Morphological and immunohistochemical analysis of placental tissue from 12 days to term using antibodies directed against the unique carboxyl terminal peptide of human chorionic gonadotrophin beta subunit, human placental lactogen (hPL) and pregnancy-specific beta -glycoprotein reveals that an intermediate from of trophoblast with distinctive features exists. This cell has a diverse morphological expression and is located overlying chorionic villi, in the trophoblastic columns, basal plate and the trophoblastic shell. Although all three placental proteins are localized in this cell the predominant hormone is hPL, which can serve as an immunocytochemical marker. One of the primary functions of this cell is in implantation and in the establishment of the uteroplacental circulation since it extensively invades the spiral arteries at the placental site. It is proposed that this distinctive from of trophoblast be termed ‘intermediate trophoblast’.
Ovine trophoblastic protein-1 (oTP-1), an early secretory protein of the sheep blastocyst, was purified after culturing day 14-16 conceptuses for 24 h in vitro. The localization of oTP-1 in the pregnant day 16 sheep uterus was determined immunocytochemically. The protein was associated with trophectoderm cells of the elongated blastocyst and with the surface and upper glandular epithelium of the maternal uterus. Receptors that bound oTP-1 with high affinity (Kd = approximately 2 X 10(-10) M) were present in crude membrane preparations derived from homogenates of endometria from day 12 nonpregnant and anestrous ewes. Uterine infusion of 125I-labeled oTP-1 into day 12 nonpregnant ewes showed that the majority of the radioactivity was retained in the uterus, and only very small amounts of intact protein appeared to enter the maternal vasculature. There was no significant association with the corpora lutea, ovaries, or other tissues tested. oTP-1 failed to compete with ovine PRL for rabbit mammary gland receptors or with hCG or bovine LH for sheep luteal cell receptors, and the oTP-1 did not stimulate progesterone production by dispersed luteal cells from day 12 cycling ewes. Incubation of endometrial explants from day 12 nonpregnant ewes with 5 micrograms/ml oTP-1 resulted in increased rates of protein release into the medium. Two-dimensional polyacrylamide gel electrophoresis revealed that the synthesis of six polypeptides was stimulated selectively by the presence of oTP-1. Together these data suggest that oTP-1 acts on the maternal endometrium. It is suggested that the interaction of oTP-1 with uterine endometrium may elicit maternal responses which contribute to the maintenance of pregnancy in the sheep.
We have prepared monoclonal antibodies by immunizing BALB/c mice with purified human term placental plasma membranes. The antibodies were selected to show predominant specificity for trophoblast and trophoblast derivatives. Four of these antibodies have been found to recognize the placenta‐specific isozyme of alkaline phosphatase (EC 220.127.116.11), and to cross‐react with the closely related testis form of this enzyme. One antibody recognized transferrin, a serum protein with an abundant placental receptor. The specificities of the other antibodies, whose target antigens are unknown, are described. Their reactivity with some human tumour‐derived epithelial cell lines suggests that they may provide useful markers of human trophectoderm differentiation, as well as for properties selected for during tumour progression.
The results of the diagnostic application of first trimester trophoblast sampling in 100 pregnancies are reported in detail. Further improvement of the method for routine, direct chromosome analysis resulted in a technique which proved to be fast, simple, and efficient. We found that short-term incubation of villi permits the application of many experimental methods, such as visualization of sister chromatid exchanges and bromodeoxyuridine (BrdU) incorporation. Fetal karyotyping was successful in each of the 96 pregnancies in which fetal material was obtained from a total of 98 fetuses. There were 42 males and 56 females, and an abnormal chromosome constitution was found in 12 cases. Two trisomic fetuses were found among the eight pregnancies at risk for Duchenne muscular dystrophy, and this indicates that fetal sexing (which is achieved with our method in two hours) should not be performed without chromosome visualization. The results indicate a risk of 8% of an abnormal fetus for mothers aged 35 years or more, while the risk of failure of sampling and of spontaneous abortion after villi sampling were 4 and 6%, respectively. Enzyme determinations were performed in three pregnancies at risk for gangliosidosis GM1, Niemann-Pick disease, and Hurler syndrome. In this last case inconsistency between the results of the assay of iduronidase on chorionic villi and amniotic fluid cells was found. This unexplained error indicates the need for extensive characterisation in chorionic villi of the series of enzymes involved in metabolic diseases.