In vitro culture of early secondary preantral follicles in hanging drop of ovarian cell-conditioned medium to obtain MII oocytes from outbred deer mice

miR-450-5p and miR-202-5p Synergistically Regulate Follicle Development in Black Goat

Follicle maturation is a complex biological process governed by numerous factors, and researchers have observed follicle development by studying the proliferation and apoptosis of follicular granulosa cells (GCs). However, the regulatory mechanisms of GCs proliferation and death during follicle development are largely unknown. To investigate the regulatory mechanisms of lncRNAs, mRNAs, and microRNAs, RNA sequencing (RNA-seq) and small RNA-seq were performed on large (>10 mm) and small follicles (<3 mm) of Leizhou black goat during estrus. We discovered two microRNAs, miR-450-5p and miR-202-5p, which can target GCs in goats and may be involved in follicle maturation, and the effects of miR-450-5p and miR-202-5p on ovarian granulosa cell lines were investigated (KGN). Using cell counting kit-8 (CCK-8) assays, 5-Ethynyl-2’-deoxyuridine (EdU) assay and flow cytometry, miR-202-5p overexpression could suppress the proliferation and induce apoptosis of GCs, whereas miR-450-5p overexpression induced the opposite effects. The dual-luciferase reporter assay confirmed that miR-450-5p could directly target the BMF gene (a BCL2 modifying factor), and miR-202-5p targeted the BCL2 gene. A considerable rise in phosphorylated Akt (p-AKT) protein was observed following the downregulation of BMF by miR-450-5p mimics. After BMF gene RNAi therapy, a notable elevation in p-AKT was detected. Mimics of miR-202-5p inhibited BCL2 protein expression, significantly decreasing p-AMPK protein expression. These results imply that during the follicular development in black goats, the miR-450-5p-BMF axis favored GC proliferation on a wide scale, while the miR-202-5p-BCL2 axis triggered GC apoptosis.

Germ Cell Isolation and Cryopreservation from Reproductive Organs of Brown Mealworm

This study aimed to isolate and freeze germ cells from the superior brown mealworm. Styrofoam diet changes were observed for 20 days to determine whether mealworms were useful insects for decomposing Styrofoam. The average weight of mealworms before the Styrofoam diet was 500 mg, which decreased to 336 mg at D20 after their diet. To preserve mealworms with excellent Styrofoam-degrading ability, we first isolated the reproductive organs of mealworms, testes, ovaries, sperms, and ovarioles. Morphologically, male and female adult brown mealworms were distinguished according to the presence or absence of a protrusion at the tip of the fifth segment of the abdomen. Sperms and ovarioles were observed in anatomically isolated testes and ovaries. We compared mechanical and enzymatic (collagenase I) methods to effectively isolate ovarioles from adult female brown mealworms. For the enzymatic method, most were torn and burst as the membrane of the ovarioles was damaged by collagenase I, unlike the mechanical method. To preserve the superior genetic resources of mealworms, we cryopreserved the ovaries of female brown mealworms using slow-freezing and vitrification. Histological analysis showed that the yolk sac was completely damaged in the ovaries after slow-freezing. However, only partial damage was achieved in the vitrification group compared to the control group (no freezing). The newly developed vitrification method with alginate-encapsulated ovarioles maintained the yolk sac in the ovarioles but was evenly distributed. These results provide basic data for reproductive studies of other useful insects and contribute to the biobanking and fertility preservation of superior mealworm germ cells and endangered insects.

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.

Assessment of cGMP level in medium during in vitro growth period of murine preantral follicles with and without supplementation of C-type natriuretic peptide

To enhance the developmental competency of murine ovarian follicles cultured in vitro, C-type natriuretic peptide (CNP) was supplemented in the culture system. Although the mechanism is not fully elucidated, it was reported that the effect of CNP supplementation was mediated by increased cyclic guanosine monophosphate (cGMP). In the present study, cGMP levels in media for murine preantral follicle culture were compared both between a control group without CNP supplementation and an experimental group with CNP supplementation and between days in each group. In addition, follicle growth patterns and oocyte maturity were assessed and compared between the two groups. Results demonstrated that along with in vitro culture, cGMP levels increased (P < 0.05) both in the control group and the experimental group, whereas cGMP levels were not significantly different between the two groups on the same day of in vitro culture (P > 0.05). The oocyte's maturity was superior in the experimental group compared with the control group (P < 0.05). As ovarian follicles grew three-dimensionally in the experimental group but were flattened in the control group, CNP might improve oocyte maturity through maintaining the three-dimensional architecture of the ovarian follicle because of increased transzonal projections (TZP) and functional gap junctions between oocyte and surrounding granulosa cells.

Creating an Artificial 3-Dimensional Ovarian Follicle Culture System Using a Microfluidic System

We hypothesized that the creation of a 3-dimensional ovarian follicle, with embedded granulosa and theca cells, would better mimic the environment necessary to support early oocytes, both structurally and hormonally. Using a microfluidic system with controlled flow rates, 3-dimensional two-layer (core and shell) capsules were created. The core consists of murine granulosa cells in 0.8 mg/mL collagen + 0.05% alginate, while the shell is composed of murine theca cells suspended in 2% alginate. Somatic cell viability tests and hormonal assessments (estradiol, progesterone, and androstenedione) were performed on days 1, 6, 13, 20, and 27. Confocal microscopy confirmed appropriate compartmentalization of fluorescently-labeled murine granulosa cells to the inner capsule and theca cells to the outer shell. Greater than 78% of cells present in capsules were alive up to 27 days after collection. Artificially constructed ovarian follicles exhibited intact endocrine function as evidenced by the production of estradiol, progesterone, and androstenedione. Oocytes from primary and early secondary follicles were successfully encapsulated, which maintained size and cellular compartmentalization. This novel microfluidic system successfully encapsulated oocytes from primary and secondary follicles, recapitulating the two-compartment system necessary for the development of the mammalian oocyte. Importantly, this microfluidic system can be easily adapted for sterile, high throughput applications.

Supplementation of c-type natriuretic peptide during in vitro growth period benefits the development of murine preantral follicles

The present study investigated the effects of c-type natriuretic peptide (CNP) on the development of murine preantral follicles during in vitro growth (IVG). Preantral follicles isolated from ovaries of Kunming mice were cultured in vitro. In the culture system, CNP was supplemented in the experimental groups and omitted in the control groups. In Experiment 1, CNP was only supplemented at the early stage and follicle development was evaluated. In Experiments 2 and 3, CNP was supplemented during the whole period of in vitro culture. In Experiment 2, follicle development and oocyte maturity were evaluated. In Experiment 3, follicle development and embryo cleavage after in vitro fertilization (IVF) were assessed. The results showed that in the control groups in all three experiments, granulosa cells migrated from within the follicle and the follicles could not reach the antral stage. In the experimental groups in all three experiments, no migration of granulosa cells was observed and follicle development was assessed as attaining the antral stage, which was significantly superior to that of the control group (P < 0.0001). Oocyte meiotic arrest was effectively maintained, hence giving good developmental competence. In conclusion, CNP supplementation in the culture system during IVG benefited the development of murine preantral follicles.

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.

Three-dimensional levitation culture improves in-vitro growth of secondary follicles in bovine model

RESEARCH QUESTION

Does a three-dimensional culture system based on magnetic levitation with nanoparticles assembly maintain the follicular structure and viability with adequate growth rates leading to oocyte maturation after long-term culture?

DESIGN

Randomized-controlled trial of treatments in a bovine model. Secondary follicles (n = 213) isolated from bovine ovaries were cultured in a two-dimensional system (two-dimensional control) or three-dimensional levitation system with different concentrations (three-dimensional 50 µl/ml, 100 µl/ml and 200 µl/ml) of magnetic nanoparticles. Follicular growth (diameter, daily growth and growth patterns), morphology (normal, degenerated and extruded follicles), antrum formation, oocyte viability and chromatin configuration were assessed.

RESULTS

Secondary follicles of three-dimensional 200-µl/ml treatment showed higher viability, antrum formation and lower degeneration rates than two-dimensional control. Also, follicles cultured in the three-dimensional 200-µl/ml treatment presented a most homogenous daily growth rate as shown by the lowest variance and standard deviation. Compared with the two-dimensional control, the proportion of non-growing and slow-growing follicles were 3.8-fold lower and 1.6-fold higher, respectively, in the three-dimensional 200-µl/ml treatment. After in-vitro maturation, the three-dimensional 200-µl/ml had a greater proportion of viable oocytes (1.7-fold) and meiotic resumption rates (2.4-fold) than the two-dimensional control treatment.

CONCLUSION

The three-dimensional levitation culture system improves the viability of in-vitro development of bovine secondary follicles, antrum formation and lower extrusion and degeneration rates and adequate growth rate leading to relevant oocyte viability and meiotic resumption after in-vitro maturation. This approach does not require a specific medium, and has the potential as an alternative method to in-vitro follicle culture in several species, including humans.

A Microfluidic Device for Culturing an Encapsulated Ovarian Follicle

Microfluidic chips have been proved effective in mimicking different organs of human body. Simulating human ovarian follicles by microfluidic device will be useful in exploring the mechanism of folliculogenesis and related diseases. In this paper, a microfluidic chip was designed to culture a single human pre-antral follicle. Ovarian follicles were first encapsulated in 3D calcium alginate hydrogel beads and then cultured on chip and in dish under same conditions. The diameters of cultured ovarian follicles were measured, and the same amount of medium was collected from microfluidic device or dish per two days for measuring the estradiol and androgen concentrations. The results confirmed the successful growth of ovarian follicles on chip with their hormonal trends and diameters increase, which were similar to ovarian follicles cultured in dish. It is concluded that this microfluidic chip can be used to culture a single human ovarian follicle, which provides a useful tool to explore the hormonal changes and their interactions during folliculogenesis.

Microfluidic Encapsulation of Ovarian Follicles for 3D Culture

The ovarian follicle that contains one single oocyte is the fundamental functional tissue unit of mammalian ovary. Therefore, isolation and in vitro culture of ovarian follicles to obtain fertilizable oocytes are regarded as a promising strategy for women to combat infertility. In this communication, we performed a brief survey of studies on microfluidic encapsulation of ovarian follicles in core-shell hydrogel microcapsules for biomimetic 3D culture. These studies highlighted that recapitulation of the mechanical heterogeneity of the extracellular matrix in ovary is crucial for in vitro culture to develop early pre-antral follicles to the antral stage, and for the release of cumulus-oocyte complex (COC) from antral follicles in vitro. The hydrogel encapsulation-based biomimetic culture system and the microfluidic technology may be invaluable to facilitate follicle culture as a viable option for restoring women's fertility in the clinic.

In vitro culture of ovarian follicles from Peromyscus

The ovarian follicle is the fundamental functional tissue unit of mammalian ovary. Each ovarian follicle contains one single oocyte. Isolation and in vitro culture of ovarian follicles to obtain fertilizable oocytes have been regarded as a promising strategy for women to combat infertility. The follicles from Peromyscus are considered as a better model than that from inbred mice for studying follicle culture. This is because Peromyscus mice are outbred (as with humans) with an increased life span. In this article, we reviewed studies on this subject conducted using Peromyscus follicles. These studies show that the conventional 2D micro-drop and 3D hanging-drop approaches established for in vitro culture of early preantral follicles from inbred mice are not directly applicable for cultivating the follicles from Peromyscus. However, the efficiency could be significantly improved by culturing multiple early preantral follicles in one hanging drop of Peromyscus ovarian cell-conditioned medium. It is further revealed that the mechanical heterogeneity in the extracellular matrix of ovary is crucial for developing early preantral follicles to the antral stage and for the subsequent ovulation to release cumulus-oocyte complex. These findings may provide valuable guidance for furthering the technology of in vitro follicle culture to restore fertility in the clinic.

A Biomimetic Core-Shell Platform for Miniaturized 3D Cell and Tissue Engineering

This article describes a biomimetic core-shell platform with a collagen-based core and an alginate hydrogel shell for cell and tissue culture. With this system, chemical and physical properties of extracellular matrix (ECM) in the core microenvironment can be controlled to regulate proliferation and development of cells/tissues under miniaturized three-dimensional (3D) culture.

The effects analysis of two neonicotinoid insecticides on in vitro maturation of porcine oocytes using hanging drop monoculture method

Acetamiprid (ACE) and imidacroprid (IMI) are known neonicotinoid insecticides with strong affinities for the insect-selective nicotinic acetylcholine receptor. These provide insect control by hyperstimulating insect nerves and are used for agricultural pest management. However, it has also been reported that ACE and IMI affect mammalian reproductive function. We determined the effects of ACE and IMI on the in vitro maturation of porcine oocytes. Significant decreases in nuclear maturation rates were observed in the ACE or IMI-exposed groups. Also, in matured oocytes from the ACE or IMI-exposed groups, irregular chromosomes were observed. Our results suggest that ACE and IMI exposure was detrimental to porcine oocytes and the extent of the effects depends on the concentration of exposure.

In Vitro Mouse Ovarian Follicle Growth and Maturation in Alginate Hydrogel: Current State of the Art

This review describes the main factors affecting the in vitro development of mouse ovarian follicles under conditions of three-dimensional alginate hydrogel system. The factors discussed include concentration of alginate hydrogel, presence of additives (collagen, fibrin) influencing substrate rigidity; culture conditions; composition of culture media; substances that act like antioxidants (salts of ascorbic acid, glutathione) and contribute to the improvement of lipid metabolism (L-carnitine), hormones and growth factors. The methods for follicle group cultivation in alginate hydrogel and cocultivation of different cell populations with follicles encapsulated in alginate hydrogel are covered in the present article.

Effect of single-oocyte culture system on in vitro maturation and developmental competence in mice

Purpose

To investigate whether single-culture systems influence the quality of in vitro-matured oocytes, we examined the maturation and developmental competence of oocytes obtained by grouped in vitro maturation (IVM) or single IVM.

Methods

In vitro-matured oocytes were obtained using the culture drop (CD) method for the grouped IVM experiments, and the CD and hanging drop (HD) method for the single IVM experiments. To evaluate oocyte developmental competence, we performed in vitro fertilization and culture, and counted the number of blastocysts. To evaluate the oocyte cytoplasmic maturation, we measured the maturation promoting factor (MPF) expression levels.

Results

Oocytes cultured singly had lower maturity and developmental competence than the grouped IVM oocytes. However, enhanced oocyte fertility and blastocyst quality was achieved by the HD single IVM method. Additionally, the MPF activity level increased in all culture methods, compared to the control; however, it lagged behind nuclear maturation.

Conclusions

These results suggest that the HD method is efficient for single IVM.

The crucial role of mechanical heterogeneity in regulating follicle development and ovulation with engineered ovarian microtissue

Contemporary systems for in vitro culture of ovarian follicles do not recapitulate the mechanical heterogeneity in mammalian ovary. Here we report microfluidic generation of biomimetic ovarian microtissue for miniaturized three-dimensional (3D) culture of early secondary preantral follicles by using alginate (harder) and collagen (softer) to fabricate the ovarian cortical and medullary tissues, respectively. This biomimetic configuration greatly facilitates follicle development to antral stage. Moreover, it enables in vitro ovulation of cumulus-oocyte complex (COC) from the antral follicles in the absence of luteinizing hormone (LH) and epidermal growth factor (EGF) that are well accepted to be responsible for ovulation in contemporary literature. These data reveal the crucial role of mechanical heterogeneity in the mammalian ovary in regulating follicle development and ovulation. The biomimetic ovarian microtissue and the microfluidic technology developed in this study are valuable for improving in vitro culture of follicles to preserve fertility and for understanding the mechanism of follicle development and ovulation to facilitate the search of cures to infertility due to ovarian disorders.