OBJECTIVETo investigate the effect of human umbilical cord-derived mesenchymal stem cells(HUC-MSC) on the proliferation and differentiation of NB4 treated with all-trans retinoid acid (ATRA) and its underlining mechanisms .

METHODSHuman umbilical cord mesenchymal stem cells were isolated from umbilical cord of newborns. Co-culture system was established by HUC-MSC and NB4 in vitro. The experiment was divided into 4 groups: NB4 group (NB4 cells alone) , NM group (NB4 cells co-cultured with HUC-MSC) , NA group (NB4 cells treated with ATRA) , NMA group (NB4 cells co-cultured with HUC-MSC and treated with ATRA) . NB4 cells were counted by a microscopy, NB4 proliferation was monitored by CCK-8 assay, NB4 differentiation was assessed by Wright ' s staining and nitroblue tetrazolium reduction test. IL-6 levels in the culture supernatant of different groups were tested by ELISA kit. Quantitative PCR was used to detect the transcription level of CDKN1A, CCND1 and Survivin.

RESULTSNB4 and HUC-MSC in the co-culturing systems were in good condition with a slight repression of NB4 proliferation by HUC-MSC. HUC-MSC could collaborate with ATRA to induce significant NB4 differentiation. Consistent with this finding, IL-6 expression levels of co-cultured groups were remarkably higher than that in any other groups or the group of HUC-MSC alone. The quantitative PCR analysis showed that the levels of CDKN1A and CCND1 mRNA expression were increased or decreased respectively in the co-cultured groups.

CONCLUSIONHUC-MSC co-culture can reduce proliferation but promote the differentiation of NB4 cells, suggesting that this effect may be closely related with the secretion of IL-6 which can affect the expression of some factors in vitro.