Regulation of secondary follicle growth by theca cells and insulin-like growth factor 1

Growth factors and female reproduction in vertebrates

Female reproductive efficiency is influenced by the outcomes of various processes, including folliculogenesis, apoptosis, response to gonadotropin signaling, oocyte maturation, and ovulation. The role of hormones in regulating these processes and other reproductive activities has been well established. It is becoming increasingly evident that in addition to well-characterized hormones, growth factors play vital roles in regulating some of these reproductive activities. Growth factors and their receptors are widely distributed in vertebrate ovaries at different stages of ovarian development, indicating their involvement in intraovarian reproductive functions. In the ovary, cell surface receptors allow growth factors to regulate intraovarian reproductive activities. Understanding these actions in the reproductive axis would provide a tool to target growth factors and/or their receptors to yield desirable reproductive outcomes. These include enrichment of in vitro maturation and fertilization culture media, and management of infertility. This review discusses some widely characterized growth factors belonging to the TGF, EGF, IGF, FGF, and BDNF family of peptides and their role in female reproduction in vertebrates, with a focus on mammals.

Duodenogastric Intussusception in a 14-Week-Old Infant with Donohue Syndrome: Case Study

Donohue syndrome (DS) is a rare recessively inherited disorder characterized by severe insulin resistance caused by genetic defects affecting the insulin receptor. The classical clinical characteristics include severe intrauterine growth restriction, craniofacial dysmorphic features, body and skin features, and soft tissue overgrowth. Postnatal growth retardation, cardiac, gastrointestinal, and renal complications, and infection susceptibility develop within the first few months of life, leading to a short life expectancy (<2 years). The classical metabolic abnormalities vary from fasting hypoglycemia to postprandial hyperglycemia with severe hyperinsulinemia. We present the case of a 14-week-old infant with DS who developed cardiac, renal, hepatic, pancreatic, and gastrointestinal features, all of them previously reported in infants with DS. The gastrointestinal features started during the first week of life and included abdominal distension, feeding difficulties, intermittent vomiting, and two episodes of intestinal obstruction. The diagnosis of duodenogastric intussusception was made, and this previously unreported complication tragically resulted in mortality. We discuss how basic mechanisms of cross-talk between insulin and insulin-growth factor 1 receptors could be linked to hyperinsulinemia and its associated comorbidities.

hUMSC transplantation restores follicle development in ovary damaged mice via re-establish extracellular matrix (ECM) components

OBJECTIVES

Explore the therapeutic role of human umbilical mesenchymal stem cells (hUMSCs) transplantation for regeneration of ECM components and restoration of follicular development in mice.

BACKGROUND

The extracellular matrix (ECM) is crucial to maintain ovary function and regulate follicular development, as it participates in important cell signaling and provides physical support to the cells. However, it is unknown how hUMSCs affect the expression of ECM-related genes in ovaries treated with cyclophosphamide (CTX) and busulfan (BUS).

METHODS

In the present study, we used 64 six- to eight-week-old ICR female mice to established mouse model. The mice were randomly divided into four groups (n = 16/group): control, POI, POI + hUMSCs, and POI + PBS group. The premature ovarian insufficiency (POI) mouse model was established by intraperitoneal injection of CTX and BUS for 7days, then, hUMSCs or PBS were respectively injected via the tail vein in POI + hUMSCs or POI + PBS group. Another 7days after injection, the mice were sacrificed to harvest the ovary tissue. The ovaries were immediately frozen with liquid nitrogen or fixed with 4% PFA for subsequent experiments. To screen differentially expressed genes (DEGs), we performed transcriptome sequencing of ovaries. Thereafter, a Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to predict the related biological functions. Retrieval of interacting genes for ECM-related DEGs was performed using the function of STRINGdb (version 2.6.5) to evaluate potential protein-protein interaction (PPI) networks. Furthermore, qRT-PCR and IHC were performed to assess the differential expression of selected DEGs in control, damaged, hUMSCs-transplanted and non-transplanted ovaries.

RESULTS

Chemotherapy caused mouse ovarian follicular reserve depletion, and hUMSCs transplantation partially restored follicular development. Our results revealed that ECM-receptor interaction and ECM organization were both downregulated in the damaged ovaries. Further investigation showed that ECM-related genes were downregulated in the CTX and BUS treatment group and partially rescued in hUMSCs injection group but not in the PBS group. qRT-PCR and IHC verified the results: collagen IV and laminin gamma 3 were both expressed around follicle regions in normal ovaries, chemotherapy treatment disrupted their expression, and hUMSCs transplantation rescued their localization and expression to some extent.

CONCLUSION

Our data demonstrated that ECM-related genes participate in the regulation of ovarian reserve, hUMSCs treatment rescued abnormal expression and localization of collagen IV and laminin gamma 3 in the damaged ovaries. The results suggest that hUMSCs transplantation can maintain ECM-stable microenvironments, which is beneficial to follicular development.

Squeezing the eggs to grow: The mechanobiology of mammalian folliculogenesis

The formation of functional eggs (oocyte) in ovarian follicles is arguably one of the most important events in early mammalian development since the oocytes provide the bulk genetic and cytoplasmic materials for successful reproduction. While past studies have identified many genes that are critical to normal ovarian development and function, recent studies have highlighted the role of mechanical force in shaping folliculogenesis. In this review, we discuss the underlying mechanobiological principles and the force-generating cellular structures and extracellular matrix that control the various stages of follicle development. We also highlight emerging techniques that allow for the quantification of mechanical interactions and follicular dynamics during development, and propose new directions for future studies in the field. We hope this review will provide a timely and useful framework for future understanding of mechano-signalling pathways in reproductive biology and diseases.

Effects of IGF-1 on the Three-Dimensional Culture of Ovarian Preantral Follicles and Superovulation Rates in Mice

Insulin-like growth factor-1 (IGF-1) plays a crucial role during folliculogenesis, which has been demonstrated by previous research. However, the optimal IGF-1 dosage in the three-dimensional (3D) culture system is unknown. Mouse secondary follicles (140−150 µm) were cultured for 6 days within an alginate bead in a medium supplemented with 0 (G0), 5 ng/mL (G5), 10 ng/mL (G10), or 50 ng/mL IGF-1 (G50). Secretions of 17β-estradiol and progesterone were significantly increased in G10 and G50 (p < 0.05). However, G50 significantly inhibited follicular growth (p < 0.05), while G10 showed a higher oocyte maturation rate. Thus, the 10 ng/mL IGF-1 was used in subsequent experiments. IGF-1 enhanced the function of granulosa cells (GCs) by upregulating expressions of Star, Cyp19a1, Hsd3b1, Fshr, and Lhcgr. Oocyte secretory function was promoted by upregulating expressions of Bmp-15, Gdf-9, and Fgf-8. Addition of IGF-1 showed anti-apoptotic effect. However, G10 did not improve fertilization rate of MII oocytes compared to G0. In an intraperitoneal injection experiment in mice, IGF-1 significantly increased the number of ovulated oocytes (p < 0.05). In conclusion, 10 ng/mL IGF-1 can promote the production of mature oocytes in the 3D culture medium and injection of IGF-1 before superovulation increases the number of ovulated oocytes.

Therapeutic Potential of In Vitro-Derived Oocytes for the Restoration and Treatment of Female Fertility

Considerable progress has been made with the development of culture systems for the in vitro growth and maturation (IVGM) of oocytes from the earliest-staged primordial follicles and from the more advanced secondary follicles in rodents, ruminants, nonhuman primates, and humans. Successful oocyte production in vitro depends on the development of a dynamic culture strategy that replicates the follicular microenvironment required for oocyte activation and to support oocyte growth and maturation in vivo while enabling the coordinated and timely acquisition of oocyte developmental competence. Significant heterogeneity exists between the culture protocols used for different stages of follicle development and for different species. To date, the fertile potential of IVGM oocytes derived from primordial follicles has been realized only in mice. Although many technical challenges remain, significant advances have been made, and there is an increasing consensus that complete IVGM will require a dynamic, multiphase culture approach. The production of healthy offspring from in vitro-produced oocytes in a secondary large animal species is a vital next step before IVGM can be tested for therapeutic use in humans.

Growth hormone in fertility and infertility: Mechanisms of action and clinical applications

Secreted by the anterior pituitary gland, growth hormone (GH) is a peptide that plays a critical role in regulating cell growth, development, and metabolism in multiple targeted tissues. Studies have shown that GH and its functional receptor are also expressed in the female reproductive system, including the ovaries and uterus. The experimental data suggest putative roles for GH and insulin-like growth factor 1 (IGF-1, induced by GH activity) signaling in the direct control of multiple reproductive functions, including activation of primordial follicles, folliculogenesis, ovarian steroidogenesis, oocyte maturation, and embryo implantation. In addition, GH enhances granulosa cell responsiveness to gonadotropin by upregulating the expression of gonadotropin receptors (follicle-stimulating hormone receptor and luteinizing hormone receptor), indicating crosstalk between this ovarian regulator and the endocrine signaling system. Notably, natural gene mutation of GH and the age-related decline in GH levels may have a detrimental effect on female reproductive function, leading to several reproductive pathologies, such as diminished ovarian reserve, poor ovarian response during assisted reproductive technology (ART), and implantation failure. Association studies using clinical samples showed that mature GH peptide is present in human follicular fluid, and the concentration of GH in this fluid is positively correlated with oocyte quality and the subsequent embryo morphology and cleavage rate. Furthermore, the results obtained from animal experiments and human samples indicate that supplementation with GH in the in vitro culture system increases steroid hormone production, prevents cell apoptosis, and enhances oocyte maturation and embryo quality. The uterine endometrium is another GH target site, as GH promotes endometrial receptivity and pregnancy by facilitating the implantation process, and the targeted depletion of GH receptors in mice results in fewer uterine implantation sites. Although still controversial, the administration of GH during ovarian stimulation alleviates age-related decreases in ART efficiency, including the number of oocytes retrieved, fertilization rate, embryo quality, implantation rate, pregnancy rate, and live birth rate, especially in patients with poor ovarian response and recurrent implantation failure.

Transcriptome analysis reveals that long noncoding RNAs contribute to developmental differences between medium-sized ovarian follicles of Meishan and Duroc sows

Ovulation rate is an extremely important factor affecting litter size in sows. It differs greatly among pig breeds with different genetic backgrounds. Long non-coding RNAs (lncRNAs) can regulate follicle development, granulosa cell growth, and hormone secretion, which in turn can affect sow litter size. In this study, we identified 3554 lncRNAs and 25,491 mRNAs in M2 follicles of Meishan and Duroc sows. The lncRNA sequence and open reading frame lengths were shorter than mRNAs, and lncRNAs had fewer exons, were less abundant, and more conserved than protein-coding RNAs. Furthermore, 201 lncRNAs were differentially expressed (DE) between breeds, and quantitative trait loci analysis of DE lncRNAs were performed. A total of 127 DE lncRNAs were identified in 119 reproduction trait-related loci. In addition, the potential target genes of lncRNAs in cis or trans configurations were predicted. Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed that some potential target genes were involved in follicular development and hormone secretion-related biological processes or pathways, such as progesterone biosynthetic process, estrogen metabolic process, ovarian steroidogenesis, and PI3K-Akt signaling pathway. Furthermore, we also screened 19 differentially expressed lncRNAs in the PI3K-Akt signaling pathway as candidates. This study provides new insights into the roles of lncRNAs in follicular growth and development in pigs.

Human Follicle in vitro Culture Including Activation, Growth, and Maturation: A Review of Research Progress

Fertility preservation has received unprecedented attention nowadays. In addition to cryopreservation and re-implantation of embryos, oocytes, and ovarian tissue pieces, in vitro culture system for follicles/oocytes has been considered as an alternative strategy for fertility preservation. Since the metabolic dynamics and required nutrients are not entirely the same in different stages of follicular development, optimization of each culture step is needed. In this paper, literature regarding culture conditions in three steps were analyzed. Known additives in activation stage included 740Y-P, bpV(HOpic), follicle stimulating hormone (FSH), human serum albumin (HSA), ITS, growth differentiation factor 9 (GDF9), bone morphogenetic protein 15 (BMP15), and cyclic adenosine monophosphate (cAMP), with different degrees of activation promotion and potential detrimental effect on DNA integrity. For isolated follicles growth stage, actin A, FSH, basic fibroblast growth factor (bFGF), estradiol were proved to improve development or proliferation. As for maturation, addition of growth hormone, melatonin, C-type natriuretic peptide (CNP), GDF9, cilostamide, or forskolin helped to regulate maturation rate or improve oocyte quality. Based on previous sequential culture system for human follicles, optimization is needed to achieve higher maturation rate and better oocyte quality, pursuant to current review, which demonstrated the effects of various additives on different stages.

Identification of a New Theca/Interstitial Cell-Specific Gene and Its Biological Role in Growth of Mouse Ovarian Follicles at the Gonadotropin-Independent Stage

Theca/interstitial cells are responsible for the growth and maturation of ovarian follicles. However, little is known about the theca/interstitial cell-specific genes and their functions. In this study, we explored transcriptomes of theca/interstitial cells by RNA-seq, and the novel biological roles of a theca cell marker, asporin (Aspn)/periodontal ligament-associated protein 1 (PLAP-1). RNA-seq detected 432 and 62 genes expressed specifically in theca/interstitial cells and granulosa cells isolated from 3-weeks old mouse ovaries. Gene ontology analysis demonstrated that these genes were largely categorized into four major groups: extracellular matrix organization-related terms, chemotaxis-related terms, the angiogenesis-related terms, and morphogenesis-related terms. In situ hybridization demonstrated that the newly detected representative gene, Aspn/PLAP-1, was detected specifically in the outer layer of theca cells in contrast with the expression of the basal lamina-specific gene, Nidgen-1. Intriguingly, an Aspn/PLAP-1 antibody completely arrested the growth of secondary follicles that is the gonadotropin-independent follicle developmental stage. Furthermore, transforming growth factor-β (TGF-β)-triggered signaling was induced by the Aspn/PLAP-1 antibody treatment, which is consistent with the inhibitory effect of Aspn/PLAP-1 on TGF-β. Altogether, these results suggest that theca cells are classified into subpopulations on the basis of new marker genes and their biological functions, and provide evidence that Aspn/PLAP-1 is expressed exclusively in the outer layer of theca cells and plays a pivotal role in the growth of secondary follicles via downregulation of the canonical TGF-β signaling cascade.

Growth Hormone and Reproduction: Lessons Learned From Animal Models and Clinical Trials

Growth Hormone (GH) has been considered as a therapeutic option to increase the number of growing follicles during Assisted Reproductive Technology (ART) for more than 30 years. In this review the biological rationale for therapeutic GH usage is explained through evidence in animal models, aiming to put this into a clinical context. First, we explain the GH-Insulin like Growth Factor (IGF)-1-gonadal axis and its role in reproduction. Evidence suggests that GH can stimulate the secretion of IGF1 not only in the liver but also in the peripheral target structures, including the ovary. Moreover, IGF-1 can be secreted locally under the influence of stimuli other than GH. In the case of the ovary, steroid hormones, gonadotropins or the combination of both seems to be involved. Even more interesting, the ovary itself can secret GH locally and exert a paracrine action modulating the intracellular signaling pathway of GH, i.e., not by the systemic pathway where GH binds to the extracellular domain of the GH receptor. Finally, these aspects from animal models are put into clinical perspective by discussing results and shortcomings of studies and meta-analyses in order to put forth the state-of-the-art rationale for therapeutic GH usage in modern ART.

The concentration-dependent effect of progesterone on follicle growth in the mouse ovary

Follicle growth in the mammalian ovary is coordinately controlled by multiple factors to sustain periodic ovulation. In this study, we investigated the role of progesterone on follicle growth in the mouse ovary. As the concentration of progesterone changes during the estrus cycle, we cultured the sliced mouse ovary in a medium containing 10 ng/ml, 100 ng/ml, and 1 μg/ml progesterone. Progesterone promoted the growth of primordial to primary follicles at 100 ng/ml, while it suppressed the growth of secondary follicles at 1 μg/ml. Follicles at other developmental stages in the cultured ovary were unaffected with different concentrations of progesterone. The number of ovulated oocytes increased in the medium containing 100 ng/ml progesterone but decreased in the presence of 1 μg/ml progesterone. Follicles expressed two types of progesterone receptors, progesterone receptor (PGR) and PGR membrane component 1 (PGRMC1). While PGR shows transient expression on granulosa cells of Graafian follicles, PGRMC1 expresses in granulosa cells of developing follicles. These results suggest that progesterone controls the growth of developing follicles through PGRMC1. Our study shows that the effect of progesterone on ovulation and follicle growth in mouse ovary is dependent on the concentration of progesterone and the follicle stage.

Observation of the dynamics of follicular development in the ovary

The number of ovulated oocytes is different among mammals but does not vary much within the same species. In order to sustain periodic ovulation, follicular development must be coordinated at the tissue level. Elucidating the regulatory mechanisms of follicular development is difficult because the ovary has a complicated structure and it takes a long time for primordial follicles to develop into Graafian follicles. Therefore, it is not possible to observe follicular development by conventional experiments. The authors previously developed a new ovarian tissue culture method that enabled the observation of follicular development from the early follicle stage. These findings indicated that follicular interactions are important in regulating follicular development and ovulation. This review describes the current methods of observing follicular development in the ovary and the regulatory mechanisms of follicular development.