Regulation of mouse follicle development by follicle-stimulating hormone in a three-dimensional in vitro culture system is dependent on follicle stage and dose

Survival, growth, and maturation of secondary follicles from prepubertal, young, and older adult rhesus monkeys during encapsulated three-dimensional culture: effects of gonadotropins and insulin

A three-dimensional culture system supports the development of primate preantral follicles to the antral stage with appreciable steroid production. This study assessed i) whether in vitro developmental competence of follicles is age dependent, ii) the role of gonadotropins and insulin in supporting folliculogenesis, and iii) anti-Müllerian hormone (AMH) and vascular endothelial growth factor (VEGF) production by growing follicles. Ovaries were obtained from prepubertal, young, and older adult rhesus macaques. Secondary follicles were encapsulated into alginate beads and cultured individually for 40 days in media containing 0.05 or 5  μg/ml insulin, with or without recombinant human (rh) FSH (500  mIU/ml). No follicles survived in the culture without rhFSH. In the presence of rhFSH, survival was lower for follicles from older animals, whereas growth, i.e. follicle diameter, was less by day 40 for follicles from prepubertal animals. The surviving follicles were categorized as no-grow (NG; ≤ 250 μm), slow-grow (SG; 250-500 μm), and fast-grow (FG; ≥ 500  μm) according to their diameters. SG follicles cultured with 5 μg/ml insulin produced more ovarian steroids than those cultured with 0.05  μg/ml insulin by week 5. SG and FG follicles produced more AMH and VEGF than the NG, and levels peaked at weeks 2 and 5 respectively. After 100  ng/ml rh chorionic gonadotropin treatment for 34 h, more healthy oocytes were retrieved from young adults whose follicles were cultured with 5  μg/ml insulin. This culture system offers an opportunity to characterize the endocrine and paracrine function of primate follicles that influence follicle growth and oocyte maturation.

Current achievements and future research directions in ovarian tissue culture, in vitro follicle development and transplantation: implications for fertility preservation

BACKGROUND Female cancer patients are offered 'banking' of gametes before starting fertility-threatening cancer therapy. Transplants of fresh and frozen ovarian tissue between healthy fertile and infertile women have demonstrated the utility of the tissue banked for restoration of endocrine and fertility function. Additional methods, like follicle culture and isolated follicle transplantation, are in development. METHODS Specialist reproductive medicine scientists and clinicians with complementary expertise in ovarian tissue culture and transplantation presented relevant published literature in their field of expertise and also unpublished promising data for discussion. As the major aims were to identify the current gaps prohibiting advancement, to share technical experience and to orient new research, contributors were allowed to provide their opinioned expert views on future research. RESULTS Normal healthy children have been born in cancer survivors after orthotopic transplantation of their cryopreserved ovarian tissue. Longevity of the graft might be optimized by using new vitrification techniques and by promoting rapid revascularization of the graft. For the in vitro culture of follicles, a successive battery of culture methods including the use of defined media, growth factors and three-dimensional extracellular matrix support might overcome growth arrest of the follicles. Molecular methods and immunoassay can evaluate stage of maturation and guide adequate differentiation. Large animals, including non-human primates, are essential working models. CONCLUSIONS Experiments on ovarian tissue from non-human primate models and from consenting fertile and infertile patients benefit from a multidisciplinary approach. The new discipline of oncofertility requires professionalization, multidisciplinarity and mobilization of funding for basic and translational research.

[Oncofertility: a new focus in women health-care...]

Although treatment and survival are the primary focus of health-care patients, with cancer survivors living longer it is now appropriate to consider their quality of life after treatment, including the possibility of becoming parents. There are several options for fertility preservation in cancer patients. Even though most of them are still experimental and their efficacy and reliability have not been determined, especially in women. The most successful alternative for female survivors is embryo cryopreservation, an approach not suitable for many single or virgin women or even possible for prepubertal girls. Reports of live birth after transplantation of human ovarian tissue have reinforced the clinical potential of ovarian tissue banking for fertility preservation. Many exciting studies are underway to improve the efficacy and solve the problems with current fertility preservation strategies, especially for in vitro culture of cryopreserved tissue or follicles. Continuous efforts to improve current strategies and to develop new strategies will benefit many women and children who are facing premature ovarian failure and sterility.

Dynamics of extracellular matrix in ovarian follicles and corpora lutea of mice

Despite the mouse being an important laboratory species, little is known about changes in its extracellular matrix (ECM) during follicle and corpora lutea formation and regression. Follicle development was induced in mice (29 days of age/experimental day 0) by injections of pregnant mare’s serum gonadotrophin on days 0 and 1 and ovulation was induced by injection of human chorionic gonadotrophin on day 2. Ovaries were collected for immunohistochemistry (n=10 per group) on days 0, 2 and 5. Another group was mated and ovaries were examined on day 11 (n=7). Collagen type IV α1 and α2, laminin α1, β1 and γ1 chains, nidogens 1 and 2 and perlecan were present in the follicular basal lamina of all developmental stages. Collagen type XVIII was only found in basal lamina of primordial, primary and some preantral follicles, whereas laminin α2 was only detected in some preantral and antral follicles. The focimatrix, a specialised matrix of the membrana granulosa, contained collagen type IV α1 and α2, laminin α1, β1 and γ1 chains, nidogens 1 and 2, perlecan and collagen type XVIII. In the corpora lutea, staining was restricted to capillary sub-endothelial basal laminas containing collagen type IV α1 and α2, laminin α1, β1 and γ1 chains, nidogens 1 and 2, perlecan and collagen type XVIII. Laminins α4 and α5 were not immunolocalised to any structure in the mouse ovary. The ECM composition of the mouse ovary has similarities to, but also major differences from, other species with respect to nidogens 1 and 2 and perlecan.

A novel two-step strategy for in vitro culture of early-stage ovarian follicles in the mouse

OBJECTIVE

To develop an in vitro strategy to support the growth of early-stage follicles and produce mature oocytes competent for fertilization.

DESIGN

Whole ovaries from 8-day-old mice were cultured for 4 days, and then secondary follicles were isolated and cultured for 12 days in a three-dimensional alginate or fibrin-alginate (FA) hydrogel matrix.

SETTING

University-affiliated laboratory.

ANIMALS

Mice.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURES

Histologic evaluation of follicle development, steroid hormone production, and rates of oocyte maturation, oocyte fertilization, and embryo formation.

RESULT(S)

Culture of 8-day-old mouse ovaries for 4 days resulted in transition of the follicle population from primordial and primary follicles to secondary follicles, similar to that seen in a 12-day-old ovary. Isolated secondary follicles cultured for 12 days showed larger increases in oocyte diameter and more frequent antrum formation and theca cell differentiation in the FA-hydrogel matrix compared with the alginate matrix. Steroid hormone secretion patterns were consistent with the changes in follicle morphology and cell differentiation observed in the cultured follicles. Compared with oocytes from alginate follicle cultures, a greater number of oocytes retrieved from the FA-based follicle cultures progressed to metaphase I, reached metaphase II, and could be fertilized and cleaved to two-cell embryos. The organ culture plus FA-hydrogel follicle culture strategy produced a very high rate of oocyte progression to metaphase II (88 +/- 8.7% [mean +/- SEM]) and formation of two-cell embryos (54 +/- 4%).

CONCLUSION(S)

A strategy combining whole ovary culture of early-stage follicles and subsequent FA hydrogel in vitro follicle culture produced a high percentage of oocytes competent for fertilization; this might provide new options for fertility preservation in women and prepubertal girls facing fertility-threatening diseases or treatments.

Preserving female fertility following cancer treatment: current options and future possibilities

Children and women of reproductive age are increasingly surviving cancer diagnoses, and therefore long-term quality-of-life issues are of greater importance at the time of diagnosis. Cancer therapies including radiation and chemotherapy can be detrimental to fertility, and therefore many patients are motivated to preserve fertility prior to cancer treatment. The only highly successful method in preserving fertility to date is embryo cryopreservation, which may not be appropriate for some patients due to age, delay in treatment, cancer type and stage, as well as availability of an acceptable sperm donor. Alternative methods including oocyte cryopreservation and ovarian tissue banking may also preserve fertility while providing additional flexibility to patients. In vitro ovarian follicle maturation following tissue banking is one potential approach that would not require a delay in cancer therapy for ovarian stimulation, would not require an immediate sperm donor, and does not carry the risk of reintroducing malignant cells following tissue transplantation. In vitro follicle culture systems have resulted in successful live births in the mouse. However, many challenges must be addressed in translating the system to the human. This review summarizes current approaches to fertility preservation and discusses recent developments and future challenges in developing a human in vitro follicle culture system.

Three-dimensional ovarian organ culture as a tool to study normal ovarian surface epithelial wound repair

Ovarian cancers are primarily derived from a single layer of epithelial cells surrounding the ovary, the ovarian surface epithelium (OSE). Ovarian surface proliferation is associated with ovulation and has been suggested to play a role in ovarian surface transformation and cancer progression. Aspects of ovarian surface repair after ovulation include proliferation, migration, and surface regeneration. To study ovarian surface repair, an organ culture system was developed that supports the proliferation, encapsulation, and repair of an artificially wounded surface. Wounded mouse ovaries embedded into an alginate hydrogel matrix have normal OSE cells as demonstrated by expression of cytokeratin 8, vimentin, N-cadherin, and a lack of E-cadherin. Normal OSE cells began proliferating and migrating around wounded surfaces after 1 d of culture. Organ cultures were propagated in medium supplemented with BSA and fetal bovine serum to determine optimal growth conditions. BSA cultured organs had OSE that proliferated significantly more than controls until d 4, whereas fetal bovine serum cultured organs had significantly more surface area encapsulated by OSE. Overall, a three-dimensional ovarian organ culture supports the growth of normal OSE in response to artificial wounding and provides a novel system for investigating wound repair as it relates to the possible role of ovulation and ovarian cancer.

Interaction between ascorbic acid and follicle-stimulating hormone maintains follicular viability after long-term in vitro culture of caprine preantral follicles

This study evaluates the effects of ascorbic acid and its interaction with follicle-stimulating hormone (FSH) on the morphology, activation, and in vitro growth of caprine preantral follicles. Ovarian fragments were cultured for 1, 7, or 14 d in minimum essential medium (MEM) containing ascorbic acid (50 or 100microg/mL), FSH (50ng/mL), or both of these substances. Ovarian tissue that was either fresh (control) or cultured for 1, 7, or 14 d was processed for histological and ultrastructural evaluation. The results showed that after 14 d of culture, medium supplemented with 50microg/mL of ascorbic acid alone or combined with FSH showed higher rates of follicular survival compared with MEM. After 7 d of culture, FSH, ascorbic acid at 50microg/mL with or without FSH, and ascorbic acid at 100microg/mL increased the percentage of follicular activation compared to fresh control. In addition, FSH alone significantly increased the percentage of growing follicles after 14 d. The combination of 50microg/mL of ascorbic acid and FSH promoted a significant increase in oocyte and follicular diameter after 7 d of culture. Ultrastructural and fluorescent analysis confirmed the integrity of follicles cultured with 50microg/mL of ascorbic acid and FSH after 14 d. In conclusion, the combination of 50microg/mL of ascorbic acid and FSH maintained follicular integrity and promoted follicular activation and growth after long-term in vitro culture of caprine preantral follicles.

Interpenetrating fibrin-alginate matrices for in vitro ovarian follicle development

In this report, we investigate the fibrin-alginate interpenetrating network (FA-IPN) to provide dynamic cell-responsive mechanical properties, which we apply to the in vitro growth of ovarian follicles. The mechanical properties and polymerization rate of the gels were investigated by rheology, and the fiber structure was imaged by electron microscopy. Using a mouse model, two-layered secondary follicles were encapsulated in FA-IPNs, and growth, morphology, hormone production, fibrin degradation rate and the numbers of competent eggs were assessed. The initial mechanics of the FA-IPN are determined by the composite material, and subsequent degradation of fibrin by the encapsulated cells would produce a material with mechanical properties due to the alginate alone. The rate of meiotically competent oocytes produced by culture in FA-IPN was 82%, which was significantly greater than in alginate alone. This increase in oocyte quality is an important step in identifying 3D culture systems that can provide a fundamental tool to investigate follicle maturation, and may be applied to promote the growth of human follicles, which can be used to provide reproductive options for women facing a cancer diagnosis.

In vitro grown human ovarian follicles from cancer patients support oocyte growth

BACKGROUND

Young female adult and adolescent cancer patients facing life-preserving but fertility-threatening chemo- or radiation-therapy are increasingly seeking options to protect their reproductive potential. Ovarian tissue cryopreservation with transplantation is a promising technique to safeguard fertility in cancer patients. However, this method may risk re-introduction of the original cancer to the survivor of the disease. Thus, developing a method for in vitro growth of immature follicles may provide a method for fertility restoration in the future.

METHODS

Human secondary follicles were isolated from ovarian tissues obtained from cancer patients and grown in vitro within a bio-engineered culture system for 30 days.

RESULTS

Human ovarian follicles became steroidogenically active, and developed from the early secondary to antral stage in vitro. The follicles contained healthy, growing oocytes that were connected by transzonal projections between the somatic cells and oocyte.

CONCLUSIONS

Our data support the notion that human follicle development can be achieved in vitro in a bio-engineered culture system. More studies are required to investigate whether the fully sized oocytes obtained from in vitro grown follicle are competent to resume meiosis and be fertilized.

The mouse follicle microenvironment regulates antrum formation and steroid production: alterations in gene expression profiles

Folliculogenesis is a coordinated process, and the genes that regulate development are difficult to investigate in vivo. In vitro culture systems permit the assessment of individual follicles during development, thereby enabling gene expression patterns to be monitored during follicle development. Mouse multilayered secondary follicles (150-180 microm in diameter) were cultured in three-dimensional matrices of varying physical properties for up to 8 days. During this period of follicle growth in vitro, antrum formation and steroid production were monitored, and mRNA was isolated. The expression levels of genes (Star, Cyp11a1, Cyp17a1, Hsd3b1, Cyp19a1, Fshr, Lhcgr, Aqp7, Aqp8, Aqp9, and Hif1a) were measured and correlated to follicle developmental status. Follicles that developed an antrum and produced appropriate levels of estrogen and progesterone had unchanging expression of Star, Aqp7, Aqp8, and Hif1a and a 34-fold increase in Cyp19a1 expression at Day 8 of culture and had elevated Lhcgr at Days 6 and 8 of culture. Follicles that were healthy but did not form an antrum or produce appropriate levels of steroids, however, demonstrated increasing levels of Star, Aqp7, Aqp8, and Hif1a and a 15-fold increase in Cyp19a1 at Day 8 of culture, and Lhcgr levels were not elevated until Day 8 of culture. To our knowledge, this study provides the first temporal analysis of gene expression using individual culture in alginate hydrogels that correlates growth and steroidogenesis during follicle development and identifies expression patterns in healthy follicles and in developmentally disadvantaged follicles.

Effect of cell shape and packing density on granulosa cell proliferation and formation of multiple layers during early follicle development in the ovary

The postnatal mouse ovary is rich in quiescent and early-growing oocytes, each one surrounded by a layer of somatic granulosa cells (GCs) on a basal lamina. As oocytes start to grow the GCs change shape from flattened to cuboidal, increase their proliferation and form multiple layers, providing a unique model for studying the relationship between cell shape, proliferation and multilayering within the context of two different intercommunicating cell types: somatic and germ cells. Proliferation of GCs was quantified using immunohistochemistry for Ki67 and demonstrated that, unusually, cuboidal cells divided more than flat cells. As a second layer of GCs started to appear, cells on the basal lamina reached maximum packing density and the axes of their mitoses became perpendicular to the basal lamina, resulting in cells dividing inwards to form second and subsequent layers. Proliferation of basal GCs was less than that of inner cells. Ultrastructurally, collagen fibrils outside the basal lamina became more numerous as follicles developed. We propose that the basement membrane and/or theca cells that surround the follicle provide an important confinement for rapidly dividing columnar cells so that they attain maximum packing density, which restricts lateral mitosis and promotes inwardly oriented cell divisions and subsequent multilayering.

Cryopreservation/transplantation of ovarian tissue and in vitro maturation of follicles and oocytes: challenges for fertility preservation

Cryopreservation of ovarian tissue and in vitro follicle maturation are two emerging techniques for fertility preservation, especially in cancer patients. These treatment regimes are opening up more options and allow for more suitable choices to preserve fertility according to the patient's specific circumstances. If these technologies are to become widely accepted, they need to be safe, easy to perform and must obtain favorable results. The generation of healthy eggs with the normal genetic complement and the ability to develop into viable and healthy embryos requires tight regulation of oocyte development and maturation. Novel freezing techniques such as vitrification, along with whole ovary cryopreservation and three-dimensional follicle cultures, have shown favorable outcomes. The scope of this article is to take a comprehensively look at the challenges still faced in order for these novel technologies to be routinely employed with the aim of successful fertility preservation.

The effects of different concentrations of sodium selenite on the in vitro maturation of preantral follicles in serum-free and serum supplemented media

PURPOSE

This study was to investigate the effect of sodium selenite (SS) on in vitro maturation of mouse preantral follicles.

METHODS

The isolated preantral follicles were cultured in TCM 199 medium supplemented with different concentrations (0, 5, 10, 15 ng/ml) of SS and 3 mg/ml bovine serum albumin (BSA) or 5% Fetal Bovine Serum (FBS). The ovulation was induced by addition of 1.5 IU/ml human chorionic gonadotropin. The size and development of follicles and oocytes were assessed by calibrated eyepiece.

RESULTS

The survival rates of follicles in FBS supplemented groups containing 5 and 10 ng/ml SS (88.23%, 90.83%) were higher than other groups (P < 0.05 and P < 0.001 respectively). The mean diameter of follicles (199.84 +/- 15.58 microm) and the percentage of MII oocyte (33.08%) were higher in FBS supplemented group containing 10 ng/ml SS (P < 0.001).

CONCLUSION

The sodium selenite and FBS improve the in vitro growth and maturation of mouse preantral follicles.

Essential role of follicle stimulating hormone in the maintenance of caprine preantral follicle viability in vitro

The aims of the present study were to investigate the effects of follicle-stimulating hormone (FSH) on survival, activation and growth of caprine primordial follicles using histological and ultrastructural studies. Pieces of caprine ovarian cortex were cultured for 1 or 7 days in minimum essential medium (MEM - control medium) supplemented with different concentrations of FSH (0, 10, 50 or 100 ng/ml). Small fragments from non-cultured ovarian tissue and from those cultured for 1 or 7 days in a specific medium were processed for classical histology and transmission electron microscopy (TEM). Additionally, effects of FSH on oocyte and follicle diameter of cultured follicles were evaluated. The results showed that the lowest percentage of normal follicles was observed after 7 days of culture in control medium. After 1 day of culture, a higher percentage of growing follicles was observed in the medium supplemented with 50 ng/ml of FSH. In the presence of 10 and 50 ng/ml of FSH, an increase in diameter of both oocyte and follicle on day 7 of culture was observed. TEM showed ultrastructural integrity of follicles after 1 day of culture in MEM and after 7 days in MEM plus 50 ng/ml FSH, but did not confirm the integrity of those follicles cultured for 7 days in MEM. In conclusion, this study demonstrated that FSH at concentration of 50 ng/ml not only maintains the morphological integrity of 7 days cultured caprine preantral follicles, but also stimulate the activation of primordial follicles and the growth of activated follicles.

Expression of growth differentiation factor 9, bone morphogenetic protein 15, and anti-Müllerian hormone in cultured mouse primary follicles

Growth differentiation factor 9 (GDF9), bone morphogenetic protein 15 (BMP15), and anti-Müllerian hormone (AMH) play an important role in the primary to secondary follicle transition and follicle activation in vivo. In organ culture of neonatal mouse ovaries, it was observed that significantly fewer primary follicles develop to the secondary stage. The objectives of this study were: (1) to compare ovarian follicular populations between organ-cultured neonatal mouse ovaries and freshly isolated age-matched control ovaries; (2) to quantify RNA levels of Gdf9, Bmp15, and Amh in cultured primary follicles; and (3) to immunolocalize GDF9 and AMH in cultured ovaries. Ovaries from 3-day-old (PND 3) mice were cultured for 7 or 10 days in the absence or presence of FSH. Follicular populations were counted in freshly isolated 13-day-old (PND 13) ovaries and organ-cultured ovaries. Transcripts were quantified in isolated primary follicles using real-time RT-PCR, and protein expressions were localized using immunohistochemistry. The number of secondary follicles in organ-cultured ovaries was significantly lower than in vivo controls. Gdf9 and Bmp15 mRNA expression levels were similar as in controls. Amh mRNA levels were significantly (P<0.05) lower after day 10 of culture in the absence of FSH. GDF9 and AMH proteins were respectively detected in the oocytes and the granulosa cells (GC) beginning at the primary and primordial stages onward. GDF9 and BMP15 production in cultured primary follicles are not different from in vivo controls; hence abnormal early follicular growth was not related to a deficient transcription of these factors.

The role of the extracellular matrix in ovarian follicle development

Regulation of ovarian follicle development depends on endocrine- and paracrine-acting hormones, the 3-dimensional architecture of the follicle, and the physical rigidity of the surrounding tissue. These 3 forces are integrated throughout the life cycle of the follicle to ensure appropriate hormone secretion, differentiation of the somatic cells, and maturation of the oocyte. The process of in-follicle maturation provides a new tool for understanding ovarian follicle development under the influence of these factors.

Engineering the follicle microenvironment

In vitro ovarian follicle culture provides a tool to investigate folliculogenesis, and may one day provide women with fertility-preservation options. The application of tissue engineering principles to ovarian follicle maturation may enable the creation of controllable microenvironments that will coordinate the growth of the multiple cellular compartments within the follicle. Three-dimensional culture systems can preserve follicle architecture, thereby maintaining critical cell-cell and cell-matrix signaling lost in traditional two-dimensional attached follicle culture systems. Maintaining the follicular structure while manipulating the biochemical and mechanical environment will enable the development of controllable systems to investigate the fundamental biological principles underlying follicle maturation. This review describes recent advances in ovarian follicle culture, and highlights the tissue engineering principles that may be applied to follicle culture, with the ultimate objective of germline preservation for females facing premature infertility.

Physical properties of alginate hydrogels and their effects on in vitro follicle development

The mechanical properties and density of natural and synthetic extracellular matrices are known to affect cellular processes and regulate tissue formation. In this report, these factors were independently investigated for their role in ovarian follicle development. The matrix composition was controlled through decreasing the solids concentration or the molar mass of the encapsulating biomaterial, alginate. Decreasing matrix stiffness and solids concentration enhanced follicle growth and coordinated differentiation of the follicle cell types, as evidenced by antral cavity formation, theca cell differentiation, oocyte maturation, and relative hormone production levels. While a stiff environment favored high progesterone and androgen secretion, decreasing alginate stiffness resulted in estrogen production which exceeded progesterone and androgen accumulation. These studies reveal, for the first time, a direct link between the biomechanical environment and follicle function, and suggest a novel non-hormonal mechanism regulating follicle development.

Tissue-engineered follicles produce live, fertile offspring

Oocytes grown in vitro are of low quality and yield few live births, thus limiting the ability to store or bank the ova of women wishing to preserve their fertility. We applied tissue engineering principles to the culture of immature mouse follicles by designing an alginate hydrogel matrix to maintain the oocyte's 3- dimensional (3D) architecture and cell-cell interactions in vitro. A 3D culture mimics the in vivo follicle environment, and hydrogel-encapsulated follicles develop mature oocytes within the capacity for fertilization similar to that of oocytes matured in vivo. Embryos derived from cultured oocytes fertilized in vitro and transferred to pseudopregnant female mice were viable, and both male and female offspring were fertile. Our results demonstrate that alginate hydrogel-based 3D in vitro culture of follicles permits normal growth and development of follicles and oocytes. This system creates new opportunities for discovery in follicle biology and establishes a core technology for human egg banks for preservation of fertility.

The structures that underlie normal reproductive function

The mechanisms and physiology of reproductive function have fascinated scientists throughout time. Recent cellular and molecular level structural studies have provided unprecedented insights into reproductive systems and signaling networks. This 'cutting edge' editorial provides a recent example in each of these areas, namely, the anatomical integrity of the follicle, the molecular structure of activin with its binding partners and the molecular regulation of inhibin. These three examples of structure informing function help explain reproductive health and may provide solutions to reproductive disease.

Identification of a stage-specific permissive in vitro culture environment for follicle growth and oocyte development

The availability of viable oocytes is the limiting factor in the development of new reproductive techniques. Many attempts have been made to grow immature oocytes in vitro during recent decades. Recently, a modified alginate-based three-dimensional culture system was designed to support the growth and maturation of multilayered secondary follicles. This system was able to produce oocytes that successfully completed meiosis, fertilization, and development to the blastocyst stage. Subsequent attempts to culture two-layered secondary follicles were unsuccessful under the original conditions. Herein, we investigated the effect of alginate consistency on two-layered follicle growth and oocyte developmental competence by encapsulating follicles into alginate scaffolds of various concentrations. Although there were no significant differences in survival rates, 0.25% and 0.5% alginate supported more rapid growth of follicles and antrum formation compared with 1.5% and 1.0% alginate after 8 days of culture. Alginate scaffold concentration also affected the proliferation and differentiation of somatic cells (theca and granulosa cells), measured in terms of morphological changes, steroid profiles (androstenedione, estradiol, and progesterone), and specific molecular markers (Fshr, Lhcgr, and Gja1). Theca cell proliferation and steroid production were hindered in follicles cultured in 1.5% alginate. In vitro fertilization and embryo culture revealed that oocytes obtained from 0.25% alginate retained the highest developmental competence. Overall, the present study showed that the alginate scaffold consistency affects folliculogenesis and oocyte development in vitro and that the alginate culture system can and should be tailored to maximally support follicle growth depending on the size and stage of the follicles selected for culture.

In vitro maturation of human oocytes in a follicle-mimicking three-dimensional coculture

OBJECTIVE

To verify the hypothesis that a three-dimensional, follicle-mimicking structure enhances in vitro maturation yields without hormonal supplementation in an in vitro maturation program.

DESIGN

Feasibility study; 204 anonymous denuded germinal vesicles retrieved from gonadotropin-treated women were cultured for 48 hours without hormonal supplementation in microdrop culture or in a three-dimensional coculture with granulosa cells in a barium alginate membrane.

SETTING

An assisted reproduction center in Italy.

PATIENT(S)

One hundred twenty-two informed women.

INTERVENTION(S)

Germinal vesicles retrieved after ovarian stimulation were denuded and cultured without hormonal supplementation in microdrop culture or in a three-dimensional coculture with granulosa cells enclosed in the core of a barium alginate capsule.

MAIN OUTCOME MEASURE(S)

Oocyte maturation and morphological investigation of follicle-mimicking structures.

RESULT(S)

Statistically significantly higher oocyte maturation yields were obtained by using the three-dimensional coculture system enclosed in a barium alginate membrane (after 48 hours: coculture, 90.3%; microdrop, 52.0%; odds ratio, 8.51). Morphological investigation indicated that after 48 hours of coculture, the decumulated oocyte appeared to be surrounded by a pseudocumulus structure that lies on the inner surface of the alginate membrane and protrudes toward the capsule's lumen.

CONCLUSION(S)

The maturation yield of cocultured oocytes is eightfold higher than that achieved with a microdrop maturation technique, making a higher number of gametes available for IVF programs. Stereomicroscopic morphological survey indicates a reassembly of granulosa cells surrounding oocyte zona, mimicking an antral cumulus oophorus.

FSH regulates acetycholine production by ovarian granulosa cells

BACKGROUND

It has been previously shown that cultured granulosa cells (GCs) derived from human ovarian preovulatory follicles contain choline acetyltransferase (ChAT), the enzyme responsible for acetylcholine (ACh) synthesis. They also produce ACh and express functional muscarinic ACh receptors. ACh can act on GCs to increase proliferation, disrupt gap junctional communication, alter intracellular calcium levels, as well as expression of transcription factors, suggesting an unrecognized role of ACh in GC function. To gain further insights into the possible role of ACh in the ovary, we examined ChAT expression in the gland before and after birth, as well as in adults, and studied the regulation of ACh production by FSH.

METHODS

ChAT immunohistochemistry was performed using ovarian samples of different species and ages (embryonic, postnatal and adult rats and mice, including embryonic ovaries from mice null for ChAT, neonatal and adult rhesus monkeys and adult humans). ACh was measured by HPLC and/or a fluorescence based method in rat ovaries and in a FSH receptor-expressing cell line (rat GFSHR-17) cultured with or without FSH.

RESULTS

In adult rat, as well as in all other species, ovarian ChAT immunoreactivity is associated with GCs of antral follicles, but not with other structures, indicating that GCs are the only ovarian source of ACh. Indeed ACh was clearly detected in adult rat ovaries by two methods. ChAT immunoreactivity is absent from embryonic and/or neonatal ovaries (mouse/rat and monkey) and ovarian development in embryonic mice null for ChAT appears normal, suggesting that ACh is not involved in ovarian or follicular formation. Since ChAT immunoreactivity is present in GCs of large follicles and since the degree of the ChAT immunoreactivity increases as antral follicles grow, we tested whether ACh production is stimulated by FSH. Rat GFSHR-17 cells that stably express the FSH receptor, respond to FSH with an increase in ACh production.

CONCLUSION

ACh and ChAT are present in GCs of growing follicles and FSH, the major driving force of follicular growth, stimulates ACh production. Since ACh stimulates proliferation and differentiation processes in cultured GCs, we suggest that ACh may act in the growing ovarian follicle as a local mediator of some of the actions ascribed to FSH.

Distribution of extracellular matrix proteins type I collagen, type IV collagen, fibronectin, and laminin in mouse folliculogenesis

The extracellular matrix (ECM) plays a prominent role in ovarian function by participating in processes such as cell migration, proliferation, growth, and development. Although some of these signaling processes have been characterized in the mouse, the relative quantity and distribution of ECM proteins within developing follicles of the ovary have not been characterized. This study uses immunohistochemistry and real-time PCR to characterize the ECM components type I collagen, type IV collagen, fibronectin, and laminin in the mouse ovary according to follicle stage and cellular compartment. Collagen I was present throughout the ovary, with higher concentrations in the ovarian surface epithelium and follicular compartments. Collagen IV was abundant in the theca cell compartment with low-level expression in the stroma and granulosa cells. The distribution of collagen was consistent throughout follicle maturation. Fibronectin staining in the stroma and theca cell compartment increased throughout follicle development, while staining in the granulosa cell compartment decreased. Heavy staining was also observed in the follicular fluid of antral follicles. Laminin was localized primarily to the theca cell compartment, with a defined ring at the exterior of the follicular granulosa cells marking the basement membrane. Low levels of laminin were also apparent in the stroma and granulosa cell compartment. Taken together, the ECM content of the mouse ovary changes during follicular development and reveals a distinct spatial and temporal pattern. This understanding of ECM composition and distribution can be used in the basic studies of ECM function during follicle development, and could aid in the development of in vitro systems for follicle growth.