In vitro embryo production from early antral follicles of goats fed with a whole full-fat linseed based diet.

The present study aimed to use an in vitro follicle culture (IVFC) biotechnique as a tool to evaluate the influence of whole flaxseed as a feed supplementation in the diet on the in vitro development of caprine early antral follicles (EAFs) and further embryo production. In total, 18 adult goats were homogeneously allocated into two diet groups: Control and Flaxseed. EAFs from both experimental groups (300-400 µm) were isolated and cultured in vitro for 18 days. After IVFC, recovered cumulus-oocyte complexes were submitted to in vitro maturation, and subsequently to IVF and in vitro embryo culture. The endpoints evaluated were follicular growth and morphology, oocyte recovery rate and diameter, sperm penetration, pronuclei formation, embryo development, and estradiol production. The addition of the whole flaxseed in the diet did not affect (P > 0.05) follicular growth and diameter. A higher (P < 0.05) percentage of oocytes ≥ 110 µm was recovered from the flaxseed treatment. However, the sperm penetration rate was higher (P < 0.05) in the control treatment when compared with the flaxseed treatment, but no differences were found regarding the rate of fertilization nor cleaved embryos. In conclusion, dietary flaxseed increased the recovery rate of fully grown oocytes, but it did negatively affect the sperm penetration rate, even though there was no further effect on the cleavage rate.

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

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

Folliculogenesis-related genes are differently expressed in secondary and tertiary ovarian follicles.

The relative mRNA abundance of 10 genes associated with folliculogenesis was compared between late preantral (secondary) and early antral (tertiary) ovarian follicles in goats. In total, 100 follicles in each category were mechanically isolated. The relative transcript abundance of the mRNAs were determined by qPCR. Data were analyzed using unpaired Student's t-test. Of the 10 tested genes, ABLIM mRNA was not detected in either follicle category, six genes (SLIT3, TYMS, GTPBP1, AKR1C4, PIK3R6, and MAOB) were upregulated in secondary follicles compared with tertiary follicles, and three genes (ARHGEF12, CLEC6A, and CYTL1) showed similar mRNA abundances in both secondary and tertiary follicles. In conclusion, SLIT3, GTPBP1, AKR1C4, and PIK3R6 mRNA abundance was upregulated in secondary follicles (preantral phase) compared with in tertiary follicles (antral phase) in goats.

Harvesting, processing, and evaluation of in vitro-manipulated equine preantral follicles: A review.

The mammalian ovary is responsible for essential stages of folliculogenesis and hormonal production, regulating the female physiological functions during the menstrual/estrous cycles. The mare has been considered an attractive model for comparative studies due to the striking similarities shared with women regarding in vivo and in vitro folliculogenesis. The ovarian follicular population in horses contains a large number of oocytes enclosed in preantral follicles that are yet to be explored. Therefore, the in vitro manipulation of equine preantral follicles aims to avoid the process of atresia and promote the development of follicles with competent oocytes. In this regard, after ovarian tissue harvesting, the use of appropriate processing techniques, as well as suitable approaches to evaluating equine preantral follicles and ovarian tissue, are necessary. Although high-quality equine ovarian tissue can be obtained from several sources, some critical aspects, such as the age of the animals, ovarian cyclicity, reproductive phase, and the types of ovarian structures, should be considered. Therefore, this review will focus on providing an update on the most current advances concerning the critical factors able to influence equine preantral follicle quality and quantity. Also, the in vivo strategies used to harvest equine ovarian tissue, the approaches to manipulating ovarian tissue post-harvesting, the techniques for processing ovarian tissue, and the classical approaches used to evaluate preantral follicles will be discussed.

Supportive techniques to investigate in vitro culture and cryopreservation efficiencies of equine ovarian tissue: A review.

During the reproductive lifespan of a female, only a limited quantity of oocytes are naturally ovulated; therefore, the mammalian ovary possesses a substantial population of preantral follicles available to be handled and explored in vitro. Hence, the manipulation of preantral follicles enclosed in ovarian tissue aims to recover a considerable population of oocytes of high-value animals for potential application in profitable assisted reproductive technologies (ARTs). For this purpose, the technique of preantral follicle in vitro culture (IVC) has been the most common research tool, achieving extraordinary results with offspring production in the mouse model. Although promising outcomes have been generated in livestock animals after IVC of preantral follicles, the quantity and quality of embryo production with those oocytes are still poor. In recent years, the mare has become an additional model for IVC studies due to remarkable similarities with women and livestock animals regarding in vivo and in vitro ovarian folliculogenesis. For a successful IVC system, several factors should be carefully considered to provide an optimum culture environment able to support the viability and growth of preantral follicles enclosed in ovarian tissue. The cryopreservation of the ovarian tissue is another important in vitro manipulation technique that has been used to preserve the reproductive potential in humans and, in the future, may be used in highly valuable domestic animals or endangered species. Several improvements in cryopreservation protocols are necessary to support the utilization of ovarian tissue of different species in follow-up ARTs (e.g., ovarian fragment transplantation). This review aims to provide an update on the most current advances regarding supportive in vitro techniques used in equids to evaluate and manipulate preantral follicles and ovarian tissue, as well as methodological approaches used during IVC and cryopreservation techniques.

Anethole improves blastocysts rates together with antioxidant capacity when added during bovine embryo culture rather than in the in vitro maturation medium.

We performed the exposure of bovine oocytes to anethole during in vitro maturation (0 or 300 µg/ml), during in vitro embryo production (0, 30, 300 or 2000 µg/ml), or during both periods to determine the rates of 2-4 cells embryos, blastocysts rates and cells numbers, as well as the production of reactive oxygen species (ROS). Bovine ovaries (n = 240) were collected from a local abattoir after slaughter and cumulus-oocyte complexes (COCs) with homogeneous and non-dark cytoplasm, surrounded by two or more compact layers of cumulus cells, and an intact zona pellucida were selected for in vitro maturatuion (IVM). Mature oocytes were then submitted to in vitro fertilization (IVF) and in vitro embryo production (IVP) in culture medium supplemented or not with different concentrations of anethole, as described above. Although IVM medium supplementation with 300 µg/ml anethole improved the rates of bovine blastocysts formation, we demonstrated that IVP medium supplementation with 30 µg/ml anethole, regardless of IVM medium enrichment, considerably enhanced blastocysts rates. Furthermore, ROS levels were decreased only when anethole was added to the IVP medium without previous IVM medium supplementation.

Effect of cryopreservation techniques on proliferation and apoptosis of cultured equine ovarian tissue.

Preservation of cellular integrity and its mechanisms after ovarian tissue cryopreservation (OTC) and in vitro culture (IVC) procedures are crucial aspects for the success of preservation and recovery of female fertility. This study aimed to evaluate the effects of two cryopreservation methods (slow-freezing, SF, and vitrification, VIT) on the equine ovarian tissue after 1, 3, and 7 days of IVC by assessing: (i) preantral follicle morphology and distribution of follicle classes; (ii) protein expression of markers of cell proliferation for EGFR and Ki-67; (iii) markers of apoptosis for Bax and Bcl-2; and (iv) DNA fragmentation. Percentages of normal primordial follicles were similar (P > 0.05) among SF-control, VIT-control, and fresh control groups. After 7 days of culture, VIT-IVC7 had a greater (P < 0.05) total percentage of normal preantral follicles when compared with SF-IVC7, but both had a lower (P < 0.05) percentage than fresh IVC7 group. Prior to and after 7 days of culture, expression of EGFR and Ki-67 were similar (P > 0.05) among fresh, SF, and VIT groups. After 7 days of culture, VIT had higher (P < 0.05) Bax expression than the fresh and SF tissues, but Bcl-2 was similar (P > 0.05) among groups. Prior to IVC, TUNEL signals were similar (P > 0.05) among groups; however, VIT-IVC7 had greater (P < 0.05) TUNEL signals when compared with the fresh IVC7 group. In conclusion, findings demonstrated: (i) similar efficiency between SF and VIT compared with fresh control to preserve morphologically normal follicles; and (ii) similar tissue functionality and cell proliferation capability after equine OTC by either SF and VIT methods following IVC for 7 days. The results herein presented shed light on equine fertility preservation programs using OTC techniques.

Cryopreservation and in vitro culture of white-tailed deer ovarian tissue.

The aims of this study were to evaluate (1) the survivability of white-tailed deer ovarian tissue after cryopreservation by slow-freezing (SF) and vitrification (VIT) techniques and in vitro culture (IVC) for up to 7 days, and (2) the effects of cryopreservation techniques on protein expression of proliferative and apoptotic markers of ovarian tissue pre- and post-in vitro culture. Ovaries (n = 14) of seven white-tailed deer fawns (<1.5 years old) were used. Ovarian cortexes were cut into fragments (2 × 2 × 0.5 mm) and split into nine treatment groups: (1) fresh noncultured control, (2) fresh-IVC 1 day, (3) fresh-IVC 7 days, (4) SF noncultured, (5) SF-IVC 1 day, (6) SF-IVC 7 days, (7) VIT noncultured, (8) VIT-IVC 1 day, and (9) VIT-IVC 7 days. Preantral follicle morphology, class distribution, and density; stromal cell density; EGFR, Ki-67, Bax, and Bcl-2 protein expression; and DNA fragmentation were assessed. Results showed that: (i) white-tailed deer fresh ovarian tissue can be cultured for up to 7 days, preserving the tissue integrity and 50% of morphologically normal preantral follicles; (ii) cryopreservation of white-tailed deer ovarian tissue by either slow-freezing or vitrification does not disrupt markers of proliferation and apoptosis after thawing; (iii) ovarian fragments cryopreserved by the vitrification method had greater follicle viability during in vitro culture than the slow-freezing method; and (iv) fragments cryopreserved by slow-freezing suffered apoptosis earlier than those preserved by vitrification. The findings herein reported advance knowledge towards development of adequate cryopreservation protocols for long-term banking programs for Cervidae species.

Dose-dependent effects of frutalin on in vitro maturation and fertilization of pig oocytes.

The aim of the present study was to evaluate the effect of frutalin (FTL) on in vitro maturation (IVM), and fertilization (IVF) of pig oocytes. In the Experiment 1, cumulus-oocyte complexes (COCs) were submitted to IVM in maturation medium alone or supplemented with different FTL concentration (0.6, 6 and 60 µg/mL), or 0.3 µg/mL doxorubicin (DXR). After IVM, some oocytes were evaluated for chromatin configuration, and the remaining oocytes were submitted to in vitro fertilization. In Experiment 2, matured oocytes were fertilized in IVF medium alone (control) or in presence of different FTL concentration (0.6, 6 and 60 µg/mL), or 0.3 µg/mL DXR. After 18 h post fertilization, the endpoints penetration rate, monospermy, spermatozoa per oocyte, and the IVF efficiency were evaluated in both experiments. In Experiment 1, 6 and 60 µg/mL FTL, as well as DXR increased (P < 0.05) the rate of oocytes with abnormal chromatin configuration when compared to oocyte matured in control medium alone or supplemented with 0.6 µg/mL FTL. The percentage of meiotic resumption in oocytes cultured with 60 µg/mL FTL or DXR was less (P < 0.05) than in the other treatments. Moreover, oocytes matured with 6 or 60 µg/mL FTL and DXR had a lesser IVM efficiency when compared to those matured with 0.6 µg/mL FTL or in control medium. Additionally, there was a greater (P < 0.05) with culture in a medium containing 6 µg/mL FTL for the rate of partenogenetically activated oocytes when compared with the other treatments. Culturing of COCs during IVM in a medium containing 6 or 60 FTL resulted in a lesser (P < 0.05) sperm penetration and spermatozoa/oocyte rates when compared to other treatments, and IVF efficiency was less (P < 0.05) than that in control medium alone or with a medium containing 0.6 µg/mL FTL. In Experiment 2, culturing in a medium containing 0.6 µg/mL FTL resulted in greater (P < 0.05) monospermy and IVF efficiency rates when compared to culturing in the control medium. In addition, culturing in a medium with 6 and 60 µg/mL FTL resulted in a lesser (P < 0.05) spermatozoa penetration, sperm/oocyte rates and IVF efficiency, although there were greater (P < 0.05) monospermy rates. In conclusion, culturing in a medium containing 0.6 µg/mL FTL resulted in lesser spermatozoa penetration rates and number of spermatozoa/oocyte increasing the IVF efficiency without harmful effects. Use of a greater concentration of FTL in the medium has toxic effects during oocyte maturation and results in a reduced IVF efficiency.

Effects of FSH addition to an enriched medium containing insulin and EGF after long-term culture on functionality of equine ovarian biopsy tissue.

The effect of FSH supplementation on an enriched cultured medium containing insulin (10 ng/mL) and EGF (50 ng/mL) was investigated on in vitro culture of equine ovarian biopsy tissue. Ovarian tissue fragments were collected from mares (n = 10) and distributed in the following treatments: noncultured control, cultured control, and cultured + FSH. Both treated groups were cultured for 7 or 15 days. The end points evaluated were: follicular morphology, estradiol levels in the culture medium, fluorescence intensity for TUNEL, EGFR and Ki-67 detection, and gene expression of GDF-9, BMP-15, and Cyclin-D2 in the ovarian tissue. After seven days of culture, medium supplemented with FSH had a similar (P > 0.05) percentage of morphologically normal follicles compared to the noncultured control group. Estradiol levels increased (P < 0.05) from Day 7 to Day 15 of culture for both treated groups. No difference (P > 0.05) was observed for TUNEL and EGFR intensity between the noncultured control group and the treated groups after 15 days of culture. Ki-67 intensity did not differ (P > 0.05) between treated groups after 15 days of culture, but decreased (P < 0.05) when compared with the noncultured control group. Similar (P > 0.05) mRNA expression for GDF-9, BMP-15, and Cyclin-D2 was observed among all treatments after 15 days of culture. In conclusion, an enriched medium supplemented or not with FSH was able to maintain the functionality of equine ovarian biopsy tissue after a long-term in vitro culture.

Equine ovarian tissue viability after cryopreservation and in vitro culture.

Ovarian tissue cryopreservation allows the preservation of the female fertility potential for an undetermined period. The objectives of this study were to compare the efficiency of cryoprotective agents (CPAs; dimethyl sulfoxide, DMSO; ethylene glycol, EG; and propylene glycol, PROH) using slow-freezing and vitrification methods, and evaluate the viability of cryopreserved equine ovarian tissue after 7 days of culture. Fresh and cryopreserved ovarian fragments were evaluated for preantral follicle morphology, stromal cell density, EGFR, Ki-67, Bax, and Bcl-2 protein expression, and DNA fragmentation. Vitrification with EG had the highest rate of morphologically normal preantral follicles, while DMSO had the lowest (76.1 ± 6.1% and 40.9 ± 14.8%, respectively; P < 0.05). In slow-freezing, despite that DMSO had the highest percentage of morphologically normal follicles (77.7 ± 5.8%), no difference among the CPAs was observed. Fluorescence intensity of EGFR and Ki-67 was greater when vitrification with EG was used. Regardless of the cryopreservation treatment, DMSO had the highest (P < 0.05) Bax/Bcl-2 ratio; however, DNA fragmentation was similar (P > 0.05) among treatments after thawing. After in vitro culture, the percentage of normal follicles was similar (P > 0.05) between slow-freezing and vitrification methods; however, vitrification had greater (P < 0.05) stromal cell density than slow-freezing. In summary, equine ovarian tissue was successfully cryopreserved, increasing the viability of the cells in the ovarian tissue after thawing when using DMSO and EG for slow-freezing and vitrification methods, respectively. Therefore, these results are relevant for fertility preservation programs.

Role of EGF on in situ culture of equine preantral follicles and metabolomics profile.

The effects of epidermal growth factor (EGF) concentrations (0, 10, 50, and 100ng/ml) on in vitro culture (IVC) of equine preantral follicles were evaluated using histology, estradiol and reactive oxygen species (ROS) production and metabolomics. After IVC, the percentage of normal follicles was lower (P<0.05) for all treatments when compared to non-cultured control. EGF 50ng/ml treatment had more (P<0.05) normal follicles at Day 7 of culture when compared with EGF 0 and 100ng/ml. EGF 50ng/ml had more (P<0.05) developing follicles than the 0ng/ml and 10ng/ml EGF treatments. Follicular and oocyte diameters were greater (P<0.05) with EGF 50ng/ml than the other cultured treatments, but similar (P>0.05) to the non-cultured control. From Day 1 to Day 7 estradiol production increased (P<0.05) in all EGF treatments. EGF 50ng/ml was the only treatment that maintained ROS production through IVC. Metabolomics profiles of the spent media indicated that eleven ions from variable influence in the projection (VIP) scores were higher represented in the EGF 50ng/ml treatment. In conclusion, EGF 50ng/ml treatment maintained follicle survival and ROS production, and promoted activation of cultured equine preantral follicles enclosed in ovarian tissue.

In vitro growth and maturation of isolated caprine preantral follicles: Influence of insulin and FSH concentration, culture dish, coculture, and oocyte size on meiotic resumption.

The aims of this study were: (1) to evaluate the effect of different insulin concentrations, alone or in combination with either a fixed FSH concentration or increasing FSH concentrations on the in vitro culture of isolated caprine preantral follicles and (2) to analyze the efficiency of two IVM media and maturation culture systems (with or without coculture with in vivo grown oocytes) on the meiosis resumption. Secondary follicles were cultured for 18 days in a basic medium supplemented with low- or high-insulin concentration alone or with a fixed FSH concentration or with increasing FSH concentrations. Oocytes grown in vivo or in vitro were matured alone or cocultured. The high-insulin concentration associated with fixed FSH treatment had higher meiotic resumption rate (P < 0.05) and was the only treatment capable of producing oocytes in metaphase II. The rates of germinal vesicle, germinal vesicle breakdown, metaphase I, metaphase II (MII), meiotic resumption, and oocyte diameter were similar between the maturation media. In conclusion, a basic medium supplemented with 10-µg/mL insulin and 100-µg/mL FSH throughout the culture period improved meiotic resumption rate and produced MII oocytes from caprine preantral follicles cultured in vitro. The MII rate was similar between in vivo and in vitro grown oocytes ≥110 µm.

Caprine ovarian follicle requirements differ between preantral and early antral stages after IVC in medium supplemented with GH and VEGF alone or in combination.

The aim of the present study was to evaluate the effect of growth hormone (GH) and vascular endothelial growth factor (VEGF) added alone, sequentially or in combination, in the presence of insulin at physiological concentration (10 ng/mL) on the IVC of two different follicular categories: preantral (experiment 1; Exp.1) and early antral (experiment 2; Exp.2). Isolated follicles were individually cultured for 24 (Exp.1) and 18 days (Exp.2) in the following treatments: αMEM+ (Control), or Control medium supplemented with 50 ng/mL GH (GH), 100 ng/mL VEGF (VEGF), the combination of both (GH + VEGF), GH during the first 12 days and VEGF from Day 12 until the end of the culture (GH/VEGF) and vice versa (VEGF/GH). At the end of the culture, cumulus-oocyte complexes from in vitro-grown follicles were recovered and subjected to IVM. The following end points were evaluated: Follicle morphology, growth rates and antrum formation, production of estradiol, progesterone and testosterone, oocyte viability and meiotic stage, as well as relative expression of LHR, Amh, HAS2, PTGS2, CYP17, CYP19A1, and 3ßHSD. A considerable amount of viable fully grown oocytes were recovered after the IVC of early antral follicles in all treatments. Nevertheless, the GH treatment presented the highest percentage of fully grown oocytes (60%), mean oocyte diameter (117.74 ± 2.61 µm), and meiotic resumption (50%). Furthermore, GH treatment produced higher (P < 0.05) rates of metaphase II oocytes than all the other treatments, and similar LHR, Amh, and PTGS2 transcript levels to in vivo. Contrary to early antral follicles, preantral follicles were not affected by medium supplementation. In conclusion, the addition of GH to a culture medium containing physiological concentrations of insulin improves oocyte growth and maturation after the IVC of goat early antral follicles.

FSH supplementation to culture medium is beneficial for activation and survival of preantral follicles enclosed in equine ovarian tissue.

This study investigated the effect of adding different concentrations of bovine recombinant follicle-stimulating hormone on the IVC of equine preantral follicles enclosed in ovarian tissue fragments. Randomized ovarian fragments were fixed immediately (fresh noncultured control) or cultured for 1 or 7 days in α-MEM(+) supplemented with 0, 10, 50, and 100 ng/mL FSH and subsequently analyzed by classical histology. Culture media collected on Day 1 or Day 7 and were analyzed for steroids (estradiol and progesterone) and reactive oxygen species (ROS). After Day 1 and Day 7 of culture, 50-ng/mL FSH treatment had a greater (P < 0.05) percentage of morphologically normal follicles when compared to the other groups, except the 10-ng/mL FSH treatment at Day 1 of culture. The percentage of developing follicles (transition, primary, and secondary), and follicular and oocyte diameters were higher (P < 0.05) in the 50-ng/mL FSH treatment compared to the other groups after Day 7 of culture. Furthermore, estradiol secretion and ROS production were maintained (P > 0.05) throughout the culture in the 50-ng/mL FSH treatment. In conclusion, the addition of 50 ng/mL of FSH promoted activation of primordial follicles to developing follicles, improved survival of preantral follicles, and maintained estradiol and ROS production of equine ovarian tissue after 7 days of culture.

Insulin improves in vitro survival of equine preantral follicles enclosed in ovarian tissue and reduces reactive oxygen species production after culture.

This study investigated the effect of insulin concentration on the in vitro culture of equine preantral follicles enclosed in ovarian tissue. Ovarian tissue samples were immediately fixed (noncultured control) or cultured for 1 or 7 days in α-MEM(+) supplemented with 0 ng/mL, 10 ng/mL, or 10 µg/mL insulin. Ovarian tissues were processed and analyzed by classical histology. Culture medium samples were collected after 1 and 7 days of culture for steroid and reactive oxygen species (ROS) analyses. The percentage of morphologically normal follicles was greater (P < 0.001) in insulin-treated groups after 1 day of culture; likewise, more (P < 0.02) normal follicles were observed after 7 days of culture in medium supplemented with 10-ng/mL insulin. Furthermore, an increase (P < 0.01) in developing (transition, primary, and secondary) follicles between Days 1 and 7 of culture was observed only with the 10-ng/mL insulin treatment. ROS production after 1 or 7 days of culture was lower (P < 0.0001) in medium with 10-ng/mL insulin than the other treatments. Ovarian tissues containing preantral follicles were able to produce estradiol and progesterone after 1 and 7 days of culture; however, treatments did not differ in steroid production. In conclusion, the use of a physiological concentration (10 ng/mL) of insulin rather than the previously reported concentration (10 µg/mL) for in vitro culture of equine preantral follicles improved follicular survival and growth and lowered oxidative stress. Results from this study shed light on new perspectives for producing an appropriate medium to improve equine preantral follicle in vitro survival and growth.