Abstract:

Objective   To investigate effects of Wharton′s jelly-derived mesenchymal stem cells(WJCs) from the human umbilical cord on CD4+CD25+ regulatory T cells and the Foxp3 gene, and their immunoregulatory mechanisms in severe aplastic anemia(SAA) patients. Methods   WJCs were isolated from the human umbilical cord, expanded, and identified by morphology of culture cells and flow cytometry of stem cell markers. Using density gradient centrifugation, T-lymphocytes(TLCs) were isolated from human peripheral blood from patients with SAA. TLCs(1×105) were cultured under the stimulation of phytohemagglutinin(PHA). In the experimental group, WJCs(1×103,1×104 and 1×105)were co-cultured with TLCs for 3 days, and then the inhibitory ratio of TLCs induced by human WJCs at various concentrations was measured by MTT assay. The percentage of CD4+CD25+T cells from patients with SAA was detected by flow cytometry, and expression of the Foxp3 gene was detected by reverse transcriptionpolymerase chain reaction(RT-PCR). Results   WJCs showed an inhibitory effect on TLCs from patients with SAA in a dose-dependent manner. An increase of the percentage of CD4+CD25+T cells in peripheral CD4+T cells was  observed  when  TLCswere co-cultured with WJCs. The level of Foxp3 mRNA in the experimental group was significantly higher than that in the controls and was negatively associated with the value, which represented TLCs proliferation. Conclusion   WJCs specifically inhibit the proliferation of TLCs from patients with SAA in a dose-dependent manner, and one of mechanisms could be that up-regulated expression of Foxp3 promotes CD4+CD25+regulatory T cells to perform their immunoregulatory function.

Key words: Wharton′s jelly-derived mesenchymal stem cells; CD4+CD25+regulatory T cells; Foxp3 gene; Aplastic