Arachidonic acid in uterine phospholipid during early pregnancy and following hormone treatment

Regulation of cytosolic phospholipase A2 in rat endometrial stromal cells: the role of epidermal growth factor

The effect of epidermal growth factor on the levels of cytosolic phospholipase A2 mRNA and protein in cultured rat endometrial stromal cells isolated from uteri sensitized for the decidual cell reaction was examined. Treatment with epidermal growth factor increased the steady-state cytosolic phospholipase A2 mRNA and protein levels as demonstrated by Northern and Western blot analyses, respectively. Immunocytochemical analysis demonstrated an increase of cytosolic phospholipase A2 protein in most cells, as opposed to a small subpopulation of cells in culture. These results show that epidermal growth factor causes an increase in steady-state cytosolic phospholipase A2 mRNA and protein levels in rat endometrial stromal cells from uteri sensitized for the decidual cell reaction. Epidermal growth factor receptor ligands may regulate cytosolic phospholipase A2 and thus prostaglandin production in the endometrial stromal cells during implantation.

Uterine lipid alterations during early pseudopregnancy and following the artificial induction of decidualization by Concanavalin A in QS mice

Lipid extracts of whole uterine tissue from mice were examined by gas chromatography-mass spectrometry during days 2,3, and 4 pseudopregnancy (day 1 = copulatory plug) and following the artificial induction of the decidual cell reaction (DCR) on day 4. The range of lipids identified during pseudopregnancy and their percentage composition on day 2 included saturated fatty acids (SFA, 38%), monounsaturated fatty acids (MUFA, 20%), polyunsaturated fatty acids (PUFA, 17%), sterols (25%), long chain alcohols (0.12%), and alkylglycerols (0.11%). Of these, the main components were the fatty acids 16:0 (21%), 18:0 (14%), cis18:In-9 (14%), 18:2n-6 (8.5%), and cholesterol (24%). Although only subtle changes in the composition of uterine lipids occurred through days 2 and 3 of pseudopregnancy, more substantial changes were detected on day 4, at a time when the uterus normally initiates its transient "window of receptivity." Following induction of the DCR with the lectin Concanavalin A (Con A) at this time, even greater alterations in uterine lipid composition were observed. From 20 to 1,280 min post-Con A-treatment the percentage composition of SFA in the treated left uterine horn changed from 43% to 64%, sterols from 19% to 4%, PUFA from 15% to 10%, while MUFA remained unchanged at 23%. The lipid profile of the untreated right uterine horn of these animals was similar to that of the Con A-treated left uterine horn during the early stages. However, by 1,280 min substantial differences were observed, at a time corresponding with Con A-induced uterine growth. In contrast, differences in the lipid profile of Con A- and saline-treated uteri were observed at 320 min post-treatment, a time preceding Con A-induced uterine growth. Furthermore, the tissue concentration (nmol/mg dry weight) of SFA and sterols in uterine tissue decreased significantly following Con A treatment. The results suggest that uterine lipid changes are implicated in the development of uterine receptivity, and in the remodeling of uterine tissue for successful embryonic invasion and the establishment of pregnancy.

Sterility in neonatally androgenized female rats and the decidual cell reaction

In female rats, administration of androgen during early postnatal life results in anovulatory sterility characterized by polyfollicular ovaries and persistent vaginal cornification in adulthood. In these androgen-sterilized rats, the acyclic male pattern of gonadotropin secretion results from permanent damage to hypothalamic centers normally responsive to steroid feedback. The capacity of the endometrium to differentiate into deciduoma in response to endometrial stimulation is markedly reduced in the uterus of the androgenized rats receiving an appropriate regimen of progesterone and estrogen injections. The hypothesis is presented that the lowered uterine responsiveness in the androgenized rats is largely ascribable to the effect of androgen given neonatally rather than to the influence of continued exposure to ovarian estrogen. This review deals with the nature of the uterine response to ovarian hormones and the deciduogenic stimulus in androgenized rats in order to verify the mechanism involved in androgen action on the neonatal uterus.

Implantation and decidualization in rodents

This article reviews the main events of embryo-implantation and decidualization in rodents. In common laboratory rodents the embryo attaches to the uterine epithelial lining, usually on days 4 to 6 of pregnancy. A progressive degree of proximity between trophoblast and epithelium occurs until the epithelial cells undergo apoptosis and detach from the basement membrane. During the attachment stage, the spindle-shaped connective tissue cells that underlie the epithelium next to the embryos transform into polyhedral and closely packed decidual cells. Following the epithelial detachment and the breaching of the basement membrane the embryo is thus in direct contact with decidual cells. These cells accumulate organelles associated with synthesis of macro-molecules, intermediate filaments, and eventually lipid droplets and glycogen. Another remarkable feature of decidual cells is the establishment of gap and adherens intercellular junctions. Differentiation of fibroblasts into decidual cells advances antimesometrially and mesometrially, creating in the endometrium several regions of cells with different morphology. The whole phenomenon of decidualization which is normally triggered by the embryo can be artificially induced in pseudo-pregnant or hormonally-prepared animals with the use of diverse stimuli. The uterine epithelium is probably responsible for the transduction of the initial stimulus. Prostaglandins have been shown to be important in the induction of decidualization. More recently other substances such as leukotrienes, platelet-activating factor (PAF), and transforming growth factor (TGF) have been thought to play a role in induction. Much evidence points to prostaglandin production by the decidual cells. New proteins such as a luteotropic factor, desmin, and other molecules were shown to be produced after rat stromal cells undergo decidual transformation. The extracellular matrix of the mouse decidua contains very thick collagen fibrils. Mouse decidual cells are also very active in phagocytosing the thick fibrils, contributing to the remodeling and involution of the decidua that accompanies embryonic growth. Radioautographic data indicates that mouse decidual cells produce and secrete collagen and sulfated proteoglycans.