In: Progesterone1 Feb 2013
Prior to implantation of the mammalian embryo, a sequence of changes takes place in the endometrium in response to the female sex steroids estrogen and progesterone. Ovarian hormone action on uterine cells is necessary in order to change the uterus from a suboptimal environment to one that is receptive to the blastocyst. The best-characterized action of estrogen and progesterone on the mammalian uterus is stimulation of endometrial cell proliferation and differentiation. While it is clear that hormonal control of proliferation is mediated, in part, through control of the expression of a variety of growth factors and/or growth factor receptors, recent evidence from breast cancer cell studies elegantly shows direct control of cell cycle regulatory proteins by steroid hormones.
Studies concerned with understanding the targets of hormone action thus continue to center on the identification of endocrine-dependent genes that regulate uterine cell proliferation and differentiation. Estrogen and progesterone act on target tissues, such as the uterus, by stimulating the transcription of certain genes. Ligand-bound receptors interact with specific hormone response elements along the DNA of target genes and change the rates of transcription. While this mechanism of hormone action has been clearly demonstrated for a variety of individual genes, the potential targets of hormone action required to stimulate endometrial cell proliferation and differentiation are not clearly defined. buy asthma inhaler
The purpose of this review is to summarize the current information regarding the effects of progesterone, the hormone of pregnancy, on control of stromal cell proliferation in the uterus. We focus particularly on the rodent models, since the pattern of cell proliferation in these species has been extensively characterized (see ). Our understanding of cell cycle control in hormonally responsive cells, particularly uterine cells, lags behind knowledge of other systems because few models have been available for study of the role of steroid hormones and their receptors in this process. The development of stromal cell culture systems in which progesterone-dependent proliferation is maintained provides an important opportunity for new insight into the molecular mechanisms regulating stromal cell proliferation. Formation and regression of the decidua are critical events to ensure successful pregnancy in many euther-ian mammals. By understanding hormonal control of cell proliferation, we can best address its cessation for differentiation (stromal cell decidualization) and later regression (apoptosis).
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