Biomedical subjects

C M Serre

Publications and source records attributed to C M Serre.

22 records · Page 2Linked to original sources

PubMed1992

Protein-S, a vitamin K-dependent protein, is a bone matrix component synthesized and secreted by osteoblasts.

Protein-S is a vitamin K (Vit K)-dependent protein synthesized by hepatocytes, megakaryocytes, and endothelial cells and plays an important role in the regulation of hemostasis. Two cases of free protein-S congenital deficiency were recently reported to be associated with osteopenia. We hypothesized that this osteopenia could be the result of a bone deficit of protein-S synthesized by bone cells. Using enzyme-linked immunoassay, immunocytochemistry, immunoblotting, and immunoprecipitation after labeling with [35S]methionine, we have shown that this protein is secreted by three human osteosarcoma cell lines and by human adult osteoblast-like cells. In addition, protein-S was present in protein extracts of human bone matrix. Protein-S secreted by MG 63 cells increased linearly from 1-7 days of culture, was biologically active, and was regulated by warfarin, as previously described for the other cell types secreting protein-S. Vit K had no direct effect on protein-S secretion or activity, but could overcome the effects of warfarin. In conclusion, in addition to osteocalcin and matrix gamma-carboxyglutamic acid (Gla) protein, osteoblasts secrete another Vit K-dependent protein, which is a constituent of the bone matrix. Our data suggest that osteopenia occurring in patients with congenital protein-S deficiency might be related to a deficiency of protein-S secretion by the osteoblasts. This finding raises the intriguing possibility that protein-S might play a role in bone turnover and bone mass.

Bone Neoplasms↗

PubMed1991

Thrombospondin binds to the surface of human osteosarcoma cells and mediates platelet-osteosarcoma cell interaction.

We have previously shown that thrombospondin (TSP) is synthesized and secreted by human MG-63 osteosarcoma cells. In this study, the secretion and cell surface expression of TSP by two different human osteosarcoma cell lines (MG-63 and TE-85) as well as the involvement of TSP in the platelet-aggregating activity of these tumor cells were studied. Using a sandwich enzyme-linked immunosorbent assay, MG-63 cells secreted 3-fold as much TSP as TE-85 cells at 48 h (0.17 +/- 0.01 (SD) versus 0.06 +/- 0.006 micrograms/10(6) cells, P = 0.007). Binding of exogenous 125I-TSP to MG-63 and TE-85 cells in monolayer indicated that binding was time and concentration dependent, saturable, and inhibited by excess cold TSP. However, despite a similar affinity, MG-63 cells had 10-fold more TSP-binding sites than TE-85 cells (402,394 +/- 130,346 versus 36,748 +/- 7,708 TSP-binding sites/cell; P = 0.002). Similar binding differences of 125I-TSP were observed with both osteosarcoma cell lines in suspension. A fluorescence-activated cell-sorting analysis was used in conjunction with an anti-TSP polyclonal antibody, and binding of endogenous TSP to MG-63 and TE-85 cells in suspension was investigated. Addition of an anti-TSP antibody to MG-63 and TE-85 cells in suspension increased the mean fluorescence intensity 50-fold when compared to an irrelevant antibody. Moreover, the fluorescence intensity of MG-63 cells with an anti-TSP polyclonal antibody was increased by 40% when compared to TE-85 cells. Since TSP was expressed on the surface of osteosarcoma cells, the involvement of this glycoprotein in the platelet-aggregating activity of MG-63 and TE-85 cells was therefore investigated using an anti-TSP polyclonal antibody and two monoclonal antibodies (P10 and MA-II), the epitopes of which lie within the Mr 140,000 non-heparin-binding fragment and the Mr 25,000 heparin-binding fragment of TSP, respectively. Preincubation of MG-63 cells (1 x 10(6) cells/ml) with either an anti-TSP polyclonal antibody (100 micrograms/ml) or monoclonal antibody P10 (15 micrograms/ml) inhibited by 80% other platelet-aggregating activity of these tumor cells, while anti-TSP monoclonal antibody MA-II (15 micrograms/ml) had no effect. In sharp contrast, the anti-TSP polyclonal antibody (100 micrograms/ml) only exhibited a slight inhibitory effect on platelet aggregation induced by TE-85 cells when using a low concentration of tumor cells (0.6 x 10(6) cells/ml).(ABSTRACT TRUNCATED AT 400 WORDS)

Antibodies↗

PubMed1990

[Effects of 1,25 dihydroxyvitamin d3 on the morphology and alkaline phosphatase activity of ROS 17/2,8 osteoblastic cells: influence of time and dose].

Osteosarcoma-derived osteoblastic cells were exposed to 1,25 dihydroxyvitamin D3 (1,25(OH)2D3) either to 0.001-1,000 nmol.l-1 for 4 days or to 10 nmol.-1 for 1-21 days. Between 0.01 and 10 nmol.l-1, a dose-dependent increase in alkaline phosphatase (AP) activity was found, which rose to a maximum level at 10 nmol.l-1 (+55%). At higher doses (100 and 1,000 nmol.l-1), 1,25(OH)2D3 induced a decrease in AP activity of 40%. After 1 day at 10 nmol.l-1 a slight increase in AP activity was noted (+20%) which augmented with the duration of exposure. This stimulatory effect was highest after 8 days (+130%). In contrast, after 15 and 21 days, AP activity decreased by 30%. Under 1,25(OH)2D3, microtubules were observed mainly in the perinuclear region.

Alkaline Phosphatase↗

PubMedDate not supplied

Fluoride increases rat osteoblast function and population after in vivo administration but not after in vitro exposure.

The effects of fluoride on bone tissue are now well documented by in vivo histological studies performed on both human and animal bone biopsies and demonstrating an increase in osteoblast (OB) population. In order to elucidate whether the mechanism of action of fluoride on osteoblasts was direct or indirect, 14 three-week-old Sprague-Dawley rats were selected. Seven animals received 100 ppm fluoride as sodium fluoride (NaF) in drinking water for one month. The other animals, which did not receive fluoride, were considered as controls. At the end of the experiment, femurs and vertebrae were excised and osteoblastic cells were obtained after collagenase digestion separately from each animal. The osteoblastic cells derived from control and NaF-treated rats were exposed in vitro to 10(-5) M NaF. Alkaline phosphatase (AP) activity was measured, and the cellular proliferation was assessed by 3H-thymidine incorporation. Thymidine incorporation and AP activity were significantly higher in osteoblastic cells derived from NaF-treated rats than in cells obtained from control rats (p = 0.05 and p < 0.01, respectively). In contrast, the osteoblast proliferation and activity were not modified after in vitro exposure to NaF in cells derived from control and NaF-treated rats. In conclusion, the function of osteoblasts was not modified after in vitro exposure to fluoride. In contrast, given in vivo to rats for one month, fluoride has a mitogenic effect on osteoblasts and stimulates their activity. These data emphasize the hypothesis that fluoride may act either on osteoprogenitor cells or through an indirect mechanism mediated by a cofactor.

Administration, Oral↗