Localization of the sites of synthesis and action of insulin-like growth factor-I in the rat uterus

Human Chorionic Gonadotrophin as a Possible Mediator of Leiomyoma Growth during Pregnancy: Molecular Mechanisms

Uterine fibroids are the most common gynecologic benign tumors. Studies supporting a strong pregnancy-related growth of leiomyomas generally claimed a crucial role of sex steroid hormones. However, sex steroids are unlikely the unique actors involved as estrogen and progesterone achieve a pick serum concentration in the last trimester while leiomyomas show a typical increase during the first trimester. Given the rapid exponential raise in serum human Chorionic Gonadotrophin (hCG) at the beginning of gestation, we conducted a review to assess the potential role of hCG in the striking growth of leiomyomas during initial pregnancy. Fibroid growth during initial pregnancy seems to correlate to the similar increase of serum hCG levels until 12 weeks of gestation. The presence of functional Luteinizing Hormone/human Chorionic Gonadotropin (LH/hCG) receptors was demonstrated on leiomyomas. In vitro treatment of leiomyoma cells with hCG determines an up to 500% increase in cell number after three days. Expression of cyclin E and cyclin-dependent kinase 1 was significantly increased in leiomyoma cells by hCG treatment. Moreover, upon binding to the receptor, hCG stimulates prolactin secretion in leiomyoma cells, promoting cell proliferation via the mitogen-activated protein kinase cascade. Fibroid enlargement during initial pregnancy may be regulated by serum hCG.

The developmental transcriptome landscape of receptive endometrium during embryo implantation in dairy goats

Under natural conditions, some embryos cannot implant successfully because of the dysfunction of receptive endometrium (RE). Thus, it is imperative for us to study the molecular mechanisms involved in the formation of the RE from pre-receptive endometrium (PE). In this study, the endometrium from gestational day 5 (D5, PE) and gestational day 15 (D15, RE) dairy goats were selected to systematically analyze the transcriptome using strand-specific Ribo-Zero RNA-Seq, >120 million high-quality paired-end reads were generated and 47,616 transcripts were identified in the endometrium of dairy goats. A total of 810 mRNAs were differentially expressed genes (DEGs) between the RE and PE meeting the criteria of P-values<0.05. Bioinformatics analysis of the DEGs revealed that a number of biological processes and pathways were potentially involved in the establishment of the RE, notably energy metabolism and amino acid metabolism. Furthermore, we speculated that CXCL14, IGFBP3, and LGALS15 potentially participated in the development of endometrium. What's more, putative SNPs, InDels and AS events were identified and analyzed in the endometrium. In a word, this resulting view of the transcriptome greatly enhances the comprehensive transcript catalog and uncovers the global trends in gene expression during the formation of receptive endometrium in dairy goats.

Epithelial estrogen receptor 1 intrinsically mediates squamous differentiation in the mouse vagina

Estrogen-mediated actions in female reproductive organs are tightly regulated, mainly through estrogen receptor 1 (ESR1). The mouse vaginal epithelium cyclically exhibits cell proliferation and differentiation in response to estrogen and provides a unique model for analyzing the homeostasis of stratified squamous epithelia. To address the role of ESR1-mediated tissue events during homeostasis, we analyzed mice with a vaginal epithelium-specific knockout of Esr1 driven by keratin 5-Cre (K5-Esr1KO). We show here that loss of epithelial ESR1 in the vagina resulted in aberrant epithelial cell proliferation in the suprabasal cell layers and led to failure of keratinized differentiation. Gene expression analysis showed that several known estrogen target genes, including erbB growth factor ligands, were not induced by estrogen in the K5-Esr1KO mouse vagina. Organ culture experiments revealed that the addition of erbB growth factor ligands, such as amphiregulin, could activate keratinized differentiation in the absence of epithelial ESR1. Thus, epithelial ESR1 integrates estrogen and growth factor signaling to mediate regulation of cell proliferation in squamous differentiation, and our results provide new insights into estrogen-mediated homeostasis in female reproductive organs.

Insulin-like growth factor 1 mRNA expression in the uterus of streptozotocin-treated diabetic mice

Reproductive functions decline with the onset of diabetes in female mice. Diabetic mice have smaller uteri with an underdeveloped endometrium, suggesting diminished estrogen-induced growth. We aimed to clarify the changes in the estrous cycle and in insulin-like growth factor 1 (IGF1) expression in the uteri of streptozotocin (STZ)-treated diabetic mice, because IGF1 is one of the main growth factors involved in estrogen-induced uterine growth. ICR female mice were intraperitoneally administered STZ (10 mg/100 g BW), and blood glucose levels were determined. Mice with blood glucose levels > 200 mg/dl were classified as diabetic mice. The onset of diabetes was associated with acyclic estrous cycles. Diabetes was also induced with STZ in ovariectomized mice. Uterine Igf1 mRNA levels were reduced in ovariectomized STZ-treated diabetic mice. Estrogen is known to stimulate Igf1 mRNA expression in the uterus, but estrogen action was abolished in the uteri of STZ-treated diabetic mice. mRNA expressions of estrogen receptor α (ERα) and steroid hormone receptor coactivators (SRC-1/Ncoa1, SRC-2/Ncoa2, SRC-3/Ncoa3 and CBP/p300/Crebbp) were reduced in the uteri of ovariectomized STZ-treated diabetic mice. The present study demonstrates that diabetes induces a decline in female reproductive functions in mice. Igf1 expression in ovariectomized diabetic female mice was decreased, and decreased responsiveness to estrogen in the uteri of diabetic mice is probably associated with a reduction in ERα and steroid receptor coactivator mRNA expression.

Runx3 expression and its roles in mouse endometrial cells

Runx3 is a transcription factor that belongs to the Runx family. We studied the localization of Runx3 mRNA in the mouse uterus, and its function in the mouse endometrium using Runx3 knockout (Runx3(-/-)) mice. Runx3 mRNA was detected in the endometrial luminal epithelial cells, glandular epithelial cells and stromal cells below the epithelial cell layer on the luminal side. The uteri of Runx3(-/-) mice were smaller than those of wt mice. The endometrial layer and uterine glands of Runx3(-/-) mice were less developed than those of wild-type mice, and the endometrial stromal layer was thinner. Transforming growth factor β1 and β3 (TGFβ1 and β3) mRNA levels in endometrial stromal cells of Runx3(-/-) mice were low compared with those of wild-type mice. Estradiol-17β (E2) increased Tgfb2 mRNA levels in endometrial stromal cells of Runx3(-/-) mice, but not in those of wild-type mice. E2 increased epidermal growth factor (EGF) mRNA levels in endometrial stromal cells of wild-type mice, but did not increase those of Runx3(-/-) mice. The diminished Tgfb1 and Tgfb3 mRNA expressions may lead to the reduced proliferation of endometrial stromal cells. Alterations of E2-associated expressions of Tgfb2 and Egf mRNA in endometrial stromal cells of Runx3(-/-) mice may be associated with suppression of E2-dependent endometrial epithelial cell proliferation in Runx3(-/-) mice. Thus, Runx3 is likely to be a regulatory factor responsible for endometrial growth.

Role of cytokines in endometrium and at the fetomaternal interface

Cytokines were first recognized as factors involved in the immune responses. However, emerging evidence suggests that cytokines serve as the unanimous language through which cells in organ systems as diverse as hypothalamus to endometrium communicate. Evidence for the participation of these factors in the normal function of the endometrium and uteroplacental unit and development of the embryo is being recognized. This review will highlight the significant insight gained over the past several years for the role of cytokines in the field of reproductive biology. Major emphasis will be placed on interleukins, tumour necrosis factor-α, transforming growth factors, colony stimulating factors and interferon-gamma.

Distinct modes of activation of phosphatidylinositol 3-kinase in response to cyclic adenosine 3', 5'-monophosphate or insulin-like growth factor I play different roles in regulation of cyclin D1 and p27Kip1 in FRTL-5 cells

Bioactivities of IGFs in various cells are often potentiated in the presence of other hormones. In previous studies we showed that pretreatment of rat FRTL-5 thyroid cells with TSH or other cAMP-generating agents markedly potentiated DNA synthesis induced by IGF-I. Under these conditions we found that phosphatidylinositol (PI) 3-kinase was activated in response to either cAMP or IGF stimulus, and both activation modes were indispensable for the potentiation of DNA synthesis. The present studies were undertaken to elucidate how cAMP and/or IGF-I stimulus regulated the G1 cyclin-cyclin dependent kinase (CDK)-inhibitor system, and to determine the roles of PI 3-kinase activation by cAMP or IGF-I stimulus in this system. We found that cAMP pretreatment enhanced IGF-I-dependent increases in cyclin D1, due to synergistic increases in mRNA and elevation of translation rates. Furthermore, cAMP pretreatment enhanced IGF-I-induced protein degradation of the CDK inhibitor, p27(Kip1). These changes well explained an increase in cyclin E, leading to marked activation of G1 CDKs, followed by retinoblastoma protein phosphorylation. Our results using a PI 3-kinase inhibitor showed that cAMP-dependent PI 3-kinase activation plays an important role in the increase in cyclin D1 translation. In contrast, IGF-I-dependent PI 3-kinase activation was required for the increase in cyclin D1 mRNA levels and degradation of p27(Kip1). Together, the present study elucidates the role of cAMP and IGF-I in differentially activating PI 3-kinase as a mediator of multiple molecular events. These events converge in the regulation of cyclin D1 and p27(Kip1), leading to cAMP-dependent potentiation of IGF-I-dependent CDK activation and DNA synthesis.

Endometrial expression of the insulin-like growth factor system during uterine involution in the postpartum dairy cow

Rapid uterine involution in the postpartum period of dairy cows is important to achieve a short interval to conception. Expression patterns for members of the insulin-like growth factor (IGF) family were determined by in situ hybridisation at day 14+/-0.4 postpartum (n=12 cows) to investigate a potential role for IGFs in modulating uterine involution. Expression in each uterine tissue region was measured as optical density units and data were analysed according to region and horn. IGF-I mRNA was localized to the sub-epithelial stroma (SES) of inter-caruncular and caruncular endometrium. Both IGF-II and IGF-1R expression was detected in the deep endometrial stroma (DES), the caruncular stroma and myometrium. IGFBP-2, IGFBP-4 and IGFBP-6 mRNAs were all localised to the SES of inter-caruncular and caruncular uterine tissue, and in the DES and caruncular stroma, with IGFBP-4 mRNA additionally expressed in myometrium. IGFBP-3 mRNA was only detectable in luminal epithelium. IGFBP-5 mRNA was found in myometrium, inter-caruncular and caruncular SES and caruncular stroma. These data support a role for IGF-I and IGF-II in the extensive tissue remodelling and repair which the postpartum uterus undergoes to return to its non-pregnant state. The differential expression of binding proteins between tissues (IGFBP-3 in epithelium, IGFBP-2, -4, -5 and -6 in stroma and IGFBP-4 and -5 in myometrium) suggest tight control of IGF activity within each compartment. Differential expression of many members of the IGF family between the significantly larger previously gravid horn and the previously non-gravid horn may relate to differences in their rate of tissue remodelling.

Estradiol-17beta regulates mouse uterine epithelial cell proliferation through insulin-like growth factor 1 signaling

Estradiol-17beta (E(2)) causes cell proliferation in the uterine epithelium of mice and humans by signaling through its transcription factor receptor alpha (ERalpha). In this work we show that this signaling is mediated by the insulin-like growth factor 1 receptor (IGF1R) expressed in the epithelium, whose activation leads to the stimulation of the phosphoinositide 3-kinase/protein kinase B pathway leading to cyclin D1 nuclear accumulation and engagement with the canonical cell cycle machinery. This cyclin D1 nuclear accumulation results from the inhibition of glycogen synthase kinase 3beta (GSK3beta) activity caused by an inhibitory phosphorylation by protein kinase B. Once the IGF1 pathway is activated, inhibition of ER signaling demonstrates that it is independent of ER. Inhibition of GSK3beta in the absence of E(2) is sufficient to induce uterine epithelial cell proliferation, and GSK3beta is epistatic to IGF1 signaling, indicating a linear pathway from E(2) to cyclin D1. Exposure to E(2) is the major risk factor for endometrial cancer, suggesting that downstream activation of this IGF1-mediated pathway by mutation could be causal in the progression to ER-independent tumors.

Immunolocalization of insulin-like growth factor I (IGF-I) during preimplantation in rat uterus

OBJECTIVE

The aim of this study was to determine the insulin-like growth factor (IGF-I) immunolocalization in rat uterus at preimplantation period.

DESIGN

The tissue samples were examined from pregnant animals between gestational day 1 and 5 using immunocytochemistry.

RESULTS

While both the uterine luminal epithelium and the glandular epithelium were stained strongly from gestational day 1 - 3 by IGF-I antibody, the IGF-I immunoreactivity was moderate in myometrium and capillary endothelium. At this period, the IGF-I immunoreactivity was weakly present in a few endometrial stromal cells. At day 4, while IGF-I immunostaining intensity was particularly decreased in the basal domains of uterine luminal epithelium and glandular epithelium, it was similar to the first 3 days of gestation in myometrium and capillary endothelium. The endometrial vascularization and the number of stromal cells immunoreacting with IGF-I increased. The differentiation of stromal cells into decidual cells was seen at gestational day 5 and IGF-I was strongly expressed in the decidualizing cells. The IGF-I immunoreactivity in uterine luminal epithelium and glandular epithelium was similar to gestational day 4. IGF-I immunoreactivity was strongly detected in all of endometrial stromal cells.

CONCLUSION

These results indicate that IGF-I expression in the rat uterus changes in the early pregnancy process and increase toward to day when implantation will be initiated.

Progesterone Inhibits the Estrogen-Induced Phosphoinositide 3-Kinase→AKT→GSK-3β→Cyclin D1→pRB Pathway to Block Uterine Epithelial Cell Proliferation

The mammalian cell cycle is regulated by the cyclin/cyclin-dependent kinase (CDK) phosphorylation of the retinoblastoma (pRB) family of proteins. Cyclin D1 with its CDK4/6 partners initiates the cell cycle and acts as the link between extracellular signals and the cell cycle machinery. Estradiol-17β (E2) stimulates uterine epithelial cell proliferation, a process that is completely inhibited by pretreatment with progesterone (P4). Previously, we identified cyclin D1 localization as a key point of regulation in these cells with E2 causing its nuclear accumulation and P4 retaining it in the cytoplasm with the resultant inhibition of pRB phosphorylation. Here we show that E2 stimulates phosphoinositide 3-kinase to activate phosphokinase B/AKT to effect an inhibitory phosphorylation of glycogen synthase kinase (GSK-3β). This pathway is suppressed by P4. Inhibition of the GSK-3β activity in P4-treated uteri by the specific inhibitor, LiCl, reversed the nuclear accumulation of cyclin D1 and in doing so, caused pRB phosphorylation and the induction of downstream genes, proliferating cell nuclear antigen and Ki67. Conversely, inhibition of phosphoinositide 3 kinase by LY294002 or Wortmanin reversed the E2-induced GSK-3β Ser9 inhibitory phosphorylation and blocked nuclear accumulation of cyclin D1. These data show the reciprocal actions of E2 and P4 on the phosphoinositide 3-kinase through to the GSK-3β pathway that in turn regulates cyclin D1 localization and cell cycle progression. These data reveal a novel signaling pathway that links E2 and P4 action to growth factor-mediated signaling in the uterus.

Dynamic profiling of estrogen receptor and epidermal growth factor signaling in the uteri of genistein- and estrogen-treated rats

The pharmacokinetics and time course actions of the soy isoflavone, genistein, and estradiol benzoate (EB) on sex steroid and growth factor signaling were compared in the rat uterus. Following one s.c. injection of 500 mg genistein/kg BW or 500 microg EB/kg BW, AUC for genistein was 20171.8 ng h/ml and was 15.7 ng h/ml for estradiol-17-beta. Estrogen receptor-alpha (ER-alpha) decreased within 2 h of genistein or EB treatment, returning to basal levels within 24 and 48 h, respectively. In response to genistein and EB, progesterone receptors (PRs) A and B increased between 16 and 24 h, with a significant increase at 24 and 48 h. Epidermal growth factor receptor (EGFR) expression peaked 16 h after genistein or EB treatment, inversely correlating with extracellular regulating kinase (ERK) phosphorylation. These effects were inhibited by antiestrogen pretreatment, demonstrating a requirement for ER. At 16 h, uterine weight, epithelial cell height, and cell proliferation increased. While EGFR levels increased, phosphorylated EGFR was not altered. Reduced phosphorylation of downstream kinases corresponded with decreased stromal phosphorylated-ERK (P-ERK) immunolabeling, suggesting signal attenuation. Dynamic profiling of sex steroid receptors and EGF signaling molecules suggest a similar mechanism of action for genistein and EB in the uterus, albeit at approximately 1000-fold concentration.

Origin of plasma insulin-like growth factor-I (IGF-I) during estrus in goats

The objective of this study was to clarify the origin of the increase in plasma insulin-like growth factor-I (IGF-I) during estrus in goats. Focusing on the uterus, the effect of estradiol-17 beta (E2) on the secretion of IGF-I was examined using ovariectomized and hysterectomized animals. A single 5 microg/kg BW of E2 was injected intramuscularly into ovariectomized and hysterectomized goats for 3 consecutive days, and plasma IGF-I concentrations in the two groups were compared. The concentrations of IGF-I rose after the treatments in both groups. The concentrations were significantly higher from 3 to 8 days after the treatment than before the treatment in ovariectomized goats (P<0.05), and from 1 to 3 days after the treatment than before in hysterectomized goats (P<0.05). Thus higher concentrations of plasma IGF-I tended to last longer in ovariectomized than hysterectomized goats. The area under the IGF-I response curve for the 8-day period after the first injection of E2 tended to be greater in ovariectomized than in hysterectomized goats. The results show that E2 increases plasma IGF-I concentrations in goats, and suggest that E2-stimulated IGF-I in plasma may originate mainly from the uterus.

Involvement of androgen receptor in 17beta-estradiol-induced cell proliferation in rat uterus

Although it is known that, in the uterus, estrogen receptor alpha (ERalpha) is involved in proliferation and progesterone receptor in differentiation, the role of the two other gonadal-hormone receptors expressed in the uterus, androgen receptor (AR) and estrogen receptor beta (ERbeta), remains undefined. In this study, the involvement of AR in 17beta-estradiol (E(2))-induced cellular proliferation in the immature rat uterus was investigated. AR levels were low in the untreated immature uterus, but 24 h after treatment of rats with E(2), there was an increase in the levels of AR and of two androgen-regulated genes, IGF-I and Crisp (cysteine-rich secretory protein). As expected, E(2) induced proliferation of luminal epithelial cells. These actions of E(2) were all blocked by both the antiestrogen tamoxifen and the antiandrogen flutamide. The E(2)-induced AR was found by immunohistochemistry to be localized exclusively in the stroma, mainly in the myometrium, where it colocalized with ERalpha but not with ERbeta. ERbeta, detected with two different ERbeta-specific antibodies, was expressed in both stromal and epithelial cells either alone or together with ERalpha. Treatment with E(2) caused down-regulation of ERalpha and ERbeta in the epithelium. The data suggest that, in E(2)-induced epithelial cell proliferation, ERalpha induces stromal AR and AR amplifies the ERalpha signal by induction of IGF-I. Because AR is never expressed in cells with ERbeta, it is unlikely that ERbeta signaling is involved in this pathway. These results indicate an important role for AR in proliferation of the uterus, where estrogen and androgen do not represent separate pathways but are sequential steps in one pathway.

Possible role for insulin-like growth factor-I in the pathogenesis of cystic endometrial hyperplasia pyometra complex in the bitch

Cystic endometrial hyperplasia (CEH) is an important pathologic condition in the canine uterus and recognized as a common cause of illness and death in this species. The underlying cause and pathogenic mechanism responsible for this condition remains incompletely understood. Aberrant sex steroid hormone receptor expression in the uterus of dogs with CEH has been documented but not explained. In the dog there is an exceptionally high, progestin induced production of insulin-like growth factor-I (IGF-I) which is now generally accepted to be one of the most important growth factors with a high mitogenic effect on the uterus. Therefore, in this study the immunohistochemical staining intensity for IGF-I was compared among the uteri of 25 adult female dogs that had developed CEH and 14 healthy dogs in comparable stages of the estrus cycle. Specific staining for IGF-I was found in the cytoplasm epithelial cells and in smooth muscle cells of endometrium and myometrium. A marked increase in specific staining intensity for IGF-I was found in the surface epithelium, glandular epithelium and in the stroma of the uteri of dogs with CEH. The increase in IGF-I specific staining intensity was most prominent in the superficial endometrial stroma. Based on the known role of IGF-I in endometrial proliferation, it was concluded from the present study that high concentrations of IGF-I located in and around the epithelial cells of the endometrium in dogs with CEH, could play an important role in the development of CEH.

Requirement of estrogen receptor-alpha in insulin-like growth factor-1 (IGF-1)-induced uterine responses and in vivo evidence for IGF-1/estrogen receptor cross-talk

In the uterus insulin-like growth factor-1 (IGF-1) signaling can be initiated by estradiol acting through its nuclear receptor (estrogen receptor (ER)) to stimulate the local synthesis of IGF-1. Conversely, in vitro studies have demonstrated that estradiol-independent ER transcriptional activity can be induced by IGF-1 signaling, providing evidence for a cross-talk mechanism between IGF-1 and ER. To investigate whether ER alpha is required for uterine responses to IGF-1 in vivo, both wild-type (WT) and ER alpha knockout (alpha ERKO) mice were administered IGF-1, and various uterine responses to IGF-1 were compared. In both WT and alpha ERKO mice, IGF-1 treatment resulted in phosphorylation of uterine IGF-1 receptor (IGF-1R) and formation of an IGF-1R/insulin receptor substrate-1/ phosphatidylinositol 3-kinase signaling complex. In addition, IGF-1 stimulated phosphorylation of uterine Akt and MAPK in both WT and alpha ERKO mice. However, IGF-1 treatment stimulated BrdUrd incorporation and proliferating cell nuclear antigen expression in WT uteri only. To determine whether ER alpha can be activated in vivo by IGF-1 signaling, transgenic mice carrying a luciferase gene driven by two estrogen response elements (ERE-luciferase mice) were utilized. Treatment of ovariectomized ERE-luciferase mice with IGF-1 resulted in an increase in uterine luciferase activity that was attenuated in the presence of the ER antagonist ICI 182,780. Together these data demonstrate that 1) functional signaling proximal to IGF-1R is maintained in the alpha ERKO mouse uterus, 2) ER alpha is necessary for IGF-1 induction of uterine nuclear proliferative responses, and 3) cross-talk between IGF-1R and ER signaling pathways exists in vivo.

Disruption of the tissue inhibitor of metalloproteinase-1 gene in reproductive-age female mice is associated with estrous cycle stage-specific increases in stromelysin messenger RNA expression and activity

Tissue inhibitors of metalloproteinases (TIMPs) are expressed in the uteri of virtually all species, yet the precise role of these factors in uterine physiology is uncertain. It has been previously demonstrated that disruption of the TIMP-1 gene product in vivo results in altered reproductive cycles and an aberrant uterine phenotype. Because this phenotype may be due to an elevation in uterine matrix metalloproteinase (MMP) activity, the purpose of the following experiments was to identify which uterine MMPs may have their expression altered in response to disruption of the TIMP-1 gene. Mature female TIMP-1 wild-type and null mice were killed during each stage of the estrous cycle, and uterine MMP activity and transcript expression were assessed. Disruption of the TIMP-1 gene product was associated with an increase in total uterine protease activity. Gel zymography further revealed that uterine stromelysin (stromelysin-1, -2, and -3) activity was significantly increased in the TIMP-1 null mice, whereas Northern blot analysis indicated that an up-regulation of stromelysin-1 and -3 mRNA expression may contribute to this increase in activity. It is concluded from this study that TIMP-1 plays a pivotal role in regulating uterine stromelysins both at the level of protease activity and the level of transcript expression.

Targeted overexpression of IGF-I in smooth muscle cells of transgenic mice enhances neointimal formation through increased proliferation and cell migration after intraarterial injury

The response of arterial smooth muscle cells to injury is governed by a complex series of events. Significant among them is the paracrine production of peptide growth factors. To determine the impact of local IGF-I gene expression on vascular injury, the left carotid arteries of SMP8-IGF-I mice (in which IGF-I is selectively overexpressed in smooth muscle cells by means of a smooth muscle alpha-actin promoter) and wild-type controls were injured mechanically with an epon resin probe. After 7 and 14 d, a progressive increase in medial area was seen in both SMP8-IGF-I and wild-type mice, but they were not significantly different from each other. However, by 14 d there was a more than 4-fold increase in neointimal area in transgenic vs. wild-type. The intima/media ratios were also strikingly increased at 14 d in the IGF-I-overexpressing animals. The mitotic index, determined in animals injected daily with bromodeoxyuridine for 3 d before death, was markedly elevated in both the media and neointima 7 d after injury in SMP8-IGF-I mice, but the effect had subsided by 14 d. Despite a higher rate of cell division, the relative increase in medial area was less in the SMP8-IGF-I mice than in wild-type mice at both 7 and 14 d, consistent with a stimulation of cell migration to the neointima. The experiments reported here provide compelling evidence that paracrine expression of IGF-I is a powerful stimulus for smooth muscle cell proliferation and migration in vivo.

Paracrine regulation of apoptosis by steroid hormones in the male and female reproductive system

In males, androgens are essential in maintaining the integrity of the prostate. Androgen-ablation induces apoptosis of the prostatic epithelium. In females, ovariectomy induces apoptosis in uterine epithelium while progesterone inhibits this process. The objective of this study was to determine whether androgen and progesterone inhibit apoptosis, respectively, in mouse prostatic and uterine epithelia via steroid receptors in the epithelium or in the stroma. To address this question, prostatic tissue recombinants were prepared with rat urogenital sinus mesenchyme plus bladder epithelium from wild-type or testicular feminization mutant (Tfm) mice. Thus, prostatic tissue was generated having androgen receptor (AR) in both epithelium and stroma or in the stroma only. Castration of hosts induced apoptosis in the AR-negative Tfm prostatic epithelium with an epithelial apoptotic index virtually identical to prostatic tissue recombinants containing wild-type epithelium. Moreover, this castration-induced prostatic epithelial apoptosis was blocked by testosterone and dihydrotestosterone in both wild-type and Tfm prostatic tissue recombinants. Likewise, uterine tissue recombinants were prepared in which epithelium and/or stroma was devoid of progesterone receptor (PR) by using uterine epithelium and stroma of wild-type and PR knockout mice. Progesterone inhibited uterine epithelial apoptosis only in tissue recombinants prepared with PR-positive stroma. The PR status of the epithelium did not affect epithelial apoptotic index. Therefore, the apoptosis in prostatic and uterine epithelia is regulated by androgen and progesterone via stromal AR and PR, respectively. In both cases, epithelial AR or PR is not required for hormonal regulation of epithelial apoptosis in prostatic and uterine epithelium.

Uterine leiomyomas: mechanisms of tumorigenesis

Uterine leiomyomas, also called fibroids, are the most common reproductive tract neoplasm and the leading indication for hysterectomy in premenopausal women. The discovery and development of medicinal therapies for uterine leiomyoma have been hampered by a lack of understanding regarding the etiology and molecular mechanisms underlying the development of these lesions. Although the estrogen responsiveness of uterine leiomyoma is well established, the impact of environmental estrogens and their contribution to the development of these tumors is currently unknown. The Eker rat model of uterine leiomyoma has proven useful for addressing these issues and understanding the pathophysiology of this disease. The Eker rat is the only animal model that develops spontaneous uterine leiomyomas, and these tumors share many characteristics with those found in humans. The availability of tumor-derived cell lines from these rats has made this a valuable in vitro/in vivo model system for experimental studies to investigate molecular mechanisms of disease and to design interventional and preventative strategies for this clinically relevant tumor.

Altered hormonal responsiveness of proliferation and apoptosis during myometrial maturation and the development of uterine leiomyomas in the rat

Uterine leiomyomas are responsive to the ovarian steroids, estrogen and progesterone; however, a mechanistic understanding of the role of these hormones in the development of this common gynecologic lesion remains to be elucidated. We have used the Eker rat uterine leiomyoma model to investigate how ovarian hormones regulate or promote the growth of these tumors. Proliferative and apoptotic rates were quantitated in normal uterine tissues and leiomyomas in response to endogenous ovarian steroids. In 2- to 4-mo-old animals, cell proliferation in the normal uterus corresponded with high serum levels of steroid hormones during the estrous cycle, and apoptosis occurred in the rat uterus in all cell types following sharp, cyclical declines in serum hormone levels. It is interesting that the responsiveness of uterine mesenchymal cells changed between 4 and 6 mo of age, with significant decreases in both proliferative and apoptotic rates observed in myometrial and stromal cells of cycling animals. Leiomyomas displayed much higher levels of proliferation than did age-matched myometrium; however, their apoptotic index was significantly decreased in comparison with normal myometrium. This disregulation between proliferative and apoptotic responses, which were tightly regulated during ovarian cycling in the normal myometrium, may contribute to the disruption of tissue homeostasis and underlie neoplastic growth of these tumors.

Plasma insulin-like growth factor-I concentrations increase during the estrous phase in goats

The objective of this study was to characterize plasma insulin-like growth factor-I (IGF-I) profiles during the estrous cycle in goats. Frequent blood samples were drawn during the day of estrus and during the luteal phase on Day 10 after estrus, and plasma growth hormone (GH) and IGF-I profiles were examined. Then, daily blood samples were drawn throughout the estrous cycle or during induction of estrus by prostaglandin F(2alpha) (PGF(2alpha)) to further clarify the IGF-I profiles. GH was secreted in an episodic manner in the estrous and luteal phases in goats. There were no significant differences in the mean concentrations, pulse amplitude and pulse frequency of GH between the estrous and luteal phases. IGF-I concentrations during estrous phase were higher than those in the luteal phase (P<0.05). Plasma IGF-I increased approximately two days before behavioral estrus, and the IGF-I peak was observed in accordance with the appearance of estrus. The elevated IGF-I levels then declined to basal values 4 to 5 days after estrus. When estrus was induced by PGF(2alpha), plasma IGF-I concentrations increased after treatment, and the concentration 2 days after treatment (day of appearance of behavioral estrus) was significantly higher than concentrations before treatment (P<0.05). The elevated IGF-I levels then declined during the 3 days after treatment. These results indicate that plasma IGF-I concentrations increase during estrus in goats.

Expression of mRNA encoding insulin-like growth factors I and II by uterine tissues and placenta during pregnancy in the rat

The uterus and the placenta synthesize insulin-like growth factors (IGFs) and insulin-like binding proteins (IGFBPs). These growth factors are implicated in processes of proliferation and differentiation that occur in the uterus. To determine the patterns of expression of IGFs during rat pregnancy we used in situ hybridization with digoxigenin labeled probes on uterus from day 7 to day 16 of pregnancy. In early gestation days (7-8) both IGF mRNAs showed similar tissue distribution with relative abundance in the stroma and circular muscle layer. On days 11 and 12 expression for IGF-I mRNA was found in the mesometrial decidua and metrial gland and in the ectoplacental cone while clear expression of IGF-II mRNA could only be found in the latter. On days 13 and 14, expression for IGF-I mRNA could be detected in the mesometrial decidua and metrial gland but no expression was observed for IGF-II mRNA. A gradient of IGF-I mRNA expression could be observed in the placenta on day 16, with the trophoblastic cells of the basal zone expressing the signal with stronger intensity than in the labyrinthine zone. For IGF-II mRNA the highest expression was associated with the labyrinthine zone. Endovascular trophoblast was positive for both mRNAs. The spatial and temporal patterns of expression suggests a role for IGFs in the process of decidualization as well as in the establishment, growth and differentiation of the various trophoblast cells of the placenta.

Tissue-specific expression of messenger ribonucleic acids for insulin-like growth factors and insulin-like growth factor-binding proteins during perinatal development of the rat uterus

Insulin-like growth factor (IGF)-I and IGF-II play a number of important roles in growth and differentiation, and IGF-binding proteins (IGFBPs) modulate IGF biological activity. IGF-I has been shown previously to be essential for normal uterine development. Therefore, we used in situ hybridization assays to characterize the unique tissue- and developmental stage-specific pattern of expression for each IGF and IGFBP gene in the rat uterus during perinatal development (gestational day [GD]-20 to postnatal day [PND]-24). IGF-I and IGFBP-1 mRNAs were expressed in all uterine tissues throughout this period. IGFBP-3 mRNA was not detectable at GD-20 but became detectable beginning at PND-5, and the signal intensity appeared to increase during stromal and muscle development. IGFBP-4 mRNA was abundant throughout perinatal development in the myometrium and in the stroma, particularly near the luminal epithelium. IGFBP-5 mRNA was abundantly expressed in myometrium throughout perinatal development. IGFBP-6 mRNA was detected throughout perinatal development in both the stroma and myometrium in a diffuse expression pattern. IGF-II and IGFBP-2 mRNAs were not detected in perinatal uteri. Our results suggest that coordinated temporal and spatial expression of IGF-I and its binding proteins (IGFBP-1,-3,-4,-5, and -6) could play important roles in perinatal rodent uterine development.

Expression of insulin-like growth factor binding protein-4, insulin-like growth factor-I receptor, and insulin-like growth factor-I in the mouse uterus throughout the estrous cycle

Recent evidence suggests that a regulated insulin-like growth factor (IGF) system mediates the effects of estrogen, promoting the proliferation and differentiation of specific uterine cell types throughout the estrous cycle and during gestation in the rodent. Previous studies have shown that IGFs are differentially expressed in the mouse uterus during the periimplantation period. In the current study, we examined the expression of IGF binding protein-4 (IGFBP-4), IGF-I receptor (IGF-IR), and IGF-I in the mouse uterus throughout the estrous cycle. Ligand blot analysis was conducted on uterine homogenates using [125I]IGF-I. IGFBP-4 was detected in all uterine homogenates, varying in intensity throughout the estrous cycle. In situ hybridization studies at metestrus and diestrus demonstrated an intense IGFBP-4 mRNA signal in antimesometrial stromal cells between the luminal epithelium and the myometrium, but at proestrus and estrus, no IGFBP-4 signal was detected. No IGF-I mRNA was detected at any stage of the estrous cycle by in situ hybridization. However, by RT-PCR analysis, IGF-I mRNA was detected at all stages of the estrous cycle. RT-PCR analysis also showed IGF-IR mRNA throughout the estrous cycle. Using immunohistochemistry, IGF-IR immunostaining was detected throughout the estrous cycle and on days 2-7 of gestation, but was restricted to the glandular epithelium. These results suggest that uterine IGFBP-4 expression may not be dependent on uterine IGF-I expression. They also suggest that IGFBP-4 may play a role in uterine physiology independent of the inhibition of IGF-I action, and that IGF-IR is constitutively expressed in the mouse uterus.

Expression and localization of insulin-like growth factor-1 in normal and post-burn hypertrophic scar tissue in human

The migration of epithelial cells from dermal appendages toward the wound surface is essential for re-epithelialization of partial thickness burn injuries. This study provides evidence that these cells in vivo synthesize a mitogenic and fibrogenic factor, insulin-like growth factor-1 (IGF-1), which may promote the development of the post-burn fibroproliferative disorder, hypertrophic scarring (HSc). An evaluation of 7 post-burn hypertrophic scars, 7 normal skin samples obtained from the same patients and 4 mature scars revealed that IGF-1 expressing cells from the disrupted sweat glands tend to reform small sweat glands of 4-10 cells/gland in post-burn HSc. The number of these cells increases with time and the glands become larger in mature scar. Other epithelial cells such as those found in sebaceous glands and basal and suprabasal keratinocytes, also express IGF-1 protein and mRNA as detected by Northern and RT-PCR analysis of RNA obtained from whole skin and separated epidermis and dermis. However, cultured keratinocytes did not express mRNA for IGF-1. Histological comparisons between normal and HSc sections show no mature sebaceous glands in dermal fibrotic tissues but the number of IGF-1 producing cells including infiltrated immune cells was markedly higher in the dermis of hypertrophic scar tissues relative to that of the normal control. In these tissues, but not in normal dermis, IGF-1 protein was found associated with the extracellular matrix. By in situ hybridization, IGF-1 mRNA was localized to both epithelial and infiltrated immune cells. Collectively, these findings suggest that in normal skin, fibroblasts have little or no access to diffusible IGF-1 expressed by epithelial cells of the epidermis, sweat and sebaceous glands; while following dermal injury when these structures are disrupted, IGF-1 may contribute to the development of fibrosis through its fibrogenic and mitogenic functions. Reformation of sweat glands during the later stages of healing may, therefore, limit this accessibility, and lead to scar maturation.

Uterine and vaginal organ growth requires epidermal growth factor receptor signaling from stroma

Estrogens are crucial for growth and function of the female genital tract. Recently, we showed that induction of uterine epithelial proliferation by estradiol is a paracrine event requiring an estrogen receptor-positive stroma. Growth factors [such as EGF (epidermal growth factor) ligands] are likely paracrine mediators, which may directly or indirectly regulate epithelial proliferation in estrogen target organs via cell-cell interactions. In this report, we used mice with a null mutation in their EGF receptor (EGFR) to examine the role of EGFR signaling in growth of the uterus and vagina and in estrogen-induced uterine and vaginal epithelial proliferation. When WT and EGFR-knockout (EGFR-KO) uteri and vaginae were grown as renal capsule grafts in nude mice, growth of uterine and vaginal grafts of EGFR-KO mice was reduced, compared with their WT counterparts. Grafts of both EGFR-KO uteri and vaginae were about one third smaller (wet weight) than their corresponding WT organs, even though differentiation of both epithelium and mesenchyme were normal in both cases. Both wild-type and EGFR-KO vaginal grafts contained within their lumina alternating layers of cornified and mucified epithelial cell layers, indicating cyclic alteration of epithelial differentiation. In response to estradiol treatment, stromal cell labeling index (LI), as assessed by incorporation of 3H-thymidine, was severely depressed in EGFR-KO uterine and vaginal grafts vs. stromal cell LI in WT uterine and vaginal grafts. Unexpectedly, epithelium of both EGFR-KO and wild-type grafts responded comparably to estradiol with a marked elevation (approximately 7-fold overall) of epithelial LI in response to estradiol in uterine and vaginal epithelia. These data supported the hypothesis that overall uterine and vaginal organ growth, in response to estrogen, required EGFR signaling for DNA synthesis in the fibromuscular stroma, whereas EGFR signaling was not essential for estrogen-induced epithelial growth in the uterus and vagina.

Endometrial transcripts of human insulin-like growth factors arise by differential promoter usage

By the application of RT-PCR, we have demonstrated that in the human endometrium mRNAs for insulin-like growth factors, IGF-I and II, and their receptors are expressed not only in the intact endometrium, but also in the freshly isolated stromal and epithelial cells. The expression of multiple transcript forms of the IGF-I and II at various phases of the menstrual cycle, occurs by differential use of all four IGF-I transcriptional start sites, and two of the four known promoter sites of the IGF-II gene. The complete spectrum of transcripts is displayed by the proliferative phase and the menstrual phase endometrium. During the secretory phase, the exon 1 upstream start site of the IGF-I gene and the P2 promoter of the IGF-II gene are not used. Irrespective of the phase of the menstrual cycle, the stromal cells always display the same transcriptional patterns of both growth factor genes as those of the intact endometrium. In contrast, the epithelial cells do not express IGF-I transcript originating from the exon 2 upstream initiation site. These results indicate that the expressions of the IGF-I and II genes in the intact endometrium and stromal and epithelial cells are modulated at the transcriptional level during the menstrual cycle by differential usage of promoters and start sites.

Role of astroglia and insulin-like growth factor-I in gonadal hormone-dependent synaptic plasticity

Gonadal hormones exert a critical influence over the architecture of specific brain areas affecting the formation of neuronal contacts. Cellular mechanisms mediating gonadal hormone actions on synapses have been studied extensively in the rat arcuate nucleus, a hypothalamic center involved in the feed-back regulation of gonadotropins. Gonadal steroids exert organizational and activational effects on arcuate nucleus synaptic connectivity. Perinatal testosterone induces a sexual dimorphic pattern of synaptic contacts. Furthermore, during the preovulatory and ovulatory phases of the estrous cycle there is a transient disconnection of inhibitory synaptic inputs to the somas of arcuate neurons. This synaptic remodeling is induced by estradiol, blocked by progesterone, and begins with the onset of puberty in females. Astroglia appear to play a significant role in the organizational and the activational hormone effects on neuronal connectivity by regulating the amount of neuronal membrane available for the formation of synaptic contacts and by releasing soluble factors, such as insulin-like growth factor I (IGF-I), which promote the differentiation of neural processes. Recent evidence indicates that gonadal steroids and IGF-I may interact in their trophic effects on the neuroendocrine hypothalamus. Estradiol and IGF-I promote the survival and morphological differentiation of rat hypothalamic neurons in primary cultures. The effect of estradiol depends on IGF-I, while the effects of both estradiol and IGF-I depend on estrogen receptors. Furthermore, estrogen activation of astroglia in hypothalamic tissue fragments depends on IGF-I receptors. These findings indicate that IGF-I may mediate some of the developmental and activational effects of gonadal steroids on the brain and suggest that IGF-I may activate the estrogen receptor to induce its neurotrophic effects on hypothalamic cells. In addition, IGF-I levels in the neuroendocrine hypothalamus are regulated by gonadal steroids. IGF-I levels in tanycytes, a specific astroglia cell type present in the arcuate nucleus and median eminence, increase at puberty, are affected by neonatal androgen levels, show sex differences, and fluctuate in accordance to the natural variations in plasma levels of ovarian steroids that are associated with the estrous cycle. These changes appear to be mediated by hormonal regulation of IGF-I uptake from blood or cerebrospinal fluid by tanycytes. These results suggest that tanycytes may be involved in the regulation of neuroendocrine events in adult rats by regulating the availability of IGF-I to hypothalamic neurons. In summary, IGF-I and different forms of neuron-astroglia communication are involved in the effects of estradiol on synaptic plasticity in the hypothalamic arcuate nucleus.

Targeted overexpression of IGF-I evokes distinct patterns of organ remodeling in smooth muscle cell tissue beds of transgenic mice

Smooth muscle cells (SMC) of the vascular wall, bladder, myometrium, and gastrointestinal and respiratory tracts retain the ability to proliferate postnatally, which enables adaptive responses to injury, hormonal, or mechanical stimulation. SMC growth is regulated by a number of mesenchymal growth factors, including insulin-like growth factor I (IGF-I). To explore the function of IGF-I on SMC in vivo, the mouse SMC alpha-actin promoter fragment SMP8 (-1074 bp, 63 bp of 5'UT and 2.5 kb of intron 1) was cloned upstream of rat IGF-I cDNA, and the fusion gene microinjected to fertilized eggs of the FVB-N mouse strain. Mating of hemizygous mice with controls produced about 50% transgenic offspring, with equal sex distribution. Transgenic IGF-I mRNA expression was confined to SMC-containing tissues, with the following hierarchy: bladder > stomach > aorta = uterus > intestine. There was no transgene expression in skeletal muscle, heart, or liver. Radioimmunoassayable IGF-I content was increased by 3.5- to 4-fold in aorta, and by almost 10-fold in bladder of transgenic mice at 5 and 10 wk, with no change in plasma IGF-I levels. Wet weight of bladder, stomach, intestine, uterus, and aorta was selectively increased, with no change in total body or carcass weight of transgenic animals. In situ hybridization showed that transgene expression was exquisitely targeted to the smooth muscle layers of the arteries, veins, bladder, ureter, stomach, intestine, and uterus. Paracrine overproduction of IGF-I resulted in hyperplasia of the muscular layers of these tissues, manifesting in remarkably different phenotypes in the various SMC beds. Whereas the muscular layer of the bladder and stomach exhibited a concentric thickening, the SMC of the intestine and uterus grew in a longitudinal fashion, resulting in a marked lengthening of the small bowel and of the uterine horns. This report describes the first successful targeting of expression of any functional protein capable of modifying the phenotype of SMC in transgenic mice. IGF-I stimulates SMC hyperplasia, leading to distinct patterns of organ remodeling in the different tissue environments.

Expression of insulin-like growth factors (IGFs), their receptors and IGF binding protein-3 in normal, benign and malignant smooth muscle tissues

To assess the role of insulin-like growth factors (IGFs) in growth and transformation of normal (myometrium) and tumorous smooth muscle cell (SMC) tissues, in situ hybridization (ISH) analysis for insulin-like growth factor I and II (IGF-I and IGF-II) mRNAs was combined with detection of IGF peptides, their receptors and IGF binding protein-3 (IGFBP-3). mRNAs for both IGFs were detected in smooth muscle cells in normal, benign and malignant SMC tissues, together with the IGF peptides, both IGF receptors and IGFBP-3. This suggests an autocrine role for both IGFs. Leiomyomas had higher IGF-I peptide levels and higher levels of type I IGF receptors than myometrium, supporting the idea that IGFs play a role in the growth and transformation of these tumours. Low-grade leiomyosarcomas contained more IGF-II mRNAs than myometrium and leiomyoma, fewer type II IGF/mannose 6-phosphate receptors and less IGFBP-3 than myometrium and, in addition, fewer IGF-I mRNAs and type I IGF receptors than leiomyoma. Intermediate- and high-grade leiomyosarcomas had intermediate levels of IGF-II mRNAs and peptide, ranging between those in myometrium and low-grade leiomyosarcomas. Thus, growth and transformation of leiomyosarcomas may be regulated by IGF-II, although more markedly in low-grade than in high-grade leiomyosarcomas. In conclusion, the various categories of SMC tissues are associated with a distinct expression pattern of the IGF system. This suggests that each category of SMC tumours arises as a distinct entity and that there is no progression of transformation in these tissues.

Interaction of insulin-like growth factor-I and estradiol signaling pathways on hypothalamic neuronal differentiation

Neurotrophic effects of estradiol and insulin-like growth factor-I were assessed in primary cultures from fetal rat hypothalamus. Cultured neurons were immunostained with an antibody for the microtubule-associated protein-2. While both estradiol and insulin-like growth factor-I increased the number of microtubule-associated protein-2-immunoreactive neurons and the extension of immunoreactive processes, the effect of these two factors was not additive. The estradiol-induced increases in neuronal numbers and extension of neuronal processes were blocked by either the estrogen receptor antagonist ICI 182,780 or by an anti-sense oligonucleotide to the estrogen receptor. Furthermore, incubation of the cultures with an anti-sense oligonucleotide directed against the insulin-like growth factor-I messenger RNA also blocked the effect of estradiol. In turn, the effects of insulin-like growth factor-I were blocked by the estrogen receptor antagonist ICI 182,780 and by the anti-sense oligonucleotide to the estrogen receptor. These findings suggest that estradiol-induced activation of the estrogen receptor in developing hypothalamic cells requires the presence of insulin-like growth factor-I, and that both estradiol and insulin-like growth factor-I use the estrogen receptor as a mediator of their trophic effects on hypothalamic neurons.

Influence of blockers for the estrogen receptor (ER) and type 1 IGF-receptor on the levels of ER, ER mRNA and IGF-I mRNA in the rat uterus

The effects on the uterine concentration of the estrogen receptor (ER), ER mRNA and IGF-I mRNA were monitored in ovariectomized (OVX) rats treated with blockers for the estrogen receptor (ER) (ICI 182780) or the type 1 IGF receptor (H-1356), alone or in combination with estradiol (E2). The hormone-mediated increase in uterine wet weight after E2 treatment was prevented by a simultaneous injection of ICI 182780. The levels of IGF-I mRNA and ER mRNA increased in rats given estradiol (E2), but not in those also receiving ICI 182780. The level of uterine ER was decreased in all animals that received ICI 182780. H-1356 (H) given as a continuous infusion decreased the estradiol-induced increase in uterine wet weight 24 h after a single E2 injection, but not 48 h after the first (of two) E2 injections. The IGF-I mRNA was increased in the E2 treated group after 24 h, and in both the E2 and H + E2 treated groups after 48 h. The ER mRNA was increased in the E2 treated group after 24 h, but not after 48 h. When H-1356 was given as two single injections and estradiol was or was not administered together with the second injection, the uterine wet weight was not increased as in the group receiving E2 only. The levels of IGF-I mRNA as well as ER mRNA were increased both after E2 and H + E2 treatment. In conclusion, the uterine growth stimulated by E2 was prevented by simultaneous treatment with ICI 182780. In addition a type 1 IGF-receptor blocker, which is an IGF-I analogue inhibiting the autophosphorylation of the receptor, also prevented the hormone-induced uterine growth after 24 h, but not after 48 h, when given as a continuous infusion. The results imply that the growth process stimulated by estradiol utilizes the ER receptor, and also the type 1 IGF-receptor during the first 24 h after E2 treatment.

Major secretory product of the mesometrial decidua in the rat, a variant of alpha-2-macroglobulin, binds insulin-like growth factor I via a protease-dependent mechanism

Decidualization-associated protein (DAP), the quantitatively major secretory product of the mesometrial decidua in the rat, is a pl variant of the liver-derived acute-phase reactant, alpha-2-macroglobulin (alpha 2M). Alpha 2M, a broad spectrum protease inhibitor, has been demonstrated in the human to bind a variety of cytokines and growth factors. In humans, the quantitatively major secretory product of decidual tissue is an insulin-like growth factor (IGF) binding protein. In this study, we have therefore tested the ability of liver- and decidual-derived alpha 2M in the rat to bind IGF-I. Alpha 2M purified from acute-phase plasma and DAP purified from cytosolic extracts of decidual tissue and medium from tissue incubations both bound radiolabeled IGF-I. The binding of IGF-I was principally dependent upon the coincubation of the protein with a proteinase. Therefore, it occurred during the conversion of the "slow" to the "fast" form of alpha 2M. Pretreatment with proteinase to produce the fast form before addition of the IGF-I reduced the binding. Binding was enhanced at a ratio protein:proteinase of 1:1. Results from gel electrophoretic analysis were consistent with the covalent linkage of IGF-I to alpha 2M during the cleavage of the "bait region." A saturable displacement by increasing concentrations of unlabeled IGF-I suggested high affinity interaction. Under conditions of demonstrated binding to purified proteins binding in acute-phase plasma, decidual tissue extracts and tissue incubation medium were associated with a high molecular weight species which was confirmed to represent alpha 2M and DAP, respectively. Our studies demonstrate that IGF-I may now be added to the list of regulatory peptides which alpha 2M may bind and that, in rat decidua, DAP may represent the functional homolog of decidual IGFBP-1 in the human and regulate growth factor function during placental development.

Cervical ripening in humans: potential roles of estrogen, progesterone, and insulin-like growth factor-I

OBJECTIVE

During pregnancy in humans a gradual connective tissue remodeling takes place in the cervix. The aim of this study was to examine a possible relationship between the action of gonadal steroids and growth factors and the biochemically identifiable changes in connective tissues during cervical ripening.

STUDY DESIGN

Cervical biopsy specimens and serum samples were taken from 20 term pregnant and 20 nonpregnant menstruating women. Estrogen receptors and progesterone receptors were measured with enzyme immunoassays. The messenger ribonucleic acid levels for estrogen receptors, progesterone receptors, and insulin-like growth factor-I were determined by solution hybridization with human complementary deoxyribonucleic acid probes. The concentration of collagen and its solubility by pepsin digestion were measured. Statistical evaluations were done with the Student t test.

RESULTS

In term pregnancy the estrogen receptor level decreased to 14% and the progesterone receptor level to 24% of nonpregnant levels (p <0.001 and p <0.01). The insulin-like growth factor-I messenger ribonucleic acid level increased 400% (p <0.01), whereas the messenger ribonucleic acid levels for estrogen receptors and progesterone receptors were unchanged. The changes coincided with a twofold decrease in collagen concentration (hydroxyproline) and a twofold increase in collagen solubility.

CONCLUSION

Estrogen receptors and progesterone receptors are present in human cervix. A significant down-regulation of estrogen receptors and progesterone receptors and a fourfold increase in the insulin-like growth factor-I messenger ribonucleic acid level were registered in term pregnant cervix. These findings coincided with the remodeling of the cervical connective tissue.

Effects of insulin-like growth factor-I, estrogen, glucocorticoid, and transferrin on the mRNA contents of ovalbumin and conalbumin in primary cultures of quail (Coturnix coturnix japonica) oviduct cells

The effects of estrogen, dexamethasone, insulin-like growth factor-I (IGF-I), and transferrin on the messenger RNA (mRNA) contents of ovalbumin and conalbumin in primary cultures of quail oviduct cells were investigated. In the absence of one of the above hormones or factors, a decrease in ovalbumin mRNA was prominent. In particular, removal of IGF-I and transferrin caused a significant effect. Studies using a combination of estrogen, dexamethasone, IGF-I and transferrin indicated that IGF-I cooperates with estrogen or dexamethasone and transferrin works with dexamethasone. Specifically, IGF-I enhanced ovalbumin synthesis or increased cellular ovalbumin mRNA content depending on its concentration in the medium in the presence of estrogen. However, the effects of estrogen, dexamethasone, IGF-I, and transferrin were not similarly observed with conalbumin mRNA. These results show that ovalbumin synthesis is controlled by estrogen or glucocorticoid with IGF-I or transferrin and that cellular ovalbumin mRNA content is also regulated by these hormones or transferrin. In contrast, conalbumin synthesis and cellular content of conalbumin mRNA are not affected by these hormones under the conditions of the present study.

Effects of somatotropin on the conceptus, uterus, and ovary during maternal recognition of pregnancy in cattle

Effects of recombinant bovine somatotropin (rbST) on ovarian and uterine function and the production of components of the insulin-like growth factor (IGF) system were examined during the period of maternal recognition of pregnancy in cattle. Lactating dairy cows were treated with 25 mg/d rbST (n = 8) or saline (n = 8) for 16 d after estrus. Ovaries, uteri, and conceptuses were collected on Day 17 after estrus. The length (millimeters) of the conceptus was recorded. The concentration of IGF-I and the content of IGF-binding proteins (BP) in uterine flushings were determined. Corpora lutea (CL) were weighed, and the number of follicles (> or = 2 mm in diameter) were counted. Follicular fluid from the largest and second-largest follicles was assayed for the concentration of IGF-I, IGFBP, progesterone, and estradiol. The length of the conceptus and the total amount of IGF-I in uterine fluid were similar for rbST and control. Recombinant bST increased 1) the weight of the CL, 2) the number of largest follicles (10 to 15 mm in diameter), 3) the concentration of IGF-I in the follicular fluid, 4) the follicular fluid content of IGFBP of the largest estrogenic follicle, and 5) the quantity of IGFBP in uterine flushings. The concentration of progesterone in the follicular fluid tended to be increased in rbST-treated cows, whereas the concentration of estradiol was similar to that of control cows. The concentration of progesterone in plasma was similar for rbST compared with control. In conclusion, the administration of rbST in lactating dairy cows for 16 d after estrus did not alter the growth of the conceptus collected on Day 17. The greatest responses to rbST were found within the ovary, where rbST increased the weight of the CL and altered the amount of IGF-I and IGFBP in the follicular fluid.

Role of insulin-like growth factors in steroid modulated proliferation

The mechanism by which steroids influence cell proliferation is poorly understood although an understanding of this process might facilitate the development of strategies to modulate the tissue-specific activity of steroid hormones. In this article, the evidence that steroid hormones interact with the insulin-like growth factor (IGF) signal transduction pathway is reviewed for three different tissues. In osteoblasts, oestradiol stimulates the production of IGF-I which appears to act as an autocrine growth factor. In uterine tissue, oestradiol increases the synthesis of IGF-I in the stroma which then modulates the proliferation of epithelial cells although there is also evidence that oestradiol can modulate the sensitivity of uterine epithelial cells to IGFs. In breast cancer, oestrogens may increase IGF-II synthesis in epithelial cells, increase the sensitivity of breast cancer cells to IGFs (possibly by modulating type I IGF receptor levels) as well as resulting components of the IGF signal transduction pathway resulting in induction of immediate early genes. There therefore appears to be a variety of ways in which oestradiol interact with the IGF signal transduction pathway and these may be applicable to other malignant and normal tissues and other groups of steroid hormones.

Site of production of IGF1 in the normal and stimulated mouse thyroid

Insulin-like growth factor 1 (IGF1) has emerged as an essential factor in the follicular cell growth response in vitro to TSH, although its source within the thyroid in vivo is not clear. We have studied the localisation of IGF1 mRNA by in situ hybridization using digoxigenin labelled oligoprobes in tissue sections of mouse thyroid. Our results show that in the thyroid IGF1 mRNA is predominantly present in follicular cells and C cells rather than the stroma. Follicular cell levels are higher during postnatal thyroid growth and during the growth response to goitrogen administration, but decrease in the mature animal. This decrease in production is limited to the follicular cells, as IGF1 mRNA is still easily demonstrable in C cells and in the parathyroid. Immunocytochemistry for IGF1 peptide shows a weak and variable follicular cell content in both juvenile and mature mice, but a more uniform distribution during growth in response to a goitrogenic stimulus. These studies show that the follicular cells are the main source of IGF1 in the thyroid, and suggest that the role of IGF1 in follicular cell growth is as an autocrine factor.

Progesterone-dependent expression of keratinocyte growth factor mRNA in stromal cells of the primate endometrium: keratinocyte growth factor as a progestomedin

In vitro studies have shown that keratinocyte growth factor (KGF, also known as FGF-7) is secreted by fibroblasts and is mitogenic specifically for epithelial cells. Therefore, KGF may be an important paracrine mediator of epithelial cell proliferation in vivo. Because stromal cells are thought to influence glandular proliferation in the primate endometrium, we investigated the hormonal regulation and cellular localization of KGF mRNA expression in the rhesus monkey uterus. Tissues were obtained both from naturally cycling monkeys in the follicular and luteal phases of the cycle, and from spayed monkeys that were either untreated or treated with estradiol (E2) alone, E2 followed by progesterone (P), E2 plus P, or E2 plus P plus an antiprogestin (RU 486). Northern blot analysis of total RNA with 32P-labeled probes revealed that the level of KGF mRNA in the endometrium was 70-100-fold greater in the luteal phase or after P treatment than in untreated, E2-treated, or follicular phase animals. Northern analysis also showed that KGF mRNA was present in the myometrium but was unaffected by hormonal state. RU 486 treatment prevented the P-induced elevation of endometrial KGF mRNA. P-dependent elevation of endometrial KGF expression was confirmed by measurement of KGF protein in tissue extracts using a two-site enzyme-linked immunosorbent assay. In situ hybridization with nonradioactive digoxigenin-labeled cDNA probes revealed that the KGF mRNA signal, which was present only in stromal and smooth muscle cells, was substantially increased by P primarily in the stromal cells located in the basalis region. Smooth muscle cells in the myometrium and the walls of the spiral arteries also expressed KGF mRNA, but the degree of this expression did not differ with hormonal state. P treatment led to increased proliferation in the glandular epithelium of the basalis region and to extensive growth of the spiral arteries. We conclude that the P-dependent increase in endometrial KGF resulted from a dual action of P: (a) a P-dependent induction of KGF expression in stromal cells, especially those in the basalis (zones III and IV), and (b) a P-dependent increase in the number of KGF-positive vascular smooth muscle cells caused by the proliferation of the spiral arteries. KGF is one of the first examples in primates of a P-induced, stromally derived growth factor that might function as a progestomedin.

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.

Regulation of endometrial cancer cell growth by insulin-like growth factors and the luteinizing hormone-releasing hormone antagonist SB-75

The involvement of IGFs in growth regulation of the Ishikawa endometrial tumor cell line and the possible interference of LH-RH analogues with a potential autocrine or paracrine loop involving IGFs was evaluated. The mitogenic effects of IGF-I, IGF-II, and insulin were compared. IGF-I was found to be 3-fold more potent than IGF-II and 30-fold more potent than insulin, suggesting that the effects of these growth factors are mediated by the IGF-I receptor. Ishikawa endometrial cancer cells secrete IGF-II, but not IGF-I, and insulin (1 microM) stimulates IGF-II release. The LH-RH antagonist [Ac-D-Nal(2)1, D-Phe(4Cl)2, D-Pal(3)3, D-Cit6, D-Ala10]-GnRH (SB-75, CETRORELIX) inhibited basal and IGF-induced growth. Moreover, this antagonist almost completely inhibited IGF-II release from Ishikawa cells, while having no significant effect on the number or affinity of IGF-I binding sites. Inhibition of IGF-II release occurred at a lower SB-75 concentration than that needed for a reduction in cell number. The ED50 of SB-75 for IGF-II release was 0.3 microM as compared to 1.5 microns concentration which is required for reduction in cell number, suggesting that inhibition of growth factor release precedes cell growth inhibition. We conclude that the LH-RH antagonist SB-75 can inhibit the growth of endometrial cancer cells by interfering with the autocrine action of IGF-II and also by directly inhibiting the growth-stimulatory effects of IGFs, probably through effects on a post-receptor mechanism.

Expression and regulation of insulin-like growth factor binding protein-1 in the rat uterus throughout estrous cycle

In previous studies, we have demonstrated that IGF-1 and IGF-1 receptor are expressed in rat uterus and that the expression is up-regulated by estrogen. The present study examines the expression and regulation of IGFBP-1 and IGFBP-3 in rat uterus throughout the estrous cycle. The stage of the estrous cycle in 16 mature female rats was determined by microscopic examination of daily prepared vaginal smears. Rat uteri were then used for RNA extraction. The results of the Northern blot analysis demonstrate that uterine cells express both IGFBP-1 and IGFBP-3 mRNA throughout the estrous cycle. When autoradiograms were quantitated by a densitometry, a significant reduction in expression of IGFBP-1 mRNA was found in uteri at stages of proestrous and estrous relative to that in diestrus. Although the level of IGFBP-3 mRNA varied in uteri throughout estrous cycle but this variation was not statistically significant. The lowest expression of IGFBP-1 (8.5% relative to diestrus, p < 0.05, n = 4) and IGFBP-3 (71% relative to diestrus) was found in the uteri prepared from rats at the stage of proestrus, while the highest expression of IGFBP-1 and IGFBP-3 was observed in the uteri obtained from rats at the stage of diestrus and metestrus, respectively. Using anti-rabbit IGFBP-1 antibody raised against an oligo-synthetic IGFBP-1 peptide, immunohistochemical staining demonstrates the presence of IGFBP-1 in the luminal and stromal glandular epithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Possible autocrine/paracrine actions of insulin-like growth factors during embryonic development: expression and action of IGFs in undifferentiated P19 cells

The insulin-like growth factors I and II (IGF I and II) and their cell surface receptors are expressed in the mammalian embryo and may function as autocrine or paracrine growth factors during early development. P19 embryonic carcinoma cells, derived from a 7.5 day mouse embryo, were used as a model for a functional study of the IGF system in post-implantation embryogenesis. Undifferentiated P19 cells synthesized IGF I and II, the type I and II IGF receptors, and IGF binding proteins (IGF BP2, IGF BP3, and IGF BP4). P19 cells showed an increase in thymidine incorporation of 150% of control with a 4 hour incubation of IGF I (10 ng/ml) or IGF II (100 ng/ml) and an increase in cell viability compared to control cells during 24 hours of serum starvation. In both experiments IGF I was more potent than IGF II. Endogenous concentrations of IGF I and II in conditioned media were low compared to the doses of exogenous IGFs required for biologic effect, but nonetheless contributed significantly to baseline DNA synthesis, as demonstrated by inhibition of IGF actions with specific antibodies. Cell surface associated IGF BPs bound more radiolabeled IGF than IGF receptors, as determined by binding studies and affinity cross-linking. IGF I and IGF II appeared to regulate production of IGF BP2, suggesting that the IGFs may regulate their own actions by altering the abundance of their binding proteins.