Feto-maternal relationships: the actions and the control of certain placental hormones

Expression and purification of human placenta lactogen in Escherichia coli

There are many growth factors secreted by placenta including growth hormone, placenta lactogen (PL), prolactin, follicle stimulating hormone, luteinizing hormone, thyroid stimulating hormone, and chorionic gonadotropin. For a systematic study of how these growth factors work together to result in the various biological functions and future clinical applications, it is needed to produce enough quantities of each protein. In this paper, we report the cloning of human PL (hPL) and expression by Escherichia coli (E. coli). Four kinds of expression vectors containing the hPL gene were transformed into several kinds of suitable host strains and grown at 37 and/or 30 degrees C. Determination of the yield of recombinant hPL by SDS-PAGE reveals that among the various conditions, pQE30-PL in E. coli strain M15[pREP4] expressed the largest amount of recombinant hPL at 37 degrees C. However, the expressed recombinant hPL was accumulated in inclusion body forms. The inclusion bodies were solubilized in 8M urea and purified by a His6 tagged affinity column under denaturing condition and the final yield of hPL was determined to be 48 mg/L. Intra-chain disulfide bonds could be formed either by oxidation in the refolding buffer or by air oxidation in the presence of urea. The biological activity was examined by the fact that hPL could stimulate erythroid maturation by the formation of hemoglobin in K-562 cells in the presence of erythropoietin. Initial optimization studies resulted in the production of 282.4 mg/L of hPL.

Growth promoting effects of human placental lactogen during early organogenesis: a link to insulin-like growth factors

Many maternally derived factors may be involved in the regulation of embryonic growth but the control mechanisms involved are poorly understood. Human placental lactogen (hPL) has been implicated in playing a role in the control of embryonic growth. Several investigators suggested that there may be a possible link between the effects of this hormone and insulin-like growth factors (IGFs). In order to determine the growth promoting potential of hPL and involvement of IGFs in the mechanism of action of the hormone, 9.5 d rat embryos were cultured in vitro for 48 h in depleted serum in the presence and absence of hPL with additional IGF antisera. The growth supporting capacity of the serum was reduced by removal of low molecular weight molecules by prolonged filtration of the serum using filters with a molecular weight exclusion of 30 kDa. Addition of hPL (3.2-25.6 ng/ml) to depleted serum significantly improved embryonic growth and development, suggesting that the developing embryo may utilise hPL. The presence of antisera against hPL, IGF-I and -II abolished the hPL-induced increase in the development in all parameters suggesting that there may be a possible link between the IGFs and the effects of hPL on rat embryonic development and this hormone may achieve its growth promoting effects via IGFs.

Expression of the human growth hormone variant gene in cultured fibroblasts and transgenic mice

The nucleotide sequence of the human growth hormone variant gene, one of the five members of the growth hormone gene family, predicts that it encodes a growth hormone-like protein. As a first step in determining whether this gene is functional in humans, we have expressed a mouse metallothionein I/human growth hormone variant fusion gene in mouse L cells and in transgenic mice. The growth hormone variant protein expressed in transiently transfected L cells is distinct from growth hormone itself with respect to reactivity with anti-growth hormone monoclonal antibodies, behavior during column chromatography, and isoelectric point. Transgenic mice expressing the growth hormone variant protein are 1.4- to 1.9-fold larger than nontransgenic controls, suggesting that the protein has growth-promoting properties.

Trinucleate cells and the ultrastructural localisation of bovine placental lactogen

Bovine placental lactogen activity is shown by immunogold electron microscopy to be restricted to the granules and the Golgi body from which they form in the bovine fetal trophectodermal binucleate cell, and granules of similar size and staining reaction in trinucleate "giant" cells found in the maternal uterine epithelium throughout pregnancy. These results support the hypothesis that a fetal binucleate cell forms a maternal giant cell by migration to and fusion with a uterine epithelial cell.

Ultrastructural immunogold investigation of the function and diversity of binucleate cells in the ovine placenta using a monoclonal antibody

Ultrastructural immunogold labelling of ovine placentomes demonstrated that the molecule recognized by the monoclonal antibody SBU-3 is restricted to the fetal binucleate cell granules and Golgi body, and granules of similar size in the syncytium. Quantitative examination shows that the percentage of placentomal mature binucleate cells that are SBU-3-positive increases rapidly from a low level at 29 days of pregnancy to a plateau at virtually 100 per cent from 41 days to term, whereas interplacentomal binucleate cells rarely show label at any stage. There were no detectable differences in ultrastructure between SBU-3-positive or -negative binucleate cells. These results corroborate the hypothesis of syncytium formation by migration of binucleate cells and indicate local control of SBU-3 production and its possible role in villus formation.

Factors influencing fetal growth

Fetal growth is exponential and during the last 20 weeks of gestation the fetus gains 95% of its weight. Genetic, nutritional, environmental, uteroplacental, and fetal factors have been suggested to influence fetal growth. Uteroplacental and umbilical blood flow and transplacental glucose and fetal insulin are major determinants of fetal growth. The role of the fetal pituitary (growth hormone) and thyroid in fetal growth is not well understood; human anencephalic or athyroid fetuses usually have no or only minor retardation of growth. Also, it is not clear whether placental lactogen or somatomedin or a somatostatin-like substance of the placenta and fetus influences fetal growth. From experiments on rats it may be assumed that a specific placental-fetal growth-promoting and growth-regulating factors(s) exists. Identification of such a placental-fetal growth factor(s) in humans might aid in the prevention, diagnosis, and treatment of fetal growth retardation.