In vitro growth of mouse preantral follicles: effect of animal age and stem cell factor/insulin-like growth factor supplementation

In vitro growth (IVG) of human ovarian follicles in frozen thawed ovarian cortex tissue culture supplemented with follicular fluid under hypoxic conditions

Background

Despite its clinical success rates, transplantation after ovarian tissue cryopreservation (OTC) remains a matter of concern. Certain cancer subtypes may lead to the transfer of malignant cells when transplantation of affected ovarian tissue is conducted. IVG and subsequent isolation of vital follicles obtained from frozen thawed ovarian tissue for further in vitro maturation (IVM) would expand current fertility protection techniques while reducing the risk of retransplanting malignant cells.

Methods

A total of 216 cortical biopsies from 3 patients were included in this study in 4 treatment groups. After freezing, thawing and 8 days of hypoxic tissue culture supplemented with different concentrations of human follicular fluid (HuFF) and follicle-stimulating hormone (FSH), follicles were isolated enzymatically and stained with calcein to determine follicular viability. Numbers and size of vital follicles were assessed by fluorescence microscopy (Ti2, Nikon) and specified by computer assisted, semi-automated measurement (NIS software, Nikon). To estimate the effect of in vitro culture on apoptosis, tissue sections were stained for nicked DNA (TUNEL) prior and after tissue culture.

Results

Analysing 3025 vital follicles, we observed significant differences [P < 0.01] regarding follicle size when hypoxic tissue culture was supplemented with HuFF compared with the control group on day 1, individual follicles reached sizes > 100 µm.

Conclusions

The results implicate that HuFF contains valuable factors contributing to significant IVG of follicles in human ovarian tissue and could be regarded as an additional tool in personalized fertility restoration prior to retransplantation of ovarian tissue.

Figla promotes secondary follicle growth in mature mice

The in vitro growth (IVG) of human follicles is a potential fertility option for women for whom cryopreserved ovarian tissues cannot be transplanted due to the risk of cancer cell reintroduction; however, there is currently no established method. Furthermore, optimal IVG conditions may differ between the follicles of adult and pre-pubertal females due to molecular differences suggested by basic research. To systematically identify differences between the secondary follicles of adult and pre-pubertal females, a comparative transcriptomic study using mice was conducted herein. Among differentially expressed genes (DEGs), Figla was up-regulated in mature mice. We successfully down-regulated Figla expression in secondary follicle oocytes by a Figla siRNA microinjection, and the subsequent IVG of follicles showed that the diameter of these follicles was smaller than those of controls in mature mice, whereas no significant difference was observed in premature mice. The canonical pathways of DEGs between control and Figla-reduced secondary follicles suggest that Figla up-regulates VDR/RXR activation and down-regulates stem cell pluripotency as well as estrogen signaling. We demonstrated for the first time that folliculogenesis of the secondary follicles of premature and mature mice may be regulated by different factors, such as Figla with its possible target genes, providing insights into optimal IVG conditions for adult and pre-pubertal females, respectively.

Effects of stem cell factor on in vitro growth of buffalo oocytes

Stem cell factor (SCF) plays important roles in primordial follicle activation, oocyte growth and survival, granulosa cell proliferation, theca cell recruitment, and ovarian steroidogenesis. The aim of this study was to investigate the effect of SCF on in vitro growth of buffalo oocytes. Oocyte-granulosa cell complexes (OGCs) were dissected from early antral follicles of slaughtered buffalo ovaries and cultured for 6 days in media supplemented with 0, 50 or 100 ng/mL SCF. In vitro grown oocytes were further cultured for in vitro maturation for 24 h. The results showed that SCF significantly (P < 0.05) increased oocyte diameter in vitro. The percentages of surviving oocytes were 60, 81 and 92 in 0, 50 and 100 ng/mL SCF supplemented group, respectively. SCF promoted formation of antrum-like structures in culture. The results also showed that SCF enhanced the maturation of in vitro grown buffalo oocytes. Here, 14% in vitro grown oocytes reached metaphase II (MII) stage in 50 ng/mL SCF supplemented group, whereas the percentage was increased to 26% in 100 ng/mL SCF treated group. These results show that SCF supports the growth, viability and nuclear maturation of buffalo oocytes in vitro.

Effects of Supplementation of Human Endometriotic Fluids on In Vitro Mouse Preantral Follicle Culture

This study aimed to investigate the potential detrimental effect of human endometriotic fluids (EFs) on in vitro growth of mouse preantral follicles. Preantral follicles (isolated from ovaries of 7- to 8-week-old mice) were cultured in growth medium for 10 days and then in maturation medium for 2 days. During in vitro culture, EF supernatants (0%, 2.5%, 5%, and 10%) were supplemented. Meiotic spindle integrity of metaphase II (MII) oocytes was analyzed. Hormone (17β-estradiol and anti-Müllerian hormone [AMH]) levels in the final spent media were measured by enzyme-linked immunosorbent assay. The survival rates of follicles at day 10 were significantly lower in 3 EF-supplemented groups (56.1%, 30.6%, and 6.2%; 83.6% in the nonsupplemented group). The production of total oocytes per initiated follicle was also significantly lower in the 3 EF-supplemented groups (34.7%, 18.4%, and 4.1%; 68.1% in the nonsupplemented group). Proportions of the oocyte with normal spindles were significantly lower in the 3 EF-supplemented groups (10%, 0% and 0%; 52% in the nonsupplemented group). In the final spent media, the level of 17β-estradiol was significantly lower only in the 10% EF-supplemented group, and the level of AMH was significantly lower in all 3 EF-supplemented groups, when compared with the nonsupplemented group. During in vitro culture of mouse preantral follicles, the survival rate, oocyte acquisition, spindle integrity of MII oocytes, and AMH production were greatly affected by EF supplementation. These findings suggest a possibility of detrimental effects of endometriotic cysts on folliculogenesis in adjacent ovarian tissues.

Physiologic Course of Female Reproductive Function: A Molecular Look into the Prologue of Life

The genetic, endocrine, and metabolic mechanisms underlying female reproduction are numerous and sophisticated, displaying complex functional evolution throughout a woman's lifetime. This vital course may be systematized in three subsequent stages: prenatal development of ovaries and germ cells up until in utero arrest of follicular growth and the ensuing interim suspension of gonadal function; onset of reproductive maturity through puberty, with reinitiation of both gonadal and adrenal activity; and adult functionality of the ovarian cycle which permits ovulation, a key event in female fertility, and dictates concurrent modifications in the endometrium and other ovarian hormone-sensitive tissues. Indeed, the ultimate goal of this physiologic progression is to achieve ovulation and offer an adequate environment for the installation of gestation, the consummation of female fertility. Strict regulation of these processes is important, as disruptions at any point in this evolution may equate a myriad of endocrine-metabolic disturbances for women and adverse consequences on offspring both during pregnancy and postpartum. This review offers a summary of pivotal aspects concerning the physiologic course of female reproductive function.

The base medium affects ultrastructure and survival of bovine preantral follicles cultured in vitro

The aim of this study was to determine the effectiveness of minimum essential medium alpha modification (α-MEM), tissue culture medium 199 (TCM-199), and McCoy's medium (McCoy's) on IVC of preantral follicles included in the bovine ovarian cortex (in situ). Bovine ovarian fragments were cultured in α-MEM, TCM-199, or McCoy supplemented ((+)) with glutamine, insulin, transferrin, selenium, ascorbic acid, BSA, penicillin, streptomycin, and HEPES buffer in 24-well plates, at 37 °C and 5% CO2 for 1 or 7 days. The morphology of follicles, normal, primordial and development (primary and secondary), as well as viability and morphometric variables of follicles and oocytes were assessed. The morphology and morphometry of preantral follicles were analyzed by ANOVA followed by the Tukey and Dunnett tests, and viability variables were determined by the chi-square test. The results showed that TCM-199(+) reduced significantly (P < 0.05) the percentage of morphologically normal and viable follicles after 7 days of culture compared to the control. Similar results were observed in McCoy(+), in which the percentage of viable follicles after 7 days of culture was significantly lower (P < 0.05) than in the control. However, it was similar (P > 0.05) between α-MEM(+) and TCM-199(+). Moreover, follicular diameters in McCoy(+) and TCM-199(+) were significantly smaller (P < 0.05) than in control and α-MEM(+) after 7 days of culture. In addition, the ultrastructure of preantral follicles was similar between the control and α-MEM(+) after 7 days of culture. In conclusion, α-MEM(+) showed to be the most effective medium to preserve morphology, morphometry and ultrastructure of bovine preantral follicles, ensuring their viability and growth after in situ culture.