Total saponins of Panax ginseng (TSPG) promote erythroid differentiation of human CD34 + cells via EpoR-mediated JAK 2/STAT 5 signaling pathway

Abstract

Ethnopharmacological relevance Total 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. Objective To 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 methods The 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 JAK 2 and STAT 5 tyrosine phosphorylation were analyzed by immunoprecipitation. Results The 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 JAK 2 and STAT 5 in UCB-MNCs. Conclusion These findings suggest that TSPG may enhance the erythroid differentiation of hematopoietic stem and progenitor cells via Epo/EpoR-mediated JAK 2/STAT 5 signaling pathway.