Distribution and epidermal growth factor receptor expression of primordial follicles in human ovarian tissue before and after cryopreservation

Follicular growth and estradiol follow-up after subcutaneous xenografting of fresh and cryopreserved human ovarian tissue

OBJECTIVE

To assess ovarian cortex surrounding benign ovarian cysts after cryopreservation and grafting to severe combined immunodeficient (SCID) mice.

DESIGN

Animal study.

SETTING

Academic research laboratories.

PATIENT(S)

Ovarian tissue obtained from 15 patients.

INTERVENTION(S)

Grafting of fresh and frozen/thawed ovarian tissue into the subcutaneous space of 22 SCID mice for 80 days.

MAIN OUTCOME MEASURE(S)

Histologic analysis before and after grafting. Serum E(2) measured before (after 37 days of grafting) and after FSH/LH supplementation (end of the study).

RESULT(S)

After grafting, follicular density had decreased for frozen/thawed tissue in all cases. The follicular distribution was modified in fresh tissue: Primordial follicles proportion was reduced (79% vs. 17%), whereas the primary and secondary ones were increased (21% vs. 57% and 0% vs. 23%, respectively). The same tendency was observed in frozen/thawed tissue. Significant E(2) secretion was obtained before and after FSH/LH supplementation in castrated mice, grafted with either fresh or frozen/thawed tissue.

CONCLUSION(S)

Fresh and cryopreserved ovarian cortex surrounding benign ovarian cysts grafted into the subcutaneous space of SCID mice is able to sustain ovarian tissue function, although follicular growth appears lower with frozen/thawed tissue.

Clinical implications of the ErbB/epidermal growth factor (EGF) receptor family and its ligands in ovarian cancer

The ERBB or EGF receptor (EGFR) proto-oncogene family, which consists of four structurally-related transmembrane receptors (i.e., EGFR, ErbB2, ErbB3, and ErbB4), plays an etiological role in the molecular pathogenesis of cancer and is a key therapeutic target in many types of cancer, including ovarian cancer. These ErbB/EGF receptor tyrosine kinases play important physiologic roles in cell proliferation, survival, adhesion, motility, invasion, and angiogenesis. It is, therefore, not surprising that gene amplification, genetic mutation, and altered transcription/translation result in aberrant ErbB/EGF receptor expression and/or signal transduction, contributing to the development of malignant transformation. Clinically, the diagnostic, prognostic, and theragnostic significance of any single ErbB receptor and/or ErbB ligand is controversial, but generally, ErbB receptor overexpression has been correlated with poor prognosis and decreased therapeutic responsiveness in ovarian cancer patients. Thus, anticancer agents targeting ErbB/EGF receptors hold great promise for personalized cancer treatment. Yet, challenges remain in designing prospective clinical trials to assess the clinical utility of ErbB receptors and their ligands to diagnose cancer; to predict progression-free and overall survival, therapeutic responsiveness, and disease recurrence; and to monitor treatment responsiveness. Here, we review the tissue expression and serum biomarker studies that have evaluated the diagnostic, prognostic, and theragnostic utility of ErbB/EGF receptors, their circulating soluble isoforms (sEGFR/sErbBs), and their cognate ligands in ovarian cancer patients.

Establishment of ovarian reserve: a quantitative morphometric study of the developing human ovary

OBJECTIVE

To assess directly the dynamics of the formation of the ovarian reserve in the normal human ovary by evaluating the total number of follicles in developing ovaries when folliculogenesis occurs.

DESIGN

Histomorphometry-based follicle counts in complete serial tissue sections.

SETTING

Functional Anatomy Research Center, University of Milano.

PATIENT(S)

Thirteen fetuses, neonates, and one 8-month-old infant.

INTERVENTION(S)

Fifteen ovaries were completely cut, obtaining serial sections. Ovarian volume, volume fractions, density and total number of follicles per ovary were calculated using quantitative morphometric methods.

MAIN OUTCOME MEASURE(S)

Age-related dynamics of the establishment of ovarian reserve in human developing ovary at the end of the organogenesis.

RESULT(S)

The ovarian reserve (100,000 follicles at 15 weeks of postconceptional age) increased progressively to 680,000 follicles at 34 weeks. At 8 months of postnatal age the pool was still about 680,000 primordial follicles.

CONCLUSION(S)

The consistence of the primordial follicle pool during organogenesis shows an exponential increase until month 8 of prenatal life and it is subsequently maintained without modifications at least until month 8 of postnatal life.

A systematic review of tests predicting ovarian reserve and IVF outcome

The age-related decline of the success in IVF is largely attributable to a progressive decline of ovarian oocyte quality and quantity. Over the past two decades, a number of so-called ovarian reserve tests (ORTs) have been designed to determine oocyte reserve and quality and have been evaluated for their ability to predict the outcome of IVF in terms of oocyte yield and occurrence of pregnancy. Many of these tests have become part of the routine diagnostic procedure for infertility patients who undergo assisted reproductive techniques. The unifying goals are traditionally to find out how a patient will respond to stimulation and what are their chances of pregnancy. Evidence-based medicine has progressively developed as the standard approach for many diagnostic procedures and treatment options in the field of reproductive medicine. We here provide the first comprehensive systematic literature review, including an a priori protocolized information retrieval on all currently available and applied tests, namely early-follicular-phase blood values of FSH, estradiol, inhibin B and anti-Müllerian hormone (AMH), the antral follicle count (AFC), the ovarian volume (OVVOL) and the ovarian blood flow, and furthermore the Clomiphene Citrate Challenge Test (CCCT), the exogenous FSH ORT (EFORT) and the gonadotrophin agonist stimulation test (GAST), all as measures to predict ovarian response and chance of pregnancy. We provide, where possible, an integrated receiver operating characteristic (ROC) analysis and curve of all individual evaluated published papers of each test, as well as a formal judgement upon the clinical value. Our analysis shows that the ORTs known to date have only modest-to-poor predictive properties and are therefore far from suitable for relevant clinical use. Accuracy of testing for the occurrence of poor ovarian response to hyperstimulation appears to be modest. Whether the a priori identification of actual poor responders in the first IVF cycle has any prognostic value for their chances of conception in the course of a series of IVF cycles remains to be established. The accuracy of predicting the occurrence of pregnancy is very limited. If a high threshold is used, to prevent couples from wrongly being refused IVF, a very small minority of IVF-indicated cases (approximately 3%) are identified as having unfavourable prospects in an IVF treatment cycle. Although mostly inexpensive and not very demanding, the use of any ORT for outcome prediction cannot be supported. As poor ovarian response will provide some information on OR status, especially if the stimulation is maximal, entering the first cycle of IVF without any prior testing seems to be the preferable strategy.

Ovarian tissue cryopreservation and transplantation: a review

The review covers current options for ovarian tissue cryopreservation and transplantation and provides a systematic review of the existing literature from the last 10 years, taking into account all previously published reviews on the subject. The different cryopreservation options available for fertility preservation in cancer patients are embryo cryopreservation, oocyte cryopreservation and ovarian tissue cryopreservation. The choice depends on various parameters: the type and timing of chemotherapy, the type of cancer, the patient's age and the partner status. The different options and their results are discussed, as well as their putative indications and efficacy. The review concludes that advances in reproductive technology have made fertility preservation techniques a real possibility for patients whose gonadal function is threatened by premature menopause, or by treatments such as radiotherapy, chemotherapy or surgical castration.

Expression of mRNA and protein localization of epidermal growth factor and its receptor in goat ovaries

To examine the possibility that epidermal growth factor (EGF) and its receptor (EGF-R) are expressed throughout folliculogenesis, we studied the presence and distribution of EGF and EGF-R in goat ovaries. Ovaries of goats were collected and either fixed in paraformaldehyde for immunohistochemical localization of proteins, or used for the isolation of follicles, luteal cells and ovarian surface epithelium to study mRNA expression for EGF and EGF-R, using the reverse transcriptase polymerase chain reaction. EGF protein and mRNA were found in primordial, primary and secondary follicles as well as in small and large antral follicles and in surface epithelium, but in corpora lutea only the protein could be detected. Antral follicles expressed EGF mRNA in oocyte, cumulus, mural granulosa and theca cells. For EGF-R, both protein and mRNA were present at all stages of follicular development and in all antral follicular compartments. EGF-R protein and mRNA were also found in corpora lutea and surface epithelium. It is concluded that EGF and its receptor are expressed in goat ovarian follicles at all stages of follicle development, in corpora lutea, and in ovarian surface epithelium.

Regulation of primordial follicle assembly and development

The assembly of the primordial follicles early in ovarian development and the subsequent development and transition of the primordial follicle to the primary follicle are critical processes in ovarian biology. These processes directly affect the number of oocytes available to a female throughout her reproductive life. Once the pool of primordial follicles is depleted a series of physiological changes known as menopause occur. The inappropriate coordination of these processes contributes to ovarian pathologies such as premature ovarian failure (POF) and infertility. Primordial follicle assembly and development are coordinated by locally produced paracrine and autocrine growth factors. Endocrine factors such as progesterone have also been identified that influence follicular assembly. Locally produced factors that promote the primordial to primary follicle transition include growth factors such as kit ligand (KL), leukaemia inhibitory factor (LIF), bone morphogenic proteins (BMP's), keratinocyte growth factor (KGF) and basic fibroblast growth factor (bFGF). Factors mediating both precursor theca-granulosa cell interactions and granulosa-oocyte interactions have been identified. A factor produced by preantral and antral follicles, Müllerian inhibitory substance, can act to inhibit the primordial to primary follicle transition. Observations suggest that a complex network of cell-cell interactions is required to control the primordial to primary follicle transition. Elucidation of the molecular and cellular control of primordial follicle assembly and the primordial to primary follicle transition provides therapeutic targets to regulate ovarian function and treat ovarian disease.

Human ovarian tissue from cortex surrounding benign cysts: a model to study ovarian tissue cryopreservation

BACKGROUND

The scarcity of human ovarian tissue is a major problem in developing research on ovarian cryopreservation. We were interested in ovarian cortex surrounding benign ovarian cysts harvested during their requisite operations.

METHODS

Ovarian tissue was collected from 25 women (mean age = 27.7 +/- 1.0 SEM) and frozen in serum-free cryoprotective medium. Histological and viability analysis were performed on fresh and frozen-thawed slices of tissue.

RESULTS

Dermoid (n = 7), endometriosis (n = 13) and serous (n = 5) cysts were observed. Follicular densities (expressed per mm3) in ovarian cortex surrounding dermoid cysts were higher than in endometriosis and serous cysts for both histological (median of follicular densities: 13.04, 0.31 and 0.89 respectively) and viability analysis (2.93, 0.05 and 0.71 respectively). Freezing-thawing did not result in gross abnormality of follicle population either in number or morphology (80% of follicles preserved a normal pattern). However, a slight decrease of the density of living follicles (expressed per mm2) was reported.

CONCLUSIONS

Ovarian cortex surrounding ovarian cysts, especially dermoid cysts, could be considered a source of ovarian tissue for future research. In our study, the cryopreservation procedure resulted in high follicular survival assessed by both histological and viability analysis. Nevertheless, further studies of in vivo and in vitro follicular maturation are needed to strengthen this model.

Ficoll density gradient method for recovery of isolated human ovarian primordial follicles

OBJECTIVE

To develop a simple and efficient technique to allow rapid recovery of a maximum number of good quality isolated follicles.

DESIGN

Prospective experimental study.

SETTING

Academic research unit of the department of gynecology in a university hospital.

PATIENT(S)

Biopsies were obtained from five women (between 26 and 31 years of age).

INTERVENTION(S)

Biopsies were cut with a tissue sectioner. Enzymatic digestion was performed in a collagenase solution for 90 min at 37 degrees C. The follicles were recovered using a discontinuous Ficoll density gradient method.

MAIN OUTCOME MEASURE(S)

The number of follicles present in the interface layers of Ficoll gradient was quantified. Follicular viability of these recovered follicles was assessed with live-dead stains, using calcein-AM and ethidium homodimer-I.

RESULT(S)

Out of a total of 6,811 recovered follicles, we found 63% (n = 4,201) at the medium-1.06 Ficoll interface and 36.9% (n = 2,590) at the 1.06-1.09 Ficoll interface, which represents 99.9% of total recovered follicles. Analysis by vital fluorescent staining showed that 95.8% of the follicles treated with Ficoll were totally viable.

CONCLUSION(S)

The Ficoll density gradient method allows us to maximize the recovery of isolated human ovarian follicles and minimize the manipulation time while maintaining high follicular viability.

Diagnostic assessment of the developmental potential of human cryopreserved ovarian tissue from multiple patients using xenografting

BACKGROUND

Although ovarian tissue cryopreservation for women at risk of losing ovarian function is offered by many clinics, there is a lack of evidence relating to the developmental potential of the stored tissue and, therefore, its clinical potential. This study was designed to use xenografting of cryopreserved tissue from multiple patients to assess the reproducibility of preservating developmental potential, the variation in developing follicle profile and the relationship between pre-freeze histology and post-thaw development.

METHODS

Using previously published methods, cryopreserved ovarian cortex from nine patients was thawed and grafted under the kidney capsules of immunodeficient mice. Development of follicles was assessed after 26 weeks and compared to histology prior to freezing.

RESULTS

Multiple growing follicles including antral stages were observed in multiple grafts of tissue from all patients. Metaphase II oocytes (n=9) were observed in follicles in grafts from five patients. There was no relationship between pre-freeze histology and developing follicle profile in xenografts.

CONCLUSIONS

The propanediol freezing method used in this study is capable of reproducibly preserving the developmental potential of human ovarian follicles. The developing follicle profile after cryopreservation cannot be accurately predicted from pre-freeze histology. Xenografting provides a powerful tool for assessing the potential of human cryopreserved ovarian tissue.

Influences of FSH and EGF on primordial follicles during in vitro culture of caprine ovarian cortical tissue

Factors that control the onset of folliculogenesis are critical to female gamete production, but poorly understood. The aim of the present study was to investigate the effects of FSH and EGF on the activation and growth of goat primordial follicles in vitro. To this end, pieces of goat ovarian cortex were cultured in vitro for 1, 3 or 5 days, at 39 degrees C in an atmosphere containing 5% CO(2), in minimum essential medium supplemented with insulin, transferrin, selenium, pyruvate, glutamine, hypoxanthine, BSA, penicillin, streptomycin and fungizone and with or without FSH (100 ng/ml) and/or EGF (100 ng/ml). At the end of the culture periods, the relative proportions of primordial, intermediate, primary and secondary follicles were calculated and compared with those in non-cultured tissue. In addition, mitotic activity of granulosa cells was studied by immunohistochemistry for proliferating cell nuclear antigen (PCNA). In brief, it was found that goat primordial follicles activate spontaneously during culture in vitro and, while neither FSH nor EGF affected the proportion of primordial follicles that entered the growth phase, both stimulated an increase in oocyte and follicle diameter, especially in intermediate and primary follicles cultured for 5 days. On the other hand, there was no significant effect of culture or either growth factor on the proportion of PCNA-stained growing follicles. Contrary to expectations, neither FSH nor EGF affected follicle viability or integrity during culture, since the percentages of intact follicles did not differ between control, FSH and/or EGF containing medium. In conclusion, this study demonstrated that goat primordial follicles activate spontaneously in vitro, and that both FSH and EGF stimulate an increase in follicle size by promoting oocyte growth.

Age-related decline in fertility

A progressive decline in fecundity with advancing age is a reality, attributed primarily to the detrimental impact of various aging processes on female gametes. Despite medical advances that have dramatically prolonged the female life span, declining numbers and deteriorating quality of oocytes, and an increasing incidence of meiotic errors and aneuploidy of gametes and embryos, reduce clinical pregnancy rates and escalate pregnancy wastage. Increased fetal aneuploidies in ongoing pregnancies and an increased predisposition to obstetric morbidities further contribute to the diminishing reproductive successes associated with advancing age. The age of male partners, despite the decline in semen parameters and sexual performance with aging, does not appear to have a major impact on the eventual fertility of the aging couple. The contributions of age-related impaired sexuality and ejaculatory problems, although slight albeit significant, to declining fertility in the aging should be appreciated in appropriate cases. With the realization of the age-related detriment on fertility potential and the limitations of available therapeutic interventions, management of subfecundity in women beyond their mid-30s should be approached aggressively. Success of ovulation induction with clomiphine citrate or gonadotropins is marginal in women aged older than 40 years; a case can be made to proceed directly with ART in women in this age group, especially when there is coexisting male factor or pelvic disease. Except for the use of donor oocytes, the outcome of various therapeutic interventions to optimize reproductive performance in women aged older than 44 years remains dismal. A broader application of PGD techniques may contribute to improved live birth rates in reproductively aging women. The greater likelihood of obstetric complications in pregnancies resulting from donor oocytes and an increased prevalence of age-related medical problems complicating pregnancy should prompt a thorough medical evaluation before proceeding with ART.

The potential of ovarian tissue transplant to preserve fertility

Laboratory research on ovarian cryopreservation and transplantation began in the 1950s leading to clinical studies in the 2000s. The research that was performed during this half a century indicated that cryopreserved ovarian tissue has the potential to restore fertility in women who face premature ovarian failure due to chemotherapy, radiotherapy or surgery. Until today, ovarian function has been restored in at least four women. Even though no pregnancies have been reported to date from these clinical studies, animal studies indicate that this is a valid prospect for humans. Future clinical trials will determine in a larger number of patients the longevity of ovarian grafts, normalcy of hormone production and ovarian follicle development, possibility and safety of pregnancy and the safety of auto-transplantation in cancer patients. In addition, further basic research may be needed to develop better cryoprotectants and cryopreservation techniques. However, the major improvement in the efficiency of ovarian transplantation is anticipated to come from research exploring the revascularisation process.

Epidermal growth factor modulates transforming growth factor receptor messenger RNA and protein levels in hamster preantral follicles in vitro

Epidermal growth factor (EGF) is mitogenic to preantral follicles, and transforming growth factor beta (TGFbeta) influences ovarian cell functions in a variety of species. Although an interaction of these ligands during preantral folliculogenesis is likely, whether EGF influences TGFbeta action on preantral follicles by modulating TGFbeta receptor (TbetaR) gene transcription and translation is not known. To determine whether EGF influenced TbetaR mRNA and protein levels in granulosa cells during preantral folliculogenesis, hamster preantral follicles at stages 1-6 were cultured in the absence or presence of EGF and follicular TbetaR mRNA, and protein levels were monitored by semiquantitative reverse transcription polymerase chain reaction and immunoblotting, respectively. Both TbetaR type I (TbetaRI) and TbetaR type II (TbetaRII) mRNA and protein were present in preantral follicles, and their expression was up-regulated by EGF in a stage-dependent manner. However, EGF effect on the expression of TbetaRI and TbetaRII was differential. In contrast to TbetaRI, EGF-stimulation of follicular TbetaRII mRNA expression was evident from stages 1 and 2 onwards, and more than twofold induction was noted for stages 4-6. Moreover, significant increases in thecal TbetaR mRNA levels were noted for stage 6 follicles. Follicles at smaller stages appeared to be more sensitive to EGF than were larger preantral follicles. Despite an increase in the cytosolic form of TbetaRI protein for most of the stages and TbetaRII protein for follicles at stages 4 and 5, EGF-stimulation of the membrane-associated form of the receptor was restricted to follicles at stage 6. Functionally, TGFbeta1 attenuated EGF-induced DNA synthesis for follicles at stages 1-3 and 6 without affecting EGF-induced progesterone production for most of the stages. Administration of alpha-amanitin resulted in a significant reduction of EGF-induction of TbetaR mRNA levels, suggesting that increased receptor protein levels were a consequence of mRNA synthesis. These results indicate that an interaction between EGF and TGFbeta forms an important regulatory mechanism for preantral folliculogenesis. The effect of EGF on TbetaRI and TbetaRII gene transcription and translation are differential, and follicular response to EGF depends on the developmental status of the follicles.

Recent progress in oocyte and ovarian tissue cryopreservation and transplantation

Ovarian tissue cryopreservation and transplantation is an experimental technique that has been developed to sustain the reproductive function of women and children who are faced with sterilizing chemotherapy, radiotherapy, or radical reproductive surgery. Oocyte cryopreservation, on the other hand, is less feasible in the context of cancer because there is usually inadequate time to complete an ovarian stimulation cycle. The main promise of oocyte cryopreservation is that it offers an alternative when embryo freezing is not possible for technical, regulatory, or religious reasons. Oocyte freezing is more suitable for a single woman when the concern is age-related decline in fecundity. There have been significant scientific advances in the field of cryopreservation of ovarian tissue and oocytes, especially within the past few years. Ovarian function has been reported after the first cases of ovarian transplantation, and the number of pregnancies from cryopreserved oocytes has grown. Ovarian tissue and oocyte freezing can now be recommended in a carefully selected group of patients, provided that these options are offered under protocols that are approved by an institutional review board.

Activation of follicle development: the primordial follicle

Investigations of primordial follicle formation and growth are fundamental to our understanding of female gamete production. In all mammalian females the full complement of oocytes is established during fetal development. This store of primordial follicles is not renewable and serves the entire reproductive life span of the adult. The correct programming of fetal ovarian development and the number of primordial follicles formed will therefore limit the fecundity of the ovary. Primordial follicles are characterized by the presence of a single oocyte surrounded by a varying number of pregranulosa cells. The relatively small size, undifferentiated status and large numbers of primordial follicles make them prime candidates for use in basic and applied research in animal production, gene transfer and cloning. Furthermore, the development of cell culture systems that use primordial follicles as a source of oocytes for in vitro growth and maturation will enable us to maximize the potential of high genetic merit females and to shorten generation intervals. Despite these possibilities, primordial follicles are the least understood of all stages of follicle development. The factor(s) responsible for maintaining the primordial pool or, conversely, for activating primordial follicle growth remain elusive.

Fluorescent probes allow rapid and precise recording of follicle density and staging in human ovarian cortical biopsy samples

OBJECTIVE

To develop rapid and reliable techniques for determining follicle content, viability, and morphologic features in an ovarian cortical biopsy specimen.

DESIGN

Prospective laboratory study.

SETTING

Academic research institution.

PATIENT(S)

Consenting patients undergoing laparoscopic surgery for nonovarian disease.

INTERVENTION(S)

Ovarian cortical biopsy specimens were stained by using fluorescent probes and conventional histologic stains. Observations were made by using light, fluorescent, and confocal laser microscopy.

MAIN OUTCOME MEASURE(S)

Density, cellular viability, and morphologic features of ovarian follicles.

RESULT(S)

After 45 minutes of incubation of ovarian cortical tissue with calcein AM, follicles were visualized by fluorescent microscopy and counted. Ten minutes of exposure is sufficient to stain all cell nuclei with the PicoGreen probe. Subsequent confocal microscopy allows quantification of follicle density and reveals follicle morphology in the optical sections. Follicle density as assessed by using these rapid methods was concordant with the number of units counted in conventionally stained histologic sections.

CONCLUSION(S)

Use of fluoroprobes for mitochondrial and DNA staining allows rapid evaluation of follicle density in ovarian tissue.

Histologic and ultrastructural evaluation of fresh and frozen-thawed human ovarian xenografts in nude mice

OBJECTIVE

To compare histologic and ultrastructural characteristics of fresh and frozen-thawed human ovarian cortical tissue grafted into nude mice.

DESIGN

Experimental prospective study.

SETTING

An academic research environment.

PATIENT(S)

Ovarian biopsy specimens were obtained from 13 women undergoing laparoscopy for tubal ligation or infertility.

ANIMAL(S)

Forty nude mice.

INTERVENTION(S)

A minilaparotomy was performed to place fresh and frozen-thawed ovarian grafts subcutaneously (sc) or intraperitoneally (ip). Removal of the ovarian grafts was performed at 24 days.

MAIN OUTCOME MEASURE(S)

[1] the follicular population, [2] fibrosis, [3] vascularization of the grafted tissue, and [4] ultrastructural evaluation.

RESULT(S)

A greater fibrosis relative surface area was noted in frozen-thawed transplanted tissue than in fresh transplants. Regardless of this fibrosis, a similar follicular density was observed in fresh and frozen-thawed ovarian tissue 24 days after transplantation. Active angiogenesis was proved by both immunohistochemical study of the vascular endothelial growth factor and morphometric study of the vascular network. Normal ultrastructural characteristics were noted in frozen-thawed ovarian biopsies.

CONCLUSION(S)

Angiogenesis allows implantation of the graft even if it has been cryopreserved and thawed similarly to implantation of fresh tissue. The greater fibrosis observed in grafts after cryopreservation and implantation does not seem to affect the primordial and primary ovocyte population and their ultrastructural characteristics, but further studies must be conducted to prove that after cryopreservation and transplantation, ovocytes may achieve full maturation and fertilization.