Effect of estrogen on gene expression of fatty acid synthase in periosteum.

BACKGROUND: Estrogen deficiency contributes to postmenopausal osteoporosis. Periosteum might be a potential target of estrogen, but the underlying mechanism at gene level is far from being elucidated. The objective of this study was to investigate the correlation between estrogen and fatty acid synthase (FAS) expression in periosteum. METHODS: Human periosteum cells were cultured in vitro. Expressed genes in the substrated cDNA library were verified using semi-quantitative PCR and real-time PCR. The expression of FAS in periosteum of ovarectomized (OVX) SD rats was investigated. RESULTS: FAS gene was most significantly expressed in the subtracted cDNA library of periosteal cells screened by semi-quantitative PCR. Low FAS expression was verified by real-time PCR in the estrogen exposed human periosteum rather than in the control. The estradiol levels were (20.81 +/- 12.62) pg/ml, (19.64 +/- 4.35) pg/ml and (13.47 +/- 1.84) pg/ml in the sham group, the control, and the OVX group, respectively. The estradiol levels in the OVX group was significantly lower (P = 0.0386). The FAS gene expression in periosteum in the OVX group, sham group, and control group was 3.09 +/- 1.97, 1.33 +/- 0.47 and 1.51 +/- 1.32, respectively. The gene expression in the OVX group was significantly higher (P = 0.0372). CONCLUSION: Estrogen modulates FAS gene expression in in vitro human perisoteum as well as in in vivo rat periosteum.

[Establishment of the transfected cell line expressing the mouse OX40 gene and its potency to induce differentiation of B cells].

AIM: To establish HUVECs line expressing mouse OX40(CD134) and to study its promotive effect on proliferation of B cells. METHODS: The cDNA fragment encoding mouse OX40 was obtained from the total RNA of ConA-activated lymphocytes of thymus by using RT-PCR and cloned into pUCm-T vector. The cDNA was then inserted into the eukaryotic expression vector pIRES2-EGFP. The recombinant vector was transfected into HUVECs with lipofectin reagent, and the positive cellular clones were selected by G418. Expression of mouse OX40 in the transfected cells was analyzed by FCM. The differentiation of B cells in vitro induced by OX40 signal was studied by means of (3)H-TdR method. RESULTS: The cDNA fragment in the recombinant plasmid was consistent with the reported mouse OX40 cDNA in GenBank, which was confirmed by DNA sequencing, PCR and enzyme digestion. The HUVECs stably expressing the mouse OX40 were successfully cloned. The transfected cells promoted the differentiation of B cells in vitro and there existed a synergic effect between OX40/OX40L and CD40/CD40L signals. CONCLUSION: Transfected cell line expressing the mouse OX40 gene is established successfully. OX40 enhances the proliferation of B cells.