Biomedical subjects

Frederick Schatz

Publications and source records attributed to Frederick Schatz.

22 records · Page 2Linked to original sources

PubMed2003

Progestin-regulated expression of tissue factor in decidual cells: implications in endometrial hemostasis, menstruation and angiogenesis.

Expression of tissue factor (TF), the primary initiator of hemostasis via thrombin formation, is induced during progesterone (P4)-stimulated decidualization of human endometrial stromal cells (HESCs), and remains elevated in decidualized HESCs of luteal and gestational endometrium. In HESC monolayers, progestins elevate TF mRNA and protein levels and estradiol (E2) plus progestin further enhance TF levels for weeks despite no response to E2 alone. This in vitro model mimics the chronic differential ovarian steroid upregulation of TF levels associated with in vivo decidualization. After incubation of HESCs with E2 plus progestin to elevate TF expression, the antiprogestin RU486 completely reversed this upregulation. Thus, progesterone withdrawal transformed decidualization-associated hemostasis of the luteal phase endometrium to the hemorrhagic milieu of menstruation. Transient transfections with TF promoter constructs containing SP and EGR-1 binding sites before and after inactivation by site-directed mutagenesis revealed that Sp1 mediates basal and progestin-enhanced TF transcriptional activity. Progesterone receptor involvement in TF expression was further confirmed since RU486 was a pure antagonist of progestin-enhanced TF mRNA and protein expression, and progestin-enhanced, but not basal, Sp1-mediated transcriptional activity. Enhanced TF mRNA and protein levels in HESCs require co-incubation with progestin and epidermal growth factor receptor (EGFR) agonist indicating that the EGFR mediates progestin-enhanced TF expression. A peak in the primary angiogenic agent, vascular endothelial growth factor (VEGF) in luteal phase endometrium may be indirectly regulated by P4. Neither E2, nor progestin, nor E2 plus progestin affected VEGF expression in glandular epithelial and stromal cells, whereas thrombin enhanced VEGF mRNA and protein levels in decidualized HESCs, but not in the epithelial cells. Transudation of clotting factors to perivascular decidual cell TF in the luteal phase would generate thrombin, enabling it to act as an autocrine enhancer of VEGF in decidualized HESCs. Abnormal uterine bleeding complicates long-term progestin only contraceptive use. After Norplant administration, endometrial VEGF levels are elevated and TF levels are selectively enhanced in decidualized HESCs at bleeding sites. Over-expressed VEGF causes blood vessels to become leaky, increasing clotting factor access to decidualized HESC-expressed TF to promote feed-forward thrombin and VEGF formation. Since thrombin and VEGF induce angiogenesis via separate endothelial cell receptors, they may synergize to elicit aberrant angiogenesis, and ultimately lead to focal bleeding.

Decidua↗

PubMed2002

CD1d and invariant NKT cells at the human maternal-fetal interface.

Invariant CD1d-restricted natural killer T (iNKT) cells comprise a small, but significant, immunoregulatory T cell subset. Here, the presence of these cells and their CD1d ligand at the human maternal-fetal interface was investigated. Immunohistochemical staining of human decidua revealed the expression of CD1d on both villous and extravillous trophoblasts, the fetal cells that invade the maternal decidua. Decidual iNKT cells comprised 0.48% of the decidual CD3+ T cell population, a frequency 10 times greater than that seen in peripheral blood. Interestingly, decidual CD4+ iNKT cells exhibited a striking Th1-like bias (IFN-gamma production), whereas peripheral blood CD4+ iNKT clones exhibited a Th2-like bias (IL-4 production). Moreover, compared to their peripheral blood counterparts, decidual iNKT clones were strongly polarized toward granulocyte/macrophage colony-stimulating factor production. The demonstration of CD1d expression on fetal trophoblasts together with the differential pattern of cytokine expression by decidual iNKT cells suggests that maternal iNKT cell interactions with CD1d expressed on invading fetal cells may play an immunoregulatory role at the maternal-fetal interface.

Antigens, CD1↗

PubMed2002

Abnormal uterine bleeding during progestin-only contraception may result from free radical-induced alterations in angiopoietin expression.

Abnormal uterine bleeding is the leading indication for discontinuation of long-term progestin-only contraceptives (LTPOCs). Histological sections of endometria from LTPOC-treated patients display abnormally enlarged blood vessels at bleeding sites. Paradoxically, a trend toward reduced endometrial perfusion in LTPOC users has been reported in these patients. We hypothesized that hypoxia/reperfusion-induced free radical production inhibits the expression of angiopoietin-1 (Ang-1), a vessel stabilizing factor, leaving unopposed the effects of endothelial Ang-2, a vessel-branching and permeability factor. Immunohistochemical studies confirmed selective decreases in stromal cell Ang-1 in LTPOC-exposed endometrium. To indirectly assess whether LTPOC enhances endometrial free radical production, immunostaining was conducted for the phosphorylated form of the stress-activated kinases SAPK/JNK and p38. These kinases were greatly increased in endometria from LTPOC-treated patients. Interestingly, the endothelial cells but not the stromal cells displayed enhanced immunostaining for the phosphorylated mitogen-activated kinase (pMAPK) after LTPOC treatment. To further examine the effects of progestin, hypoxia, and reactive oxygen species (ROS) on the regulation of Ang-1 and Ang-2 as well as the activation of MAPK, SAPK/JNK, and p38 by the relevant cell types, we conducted in vitro studies with cultured human endometrial stromal cells (HESCs) and human endometrial endothelial cells (HEECs). Cultures of HESCs were treated with vehicle control, estradiol (E(2)), or with medroxyprogesterone acetate +/- E(2) under hypoxic and normoxic conditions. Although medroxyprogesterone acetate but not E(2) increased Ang-1 expression, hypoxia greatly decreased Ang-1 protein and mRNA expression. In contrast, HESCs did not appear to express Ang-2 protein or mRNA. Conversely, cultured HEECs did not appear to express Ang-1, but expressed Ang-2, the levels of which were significantly increased by hypoxia. Hypoxia also induced the phosphorylation of SAPK/JNK and p38 in both cultured HESCs and HEECs. Moreover, ROS such as that observed after hypoxia/reperfusion resulted in the activation of SAPK/JNK and p38 in HESCs and HEECs and inhibited Ang-1 in cultured HESCs. These effects could be blocked by oxygen radical scavengers. Consistent with the in vivo studies, MAPK was activated after ROS treatment in HEECs but not in HESCs. Our findings suggest that LTPOC-induced endometrial bleeding occurs as a result of hypoxia/reperfusion-induced free radicals that directly damage vessels and alter the balance of Ang-1 and Ang-2 to produce the characteristic enlarged and permeable vessels that are prone to bleeding.

Angiopoietin-1↗

PubMed2002

Differential effects of thrombin and hypoxia on endometrial stromal and glandular epithelial cell vascular endothelial growth factor expression.

Ovarian steroids and/or premenstrual endometrial hypoxia are thought to restore the endometrial vasculature shed during menstruation by elevating endometrial vascular endothelial growth factor (VEGF) levels. During the luteal phase, VEGF levels peak, progesterone induces estradiol (E(2))-primed human endometrial stromal cells (HESCs) to decidualize and express tissue factor (TF), and endometrial vascular permeability is enhanced. The latter would present circulating clotting factors to decidual cell-expressed TF to form local thrombin. HESCs were incubated in serum-supplemented medium containing vehicle (control) or 10(-8) M E(2) or 10(-7) M medroxyprogesterone acetate (MPA) or E(2) + MPA for 7 d to induce decidualization, while monolayers of human endometrial glandular epithelial cells (HEGECs) formed during 4-d incubation of glands. The medium was exchanged for a defined medium containing corresponding vehicle or steroids +/- thrombin under normoxia or hypoxia (0-1% O(2)). Hypoxia enhanced secreted immunoreactive VEGF levels by severalfold in HESCs and HEGECs, but the steroids did not affect VEGF output in either cell type under normoxia or hypoxia. In E(2) + MPA-decidualized HESCs, VEGF levels were elevated by 0.1 U/ml of thrombin, and 0.5-2.5 U/ml of thrombin elicited maximum effects. The addition of 0.5 U/ml of thrombin evoked a time-dependent enhancement of VEGF levels and about an 8-fold increase at 48 h (P < 0.02; n = 6). Northern blotting indicated that E(2) + MPA-decidualized HESCs expressed VEGF(121), VEGF(165), and VEGF(189) mRNA, which were enhanced severalfold during 5- to 20-h incubation with thrombin. Moreover, TRAP, a synthetic peptide activator of the constitutively expressed protease activated receptor-1 thrombin receptor in decidualized HESCs, also elevated secreted VEGF levels. By contrast, HEGECs were unresponsive to thrombin added alone or with ovarian steroids. These results suggest that thrombin formed by progestin-augmented TF levels acts as an autocrine enhancer of VEGF expression in decidualized HESCs. Because angiogenesis occurs in a matrix of decidualized HESCs, these in vitro results provide a novel mechanism to account for both the peak in VEGF and angiogenesis in luteal phase human endometrium.

Cell Hypoxia↗