CONICET | Buscador de Institutos y Recursos Humanos

Leptin, the 16 kDa protein product of the obese gene, was originally seen as an adipocyte-derived signaling molecule, but later found to be expressed in other tissues particularly in placenta. It has been suggested to be involved in some functions during pregnacy such as growth, angiogenesis and immunomodulation. The molecular mechanisms involved in the adhesion of the embryos to uterine epithelium and growth are still unknown. The aim of the present investgation is to study the factors that could regulate leptin expression in placental cells and leptin involvement in cell proliferation. Methods: JEG-3 and BeWo cells were cultured under standard conditions. Western blot analysis was carried out to detect leptin and leptin receptor proteins.Leptin promoter activity was evaluated by transient transfection with a plasmid containing different promoter regions directing the expression of the reporter gene luc. Cell proliferation was asessed by cell counting, 3H-timidine incorporation and FACS analysis. Apoptosis was determined by caspase 3 activation and Annexin V-FITC staining method. Results: We observed a maximum increase in promoter activity of 8.8 and 12.9 times when cells were treated with 0.1 mM 17b-estradiol and 100 UI of hCG/ml, respectively. These effects were dose dependent and not evidenced with a promoter length of less than -1.9 Kb. Similar results were obtained when studying endogenous leptin expression. On the other hand leptin treatment promoted cell proliferation in a time and dose dependent way, with a maximum of 2.9 times at 250 ng/ml in day 3, probably by increasing cells in G2 phase. Diminished endogenous leptin level by treatment with an antisense oligonucleotide (2 mM) reduced 3.25 times cell proliferation and increased cell apoptosis. Conclusions: All these findings put leptin as a possible link between embryo and endometrium communication. Supported by a grant from Universidad de Buenos Aires (UBACYT X-048).

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