Abstract：Objective To analyze the stem cell characteristics of CD34+ epidermal cells and their resistance to acute cytotoxicity of sodium arsenite (NaAsO2) so as to lay the foundation for further exploring the arsenic carcinogenic mechanism by using stem cells model. Methods CD34+ cells were enriched from HaCaT cells by immunomagnetic separation method and verified by flow cytometry. Holoclone forming capacity was assessed. The mRNA levels of genes encoding stem cell markers (CD34, p63, K5, K14, OCT4 and SHH), drug transporters (ABCC1, ABCC2 and ABCG2), detoxification enzyme gene (GST-Pi) and antioxidant genes(NRF2, HO-1 and GCLC) were measured by reverse transcript quantitative PCR (RT-qPCR). CD34+ cells and HaCaT cells (control cells) were treated with 0-150 μmol/L NaAsO2 for 24 hours, and then cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)- 5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay. Results After immunomagnetic separation, the enrichment rate of CD34+ cells was increased from (0.10±0.05)% to (88.6±2.5)% (P<0.001). Holoclone formation capacity of CD34+ cells was 2.4 fold of that of the control cells (P<0.01). The transcriptional levels ofgenes encodingstem cell markers, CD34, p63, K5, K14, OCT4 and SHH, were significantly increased in CD34+ cells (P<0.05), which were (18.20±2.81) fold, (2.21±0.07) fold, (1.60±0.13) fold, (3.89±0.05) fold, (2.27±1.34) fold and (4.18±0.91) fold of those in the control cells. Viability of CD34+ cells in response to NaAsO2 at 20-150 μmol/L was significantly higher than that of the control cells (P<0.05). The median lethal doses (LD50) of CD34+ cells and the control cells in response to NaAsO2 were 98.3 μmol/L and 50.1 μmol/L respectively. The mRNA levels of drug transporter genes (ABCC1, ABCC2 and ABCG2) in CD34+ cells were significantly higher than those of the control cells (P<0.05), which were (3.00±0.30) fold, (1.23±0.30) fold and (2.59±0.38) fold of those in the control cells. The mRNA level of detoxification enzyme gene (GST-Pi) was (2.19±0.56) fold of thatin the control cells, and the transcriptional levels of antioxidant genes (NRF2, HO-1 and GCLC) in CD34+ cells were significantly higher than those of the control cells (P<0.05), which were respectively (2.22±0.23) fold, (2.59±0.36) fold and (2.19±0.24) fold of those in the control cells. Conclusions CD34+ cells from HaCaT cells show stem-cell-like phenotypes and hyper-resistance to acute arsenic exposure.
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