Human fetal ovaries and uteri: developmental expression of genes encoding the insulin, insulin-like growth factor I, and insulin-like growth factor II receptors

Plasma Insulin Concentration in Newborns and Children and Age at Menarche

OBJECTIVE

To investigate the association of plasma insulin levels and their trajectories from birth to childhood with the timing of menarche.

RESEARCH DESIGN AND METHODS

This prospective study included 458 girls recruited at birth between 1998 and 2011 and followed prospectively at the Boston Medical Center. Plasma nonfasting insulin concentrations were measured at two time points: at birth (cord blood) and in childhood (age 0.5-5 years). Age at menarche was obtained from a pubertal developmental questionnaire or abstracted from electronic medical records.

RESULTS

Three hundred six (67%) of the girls had reached menarche. The median (range) age at menarche was 12.4 (9-15) years. Elevated plasma insulin concentrations at birth (n = 391) and in childhood (n = 335) were each associated with an earlier mean age at menarche: approximately 2 months earlier per doubling of insulin concentration (mean shift, -1.95 months, 95% CI, -0.33 to -3.53, and -2.07 months, 95% CI, -0.48 to -3.65, respectively). Girls with overweight or obesity in addition to elevated insulin attained menarche about 11-17 months earlier, on average, than those with normal weight and low insulin. Considering longitudinal trajectories (n = 268), having high insulin levels both at birth and in childhood was associated with a roughly 6 months earlier mean age at menarche (mean shift, -6.25 months, 95% CI, -0.38 to -11.88), compared with having consistently low insulin levels at both time points.

CONCLUSIONS

Our data showed that elevated insulin concentrations in early life, especially in conjunction with overweight or obesity, contribute to the earlier onset of menarche, suggesting the need for early screening and intervention.

Pathophysiology of polycystic ovary syndrome revisited: Current understanding and perspectives regarding future research

Background

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder among reproductive‐age women and has lifelong effects on health.

Methods

In this review, I discuss the pathophysiology of PCOS. First, I summarize our current understanding of the etiology and pathology of PCOS, then, discuss details of two representative environmental factors involved in the pathogenesis of PCOS. Finally, I present perspectives regarding the directions of future research.

Main findings

The pathophysiology of PCOS is heterogeneous and shaped by the interaction of reproductive dysfunction and metabolic disorders. Hyperandrogenism and insulin resistance exacerbate one another during the development of PCOS, which is also affected by dysfunction of the hypothalamus‐pituitary‐ovarian axis. PCOS is a highly heritable disorder, and exposure to certain environmental factors causes individuals with predisposing genetic factors to develop PCOS. The environmental factors that drive the development of PCOS pathophysiology make a larger contribution than the genetic factors, and may include the intrauterine environment during the prenatal period, the follicular microenvironment, and lifestyle after birth.

Conclusion

On the basis of this current understanding, three areas are proposed to be subjects for future research, with the ultimate goals of developing therapeutic and preventive strategies and providing appropriate lifelong management, including preconception care.

Roles of insulin-like growth factor II in regulating female reproductive physiology

The number of growth factors involved in female fertility has been extensively studied, but reluctance to add essential growth factors in culture media has limited progress in optimizing embryonic growth and implantation outcomes, a situation that has ultimately led to reduced pregnancy outcomes. Insulin-like growth factor II (IGF-II) is the most intricately regulated of all known reproduction-related growth factors characterized to date, and is perhaps the predominant growth factor in human ovarian follicles. This review aims to concisely summarize what is known about the role of IGF-II in follicular development, oocyte maturation, embryonic development, implantation success, placentation, fetal growth, and in reducing placental cell apoptosis, as well as present strategies that use growth factors in culture systems to improve the developmental potential of oocytes and embryos in different species. Synthesizing the present knowledge about the physiological roles of IGF-II in follicular development, oocyte maturation, and early embryonic development should, on the one hand, deepen our overall understanding of the potential beneficial effects of growth factors in female reproduction and on the other hand support development (optimization) of improved outcomes for assisted reproductive technologies.

Growth Hormone and Endometrial Receptivity

Administration of growth hormone (GH) during ovarian stimulation has shown beneficial effects on in vitro fertilization (IVF) outcomes. It is generally believed that this improvement is due to the stimulating effect of GH on oocyte quality. However, studies are emerging that show possible positive effect of GH administration on endometrial receptivity, thus suggesting an additional potential benefit at the level of the uterus, especially among women with recurrent implantation failure, thin endometrium, and older normal responders. This review summarizes recent data on GH co-treatment effects on endometrium and endometrial receptivity among infertile women undergoing IVF, and proposes possible mechanisms of GH actions in the endometrium.

Is foetal hyperexposure to androgens a cause of PCOS?

BACKGROUND

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy affecting reproductive-aged women. The pathophysiology of this syndrome is still not completely understood but recent evidence suggests that the intra-uterine environment may be a key factor in the pathogenesis of PCOS, in particular, hyperexposure of the foetus to androgens. High concentrations of maternal serum testosterone during pregnancy have been shown to influence behaviour during childhood, the prevalence of autism disorders and anti-Mullerian hormone (AMH) concentrations in adolescence. They are also thought to re-programme the female reproductive axis to induce the features of PCOS in later life: oligo/anovulation, polycystic ovaries, hyperandrogenism and insulin resistance (IR). Support for this developmental theory for the aetiology of PCOS is gathering momentum, following results from first animal studies and now human data, which lend credence to many aspects of this hypothesis.

OBJECTIVE AND RATIONALE

In this review the recent available evidence is presented to support the hypothesis that hyperandrogenic changes in the intra-uterine environment could play a major part in the aetiological basis of PCOS.

SEARCH METHODS

An extensive PubMED and MEDline database search was conducted. Relevant studies were identified using a combination of search terms: 'polycystic ovary syndrome', 'PCOS', 'aetiology', 'anti-Mullerian hormone', 'AMH', 'pathogenesis', 'kisspeptin', 'hyperandrogenism', 'insulin resistance', 'metabolic factors', 'placenta', 'developmental hypothesis', 'genetic and epigenetic origins'.

OUTCOMES

A total of 82 studies were finally included in this review. There is robust evidence that a hyperandrogenic intra-uterine environment 'programmes' the genes concerned with ovarian steroidogenesis, insulin metabolism, gonadotrophin secretion and ovarian follicle development resulting in the development of PCOS in adult life.

WIDER IMPLICATIONS

Once the evidence supporting this hypothesis has been expanded by additional studies, the door would be open to find innovative treatments and preventative measures for this very prevalent condition. Such measures could considerably ease the human and economic burden that PCOS creates.

Intrauterine environment and polycystic ovary syndrome

The maternal-fetal environment plays an important role in developmental programming of adult disease. Metabolic and hormonal dysfunction during human fetal development accompanies gestational diabetes as a common occurrence in mothers with polycystic ovary syndrome (PCOS), while human fetal androgen excess from congenital adrenal hyperplasia or virilizing tumors precedes PCOS-like symptoms after birth. To date, clinical studies of infant blood levels at term have yet to confirm that human fetal androgen excess promotes PCOS development after birth. Earlier in development, however, circulating androgen levels in the second trimester female human fetus can normally rise into the male range. Furthermore, midgestational amniotic testosterone levels are elevated in female fetuses of PCOS compared with normal mothers and might influence fetal development because experimentally induced fetal androgen excess in animals produces a PCOS-like phenotype with reproductive and metabolic dysfunction. Such alterations in the maternal-fetal environment likely program adult PCOS by epigenetic modifications of genetic susceptibility of the fetus to PCOS after birth. Understanding this phenomenon requires advanced fetal surveillance technologies and postnatal assessment of midgestational androgen exposure for new clinical strategies to improve reproduction in PCOS women, optimize long-term health of their offspring, and minimize susceptibility to acquiring PCOS in future generations.

Polycystic ovary syndrome and its developmental origins

The prenatal testosterone (T)-treated adult female rhesus monkey is one animal model of polycystic ovary syndrome (PCOS) in women, with early prenatal T excess programming a permanent PCOS-like phenotype characterized by luteinizing hormone (LH) hypersecretion from reduced hypothalamic sensitivity to steroid negative feedback and relative insulin excess from increased abdominal adiposity. These combined reproductive and metabolic abnormalities are associated with ovarian hyperandrogenism and follicular arrest in adulthood, as well as premature follicle differentiation and impaired embryo development during gonadotropin therapy for in vitro fertilization (IVF). A second animal model for PCOS, the prenatal T-treated sheep also is characterized by LH hypersecretion from reduced hypothalamic sensitivity to steroid negative feedback, persistent follicles and insulin resistance, but also is associated with intrauterine growth retardation and compensatory growth after birth. The ability of prenatal T excess in both species to alter the developmental trajectory of multiple organ systems in utero provides evidence that the hormonal environment of intrauterine life programs target tissue differentiation, raising the possibility that T excess in human fetal development promotes PCOS in adulthood. Such a hypothesis must include data from clinical studies of PCOS women to clarify the homology between these PCOS-like animal models and PCOS per se in reproductive and metabolic function. Future studies should develop new clinical strategies that improve pregnancy outcome and minimize pregnancy loss in women with disorders of insulin action, including PCOS, obesity and diabetes mellitus as well as minimize transgenerational susceptibility to adult PCOS and its metabolic derangements in male close relatives.

Early origins of polycystic ovary syndrome

The prenatally androgenised female rhesus monkey has become a model for polycystic ovary syndrome (PCOS) in women, with early prenatal androgenisation entraining a permanent PCOS-like phenotype characterised by luteinising hormone (LH) hypersecretion due to reduced hypothalamic sensitivity to steroid negative feedback and relative insulin excess associated with increased abdominal adiposity. These combined reproductive and metabolic abnormalities occur in combination with ovarian hyperandrogenism and follicular arrest in adulthood, and with premature follicle differentiation and impaired embryo development during gonadotrophin therapy for in vitro fertilization (IVF). The ability of prenatal androgen excess in fetal rhesus monkeys to entrain multiple organ systems in utero provides evidence that the hormonal environment of intrauterine life programmes target tissue differentiation, raising the possibility that hyperandrogenism in human fetal development promotes PCOS in adulthood. This hypothesis developed in prenatally androgenised female rhesus monkeys, however, also must include data from clinical studies of PCOS to clarify the homology between human and non-human primates in intrafollicular steroidogenesis and its impact on oocyte developmental competency. By doing so, future studies promise to develop new clinical strategies that will lead to improved pregnancy outcome and reduced pregnancy loss in women with disorders of insulin action, including PCOS, obesity and diabetes mellitus.

Human fetal ovary development involves the spatiotemporal expression of p450c17 protein

OBJECTIVE

The purpose of this research was to characterize the spatiotemporal expression of P450c17 in the human fetal ovary.

DESIGN

P450c17 protein was visualized in sections of control and anencephalic ovaries using immunohistochemistry.

SUBJECTS

Subjects included control (nonanencephalic) and anencephalic human fetal ovaries during the second and third trimesters.

RESULTS

In second-trimester control ovaries, P450c17 was highly expressed in primary interstitial cells (PIC) located between the ovigerous cords near the cortical-medullary border where meiosis and primordial follicle formation were occurring. Morphometric analysis revealed a progressive decrease in the number of PIC during the second trimester, suggesting that PIC might have a finite lifetime. Between 25 and 32 wk, relatively few cells stained positive for P450c17; however, after 33 wk, P450c17 was strongly expressed in theca interstitial cells (TIC) bordering developing follicles. Surprisingly, the TIC appeared remarkably early during folliculogenesis, e.g. as early as the primary-to-secondary transition, and exhibited notable hyperplasia throughout preantral and early antral follicle growth. Owing to large numbers of developing preantral follicles, the third trimester was characterized by an increased abundance of P450c17-positive TIC. During this time period, P450c17 was strongly expressed in the hilus interstitial cells juxtaposed to the rete ovarii. Studies of ovaries of anencephalic fetuses revealed a similar spatiotemporal pattern of P450c17 expression in the PIC, TIC, and hilus interstitial cells, consistent with the possibility that pituitary hormones may not be involved in P450c17 expression in fetal ovaries.

CONCLUSION

We identified three different classes of P450c17-expressing interstitial cells in the human fetal ovary, each having a different spatiotemporal pattern of P450c17 expression and, presumably, a different set of physiological functions.

Immunohistochemical localization of the growth hormone in human endometrium and decidua

PROBLEM

Recent evidence of growth hormone (GH) receptor expression in rat endometrium and human myometrium have focused our attention on the role of the GH in endometrial development. We tested the expression of GH in the human endometrium throughout the menstrual cycle and during pregnancy.

METHOD OF STUDY

Immunohistochemical study was performed on endometrial specimens of fertile women in different periods of the menstrual cycle and in decidua of pregnant women.

RESULTS

Glandular cells of the human endometrium were positive for GH in the mid and late luteal phase. Furthermore, the glandular cells of decidua showed intense staining for GH, while the stromal cells were negative. No immunostaining was expressed in the proliferative or early luteal phase. The intensity levels of staining for GH in decidual specimens were significantly higher than in glandular cells of secretory endometrium specimens (P < 0.01).

CONCLUSIONS

The glandular cells of the human endometrium express GH from the late luteal phase throughout pregnancy in the decidual tissue. We suppose that GH plays an important role in blastocyst implantation.

Expression of transforming growth factor (TGF)-beta1, TGF-beta2, and TGF-beta3 and of type I and II TGF-beta receptors during the development of the human fetal ovary

OBJECTIVE

To investigate the role of transforming growth factor-beta (TGF-beta) in the regulation of human fetal ovarian development.

DESIGN

Reverse transcription-polymerase chain reaction and comparative immunohistochemical analysis of the localization and staining intensity of TGF-beta1, TGF-beta2, and TGF-beta3, and of their receptors.

SETTING

Academic research environment.

PATIENT(S)

Human fetal ovaries were obtained from terminated normal intact pregnancies at 11-24 weeks' gestation.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Messenger RNA analysis and protein expression of TGF-beta isoforms and their receptors in human fetal ovaries at 11-24 weeks of gestational age.

RESULT(S)

Messenger RNAs for the three TGF-beta isoforms and the two TGF-beta receptors were demonstrated in all the developmental ages studied: 11, 14, 18, 20, and 22 weeks of gestation. During the first trimester, immunohistochemical analysis for TGF-beta1, TGF-beta2, and TGF-beta receptor type I revealed homogeneous light staining of the ovary. Staining for TGF-beta3 and TGF-beta receptor type II was predominantly in the oocytes. During the second trimester, staining for all three TGF-beta isoforms and both receptors was predominantly in the oocytes. In addition, for receptor types I and II, staining was observed in the pregranulosa cells.

CONCLUSION(S)

Our findings support the hypothesis that expression of the TGF-beta system changes from the first to the second trimester of fetal development and may have an autocrine and/or paracrine regulatory role during ovarian development.

Developmental expression of insulin-like growth factor II receptor (IGF-IIR) in congenic mouse embryonic lungs: correlation between IGF-IIR mRNA and protein levels and heterochronic lung development

Embryonic lung maturation in the H-2 congenic pair, B10.A and B10, proceeds at different rates. The dependence of this heterochronic development on maternal haplotype suggests the involvement of a parentally imprinted gene. Since B10.A (H-2a) and B10 (H-2b) mice are genetically identical except for a 3-18 cM region of chromosome 17 that includes the H-2 complex, we sought a promising candidate gene(s) involved in regulating the rate of lung development from genes encoded in this region. The best candidate is the gene encoding the type II insulin-like growth factor receptor (IGF-IIR), whose ligand is the growth factor IGF-II. Only the maternal copy of this gene is expressed in postimplantation embryos. This receptor does not appear to transduce mitogenic signals; instead, IGF-IIR appears to regulate the levels of its ligand available to the growth-promoting type I IGF receptor (IGF-IR). Using in situ hybridization and indirect immunofluorescence, we demonstrate that IGF-IIR mRNA and protein are localized throughout the pulmonary mesenchyme, as well as in branching epithelia of the pseudoglandular and canalicular stages. We also examined the levels of IGF-IIR mRNA and protein expression by RNase protection assay and ligand blotting during the embryonic period of lung development in B10.A and B10 mice, and found that there is a highly significant positive correlation of IGF-IIR levels with progressive development in both strains. Further, slower-developing B10.A lungs contain significantly higher levels of IGF-IIR mRNA and protein than the more rapidly developing B10 lungs. These results suggest that haplotype-dependent elevation of IGF-IIR levels reduces the available concentration of IGF-II, resulting in a decreased rate of morphogenesis in B10.A mice. Heterochronic lung maturation, then, appears consequent to variable extracellular levels of this important growth factor. These results may be of clinical importance to predicting susceptibility to Respiratory Distress Syndrome in prenatal newborns.

Establishment of a rat thyroid carcinoma cell line in vitro demonstrating high DNA synthesis in response to insulin-like growth factor I

We previously established transplantable rat thyroid carcinoma cell lines in vivo from primary thyroid tumors induced by N-bis-(2-hydroxypropyl)nitrosamine (DHPN). In the present study, an insulin-like growth factor I (IGF-I)-responsive cell line (TRTC-G1-C-A4) in culture was derived from one (well differentiated papillary type) of these carcinoma cell lines G1. TRTC-G1-C-A4 cells were found to exhibit specific saturable binding of IGF-I with a Kd of 1.16 nM at approximately 43.6 fmol/10(5) cells. Inclusion of IGF-I (10 and 50 ng/ml) in the culture medium resulted in a significant increase of [3H]thymidine incorporation and marked cell proliferation. IGF-II (10 ng/ml) and insulin (1 microgram) produced no such effects. The molecular weight of IGF-I receptors on the cell membrane was determined by Western blotting analysis, a single band of binding proteins with a molecular weight of 125 kDa being evident under non-reducing conditions. Reverse transcriptase polymerase chain reaction (RT-PCR) showed that the TRTC-G1-C-A4 cells contained IGF-I receptor mRNA with a sequence corresponding to that determined from rat uterus. These results demonstrate that the IGF-I receptor can be expressed in a thyroid carcinoma with an important contribution to cell growth.

Localization and timing of appearance of insulin, insulin-like growth factor-I, and their receptors in the human fetal müllerian tract

OBJECTIVE

The factors that regulate fetal müllerian tract development are still unknown. Insulin and insulin-like growth factor-I are peptides postulated to serve as autocrine or paracrine regulators of cell activity. We have previously demonstrated that messenger ribonucleic acid for insulin and insulin-like growth factor-I receptors are expressed in fetal uterine tissues. We undertook this study to determine by immunohistochemical techniques the exact location of these two growth factors and their receptors in the human fetal uterus.

STUDY DESIGN

We obtained freshly discarded human fetal uteri (n = 12) between 15 and 22 weeks of gestation from elective pregnancy terminations. Frozen-section specimens were incubated with antibodies against insulin, insulin-like growth factor-I, insulin receptor, and insulin-like growth factor-I receptor. These sections were then incubated with a second antibody conjugated to fluorescein isothiocyanate and examined under phase and fluorescent microscopy.

RESULTS

The fetal endometrium at 19 and 22 weeks of gestation contained insulin, insulin-like growth factor-I, insulin receptor, and insulin-like growth factor-I receptor. The distribution of immunofluorescence in the endometrium is similar for both insulin and its receptor. The same pattern of immunostaining was likewise demonstrated for insulin-like growth factor-I and its receptor.

CONCLUSION

The localization of these growth factors and their receptors, combined with our previous messenger ribonucleic acid data, suggest an autocrine or paracrine role for insulin and insulin-like growth factor-I in the developing human fetal müllerian tract.