Developmental and hormonal regulated gene expression of fibroblast growth factor 2 (FGF-2) and its receptors in porcine endometrium

Chemerin affects the expression of angiogenesis-related factors in the porcine endometrium during early pregnancy and the oestrous cycle: an in vitro study

CONTEXT

The appropriate course of angiogenesis in the endometrium is crucial for pregnancy establishment and maintenance. Very little is known about the factors linking vessel formation and immune system functioning.

AIMS

We hypothesised that chemerin, an adipokine known for its involvement in the regulation of energy balance and immunological functions, may act as a potent regulator of endometrial angiogenesis during early pregnancy in pigs.

METHODS

Porcine endometrial tissue explants were obtained from pregnant pigs on days 10-11, 12-13, 15-16 and 27-28, and on days 10-12 of the oestrous cycle. The explants were in vitro cultured for 24h in the presence of chemerin (100, 200ng/mL) or in medium alone (control). We evaluated the in vitro effect of chemerin on the secretion of vascular endothelial growth factors A-D (VEGF-A-D), placental growth factor (PlGF), basic fibroblast growth factor (bFGF) and angiopoietin 1 and 2 (ANG-1, ANG-2) with the ELISA method. The protein abundance of angiogenesis-related factor receptors, VEGF receptors 1-3 (VEGFR1-3), FGF receptors 1 and 2 (FGFR1-2) and ANG receptor (TIE2) was evaluated with the Western blot (WB) method. We also analysed the influence of chemerin on the phosphorylation of AMPK using WB.

KEY RESULTS

We found that in the studied endometrial samples, chemerin up-regulated the secretion of VEGF-A, VEGF-B and PlGF, and protein expression of VEGFR3. The adipokine caused a decrease in VEGF-C, VEGF-D and ANG-1 release. Chemerin effect on bFGF and ANG-2 secretion, and protein content of VEGFR1, VEGFR2, FGFR1, FGFR2 and TIE2 were dependent on the stage of pregnancy. Chemerin was found to down-regulate AMPK phosphorylation.

CONCLUSIONS

The obtained in vitro results suggest that chemerin could be an important factor in the early pregnant uterus by its influence on angiogenic factors' secretion and signalling.

IMPLICATIONS

The obtained results on the role of chemerin in the process of endometrial angiogenesis may, in the long term perspective, contribute to the elaboration of more effective methods of modifying reproductive processes and maintaining energy homeostasis in farm animals.

Impaired luteal progesterone synthesis observed in gilts with PMSG/hCG-induced estrus affects the expression of steroid, prostaglandin, and cytokine receptors in the endometrium and myometrium during the peri-implantation period

The present study aimed to examine the effect of impaired progesterone (P4) synthesis, observed in gilts with gonadotropin-induced estrus, on the uterine expression of receptors important for pregnancy establishment. Twenty prepubertal gilts received 750 IU PMSG and 500 IU hCG 72 h later, while 18 prepubertal gilts in the control group were observed daily for estrus behavior. Gilts were inseminated in their first estrus and slaughtered on days 10, 12, and 15 of pregnancy to collect endometrial and myometrial tissues for mRNA analysis using real-time PCR. As we previously described, gilts with PMSG/hCG-induced estrus showed decreased luteal P4 synthesis on days 10 and 12 of pregnancy. PMSG/hCG treatment did not affect P4 receptor mRNA expression in either uterine tissue. In the endometrium, a greater mRNA transcript abundance of estrogen receptors (ESR1 and ESR2), androgen receptor (AR), prostaglandin (PG) E2 receptors (PTGER2 and PTGER4), PGF2α receptor (PTGFR), interleukin 6 receptor (IL6R), and tumor necrosis factor α receptors (TNFRSF1A and TNFRSF1B) was detected in gilts with natural than with PMSG/hCG-induced estrus (P<0.05). In the myometrium, the mRNA expression of AR, PTGER2, and PTGFR was lower, while PGI2 receptor (PTGIR) transcript abundance was elevated in the gilts treated with PMSG/hCG as compared with the control animals (P<0.05). In summary, a decreased luteal P4 level during the peri-implantation period in gonadotropin-stimulated pigs affects endometrial and myometrial receptor expression, with the endometrium being more sensitive to impaired P4 synthesis. Whether the observed changes alter uterine receptivity to local and systemic factors remains to be elucidated.

Vascular Distribution and Expression Patterns of Angiogenic Factors in Caruncle during the Early Stage of Pregnancy in Goats (Capra hircus)

The placenta is a temporary maternal−fetal organ, and its maternal placenta (caruncle) is essential for fetal growth and development. The exchange function of the placenta requires vascular development (angiogenesis). However, the angiogenesis of the caruncle is poorly understood in goats during the early stage of pregnancy. Here, we investigated the vascular distribution, mRNA expression of major angiogenic factors, and the methylation levels of ANGPT2 in the goat caruncle. It showed that CAD (capillary area density), CSD (capillary surface density), and APC (area per capillary) increased gradually, while CND (capillary number density) showed an insignificant change, probably due to the variability between animals. The proportion of proliferating cells was observed to be very high (>26%) and increased (p < 0.002) approximately 2-fold from day 20 to 60 of pregnancy. Furthermore, the expression patterns of major angiogenic factors changed during the early stage of pregnancy. Interestingly, we discovered an absolute correlation between the mRNA for ANGPT2, TEK, FGF2, and vascular distribution. Subsequently, we evaluated the DNA methylation of ANGPT2, where we found that mean methylation was negatively correlated with CAD. The methylation at the CpG sites, such as CpG 4/18, CpG 9.10.11, and CpG 15, showed significant changes during the early stage of pregnancy. Thus, our findings suggest that the methylation of ANGPT2 may be involved in the regulation of caruncle angiogenesis during the early stage of pregnancy.

Single-Cell Transcriptomics of Proliferative Phase Endometrium: Systems Analysis of Cell–Cell Communication Network Using CellChat

The endometrium thickness increases by which endometrial angiogenesis occurs in parallel with the rapid growth of endometrium during the proliferative phase, which is orchestrated by complex cell–cell interactions and cytokine networks. However, the intercellular communication has not been fully delineated. In the present work, we studied the cell–cell interactome among cells of human proliferative phase endometrium using single-cell transcriptomics. The transcriptomes of 33,240 primary endometrial cells were profiled at single-cell resolution. CellChat was used to infer the cell–cell interactome by assessing the gene expression of receptor–ligand pairs across cell types. In total, nine cell types and 88 functionally related signaling pathways were found. Among them, growth factors and angiogenic factor signaling pathways, including EGF, FGF, IGF, PDGF, TGFb, VEGF, ANGPT, and ANGPTL that are highly associated with endometrial growth, were further analyzed and verified. The results showed that stromal cells and proliferating stromal cells represented cell–cell interaction hubs with a large number of EGF, PDGF incoming signals, and FGF outgoing signals. Endothelial cells exhibited cell–cell interaction hubs with a plenty of VEGF, TGFb incoming signals, and ANGPT outgoing signals. Unciliated epithelial cells, ciliated epithelial cells, and macrophages exhibited cell–cell interaction hubs with substantial EGF outgoing signals. Ciliated epithelial cells represented cell–cell interaction hubs with a large number of IGF and TGFb incoming signals. Smooth muscle cells represented lots of PDGF incoming signals and ANGPT and ANGPTL outgoing signals. This study deconvoluted complex intercellular communications at the single-cell level and predicted meaningful biological discoveries, which deepened the understanding of communications among endometrial cells.

Semen Modulates Cell Proliferation and Differentiation-Related Transcripts in the Pig Peri-Ovulatory Endometrium

Simple Summary

Homeostasis of the uterus after mating is crucial for the subsequent reproductive events. The post-mating inflammatory response is restricted to the uterus, but semen also modulates the expression of other genes involved in regulation along the female reproductive tract, including the oviduct. This study aims to determine if several ejaculate fractions of the pig may modulate cell proliferation and differentiation-related transcripts in different sections of the peri-ovulatory sow reproductive tract. Our data demonstrate that most of the mRNA expression changes of the 144 transcripts tested were induced by mating. Additionally, spermatozoa and seminal plasma also triggered differential expression of the transcripts tested. Finally, our data imply that spermatozoa, seminal plasma components, and the act of mating induce differential mechanisms in the peri-ovulatory female reproductive tract, which are essential for tissue repair.

Abstract

Uterine homeostasis is maintained after mating by eliminating pathogens, foreign cells, and proteins by a transient inflammation of the uterus. Such inflammation does not occur in the oviductal sperm reservoir (utero-tubal junction, UTJ), colonized by a population of potentially fertile spermatozoa before the inflammatory changes are triggered. Semen entry (spermatozoa and/or seminal plasma) modifies the expression of regulatory genes, including cell proliferation and differentiation-related transcripts. Considering pigs display a fractionated ejaculation, this study aims to determine whether different ejaculate fractions differentially modulate cell proliferation and differentiation-related transcripts in the sow reproductive tract during the peri-ovulatory stage. Using species-specific microarray analyses, the differential expression of 144 cell proliferation and differentiation-related transcripts was studied in specific segments: cervix (Cvx), distal and proximal uterus (DistUt, ProxUt), UTJ, isthmus (Isth), ampulla (Amp), and infundibulum (Inf) of the peri-ovulatory sow reproductive tract in response to semen and/or seminal plasma cervical deposition. Most mRNA expression changes were induced by mating. In addition, while mating upregulates the fibroblast growth factor 1 (FGF1, p-value DistUt = 0.0007; ProxUt = 0.0253) transcript in the endometrium, both its receptor, the fibroblast growth factor receptor 1 (FGFR1, p-value DistUt = 2.14 e⁻⁰⁶; ProxUt = 0.0027; UTJ = 0.0458) transcript, and a potentiator of its biological effect, the fibroblast growth factor binding protein 1 (FGFBP1), were downregulated in the endometrium (p-value DistUt = 0.0068; ProxUt = 0.0011) and the UTJ (p-value UTJ = 0.0191). The FGFBP1 was downregulated in the whole oviduct after seminal depositions (p-value Isth = 0.0007; Amp = 0.0007; Inf = 6.87 e⁻⁰⁵) and, interestingly, FGFR1 was downregulated in the endometrium in the absence of semen (p-value DistUt = 0.0097; ProxUt = 0.0456). In conclusion, the findings suggest that spermatozoa, seminal components, and the act of mating trigger, besides inflammation, differential mechanisms in the peri-ovulatory female reproductive tract, relevant for tissue repair.

Adiponectin Influences FGF2 in the Developing Porcine Corpus Luteum

Luteal angiogenesis is regulated by pro-angiogenic hormones including fibroblast growth factor 2 (FGF2) and angiopoietin 1 (Ang1), which are regulated by the adipokine leptin during development. Another adipokine, adiponectin, exhibits an inverse relationship with leptin and has been identified in the CL. Therefore, it is hypothesized that adiponectin will influence pro-angiogenic hormones in the developing porcine CL. Crossbred sows were randomly allocated to one of two days of the estrous cycle, day 5 (D5; n = 4) or day 7 (D7; n = 5) for CL collection. Tissue was processed for immunohistochemical localization of adiponectin receptor 2 (AdipoR2), gene expression of FGF2, Ang1, leptin, AdipoR2, and cell culture for adiponectin treatment. The expression of AdipoR2 tended (p = 0.09) to be higher in D7 lutea and was more prevalently localized to the cell surface of large and small luteal cells than in D5 tissue. Adiponectin influenced (p ≤ 0.05) FGF2, leptin, and AdipoR2 gene expression relative to the dose and day (D5 or D7). Collectively, the evidence supports the supposition that adiponectin influences angiogenic factors in the developing CL.

Prostaglandin E receptor 2 mediates the inducible effects of prostaglandin E2 on expression of growth factors and enzymes in cattle endometrial epithelial cells and explants

Prostaglandin E₂ (PGE₂ ) is able to induce the expression of several growth factors and enzymes in cattle endometria. However, the specific type of PGE₂ receptors which mediates this effect is not fully clear. In this study, the role of prostaglandin E receptor 2 (PTGER2) in PGE₂ -mediated induction of growth factors and enzymes expression in cattle endometrial explants and epithelial cells were investigated. PTGER2 was blocked by a PTGER2 antagonist, AH6809, before PGE₂ treatment, then the mRNA and protein expression levels of several growth factors and enzymes were compared with that in PGE₂ alone treatment group by real-time RT-PCR and Western blotting analysis in endometrial epithelial cells and explants. Results indicated that PGE₂ significantly increased the mRNA and protein levels of these growth factors and enzymes, while the rates of increment in the expression of these growth factors and enzymes were inhibited by AH6809. In addition, a PTGER2 agonist, butaprost, significantly increased the expression levels of these growth factors and enzymes, and the effect could be blocked by AH6809. In conclusion, PTGER2 was found to be one dominant receptor mediating the inducible effects of PGE₂ on the expression of these growth factors and enzymes in cattle endometrial explants and epithelial cells.

The distribution and immunolocalization of fibroblast growth factors (FGFs) in the rat oviduct during early pregnancy and the post-partum period

The mammalian oviduct provides a favourable environment for several reproductive processes, including ovum transport, sperm capacitation, fertilization and pre-implantation embryonic development. This environment is regulated by cyclic ovarian steroids, that is oestrogen, and growth factors. Fibroblast growth factors (FGFs) regulate the differentiation and growth of various cell types in the female genital tract. This study aimed to determine the localization of FGF1, FGF2, FGF receptor 1 (FGFR1) and 2 (FGFR2) in the rat oviduct, by immunohistochemistry, on day 5 of pregnancy and post-partum days 1, 3 and 5, and to demonstrate the possible functions of these proteins during early pregnancy and the post-partum period. On all examination days, cytoplasmic and nuclear FGF1 immunoreactivity was detected in the epithelium lining the infundibulum, ampulla and isthmus of the oviduct. Immunoreactivity was much stronger in the basal bodies of the cilia on the epithelium lining the infundibulum and ampulla. FGF1 immunoreactivity was also detected in stromal cells, myocytes and endothelial cells. Cytoplasmic FGF2 immunoreactivity was observed in the tunica muscularis, vascular myocytes and endothelial cells. While strong cytoplasmic FGF2 immunoreactions were observed in the stromal cells of the lamina propria, the luminal epithelium, some stromal cells and smooth muscle cells displayed a rather weak FGFR1 and FGFR2 immunoreactivity. Immunoreaction intensity did not differ between the periods examined. This study shows that FGF1, FGF2, FGFR1 and FGFR2 are produced by rat oviduct cells during pregnancy and the post-partum period, and reproductive physiology is regulated not only by hormonal mechanisms, but also by growth factors.

Selective sweep analysis reveals extensive parallel selection traits between large white and Duroc pigs

In the process of pig genetic improvement, different commercial breeds have been bred for the same purpose, improving meat production. Most of the economic traits, such as growth and fertility, have been selected similarly despite the discrepant selection pressure, which is known as parallel selection. Here, 28 whole-genome sequencing data of Danish large white pigs with an approximately 25-fold depth each were generated, resulting in about 12 million high-quality SNPs for each individual. Combined with the sequencing data of 27 Duroc and 23 European wild boars, we investigated the parallel selection of Danish large white and Duroc pigs using two complementary methods, Fst and iHS. In total, 67 candidate regions were identified as the signatures of parallel selection. The genes in candidate regions of parallel selection were mainly associated with sensory perception, growth rate, and body size. Further functional annotation suggested that the striking consistency of the terms may be caused by the polygenetic basis of quantitative traits, and revealing the complex genetic basis of parallel selection. Besides, some unique terms were enriched in population-specific selection regions, such as the limb development-related terms enriched in Duroc-specific selection regions, suggesting unique selections of breed-specific selected traits. These results will help us better understand the parallel selection process of different breeds. Moreover, we identified several potential causal SNPs that may contribute to the pig genetic breeding process.

Pleiotropic role of prokineticin 1 in the porcine endometrium during pregnancy establishment and embryo implantation †

Acquisition of endometrial receptivity for embryo implantation is one of the crucial processes during pregnancy and is induced mainly by progesterone and enhanced by conceptus signals. Prokineticin 1 (PROK1) is characterized as a secretory protein with diverse functions in various tissues, including the reproductive tract. PROK1, with its receptor PROKR1, are up-regulated in the porcine endometrium during implantation and in women's receptive endometrium and decidua. However, the function of PROK1 in embryo-maternal communication has still not been fully elucidated. Hence, we hypothesize that PROK1 is involved in endometrial receptivity development and implantation in pigs. In this study, using the porcine in vivo model of intrauterine infusions of estradiol-17β (E2) and prostaglandin E2 (PGE2), we revealed that these hormones elevated endometrial expression of PROK1 and PROKR1 mRNA, respectively. Moreover, E2, acting synergistically with PGE2, increased PROKR1 protein expression. We also evidenced that PROK1-PROKR1 signaling induced expression of following genes and/or proteins CCN2, CDH13, FGF2, NFATC2, ANGPT1, ANGPT2, CDH1, MUC4, SPP1, IFNG, IL6, LIF, LIFR, TNF, TGFB3, and FGF9, as well as phosphorylation of PTK2 and secretion of IL6 and IL11 by endometrial explants in vitro. Ingenuity pathway analysis revealed that functions associated with the PROK1-regulated genes/proteins include cell-to-cell contact, cell attachment, migration and viability, differentiation of epithelial tissue, leukocyte migration, inflammatory response, angiogenesis, and vasculogenesis. Summarizing, our study suggests that PROK1 acts pleiotropically as an embryonic signal mediator that regulates endometrial receptivity by increasing the expression of the genes and proteins involved in implantation and pregnancy establishment in pigs.

In vivo response of the corpus luteum to progesterone treatment of gilts during early gestation

Supplementation of progesterone (P₄) in pregnant gilts increases concentrations of circulating P₄ and stimulates the secretory activity of the endometrium. In this study, there was examination of the consequences of exogenous P₄ administration on luteal P₄ content and the expression of genes related to the corpus luteum (CL) function. Gilts with gonadotropin-induced estrus were administered daily injections of corn oil (n = 8) or P₄ (n = 8) on days 3 through 10 after insemination. The animals were slaughtered on day 12 of pregnancy to obtain corpora lutea for real-time polymerase chain reaction analyses of selected genes and for enzyme immunoassay of P₄. Injections with P₄ had no effect on the concentration of P₄ and the relative abundance of mRNA transcripts of cholesterol transport-related proteins, steroidogenic enzymes, and receptors for luteotropic factors in the luteal tissue. The abundance of prostaglandin (PG) endoperoxide synthase 2, PGI2 synthase, PGI2 receptor, fibroblast growth factor 2, peroxisome proliferator-activated receptor γ, and tumor necrosis factor α receptor type I transcripts increased after P₄ treatment. In contrast, the relative abundance of angiopoietin 2 mRNA decreased in response to P₄ administration. In summary, P₄ supplementation in pregnant gilts does not affect luteal steroidogenesis but modulates the abundance of factors related to vascular function. Given that the endometrium is the main target tissue for P₄, an indirect uterine-mediated effect of exogenous P₄ on CL function is likely.

Prokineticin 1-prokineticin receptor 1 signaling promotes angiogenesis in the porcine endometrium during pregnancy†

Pregnancy establishment in mammals, including pigs, requires proper communication between embryos and the maternal reproductive tract. Prokineticin 1 (PROK1) has been described as a secretory protein with pleiotropic functions and as a novel tissue-specific angiogenic factor. However, despite the studies performed mainly on human cell lines and in mice, the function of PROK1 in the endometrium during early pregnancy is still not fully elucidated. We hypothesized that PROK1 contributes to pregnancy establishment in pigs. The present study is the first to report that the expression of PROK1 and its receptor (PROKR1) is elevated in the porcine endometrium during the implantation and early placentation period. PROK1 protein was detected mainly in luminal epithelial cells, glandular epithelial cells, and blood vessels in the endometrium. Using the porcine in vivo model of unilateral pregnancy, we revealed that conceptuses induced the endometrial expression of PROK1 and PROKR1. Moreover, the embryonic signal, estradiol-17β, as well as progesterone, stimulated the endometrial expression of PROK1 and PROKR1. We also evidenced that PROK1-PROKR1 signaling supports endometrial angiogenesis in pigs. The PROK1-stimulated proliferation of primary porcine endometrial endothelial (PEE) cells involved PI3K/AKT/mTOR, MAPK, cAMP, and NFKB signaling pathways. Furthermore, PROK1 via PROKR1 promoted the formation of capillary-like structures by PEE cells. PROK1 also stimulated VEGFA and PGF2α secretion, which in turn may indirectly support angiogenic changes within endometrial tissue. In summary, our study suggests that PROK1 acts as an embryonic signal mediator that regulates endometrial angiogenesis and secretory function during the implantation and early placentation period in pigs.

Clinical Management of Congenital Hypogonadotropic Hypogonadism

The initiation and maintenance of reproductive capacity in humans is dependent on pulsatile secretion of the hypothalamic hormone GnRH. Congenital hypogonadotropic hypogonadism (CHH) is a rare disorder that results from the failure of the normal episodic GnRH secretion, leading to delayed puberty and infertility. CHH can be associated with an absent sense of smell, also termed Kallmann syndrome, or with other anomalies. CHH is characterized by rich genetic heterogeneity, with mutations in >30 genes identified to date acting either alone or in combination. CHH can be challenging to diagnose, particularly in early adolescence where the clinical picture mirrors that of constitutional delay of growth and puberty. Timely diagnosis and treatment will induce puberty, leading to improved sexual, bone, metabolic, and psychological health. In most cases, patients require lifelong treatment, yet a notable portion of male patients (∼10% to 20%) exhibit a spontaneous recovery of their reproductive function. Finally, fertility can be induced with pulsatile GnRH treatment or gonadotropin regimens in most patients. In summary, this review is a comprehensive synthesis of the current literature available regarding the diagnosis, patient management, and genetic foundations of CHH relative to normal reproductive development.

The fibroblast growth factor 8 family in the female reproductive tract

Several growth factor families have been shown to be involved in the function of the female reproductive tract. One subfamily of the fibroblast growth factor (FGF) superfamily, namely the FGF8 subfamily (including FGF17 and FGF18), has become important as Fgf8 has been described as an oocyte-derived factor essential for glycolysis in mouse cumulus cells and aberrant expression ofFGF18has been described in ovarian and endometrial cancers. In this review, we describe the pattern of expression of these factors in normal ovaries and uteri in rodents, ruminants and humans, as well as the expression of their receptors and intracellular negative feedback regulators. Expression of these molecules in gynaecological cancers is also reviewed. The role of FGF8 and FGF18 in ovarian and uterine function is described, and potential differences between rodents and ruminants have been highlighted especially with respect to FGF18 signalling within the ovarian follicle. Finally, we identify major questions about the reproductive biology of FGFs that remain to be answered, including (1) the physiological concentrations within the ovary and uterus, (2) which cell types within the endometrial stroma and theca layer express FGFs and (3) which receptors are activated by FGF8 subfamily members in reproductive tissues.

Stimulatory effects of fibroblast growth factor 2 on proliferation and migration of uterine luminal epithelial cells during early pregnancy

Fibroblast growth factor 2 (FGF2) is a mitogen that induces proliferation, differentiation, and migration of cells, as well as angiogenesis and carcinogenesis via autocrine or paracrine actions. Fibroblast growth factor 2 expression is abundant in porcine conceptuses and endometrium during the estrous cycle and peri-implantation period of pregnancy. However, its intracellular actions in uterine epithelial cells have not been reported. The results of this study indicated abundant expression of FGFR1 and FGFR2 predominantly in uterine luminal and glandular epithelia during early pregnancy and that their expression decreased with increasing parity of the sows. Treatment of porcine uterine luminal epithelial (pLE) cells with FGF2 increased proliferation and DNA replication based on increases in proliferating cell nuclear antigen (PCNA) and initiation of G1/S phase progression. In addition, FGF2 increases phosphorylation of AKT, P70S6K, S6, ERK1/2, JNK, P38, and P90RSK in a time-dependent manner, and increases in their expression was suppressed by Wortmannin (a phosphatidylinositol 3-kinase [PI3K] inhibitor), U0126 (an ERK1/2 inhibitor), SP600125 (a JNK inhibitor), and SB203580 (a P38 inhibitor) based on western blot analyses. Also, the abundance of cytoplasmic p-AKT protein was decreased by Wortmannin and U0126, and p-ERK1/2 protein was reduced only by U0126. Furthermore, inhibition of each signal transduction protein reduced the ability of FGF2 to stimulate proliferation and migration of pLE cells. Collectively, these results indicate that activation of FGFR1 and FGFR2 by uterine- and endometrial-derived FGF2 stimulates PI3K/AKT and mitogen-activated protein kinase pathways for development of the porcine uterus and improvement of litter size.

The effect of leptin on luteal angiogenic factors during the luteal phase of the estrous cycle in goats

Fibroblast growth factor 2 (FGF2), angiopoietin 1 (Ang1), and vascular endothelial growth factor (VEGF) are angiogenic factors implicated in the vascular development of the corpus luteum (CL). Each factor is regulated or influenced by leptin in non-ovarian tissues. Moreover, leptin and its receptor, ObRb, have been identified in luteal tissue throughout the luteal phase. Therefore, leptin is hypothesized to influence luteal vasculature through the regulation of FGF2, Ang1, and VEGF. Multiparous, cycling crossbred female goats (does) were allocated to early (n=12), mid (n=8), and late (n=11) stages of the luteal phase for CL collection. Luteal tissue was harvested and either snap frozen in liquid N2, paraffin embedded, or cultured with leptin (0, 10(-12), 10(-11), 10(-10), 10(-9), 10(-8)M). Tissue was analyzed for FGF2, Ang1, VEGF, ObRb, and leptin expression. Angiopoietin 1, FGF2, VEGF expression was higher (P≤0.001) in the mid-luteal stage than the early stage. Expression decreased (P≤0.001) during the late luteal stage with the exception of VEGF, which remained elevated. In contrast, leptin and ObRb were lowest (P≤0.003) during the mid-luteal stage compared to the early and late stages. All factors were detected in and/or around vessels in early stage tissue compared to mid and late stages. Leptin stimulated (P≤0.02) Ang1, FGF2, and VEGF expression only in early stage luteal cultures. Collectively, these data provide evidence that leptin may be involved in the luteal angiogenic process during the early stage of CL formation.

Fibroblast growth factor-2 expression in the preimplantation equine conceptus and endometrium of pregnant and cyclic mares

Uterine-derived growth factors and cytokines play essential roles in regulating preimplantation conceptus development. In several species, fibroblast growth factor-2 (FGF2) promotes embryogenesis, trophoblast cell migration, and adhesion. This study investigated mRNA expression for FGF2, its receptors (FGFR1-4), the activating factor FGF binding protein (FGF-BP) in equine endometrium and trophectoderm during early pregnancy and the estrous cycle, and localized FGF2 protein in both endometrium and conceptus tissues. FGF2, FGFRs1-4, and FGFBP mRNAs were expressed in endometrium throughout the estrous cycle and early pregnancy, and in days 14 to 28 conceptus membranes. FGF2 transcription was higher during estrus than on days 7 or 14 of diestrus, suggesting estrogen dependency. Endometrial expression of FGF2 mRNA and protein increased as pregnancy progressed from days 21 and day 28; FGF2 protein was localized predominantly in the luminal and glandular epithelium. FGF2 mRNA was detectable in trophectoderm from as early as day 14, and transcription and translation increased in day 21 and 28 allantochorion. FGF2 protein was localized mainly in the trophectoderm up to day 21 but was present in both trophectoderm and endoderm of day 28 allantochorion. FGFR1 mRNA was down-regulated in the endometrium at day 7 of diestrus but increased again by day 14. Gene expression for all of the FGFR2 splice variants, including FGFR2IIIc, was up-regulated during estrus. During early pregnancy, endometrial FGFR1 expression decreased, whereas FGFR2IIIc expression did not change. Conceptus mRNA expression for all FGFRs increased as pregnancy progressed. FGFBP expression remained unchanged in endometrium, but increased in the conceptus between days 14 and 28, suggesting a role in regulating FGF2 activity in the developing conceptus. We conclude that during weeks 3 and 4 of pregnancy, the equine endometrial epithelium produces FGF2, which may play a role in trophoblast development and adhesion.

In vitro release of ovarian progesterone is decreased during the oestrous cycle and pregnancy of swine with obesity/leptin resistance

Previous studies indicate that reproductive prolificacy of obese swine breeds is markedly influenced by embryo losses in early pregnancy. In such period, adequate secretion of progesterone (P4) by the ovary is essential for pregnancy success. This study analyses the luteal functionality during the oestrous cycle and early pregnancy of Iberian sows and Large White x Landrace females, in terms of P4 secretion after in vitro culture of luteal tissue stimulated or not with luteinizing hormone (LH). The secretion of progesterone (expressed in ng/mg of luteal tissue or ng/mgLT) of the corpora lutea of obese Iberian swine was always hampered when compared to lean genotypes, either during early oestrous cycle (110.7 ± 37.8 vs 259.7 ± 10.2 ng/mgLT; p < 0.0001), late oestrous cycle (49.0 ± 3.5 vs 75.92 ± 7.14 ng/mgLT; p < 0.0001) or early pregnancy (38.4 ± 2.1 vs 70.7 ± 5.3 ng/mgLT; p < 0.0001). The differences in basal P4 secretion remained after stimulation with LH. Finally, P4 secretion during early pregnancy of Iberian sows decreased with age and, hence, with obesity features (46.6 ± 4.2 vs 65.5 ± 4.8 ng/mgLT; p < 0.001). In conclusion, the results of the present study provide convincing evidence of a reduced luteal function during oestrous cycle and early pregnancy of sows with obesity/leptin resistance like Iberian sows, which may contribute to the low reproductive efficiency reported in this breed.

Expression of angiogenic basic fibroblast growth factor, platelet derived growth factor, thrombospondin-1 and their receptors at the porcine maternal-fetal interface

BACKGROUND

Commercial swine breeds in North America undergo two waves of spontaneous fetal loss; one during peri-attachment and another during mid-gestation. Although an exact mechanism for this loss is not known, deficits in vasculature at the attachment sites appear to be a major cause. We hypothesized that a balance between pro-angiogenic and anti-angiogenic factors is needed at the maternal-fetal interface for successful conceptus development. Six selected members of the pro-angiogenic fibroblast growth factor (FGF) and platelet derived growth factor (PDGF) families and anti-angiogenic factor thrombospondin-1 (TSP-1) and its receptor CD36 were quantified and localized at the porcine maternal-fetal interface at early and midgestation time points.

METHODS

Mesometrial endometrium was collected from non-pregnant gilts (n = 8). Endometrial and chorioallantoic membrane samples were collected from healthy and arresting conceptus attachment sites at gestation day (gd) 20 (n = 8) and gd 50 (n = 8). At gd20 arresting conceptus attachment sites were distinguished by decreased vasculature of the placental membranes and decreased conceptus size. At gd50 arresting conceptuses attachment sites were identified by smaller conceptus length and weight measurements. Quantitative real time PCR was used to determine relative transcript levels of genes of interest, and cellular localization was determined by immunohistochemistry in paraffin embedded endometrial sections.

RESULTS

At gd20, endometrial samples from arresting conceptuses had elevated transcripts for bFGF, and PDGF-bb than healthy sites (p < 0.05). At gd50, bFGF, FGFR2, and CD36 were more abundant at arresting than at healthy conceptus attachment sites (p < 0.05). Chorioallantoic membrane from arresting conceptus attachment sites at gd20 had elevated transcripts for bFGF, FGFR1, FGFR2 and CD36 compared with healthy sites (p < 0.05). FGFR2 transcripts were more abundant in chorioallantoic membrane from arresting conceptuses at gd 50 (p < 0.05). Immunohistochemical localization of selected pro- and anti-angiogenic factors and receptors revealed their abundance in the luminal epithelium, uterine glands and perivascular areas of endometrium at gd20 and gd50.

CONCLUSIONS

We provide comprehensive analysis of pro and anti-angiogenic factors at the porcine maternal fetal interface during early and mid-pregnancy. At mRNA levels, the majority of pro-angiogenic factors investigated were elevated at the sites of fetal arrest. These observations contrast with our previous findings of decreased Vascular Endothelial Growth Factor (VEGF) family members at arresting sites, and suggest that the bFGF family functions as a compensatory survival mechanism when major angiogenic proteins are decreasing at the sites of fetal arrest.

Effects of long-term progesterone on developmental and functional aspects of porcine uterine epithelia and vasculature: progesterone alone does not support development of uterine glands comparable to that of pregnancy

In pigs, endometrial functions are regulated primarily by progesterone and placental factors including estrogen. Progesterone levels are high throughout pregnancy to stimulate and maintain secretion of histotroph from uterine epithelia necessary for growth, implantation, placentation, and development of the conceptus (embryo and its extra-embryonic membranes). This study determined effects of long-term progesterone on development and histoarchitecture of endometrial luminal epithelium (LE), glandular epithelium (GE), and vasculature in pigs. Pigs were ovariectomized during diestrus (day 12), and then received daily injections of either corn oil or progesterone for 28 days. Prolonged progesterone treatment resulted in increased weight and length of the uterine horns, and thickness of the endometrium and myometrium. Hyperplasia and hypertrophy of GE were not evident, but LE cell height increased, suggesting elevated secretory activity. Although GE development was deficient, progesterone supported increased endometrial angiogenesis comparable to that of pregnancy. Progesterone also supported alterations to the apical and basolateral domains of LE and GE. Dolichos biflorus agglutinin lectin binding and αv integrin were downregulated at the apical surfaces of LE and GE. Claudin-4, α2β1 integrin, and vimentin were increased at basolateral surfaces, whereas occludins-1 and -2, claudin-3, and E-cadherin were unaffected by progesterone treatment indicating structurally competent trans-epithelial adhesion and tight junctional complexes. Collectively, the results suggest that progesterone affects LE, GE, and vascular development and histoarchitecture, but in the absence of ovarian or placental factors, it does not support development of GE comparable to pregnancy. Furthermore, LE and vascular development are highly responsive to the effects of progesterone.

Immunohistochemical expression of basic fibroblast growth factor and fibroblast growth factor receptors 1 and 2 in the pathogenesis of lung cancer

PURPOSE

To identify the patterns of protein expression of basic fibroblast growth factor (bFGF) and FGF receptors 1 and 2 in non-small cell lung carcinoma (NSCLC) and their role in the early pathogenesis of squamous cell carcinoma (SCC) of the lung.

EXPERIMENTAL DESIGN

Archived tissue from NSCLC (adenocarcinoma and SCC; n = 321) and adjacent bronchial epithelial specimens (n = 426) were analyzed for the immunohistochemical expression of bFGF, FGFR1, and FGFR2, and the findings were correlated with clinicopathologic features of the patients.

RESULTS

High expression of bFGF, FGFR1, and FGFR2 was shown in most NSCLC tumors. The pattern of expression for all markers varied according to tumor histologic type and cellular localization. Cytoplasmic expression scores were significantly higher in tumors than in normal epithelia. Nuclear bFGF (P = 0.03) and FGFR1 (P = 0.02) levels were significantly higher in women than in men. Although cytoplasmic FGFR1 expression was significantly higher (P = 0.002) in ever smokers than in never smokers, nuclear FGFR1 (P = 0.0001) and FGFR2 (P = 0.003) expression was significantly higher in never smokers. Different prognostic patterns for the expression of these markers were detected for both NSCLC histologic types. Dysplastic changes showed significantly higher expression of all markers compared with squamous metaplasia.

CONCLUSIONS

bFGF, FGFR1, and FGFR2 are frequently overexpressed in SCC and adenocarcinoma of the lung. bFGF signaling pathway activation may be an early phenomenon in the pathogenesis of SCC and thus an attractive novel target for lung cancer chemopreventive and therapeutic strategies.

Regulation of Expression of Fibroblast Growth Factor 7 in the Pig Uterus by Progesterone and Estradiol1

Fibroblast growth factor 7 (FGF7) stimulates cell proliferation, differentiation, migration and angiogenesis. The consensus is that FGF7, expressed by mesenchymal cells, binds FGF receptor 2IIIb (FGFR2) on epithelia, thereby mediating epithelial-mesenchymal interactions. The pig uterus is unique in that FGF7 is expressed by the luminal epithelium (LE) and FGFR2 is expressed by the LE, glandular epithelium (GE), and trophectoderm to effect proliferation and differentiated cell functions during conceptus development and implantation. FGF7 expression by the uterine LE of pigs increases between Days 9 and 12 of the estrus cycle and pregnancy, as circulating concentrations of progesterone increase, progesterone receptors (PGR) in the uterine epithelia decrease, and the conceptuses secrete estradiol-17beta (E(2)), for pregnancy recognition. Furthermore, E(2) increases the expression of FGF7 in pig uterine explants. The present study investigates the relationships between progesterone, E(2), and their receptors and the expression of FGF7 in the pig uterus in vivo. Pigs were ovariectomized on Day 4 of the estrus cycle and injected i.m. daily from Day 4 to Day 12 with either corn oil (CO), progesterone (P4), P4 and ZK317,316 (PZK), E(2), P4 and E(2) (PE), or P4 and ZK and E(2) (PZKE). All gilts (n = 5/treatment) were hysterectomized on Day 12. The results suggest that: 1) P4 is permissive to FGF7 expression by down-regulating PGR in LE; 2) P4 stimulates PGR-positive uterine stromal cells to release an unidentified progestamedin that induces FGF7 expression by LE; 3) E(2) and P4 can induce FGF7 when PGR are rendered nonfunctional by ZK; and 4) E(2) from conceptuses interacts via estrogen receptor alpha, but not estrogen receptor beta in LE to induce maximal expression of FGF7 in LE on Day 12 of pregnancy in pigs.

Positive correlation between estradiol and vascular endothelial growth factor but not fibroblast growth factor-2 in normal human breast tissue in vivo

PURPOSE

Angiogenesis is crucial in tumor development and progression. Ovarian hormones regulate angiogenesis in the reproductive tract but very little is known about its regulation in the normal breast. Sex steroids play an important role in breast cancer development by poorly understood mechanisms. Vascular endothelial growth factor (VEGF) and fibroblast growth factor-2 (FGF-2) are potent stimulators of angiogenesis. Both VEGF and FGF-2 function in autocrine/paracrine pathways and there is a major contribution of bioactive proteins by a posttranslational activation of sequestered molecules in the extracellular space. A direct measurement of these molecules in the extracellular compartment is, therefore, needed.

EXPERIMENTAL DESIGN

In this study, microdialysis was used to measure extracellular VEGF and FGF-2 in normal human breast tissue in situ in 11 premenopausal and 5 postmenopausal women.

RESULTS

Significantly higher level of VEGF in breast tissue of premenopausal women was found. Plasma as well as local estradiol and breast tissue VEGF exhibited significant correlations, whereas progesterone had no correlation with breast VEGF. FGF-2 did not correlate with either estradiol or progesterone.

CONCLUSION

The result suggests that estradiol is a more potent regulator of free VEGF levels than progesterone in the normal breast. The control of free FGF-2 seems to be independent of sex steroids in the breast. Estrogen induction of free extracellular VEGF may be one mechanism involved in sex steroid-dependent breast carcinogenesis.

Expression of epidermal growth factor receptor (EGF-R), vascular endothelial growth factor receptor (VEGF-R) and fibroblast growth factor receptor (FGF-R) systems in porcine oviduct and endometrium during the time of implantation

The oviduct and uterus provide the environment for the establishment of pregnancy. Among others, growth factor systems are involved in functional signaling interactions at the pre- and peri-implantation maternal-conceptus interface in pigs. Distinct regulation of epidermal growth factor Receptor (EGF-R), vascular endothelial growth factor receptor (VEGF-R) and fibroblast growth factor receptor (FGF-R) systems and of bioactivation of EGF-R in porcine oviduct and endometrium during the estrous cycle, early pregnancy and during steroid replacement in ovariectomized gilts is summarized. Remarkable influences of ovarian steroids and EGF on the expression of specific markers of transcription and translation in these tissues are discussed. Known biological effects of the EGF, VEGF and FGF are related to cellular differentiation and angiogenesis. This suggests their involvement in the transformation of the endometrium into a decidua subsequently leading towards successful establishment of pregnancy. Peripheral steroids may exert their effects on epithelial cells both in a direct genomic manner or through mediators such as growth factors. The aim of our study was to draw specific attention to the paracrine regulation in the porcine endometrium especially during the implantation window.