Promoting extracellular matrix remodeling via ascorbic acid enhances the survival of primary ovarian follicles encapsulated in alginate hydrogels

Growth factor-loaded ovarian extracellular matrix hydrogels promote in vivo ovarian niche regeneration and enhance fertility in premature ovarian insufficiency preclinical models

Premature ovarian insufficiency (POI) means menopause before 40 years of age affecting about 1 % of women. Approaches based on cell therapy and the paracrine effects of stem cells or bioproducts such as platelet-rich plasma have been proposed, but concerns remain about undesired systemic effects, as well as the need to optimize delivery methods through bioengineering methods. This study explores the efficacy of decellularized bovine ovarian cortex extracellular matrix (OvaECM) hydrogels alone and as a growth factor (GF) carrier (OvaECM+GF) in a chemotherapy-induced POI murine model. In vitro assays showed a gradual release of GF from the OvaECM sustained for two weeks. Chemotherapy drastically reduced follicle numbers, but OvaECM+GF treatment restored pre-antral follicle development. Moreover, this treatment notably regenerated the ovarian microenvironment by increasing cell proliferation and microvessel density while reducing chemotherapy-induced apoptosis and fibrosis. Whole-ovary RNA sequencing and gene set enrichment analysis revealed an upregulation of regeneration-related genes and a downregulation of apoptotic pathways. The OvaECM+GF treatment also yielded significantly better outcomes following ovarian stimulation and in vitro fertilization. After two consecutive crossbreeding cycles, OvaECM+GF-treated mice showed normal reproductive function. This research showcases the biocompatibility and efficacy of OvaECM to reverse POI in mice, setting a foundation to explore innovative bioengineering-based POI therapies. STATEMENT OF SIGNIFICANCE: Premature ovarian insufficiency (POI) affects about 1 % of women worldwide, causing early menopause before 40 years old. Current treatments alleviate symptoms but do not restore ovarian function. This study explores an innovative approach using ovarian cortex extracellular matrix hydrogels to deliver growth factors into the murine ovarian niche and reverse POI. In vitro release kinetic assays demonstrated a gradual and sustained release of growth factors. In a POI-induced mouse model, intraovarian injections of the hydrogel encapsulating growth factors restored pre-antral follicle development, increased cell proliferation, reduced apoptosis and fibrosis, and improved ovarian response and in vitro fertilization outcomes. Long-term benefits included larger litter sizes. This innovative technique shows promise in regenerating the ovarian environment and improving reproductive outcomes.

The effect of vitamin C on the recovery of activity and survival of autografted ovaries through inhibition of oxidation and inflammation

Ovarian tissue autografting is a valuable clinical option to help restore fertility in women with cancer. However, many follicles are lost due to ischemia-reperfusion (IR) injury, which depletes follicles after grafting. We aimed to investigate the effect of vitamin C, an antioxidant with anti-apoptotic and anti-inflammatory properties, on improving the structure and function of autografted ovaries in mice. Thirty-six female NMRI mice (4-5 weeks old) were divided into three groups of 12: control (no grafting), autograft + vitamin C (50 mg/kg/day intraperitoneally), and autograft + saline (100 µl/day/animal, intraperitoneally). After the ovarian autografting and before the start of the experiment, each group was further divided into 7-day and 28-day subgroups. Seven days after ovary autografting, serum levels of malondialdehyde (MDA), total antioxidant capacity (TAC), and inflammatory factors were measured. On day 28, ovarian histology, DNA fragmentation, and estradiol and progesterone levels were assessed. Results were analyzed using one-way ANOVA and Tukey's test, with significance set at p<0.05. In the autograft + vitamin C group, there were significant increases in the mean total volume of the ovary, cortex (p<0.05), medulla, number of follicles, and levels of IL-10, progesterone, estradiol, and TAC (p<0.001), compared to the autograft group. Conversely, the rate of apoptosis and serum levels of MDA, IL-6, and TNF-α were notably reduced in the autograft + vitamin C group (p<0.001). These results suggest that vitamin C can significantly enhance the recovery of autografted ovaries through its antioxidant, anti-inflammatory, and anti-apoptotic effects.

Vitamin C Improves Oocyte In Vitro Maturation and Potentially Changes Embryo Quality in Cattle

To obtain high-quality bovine oocytes, the effects of vitamin C (VC) on the IVM of bovine oocytes and early embryo development were investigated. The results showed the following. (1) The IVM medium containing 50 µg/mL VC improved the oocyte maturation rate but did not affect the parthenogenetic embryo development. (2) The IVC medium containing 20 µg/mL VC improved the cleavage rate of the IVF embryos and enhanced the mRNA transcriptions of pluripotency gene Oct4, Sox2, Cdx2, and Nanog in the blastocysts but had no effects on the blastocyst rate. (3) Combining supplementation of 50 µg/mL VC in IVM medium + 20 µg/mL VC in IVC medium (named as VC 50/20, similar hereinafter) elevated the cleavage rate of IVF embryos and enhanced the mRNA expressions of Oct4, Sox2, Cdx2, and Nanog in the blastocysts. (4) Combination of VC 0/20 and VC 50/20 enhanced the transcription of anti-apoptotic gene Bcl-2 and VC 50/0 weakened the transcription of pro-apoptotic gene Bax, while VC 0/40 and VC 0/60 increased Bax expression and diminished the Bcl-2/Bax ratio in blastocysts. Together, employing 50 µg/mL VC improves the IVM of bovine oocytes and combination of VC 50/20 potentially changes bovine embryo quality by enhancing the expressions of the pluripotency genes and regulating the expressions of apoptosis-related genes.

Bioengineered 3D ovarian model for long-term multiple development of preantral follicle: bridging the gap for poly(ε-caprolactone) (PCL)-based scaffold reproductive applications

BACKGROUND

Assisted Reproductive Technologies (ARTs) have been validated in human and animal to solve reproductive problems such as infertility, aging, genetic selection/amplification and diseases. The persistent gap in ART biomedical applications lies in recapitulating the early stage of ovarian folliculogenesis, thus providing protocols to drive the large reserve of immature follicles towards the gonadotropin-dependent phase. Tissue engineering is becoming a concrete solution to potentially recapitulate ovarian structure, mostly relying on the use of autologous early follicles on natural or synthetic scaffolds. Based on these premises, the present study has been designed to validate the use of the ovarian bioinspired patterned electrospun fibrous scaffolds fabricated with poly(ε-caprolactone) (PCL) for multiple preantral (PA) follicle development.

METHODS

PA follicles isolated from lamb ovaries were cultured on PCL scaffold adopting a validated single-follicle protocol (Ctrl) or simulating a multiple-follicle condition by reproducing an artificial ovary engrafted with 5 or 10 PA (AO5PA and AO10PA). The incubations were protracted for 14 and 18 days before assessing scaffold-based microenvironment suitability to assist in vitro folliculogenesis (ivF) and oogenesis at morphological and functional level.

RESULTS

The ivF outcomes demonstrated that PCL-scaffolds generate an appropriate biomimetic ovarian microenvironment supporting the transition of multiple PA follicles towards early antral (EA) stage by supporting follicle growth and steroidogenic activation. PCL-multiple bioengineering ivF (AO10PA) performed in long term generated, in addition, the greatest percentage of highly specialized gametes by enhancing meiotic competence, large chromatin remodeling and parthenogenetic developmental competence.

CONCLUSIONS

The study showcased the proof of concept for a next-generation ART use of PCL-patterned scaffold aimed to generate transplantable artificial ovary engrafted with autologous early-stage follicles or to advance ivF technologies holding a 3D bioinspired matrix promoting a physiological long-term multiple PA follicle protocol.

Generation of Tailored Extracellular Matrix Hydrogels for the Study of In Vitro Folliculogenesis in Response to Matrisome-Dependent Biochemical Cues

While ovarian tissue cryopreservation (OTC) is an important fertility preservation option, it has its limitations. Improving OTC and ovarian tissue transplantation (OTT) must include extending the function of reimplanted tissue by reducing the extensive activation of primordial follicles (PMFs) and eliminating the risk of reimplanting malignant cells. To develop a more effective OTT, we must understand the effects of the ovarian microenvironment on folliculogenesis. Here, we describe a method for producing decellularized extracellular matrix (dECM) hydrogels that reflect the protein composition of the ovary. These ovarian dECM hydrogels were engineered to assess the effects of ECM on in vitro follicle growth, and we developed a novel method for selectively removing proteins of interest from dECM hydrogels. Finally, we validated the depletion of these proteins and successfully cultured murine follicles encapsulated in the compartment-specific ovarian dECM hydrogels and these same hydrogels depleted of EMILIN1. These are the first, optically clear, tailored tissue-specific hydrogels that support follicle survival and growth comparable to the "gold standard" alginate hydrogels. Furthermore, depleted hydrogels can serve as a novel tool for many tissue types to evaluate the impact of specific ECM proteins on cellular and molecular behavior.

Co-encapsulation and release of apigenin and ascorbic acid in polyelectrolyte multilayer capsules for targeted polycystic ovary syndrome

Polycystic ovary syndrome (PCOS), a prevalent endocrine disorder in women of reproductive age, is linked to hormonal imbalances and oxidative stress. Our study investigates the regenerative potential of apigenin (AP, hydrophobic) and ascorbic acid (AC, hydrophilic) encapsulated within poly (allylamine hydrochloride) and dextran sulfate (PAH/DS) hollow microcapsules for PCOS. These microcapsules, constructed using a layer-by-layer (LbL) assembly, are found to be 4 ± 0.5 μm in size. Our research successfully demonstrates the co-encapsulation of AP and AC in a single PAH/DS system with high encapsulation efficiency followed by successful release at physiological conditions by CLSM investigations. In vitro tests with testosterone-treated CHO cells reveal that the dual-drug-loaded PAH/DS capsules effectively reduce intracellular ROS levels and apoptosis and offering protection. In an in-vivo zebrafish model, these capsules demonstrate active biodistribution to targeted ovaries and reduce testosterone levels through radical scavenging. Histopathological examinations show that the injected dual-drug-loaded PAH/DS microcapsules assist in the development of ovarian follicles in testosterone-treated zebrafish. Hence, this dual-drug-loaded system, capable of co-encapsulating two natural compounds, effectively interacts with ovarian cells, reducing cellular damage and normalizing PCOS conditions.

In Vitro Growth of Human Follicles: Current and Future Perspectives

Ovarian tissue cryopreservation is gaining importance as a successful method to restore fertility to girls and young women at high risk of sterility. However, there are concerns regarding the safety of transplantation after ovarian tissue cryopreservation due to the high risk of reintroducing cancer cells and causing disease recurrence. In these cases, the development of culture systems that support oocyte development from the primordial follicle stage is required. Notable achievements have been reached in human follicle in vitro growth in the past decade. Currently, systems for the in vitro culture of ovarian tissue are based on two-dimensional substrates that do not support the survival of follicles or recapitulate the mechanical heterogenicity in the mammalian ovary. Recognition of the importance of special arrangements between cells has spurred research in three-dimensional culture systems, and the provision of a precise culture system that maximizes the diffusion of nutrients and gases through the follicles has raised interest in advanced biomimetic models. The current review critically examines various culture systems employed for the in vitro development of follicles, with a particular focus on solutions utilizing Organ-on-a-Chip (OOC) technology. The emphasis on OOC technology underscores its role as a promising avenue in ensuring the successful cultivation and maintenance of follicular structures during the culture period.

Facilitation of Ovarian Response by Mechanical Force-Latest Insight on Fertility Improvement in Women with Poor Ovarian Response or Primary Ovarian Insufficiency

The decline in fertility in aging women, especially those with poor ovarian response (POR) or primary ovarian insufficiency (POI), is a major concern for modern IVF centers. Fertility treatments have traditionally relied on gonadotropin- and steroid-hormone-based IVF practices, but these methods have limitations, especially for women with aging ovaries. Researchers have been motivated to explore alternative approaches. Ovarian aging is a complicated process, and the deterioration of oocytes, follicular cells, the extracellular matrix (ECM), and the stromal compartment can all contribute to declining fertility. Adjunct interventions that involve the use of hormones, steroids, and cofactors and gamete engineering are two major research areas aimed to improve fertility in aging women. Additionally, mechanical procedures including the In Vitro Activation (IVA) procedure, which combines pharmacological activators and fragmentation of ovarian strips, and the Whole Ovary Laparoscopic Incision (WOLI) procedure that solely relies on mechanical manipulation in vivo have shown promising results in improving follicle growth and fertility in women with POR and POI. Advances in the use of mechanical procedures have brought exciting opportunities to improve fertility outcomes in aging women with POR or POI. While the lack of a comprehensive understanding of the molecular mechanisms that lead to fertility decline in aging women remains a major challenge for further improvement of mechanical-manipulation-based approaches, recent progress has provided a better view of how these procedures promote folliculogenesis in the fibrotic and avascular aging ovaries. In this review, we first provide a brief overview of the potential mechanisms that contribute to ovarian aging in POI and POR patients, followed by a discussion of measures that aim to improve ovarian folliculogenesis in aging women. At last, we discuss the likely mechanisms that contribute to the outcomes of IVA and WOLI procedures and potential future directions.

Advances of xenogeneic ovarian extracellular matrix hydrogels for in vitro follicle development and oocyte maturation

Research aimed at preserving female fertility is increasingly using bioengineering techniques to develop new platforms capable of supporting ovarian cell function in vitro and in vivo. Natural hydrogels (alginate, collagen, and fibrin) have been the most exploited approaches; however they are biologically inert and/or biochemically simple. Thus, establishing a suitable biomimetic hydrogel from decellularized ovarian cortex (OC) extracellular matrix (OvaECM) could provide a complex native biomaterial for follicle development and oocyte maturation. The objectives of this work were (i) to establish an optimal protocol to decellularize and solubilize bovine OC, (ii) to characterize the histological, molecular, ultrastructural, and proteomic properties of the resulting tissue and hydrogel, and (iii) to assess its biocompatibility and adequacy for murine in vitro follicle growth (IVFG). Sodium dodecyl sulfate was identified as the best detergent to develop bovine OvaECM hydrogels. Hydrogels added into standard media or used as plate coatings were employed for IVFG and oocyte maturation. Follicle growth, survival, hormone production, and oocyte maturation and developmental competence were evaluated. OvaECM hydrogel-supplemented media best supported follicle survival, expansion, and hormone production, while the coatings provided more mature and competent oocytes. Overall, the findings support the xenogeneic use of OvaECM hydrogels for future human female reproductive bioengineering.

Recapitulating folliculogenesis and oogenesis outside the body: encapsulated in vitro follicle growth†

Folliculogenesis is a tightly coordinated process essential for generating a fertilization-competent gamete while also producing gonadal hormones that sustain endocrine function. In vitro follicle growth systems have been critical to our understanding of key events in folliculogenesis, such as gonadotropin-independent and dependent growth, steroid hormone production, and oocyte growth and maturation (cytoplasmic and meiotic). Although there are several successful follicle culture strategies, the following protocol details an encapsulated in vitro follicle growth (eIVFG) system for use with mouse ovarian follicles. Encapsulated IVFG is performed with alginate hydrogels, which are biologically inert, maintains cell-to-cell interactions between granulosa cells and the oocyte, and preserves follicle architecture as found in the ovary. The system supports follicle growth, development, and differentiation from the early primary follicle to the antral follicle stage. Moreover, post-folliculogenesis events including meiotic maturation, ovulation, and luteinization are also supported. Importantly, the culture of secondary follicles has successfully resulted in viable pups after blastocyst transfer. This alginate-based eIVFG system is versatile and has broad applications as a tool for interrogating the fundamental biology of the ovarian follicle in a controlled manner, a screening platform for toxicity and bioactivity, and a potential fertility preservation method for endangered species as well as humans.

Biomechanical forces and signals operating in the ovary during folliculogenesis and their dysregulation: implications for fertility

BACKGROUND

Folliculogenesis occurs in the highly dynamic environment of the ovary. Follicle cyclic recruitment, neo-angiogenesis, spatial displacement, follicle atresia and ovulation stand out as major events resulting from the interplay between mechanical forces and molecular signals. Morphological and functional changes to the growing follicle and to the surrounding tissue are required to produce oocytes capable of supporting preimplantation development to the blastocyst stage.

OBJECTIVE AND RATIONALE

This review will summarize the ovarian morphological and functional context that contributes to follicle recruitment, growth and ovulation, as well as to the acquisition of oocyte developmental competence. We will describe the changes occurring during folliculogenesis to the ovarian extracellular matrix (ECM) and to the vasculature, their influence on the mechanical properties of the ovarian tissue, and, in turn, their influence on the regulation of signal transduction. Also, we will outline how their dysregulation might be associated with pathologies such as polycystic ovary syndrome (PCOS), endometriosis or premature ovarian insufficiency (POI). Finally, for each of these three pathologies, we will highlight therapeutic strategies attempting to correct the altered biomechanical context in order to restore fertility.

SEARCH METHODS

For each area discussed, a systematic bibliographical search was performed, without temporal limits, using PubMed Central, Web of Science and Scopus search engines employing the keywords extracellular matrix, mechanobiology, biomechanics, vasculature, angiogenesis or signalling pathway in combination with: ovary, oogenesis, oocyte, folliculogenesis, ovarian follicle, theca, granulosa, cumulus, follicular fluid, corpus luteum, meiosis, oocyte developmental competence, preimplantation, polycystic ovary syndrome, premature ovarian insufficiency or endometriosis.

OUTCOMES

Through search engines queries, we yielded a total of 37 368 papers that were further selected based on our focus on mammals and, specifically, on rodents, bovine, equine, ovine, primates and human, and also were trimmed around each specific topic of the review. After the elimination of duplicates, this selection process resulted in 628 papers, of which 287 were cited in the manuscript. Among these, 89.2% were published in the past 22 years, while the remaining 8.0%, 2.4% or 0.3% were published during the 1990s, 1980s or before, respectively. During folliculogenesis, changes occur to the ovarian ECM composition and organization that, together with vasculature modelling around the growing follicle, are aimed to sustain its recruitment and growth, and the maturation of the enclosed oocyte. These events define the scenario in which mechanical forces are key to the regulation of cascades of molecular signals. Alterations to this context determine impaired folliculogenesis and decreased oocyte developmental potential, as observed in pathological conditions which are causes of infertility, such as PCOS, endometriosis or POI.

WIDER IMPLICATIONS

The knowledge of these mechanisms and the rules that govern them lay a sound basis to explain how follicles recruitment and growth are modulated, and stimulate insights to develop, in clinical practice, strategies to improve follicular recruitment and oocyte competence, particularly for pathologies like PCOS, endometriosis and POI.

Cell derived matrices from bovine corneal endothelial cells as a model to study cellular dysfunction

PURPOSE

Fuchs endothelial corneal dystrophy (FECD) is a progressive corneal disease that impacts the structure and stiffness of the Descemet's membrane (DM), the substratum for corneal endothelial cells (CECs). These structural alterations of the DM could contribute to the loss of the CECs resulting in corneal edema and blindness. Oxidative stress and transforming growth factor-β (TGF-β) pathways have been implicated in endothelial cell loss and endothelial to mesenchymal transition of CECs in FECD. Ascorbic acid (AA) is found at high concentrations in FECD and its impact on CEC survival has been investigated. However, how TGF-β and AA effect the composition and rigidity of the CEC's matrix remains unknown.

METHODS

In this study, we investigated the effect of AA, TGF-β1 and TGF-β3 on the deposition, ultrastructure, stiffness, and composition of the extracellular matrix (ECM) secreted by primary bovine corneal endothelial cells (BCECs).

RESULTS

Immunofluorescence and electron microscopy post-decellularization demonstrated a robust deposition and distinct structure of ECM in response to treatments. AFM measurements showed that the modulus of the matrix in BCECs treated with TGF-β1 and TGF-β3 was significantly lower than the controls. There was no difference in the stiffness of the matrix between the AA-treated cell and controls. Gene Ontology analysis of the proteomics results revealed that AA modulates the oxidative stress pathway in the matrix while TGF-β induces the expression of matrix proteins collagen IV, laminin, and lysyl oxidase homolog 1.

CONCLUSIONS

Molecular pathways identified in this study demonstrate the differential role of soluble factors in the pathogenesis of FECD.

A bioengineered in situ ovary (ISO) supports follicle engraftment and live-births post-chemotherapy

Female cancer patients who have undergone chemotherapy have an elevated risk of developing ovarian dysfunction and failure. Experimental approaches to treat iatrogenic infertility are evolving rapidly; however, challenges and risks remain that hinder clinical translation. Biomaterials have improved in vitro follicle maturation and in vivo transplantation in mice, but there has only been marginal success for early-stage human follicles. Here, we developed methods to obtain an ovarian-specific extracellular matrix hydrogel to facilitate follicle delivery and establish an in situ ovary (ISO), which offers a permissive environment to enhance follicle survival. We demonstrate sustainable follicle engraftment, natural pregnancy, and the birth of healthy pups after intraovarian microinjection of isolated exogenous follicles into chemotherapy-treated (CTx) mice. Our results confirm that hydrogel-based follicle microinjection could offer a minimally invasive delivery platform to enhance follicle integration for patients post-chemotherapy.

Three-Dimensional Culture for In Vitro Folliculogenesis in the Aspect of Methods and Materials

In vitro ovarian follicle culture is a reproduction technique used to obtain fertilizable oocytes, for overcoming fertility issues due to premature ovarian failure. This requires the establishment of an in vitro culture model that is capable of better simulating the in vivo ovarian growth environment. Two-dimensional (2D) culture systems have been successfully set up in rodent models. However, they are not suitable for larger animal models as the follicles of larger animals cultured in 2D culture systems often lose their shape due to dysfunction in the gap junctions. Three-dimensional (3D) culture systems are more suitable for maintaining follicle architecture, and therefore are proposed for the successful in vitro culturing of follicles in various animal models. The role of different methods, scaffolds, and suspension cultures in supporting follicle development has been studied to provide direction for improving in vitro follicle culture technologies. The three major strategies for in vitro 3D follicle cultures are discussed in this article. First, the in vitro culture systems, such as microfluidics, hanging drop, hydrogels, and 3D-printing, are reviewed. We have focused on the 3D hydrogel system as it uses different materials for supporting follicular growth and oocyte maturation in several animal models and in humans. We have also discussed the criteria used for biomaterial evaluations such as solid concentration, elasticity, and rigidity. In addition, future research directions for advancing in vitro 3D follicle culture system are discussed. Impact statement A new frontier in assisted reproductive technology is in vitro tissue or follicle culture, particularly for fertility preservation. The in vitro three-dimensional (3D) culture technique enhances follicular development and provides mature oocytes, overcoming the limitations of traditional in vitro two-dimensional cultures. Polymer biomaterials have good compatibility and retain the physiological structure of follicles in the 3D culture system. Utilizing hybrid in vitro culture materials by merging matrix, hydrogel, and unique patterned materials may facilitate follicular growth in the future.

Advanced bioengineering of female germ cells to preserve fertility

Oogenesis and folliculogenesis are considered as complex and species-specific cellular differentiation processes, which depend on the in vivo ovarian follicular environment and endocrine cues. Considerable efforts have been devoted to driving the differentiation of female primordial germ cells toward mature oocytes outside of the body. The recent experimental attempts have laid stress on offering a suitable microenvironment to assist the in vitro folliculogenesis and oogenesis. Despite developing a variety of bioengineering techniques and generating functional mature gametes through in vitro oogenesis in earlier studies, we still lack knowledge of appropriate microenvironment conditions for building biomimetic culture systems for female fertility preservation. Therefore, this review paper can provide a source for a large body of scientists developing cutting-edge in vitro culture systems for female germ cells or setting up the next generation of reproductive medicine as feasible options for female infertility treatment. The focal point of this review outlines advanced bioengineering technologies such as 3D biofabricated hydrogels/scaffolds and microfluidic systems utilized with female germlines for fertility preservation through in vitro folliculogenesis and oogenesis.

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.

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.

In vitro production of viable eggs from isolated mouse primary follicles by successive culture

To produce viable eggs from single primary follicles in vitro, primary follicles containing oocytes (average 39.0 ± 0.2 µm in diameter) were isolated from the ovaries of 1-week-old mice, and cultured in combination with culture membranes for the first 8 days up to the secondary follicle stage, followed by the next 12 days to the later stages. After culture with a combination of first and second culture membranes using high and low adhesion characteristics, the average oocyte diameters of the surviving follicles increased by almost two-fold in all four groups. Further, the oocyte maturation rate was the highest (74.1%) in the culture group with low adhesion with collagenase and high adhesion. In this culture group, when the O₂ concentration was changed from 20% in the first culture to 5% in the second culture, the cleavage rate increased to 47.5%, which was comparable to the level of the in vivo control (34.6%). Finally, 39 embryos at the 2- to 8-cell stages were transferred into the oviducts of three pseudopregnant females, and eight live pups (20.5%) were obtained. Of the eight pups, six survived for at least six months and were fertile. The present study shows successive in vitro cultures of single isolated primary follicles for the production of viable eggs. We believe that this culture system, with a combination of culture membranes under controlled O₂ conditions, is applicable to other mammalian species, including humans.

Sequestered cell-secreted extracellular matrix proteins improve murine folliculogenesis and oocyte maturation for fertility preservation

Synthetic matrices offer a high degree of control and tunability for mimicking extracellular matrix functions of native tissue, allowing the study of disease and development in vitro. In this study, we functionalized degradable poly(ethylene glycol) hydrogels with extracellular matrix (ECM)-sequestering peptides aiming to recapitulate the native ECM composition for culture and maturation of ovarian follicular organoids. We hypothesized that ECM-sequestering peptides would facilitate deposition and retention of cell-secreted ECM molecules, thereby recreating cell-matrix interactions in otherwise bioinert PEG hydrogels. Specifically, heparin-binding peptide from antithrombin III (HBP), heparan sulfate binding peptide derived from laminin (AG73), basement membrane binder peptide (BMB), and heparan sulfate binding region of placental growth factor 2 (RRR) tethered to a PEG hydrogel significantly improved follicle survival, growth and maturation compared to PEG-Cys, a mechanically similar but biologically inert control. Immunohistochemical analysis of the hydrogel surrounding cultured follicles confirmed sequestration and retention of laminin, collagen I, perlecan, and fibronectin in ECM-sequestering hydrogels but not in bioinert PEG-Cys hydrogels. The media from follicles cultured in PEG-AG73, PEG-BMB, and PEG-RRR also had significantly higher concentrations of factors known to regulate follicle development compared to PEG-Cys. PEG-AG73 and PEG-BMB were the most beneficial for promoting follicle maturation, likely because AG73 and BMB mimic basement membrane interactions which are crucial for follicle development. Here we have shown that functionalizing PEG with ECM-sequestering peptides allows cell-secreted ECM to be retained within the hydrogels, restoring critical cell-matrix interactions and promoting healthy organoid development in a fully synthetic culture system. STATEMENT OF SIGNIFICANCE: Here we present a novel approach for sequestering and retaining cell-secreted extracellular matrix in a fully synthetic material for organoid culture. We have engineered a biomimetic poly(ethylene glycol) hydrogel functionalized with extracellular matrix-binding peptides to recapitulate the ovarian microenvironment. Incorporation of these peptides allows ovarian follicles to recreate their native matrix with the sequestered ECM that subsequently binds growth factors, facilitating follicle maturation. The novel design resulted in improved outcomes of folliculogenesis, potentially developing a fertility preservation option for young women undergoing sterilizing treatments for cancer. The fully synthetic and modular nature of this biomimetic material holds promise for other tissue engineering applications as it allows encapsulated cells to rebuild their native microenvironments in vitro.

Capitalizing on transcriptome profiling to optimize and identify targets for promoting early murine folliculogenesis in vitro

In vitro ovarian follicle culture is an active area of research towards providing fertility options for survivors of childhood cancer. Late-stage murine follicles (multilayer secondary and onwards) can be cultured successfully to maturity to obtain a meiotically competent oocyte for fertilization, but primordial and primary follicles usually die in culture because many key components of early follicle development are still unknown and difficult to mimic in vitro. To engineer a biomimetic three-dimensional culture system with high efficacy and reproducibility for the clinic, detailed mechanisms of early folliculogenesis must be uncovered. Previous studies have shown that primary murine follicles co-cultured in groups, in contrast to single follicles cultured in isolation, can reach preovulatory size and produce competent oocytes, but the factors accounting for the synergy of follicle co-culture are still unknown. To probe the underlying mechanisms of successful follicle co-culture, we conducted a time-course experiment for murine follicles encapsulated in 0.3% alginate hydrogels and compared between two conditions: groups of 5 (5X) versus groups of 10 (10X). For every 2 days during the course of 12 days, follicles were dissociated and somatic cells were isolated for microarray-based gene expression analysis (n = 380 follicles for 5X and n = 430 follicles for 10X). Gene activities in follicles co-cultured in larger groups (10X) had a distinct transcriptomic profile of key genes and pathways such as prolactin signaling and angiogenesis-related genes when compared to cells from follicles co-cultured in the smaller cohort (5X). To benchmark the results for follicles grown in culture, we compared our microarray data to data from murine follicles freshly isolated from the ovary at comparable stages of development previously published by Bernabé et al. Comparison of these datasets identified similarities and differences between folliculogenesis in the native microenvironment and the engineered in vitro system. A more detailed understanding of follicle growth in vitro will not only allow for better culture methods but also advance the field towards providing improved fertility options for survivors of childhood cancer.

Three-dimensional bioprinting of artificial ovaries by an extrusion-based method using gelatin-methacryloyl bioink

PURPOSE

The aim of this study was to design and fabricate a three-dimensional (3D) printed artificial ovary.

METHODS

We first compared the printability of gelatin-methacryloyl (GelMA), alginate and GelMA-alginate bioinks, of which GelMA was selected for further investigation. The swelling properties, degradation kinetics and shape fidelity of GelMA scaffolds were characterized by equilibrium swelling/lyophilization, collagenase processing and micro-computed tomography evaluation. Commercial ovarian tumor cell lines (COV434, KGN, ID8) and primary culture ovarian somatic cells were utilized to perform cell-laden 3D printing, and the results were evaluated by live/dead assays and TUNEL detection. Murine ovarian follicles were seeded in the ovarian scaffold and their diameters were recorded every day. Finally, in vitro maturation was performed, and the ovulated oocytes were collected and observed.

RESULTS

Our results indicated that GelMA was suitable for 3D printing fabrication. Its scaffolds performed well in terms of hygroscopicity, degradation kinetics and shape fidelity. The viability of ovarian somatic cells was lower than that of commercial cell lines, suggesting that extrusion-based 3D culture fabrication is not suitable for primary ovarian cells. Nevertheless, the GelMA-based 3D printing system provided an appropriate microenvironment for ovarian follicles, which successfully grew and ovulated in the scaffolds. Metaphase II oocytes were also observed after in vitro maturation.

CONCLUSIONS

The GelMA-based 3D printing culture system is a viable alternative option for follicular growth, development and transfer. Accordingly, it shows promise for clinical application in the treatment of female endocrine and reproductive conditions.

Ascorbic acid can promote the generation and expansion of neuroepithelial-like stem cells derived from hiPS/ES cells under chemically defined conditions through promoting collagen synthesis

INTRODUCTION

Spinal cord injury (SCI) is a neurological, medically incurable disorder. Human pluripotent stem cells (hPSCs) have the potential to generate neural stem/progenitor cells (NS/PCs), which hold promise in the treatment of SCI by transplantation. In our study, we aimed to establish a chemically defined culture system using serum-free medium and ascorbic acid (AA) to generate and expand long-term self-renewing neuroepithelial-like stem cells (lt-NES cells) differentiated from hPSCs effectively and stably.

METHODS

We induced human embryonic stem cells (hESCs)/induced PSCs (iPSCs) to neurospheres using a newly established in vitro induction system. Moreover, lt-NES cells were derived from hESC/iPSC-neurospheres using two induction systems, i.e., conventional N2 medium with gelatin-coated plates (coated) and N2+AA medium without pre-coated plates (AA), and were characterized by reverse transcription polymerase chain reaction (RT-PCR) analysis and immunocytochemistry staining. Subsequently, lt-NES cells were induced to neurons. A microelectrode array (MEA) recording system was used to evaluate the functionality of the neurons differentiated from lt-NES cells. Finally, the mechanism underlying the induction of lt-NES cells by AA was explored through RNA-seq and the use of inhibitors.

RESULTS

HESCs/iPSCs were efficiently induced to neurospheres using a newly established induction system in vitro. lt-NES cells derived from hESC/iPSC-neurospheres using the two induction systems (coated vs. AA) both expressed the neural pluripotency-associated genes PAX6, NESTIN, SOX1, and SOX2. After long-term cultivation, we found that they both exhibited long-term expansion for more than a dozen generations while maintaining neuropluripotency. Moreover, the lt-NES cells retained the ability to differentiate into general functional neurons that express β-tubulin at high levels. We also demonstrated that AA promotes the generation and long-term expansion of lt-NES cells by promoting collagen synthesis via the MEK-ERK1/2 pathway.

CONCLUSIONS

This new chemically defined culture system was stable and effective regarding the generation and culture of lt-NES cells induced from hESCs/iPSCs using serum-free medium combined with AA. The lt-NES cells induced under this culture system maintained their long-term expansion and neural pluripotency, with the potential to differentiate into functional neurons.

Ovarian stiffness increases with age in the mammalian ovary and depends on collagen and hyaluronan matrices

Fibrosis is a hallmark of aging tissues which often leads to altered architecture and function. The ovary is the first organ to show overt signs of aging, including increased fibrosis in the ovarian stroma. How this fibrosis affects ovarian biomechanics and the underlying mechanisms are unknown. Using instrumental indentation, we demonstrated a quantitative increase in ovarian stiffness, as evidenced by an increase in Young's modulus, when comparing ovaries from reproductively young (6-12 weeks) and old (14-17 months) mice. This ovarian stiffness was dependent on collagen because ex vivo enzyme-mediated collagen depletion in ovaries from reproductively old mice restored their collagen content and biomechanical properties to those of young controls. In addition to collagen, we also investigated the role of hyaluronan (HA) in regulating ovarian stiffness. HA is an extracellular matrix glycosaminoglycan that maintains tissue homeostasis, and its loss can change the biomechanical properties of tissues. The total HA content in the ovarian stroma decreased with age, and this was associated with increased hyaluronidase (Hyal1) and decreased hyaluronan synthase (Has3) expression. These gene expression differences were not accompanied by changes in ovarian HA molecular mass distribution. Furthermore, ovaries from mice deficient in HAS3 were stiffer compared to age-matched WT mice. Our results demonstrate that the ovary becomes stiffer with age and that both collagen and HA matrices are contributing mechanisms regulating ovarian biomechanics. Importantly, the age-associated increase in collagen and decrease in HA are conserved in the human ovary and may impact follicle development and oocyte quality.

Ameliorating Effects of Natural Antioxidant Compounds on Female Infertility: a Review

The prevalence of female infertility cases has been increasing at a frightening rate, affecting approximately 48 million women across the world. However, oxidative stress has been recognized as one of the main mediators of female infertility by causing various reproductive pathologies in females such as endometriosis, PCOS, preeclampsia, spontaneous abortion, and unexplained infertility. Nowadays, concerned women prefer dietary supplements with antioxidant properties over synthetic drugs as a natural way to lessen the oxidative stress and enhance their fertility. Therefore, the current review is an attempt to explore the efficacy of various natural antioxidant compounds including vitamins, carotenoids, and plant polyphenols and also of some medicinal plants in improving the fertility status of females. Our summarization of recent findings in the current article would pave the way toward the development of new possible antioxidant therapy to treat infertility in females. Natural antioxidant compounds found in fruits, vegetables, and other dietary sources, alone or in combination with other antioxidants, were found to be effective in ameliorating the oxidative stress-mediated infertility problems in both natural and assisted reproductive settings. Numerous medicinal plants showed promising results in averting the various reproductive disorders associated with female infertility, suggesting a plant-based herbal medicine to treat infertility. Although optimum levels of natural antioxidants have shown favorable results, however, their excessive intake may have adverse health impacts. Therefore, larger well-designed, dose-response studies in humans are further warranted to incorporate natural antioxidant compounds into the clinical management of female infertility.

Lessons from bioengineering the ovarian follicle: a personal perspective

The ovarian follicle and its maturation captivated my imagination and inspired my scientific journey - what we know now about this remarkable structure is captured in this invited review. In the past decade, our knowledge of the ovarian follicle expanded dramatically as cross-disciplinary collaborations brought new perspectives to bear, ultimately leading to the development of extragonadal follicles as model systems with significant clinical implications. Follicle maturation in vitro in an 'artificial' ovary became possible by learning what the follicle is fundamentally and autonomously capable of - which turns out to be quite a lot. Progress in understanding and harnessing follicle biology has been aided by engineers and materials scientists who created hardware that enables tissue function for extended periods of time. The EVATAR system supports extracorporeal ovarian function in an engineered environment that mimics the endocrine environment of the reproductive tract. Finally, applying the tools of inorganic chemistry, we discovered that oocytes require zinc to mature over time - a truly new aspect of follicle biology with no antecedent other than the presence of zinc in sperm. Drawing on the tools and ideas from the fields of bioengineering, materials science and chemistry unlocked follicle biology in ways that we could not have known or even predicted. Similarly, how today's basic science discoveries regarding ovarian follicle maturation are translated to improve the experience of tomorrow's patients is yet to be determined.

In vitro ovarian follicle growth: a comprehensive analysis of key protocol variables†

Folliculogenesis is a complex process that requires integration of autocrine, paracrine, and endocrine factors together with tightly regulated interactions between granulosa cells and oocytes for the growth and survival of healthy follicles. Culture of ovarian follicles is a powerful approach for investigating folliculogenesis and oogenesis in a tightly controlled environment. This method has not only enabled unprecedented insight into the fundamental biology of follicle development but also has far-reaching translational applications, including in fertility preservation for women whose ovarian follicles may be damaged by disease or its treatment or in wildlife conservation. Two- and three-dimensional follicle culture systems have been developed and are rapidly evolving. It is clear from a review of the literature on isolated follicle culture methods published over the past two decades (1980-2018) that protocols vary with respect to species examined, follicle isolation methods, culture techniques, culture media and nutrient and hormone supplementation, and experimental endpoints. Here we review the heterogeneity among these major variables of follicle culture protocols.

Harnessing mesenchymal stem cell secretome: Effect of extracellular matrices on proangiogenic signaling

The low engraftment and retention rate of mesenchymal stem cells (MSCs) at the target site indicates that the potential benefits of MSC-based therapies can be attributed to their paracrine signaling. In this study, the extracellular matrices (ECMs) deposited by bone marrow-derived human MSCs in the presence and absence of ascorbic acid was characterized. MSCs were seeded on top of decellularized ECM (dECM) and the concentrations of proangiogenic and antiangiogenic molecules released in culture (conditioned) media was compared. Effects of ECM derived from MSCs with different passage numbers on MSC secretome was also investigated. Our study revealed that the expression of proangiogenesis-related factors were upregulated when MSCs were harvested on dECMs, irrespective of media supplementation, as compared with those cultured on tissue culture plates. In addition, dECM generated in the presence of ascorbic acid promoted the expression of proangiogenic molecules as compared with dECM-derived in absence of media supplementation. Further, it was observed that the effectiveness of dECM to stimulate proangiogenic signaling of MSCs was reduced as cell passage number was increased from P3 to P5. The proliferation as well as capillary morphogenesis of human umbilical vein endothelial cells (HUVECs) in the presence of conditioned media were enhanced compared with the normal HUVECs culture media. These data indicate that the secretory signatures of MSCs and consequently, the therapeutic efficacy of MSCs can be regulated by presentation of dECM composition and variation of its composition.

The in vitro Analysis of Quality of Ovarian Follicle Culture Systems Using Time-Lapse Microscopy and Quantitative Real-Time PCR

BACKGROUND

The aim of ovarian follicle in vitro culture is to obtain mature oocytes. To evaluate the efficiency of in vitro culture system, the status of the cultured oocyte can be analyzed.

METHODS

The preantral ovarian follicles retrieved from 14-day-old C57Bl/6J mice were cultured in 3D alginate hydrogel. The status of oocytes obtained from mature (3 months old, group A) and immature (3 weeks old, group B) mice was compared to the status of oocytes retrieved from ovarian follicles cultured in vitro (Group C) using qRT-PCR analysis and time-lapse microscopy. In the qRT-PCR analysis, 8 samples for group A (80 oocytes), 8 samples for group B (80 oocytes), and 6 samples for group C (60 oocytes) were included. Time-lapse analysis was performed in group A (oocytes n=31), group B (n=45), and group C (n=21). Statistical analysis was done by Kruskal-Wallis and chi-square tests and differences were considered statistically significant if p<0,05.

RESULTS

The diameter of group C oocytes is lower in comparison to group A oocytes (67 μm vs. 75 μm, correspondingly). Groups B and C oocytes exhibited delayed meiosis in comparison to group A oocytes. Expression levels of six oocyte maturation genes (Ccnb, CDK1, Ccnh, Wee2, Mos and Epab) were evaluated using qRT-PCR analysis. Expression levels of Ccnh and Epab are lowered in group C oocytes compared to the expression levels of these genes in groups A and B oocytes (p< 0.05).

CONCLUSION

Oocytes obtained after ovarian follicles in vitro culture have reduced development competence, future fundamental changes of in vitro culture systems can be expected.

Supplemented powdered coconut water (ACP-406®) promotes growth of goat secondary follicles and oocyte meiotic resumption

The objective of this study was to test the efficiency of powdered coconut water (ACP-406^®) base-medium without or with the addition of supplements on in vitro culture of isolated goat secondary follicles. Follicles were cultured for 18 days in α-MEM or in ACP-406^®, both without supplements (referred to as α-MEM and ACP, respectively), or both supplemented with BSA, insulin, transferrin, selenium, glutamine, hypoxanthine, and ascorbic acid (referred to as α-MEM⁺ and ACP⁺). Follicular morphology, antrum formation, follicular and oocyte diameter, levels of glutathione (GSH), and chromatin configuration after in vitro maturation were evaluated. At the end of culture, ACP-406^® base-medium (without or with supplements) showed a higher (P < 0.05) percentage of normal follicles than α-MEM (without or with supplements). Antrum formation was similar among α-MEM⁺, ACP and ACP⁺, and significantly higher than α-MEM without supplements. The follicular diameter was greater in ACP⁺ than α-MEM, and similar to other treatments. Moreover, fully and daily grown rates were higher (P < 0.05) in ACP-406^® base-medium (without or with supplements) than α-MEM (without or with supplements). Levels of GSH were similar between ACP⁺ and α-MEM⁺ treatments. Both ACP⁺ and α-MEM⁺ allowed meiotic resumption without a significant difference between the two groups. In conclusion, supplemented ACP-406^® base-medium maintained follicular survival and promoted the development as well as meiotic resumption of isolated goat secondary follicles cultured in vitro for 18 days.

Vitamin C protects carboplatin-exposed oocytes from meiotic failure

CBP (carboplatin) is a second-generation chemotherapeutic drug of platinum compound commonly applied in the treatment of sarcomas and germ cell tumours. Although it is developed to replace cisplatin, which has been proven to have a variety of side effects during cancer treatment, CBP still exhibits a certain degree of toxicity including neurotoxicity, nephrotoxicity, hematotoxicity and myelosuppression. However, the underlying mechanisms regarding how CBP influences the female reproductive system especially oocyte quality have not yet been fully determined. Here, we report that CBP exposure led to the oocyte meiotic defects by impairing the dynamics of the meiotic apparatus, leading to a remarkably aberrant spindle organisation, actin polymerisation and mitochondrial integrity. Additionally, CBP exposure caused compromised sperm binding and fertilisation potential of oocytes by due to an abnormal distribution of cortical granules and its component ovastacin. More importantly, we demonstrated that vitamin C supplementation prevented meiotic failure induced by CBP exposure and inhibited the increase in ROS levels, DNA damage accumulation and apoptotic incidence. Taken together, our findings demonstrate the toxic effects of CBP exposure on oocyte development and provide a potential effective way to improve the quality of CBP-exposed oocytes in vitro.

Dynamic genome-scale cell-specific metabolic models reveal novel inter-cellular and intra-cellular metabolic communications during ovarian follicle development

BACKGROUND

The maturation of the female germ cell, the oocyte, requires the synthesis and storing of all the necessary metabolites to support multiple divisions after fertilization. Oocyte maturation is only possible in the presence of surrounding, diverse, and changing layers of somatic cells. Our understanding of metabolic interactions between the oocyte and somatic cells has been limited due to dynamic nature of ovarian follicle development, thus warranting a systems approach.

RESULTS

Here, we developed a genome-scale metabolic model of the mouse ovarian follicle. This model was constructed using an updated mouse general metabolic model (Mouse Recon 2) and contains several key ovarian follicle development metabolic pathways. We used this model to characterize the changes in the metabolism of each follicular cell type (i.e., oocyte, granulosa cells, including cumulus and mural cells), during ovarian follicle development in vivo. Using this model, we predicted major metabolic pathways that are differentially active across multiple follicle stages. We identified a set of possible secreted and consumed metabolites that could potentially serve as biomarkers for monitoring follicle development, as well as metabolites for addition to in vitro culture media that support the growth and maturation of primordial follicles.

CONCLUSIONS

Our systems approach to model follicle metabolism can guide future experimental studies to validate the model results and improve oocyte maturation approaches and support growth of primordial follicles in vitro.

FertiPROTEKT, Oncofertility Consortium and the Danish Fertility-Preservation Networks - What Can We Learn From Their Experiences?

Fertility preservation is an increasingly important discipline. It requires close coordination between reproductive medicine specialists, reproductive biologists, and oncologists in various disciplines. In addition, it represents a particular health policy challenge, since fertility-protection measures are to be understood as a treatment for side effects of gonadotoxic treatments and would therefore normally have to be reimbursed by health insurance companies. Therefore, it is inevitable that fertility-preservation activities should organise themselves into a network structure both as a medical-logistic network and as a professional medical society. The necessary network structures can differ significantly at regional, national, and international level, as the size of the regions to be integrated and the local cultural and geographical conditions, as well as the political conditions are very different. To address these issues, the current review aims to point out the basic importance and the chances but also the difficulties of fertility-protection networks and give practical guidance for the development of such network structures. We will not only discuss network structures theoretically but also present them based on three established, different sized networks, such as the Danish Network (www.rigshospitalet.dk), representing a centralised network in a small country; the German-Austrian-Swiss network FertiPROTEKT® (www.fertiprotekt.com), representing a centralised as well as decentralised network in a large country; and the Oncofertility® Consortium (www.oncofertility.northwestern.edu), representing a decentralised, internationally oriented network, primarily serving the transfer of knowledge among its members.

Follicle development as an orchestrated signaling network in a 3D organoid

The ovarian follicle is the structural and functional unit of the ovary, composed of the female gamete (the oocyte) and supportive somatic cells. Follicles are not only the source of a female's germ cell supply, but also secrete important hormones necessary for proper endocrine function. Folliculogenesis, the growth and maturation of the follicular unit, is a complex process governed by both intrafollicular crosstalk and pituitary-secreted hormones. While the later stages of this process are gonadotropin-dependent, early folliculogenesis appears to be controlled by the ovarian microenvironment and intrafollicular paracrine and autocrine signaling. In vitro follicle culture remains challenging because of the limited knowledge of growth factors and other cytokines influencing early follicle growth. Here we discuss the current state of knowledge on paracrine and autocrine signaling influencing primary follicles as they develop into the antral stage. Given the importance of intrafollicular signaling and the ovarian microenvironment, we reviewed the current engineering approaches for in vitro follicle culture, including 3D systems using natural hydrogels such as alginate and synthetic hydrogels such as poly(ethylene glycol). Our discussion is focused on what drives the proliferation of granulosa cells, development of the thecal layer, and antrum formation-three processes integral to follicle growth up to the antral stage. Further research in this area may reveal the mechanisms behind these complex signaling relationships within the follicle, leading to more successful and physiologically-relevant in vitro culture methods that will translate well to clinical applications.

In vitro follicle culture in the context of IVF

The currently available assisted reproduction techniques for fertility preservation (i.e. in vitro maturation (IVM) and in vitro fertilization) are insufficient as stand-alone procedures as only few reproductive cells can be conserved with these techniques. Oocytes in primordial follicles are well suited to survive the cryopreservation procedure and of use as valuable starting material for fertilization, on the condition that these could be grown up to fully matured oocytes. Our understanding of the biological mechanisms directing primordial follicle activation has increased over the last years and this knowledge has paved the way toward clinical applications. New multistep in vitro systems are making use of purified precursor cells and extracellular matrix components and by applying bio-printing technologies, an adequate follicular niche can be built. IVM of human oocytes is clinically applied in patients with polycystic ovary/polycystic ovary syndrome; related knowhow could become useful for fertility preservation and for patients with maturation failure and follicle-stimulating hormone resistance. The expectations from the research on human ovarian tissue and immature oocytes cultures, in combination with the improved vitrification methods, are high as these technologies can offer realistic potential for fertility preservation.

Differentially Expressed lncRNAs After the Activation of Primordial Follicles in Mouse

The activation of primordial follicles is critical to ovarian follicle development, which directly influences female fertility and reproductive life span. Several studies have suggested a role for long noncoding RNAs (lncRNAs) in ovarian function. However, the precise involvement of lncRNAs in the initiation of primordial follicles is still unknown. Here, an in vitro culture model was used to investigate the roles of lncRNAs in primordial follicle activation. We found that primordial follicles in day 3 mouse ovaries were activated after culturing for 8 days in vitro, as indicated by ovarian morphology changes, increases in primary follicle number, and downregulation of mammalian Sterile 20-like kinase messenger RNA (mRNA) and upregulation of growth differentiation factor 9 mRNA. We next examined lncRNA expression profiles by RNA sequencing at the transcriptome level and found that among 60 078 lncRNAs, 6541 lncRNA were upregulated and 2135 lncRNA were downregulated in 3-day ovaries cultured for 8 days in vitro compared with ovaries from day 3 mice. We also found that 4171 mRNAs were upregulated and 1795 were downregulated in the cultured ovaries. Gene ontology and pathway analyses showed that the functions of differentially expressed lncRNA targets and mRNAs were closely linked with many processes and pathways related to ovary development, including cell proliferation and differentiation, developmental processes, and other signaling transduction pathways. Additionally, many novel identified lncRNAs showed inducible expression, suggesting that these lncRNAs may be good candidates for investigating mouse primordial follicle activation. This study provides a foundation for further exploring lncRNA-related mechanisms in the initiation of mouse primordial follicles.

Retinoic acid promotes in vitro follicle activation in the cat ovary by regulating expression of matrix metalloproteinase 9

Retinoic acid (RA) facilitates tissue morphogenesis by regulating matrix matalloproteinase (MMPs) expression. Our objective was to examine the influence of RA on in vitro development of follicles enclosed within domestic cat ovarian tissues. Ovarian cortices from 9 prepubertal and 13 adult cats were incubated for 7 d in medium containing 0 (control), 1 or 5 μM RA and then analyzed for viability. Cortices from additional three animals of each age group were cultured in the same condition and follicle morphology, stage and size were histologically evaluated. In a separate study, cortices from 14 donors (7 prepubertal; 7 adult cats) were incubated in 0 or 5 μM RA for 7 d and assessed for (1) MMP1, 2, 3, 7, 9 and TIMP1 expression by qPCR and (2) protein expression of MMP9 by immunohistochemistry. Donor age did not influence follicle response to RA. Collective data from both age groups revealed that percentages of primordial follicles in 5 μM RA treatment were lower (P < 0.05; 40.5 ± 4.5%) than in fresh cortices (66.7 ± 5.3%) or controls (60.1 ± 4.0%) with 1 μM-RA treatment producing intermediate (56.3 ± 4.0%) results. Proportion of primary follicles in 5 μM RA (21.7 ± 3.3%) was higher than in fresh cortices (4.9 ± 2.9%) and controls (9.0 ± 2.8%) with 1 μM-RA treatment producing an intermediate value (13.8 ± 2.0%). Furthermore, proportion of secondary follicles increased after 7 d in the presence of 5 μM RA (9.5 ± 2.7%) compared to other groups (fresh, 1.9 ± 0.8%; control, 2.6 ± 1.1%; 1 μM RA, 2.5 ± 0.2%). MMP9 transcript and protein were upregulated, whereas MMP7 mRNA was suppressed by 5 μM-RA treatment compared to fresh counterparts. RA did not impact MMP1, 2, 3, 13 or TIMP1 expression. In summary, RA activated cat primordial follicle growth likely via a mechanism related to upregulation of MMP9 and down-regulation of MMP7 transcripts.

Anethole reduces oxidative stress and improves in vitro survival and activation of primordial follicles

Primordial follicles, the main source of oocytes in the ovary, are essential for the maintenance of fertility throughout the reproductive lifespan. To the best of our knowledge, there are no reports describing the effect of anethole on this important ovarian follicle population. The aim of the study was to investigate the effect of different anethole concentrations on the in vitro culture of caprine preantral follicles enclosed in ovarian tissue. Randomized ovarian fragments were fixed immediately (non-cultured treatment) or distributed into five treatments: α-MEM⁺ (cultured control), α-MEM⁺ supplemented with ascorbic acid at 50 μg/mL (AA), and anethole at 30 (AN30), 300 (AN300), or 2000 µg/mL (AN2000), for 1 or 7 days. After 7 days of culture, a significantly higher percentage of morphologically normal follicles was observed when anethole at 2000 μg/mL was used. For both culture times, a greater percentage of growing follicles was observed with the AN30 treatment compared to AA and AN2000 treatments. Anethole at 30 and 2000 µg/mL concentrations at days 1 and 7 of culture resulted in significantly larger follicular diameter than in the cultured control treatment. Anethole at 30 µg/mL concentration at day 7 showed significantly greater oocyte diameter than the other treatments, except when compared to the AN2000 treatment. At day 7 of culture, levels of reactive oxygen species (ROS) were significantly lower in the AN30 treatment than the other treatments. In conclusion, supplementation of culture medium with anethole improves survival and early follicle development at different concentrations in the caprine species.

Comparison of the Oocyte Quality Derived from Two-Dimensional Follicle Culture Methods and Developmental Competence of In Vitro Grown and Matured Oocytes

In vitro follicle growth (IVFG) is an emerging fertility preservation technique, which can obtain fertilizable oocytes from an in vitro culture system in female. This study aimed to compare efficiency of the most widely used two-dimensional follicle culture methods [with or without oil layer (O+ or O- group)]. Preantral follicles were isolated from mice and randomly assigned. Follicles were cultured for 10 days and cumulus-oocyte complexes harvested 16-18 hours after hCG treatment. Follicle and oocyte growth, hormones in spent medium, meiotic spindle localization, expression of reactive oxygen species (ROS), mitochondrial activity, and gene expression were evaluated. In follicle growth, survival, pseudoantral cavity formation, ovulation, and oocyte maturation were also significantly higher in O+ group than O- group. Hormone production was significantly higher in follicles cultured in O+ than O-. There were no significant differences in mRNA expression related to development. On the other hand, the level of ROS was increased while the mitochondrial activity of in vitro grown matured oocyte was less than in vivo matured oocytes. In conclusion, follicle culture with O+ group appears to be superior to the culture in O- group in terms of follicle growth, development, oocyte growth, maturation, and microorganelles in oocyte.

Untapped Reserves: Controlling Primordial Follicle Growth Activation

Even with the benefit of assisted reproductive technologies (ART), many women are unable to conceive and deliver healthy offspring. One common cause of infertility is the inability to produce eggs capable of contributing to live birth. This can occur despite standard-of-care treatment to maximize the recovery of eggs from growing ovarian follicles. Dormant primordial follicles in the human ovary are a 'reserve ' that can be exploited clinically to overcome this problem. We discuss how controlling primordial follicle growth activation (PFGA) can produce increased numbers of high-quality eggs available for fertility treatment(s). We consider the state of the art in interventions used to control PFGA, and consider genetic and epigenetic strategies on the horizon that might improve compromised oocyte quality to increase live births.

A bioprosthetic ovary created using 3D printed microporous scaffolds restores ovarian function in sterilized mice

Emerging additive manufacturing techniques enable investigation of the effects of pore geometry on cell behavior and function. Here, we 3D print microporous hydrogel scaffolds to test how varying pore geometry, accomplished by manipulating the advancing angle between printed layers, affects the survival of ovarian follicles. 30° and 60° scaffolds provide corners that surround follicles on multiple sides while 90° scaffolds have an open porosity that limits follicle-scaffold interaction. As the amount of scaffold interaction increases, follicle spreading is limited and survival increases. Follicle-seeded scaffolds become highly vascularized and ovarian function is fully restored when implanted in surgically sterilized mice. Moreover, pups are born through natural mating and thrive through maternal lactation. These findings present an in vivo functional ovarian implant designed with 3D printing, and indicate that scaffold pore architecture is a critical variable in additively manufactured scaffold design for functional tissue engineering.

A bioprosthetic ovary created using 3D printed microporous scaffolds restores ovarian function in sterilized mice

Emerging additive manufacturing techniques enable investigation of the effects of pore geometry on cell behavior and function. Here, we 3D print microporous hydrogel scaffolds to test how varying pore geometry, accomplished by manipulating the advancing angle between printed layers, affects the survival of ovarian follicles. 30° and 60° scaffolds provide corners that surround follicles on multiple sides while 90° scaffolds have an open porosity that limits follicle-scaffold interaction. As the amount of scaffold interaction increases, follicle spreading is limited and survival increases. Follicle-seeded scaffolds become highly vascularized and ovarian function is fully restored when implanted in surgically sterilized mice. Moreover, pups are born through natural mating and thrive through maternal lactation. These findings present an in vivo functional ovarian implant designed with 3D printing, and indicate that scaffold pore architecture is a critical variable in additively manufactured scaffold design for functional tissue engineering.

Tissue Engineered Human Amniotic Membrane Application in Mouse Ovarian Follicular Culture

Since folliculogenesis requires a powerful cell-matrix interaction, natural scaffolds seem to be needed for follicular culture. Human amniotic membrane (HAM) offers promise as a support of in vitro ovarian follicular culture. HAM was decellularized with trypsin and EDTA. DNA and histology assays were performed to determine the elimination rate of genomic components. Cyto-biocompatibility of decellular AM (DAM) was verified by the cell viability (MTT) test. The small parts of intact amniotic membrane (IAM) and DAM were coated on the bottom of 96-well and each well was filled with 150 µL of base medium. Mouse primary-secondary (PS) follicles were separated to three groups: 1-culture in base medium (Control), 2-culture on IAM and 3-culture on DAM. Follicular size, morphology, viability, estradiol production and genes expression were evaluated and IAM group showed better growth and development in follicle culture. The viability rate and estradiol production in both experimental groups were statistically higher than the Control. Gdf9, Bmp15 and Cx37 were found to have higher expression levels in IAM group. Also, maximum apoptotic and survival indexes were determined in Control and IAM groups, respectively. Finally, IAM provides a better protective environment for mouse PS follicular culture that can reduce apoptosis level.

Vitamin C in Stem Cell Biology: Impact on Extracellular Matrix Homeostasis and Epigenetics

Transcription factors and signaling molecules are well-known regulators of stem cell identity and behavior; however, increasing evidence indicates that environmental cues contribute to this complex network of stimuli, acting as crucial determinants of stem cell fate. l-Ascorbic acid (vitamin C (VitC)) has gained growing interest for its multiple functions and mechanisms of action, contributing to the homeostasis of normal tissues and organs as well as to tissue regeneration. Here, we review the main functions of VitC and its effects on stem cells, focusing on its activity as cofactor of Fe⁺²/αKG dioxygenases, which regulate the epigenetic signatures, the redox status, and the extracellular matrix (ECM) composition, depending on the enzymes' subcellular localization. Acting as cofactor of collagen prolyl hydroxylases in the endoplasmic reticulum, VitC regulates ECM/collagen homeostasis and plays a key role in the differentiation of mesenchymal stem cells towards osteoblasts, chondrocytes, and tendons. In the nucleus, VitC enhances the activity of DNA and histone demethylases, improving somatic cell reprogramming and pushing embryonic stem cell towards the naive pluripotent state. The broad spectrum of actions of VitC highlights its relevance for stem cell biology in both physiology and disease.

Efficient biomaterials for tissue engineering of female reproductive organs

Current investigations on the bioengineering of female reproductive tissues have created new hopes for the women suffering from reproductive organ failure including congenital anomaly of the female reproductive tract or serious injuries. There are many surgically restore forms that constitute congenital anomaly, however, to date, there is no treatment except surgical treatment of transplantation for patients who are suffering from anomaly or dysfunction organs like vagina and uterus. Restoring and maintaining the normal function of ovary and uterus require the establishment of biological substitutes that can cover the roles of structural support for cells and passage of secreting molecules. As in the case of constructing other functional organs, reproductive organ manufacturing also needs biological matrices which can provide an appropriate condition for attachment, growth, proliferation and signaling of various kinds of grafted cells. Among the organs, uterus needs special features such as plasticity due to their amazing changes in volume when they are in the state of pregnancy. Although numerous natural and synthetic biomaterials are still at the experimental stage, some biomaterials have already been evaluated their efficacy for the reconstruction of female reproductive tissues. In this review, all the biomaterials cited in recent literature that have ever been used and that have a potential for the tissue engineering of female reproductive organs were reviewed, especially focused on bioengineered ovary and uterus.

Primordial Follicle Transplantation within Designer Biomaterial Grafts Produce Live Births in a Mouse Infertility Model

The gonadotoxic effects of chemotherapy and radiation may result in premature ovarian failure in premenopausal oncology patients. Although autotransplantation of ovarian tissue has led to successful live births, reintroduction of latent malignant cells inducing relapse is a significant concern. In this report, we investigated the design of biomaterial grafts for transplantation of isolated ovarian follicles as a means to preserve fertility. Primordial and primary ovarian follicles from young female mice were extracted and encapsulated into biomaterials for subsequent transplantation into adult mice. Among the formulations tested, aggregated follicles encapsulated within fibrin had enhanced survival and integration with the host tissue following transplantation relative to the fibrin-alginate and fibrin-collagen composites. All mice transplanted with fibrin-encapsulated follicles resumed cycling, and live births were achieved only for follicles transplanted within VEGF-loaded fibrin beads. The extent to which these procedures reduce the presence of metastatic breast cancer cells among the isolated follicles was evaluated, with significantly reduced numbers of cancer cells present relative to intact ovaries. This ability to obtain live births by transplanting isolated primordial and primary follicles, while also reducing the risk of re-seeding disease relative to ovarian tissue transplantation, may ultimately provide a means to preserve fertility in premenopausal oncology patients.

Engineered in vitro disease models

The ultimate goal of most biomedical research is to gain greater insight into mechanisms of human disease or to develop new and improved therapies or diagnostics. Although great advances have been made in terms of developing disease models in animals, such as transgenic mice, many of these models fail to faithfully recapitulate the human condition. In addition, it is difficult to identify critical cellular and molecular contributors to disease or to vary them independently in whole-animal models. This challenge has attracted the interest of engineers, who have begun to collaborate with biologists to leverage recent advances in tissue engineering and microfabrication to develop novel in vitro models of disease. As these models are synthetic systems, specific molecular factors and individual cell types, including parenchymal cells, vascular cells, and immune cells, can be varied independently while simultaneously measuring system-level responses in real time. In this article, we provide some examples of these efforts, including engineered models of diseases of the heart, lung, intestine, liver, kidney, cartilage, skin and vascular, endocrine, musculoskeletal, and nervous systems, as well as models of infectious diseases and cancer. We also describe how engineered in vitro models can be combined with human inducible pluripotent stem cells to enable new insights into a broad variety of disease mechanisms, as well as provide a test bed for screening new therapies.

Initiation of puberty in mice following decellularized ovary transplant

Clinical interventions to preserve fertility and restore hormone levels in female patients with therapy-induced ovarian failure are insufficient, particularly for pediatric cancer patients. Laparoscopic isolation of cortical ovarian tissue followed by cryopreservation with subsequent autotransplantation has temporarily restored fertility in at least 27 women who survived cancer, and aided in pubertal transition for one pediatric patient. However, reintroducing cancer cells through ovarian transplantation has been a major concern. Decellularization is a process of removing cellular material, while maintaining the organ skeleton of extracellular matrices (ECM). The ECM that remains could be stripped of cancer cells and reseeded with healthy ovarian cells. We tested whether a decellularized ovarian scaffold could be created, recellularized and transplanted to initiate puberty in mice. Bovine and human ovaries were decellularized, and the ovarian skeleton microstructures were characterized. Primary ovarian cells seeded onto decellularized scaffolds produced estradiol in vitro. Moreover, the recellularized grafts initiated puberty in mice that had been ovariectomized, providing data that could be used to drive future human transplants and have broader implications on the bioengineering of other organs with endocrine function.

Culture and co-culture of mouse ovaries and ovarian follicles

The mammalian ovary is composed of ovarian follicles, each follicle consisting of a single oocyte surrounded by somatic granulosa cells, enclosed together within a basement membrane. A finite pool of follicles is laid down during embryonic development, when oocytes in meiotic arrest form a close association with flattened granulosa cells, forming primordial follicles. By or shortly after birth, mammalian ovaries contain their lifetime's supply of primordial follicles, from which point onwards there is a steady release of follicles into the growing follicular pool. The ovary is particularly amenable to development in vitro, with follicles growing in a highly physiological manner in culture. This work describes the culture of whole neonatal ovaries containing primordial follicles, and the culture of individual ovarian follicles, a method which can support the development of follicles from an immature through to the preovulatory stage, after which their oocytes are able to undergo fertilization in vitro. The work outlined here uses culture systems to determine how the ovary is affected by exposure to external compounds. We also describe a co-culture system, which allows investigation of the interactions that occur between growing follicles and the non-growing pool of primordial follicles.