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was noted in typical stromal-type decidual cells, villus cytotrophoblast as well as extravillus cytotrophoblast cell columns. Second passage first trimester human trophoblast cells (characterized by their expression of cytokeratin, placental alkaline phosphatase, and hCG production) were cultured in 96 well plates (lo4 cells/well) in the presence ofpure TGF-c( or anti-TGF-a Ab or no additive in quadruplicates for 18 h prior to exposure of “H-TdR (1 &i/ml) for 6 h, to measure 3H-TdR uptake (/3 counts). Presence of TGF-a (0.045-I 00 ng/ml) caused a dose-dependent stimulation of proliferation, reaching a near plateau at 6- 100 ng/ml to slightly more than double the basal level. The presence of anti-TGF-cx Ab alone (25 pg/ml) did not significantly influence the proliferation. Exogenous TGF-a also reduced syncytium formation in culture. These results reveal that first trimester human decidual cells, and to some extent villus and extravillous cytotrophoblast cells are sources of TGF-n which stimulates trophoblast cell proliferation and reduces syncytium formation. (Supported by the MRC Canada.)

ULTRASTRUCTURE OF THE INTER-ENDOTHELIAL JUNCTIONS OF TERMINAL VILLOUS CAPILLARIES IN THE HUMAN PLACENTA I,. Leach &J. A. Firth (Department of Anatomy & Cell Biology, St Mary’s HMS, London W21PG, UK)

Although transplacentally transported molecules must traverse both the trophoblast and the fetal endothelium, permeability of placenta1 capillaries has been largely ignored. As the paracellular clefts are the site of the ‘small pore’ system of continuous non-brain capillaries, we have studied the structure of these clefts in the terminal villous capillaries.

Selected lobules of term human placentae (3) were dually perfused with oxygenated TC 199 medium for a recovery period of 20 min. They were perfusion fixed and mordanted with ferrocyanide prior to processing for TEM. Thirty capillaries from five blocks made from each perfused placental lobule were studied, total N = 90.

The lateral membranes of endothelial cells were found to be separated by a paracellular cleft of mean width 15.65 +- 2.2 mu. At zonular regions (mean number = 1.6 + 0.9 per cleft, range = l-4) the two membranes approach each other more closely and frequently appear to fuse. However, progressive tilting of the specimens +60” showed a gap of mean width 4.06 + 1.2 nm exists between the membranes in 94 per cent of tight junctions. The wide regions of the clefts usually showed ‘linkers’, strands of glycocalyx-like material spanning the gap.

We conclude that these placental capillaries resemble closely other non-CNS type of continuous capillaries in having tight junctions with membrane separations and wide zones with linkers rather than zonulae adhaerentes. Linkers may act as a three-dimensional filter in series with restrictive pores in the tight junctional strands.

MEASUREMENTS OF ATRIAL NATRIURETIC PEPTIDE (ANP) IN HUMAN PLACENTA AND FETOMATERNAL COMPARTMENTS J. N. Lee & E. M. Tsai (Department of Obstetrics/Gynaecology, Kaohsiung Medical College, Kaohsiung, Taiwan, R. 0. C.)

ANP is a very potent hormone regulating body fluid homeostasis, blood pressure and renal function. The purpose of this study was to establish a high performance liquid chromatogra-

412 Placenta (1991), Vol. I2

phy (HPLC) and radioimmunoassay (RIA) system to measure ANP levels in human placental tissue, normal pregnancy, abnormal pregnancy and fetomatemal compartments. The results reveal that human placenta contains an ANP-like substance which is similar or identical to that of standard synthetic ANP physicochemically and immunologically. The plasma levels of ANP increase gradually to about 22 weeks and plateau thereafter. Significantly higher levels of ANP in pre-eclampsia and twin pregnancy, also, in umbilical artery than in vein were noted. In conclusion, human placenta contains ANP and this ANP seems to play a role as a paracrine organ during pregnancy.

STIMULATION OF BeWo (CHORIOCARCINOMA) CELL GROWTH BY INTERLEUKIN- 1 M. P. Lewis, M. H. F. Sullivan & M. G. Elder (Institute of Obstetrics & Gynaecology, R.P.M.S., Hammersmith Hospital, Du Cane Road, London W12 OHS, UK)

Impaired trophoblast growth has been implicated in both pre-eclampsia and spontaneous abortions. The decidua has been shown to influence trophoblast cell hCG production and it may be that decidual factors will also influence trophoblast growth in both normal and abnormal pregnancy. Decidual tissue produces a number of cytokines including interleukin- 1 (IL-l), which may affect cell growth; recent work in this department has confirmed that both decidual macrophages and stromal cells in culture can synthesise IL- 1.

BeWo cells, a choriocarcinoma cell line which may be used as a model for trophoblast in vitro, were plated in RPM1 1640 medium with no serum supplementation at a density of 0.5 x lo6 cells per T30 flask and cultured with different concentrations of IL-l for up to 7 days. IL-l at concentrations of l-100 pg/ml had a dose-dependent stimulatory effect, as measured by 3H-thymidine incorporation and cell counting. After 48 h of culture with 100 pg IL-l/ml, cell numbers were increased from 1.53 f 0.09 x lo6 cells to 1.96 + 0.05 X lo6 cells, and 3H-thymidine incorporation from 498,000 cpm/flask to 840,000 cpm/flask. Similar results were found after incubation times up to 7 days. Basal cell growth was increased by the inclusion of 10 per cent fetal calf serum in the medium, but the stimulatory effects of IL-l on cell growth were still detectable.

These results show that IL- 1 is an important regulator in BeWo cell growth in vitro, and studies are in progress to investigate the biochemical mechanisms involved.

THE EFFECT OF DIFFERENT EXTRACELLULAR MATRIX PROTEINS AND DIFFERENT MEDIA ON THE OUTGROWTH OF TROPHOBLAST CELLS ISOLATED FROM HUMAN TERM PLACENTAE J. Leyten, C. Luyten, R. Pijnenborg & A. Van Assche (Department of Obstetrics & Gynecology, University of Leuven, Belgium)

In order to study the interaction of trophoblast cells with maternal tissue, a monolayer culture system was established. We modified the methods described by Kliman et al, 1986,