Placental protein 12 (PP12) is induced in the endometrium by progesterone

Peptides and proteins in the human endometrium

Human endometrium is composed of three layers: stratum compactum, stratum spongiosum and stratum basale. Stratum compactum is the superficial layer made up of openings of the uterine glands and some stromal cells. Stratum spongiosum is the middle layer containing mainly dilated glands and little stroma. Stratum basale is the deepest layer adjoining the muscularis. It consists of primordial glands and compact stroma. Stratum compactum and stratum spongiosum form stratum functionale which is subject to cyclic changes and is removed during menstruation.

Differential regulation of insulin-like growth factor binding protein-1 and -2 by insulin in the baboon (Papio anubis) endometrium

BACKGROUND

The purpose of this study was to examine the effect of insulin on expression and synthesis of IGFBP-1 and IGFBP-2 in the baboon endometrium in vitro.

METHODS

Baboon endometrial explants collected from cycling, ovariectomized, steroid-treated, simulated-pregnant and pregnant animals were cultured for 48 h in the presence or absence of insulin, with or without estradiol, progesterone and hCG.

RESULTS

Insulin clearly inhibited IGFBP-1 production and mRNA expression in a time- and dose-dependent manner, whereas IGFBP-2 synthesis was not significantly affected. The inhibitory effects of insulin on IGFBP-1 were more evident in explants of non-pregnant tissue or tissue away from the implantation site. In the absence of insulin, synthesis of IGFBP-1 was induced in explants with low levels of de novo synthesis whereas IGFBP-2 synthesis was inhibited. This effect was potentiated by steroids and hCG in the explant cultures.

CONCLUSION

Insulin differentially regulates endometrial IGFBP-1 and IGFBP-2 secretion in the baboon.

Transvaginal progesterone supplementation increases serum insulin-like growth factor-binding protein-1 levels

The objective of this study was to assess the effect, which might be mediated by progesterone-dependent insulin-like growth factor-binding protein-1 (IGFBP-1), of micronized progesterone supplementation through different administration routes (oral or vaginal) on successful pregnancy. A total of 299 anovulatory women were treated with clomiphene citrate (100 mg/day on days 5-9 of the menstrual cycle) to stimulate follicular growth. Human chorionic gonadotropin (hCG, 10,000 IU) was injected intramuscularly when at least one follicle was > 20 mm in diameter as monitored by transvaginal ultrasonography. Micronized progesterone (300 mg/day, at bedtime) was used as supplementation of progesterone randomly by oral (n = 153) or vaginal (n = 146) administration from approximately 36-48 h after hCG administration until the following menstrual period or the 10th week of gestation from the last menstrual period. As a control, 18 apparently healthy females with at least three regular menstrual cycles immediately before the present study were also recruited but no interventions were made. Serum levels of progesterone, IGFBP-1, insulin-like growth factor-I (IGF-I) and insulin were determined on day 8 after hCG administration (day 0 indicates the day of hCG administration; progesterone supplementation group) or on day 21 of the menstrual cycle (controls). In the midluteal phase higher progesterone and lower IGFBP-1 levels were observed in the serum from patients supplemented with oral progesterone than in those using vaginal progesterone. Total and continuing pregnancy rates were also higher in the patients using oral than in those using vaginal progesterone (p < 0.04, by the zI-test). However, there was no difference in serum IGF-I or insulin level between the groups. It was concluded that oral administration of micronized progesterone at bedtime appears to be a convenient method of luteal supplement, whereas vaginal supplementation during the luteal phase might directly stimulate endometrial production of IGFBP-1, which possibly, in turn, deters embryo implantation and results in a decrease in the pregnancy rate.

Endometrial response to hormone replacement therapy as assessed by expression of insulin-like growth factor-binding protein-1 in the endometrium

OBJECTIVE

To assess endometrial response to parenteral levonorgestrel in hormone replacement therapy by means of morphological criteria and immunohistochemical staining of insulin-like growth factor-binding protein-1 (IGFBP-1).

DESIGN

Endometrial samples were collected from 35 postmenopausal women after 12 to 22 months of continuous combined estrogen-progestin therapy. All subjects were treated with parenteral progestin. A group of 8 women was treated with a subdermal levonorgestrel-releasing implant, and 27 women had a levonorgestrel-releasing intrauterine device (IUD). Sections of formalin-fixed paraffin-embedded biopsies were used for immunohistochemistry and after hematoxylin-eosin staining for routine histologic examination.

RESULTS

Atrophic epithelium with pronounced decidual reaction in the stroma was detected by histologic examination in all endometrial samples obtained from 27 women treated with the levonorgestrel-releasing IUD. In contrast, the endometrium was proliferative in seven of eight (87.5 percent) biopsies obtained from women treated with the levonorgestrel-releasing implant. Immunoreactive IGFBP-1 was detected in decidualized stromal cells in all endometrial samples obtained during intrauterine levonorgestrel therapy, whereas only one of eight samples obtained from women treated with subdermal levonorgestrel exhibited weak staining for IGFBP-1.

CONCLUSIONS

Our data show that both the morphological and biochemical response of post- menopausal endometrium to parenteral levonorgestrel was strikingly different, depending on the route of progestin administration, and that the decidual reaction and epithelial atrophy induced by intrauterine levonorgestrel were associated with expression IGFBP-1 in decidualized stromal cells.

Immunolocalization of progesterone-induced uterine protein-1 in human endometrium during the menstrual cycle and in the placenta throughout gestation

OBJECTIVE

Progesterone-induced uterine protein-1, a product of secretory endometrial stromal cells (relative molecular mass 70,000, isoelectric point 5.7), was immunolocalized in endometrium and placenta.

STUDY DESIGN

Biopsies were performed to obtain human endometrium and placenta throughout the menstrual cycle and gestation. Formalin-fixed, paraffin-embedded tissues (n = 74) were sectioned and immunohistochemically stained for progesterone-induced uterine protein-1 by the avidin-biotin peroxidase procedure. Isolated endometrial cells were also stained for progesterone-induced uterine protein-1.

RESULTS

Progesterone-induced uterine protein-1 localized in proliferative endometrial stroma and in early to midsecretory stroma and ciliated epithelia and vanished from nonpregnant, late-secretory endometrium yet localized in the decidua, syncytiotrophoblast, and intermediate cytotrophoblast during pregnancy. Isolated, cultured endometrial stromal but not epithelial cells displayed progesterone-induced uterine protein-1 staining.

CONCLUSION

Endometrial progesterone-induced uterine protein-1 localization shifts from stromal to epithelial, coinciding with the time of ovulation, fertilization, and implantation. This observation, combined with the disappearance of progesterone-induced uterine protein-1 in late-secretory, nonpregnant endometrium and its presence in decidua and trophoblast, suggests that progesterone-induced uterine protein-1 may play a role in decidualization, endometrial or embryo cross-talk, or placental physiologic features.

Serum levels of insulin-like growth factor I and insulin-like growth factor-binding protein-1 and -3 in women with regular menstrual cycles

OBJECTIVE

To investigate the cyclic changes of serum insulin-like growth factor (IGF-I), IGF-binding protein-1 (IGFBP-1) and IGFBP-3 levels during ovulatory menstrual cycle.

DESIGN

A prospective study following a preset protocol.

SETTING

A tertiary-care academic medical center.

PARTICIPANTS

Thirty young female adults with regular menstrual cycles were recruited (18 with normal luteal phase and 12 with inadequate luteal function confirmed by serum P levels).

MAIN OUTCOME MEASURES

Serum concentrations of IGF-I, IGFBP-1, and IGFBP-3 from women with regular menstrual cycles were assayed. Circulating E2 and P levels also were determined to certify the ovulatory cycles.

RESULTS

In women with normal luteal function, there was a peak of serum IGFBP-1 levels before ovulation concomitant with the preovulatory E2 peak. The nadir of serum IGFBP-1 levels was in the midluteal phase. Circulating IGFBP-1 elevated rapidly during late luteal phase and reached a peak on the 1st day of menstruation then declined slightly until a preovulatory IGFBP-1 peak occurred. In women with inadequate luteal function (midluteal serum levels of P < 10 ng/mL [conversion factor to SI unit, 3.180]), the preovulatory increase in serum IGFBP-1 was not significant and the circulating IGFBP-1 levels fluctuated throughout the menstrual cycle except for a unique peak of serum IGFBP-1 on the 1st day of menstruation. By contrast, there were no cyclic changes of serum IGF-I and IGFBP-3 levels in women with regular menstrual cycles, including both normal nad inadequate luteal functions.

CONCLUSIONS

The preovulatory increase in serum IGFBP-1 levels may be of follicular origin and associated with the subsequent luteal function in females with ovulatory cycles. However, the involvement of IGFBP-1 in the process of follicular maturation and luteogenesis, as well as the regulation of luteal function, needs to be explored further.

Insulin-related growth factor binding protein-1 levels in ovum donation pregnancies

The finding that endometrial maturation may be delayed following hormone replacement therapy has suggested that a generalised endometrial dysfunction may exist in ovum recipients. In order to investigate this suggestion further, circulating levels of IGFBP-1 were measured in samples taken throughout pregnancies conceived either spontaneously or following ovum donation. When analysed at two-weekly intervals, the serum levels of IGFBP-1 in ovum donation pregnancies failed to show the expected peak towards the end of the first trimester and were significantly reduced at week ten (U = 364.5, p = 0.0002) and twelve (U = 138.0, p = 0.0047). For the remainder of pregnancy, circulating IGFBP-1 levels were similar in both groups. The birth weight of children born to the ovum donation group was not significantly different from a normal control group, suggesting that circulating levels of IGFBP-1 in early pregnancy do not reflect local function and that IGFBP-1 does not have an essential function (in relation to birth weight) in early pregnancy.

Immunohistochemical localization of two endometrial proteins in the early days of human pregnancy

Insulin-like growth factor binding protein-1 (IGFBP-1) [also known as placental protein 12(PP12)] and placental protein 14 (PP14) have been identified by specific immunostaining in early pregnancy specimens obtained 13-35 days of gestation. PP12 was evident in a discrete number of stromal decidual cells at the deciduotrophoblastic interface and under the endometrial surface epithelium. These cells did not have the rounded appearance of classic decidual cells but most often displayed cytoplasmic expansions. Staining for PP14 was strictly localized to the glandular epithelium of the endometrium. Implantation of the conceptus may be an important mechanism in the early expression of PP12 but not PP14.

Growth factors and growth modulators in human uterine endometrium: their potential relevance to reproductive medicine

OBJECTIVE

To provide an up-to-date, comprehensive review on the presence and regulation of growth factors (GFs), GF receptors, and GF regulatory proteins in human endometrium in an effort to understand the potential roles of these proteins in endometrial cell mitosis and differentiation and in endometrial-trophoblast interactions.

DESIGN

Relevant studies were identified through a computerized bibliographic search (MEDLINE; BRS Information Technologies, a division of Maxwell Online, Inc., McLean, VA) and through manual scanning of recent relevant journals.

RESULTS

Several GFs, their receptors, and regulatory proteins have been identified in endometrium, and cellular localization and steroid-dependence of these proteins as well as action of several growth modulators on endometrial cell function have been studied. Epidermal growth factor, transforming growth factor (TGF)-alpha, platelet-derived growth factor, insulin-like growth factors (IGFs) and their binding proteins, fibroblast growth factor (FGF), TGF-beta, colony-stimulating factor (CSF)-1, and interferon-gamma regulate mitosis of endometrial cellular components in vitro. Endothelin-1 may participate in vasoconstriction and FGF may participate in angiogenesis in this tissue in vivo. Interleukins-1 and -6 are believed to be involved in endometrial T-cell activation, and TGF-beta, CSF-1, the interleukins, and the IGFs likely mediate endometrial-trophoblast interactions. The role of tumor necrosis factor in endometrium remains uncertain.

CONCLUSIONS

Current evidence supports the thesis that GFs play a central role in cyclic mitosis and differentiation of endometrial cellular components, recruitment of macrophages in decidualizing endometrium, endometrial-trophoblast interactions, early pregnancy maintenance, tissue shedding in the absence of implantation, and endometrial functionalis regeneration.

Insulin-like growth factor regulation of human endometrial stromal cell function: coordinate effects on insulin-like growth factor binding protein-1, cell proliferation and prolactin secretion

The insulin-like growth factor (IGF) autocrine/paracrine system is believed to be involved in endometrial differentiation, but there is limited information on the specific cellular functions regulated by IGFs in uterine tissues and their regulation of IGF-binding proteins (IGFBPs). We have investigated the regulation by insulin, IGF-I, and IGF-II, of IGFBP secretion in human endometrial stromal cells decidualized in vitro, and examined the interrelationship between the induced changes in IGFBP levels and the biological responses of stromal cells to IGFs. IGFBPs in conditioned media were analyzed by Western ligand blotting, and IGFBP-1 was quantified by an immunoenzymometric assay (IEMA). In the absence of peptides, decidualized stromal cells secreted 25.5 +/- 3.2 micrograms/day per 10(6) cells of IGFBP-1. Insulin caused a dose-dependent reduction of IGFBP-1 secretion (half-maximal inhibition at < 1 ng/ml) to a maximum of 1% of control values. Northern analysis using a specific cDNA probe showed the expression in decidualized stromal cells of a single 1.5 kb transcript for IGFBP-1, which was absent in insulin-treated cells. The effects of IGF-I and IGF-II on IGFBP-1 secretion were biphasic, with initial stimulation (200-250%) that peaked at 1 and 10 ng/ml, respectively, followed by inhibition at higher concentrations (half maximal inhibition at 3 ng/ml and 30 ng/ml, respectively). The decrease in IGFBP-1 levels in decidualized stromal cultures was associated with the induction of mitogenesis by IGF-I and IGF-II, while IGF effects on prolactin secretion paralleled those of IGFBP-1 secretion, with stimulation (243-324%) in the low concentration range followed by inhibition at higher concentrations. These data indicate that endometrial stromal cell IGFBP-1 is regulated by insulin, at concentrations that are compatible with insulin acting via its own receptor, while the effects of IGF-I and IGF-II on IGFBP-1 secretion, are suggestive of their acting probably through the type I IGF receptor. The present study describes distinct effects of the IGFs on stromal cell IGFBPs, that correlate with changes in the proliferative and secretory responses of decidualized stromal cells to the IGFs. Our findings suggest that complex IGF-IGFBP interactions may participate in the regulation of endometrial cell function, and support a role for IGF-II in stromal cell mitogenesis during decidualization, and as a local regulator of decidual cell function during the late secretory phase and early pregnancy.

Immunohistochemical localization of the insulinlike growth factor binding protein-1 in female reproductive tissues by monoclonal antibodies

Human insulinlike growth factor binding protein-1 (hlGFBP-1) is a secretory protein that modulates the receptor-binding and biological actions of the insulinlike growth factor I (IGF-I). Human endometrium expresses the mRNA for IGFBP-1, and this protein is secreted by the secretory phase and pregnancy endometrium as well as by ovarian granulosa cells in vitro. In this study, we examined the cellular localization of IGFBP-1 in female reproductive tissues by using a purified monoclonal antibody Mab 6303 with an immunoperoxidase technique. Proliferative- and early secretory-phase endometrium as well as all extrauterine tissues except decidualized cells at the implantation site on the ovaries of ovarian pregnancies were negative for IGFBP-1. In midsecretory-phase endometrium, focal staining was first observed in the cytoplasm of glandular epithelial cells, with weaker staining in the stromal cells. In late secretoryphase endometrium, strong immunostaining was observed in predecidualized stromal cells, with weak focal staining remaining in some of the glandular epithelial cells. In early pregnancy, intense staining was detected in the cytoplasm of decidualized stromal cells of zona compacta in each sample, whereas the nondecidualized stromal cells remained unstained. Strong to medium staining was detected simultaneously in the glandular epithelial cells in 70% of the early pregnancy specimens. In term pregnancy, IGFBP-1 was localized in decidual cells of placental bed and decidua parietalis. Immunolocalization of IGFBP-1 to both endometrial epithelial and stromal cells, although only stromal cells express the gene of IGFBP-1 [14], supports the hypothesis of paracrine actions between these cells. The localization of IGFBP-1 to decidualized cells at the extrauterine implantation sites implies its association with decidual differentiation.

Insulin-like growth factor-II (IGF-II) and IGF binding proteins in human endometrium

The insulin-like growth factor autocrine/paracrine system is believed to play a role in steroid-mediated endometrial differentiation. It is constituted of the mitogenic peptides (IGF-I and IGF-II), membrane receptors, and a family of high-affinity binding proteins (IGFBPs) that regulate the actions of the IGFs at their target cells. We have investigated expression of the mRNAs encoding the three major IGFBPs (IGFBP-1, IGFBP-2, and IGFBP-3) in human endometrium and have found, by Northern analysis, differential expression of all three mRNAs in secretory compared to proliferative endometrium, different steroidal milieux. IGF-II mRNAs were also detected in secretory endometrium. Finally, we found that human endometrial stromal cells in culture synthesize and secrete IGFBP-2 and IGFBP-3, and that the synthesis of IGFBP-2 is regulated by steroid hormones.

Progestins and Antiprogestins: A Review of Their Role in Medicine and Bioassays Used in Their Development

The physiological role of ovarian progesterone in reproduction and the medical uses of synthetic progestins and antiprogestins are briefly reviewed. Although a number of progestins are in wide use, the search continues for better analogues that display fewer of the unwanted effects of the present compounds. The one antiprogestin approved for human use to date, RU486, exhibits considerable antiglucocortoid activity

The classical bioassays currently in use for the development of these steroid analogues depend upon in vivo progestin effects. However, progestins induce measurable responses in several cell culture systems that could be used as alternative bioassays. Rabbit uterine stromal cells in primary culture are especially suitable for such use. Addition of progesterone to these cultures stimulates synthesis of a 42 kilodalton (42kD) protein that appears in the medium. The 42kD protein response is specific for a progesterone receptor-mediated event and it can be blocked by known progestins. Using this culture system as a bioassay, one rabbit yields enough cells to measure the effect of 30 test doses in triplicate. Thus, a culture system is described that could substitute for current in vivo bioassays. This culture bioassay would allow large scale screening for potential progestin or antiprogestin activity.

Secretory proteins of the endometrium--potential markers for endometrial dysfunction

In contrast to our detailed knowledge of endometrial structure, the study of endometrial function is still in its infancy. It seems likely that most of the changes that occur in the endometrium during the cycle are directed towards the promotion of implantation, and that the proteins secreted by the tissue have a role to play in the maintenance of pregnancy. One approach to the study of these proteins has been the incubation of endometrium in vitro with labelled amino acid precursors, and this method has revealed that in early pregnancy two proteins are quantitatively more important than the others synthesized and secreted by the endometrium. One of these proteins is a homologue of beta-lactoglobulin, also known as alpha 2-PEG, PP14 or PEP. It is synthesized by endometrial glands and no other source has been identified. Its synthesis is induced in the luteal phase of the menstrual cycle, rises to a peak in the early weeks of pregnancy and then rapidly declines as the decidua spongiosa is replaced by decidua compacta. The direction of its secretion appears to be into the amniotic fluid, and its function may be to transport a vitamin or other essential substance to the early conceptus: another possible function is immunosuppression. The protein can be measured in peripheral blood and may be useful as a marker of the effect of progesterone-or its lack of effect, as in the inadequate luteal phase. The other quantitatively important endometrial protein is IGF binding protein, which is produced mainly by stromal fibroblasts in the late luteal phase of the cycle. During the cycle the contribution of the endometrium to serum levels of IGF-BP is slight, but in pregnancy, as the amount of decidua compacta increases, levels in peripheral blood rise, with peaks at 18-24 weeks and at 36-40 weeks. The function of the protein may be to protect the mother by inhibiting IGF, or to enable IGF to stimulate the growth of endometrial stroma. Links between this protein and disorders of fetal growth have been suggested. The diversity of the possible functions of these proteins, and the continuing uncertainty over their roles, underline the complexity of endometrial functions.(ABSTRACT TRUNCATED AT 400 WORDS)

Insulin-like growth factor binding proteins from cultured human fibroblasts. Characterization and hormonal regulation

Specific, high affinity insulin-like growth factor (IGF) binding proteins are secreted by human fibroblasts in culture. By multiple criteria, the species of IGF binding proteins produced by human fibroblasts are distinct from the HepG2/amniotic fluid IGF binding protein, but share many characteristics with the growth hormone-dependent IGF binding protein forms predominant in normal adult human plasma. Treatment of cultured human fibroblasts with growth hormone produced an increase in IGF binding protein activity in the medium, while addition of glucocorticoids markedly diminished IGF binding activity. Insulin, epidermal growth factor, platelet-derived growth factor, and progesterone had no effect on IGF binding activity in fibroblast media. In comparison, HepG2 IGF binding activity was enhanced by progesterone, decreased by insulin, and unaffected by growth hormone or glucocorticoid treatment. Five molecular forms of IGF binding proteins were identified by Western ligand blots in human fibroblast conditioned medium, with Mr = 41,500, 37,000, 32,000, 28,000, and 23,000. In human fibroblast conditioned medium, the Mr = 41,500 and 37,000 IGF binding protein species were abundant, as in normal human plasma, with a major Mr = 23,000 form which was a minor component in plasma.

Two fetal antigens (FA-1 and FA-2) and endometrial proteins (PP12 and PP14) isolated from amniotic fluid: localisation in the fetus and adult female genital tract

Monospecific antisera against two fetal antigens (FA-1 and FA-2), alphafetoprotein (AFP) and two endometrial proteins (PP12 and PP14) were used to examine the distribution of these proteins and antigens in human trophoblast and gestational endometrium in first and third trimesters of pregnancy, normal human ovary and fetal tissues by indirect immunoperoxidase histochemical localisation techniques. Fetal liver stained exclusively for FA-1 and AFP which was used as a reference protein. Staining for FA-2 was seen in fetal connective tissue, in particular the basement membrane. FA-1 and FA-2 did not stain positively in decidua, trophoblast or ovarian tissue. Gestational endometrium stained positively for PP14 exclusively in the glandular epithelium, whilst staining for PP12 was seen only in the stromal cells. Trophoblast, both early and late, and ovarian tissue did not stain positively for any of the four substances tested.

Primary structure of human insulin-like growth factor-binding protein/placental protein 12 and tissue-specific expression of its mRNA

The low-molecular-mass insulin-like growth factor-binding protein (IGF-BP) and placental protein 12 (PP12) are identical proteins that are present in human serum, amniotic fluid, secretory endometrium and decidua. IGF-BP/PP12 is believed to act as an autocrine or paracrine regulator of cell growth. A cDNA clone encompassing the entire protein coding region of this protein was isolated from a human decidual cDNA library. The authenticity of the cDNA was verified by in vitro transcription/translation experiments and by the identity of the 10 N-terminal amino acids deduced for the mature peptide with those obtained by direct protein sequencing. The amino acid sequence indicates that pre-IGF-BP/PP12 consists of 259 amino acid residues. The putative signal peptide is 25 residues long, and the mature protein thus contains 234 amino acids and has a molecular mass of 25293 Da. The sequence is very cysteine-rich at the N-terminus after which there are regions of clustered Pro, Glu, Ser and Thr residues (so-called PEST regions), which exist in proteins with short half-lives. The amino acid sequence also includes an Arg-Gly-Asp tripeptide that may function as a cell recognition signal. The IGF-BP/PP12 gene encodes a single 1.6 kb mRNA species that is expressed in decidua, secretory endometrium, liver and a human hepatoma cell line (HepG2). Southern blot analysis suggests that there is a single IGF-BP/PP12 gene in the human genome.

Serum PP12, PP14, SP1 and hCG values in the 28 days after the LH-surge in patients who do and do not conceive after artificial insemination or in vitro fertilization

Serum levels of PP12 (somatomedin binding protein), PP14 (beta lactoglobulin homologue), Schwangerschaftsprotein 1 (SP1) and of human chorionic gonadotropin (hCG) were simultaneously measured in patients being treated for infertility in the 28 days after the LH-surge. PP14 levels were similar in the 14 days after the LH-surge in the patients who conceived when compared with those who did not and a high PP14 level was only indicative of pregnancy at 21 days after the LH-surge. hCG and SP1 levels behaved similarly in pregnant subjects. PP12 levels did not change significantly in the 28-days after the LH-surge.

The effect of estradiol valerate and allylestrenol on endometrial transformation in hypergonadotropic hypogonadic women

The effect of estradiol valerate and allylestrenol on the endometrial transformation of five hypergonadotropic hypogonadic women was evaluated. Estradiol valerate was administered throughout the whole induced cycle (28 days), while allylestrenol was added during the second half of the cycle. Endometrial biopsies were performed during allylestrenol treatment and were evaluated histologically. Samples of endometrium were also subjected to one-dimensional SDS electrophoresis. Of ten biopsies performed, only one was interpreted to be in-phase, while the others were dated proliferative (4 biopsies) or showed abortive or out-of-phase secretory transformation. The highest mean serum progesterone level, detected under allylestrenol treatment, was 1.5 ng/ml. Protein electrophoresis demonstrated relative sequential changes in the protein patterns of the 115 kDa and 150 kDa protein bands. It is concluded that allylestrenol, although having gestagen properties, may not be efficient for the induction of an adequate secretory transformation of human endometrium in the absence of ovaries.

Human endometrium and menstrual fluid contain placental protein 10 (PP10)

Placental protein 10 (PP10), a newly isolated protein from the human placenta, was detected by radioimmunoassay in 10 out of 23 extracts of proliferative and secretory endometrium and in all of the 20 menstrual fluids examined. The concentrations were higher in the secretory phase, when the tissue PP10 content ranged from less than 0.2 to 1.3 microgram/g of endometrial cytosol protein. In menstrual fluid, PP10 was found at concentrations of 16 to 270 micrograms/l. In RIA, the dose-response curves of endometrial, menstrual fluid and purified PP10 were parallel. In gel filtration, the major part of PP10 from the endometrium and menstrual fluid eluted in the same fraction as purified placental PP10. Our results add another placental protein to the list of placental proteins which also appear in the endometrium.

Progesterone-associated proteins PP12 and PP14 in the human endometrium

Two proteins, designated as PP12 and PP14 were originally isolated from soluble extracts of the human placenta and its adjacent membranes. We have shown that they are synthesized by decidualized/secretory endometrium and not by placenta. Both proteins occur at high concentrations in human amniotic fluid, which is therefore an excellent source for purification. PP12 is a 34-kDa glycoprotein, which has an N-terminal amino acid sequence of Ala-Pro-Trp-Gln-Cys-Ala-Pro-Cys-Ser-Ala. This is identical with that of somatomedin-binding protein purified from the amniotic fluid. PP12 too binds somatomedin-C, or IGF-I (insulin-like growth factor-I). Human secretory endometrium synthesizes and secretes PP12, and progesterone stimulates its secretion. PP14 is a 28-kDa glycoprotein. Its N-terminal sequence shows homology to that of beta-lactoglobulins from various species. We have found PP14 in the human endometrium, serum and milk. Immunologically, PP14 is related to progestagen-associated endometrial protein (PEP), alpha-2 pregnancy-associated endometrial protein (alpha-2, PEG), endometrial protein 15 (EP15), alpha-uterine protein (AUP) and chorionic alpha-2 microglobulin (CAG-2). In ovulatory menstrual cycles, the concentration of PP14 increases in endometrial tissue as the secretory changes advance. In serum, the PP14 concentration begins to rise later than the progesterone levels, and high serum PP14 levels are maintained for the first days of the next cycle. By contrast, no elevation of serum PP14 level is seen in anovulatory cycles. Our results show that progesterone-associated proteins are synthesized by the human endometrium and appear in the peripheral circulation, where they can be quantitatively measured using immunochemical techniques.

Elevated levels of a somatomedin-binding protein PP12 in patients with ovarian cancer

The circulating levels of placental protein 12 (PP12), a somatomedin-binding protein, were measured by radioimmunoassay in 37 postmenopausal women with ovarian tumors. Elevated levels (above 47 micrograms/l) were observed in 16 of 25 patients (64%) with malignant and 2 of 12 patients (17%) with benign tumors. Elevated levels were more frequent and higher in patients with advanced disease. Within 1 week of surgery, the levels fell in 13 of 17 cases (77%). In addition to clinical interest, these results contribute to our knowledge of carrier proteins of growth factors in patients bearing malignant ovarian neoplasms.

New placental proteins: chemistry, physiology and clinical use

In the past decade, several new placental proteins have been isolated and studied. The 'pregnancy-specific' beta 1-glycoprotein (SP1) is a major placental product with unusual physicochemical properties that has been extensively investigated, but its biological function remains uncertain. Pregnancy-associated plasma protein A (PAPP-A), a glycoprotein of mol. wt 400,000, has effects in vitro on the coagulation and complement cascades, probably by its properties of protease inhibition. Placental protein 5 (PP5) may be involved in the coagulation and fibrinolytic systems, and in follicle maturation and semen liquefaction. 'Placental protein 12' (PP12) is not a product of the placenta at all; it appears to be produced in the female genital tract under the influence of progesterone and may also be produced by proliferating liver cells. Further study may reveal new roles for these placental proteins beyond their traditional roles as tumour markers.

The content and immunohistochemical localization of placental protein 10 (PP10) in the fallopian tube

Radioimmunoassay, gel filtration and immunoperoxidase staining were used to study the content and localization of placental protein 10 (PP10) in 15 fallopian tubes removed on medical grounds from patients aged between 35 and 53 years. PP10 was consistently present in all parts of the tube at all ages and in all phases of the menstrual cycle. The PP10 concentration in tissue ranged from 0.08 to 2.95 micrograms/g of tubal cytosol protein. Immunoperoxidase staining localized PP10 in monocytic and lymphoid cells that were unevenly scattered in the subepithelial layer of the mucosa. In gel filtration, PP10 from the fallopian tube and purified placental PP10 eluted in the same volume, and graded amounts of PP10-immunoreactive material from the tube and purified PP10 gave parallel dose-response curves in radioimmunoassay. We conclude that PP10 is another 'placental protein' that has been identified in the fallopian tube.

Endogenous opioid peptides in uterine fluid

The present study demonstrates the presence of the endogenous opioid peptides beta-endorphin (beta-EP) and methionine-enkephalin (MET-ENK), in the uterine fluid of fertile women and normally cycling and superovulated cows. The two peptides are undetectable in the uterine fluid of untreated postmenopausal women, whereas they are present following estrogen-progesterone treatment. Immunoreactive (IR) MET-ENK concentrations were higher in the secretory than in the proliferative phase of the menstrual cycle. IR beta-EP and IR MET-ENK are present also in the follicular, oviductal, and uterine fluid of cows, and in the uterine fluid, concentrations of IR MET-ENK are higher in the superovulated than in the control animals. Because opioids play important roles on endocrine and immune functions, the present data support the potential physiologic role of endometrial secretions.

Human fallopian tube contains placental protein 14

Radioimmunoassay and immunoperoxidase staining were used to study the tissue content and localization of an endometrial protein, placental protein 14, in the human fallopian tube. Placental protein 14 immunoreactivity was found in saline extracts from all fallopian tubes tested (n = 14). In the fimbrial part the placental protein 14 content was higher in the secretory than in the proliferative phase (p less than 0.01). No difference was found in the placental protein 14 content between the isthmic, ampullar, and fimbrial parts of the tube. Immunoperoxidase staining localized placental protein 14 to the ciliated and secretory epithelial cells of the mucosa in all parts of the tube regardless of the phase of menstrual cycle. The occurrence of the same protein in the endometrium and fallopian tube is compatible with the common embryonic origin from the müllerian duct of these tissues.

Pregnancy proteins in seminal plasma, seminal vesicles, preovulatory follicular fluid, and ovary

A number of proteins previously thought to be specific for the placenta or pregnancy have been identified in the fluids bathing both the oocyte and the sperm. In many cases their concentrations in follicular fluid and seminal plasma greatly exceeded those in the serum of nonpregnant women or men, and sometimes they even exceeded the levels in pregnancy sera. We report here the occurrence of PP5, PP12, PP14 and PAPP-A in follicular fluid and seminal plasma. In follicular fluid, the levels of PP5, PP12, and PAPP-A correlate with the estrogen concentration of the same fluid, and the PP12 and PAPP-A levels also bear a positive correlation to the progesterone concentration. The levels of PP12 and PAPP-A increase as the follicle grows, as do the levels of many steroid hormones. Therefore, the apparent correlations observed may be merely coincidental. However, circumstantial evidence from other reproductive organs indicates that the synthesis of PP12 and PAPP-A is stimulated by progesterone. Results of immunohistochemical staining show that PP12 and PAPP-A are localized in the luteinized granulosa cells and the corpus luteum. Previous studies indicate that PP5 and PAPP-A inhibit the action of proteolytic enzymes plasmin and elastase, which are believed to be involved in the mechanisms of ovulation. The study of the significance of these various placental proteins for human reproduction is only at its beginning. Clearly, elucidation of their function is the key to a more fundamental understanding of their role in the events governing ovulation and implantation.

Pregnancy proteins in the endometrium after follicle aspiration for in vitro fertilization

Placental proteins PP10, PP12, and PP14 and pregnancy-associated plasma protein A (PAPP-A) and relaxin (RX) were studied by the immunoperoxidase method in the uterine mucosa at the time of embryo replacement in 18 women for whom no embryo was available to be replaced. All subjects had received 17 alpha-hydroxyprogesterone caproate at the time of follicle aspiration, which had been performed 36 hours after preovulatory administration of hCG. The time between follicle aspiration and endometrial biopsy varied from 26 to 216 hours. PP10 was not detected in any specimen. RX was found in 17 of 18, PP12 in 15 of 18, PAPP-A in 14 of 18, and PP14 in 6 of 18 specimens. In a normal cycle, PP12, PAPP-A and RX appear in the endometrium on the fourth day post ovulation. In the conditions described above the same proteins could be seen in the endometrium sooner after oocyte retrieval. This may be due to a strong progesterone effect after multiple follicle aspirations and treatment with 17 alpha-hydroxyprogesterone. The significance of the occurrence of these pregnancy proteins as well as that of the morphologic and biochemical maturity of the endometrium at the time of embryo transfer are discussed.

Immunoreactive beta-endorphin is demonstrable in the secretory but not in the proliferative endometrium

The presence of immunoreactive beta-endorphin (ir beta-E) in the endometrium was studied by immunoperoxidase staining of tissue sections at various stages of the menstrual cycle. Ir beta-E was found in the endometrium during the secretory phase of the cycle, from the fourth postovulatory day to the desquamating phase, but not in the proliferative phase or during the first three postovulatory days of the cycle. Ir beta-E was located in the cytoplasm of the epithelial cells of the glands. Samples of endometrium were homogenized, and peptides were extracted with Sep Pak C18 cartridge, followed by purification of ir beta-E by cation-exchange high-pressure liquid chromatography. In samples of secretory endometrium, a peak of ir beta-E was found with identical location of that of reference beta-E. The concentration of ir beta-E in the secretory endometrium varied from 5.0 to 12.6 pg/g of tissue. The appearance of ir beta-E in the endometrium during the secretory phase may have importance in the early events of reproduction.