet-like cells in vitro.

Bone marrow mesenchymal stem cells (BMSCs) have the ability of self-renewal and multi-directional differentiation. Recent reports showed that BMSCs could differentiate into endocrine cells of pancreas. However, the differentiation is not efficient enough to produce insulin-producing cells for the future therapeutic use. Pdx-1 is a crucial regulator for pancreatic development. Therefore we constructed a eukaryotic expression vector containing Pdx-1 to determine the effect of Pdx-1 expression on differentiation of BMSCs in vitro. The results showed that BMSCs could self-assemble to form functional pancreatic islet-like structures after differentiation in vitro. The proportion of insulin-producing cells differentiated from Pdx-1+BMSCs was 28.23% +/- 2.56%, higher than that from BMSCs transfected with vacant vector and Pdx-1-BMSCs (7.23% +/- 1.56% and 4.08% +/- 2.69% respectively) by flow cytometry. Immunocytochemical examination also testified the expression of multiple beta-cells-specific genes such as insulin, glucagons, somatostatin in differentiated BMSCs. The results also revealed that the expressions of genes mentioned above in Pdx-1+BMSCs were higher than that in Pdx-1-BMSCs, which was confirmed by Western blotting analysis and RT-PCR. Glucose-induced insulin secretion from Pdx-1+BMSCs in 5 mmol/L and 25 mmol/L glocuse was (56.61 +/- 4.82) microU/mL and (115.29 +/- 2.56) microU/mL respectively, which were much higher than those from Pdx-1-BMSCs ((25.53 +/- 6.49) microU/mL and (53.26 +/- 7.56) microU/mL respectively). Grafted animals were able to maintain their body weight and survive for relatively longer periods of time than hyperglycemic sham-grafted controls, which demonstrated an overall beneficial effect of the grafted cells on the health of the animals. These findings thus suggested that exogenous expression of Pdx-1 should provide a promising approach for efficiently producing islet-like cells from BMSCs for the future therapeutic use in diabetic patients.