Total saponins of Panax ginseng (TSPG) promote erythroid differentiation of human CD34+ cells via EpoR-mediated JAK2/STAT5 signaling pathway

Ethnopharmacological relevanceTotal saponins of Panax ginseng (TSPG), main constituents extracted from Panax ginseng, a highly valued traditional Chinese medicine, have been shown to be an effective agent on hematopoiesis.ObjectiveTo investigate the effect and mechanism underlying in which TSPG promote human CD34+ hematopoietic stem and progenitor cells to differentiate into erythroid-lineage cells.Materials and methodsThe effect of TSPG on erythroid differentiation of purified CD34+ cells derived from umbilical cord blood (UCB) was determined by methylcellulose assay system and colorimetry for hemoglobin content. The changes of EpoR expression in umbilical cord blood mononuclear cells (UCB-MNCs) and purified CD34+ cells were detected with Western blotting and flow cytometry, respectively, and observed under laser scanning confocal microscope (LSCM). RT-PCR was performed to examine EpoR mRNA expression in CD34+ cells. The effects of TSPG-pretreatment on Epo-induced JAK2 and STAT5 tyrosine phosphorylation were analyzed by immunoprecipitation.ResultsThe addition of TSPG (20–70 mg/L) increased the colony formation rate of BFU-E. TSPG (50 mg/L) alone used significantly increased the hemoglobin content, the addition of AG490 evidently reduced TSPG-induced elevation of hemoglobin content. TSPG increased the expression of EpoR on the surface membrane of CD34+ cells but did not change the expression of EpoR in total UCB-MNCs. TSPG also increased the expression of EpoR mRNA in CD34+ cells. TSPG markedly enhanced Epo-induced tyrosine phosphorylation of JAK2 and STAT5 in UCB-MNCs.ConclusionThese findings suggest that TSPG may enhance the erythroid differentiation of hematopoietic stem and progenitor cells via Epo/EpoR-mediated JAK2/STAT5 signaling pathway.