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 report cases of multiple mitochondrial dysfunction syndrome 2 (MMDS2) caused by BOLA3 gene mutation, hoping to help clinical diagnosis. Methods:The medical records of a child with MMDS2 admitted to the Department of Neurology, Guangzhou Women and Children′s Medical Center in November 2021 were analyzed, and the clinical, imaging characteristics and prognosis of MMDS2 were summarized by literature review.Results:This 1 year and 9 months old male had a disease that started in childhood, with motor function regression and hyperlactatemia. Head magnetic resonance imaging indicated white matter lesions, and gene examination indicated the homozygous variation of BOLA3 gene c.295C>T(p.Arg99Trp). The diagnosis of MMDS2 was clear for the child. After treatment, the clinical symptoms and imaging of the child recovered significantly. Through literature review, 13 children with MMDS2 reported in 7 English literatures were reviewed. These cases had similar manifestations with the case reported in this study. Among them, 1 case recovered and 8 cases died in infancy. Conclusions:MMDS2 patients often show nervous system dysfunction such as motor regression, elevated lactate and white matter lesions, which often cause multiple system disorders. Some children die early, but some of them can be recovered.