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


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.


CONCLUSIONS
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.
Chen
D
D
Laboratory of Stem Cell and Tissue Engineering, Department of Histology and Embryology, Chongqing Medical University, Chongqing, China.
Zuo
G
G
Li
C
C
Hu
X
X
Guan
T
T
Jiang
R
R
Li
J
J
Lin
X
X
Li
F
F
Luo
C
C
Wang
H
H
Lei
C
C
Long
X
X
Wang
Y
Y
Wang
J
J
D018952:Antigens, CD34; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015672:Erythroid Precursor Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005312:Fetal Blood; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D053614:Janus Kinase 2 / Q000378:metabolism*; D007963:Leukocytes, Mononuclear / Q000187:drug effects; D005894:Panax / Q000737:chemistry*; D010766:Phosphorylation; D010936:Plant Extracts / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D017467:Receptors, Erythropoietin / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050799:STAT5 Transcription Factor / Q000378:metabolism*; D012503:Saponins / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D014443:Tyrosine; D020032:Tyrphostins / Q000494:pharmacology
D018952:Antigens, CD34; D004791:Enzyme Inhibitors; D006454:Hemoglobins; D010936:Plant Extracts; D012333:RNA, Messenger; D017467:Receptors, Erythropoietin; D050799:STAT5 Transcription Factor; D012503:Saponins; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; D014443:Tyrosine; D053614:Janus Kinase 2