Ovarian microenvironment: challenges and opportunities in protecting against chemotherapy-associated ovarian damage

BACKGROUND

Chemotherapy-associated ovarian damage (CAOD) is one of the most feared short- and long-term side effects of anticancer treatment in premenopausal women. Accumulating detailed data show that different chemotherapy regimens can lead to disturbance of ovarian hormone levels, reduced or lost fertility, and an increased risk of early menopause. Previous studies have often focused on the direct effects of chemotherapeutic drugs on ovarian follicles, such as direct DNA damage-mediated apoptotic death and primordial follicle burnout. Emerging evidence has revealed an imbalance in the ovarian microenvironment during chemotherapy. The ovarian microenvironment provides nutritional support and transportation of signals that stimulate the growth and development of follicles, ovulation, and corpus luteum formation. The close interaction between the ovarian microenvironment and follicles can determine ovarian function. Therefore, designing novel and precise strategies to manipulate the ovarian microenvironment may be a new strategy to protect ovarian function during chemotherapy.

OBJECTIVE AND RATIONALE

This review details the changes that occur in the ovarian microenvironment during chemotherapy and emphasizes the importance of developing new therapeutics that protect ovarian function by targeting the ovarian microenvironment during chemotherapy.

SEARCH METHODS

A comprehensive review of the literature was performed by searching PubMed up to April 2024. Search terms included 'ovarian microenvironment' (ovarian extracellular matrix, ovarian stromal cells, ovarian interstitial, ovarian blood vessels, ovarian lymphatic vessels, ovarian macrophages, ovarian lymphocytes, ovarian immune cytokines, ovarian oxidative stress, ovarian reactive oxygen species, ovarian senescence cells, ovarian senescence-associated secretory phenotypes, ovarian oogonial stem cells, ovarian stem cells), terms related to ovarian function (reproductive health, fertility, infertility, fecundity, ovarian reserve, ovarian function, menopause, decreased ovarian reserve, premature ovarian insufficiency/failure), and terms related to chemotherapy (cyclophosphamide, lfosfamide, chlormethine, chlorambucil, busulfan, melphalan, procarbazine, cisplatin, doxorubicin, carboplatin, taxane, paclitaxel, docetaxel, 5-fluorouraci, vincristine, methotrexate, dactinomycin, bleomycin, mercaptopurine).

OUTCOMES

The ovarian microenvironment shows great changes during chemotherapy, inducing extracellular matrix deposition and stromal fibrosis, angiogenesis disorders, immune microenvironment disturbance, oxidative stress imbalances, ovarian stem cell exhaustion, and cell senescence, thereby lowering the quantity and quality of ovarian follicles. Several methods targeting the ovarian microenvironment have been adopted to prevent and treat CAOD, such as stem cell therapy and the use of free radical scavengers, senolytherapies, immunomodulators, and proangiogenic factors.

WIDER IMPLICATIONS

Ovarian function is determined by its 'seeds' (follicles) and 'soil' (ovarian microenvironment). The ovarian microenvironment has been reported to play a vital role in CAOD and targeting the ovarian microenvironment may present potential therapeutic approaches for CAOD. However, the relation between the ovarian microenvironment, its regulatory networks, and CAOD needs to be further studied. A better understanding of these issues could be helpful in explaining the pathogenesis of CAOD and creating innovative strategies for counteracting the effects exerted on ovarian function. Our aim is that this narrative review of CAOD will stimulate more research in this important field.

REGISTRATION NUMBER

Not applicable.

Prospective solutions to ovarian reserve damage during the ovarian tissue cryopreservation and transplantation procedure

Birth rates continue to decline as more women experience fertility issues. Assisted reproductive technologies are available for patients seeking fertility treatment, including cryopreservation techniques. Cryopreservation can be performed on gametes, embryos, or gonadal tissue and can be used for patients who desire to delay in vitro fertilization treatment. This review focuses on ovarian tissue cryopreservation, the freezing of ovarian cortex containing immature follicles. Ovarian tissue cryopreservation is the only available treatment for the restoration of ovarian function in patients who undergo gonadotoxic treatments, and its wide adoption has led to its recent designation as "no longer experimental" by the American Society for Reproductive Medicine. Ovarian tissue cryopreservation and subsequent transplantation can restore native endocrine function and can support the possibility of pregnancy and live birth for the patient. Importantly, there are multiple steps in the procedure that put the ovarian reserve at risk of damage. The graft is highly susceptible to ischemic reperfusion injury and mass primordial follicle growth activation, resulting in a "burnout" phenomenon. In this review, we summarize current efforts to combat the loss of primordial follicles in grafts through improvements in freeze and thaw protocols, transplantation techniques, and pharmacologic adjuvant treatments. We conducted a review of the literature, with emphasis on emergent research in the last 5 years. Regarding freeze and thaw protocols, we discuss the widely accepted slow freezing approach and newer vitrification protocols. Discussion of improved transplantation techniques includes consideration of the transplantation location of the ovarian tissue and the importance of graft sites in promoting neovascularization. Finally, we discuss pharmacologic treatments being studied to improve tissue performance postgraft. Of note, there is significant research into the efficacy of adjuvants used to reduce ischemic injury, improve neovascularization, and inhibit hyperactivation of primordial follicle growth activations. Although the "experimental" label has been removed from ovarian tissue cryopreservation and subsequent transplantation, there is a significant need for further research to better understand sources of ovarian reserve damage to improve outcomes. Future research directions are provided as we consider how to reach the most hopeful results for women globally.

Heterotopic ovarian allotransplantation in a caprine model: Effects of implant site on morphological parameters

This study aimed to investigate a new implantation site (intra-auricular subcutaneous - IA) compared to intramuscular (IM) in the cervical portion (cervical splenius muscle) of the neck for ovarian transplantation in goats. Morphological aspects of the implant, follicular activation and morphology, and type I and III collagen deposits of the transplanted tissue were evaluated. Four fragments of the ovarian cortex were allotransplanted at the IA and IM sites in all goat recipients and recovered 7 (IA-7; IM-7) or 15 (IA-15; IM-15) days later and submitted to histological analysis. Two fragments/animal were separated for the fresh control (FC) group. There was a higher percentage of normal and developing primordial follicles at the IA-7 site (P < 0.05) compared to the other treatments, with similar values to the fresh control. Type I and III collagen fibers differed between the groups (P < 0.05), showing a considerable decrease in type I collagen fibers at the IA-7 site compared to the FC. However, the IM-7 and IA-15 sites showed higher values of type I collagen fibers, showing similarity to the FC. Therefore, we conclude that the IA site in goats is an effective site for ovarian tissue transplantation, as it is easily accessible, low invasive and has presented satisfactory rates of morphology and follicular activation.

Research progress on mechanism of follicle injury after ovarian tissue transplantation and protective strategies

Ovarian tissue cryopreservation and transplantation is the only way to preserve fertility for female cancer patients in prepubertal ages and those who cannot delay radiotherapy or chemotherapy. However, the success rate of cryopreservation and transplantation of ovarian tissue is still low at present due to the risk of ischemia and hypoxia of the grafted tissues. Abnormal activation of primordial follicles and ischemia-reperfusion injury after blood supply recovery also cause massive loss of follicles in grafted ovarian tissues. Various studies have explored the use of different drugs to reduce the damage of follicles during freezing and transplantation as well as to extend the duration of endocrine and reproductive function in patients with ovarian transplantation. For example, melatonin, N-acetylcysteine, erythropoietin or other antioxidants have been used to reduce oxidative stress; mesenchymal stem cells derived from different tissues, basic fibroblast growth factor, vascular endothelial growth factor, angiopoietin 2 and gonadotropin have been used to promote revascularization; anti-Müllerian hormone and rapamycin have been used to reduce abnormal activation of primordial follicles. This article reviews the research progress on the main mechanisms of follicle loss after ovarian tissue transplantation, including hypoxia, ischemia-reperfusion injury and associated cell death, and abnormal activation of follicles. The methods for reducing follicle loss in grafted ovarian tissues are further explored to provide a reference for improving the efficiency of ovarian tissue cryopreservation and transplantation.

Innovative Strategies for Fertility Preservation in Female Cancer Survivors: New Hope from Artificial Ovary Construction and Stem Cell-Derived Neo-Folliculogenesis

Recent advances in anticancer treatment have significantly improved the survival rate of young females; unfortunately, in about one third of cancer survivors the risk of ovarian insufficiency and infertility is still quite relevant. As the possibility of becoming a mother after recovery from a juvenile cancer is an important part of the quality of life, several procedures to preserve fertility have been developed: ovarian surgical transposition, induction of ovarian quiescence by gonadotropin-releasing hormone agonists (GnRH-a) treatment, and oocyte and/or ovarian cortical tissue cryopreservation. Ovarian tissue cryostorage and allografting is a valuable technique that applies even to prepubertal girls; however, some patients cannot benefit from it due to the high risk of reintroducing cancer cells during allograft in cases of ovary-metastasizing neoplasias, such as leukemias or NH lymphomas. Innovative techniques are now under investigation, as in the construction of an artificial ovary made of isolated follicles inserted into an artificial matrix scaffold, and the use of stem cells, including ovarian stem cells (OSCs), to obtain neo-folliculogenesis and the development of fertilizable oocytes from the exhausted ovarian tissue. This review synthesizes and discusses these innovative techniques, which potentially represent interesting strategies in oncofertility programs and a new hope for young female cancer survivors.

Prospects for fertility preservation: the ovarian organ function reconstruction techniques for oogenesis, growth and maturation in vitro

Today, fertility preservation is receiving more attention than ever. Cryopreservation, which preserves ovarian tissue to preserve fertility in young women and reduce the risk of infertility, is currently the most widely practiced. Transplantation, however, is less feasible for women with blood-borne leukemia or cancers with a high risk of ovarian metastasis because of the risk of cancer recurrence. In addition to cryopreservation and re-implantation of embryos, in vitro ovarian organ reconstruction techniques have been considered as an alternative strategy for fertility preservation. In vitro culture of oocytes in vitro Culture, female germ cells induction from pluripotent stem cells (PSC) in vitro, artificial ovary construction, and ovaria-related organoids construction have provided new solutions for fertility preservation, which will therefore maximize the potential for all patients undergoing fertility preservation. In this review, we discussed and thought about the latest ovarian organ function reconstruction techniques in vitro to provide new ideas for future ovarian disease research and fertility preservation of patients with cancer and premature ovarian failure.

Novel Approaches Used in Ovarian Tissue Transplantation for Fertility Preservation: Focus on Tissue Engineering Approaches and Angiogenesis Capacity

Due to the impact of the modern lifestyle, female infertility has been reduced because of different reasons. For example, in combined chemotherapeutic therapies, a small fraction of cancer survivors has faced different post-complications and side effects such as infertility. Besides, in modern society, delayed age of childbearing has also affected fertility. Nowadays, ovarian tissue cryopreservation and transplantation (OTC/T) is considered one of the appropriate strategies for the restoration of ovarian tissue and bioactivity in patients with the loss of reproductive function. In this regard, several procedures have been considered to improve the efficacy and safety of OTT. Among them, a surgical approach is used to transplant ovaries into the optimal sites, but the existence of ischemic changes and lack of appropriate revascularization can lead to bulk follicular atresia. Besides, the role of OTC/T is limited in women of advanced maternal age undergoing lifesaving chemo-radiation. As a correlate, the development of de novo approaches with efficacious regenerative outcomes is highly welcomed. Tissue engineering shows high therapeutic potentialities to restore fertility in males and females using the combination of biomaterials, cells, and growth factors. Unfortunately, most synthetic and natural materials are at the experimental stage and only the efficacy has been properly evaluated in limited cases. Along with these descriptions, strategies associated with the induction of angiogenesis in transplanted ovaries can diminish the injuries associated with ischemic changes. In this review, the authors tried to summarize recent techniques, especially tissue engineering approaches for improving ovarian function and fertility by focusing on angiogenesis and neovascularization.

An Update on In Vitro Folliculogenesis: A New Technique for Post-Cancer Fertility

Introduction: Obtaining in vitro mature oocytes from ovarian tissue to preserve women’s fertility is still a challenge. At present, there is a therapeutic deadlock for girls and women who need emergency fertility preservation in case of a high risk of ovary invasion by malignant cells. In such a case, ovarian tissue cannot be engrafted; an alternative could be in vitro folliculogenesis. Methods: This review focuses on the progress of in vitro folliculogenesis in humans. PubMed and Embase databases were used to search for original English-language articles. Results: The first phase of in vitro folliculogenesis is carried out in the original ovarian tissue. The addition of one (or more) initiation activator(s) is not essential but allows better yields and the use of a 3D culture system at this stage provides no added value. The second stage requires a mechanical and/or enzymatic isolation of the secondary follicles. The use of an activator and/or a 3D culture system is then necessary. Conclusion: The current results are promising but there is still a long way to go. Obtaining live births in large animals is an essential step in validating this in vitro folliculogenesis technique.

Ovarian Tissue Cryopreservation in Children and Adolescents

Cancer during childhood and adolescence remains a major public health issue, affecting a significant portion of this age group. Although newer anti-cancer treatments have improved survival rates, this comes at a cost in terms of gonadotoxic effects. As a result, the preservation of fertility is important. Ovarian tissue cryopreservation, one of the newest methods, has some advantages, especially for prepubertal patients: no need for ovarian stimulation, thus, no further risk for estrogen-sensitive cancer types, and preservation of more and better-quality primordial follicles of the ovarian cortex. The most frequent indications include treatment with alkylating agents, ovarian-focused radiotherapy, leukemias, lymphomas, brain and neurological tumors, as well as Turner syndrome and benign hemoglobinopathies. An expected survival exceeding 5 years, the absence of systematic disease and an overall risk of premature ovarian insufficiency over 50% are among the criteria that need to be fulfilled in order for a patient to undertake this method. Orthotopic transplantation is more frequently used, since it can allow both live birth and the recovery of endocrine function. Reimplantation of malignant cells is always a major risk and should always be taken into consideration. Histological analysis, as well as immunohistochemical and molecular methods, are needed in order to improve the search for malignant cells before transplantation. Ovarian tissue cryopreservation appears to be a method with specific benefits, indications and risks which can be an important tool in terms of preserving fertility in younger women.

Biomaterials and advanced technologies for the evaluation and treatment of ovarian aging

Ovarian aging is characterized by a progressive decline in ovarian function. With the increase in life expectancy worldwide, ovarian aging has gradually become a key health problem among women. Over the years, various strategies have been developed to preserve fertility in women, while there are currently no clinical treatments to delay ovarian aging. Recently, advances in biomaterials and technologies, such as three-dimensional (3D) printing and microfluidics for the encapsulation of follicles and nanoparticles as delivery systems for drugs, have shown potential to be translational strategies for ovarian aging. This review introduces the research progress on the mechanisms underlying ovarian aging, and summarizes the current state of biomaterials in the evaluation and treatment of ovarian aging, including safety, potential applications, future directions and difficulties in translation.

Medical Grade Honey as a Promising Treatment to Improve Ovarian Tissue Transplantation

Ovarian tissue cryopreservation is a female fertility preservation technique that presents major challenges for the maintenance of follicular viability after transplantation. The aim of this study was to evaluate and compare the application of L-Mesitran Soft®, a product containing 40% medical grade honey (MGH), with other strategies to improve ovarian grafts' viability. For this purpose, bovine ovarian tissue was vitrified, warmed and randomly assigned to culture groups: (1) control, (2) MGH 0.2% in vitro, (3) MGH in vivo (direct application in the xenotransplantation), (4) vascular endothelial growth factor (VEGF 50 ng/mL) and (5) vitamin D (100 Nm), during a 48 h period. A sixth group (6) of fragments was thawed on transplantation day and was not cultured. The tissue was xenotransplanted into immunodeficient (Rowett nude homozygous) ovariectomized rats. Grafts were analyzed 48 h after culture, and 7 and 28 days after transplantation. The tissue was subjected to histological and immunohistochemical analysis. Treatments using MGH showed the highest angiogenic and cell proliferation stimulation, with cellular apoptosis, within a healthy cellular turnover pathway. In conclusion, MGH should be considered as a potentially effective and less expensive strategy to improve ovarian tissue transplantation.

Applications of Hydrogels in Premature Ovarian Failure and Intrauterine Adhesion

Premature ovarian failure (POF) and intrauterine adhesion (IUA) that easily lead to reduced fertility in premenopausal women are two difficult diseases to treat in obstetrics and gynecology. Hormone therapy, in vitro fertilization and surgical treatments do not completely restore fertility. The advent of hydrogels offers new hope for the treatment of POF and IUA. Hydrogels are noncytotoxic and biodegradable, and do not cause immune rejection or inflammatory reactions. Drug delivery and stem cell delivery are the main application forms. Hydrogels are a local drug delivery reservoir, and the control of drug release is achieved by changing the physicochemical properties. The porous properties and stable three-dimensional structure of hydrogels support stem cell growth and functions. In addition, hydrogels are promising biomaterials for increasing the success rate of ovarian tissue transplantation. Hydrogel-based in vitro three-dimensional culture of follicles drives the development of artificial ovaries. Hydrogels form a barrier at the site of injury and have antibacterial, antiadhesive and antistenosis properties for IUA treatment. In this review, we evaluate the physicochemical properties of hydrogels, and focus on the latest applications of hydrogels in POF and IUA. We also found the limitations on clinical application of hydrogel and provide future prospects. Artificial ovary as the future of hydrogel in POF is worth studying, and 3D bioprinting may help the mass production of hydrogels.

Artificial Ovary for Young Female Breast Cancer Patients

In recent decades, there has been increasing attention toward the quality of life of breast cancer (BC) survivors. Meeting the growing expectations of fertility preservation and the generation of biological offspring remains a great challenge for these patients. Conventional strategies for fertility preservation such as oocyte and embryo cryopreservation are not suitable for prepubertal cancer patients or in patients who need immediate cancer therapy. Ovarian tissue cryopreservation (OTC) before anticancer therapy and autotransplantation is an alternative option for these specific indications but has a risk of retransplantation malignant cells. An emerging strategy to resolve these issues is by constructing an artificial ovary combined with stem cells, which can support follicle proliferation and ensure sex hormone secretion. This promising technique can meet both demands of improving the quality of life and meanwhile fulfilling their expectation of biological offspring without the risk of cancer recurrence.

OUP accepted manuscript

BACKGROUND

To provide the optimal milieu for implantation and fetal development, the female reproductive system must orchestrate uterine dynamics with the appropriate hormones produced by the ovaries. Mature oocytes may be fertilized in the fallopian tubes, and the resulting zygote is transported toward the uterus, where it can implant and continue developing. The cervix acts as a physical barrier to protect the fetus throughout pregnancy, and the vagina acts as a birth canal (involving uterine and cervix mechanisms) and facilitates copulation. Fertility can be compromised by pathologies that affect any of these organs or processes, and therefore, being able to accurately model them or restore their function is of paramount importance in applied and translational research. However, innate differences in human and animal model reproductive tracts, and the static nature of 2D cell/tissue culture techniques, necessitate continued research and development of dynamic and more complex in vitro platforms, ex vivo approaches and in vivo therapies to study and support reproductive biology. To meet this need, bioengineering is propelling the research on female reproduction into a new dimension through a wide range of potential applications and preclinical models, and the burgeoning number and variety of studies makes for a rapidly changing state of the field.

OBJECTIVE AND RATIONALE

This review aims to summarize the mounting evidence on bioengineering strategies, platforms and therapies currently available and under development in the context of female reproductive medicine, in order to further understand female reproductive biology and provide new options for fertility restoration. Specifically, techniques used in, or for, the uterus (endometrium and myometrium), ovary, fallopian tubes, cervix and vagina will be discussed.

SEARCH METHODS

A systematic search of full-text articles available in PubMed and Embase databases was conducted to identify relevant studies published between January 2000 and September 2021. The search terms included: bioengineering, reproduction, artificial, biomaterial, microfluidic, bioprinting, organoid, hydrogel, scaffold, uterus, endometrium, ovary, fallopian tubes, oviduct, cervix, vagina, endometriosis, adenomyosis, uterine fibroids, chlamydia, Asherman’s syndrome, intrauterine adhesions, uterine polyps, polycystic ovary syndrome and primary ovarian insufficiency. Additional studies were identified by manually searching the references of the selected articles and of complementary reviews. Eligibility criteria included original, rigorous and accessible peer-reviewed work, published in English, on female reproductive bioengineering techniques in preclinical (in vitro/in vivo/ex vivo) and/or clinical testing phases.

OUTCOMES

Out of the 10 390 records identified, 312 studies were included for systematic review. Owing to inconsistencies in the study measurements and designs, the findings were assessed qualitatively rather than by meta-analysis. Hydrogels and scaffolds were commonly applied in various bioengineering-related studies of the female reproductive tract. Emerging technologies, such as organoids and bioprinting, offered personalized diagnoses and alternative treatment options, respectively. Promising microfluidic systems combining various bioengineering approaches have also shown translational value.

WIDER IMPLICATIONS

The complexity of the molecular, endocrine and tissue-level interactions regulating female reproduction present challenges for bioengineering approaches to replace female reproductive organs. However, interdisciplinary work is providing valuable insight into the physicochemical properties necessary for reproductive biological processes to occur. Defining the landscape of reproductive bioengineering technologies currently available and under development for women can provide alternative models for toxicology/drug testing, ex vivo fertility options, clinical therapies and a basis for future organ regeneration studies.

Ovarian tissue bank for fertility preservation and anti-menopause hormone replacement

Traditional fertility preservation methods such as embryo or oocyte cryopreservation cannot meet the needs of a cancer patient or for personal reasons. The cryopreservation of ovarian tissue can be an alternative and has become a hot spot to preserve fertility or hormone replacement. The freezing of ovarian tissue can be carried out at any time without ovarian hyperstimulation to retrieve follicles. It is an ideal strategy to preserve reproductive function in children, adolescent cancer patients, and patients who are in urgent need of cancer treatment. With the increasing demands of women with premature ovarian failure or in menopause, ovarian tissue transplantation is also an alternative for hormone replacement that can provide physiological doses of hormone levels, which can avoid a series of risks such as thrombosis, breast cancer, or other hormone-dependent tumors, caused by oral hormone replacement. Hence, ovarian tissue banking can be regarded as a mainstream strategy for fertility preservation and anti-menopause hormone replacement in further clinical investigation.

Role of Stem Cells in the Ovarian Tissue Cryopreservation and Transplantation for Fertility Preservation

Although the cancer survival rate has increased, cancer treatments, including chemotherapy and radiotherapy, can cause ovarian failure and infertility in women of reproductive age. Preserving fertility throughout cancer treatment is critical for maintaining quality of life. Fertility experts should propose individualized fertility preservation methods based on the patient’s marital status, pubertal status, partner status, and the urgency of treatment. Widely practiced fertility preservation methods, including ovarian transposition and embryo and oocyte cryopreservation, are inappropriate for prepubertal girls or those needing urgent initiation of cancer treatment. Ovarian tissue cryopreservation and transplantation, an emerging new technology, may be a solution for these cancer patients. The use of stem cells in ovarian tissue cryopreservation and transplantation increases oxygenation, angiogenesis, and follicle survival rates. This review discusses the recent advances in ovarian tissue cryopreservation and transplantation with special focus on the use of stem cells to improve fertilization techniques.

Ovarian tissue damage after grafting: systematic review of strategies to improve follicle outcomes

Frozen-thawed human ovarian tissue endures large-scale follicle loss in the early post-grafting period, characterized by hypoxia lasting around 7 days. Tissue revascularization occurs progressively through new vessel invasion from the host and neoangiogenesis from the graft. Such reoxygenation kinetics lead to further potential damage caused by oxidative stress. The aim of the present manuscript is to provide a systematic review of proangiogenic growth factors, hormones and various antioxidants administered in the event of ovarian tissue transplantation to protect the follicle pool from depletion by boosting revascularization or decreasing oxidative stress. Although almost all investigated studies revealed an advantage in terms of revascularization and reduction in oxidative stress, far fewer demonstrated a positive impact on follicle survival. As the cascade of events driven by ischaemia after transplantation is a complex process involving numerous players, it appears that acting on specific molecular mechanisms, such as concentrations of proangiogenic growth factors, is not enough to significantly mitigate tissue damage. Strategies exploiting the activated tissue response to ischaemia for tissue healing and remodelling purposes, such as the use of antiapoptotic drugs and adult stem cells, are also discussed in the present review, since they yielded promising results in terms of follicle pool protection.

Heterotopic autotransplantation of equine ovarian tissue using intramuscular versus subvulvar grafting sites: Preliminary results

Ovarian tissue transplantation (OTT) is a technique well established and successfully applied in humans using mainly orthotopic or heterotopic transplantation sites. In livestock, OTT is still in its infancy and, therefore, different aspects of the technique, including the efficiency of different heterotopic OTT sites as well as the potential effect of age (i.e., young vs. old mares) in the ovarian graft quality, need to be investigated. The present study investigated the efficacy of the intramuscular (IM) or the novel subvulvar mucosa (SV) heterotopic autotransplantation sites to maintain the survivability of the grafts for 3 and 7 days post-OTT. Ovarian biopsy fragments were obtained in vivo and distributed to the following treatments: Fresh control group (ovarian fragments immediately fixed), SV-3, IM-3, SV-7, and IM-7. During and after graft harvesting, the macroscopic characteristics of the grafts (i.e., adherence, morphology, and bleeding) were scored, and the percentages of morphologically normal and developing preantral follicles as well as the follicular and stromal cell densities of the grafts were evaluated. The results were that similar (P > 0.05) macroscopic scores were observed between both transplantation sites 7 days post-OTT, with positive correlations (P < 0.01) found among adherence, morphology, and bleeding of the grafts. A lower (P < 0.05) percentage of morphologically normal follicles was found 7 days post-OTT in the SV site (82%) compared with the Fresh control group (99%) and IM site (95%); however, the percentages of developing follicles were similar (P > 0.05) between both transplantation sites 7 days post-OTT (30-43%). Although similar (P > 0.05) follicular densities were found in both transplantation sites in young and old mares at 3 and 7 days post-OTT, large individual variation in the follicular depletion rate was observed regardless of transplantation site. The Fresh control group and SV-7 treatments had higher (P < 0.05) stromal cell densities in young and old mares compared with both IM-7 treatments. When comparing transplant sites between young and old mares, the follicular density in old mares and the stromal cell density in young mares were greater (P < 0.05) in the SV than in the IM site. In conclusion, even though the transplantation sites differentially affected some end points, overall comparable findings of the OTT technique using both heterotopic autotransplantation sites (i.e., IM and SV) for equine ovarian tissue were observed.

The Effects of Ovarian Encapsulation on Morphology and Expression of Apoptosis-Related Genes in Vitrified Mouse Ovary

BACKGROUND

The purpose of this study was to determine the effects of alginate hydrogel as a capsule to protect the ovary against possible detrimental effects of vitrification and warming on morphology and expression of apoptosis-related genes in the mouse ovary.

METHODS

In this experimental study, the ovaries from twenty-five female 8-week-old mice were divided into five groups of non-vitrified ovaries, vitrified ovaries, ovaries that were encapsulated with concentrations of 0.5, 0.75 and 1% of alginate hydrogel. The morphological study was performed using hematoxylin and eosin staining. Expression levels of apoptosis-associated genes were quantified in each group by real-time RT-PCR. The one-way ANOVA and post hoc test were used to analyze the data and values of p<0.05 were considered statistically significant.

RESULTS

The results of follicle count showed that the mean of total follicles in all groups was not significantly different. The average number of atretic follicles in vitrified and experimental groups significantly increased in comparison with the nonvitrified group (p=0.001). The results of the evaluation of apoptosis-related genes showed that the ratio of BAX/BCL-2 in experimental groups 1 and 2 was significantly higher than the vitrified group and experimental group 3 (p=0.000). The expression level of caspase 3 gene was not significantly different among all groups.

CONCLUSION

Ovarian encapsulation with used concentrations of alginate hydrogel failed to improve the morphology and molecular aspects of follicles and it was not able to better preserve the intact follicles of vitrified ovaries. However, morphological and molecular findings appear to improve with increasing alginate hydrogel concentration.

Heterotopic autotransplantation of ovarian tissue in a large animal model: Effects of cooling and VEGF

Heterotopic and orthotopic ovarian tissue autotransplantation techniques, currently used in humans, will become promising alternative methods for fertility preservation in domestic and wild animals. Thus, this study describes for the first time the efficiency of a heterotopic ovarian tissue autotransplantation technique in a large livestock species (i.e., horses) after ovarian fragments were exposed or not to a cooling process (4°C/24 h) and/or VEGF before grafting. Ovarian fragments were collected in vivo via an ultrasound-guided biopsy pick-up method and surgically autografted in a subcutaneous site in both sides of the neck in each mare. The blood flow perfusion at the transplantation site was monitored at days 2, 4, 6, and 7 post-grafting using color-Doppler ultrasonography. Ovarian grafts were recovered 7 days post-transplantation and subjected to histological analyses. The exposure of the ovarian fragments to VEGF before grafting was not beneficial to the quality of the tissue; however, the cooling process of the fragments reduced the acute hyperemia post-grafting. Cooled grafts compared with non-cooled grafts contained similar values for normal and developing preantral follicles, vessel density, and stromal cell apoptosis; lower collagen type III fibers and follicular density; and higher stromal cell density, AgNOR, and collagen type I fibers. In conclusion, VEGF exposure before autotransplantation did not improve the quality of grafted tissues. However, cooling ovarian tissue for at least 24 h before grafting can be beneficial because satisfactory rates of follicle survival and development, stromal cell survival and proliferation, as well as vessel density, were obtained.

Ovarian tissue cryopreservation and transplantation to delay menopause: facts and fiction

Ovarian tissue cryopreservation and transplantation (OTCT) is increasingly being used in young cancer patients for fertility restoration and prevention of premature ovarian insufficiency (POI) and has recently been advocated as a method to delay menopause. This is accomplished by cryopreserving ovarian tissue that is excised laparoscopically in thin pieces at a young age. Cryopreserved tissue will be transplanted at menopause, when ovarian function is no longer present. Transplantation may need to be repeated several times to achieve long-term restoration of ovarian function. However, it is unknown whether ovarian grafts result in a normal steroid pulsatile secretion, similar to that present during reproductive years. In addition, it is not known whether the need to restore ovarian activity appears earlier in women who undergo OTCT to delay menopause, although indirect data suggest that this is likely to be true. Until today, no cohort or comparative studies evaluating OTCT as a potential alternative to hormone replacement therapy (HRT) have been published and, thus, there is no evidence to suggest that OTCT is superior to HRT in terms of both efficacy and safety. Given the availability of alternative, established treatments for managing menopausal symptoms, as well as the multiple unanswered questions regarding the method, it is imperative that, before OTCT is regarded as a mainstream technique for management of menopausal symptoms, further evaluation and clinical investigation are undertaken.

Heterotopic ovarian allotransplantation in goats: Preantral follicle viability and tissue remodeling

An appropriate implantation site favors angiogenesis and avoids ovarian tissue damage after tissue grafting. The objective of this study was to evaluate the effects of intramuscular (IM) and subcutaneous (SC) sites for ovarian grafts in goats by evaluating follicular morphology and activation, preantral follicle and stromal cell densities, tissue DNA fragmentation, collagen types I and III depositions, and graft revascularizations. Ovarian cortical tissue was transplanted in IM or SC sites and recovered 7 or 15 days post-transplantation. There was a greater percentage of developing follicles and lesser follicular and stromal cell densities in all grafted tissues as compared to ovarian tissues of the control group. The stromal cell density and percentage of normal follicles were positively associated. At 15 days post-transplantation, tissues at the SC and IM sites had similar amounts of DNA fragmentation and type III collagen content. In contrast, tissues at the SC, as compared with IM site, had greater abundances of collagen type I. Furthermore, there was a positive association between collagen type I and percentage of morphologically normal follicles post-transplantation. In addition to a marked decrease in follicular density 15 days post-transplantation in ovarian grafts at the SC and IM sites, low percentages of normal follicles and follicular activation were observed similarly in both transplantation sites. There were also positive associations of stromal cell density and abundance of type I collagen fibers with the percentage of intact follicles in grafted ovarian tissues.

Single xenotransplant of rat brown adipose tissue prolonged the ovarian lifespan of aging mice by improving follicle survival

Prolonging the ovarian lifespan is attractive and challenging. An optimal clinical strategy must be safe, long-acting, simple, and economical. Allotransplantation of brown adipose tissue (BAT), which is most abundant and robust in infants, has been utilized to treat various mouse models of human disease. Could we use BAT to prolong the ovarian lifespan of aging mice? Could we try BAT xenotransplantation to alleviate the clinical need for allogeneic BAT due to the lack of voluntary infant donors? In the current study, we found that a single rat-to-mouse (RTM) BAT xenotransplantation did not cause systemic immune rejection but did significantly increase the fertility of mice and was effective for more than 5 months (equivalent to 10 years in humans). Next, we did a series of analysis including follicle counting; AMH level; estrous cycle; mTOR activity; GDF9, BMP15, LHR, Sirt1, and Cyp19a level; ROS and annexin V level; IL6 and adiponectin level; biochemical blood indices; body temperature; transcriptome; and DNA methylation studies. From these, we proposed that rat BAT xenotransplantation rescued multiple indices indicative of follicle and oocyte quality; rat BAT also improved the metabolism and general health of the aging mice; and transcriptional and epigenetic (DNA methylation) improvement in F0 mice could benefit F1 mice; and multiple KEGG pathways and GO classified biological processes the differentially expressed genes (DEGs) or differentially methylated regions (DMRs) involved were identical between F0 and F1. This study could be a helpful reference for clinical BAT xenotransplantation from close human relatives to the woman.

Current state and future possibilities of ovarian tissue transplantation

BACKGROUND

As a result of recent developments in cancer treatment, cancer survivorship and survivors' quality of life have been emphasized. Although ovarian tissue cryopreservation (OTC) is an experimental technique, it would be the sole technique for fertility preservation treatment for girls with malignant disease. Indeed, OTC requires ovarian tissue transplantation (OTT) for conception. As for OTC, there is room to investigate OTT. The present review focused on the current state and progress of OTT.

METHOD

The literature regarding OTT, which is currently under development, was reviewed.

MAIN FINDINGS

To improve the outcome of OTT, both efficacy and safety are important. Good surgical technique and the optimal site are important surgical factors, with orthotopic transplantation increasing. Treatment of growth factors, gonadotropins, antioxidants, apoptosis suppression factors, and cell therapy may improve the efficacy of OTT by inducing neo-angiogenesis and preventing damage. Artificial ovaries, complete in vitro primordial follicle culture technique, and non-invasive ovarian imaging techniques, such as optical coherence tomography, to select the best ovarian tissue are future possibilities.

CONCLUSION

Improving neo-angiogenesis and preventing damage with optimization, as well as investigation of future techniques, may bring us to the next stage of a fertility preservation strategy.

Reciprocal stimulating effects of bFGF and FSH on chicken primordial follicle activation through AKT and ERK pathway

Basic fibroblast growth factor (bFGF) and follicle-stimulating hormone (FSH) both play important roles in primordial follicle development. Here we investigated the reciprocal stimulation effects of a cytokine bFGF and FSH on primordial follicle development in the chicken and considered a possible signaling mechanism involving protein kinase B (AKT) and extracellular regulated protein kinase (ERK) pathways. 4-day-old chicken ovaries were treated with bFGF and FSH for 3 days in culture to investigate the effects of bFGF and FSH on primordial follicle development. Methods included HE staining, immunohistochemistry, quantitate real-time PCR, Western blot and immunofluorescence. A correlated change of bFGF receptor (FGFR1) mRNA expression and time course of primordial follicle activation was revealed in the early chick ovaries. A reciprocal stimulation effect on primordial follicle activation was demonstrated for bFGF and FSH, along with accelerated granulosa cells proliferation and decreased cell apoptosis. The promoting effect of bFGF was attenuated by the FGFR1 inhibitor SU5402 where the percentage of growing follicles had decreased. AKT and ERK signaling pathways mediated the action of bFGF and FSH in their promotion of primordial follicle activation. Cytokine bFGF and FSH imposed reciprocal stimulating effects on granulosa cell proliferation and anti-apoptosis to promote primordial follicle activation via the PI3K-AKT and ERK signaling pathways in early chick ovaries.

Transcriptome Landscape of Human Folliculogenesis Reveals Oocyte and Granulosa Cell Interactions

The dynamic transcriptional regulation and interactions of human germlines and surrounding somatic cells during folliculogenesis remain unknown. Using RNA sequencing (RNA-seq) analysis of human oocytes and corresponding granulosa cells (GCs) spanning five follicular stages, we revealed unique features in transcriptional machinery, transcription factor networks, and reciprocal interactions in human oocytes and GCs that displayed developmental-stage-specific expression patterns. Notably, we identified specific gene signatures of two cell types in particular developmental stage that may reflect developmental competency and ovarian reserve. Additionally, we uncovered key pathways that may concert germline-somatic interactions and drive the transition of primordial-to-primary follicle, which represents follicle activation. Thus, our work provides key insights into the crucial features of the transcriptional regulation in the stepwise folliculogenesis and offers important clues for improving follicle recruitment in vivo and restoring fully competent oocytes in vitro.

Effect of sustained release of basic fibroblast growth factor using biodegradable gelatin hydrogels on frozen-thawed human ovarian tissue in a xenograft model

AIM

Ovarian tissue cryopreservation before cancer treatment is the only option to preserve fertility under some circumstances. However, tissue ischemia after transplantation while awaiting angiogenesis induces dysfunctional folliculogenesis and reduces ovarian reserve and is one of the disadvantages of frozen-thawed ovarian tissue transplantation. Basic fibroblast growth factor (bFGF) is a major regulator of angiogenesis. However, bFGF rapidly loses biological activity when its free form is injected in vivo. This study investigated whether administration of active bFGF helps establish a nurturing environment for follicular survival.

METHODS

A sheet form of a sustained release drug delivery system for bFGF was developed using biodegradable acidic gelatin hydrogel (bFGF sheet). The bFGF sheets or phosphate-buffered saline sheets, as a negative control, were transplanted with frozen-thawed human ovarian tissues subcutaneously into the backs of severe combined immunodeficient mice. Neovascularization, cell proliferation, fibrosis and follicular survival of ovarian grafts were analyzed at 6 weeks after xenografting.

RESULTS

The bFGF sheets were optimized to release bFGF for at least 10 days. The transplantation of bFGF sheets with frozen-thawed ovarian tissues significantly increased human and mouse CD31-positive areas and stromal and endothelial cell proliferations. The administration of bFGF also significantly decreased the percentage of the fibrotic area in the graft, resulting in a significant increase in primordial and primary follicular density.

CONCLUSION

Local administration of a sustained release of biologically active bFGF induced neovascularization in frozen-thawed ovarian tissue grafts, which could establish the nurturing environment required for follicular survival in heterotopic xenografts.

Comparison of Allotransplantation of Fresh and Vitrified Mouse Ovaries to The Testicular Tissue under Influence of The Static Magnetic Field

Objective

The aim of this study was to investigate the effects of static magnetic field (SMF) during transplantation of the ovarian tissue into the testis.

Materials and Methods

In this experimental study, ovaries of 6- to 8-week-old female Naval Medical Research Institute (NMRI) mice were randomly divided into four groups: i. Fresh ovaries were immediately transplanted into the testicular tissue (FOT group), ii. Fresh ovaries were exposed to the SMF for 10 minutes and then transplanted into the testicular tissue (FOT+group), iii. Vitrified-warmed ovaries were transplanted into the testicular tissue (VOT group), and iv. Vitrified-warmed ovaries were transplanted into the testicular tissue and the transplantation site was then exposed to the SMF for 10 minutes (VOT+group).

Results

The lowest percentages of morphologically dead primordial follicles and the highest percentages of morphologically intact primordial follicles were seen in the FOT+ group (4.11% ± 2.88 and 41.26% ± 0.54, respectively). Although the lowest significant percentage of maturation, embryonic development and fertility was observed in the VOT group as compared to the other groups, the difference in the fertility rate was not significant between the VOT and VOT+groups. Estrogen and progesterone concentrations were significantly higher in the FOT+group than those of the control mice.

Conclusion

It is concluded that, exposure of the vitrified-warmed ovaries to SMF retains the structure of the graft similar to that of fresh ovaries.

Mesenchymal stem cell-derived angiogenin promotes primodial follicle survival and angiogenesis in transplanted human ovarian tissue

BACKGROUND

We have recently reported that human bone marrow-derived mesenchymal stem cells (MSCs) facilitate angiogenesis and prevent follicle loss in xenografted human ovarian tissues. However, the mechanism underlying this effect remains to be elucidated. Thus, determining the paracrine profiles and identifying the key secreted factors in MSCs co-transplanted with ovarian grafts are essential for the future application of MSCs.

METHODS

In this study, we used cytokine microarrays to identify differentially expressed proteins associated with angiogenesis in frozen-thawed ovarian tissues co-transplanted with MSCs. The function of specific secreted factors in MSCs co-transplanted with human ovarian tissues was studied via targeted blockade with short-hairpin RNAi and the use of monoclonal neutralizing antibodies.

RESULTS

Our results showed that angiogenin (ANG) was one of the most robustly up-regulated proteins (among 42 protein we screened, 37 proteins were up-regulated). Notably, the targeted depletion of ANG with short-hairpin RNAi (shANG) or the addition of anti-ANG monoclonal neutralizing antibodies (ANG Ab) significantly reversed the MSC-stimulated angiogenesis, increased follicle numbers and protective effect on follicle apoptosis.

CONCLUSION

Our results indicate that ANG plays a critical role in regulating angiogenesis and follicle survival in xenografted human ovarian tissues. Our findings provide important insights into the molecular mechanism by which MSCs promote angiogenesis and follicle survival in transplanted ovarian tissues, thus providing a theoretical basis for their further application.

Fibrin in Reproductive Tissue Engineering: A Review on Its Application as a Biomaterial for Fertility Preservation

In recent years, reproductive medicine has made good use of tissue engineering and regenerative medicine techniques to develop alternatives to restore fertility in cancer patients. For young female cancer patients who cannot undergo any of the currently applied strategies due to the possible presence of malignant cells in their ovaries, the challenge is creating an in vitro or in vivo artificial ovary using carefully selected biomaterials. Thanks to its numerous qualities, fibrin has been widely used as a scaffold material for fertility preservation applications. The goal of this review is to examine and discuss the applications and advantages of this biopolymer for fertility restoration in cancer patients, and consider the main results achieved so far.

Hyaluronic acid-based hydrogel scaffold without angiogenic growth factors enhances ovarian tissue function after autotransplantation in rats

One of the problems encountered during ovarian transplantation is that the number of primordial follicles in the grafts is considerably reduced 2 d after transplantation due to post-transplantation ischemia. This study investigates if the use of hyaluronic acid-based hydrogel (HABH) with and without vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) could prevent or minimize ischemia-induced follicle loss during ovarian autotransplantation and thereby restore ovarian tissue function in the rat model. In this study, twenty four female rats were subjected to bilateral ovariectomy and were randomly divided into 3 groups for ovarian tissue autotransplantation. Group A included rats with ovarian tissue without HABH, VEGF and bFGF, group B comprised rats with ovarian tissue encapsulated with HABH and group C had rats with ovarian tissue encapsulated with HABH containing VEGF and bFGF. Three days after transplantation, the grafts were assessed through histological and hormonal analyses. Apoptotic, angiogenic and maturation genes expressions were also analyzed. The mean number of follicles in all developmental stages increased in group B (P  <  0.05). The level of FSH decreased in group B (P  <  0.05) whereas, the expression level of VEGF gene increased in group B (P  <  0.05). No significant changes were observed in the expression levels of maturation and apoptotic genes in all groups. In conclusion, ovarian encapsulation with HABH alone can prevent or minimize ischemia-induced follicle loss, preserve the follicular pool, promote follicular survival, facilitate angiogenesis, and restore hormone levels. However, its efficiency in a clinical setting and in comparison with other hydrogels needs further investigation.

VEGF and FGF2 Improve Revascularization, Survival, and Oocyte Quality of Cryopreserved, Subcutaneously-Transplanted Mouse Ovarian Tissues

This study was conducted to investigate the effect of the vascular endothelial growth factor (VEGF) and fibroblast growth factor 2 (FGF2) on revascularization, survival, and oocyte quality of cryopreserved, subcutaneously-transplanted mouse ovarian tissue. Autologous subcutaneous transplantation of vitrified-thawed mouse ovarian tissues treated with (experimental group) or without (control group) VEGF and FGF2 was performed. After transplantation to the inguinal region for two or three weeks, graft survival, angiogenesis, follicle development, and oocyte quality were examined after gonadotropin administration. VEGF coupled with FGF2 (VEGF/FGF2) promoted revascularization and significantly increased the survival rate of subcutaneously-transplanted cryopreserved ovarian tissues compared with untreated controls. The two growth factors did not show long-term effects on the ovarian grafts. In contrast to the untreated ovarian grafts, active folliculogenesis was revealed as the number of follicles at various stages and of mature oocytes in antral follicles after gonadotropin administration were remarkably higher in the VEGF/FGF2-treated groups. Although the fertilization rate was similar between the VEGF/FGF2 and control groups, the oocyte quality was much better in the VEGF/FGF2-treated grafts as demonstrated by the higher ratio of blastocyst development. Introducing angiogenic factors, such as VEGF and FGF2, may be a promising strategy to improve revascularization, survival, and oocyte quality of cryopreserved, subcutaneously-transplanted mouse ovarian tissue.

bFGF and VEGF improve the quality of vitrified-thawed human ovarian tissues after xenotransplantation to SCID mice

PURPOSE

The aim of this research is to study whether basic fibroblast growth factor (bFGF) alone or in combination with vascular endothelial growth factor (VEGF) could improve the quality of vitrified-thawed human ovarian tissue xenotransplanted to severe combined immune deficiency (SCID) mice.

METHODS

After collection and cryopreservation, thawed human ovarian tissue were cultured in vitro for 2 days and then xenografted to severe combined immune deficiency (SCID) mice for 7 days. The in vitro culture medium was separated into six groups, including (A) the blank control group, (B) the human recombinant bFGF (150 ng/ml) group, (C) the bFGF (150 ng/ml)+human recombinant VEGF (25 ng/ml) group, (D) bFGF (150 ng/ml)+VEGF (50 ng/ml) group, (E) bFGF (150 ng/ml)+ VEGF (75 ng/ml) group and (F) bFGF (150 ng/ml) + VEGF (100 ng/ml) group. In addition, eight pieces of thawed ovarian tissue were transplanted without in vitro culture, which serve as the fresh control group. The effect of transplantation was assessed by histological analysis, immunohistochemical staining for CD34, Ki-67, and AC-3 expression, and microvessel density (MVD).

RESULTS

There was no significant difference between the fresh and blank control group. Compared to the blank control group, the number of follicles, MVD, and rate of Ki-67-positive cells increased significantly in groups B, C, D, E, and F, while apoptosis decreased significantly. Compared to the bFGF treatment group, no significant difference appeared in group C, D, E, and F.

CONCLUSIONS

The administration of bFGF alone or in combination with VEGF improved the quality of postgraft human ovarian tissue, though VEGF, regardless of different concentrations, did not influence effect of bFGF.

Developmental Status: Impact of Short-Term Ischemia on Follicular Survival of Whole Ovarian Transplantation in a Rabbit Model

Ischemia is the first mechanism that provokes the loss of follicles in ovarian grafts over the long term. In whole ovarian transplantation, it remains unknown, however, how changes in follicular development are influenced by short-term ischemia. Fresh whole ovarian orthotopic auto-transplantation was performed in rabbits with 45 min ischemia, and the impact of ischemia on follicular survival and development status was evaluated at different time-points (1 day, 3 days, 1 week, 2 weeks and 1 month). Assessment of follicular quantity and morphology was carried out via histologic analysis. Follicle proliferating status was evidenced by immunostaining with proliferating cell nuclear antigen (PCNA), and the Hedgehog signaling pathway (Patched and Gli); was verified via TUNEL assay. Quantitative PCR was carried out to quantify the mRNA of target genes including PCNA, Patched, Gli, Caspase 3, Bax, and Bcl-2. Compared with its contralateral fresh controls, the morphology, proliferation and apoptosis of the follicles in the grafts showed no significant differences and most primordial follicles were quiescent. However, morphology and proliferation status were significantly decreased 1 week after grafting, in comparison with the longitudinal grafting time. Patched and Gli in the Hedgehog signaling pathway were activated in only the follicles of the grafts. Short-term ischemia slightly impacts follicular survival and development status in whole ovarian grafting. Receiving intervention in the first week post-transplantation might be helpful.

Scaffold-based delivery of adipose tissue-derived stem cells in rat frozen-thawed ovarian autografts: preliminary studies in a rat model

PURPOSE

This study aimed to evaluate whether a gelatin-based Gelfoam sponge is feasible as a scaffold for adipose tissue-derived stem cell (ASC) therapy in rat frozen-thawed ovarian autografts.

METHODS

Two sets of studies were performed. The in vitro set evaluated ASCs' viability in the Gelfoam scaffold at different times of co-culturing (after 24, 48, 72, 96, and 120 h). The in vivo set used 20 12-week-old adult female Wistar rats. Frozen-thawed ovarian grafts were treated with ASCs delivered in Gelfoam scaffolds immediately after an autologous retroperitoneal transplant (ASCs-GS, n = 10). The controls received Gelfoam with a culture medium (GS, n = 10). Assessment of graft quality was conducted by vaginal smears (until euthanasia on the 30th postoperative day), histological analyses, follicular density, and viability and fibrosis. Immunohistochemical staining for VEGF-A expression, vascular network (vWF), apoptosis (caspase-3 and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)), cell proliferation (Ki-67), and hormone receptors (estrogen and progesterone) were performed.

RESULTS

The cells remained viable in Gelfoam for up to 120 h of co-culturing. The graft morphology was similar among the groups. ASC therapy promoted the earlier resumption of the estrous phase (GS 16.6 ± 3 vs. ASCs-GS 12.8 ± 1.3 days) and enhanced estrogen receptors compared with the controls (p < 0.05) without interfering with the quantity and viability of the ovarian follicles, fibrosis, endothelial cells, VEGF immunoexpression, apoptosis, or cell proliferation (p > 0.05).

CONCLUSION

The Gelfoam scaffold could be a feasible and safe non-invasive technique for ASC delivery in the treatment of frozen-thawed ovarian autografts. Future studies should evaluate the real benefit of this treatment on the survival and endocrine activity of the graft.

Effect of Local Basic Fibroblast Growth Factor and Vascular Endothelial Growth Factor on Subcutaneously Allotransplanted Ovarian Tissue in Ovariectomized Mice

Objective

One of the major obstacles to ovarian tissue preservation is delayed angiogenesis that leads follicles lost after transplantation. The aim of the present study was to investigate the effects of bFGF and VEGF on heterotopic transplanted ovarian tissue using a mouse model.

Methods

Female mice underwent bilateral ovariectomy. Ovarian tissues encapsulated by fibrin hydrogels were transplanted subcutaneously into recipient mice, in which ovarian hormonal cyclicity was absent. The fibrinogen solution was mixed with bFGF, VEGF, or a mixture of bFGF and VEGF. The grafts were recovered 21 days after transplantation. Follicle morphology and follicle numbers were observed by H&E staining. Blood vessels were observed in transplanted intra-ovarian tissue by CD31 antibody IHC staining. Daily vaginal cytology was performed to determine estrous cycle and functional restoration of transplanted ovarian tissue. Blood was collected weekly and serum FSH levels were measured with a radioimmunoassay kit. Apoptosis analysis was performed by anti-AC-3 staining and survivin mRNA expression.

Results

The number of primordial follicles and secondary follicles in the bFGF+VEGF group was significantly higher than in the control group. The vascular density in the bFGF+VEGF groups were significantly higher than in the bFGF and the VEGF groups; there was no significant difference between the bFGF and VEGF groups. Estrous cycle was earlier in the bFGF+VEGF group compared with the control group; all mice in this group restored ovarian function. Serum FSH levels in the bFGF+VEGF group were significantly lower than in the control group by day 14 post-transplantation. The AC-3-positive in control group was significantly higher compared with bFGF group and VEGF group, and in bFGF+VEGF group was significantly lower than bFGF group and VEGF group. Survivin mRNA expression in bFGF+VEGF group was significantly higher than control group.

Conclusion

The combination of bFGF and VEGF has beneficial effects on follicle survival, angiogenesis, and resumption of estrous cycles.

Basic fibroblast growth factor promotes macaque follicle development in vitro

Fertility preservation is an important type of frontier scientific research in the field of reproductive health. The culture of ovarian cortices to i) initiate primordial follicle growth and ii) procure developing follicles for later oocyte maturation is a promising fertility preservation strategy, especially for older women or cancer patients. At present, this goal remains largely unsubstantiated in primates because of the difficulty in attaining relatively large follicles via ovarian cortex culture. To overcome this hurdle, we cultured macaque monkey ovarian cortices with FSH, kit ligand (KL), basic fibroblast growth factor (bFGF), and/or epidermal growth factor (EGF). The various factors and factor combinations promoted primordial follicle development to different extents. Notably, both bFF (bFGF, 100 ng/ml and FSH, 50 ng/ml) and KF (KL, 100 ng/ml and FSH, 50 ng/ml) contributed to the activation of primordial follicles at day 12 (D12) of culture, whereas at D18, the proportions of developing follicles were significantly higher in the bFF and KF groups relative to the other treatment groups, particularly in the bFF group. Estradiol and progesterone production were also highest in the bFF group, and primary follicle diameters were the largest. Up until D24, the bFF group still exhibited the highest proportion of developing follicles. In conclusion, the bFGF–FSH combination promotes nonhuman primate primordial follicle developmentin vitro, with the optimal experimental window within 18 days. These results provide evidence for the future success of human ovarian cortex culture and the eventual acquisition of mature human follicles or oocytes for fertility restoration.

Life is three dimensional-as in vitro cancer cultures should be

For many decades, fundamental cancer research has relied on two-dimensional in vitro cell culture models. However, these provide a poor representation of the complex three-dimensional (3D) architecture of living tissues. The more recent 3D culture systems, which range from ridged scaffolds to semiliquid gels, resemble their natural counterparts more closely. The arrangement of the cells in 3D systems allows better cell-cell interaction and facilitates extracellular matrix secretion, with concomitant effects on gene and protein expression and cellular behavior. Many studies have reported differences between 3D and 2D systems as regards responses to therapeutic agents and pivotal cellular processes such as cell differentiation, morphology, and signaling pathways, demonstrating the importance of 3D culturing for various cancer cell lines.

Mesenchymal Stem Cells Enhance Angiogenesis and Follicle Survival in Human Cryopreserved Ovarian Cortex Transplantation

Transplantation of cryopreserved ovarian tissue is a novel technique to restore endocrine function and fertility especially for cancer patients. However, the main obstacle of the technique is massive follicle loss as a result of ischemia in the process of transplantation. Mesenchymal stem cells (MSCs) have been acknowledged to play an important role in supporting angiogenesis and stabilizing long-lasting blood vessel networks through release of angiogenic factors and differentiation into pericytes and endothelial cells. This study is aimed to investigate whether MSCs could be applied to overcome the above obstacle to support the ovarian tissue survival in the transplantation. Here we show that human MSCs could enhance the expression level of VEGF, FGF2, and especially the level of angiogenin, significantly stimulate neovascularization, and increase blood perfusion of the grafts in the cryopreserved ovarian tissue transplantation. Further studies reveal that MSCs could notably reduce the apoptotic rates of primordial follicles and decrease follicle loss in the grafted ovarian tissues. In summary, our findings demonstrate a previously unrecognized function of MSCs in improving human ovarian tissue transplantation and provide a useful strategy to optimize fertility preservation and restoration.

Basic fibroblast growth factor promotes the development of human ovarian early follicles during growth in vitro

STUDY QUESTION

What is the effect of basic fibroblast growth factor (bFGF) on the growth of individual early human follicles in a three-dimensional (3D) culture system in vitro?

SUMMARY ANSWER

The addition of 200 ng bFGF/ml improves human early follicle growth, survival and viability during growth in vitro.

WHAT IS KNOWN ALREADY

It has been demonstrated that bFGF enhances primordial follicle development in human ovarian tissue culture. However, the growth and survival of individual early follicles in encapsulated 3D culture have not been reported.

STUDY DESIGN, SIZE, DURATION

The maturation in vitro of human ovarian follicles was investigated. Ovarian tissue (n= 11) was obtained from 11 women during laparoscopic surgery for gynecological disease, after obtaining written informed consent. One hundred and fifty-four early follicles were isolated by enzymic digestion and mechanical disruption. They were individually encapsulated into alginate (1% w/v) and randomly assigned to be cultured with 0, 100, 200 or 300 ng bFGF/ml for 8 days.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Individual follicles were cultured in minimum essential medium α (αMEM) supplemented with bFGF. Follicle survival and growth were assessed by microscopy. Follicle viability was evaluated under confocal laser scanning microscope following Calcein-AM and Ethidium homodimer-I (Ca-AM/EthD-I) staining.

MAIN RESULTS AND THE ROLE OF CHANCE

After 8 days in culture, all 154 follicles had increased in size. The diameter and survival rate of the follicles and the percentage with good viability were significantly higher in the group cultured with 200 ng bFGF/ml than in the group without bFGF (P < 0.05). The percentage of follicles in the pre-antral stage was significantly higher in the 200 ng bFGF/ml group than in the group without bFGF (P < 0.05), while the percentages of primordial and primary follicles were significantly lower (P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

The study focuses on the effect of bFGF on the development of individual human early follicles in 3D culture in vitro and has limited ability to reveal the specific effect of bFGF at each different stage. The findings highlight the need to improve the acquisition and isolation of human ovarian follicles.

WIDER IMPLICATIONS OF THE FINDINGS

The in vitro 3D culture of human follicles with appropriate dosage of bFGF offers an effective method to investigate their development. Moreover, it allows early follicles to be cultured to an advanced stage and therefore has the potential to become an important source of mature oocytes for assisted reproductive technology; particularly as an option for fertility preservation in women, including patients with cancer.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Basic Research Program of China (2011|CB944504, 2011CB944503) and the National Natural Science Foundation of China (81200470, 81000275, 31230047, 8110197). There are no conflicts of interest to declare.