BACKGROUND:Notch singling pathway is very important for cellproliferation and differentiation, but its role is stil unknown during chondrogenesis of human umbilical cord mesenchymal stem cells. OBJECTIVE:To investigate the effect of N-[N-(3,5-difluorophenacetyl-L-alanyl)]-(S)-phenylglycinet-butyl ester (DAPT) on inducing human umbilical cord mesenchymal stem celldifferentiation into chondrocytes. METHODS:Human umbilical cord mesenchymal stem cells were isolated from human umbilical cord, then were induced to differentiate into chondrocytes. There were four experimental groups:non-induced group, high-glucose Dulbecco’s modified Eagle’s medium containing 5%fetal bovine serum and 1%double antibody;induced group, induced medium containing 6.25 mg/L insulin, 6.25 mg/L transferrin, 10μg/L transforming growth factor beta 1, 0.1μmol/L dexamethasone, 50 mg/L vitamin C, 5%fetal bovine serum and 1%double antibody;dimethyl sulfoxide group, induced medium containing 0.1%dimethyl sulfoxide;DAPT group, induced medium containing 5μmol/L DAPT. RESULTS AND CONCLUSION:After chondrogenic induction, the morphology of human umbilical cord mesenchymal stem cells became polygon and positive for toluidine blue and immunofluorescence staining;the expression of Jag-1, PS-1, Notch-1 and Hes-1 decreased significantly (P<0.01). After the addition of DAPT, compared with the induced group, the relative gene expression of Jag-1, PS-1 and Hes-1 decreased markedly (P<0.01), the relative gene expression of Notch-1 decreased obviously as wel (P<0.05), and the contents of proteoglycan and col agen type II proteins decreased significantly (P<0.01). At the same time, the relative gene expression of proteoglycan decreased obviously (P<0.05), and the relative gene expression of col agen type II decreased in part. Notch signaling pathway exists in human umbilical cord mesenchymal stem cells, once chondrogenesis begins, the signaling strength wil decline rapidly. DAPT may prevent human umbilical cord mesenchymal stem cells from differentiating into chondrocytes by Jag-1-Notch-1-Hes-1 pathway.

OBJECTIVE: To retrospectively analyze non-invasive prenatal screening (NIPS) data from two centers. METHODS: The NIPS results of 10 840 samples were analyzed, including 21/18/13 trisomies (T21/T18/T13), sex chromosome and other autosomal aneuploidies, and copy number variants (CNVs). The maternal age, gestational week, body mass index and concentration of free fetal DNA (cffDNA) were also analyzed. RESULTS: The average gestational age of the 10 840 pregnant women was (32.34±5.04) year old, and the average gestational week for NIPS was (17.60±3.55) week. The overall false positive rate for T21/T18/T13 was 0.11%, sensitivity was 100%, specificity was 99.89%, and positive predictive value was 81.5%. The positive predictive values for sex chromosome and other autosomal aneuploidies and CNVs were 56.67%, 11.76% and 83.33%, respectively. The incidence of T21/T18 in the elder women (35 years or elder) was 2.12 times(P<0.01) and 1.81 times (P> 0.05) that of young women. cffDNA was in proportion to gestational week (r = 0.207) and in inverse proportion to body mass index (r = -0.177). It has increased slowly before 15 weeks of gestation and thereafter at a rate of 0.5% per week after the 16th week. CONCLUSION The performance of NIPS in this study is by large close to the reported in the literature, and the results can provide a reference for further study.