Stanley R. Glasser

Trophoblast giant cell release of placental lactogens: Temporal and regional characteristics

Placental lactogen (PL) production by rat trophoblast giant cells was studied using in vitro methods. The influence of trophoblast giant cell location within the conceptus and day of trophoblast giant cell isolation on the type of PL released in vitro were investigated. The effect of trophoblast giant cell location on the amount of PL, progesterone, and testosterone released in vitro was also evaluated. Trophoblast giant cells release two types of PLs in vitro; a high-molecular-weight lactogen, PL-1, and a low-molecular-weight lactogen, PL-2. The type of PL released by trophoblast giant cells was not influenced by their location within the conceptus at the time of dissection. Location did influence the amount of hormone produced by trophoblast giant cells. Mural trophoblast giant cells were more active in the production of PL, progesterone, and testosterone. The type of PL released by trophoblast giant cells is highly dependent upon the day of gestation the cells are removed for study. Trophoblast giant cells isolated on Day 10 of gestation release predominantly PL-1, while those cells isolated 24 hr later (Day 11 of gestation) release predominantly PL-2. The switch from PL-1 to PL-2 production that occurs in vivo does not occur under the in vitro conditions employed in this report.

Biochemical and Structural Changes in Uterine Endometrial Cell Types Following Natural or Artificial Deciduogenic Stimuli

Attachment of the mammalian embryo to the maternal uterus is a signal event in the highly regulated program of synchronized, apparently independent but interdependent events which define unique interactions between two organisms of different genetic derivation. The focus of this essay will be the role of the individual endometrial cell types, vis-a-vis the blastocyst, in these implantation related events. This paper will suggest that at the present time, only a very generalized understanding of the regulatory mechanisms underlying blastocyst attachment has been established. Present models are, therefore, of limited predictive use in resolving problems in human infertility. In an effort to recognize elements with which to formulate a more functional model particular emphasis will be placed on the responses to endocrine, paracrine, and autocrine mechanisms which come into play following the attachment of trophoblast to the uterine epithelium, i.e., the adhesive and post-implantation phases of implantation.

Separated Cell Types as Analytical Tools in the Study of Decidualization and Implantation

Various strategies used by different species to assure successful blastocyst-endometrial interaction have evolved. The advantages and limitations of the decidual cell reaction (DCR) as a model for studying these events have been recognized (Psychoyos, 1973; Glasser and Clark, 1975; Glasser and McCormack, 1980a,c). Concise descriptions of the sequential relationships of the steroid hormones (Psychoyos, 1973; Glasser and Clark, 1975) and the different hormonal responses of epithelial and stromal cells have been provided (Martin and Finn, 1968; Tachi et al., 1972; Martin et al., 1973a,b). These researches have validated the determinant role of progesterone in the development of uterine sensitivity. Certain species require estrogen to complete the maturation of the sensitive uterus to the final stages of uterine receptivity for ovum implantation. Detailed cytological, ultrastructural (Nilsson, 1970; Enders and Schlafke, 1971; Schlafke and Enders, 1975; Sherman and Wudl, 1976), and physiological correlates (Meyers, 1970; Psychoyos, 1973; Glasser and Clark, 1975; Glasser and McCormack, 1979) of these events are also part of the literature.

Intermediate filaments of the midgestation rat trophoblast giant cell

Trophectoderm (TE) of the rodent blastocyst, the preimplantation precursor of the trophoblast giant cell (TGC), is the first embryonic cell to exhibit intermediate filaments (IF). The two IF proteins of TE (54K and 46K) have been variously described as trophectoderm specific, noncytokeratin, or cytokeratin and have been identified with Endo A and Endo B, IF proteins extracted from extraembryonic endodermal cells. IF proteins of midgestation rat TGC, the postimplantation descendant of TE, were compared to IF proteins of various rat simple epithelial cells by two-dimensional gel electrophoresis, partial proteolytic digest, antibody recognition on electrophoretic transfer, and antibody recognition by indirect immunofluorescence. The two TE IF proteins at 54K and 46K were identified in TGC IF and recognized by anti-Endo A, anti-Endo B, respectively, and anticytokeratins. TGC were found to possess additional cytokeratins at 52K, 45K, 43K, and 40K. The profile of TGC cytokeratins was qualitatively identical to that of various rat simple epithelial cells. The results suggest that (a) TE and TGC IF proteins are cytokeratins, (b) TE and TGC cytokeratins are characteristic of a simple epithelial cell, and (c) the morphologic and functional differentiation of TE to TGC is accompanied by elaboration of the cytokeratin profile.

Functional Development of Rat Trophoblast and Decidual Cells During Establishment of the Hemochorial Placenta

ABSTRACT Progesterone alters gene expression of uterine stromal cells, rendering them sensitive to decidual transformation. Prenidatory estrogen, by qualitatively modulating progesterone-induced gene expression, activates the blastocyst and initiates implantation. Implantation is the hormonally programmed migration of trophoblast through decidualized stroma in order to bring it into apposition with the maternal vasculature prior to gestation day 10 in the rat. At that time, the luteotropic peptide hormone secreted by the trophoblast giant cell (rat placental lactogen, rPL) becomes a primary regulatory factor in maintaining the latter period of pregnancy. Activation reorganized the blastocyst cytoskeleton. Microtubule assembly and distribution are associated with the outgrowth of motile trophoblast cells which insinuate themselves between uterine epithelium. A progressive decrease in specific estrogen receptor binding of decidual cells begins when implantation is initiated (day 4) and reaches 30% at the time (days 5–6) the trophoblast is moving through the superficial decidual cells. Progesterone and estrogen are being actively synthesized and estrogen receptors are being actively accumulated by the advancing trophoblast. Estrogen is responsible for the recruitment of progesterone-sensitized, deep, metastable stromal cells for decidual transformation. Migration of trophoblast through these decidual cells (days 7-8) is associated with the onset of secretion of proteolytic enzymes by the trophoblast. Invasion of deep decidual cells is correlated with peak proteolytic enzyme activity (days 8-9) which decreases markedly when the trophoblast comes into apposition with maternal vascular endothelium (days 9-10). The cessation of proteolytic tissue reorganization coincides with the breaching of the decidua, the entry of the trophoblast into the maternal sinuses and peak rPL secretion (day 10). Failure of the trophoblast to penetrate the decidual barrier on schedule prevents hemochorial placentation and interrupts pregnancy. No extrinsic regulatory factors for trophoblast differentiation have yet been identified. Trophoblast progesterone, estrogen and testosterone could be considered as possible intrinsic regulators of proteolytic invasion and rPL synthesis and secretion. DEDICATION This chapter is dedicated to the late James Hain Leathern of Rutgers University. He was our friend and teacher. Jim Leathern was a unique person. He was a warm, expansive human being. His significant contributions to science derived from a robust intellect and an unbridled enthusiasm. He will have a lasting influence on reproductive biology and endocrinology which extends beyone his own scientific contribution.

Cellular and Molecular Aspects of Decidualization and Implantation

A comprehensive analysis of the molecular and cellular mechanisms underlying decidualization and implantation is not possible today. This is because the three concurrent lines of research, i.e., molecular endocrinology, cell cycle kinetics and biochemistry, which have contributed the recent advances to these studies, have progressed with almost no interaction in parallel fashion. An initial attempt at integrating these data as they apply to the mechanisms of decidualization and implantation will be the task of this contribution.

Progesterone Directed Gene Expression in Rat Uterine Stromal Cells

When embryos attach to the luminal epithelium in the rat uterus they somehow induce differentiation of the stromal cells underlying the attachment site, giving rise to an enormous increase in the size of the stromal cell compartment through both cell proliferation and cell growth. This reaction, decidualization, is localized to areas of embryo attachment (reviewed in DeFeo, 1967). Both attachment of the embryo to the luminal epithelium and differentiation of the stromal cells in response to embryo attachment require conditioning of the uterus with steroid hormones (Psychoyos, 1973). If the uterus is hormonally prepared, decidualization can be obtained using an intraluminal traumatic or chemical artificial stimulus. In response to these stimuli stromal cells along the entire length of the uterus will differentiate (DeFeo, 1967).

Morphological and immunohistochemical differentiation patterns of rabbit uterine epithelium in vitro

We describe morphological and immunohistochemical changes of uterine epithelium from immature rabbits in vitro in response to hormonal treatments, using a matrix-coated semipermeable filter. These investigations were compared to in vivo studies of uterine epithelium from immature rabbits treated with estrogen and/or progesterone. In vitro, polarization of the epithelium seems to be best developed under progesterone dominance, and the pattern of cell organelles is similar to those seen in vivo. Two types of apical protrusions could be observed in cultures treated with progesterone, some shaped like domes, containing cell organelles, and some irregular in shape with small lucent vesicles. Both types of apical differentiation are typical for the in vivo situation. In vitro, estrogen leads to a more pseudostratified growth pattern of the cells. They develop apical protrusions with big vesicles probably containing mucin, as in vivo. Treatment with both steroid hormones leads to a heterogeneous response of the uterine epithelial cells in culture, some cells responding more to the estrogen, others to the progesterone whereas in vivo the progesterone-dominant features are obvious. Immunohistochemistry of uteroglobin in monensin-treated cultures gives evidence for uteroglobin secretion in all cultures, but to a lesser extent in the untreated, and this is strongly increased in cultures treated with estrogen and progesterone. These results correspond to observations made in vivo. This in vitro cell culture method seems therefore to provide a useful model for investigating the regulatory mechanisms of sexual steroid hormones and the cell biology of uterine receptivity.

The Interaction of Trophoblast with Endometrial Stroma

Implantation involves initial interaction between the embryo and uterine epithelium. Where placentation is chorio-epithelial, this relationship continues throughout gestation. In other cases in which invasion occurs, the embryo interacts with mesenchymal elements of the uterus. In species showing interstitial implantation, the embryo-stromal inter-relationship is much more long-lived than the embryo-epithelial interaction and arguably more important in the success of the pregnancy since it is the means by which the embryo gains access to nutrients supplied through the maternal blood stream (Mossman, 1987). The intention of this short article is not to review decidualisation or placentation, but to comment on model systems that may offer promise for an improved understanding of morphogenesis in the trophoblastic interaction with maternal stroma in rodent and primate.

In Vitro Models of Implantation

Blastocysts are capable of attaching to a uterus only after it has been appropriately prepared by ovarian steroid hormones (receptive uterus). 1,2 They can, however, attach to extrauterine sites regardless of the hormonal environment.3 These data suggest that under certain conditions the apical surface of the uterine epithelial (UE) cell expresses molecules (ligands) which do not permit blastocyst attachment (non-receptive). It has been proposed that interactions between UE cells and various regulatory agents (hormones, growth factors) effect (induce, stimulate, repress) structural and functional changes at the apical surface of the UE cell that allow nidation.