In vitro culture of buffalo (Bubalus bubalis) preantral follicles

Current status of assisted reproductive technologies in buffaloes

Buffaloes are raised by small farm holders primarily as source of draft power owing to its resistance to hot climate, disease, and stress conditions. Over the years, transformation of these animals from draft to dairy was deliberately carried out through genetic improvement program leading to the development of buffalo-based enterprises. Buffalo production is now getting more attention and interest from buffalo raisers due to its socioeconomic impact as well as its contribution to propelling the livestock industry in many developing countries. Reproduction of buffaloes, however, is confronted with huge challenge and concern as being generally less efficient to reproduce compared with cattle due to both intrinsic and extrinsic factors such as poor estrus manifestation, silent heat, marked seasonal infertility, postpartum anestrus, long calving interval, delayed puberty, inherently low number of primordial follicles in their ovaries, high incidence of atresia, and apoptosis. Assisted reproductive technologies (ARTs) are major interventions for the efficient utilization of follicle reserve in buffaloes. The present review focuses on estrus and ovulation synchronization for fixed time artificial insemination, in vitro embryo production, intracytoplasmic sperm injection, cryopreservation of oocytes and embryos, somatic cell nuclear transfer, the factors affecting utilization in various ARTs, and future perspectives in buffaloes.

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.

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.

Basic fibroblast growth factor promotes prehierarchical follicle growth and yolk deposition in the chicken

Basic fibroblast growth factor (bFGF) plays a pivotal role in prompting ovarian follicular development and angiogenesis as well as inhibiting atresia. In the chicken, high laying performance depends largely on efficient healthy development of ovarian follicles. Moreover, rapid growth of oocytes resulted from abundant yolk deposition via blood circulation and intra-ovarian interactions among somatic and germ cells. The major components of yolk mass consist of very low density lipoprotein (VLDL) and vitellogenin that are taken up by maturing oocytes via VLDL receptor (VLDLR)-mediated endocytosis from blood capillaries in the theca layer and gaps between granulosa cells. Here we used immunofluorescence, BrdU, TUNEL, Western bolt and RT-qPCR methods to investigate effects of bFGF on growth and yolk deposition of chicken prehierarchical follicles. Results showed that VLDLR was mainly expressed in the granulosa cells of the prehierarchical and preovulatory follicles, and its expression declined with follicle growth. Moreover, bFGF caused a dose-dependent promoting effect on growth of small white follicles and this effect was inhibited by SU5402 (an FGFR1 antagonist). Proliferation of follicular theca externa cells was accelerated by bFGF via FGFR1-AKT signaling, coupled with augmented angiogenesis and up-regulated p-ERK expression in granulosa cells. After combined inhibition of FGFR1 and PPARγ, we found that PPARγ could also suppress VLDLR expression in granulosa cells. These results indicate that bFGF facilitated growth and yolk deposition in chicken prehierarchical follicles through promoting proliferation and angiogenesis in theca layers, and also through down-regulating VLDLR expression in granulosa cells.

Effect of anti-apoptotic drug Z-VAD-FMK on in vitro viability of dog follicles

It is recognized that ovarian follicular atresia is associated with apoptosis, and the most important effector of cell death is caspase-3. The aim of this study was to investigate the influence of anti-apoptotic drug Z-VAD-FMK on in vitro follicle growth in the domestic dog. Ovaries were obtained from peri-pubertal and adult domestic dogs, and cortical fragments recovered and incubated on 1.5% (w/v) agarose gel blocks within a 24-well culture plate containing Minimum Essential Medium Eagle-Alpha Modification (αMEM) supplemented with 4.2 μg/mL insulin, 3.8 μg/mL transferrin, 5 ng/mL selenium, 2 mM L-glutamine, 100 μg/mL of penicillin G sodium, 100 μg/mL of streptomycin sulfate, 0.05 mM ascorbic acid, 10 ng/mL of FSH and 0.1% (w/v) polyvinyl alcohol in humidified atmosphere of 5% CO₂ and 5% O₂. The cortices were randomly allocated in six treatments: 1) 10 ng/mL EGF (EGF V0); 2) 10 ng/mL of EGF plus 1 mM Z-VAD-FMK (EGF V1); 3) 10 ng/mL of EGF and 10 mM Z-VAD-FMK (EGF V10); 4) 1 mM Z-VAD-FMK; 5) 10 mM Z-VAD-FMK and (6) no EGF and Z-VAD-FMK supplementation (Control). The cortices were processed for histology and assessed for viability (based on morphology), density of structurally normal follicles, and diameter immediately after collection (non-culture Control) or after 3 or 7 days of in vitro incubation. Evaluation of mRNA expression of Cas3 in fresh cortices and those incubated for 3 days was performed using real-time PCR. Histological analysis revealed that in vitro incubation decreased (P < 0.05) follicle viability and density compared to the fresh, non-culture control. Addition of 10 μM of Z-VAD-FMK alone to the culture medium sustained follicle viability at Day 3, but did not impact follicle diameter when compared to the other treatment groups (p < 0.001); however, the beneficial benefit of this anti-apoptotic drug diminished after 7 days of incubation. Furthermore, Z-VAD-FMK supplementation did not impact Cas3 expression. The findings demonstrated that dog ovarian tissues are highly susceptible to in vitro incubation and Z-VAD-FMK supported short-term survival of dog follicles enclosed within the ovarian cortex.

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 Chorionic Gonadotropin Modulates the Expression of Genes Related to the Structure and Function of the Bovine Corpus Luteum

We hypothesized that stimulatory and superovulatory treatments, using equine chorionic gonadotropin (eCG), modulate the expression of genes related to insulin, cellular modelling and angiogenesis signaling pathways in the bovine corpus luteum (CL). Therefore, we investigated: 1—the effect of these treatments on circulating insulin and somatomedin C concentrations and on gene and protein expression of INSR, IGF1 and IGFR1, as well as other insulin signaling molecules; 2—the effects of eCG on gene and protein expression of INSR, IGF1, GLUT4 and NFKB1A in bovine luteal cells; and 3—the effect of stimulatory and superovulatory treatments on gene and protein expression of ANG, ANGPT1, NOS2, ADM, PRSS2, MMP9 and PLAU. Serum insulin did not differ among groups (P = 0.96). However, serum somatomedin C levels were higher in both stimulated and superovulated groups compared to the control (P = 0.01). In stimulated cows, lower expression of INSR mRNA and higher expression of NFKB1A mRNA and IGF1 protein were observed. In superovulated cows, lower INSR mRNA expression, but higher INSR protein expression and higher IGF1, IGFR1 and NFKB1A gene and protein expression were observed. Expression of angiogenesis and cellular modelling pathway-related factors were as follows: ANGPT1 and PLAU protein expression were higher and MMP9 gene and protein expression were lower in stimulated animals. In superovulated cows, ANGPT1 mRNA expression was higher and ANG mRNA expression was lower. PRSS2 gene and protein expression were lower in both stimulated and superovulated animals related to the control. In vitro, eCG stimulated luteal cells P4 production as well as INSR and GLUT4 protein expression. In summary, our results suggest that superovulatory treatment induced ovarian proliferative changes accompanied by increased expression of genes providing the CL more energy substrate, whereas stimulatory treatment increased lipogenic activity, angiogenesis and plasticity of the extracellular matrix (ECM).

Ovarian follicle development in vitro and oocyte competence: advances and challenges for farm animals

During the last 2 decades, research on in vitro preantral follicle growth and oocyte maturation has delivered fascinating advances concerning the knowledge of processes regulating follicle growth and the developmental competence of oocytes. These advances include (1) information about the role of several hormones and growth factors on in vitro activation of primordial follicles; (2) increased understanding of the intracellular pathway involved in the initiation of primordial follicle growth; (3) the growth of primary and secondary follicles up to antral stages; and (4) production of embryos from oocytes from in vitro grown preantral follicles. This review article describes these advances, especially in regard farm animals, and discusses the reasons that limit embryo production from oocytes derived from preantral follicles cultured in vitro.

High insulin concentrations promote the in vitro growth and viability of canine preantral follicles

To determine whether the effects of different concentrations of insulin on the development of canine preantral follicles in vitro were associated or not with FSH, secondary follicles were isolated and cultured. In Experiment 1, follicles were cultured in the following media: modified minimum essential medium (CtrlMEM) alone; CtrlMEM plus 5 ng mL⁻¹ insulin (Ins5ng); CtrlMEM plus 10 ng mL⁻¹ insulin (Ins10ng); and CtrlMEM plus 10 μg mL⁻¹ insulin. In Experiment 2, follicles were cultured in the same media but in the presence of sequential FSH (i.e. CtrlFSH, Ins5ngF, Ins10ngF and 10μgF, respectively). Increasing concentrations of FSH (100, 500 and 1000 ng mL⁻¹) were added sequentially to the culture medium on Days 0, 6 and 12 of culture. Viability were assessed at the end of culture and follicular diameter and the antrum formation rate at four time points (Days 0, 6, 12 and 18). In Experiment 1, the high insulin concentration significantly increased follicular viability (P<0.05). In contrast, in Experiment 2, viability was not affected by the inclusion of insulin. In addition, viability was significantly better in follicles cultured in CtrlFSH (P<0.05). The diameter of follicles in the high-insulin group in Experiment 1 and high-insulin plus FSH group in Experiment 2 was superior to other groups tested. In experiment 2, the Ins10μg and Ins10μgF groups exhibited significantly higher antrum formation rates than the other groups. In conclusion, in the absence of FSH, high concentrations of insulin have beneficial effects on follicular viability. However, to promote the growth of canine preantral follicles in vitro, it is recommended that a combination of insulin and FSH be added to the medium.

Short-term culture of ovarian cortical strips from capuchin monkeys (Sapajus apella): a morphological, viability, and molecular study of preantral follicular development in vitro

The aim of this study was to evaluate whether an in vitro culture (IVC) medium containing either or not β-mercaptoethanol (BME), bone morphogenetic protein 4 (BMP4), or pregnant mare serum gonadotrophin (PMSG) could be able to promote the development of capuchin monkeys' preantral follicles enclosed in ovarian cortical strips. Follicular viability after IVC was similar to control (89.32%). Primordial follicle recruitment to primary stage was not reached with IVC, but the rate of secondary follicle formation was increased in the medium supplemented with BME, BMP4, and PMSG (44.86%) when compared to IVC control (9.20%). In the medium supplemented with BME, BMP4, and PMSG, contrary to other media, anti-müllerian hormone-messenger RNA (mRNA) expression in ovarian tissue was upregulated (3.4-fold), while that of growth differentiation factor-9 was maintained. The BMP4-mRNA expression, however, appeared downregulated in all cultured tissues. Our findings show a favorable effect of BME, BMP4, and PMSG on the in vitro development of secondary follicles from capuchin monkeys.

Isolation and culture of preantral follicles for retrieving oocytes for the embryo production: present status in domestic animals

The development of efficient ovarian preantral follicle (PF) isolation and culture systems provide a large number of oocytes for the manipulation and embryo production. It also helps for understanding the mechanisms of follicle and oocyte development. Isolation and culture protocols for PFs were developed for many domestic species like cattle, buffalo, sheep, goat, pig, horse, camel, dog and cats; however, embryo production from oocytes derived from in vitro grown PFs was reported only in pigs, buffalo, sheep and goat. The rate of oocyte maturation from PFs grown in vitro is low and requires considerable research. This paper presents an overview of isolation and culture systems of PFs that have been developed for domestic species (cattle, buffalo, sheep, goat, pigs, horse, camel, dog and cat) along with the current status of progress achieved in the direction of producing embryos using PFs as the source of oocyte in these species.

Ultrastructure of isolated mouse ovarian follicles cultured in vitro

BACKGROUND

In vitro maturation of ovarian follicles, in combination with cryopreservation, might be a valuable method for preserving and/or restoring fertility in mammals with impaired reproductive function. Several culture systems capable of sustaining mammalian follicle growth in vitro have been developed and many studies exist on factors influencing the development of in vitro grown oocytes. However, a very few reports concern the ultrastructural morphology of in vitro grown follicles.

METHODS

The present study was designed to evaluate, by transmission and scanning electron microscopy, the ultrastructural features of isolated mouse preantral follicles cultured in vitro for 6 days in a standard medium containing fetal calf serum (FCS). The culture was supplemented or not with FSH.

RESULTS

The follicles cultured in FCS alone, without FSH supplementation (FCS follicles), did not form the antral cavity. They displayed low differentiation (juxta-nuclear aggregates of organelles in the ooplasm, a variable amount of microvilli on the oolemma, numerous granulosa cell-oolemma contacts, signs of degeneration in granulosa cell compartment). Eighty (80)% of FSH-treated follicles formed the antral cavity (FSH antral follicles). These follicles showed various ultrastructural markers of maturity (spreading of organelles in ooplasm, abundant microvilli on the oolemma, scarce granulosa cell-oolemma contacts, granulosa cell proliferation). Areas of detachment of the innermost granulosa cell layer from the oocyte were also found, along with a diffuse granulosa cell loosening compatible with the antral formation. Theca cells showed an immature morphology for the stage reached. Twenty (20)% of FSH-treated follicles did not develop the antral cavity (FSH non-antral follicles) and displayed morphological differentiation features intermediate between those shown by FCS and FSH antral follicles (spreading of organelles in the ooplasm, variable amount of microvilli, scattered granulosa cell-oolemma contacts, signs of degeneration in granulosa cell compartment).

CONCLUSIONS

It is concluded that FSH supports the in vitro growth of follicles, but the presence of a diffuse structural granulosa cell-oocyte uncoupling and the absence of theca development unveil the incomplete efficiency of the system. The present study contributes to explain, from a morphological point of view, the effects of culture conditions on the development of mouse in vitro grown follicles and to highlight the necessity of maintaining efficient intercellular communications to obtain large numbers of fully-grown mature germ cells.

Follicular interactions affect the in vitro development of isolated goat preantral follicles

The aim of this study was to evaluate the influence of the number of follicles per drop (one or three) and antral follicles on in vitro development of isolated goat preantral follicles. Preantral follicles were isolated through microdissection and distributed individually (control) or in groups of three follicles (treatment) in microdroplets of α-MEM with or without 1000 ng/ml follicle stimulating hormone (FSH) for Experiments 1 and 2, respectively. Experiment 3 was divided into four treatments according to the presence of one or three preantral follicles, associated or not with antral follicles. After culture, oocytes were retrieved from morphologically normal follicles and submitted to in vitro maturation (IVM) and live/dead fluorescent labelling. Results of Experiment 1 (basic medium without FSH) showed that culture of preantral follicles in groups enhances viability, growth and antrum formation after 12 days. However, in the presence of FSH (Experiment 2), only the recovery rate of fully grown oocytes for IVM was significantly affected by grouping of follicles. In Experiment 3, in general, co-culture of preantral follicles with an early antral follicle had a detrimental effect on viability, antrum formation and production of oocytes for IVM. In conclusion, the performance of in vitro culture of goat preantral follicles is affected by the number of follicles per drop, the presence of an antral follicle and FSH.

Moment of addition of LH to the culture medium improves in vitro survival and development of secondary goat pre-antral follicles

The present study investigated the effects of time of addition of luteinizing hormone (LH) to culture medium on the in vitro development of caprine pre-antral follicles. Pre-antral follicles (≥ 150 μm) were isolated from fragments of the goat ovarian cortex and individually cultured for 18 days in the absence (control) or presence of 100 ng/ml LH, added on days 0, 6 or 12 of culture. Follicular development was assessed based on antral cavity formation, increased follicular diameter as well as follicular and fully grown oocyte (>110 μm) viability. The results showed that after 18 days of culture, the percentage of surviving follicles in the control treatment was significantly lower when compared to other treatments (p < 0.05). There were no significant differences in antrum formation, follicular diameter and oocyte viability. The addition of LH at D6 of culture significantly increased the rates of oocytes ≥ 110 μm and the resumption of meiosis (p < 0.05). In contrast, when LH was added at the onset of culture, only germinal vesicle oocytes were obtained. In conclusion, the moment of addition of LH to the culture medium affects the performance of in vitro culture of caprine pre-antral follicles. The addition of LH to the medium from day 6 of culture onward improved the rates of follicular survival, as well as the ability of oocytes to resume meiosis. However, prolonged exposure to LH (addition at the onset of culture onward) showed detrimental effects for the meiotic resumption.

In vitro survival and development of goat preantral follicles in two different oxygen tensions

The aim of the present study was to evaluate the effect of two different oxygen (O(2)) concentrations on survival and development of preantral follicles of goats cultured in vitro. Preantral ovarian follicles (> or =150 microm) were isolated from ovarian cortex fragments of goats and individually cultured for 30 days under two different O(2) concentrations (5% and 20% O(2)). Follicle development was evaluated on the basis of antral cavity formation, increase in follicular diameter, presence of healthy cumulus oocyte complexes and fully grown oocytes. Results showed with progression of culture period from 6 to 12 days, a decrease in follicular survival was observed in both O(2) concentrations (P<0.05). When the O(2) tensions were compared to each other in the different days of culture, 20% O(2) was more efficient in promoting an increase in follicular diameter from day 24 of culture onward than 5% O(2) (P<0.05). However, follicles cultured with 5% O(2) had an increased percentage of antrum formation from 12 days to the end of culture, compared with 20% O(2) (P<0.05). Moreover, there was no difference in percentage of fully developed oocytes with the different O(2) tensions. However, only oocytes (16.7%) from follicles cultured in 20% O(2) resumed meiosis. In conclusion, concentration of 20% O(2) was more efficient in promoting follicular growth and oocyte meiosis resumption from preantral follicles of goats when grown in vitro.

Viability and growth of buffalo preantral follicles and their corresponding oocytes in vitro: effect of growth factors and beta mercaptoethanol

The present study was undertaken to isolate buffalo preantral follicles (PFs), to test the viability and sizes of buffalo PFs and to examine the effect of various growth factors (insulin-like growth factor, fibroblast growth factor) and an antioxidant (beta mercaptoethanol) on the in vitro growth, survival and antrum formation rates of buffalo PFs and growth rates of oocytes in cultured PFs. Preantral follicles from slaughtered buffalo ovaries were recovered by a combined mechanical and enzymatic method. The recovery rates of >40-100, 101-200, 201-300, 301-400 and 401-500 microm PFs were 5.1, 3.2, 3.1, 6.3 and 5.1 per ovary, respectively. The corresponding viability rates were 76.1%, 78.1%, 85.2%, 92.5% and 92.6%, respectively. There was a positive correlation (r = 0.73) between oocyte size and the follicular size. However, there was no significant correlation between the size of oocyte and its viability at the time of its retrieval from ovary. Insulin-like growth factor and fibroblast growth factor improved the survival of buffalo PFs and regulated their growth in culture. The growth factors and beta mercaptoethanol in association synergically improved the growth and survival of buffalo PFs.

Survival and developmental competence of buffalo preantral follicles using three-dimensional collagen gel culture system

The aim of the present study was to develop a three-dimensional (3D) collagen gel culture system for the in vitro growth and survival of buffalo preantral follicles with or without growth factors. Buffalo ovaries were collected from a local abattoir and preantral follicles were isolated through microdissection. Isolated preantral follicles were put either in collagen gel coated culture dish or embedded in a microdrop of collagen gel. The culture medium was TCM-199 fortified with fetal calf serum (10%), insulin transferin selenium solution (ITS, 1%), epidermal growth factor (EGF, 20 ng/ml) and follicle stimulating hormone (FSH, 0.5 microg/ml). Follicles were divided into three groups and cultured in the medium described above (group a, control), with addition of insulin like growth factor (IGF-I, 100 ng/ml, group b), or with addition of IGF-I and basic fibroblast growth factor (bFGF, 10 ng/ml, group c). Preantral follicles were incubated at 38.5 degrees C in 5% CO(2) and maximum humidity. Culture medium was replenished after every 72 h and spent medium was stored at -30 degrees C for hormone analysis. We found that the extracellular matrix of collagen gel maintained follicle viability and growth by providing surface interaction and increasing attachment of follicles. Preantral follicles embedded in collagen gel droplets had better antrum formation and development as compared to the whole surface coated culture method. Follicles cultured with IGF-I on collagen gel matrix showed a significantly (P<0.05) higher survival rate and larger mean diameter of follicles on day 10 of culture with improved growth and mucification as compared to the control group. However, follicles cultured in the combination of IGF-I with bFGF had decreased survival rate and smaller mean follicles diameter than the IGF-I group (b). Progesterone (P(4)) accumulation was greater on day 9 of culture in follicles cultured in IGF-I as compared to control; whereas, P(4) was markedly decreased in the combination of IGF-I with bFGF. Follicles of the control group could survive for up to 10-15 days before degenerating, but follicles cultured with growth factors were able to survive up to 20 days and showed signs of early antrum formation. In summary, we have shown that collagen gel was a novel and efficacious 3D microenvironment for the extended culture of buffalo preantral follicles. Supplementation of culture medium with growth factors was found to be essential for antrum formation.

Effect of a partially purified 30.1 kDa ovine follicular fluid protein on ovine follicle and ovarian somatic cell growth, and oocyte maturation in vitro

AIM

Regulation of folliculogenesis and oocyte-somatic cell interactions in the ovarian follicles is under the control of gonadotrophins and various local factors. In the present study, an attempt was made to isolate and examine the biological activities of ovarian follicular fluid protein(s) in sheep in vitro.

METHODS

Follicular fluids aspirated from ovarian follicles of slaughterhouse-derived ovaries were made cell free by centrifugation (5000 g for 30 min) and steroid free by charcoal treatment. The follicular fluid was then subjected to ammonium sulphate precipitation and gel filtration chromatography using G-75 Sephadex. Protein detection was performed using a UV spectrophotometer at 280 nm. The 35-50% fraction yielded a detectable peak and a protein of 30.1 kDa as examined by SDS-PAGE. The effect of increasing doses of the 30.1 kDa ovine follicular fluid protein (oFFP) was tested at different doses on pre-antral and antral follicle growth; cumulus cell expansion; oocyte maturation; changes in protein, calcium and phosphorus levels of oocytes after culture in media containing different levels of isolated protein; mural granulosa cell, polar granulosa cell (cumulus cell), oviductal epithelial cell monolayer formation and granulosa cell proliferation in vitro.

RESULTS

The oFFP significantly inhibited antral follicle growth, cumulus expansion, oocyte maturation and somatic cell growth in vitro in a dose-dependent manner. The oFFP did not have a significant effect on the pre-antral follicle growth in vitro. The protein, calcium and phosphorus contents of oocytes were found to decrease in oocytes cultured in maturation medium containing the oFFP.

CONCLUSION

The present study demonstrates a follicular fluid factor regulating folliculogenesis and oocyte maturation in sheep.

Production of buffalo embryos using oocytes from in vitro grown preantral follicles

The present study examines the use of buffalo preantral follicles as a source of oocytes for in vitro embryo production. Preantral follicles were isolated from abattoir-derived buffalo ovaries and were grown for 100 days in five different culture systems: (1) minimum essential medium (MEM); (2) coconut water; (3) MEM + ovarian mesenchymal cell (OMC) co-culture; (4) MEM + granulosa cell (GC) co-culture; or (5) MEM + cumulus cell (CC) co-culture. Low growth rates for the preantral follicles were observed when follicles were cultured in MEM or coconut water medium. Moderate growth rates were seen for OMC and GC co-cultures, and high rates of growth were observed when follicles were grown in CC co-culture. The survival of preantral follicles was low in the MEM culture (<25%), but was over 75% in the other culture systems. Oocytes were not recovered from the MEM group, while an oocyte recovery rate of 80-100% was observed when the follicles were cultured with coconut water/somatic cells. Transferable embryos could be produced only with the oocytes obtained from preantral follicles grown in the OMC and CC co-culture systems. This study demonstrates, for the first time, that it is possible to produce buffalo embryos by in vitro fertilization of oocytes derived from in vitro grown preantral follicles.

Co-culture of buffalo preantral follicles with different somatic cells

The effect of co-culture of buffalo preantral follicles (PFs) with different somatic cells, i.e, cumulus, granulosa, ovarian mesenchymal and oviductal epithelial cells was studied. Large PFs (250-450 microm) were isolated by microdissecting the trypsin (1%) digested ovarian cortical slices. Cumulus cells were isolated by repeated pipetting of oocytes, granulosa cells were isolated by aspirating from punctured PFs and ovarian mesenchymal cells were isolated from ovarian cortex by scraping the cortical slices and passing through 20 microm filter. Preantral follicles were cultured in standard culture medium without somatic cells or co-cultured with cumulus cells, granulosa cells, ovarian mesenchymal cells and oviductal epithelial cells for 80 days. The growth rate (microm/day) of the PFs was monitored by measuring follicular diameter on day 0, 30, 60 and 80 days of culture. The viability of PFs was evaluated by trypan blue staining. The results indicated that PFs co-cultured with cumulus, granulosa and ovarian mesenchymal cells had a better development and survivality compared with control and those co-culture with oviductal epithelial cells. Maximum growth and survivality of PFs were achieved when cultured with cumulus cells. It is concluded that inclusion of somatic cells in PF culture media had beneficial effect on the growth of PFs and cumulus cells supported maximum growth and survivality of PFs in vitro of all somatic cells tested.

Recovery of large preantral follicles from buffalo ovary: Effect of season and corpus luteum

Preantral follicle can be considered as an alternative source of oocyte for in vitro production of embryos. The objective of the present study was to standardize a procedure for the isolation of large preantral follicles (>150-500 microm) from buffalo ovaries and to determine the effect of season and the presence of corpus luteum on the recovery rate of the large preantral follicles. A combined enzymatic cum mechanical approach was adopted to recover the large preantral follicles. In the first experiment, the ovarian cortical pieces were suspended in trypsin (1000-1500 BAEE units for milligrams of solid) and incubated at various temperatures for different periods, i.e. (1) trypsin (1%), 37 degrees C for 10 min; (2) trypsin (1%), 37 degrees C for 10 min + 4 degrees C for 3 h; (3) trypsin (0.5%), 37 degrees C for 20 min; (4) trypsin (0.25%), 37 degrees C for 20 min. Although there was no significant difference (P>0.05) among the different protocols, the first protocol yielded more follicles (3.2, 2.6, 1.8 and 1.5 per ovary, respectively). Hence, the first protocol was selected and used in the second and third experiments. In the second experiment, the effect of season, i.e. peak breeding season (October-March) versus low breeding season (April-September) was evaluated on the recovery rate of the large preantral follicles. The recovery rate of large preantral follicles from the ovaries during the peak breeding season was significantly (P<0.05) greater (9.92+/-0.85 per ovary) than that of the low breeding season (4.95+/-0.27 per ovary). In the third experiment, effect of the presence of corpus luteum on the recovery rate of large preantral follicles was studied. There was a significantly (P<0.05) higher yield of large preantral follicles from the ovaries with corpus luteum (8.05+/-0.88 per ovary) than for the ovaries without corpus luteum (4.57+/-0.43 per ovary). This study confirms that the large preantral follicles can be isolated from buffalo ovaries using a combination of enzymatic cum mechanical methods and that more large preantral follicles can be recovered during the peak breeding season and from the ovaries having corpus luteum.

Total anti-oxidant capacity of cell culture media

1. The composition of synthetic cell culture media is important for the behaviour of cultured cells in vitro and may affect the results of many in vitro experiments. The total anti-oxidant capacity (TAC) of an extracellular medium may be an important factor in cell redox homeostasis. 2. In the present study, the TAC of cell culture media used for the cultivation of mammalian, yeast and bacterial cells (RPMI1640, Iscove's modified Dulbecco's medium, Dulbecco's modified Eagle's medium, minimum essential medium Eagle's 1959 with Earle's salts, Parker medium 199 with Hanks salts, bacterial Luria-Bertani medium, yeast extract-peptone-glucose and yeast nitrogen base media) was estimated using the 2,2'-azinobis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS(.+)) decolourization assay and the ferric ion reducing anti-oxidant power assay. 3. We found that components of the media such as cysteine, tyrosine, tryptophan and Phenol Red are important contributors to the TAC of cell culture media.

Isolation, follicular density, and culture of preantral follicles of buffalo fetuses of different ages

The aim of the present study was to determine the most desirable ovarian tissue section thickness to isolate preantral follicles (Experiment I), determine follicular density (follicles/mm(2) of cortex) of ovaries of fetal buffalo of different ages (Experiment II), and cultivate preantral follicles of buffalo fetuses (Experiment III). In Experiment I, ovary sections with different thicknesses (25, 50, 75, and 100 microm) had 415.0+/-285.2, 457.5+/-341.9, 585.0+/-309.3, and 685.0+/-278.8 isolated preantral follicles, respectively. In Experiment II, the follicular density of 46 buffalo fetuses with ages between 3 and 8 months was estimated to be between 0 and 7220, with means of 0.0, 2070.7+/-2190.3, 2570.8+/-1796.6, 2298.1+/-2286.5, 1277.5+/-1074.9, and 643.6+/-543.9 throughout the age range studied. The follicular density of 5-month-old fetuses was greatest, coinciding with the largest number of follicles isolated at this age. In Experiment III, preantral follicles isolated from the ovaries of buffalo fetuses aged from 5 to 9 months old were cultivated individually for 7 days in four different media: basic medium (Minimal Essential Medium (MEM), 10% SFB, kanamycin, pyruvate, glutamine, hypoxanthine) with additional ITS and FSH 0.5mg/ml (treatment 1); basic medium with FSH and EGF 100 ng/ml (treatment 2); basic medium with additional ITS, FSH, and EGF (treatment 3); basic medium supplemented with ITS and EGF (treatment 4). Integrity and morphological features, viability, and increase in diameter of follicles cultured in vitro were evaluated individually with an inverted microscope and an ocular micrometer. The results showed that follicle structure and form were maintained during culture. Growth and survival rates of treatments 1, 2, and 3 over 7 day culture were 23.25+/-17.06, 33.75+/-26.19, and 43.75+/-31.73 microm, and 31.3+/-22.7, 22.06+/-8.13, and 28.92+/-21.32%, respectively. However, neither growth nor survival was observed in treatment 4. In conclusion, this study showed that preantral follicles of buffalo fetuses can be cultured in vitro, and that FSH is essential for follicle survival.

Expression of mRNA and protein localization of epidermal growth factor and its receptor in goat ovaries

To examine the possibility that epidermal growth factor (EGF) and its receptor (EGF-R) are expressed throughout folliculogenesis, we studied the presence and distribution of EGF and EGF-R in goat ovaries. Ovaries of goats were collected and either fixed in paraformaldehyde for immunohistochemical localization of proteins, or used for the isolation of follicles, luteal cells and ovarian surface epithelium to study mRNA expression for EGF and EGF-R, using the reverse transcriptase polymerase chain reaction. EGF protein and mRNA were found in primordial, primary and secondary follicles as well as in small and large antral follicles and in surface epithelium, but in corpora lutea only the protein could be detected. Antral follicles expressed EGF mRNA in oocyte, cumulus, mural granulosa and theca cells. For EGF-R, both protein and mRNA were present at all stages of follicular development and in all antral follicular compartments. EGF-R protein and mRNA were also found in corpora lutea and surface epithelium. It is concluded that EGF and its receptor are expressed in goat ovarian follicles at all stages of follicle development, in corpora lutea, and in ovarian surface epithelium.

Effect of growth factors on in vitro development of caprine preantral follicle oocytes

The objective of this work was to examine the effect of various growth factors including epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I), either individually or in association, in the presence of follicle stimulating hormone (FSH) on the in vitro growth and viability of caprine preantral follicle oocytes. Preantral follicles were disassociated enzymatically and mechanically from prepuberal caprine ovaries after the animals were anesthetically ovariectomized. In experiment, caprine preantral follicles in groups 1-4 were cultured in growth culture medium, growth culture medium+EGF, growth culture medium+IGF-I and growth culture medium+IGF-I+EGF, respectively, for 9 days. The results indicated that EGF (50 mg/l) increased the survival rate of oocytes, but decreased the growth rate of oocytes; IGF-I (100 mg/l) effectively maintained the survival of oocytes and stimulated their growth; IGF-I (100 mg/l) and EGF (50mg/l) in combination produced a higher effect on both of the survival and the growth rate of oocytes than IGF-I or EGF alone. Conclusively, the growth factors can effectively maintain the survival of caprine preantral follicle oocytes and regulated their growth in culture. EGF and IGF-I in association could synergically meliorate the culture system of caprine preantral follicle oocytes.

A Reference Preparation of Buffalo Pituitary Follicle Stimulating Hormone using Lectin Affinity Chromatography

An improved and cost effective method to isolate FSH from buffalo pituitary glands is described here. The buFSH activity was monitored throughout by a highly sensitive heterologous radioimmunoassay (sensitivity 0.2 ng oFSH/mL) and the in vivo biological activity of the final preparation was also established. A biologically active buFSH-enriched preparation with a moderate recovery (42%) was obtained. The yield of the final buFSH-enriched preparation was 26.5 mg/kg of buffalo pituitary gland. In SDS-PAGE, the purified buFSH resolved as a heterodimer of 30 kDa molecular size, with a 21 kDa presumptive alpha-subunit. This preparation was also characterized in terms of biological and some of its physicochemical properties. A high-titer antiserum to buFSH was also raised in rabbit using this preparation. The reagents generated, buFSH and buFSH-specific polyclonal antisera, have possible diagnostic and therapeutic usage for improvement of reproductive health of water buffaloes.

Regulation of in vitro growth of preantral follicles by growth factors in goats

Goat preantral follicles were cultured to investigate the effects of insulin-like growth factor-I (IGF-I), epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) on the in vitro growth and viability of oocytes. Preantral follicles were isolated mechanically and enzymatically (using collagenase and DNase) from prepuberal goat ovaries. The working medium was composed of Defined Eagle's Minimum Essential Medium (DMEM) supplemented with HEPES (20 mM), 10% fetal calf serum (FCS), hypoxanthine (2 mM), dibutyryl cyclic adenosine 3',5'-monophosphate (dbcAMP) (2 mM), penicillin (75 ng/ml) and streptomycin (50 ng/ml). The culture medium consisted of the working medium with follicle stimulating hormone (FSH) (100 ng/ml) and hydrocortisone (40 ng/ml) added. In the experiment, goat preantral follicles were cultured for 9 days in the culture medium and in the culture medium supplemented with either IGF-I (100 ng/ml), EGF (50 ng/ml), bFGF (50 ng/ml) or IGF-I (100 ng/ml)+EGF (50 ng/ml). The results indicated that IGF-I (100 ng/ml) effectively maintained the survival of oocytes and promoted their growth; EGF (50 ng/ml) enhanced the survival rate of oocytes but had a negative effect on oocyte growth; bFGF (50 ng/ml) stimulated oocyte survival but had no obvious effect on their growth while IGF-I (100 ng/ml) and EGF (50 ng/ml) in combination had a greater effect on both survival and growth rate of oocytes than IGF-I or EGF alone. The supplementation of IGF-1 and EGF to the culture medium is recommended in the culture of goat preantral follicles.

Impact of Growth Factors on In Vitro Development of Caprine Oocytes at Pre-antral Stage

The objective of this study was to examine the effect of various growth factors such as the epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I) either individually or in association, in the presence of follicle-stimulating hormone (FSH) on the in vitro growth and viability of caprine oocytes at pre-antral stage. Pre-antral follicles were disassociated enzymatically and mechanically from pre-pubertal caprine ovaries after the animals were anaesthetically ovariectomized. Caprine pre-antral follicles in group 1, 2, 3 and 4 were cultured in growth culture medium, growth culture medium + EGF, growth culture medium + IGF-I and growth culture medium + IGF-I + EGF, respectively, for 9 days. The results indicated that EGF (50 mg/l) increased the survival rate of oocytes, but decreased the growth rate of oocytes; IGF-I (100 mg/l) effectively maintained the survival of oocytes and stimulated their growth; IGF-I (100 mg/l) and EGF (50 mg/l) in combination produced a higher effect on both the survival and the growth rate of oocytes than IGF-I or EGF alone. Conclusively, the growth factors can effectively maintain the survival of caprine oocytes from pre-antral follicles and regulate their growth in culture. EGF and IGF-I in association could synergically meliorate the culture system of caprine pre-antral follicles.

Production of buffalo (Bubalus bubalis) embryos in vitro: premises and promises

Techniques for in vitro production (IVP) of buffalo embryos adopting the procedures developed in cattle have received increasing interest in the recent times. A high oocyte maturation, fertilization and cleavage rate and a low rate of blastocyst yield and calving following transfer of in vitro produced buffalo embryos have been obtained. The efficiency of IVP in buffalo is much lower than that in cattle. Several problems need to be resolved before IVP technology can be used regularly in buffalo breeding. This review attempts to present an overview of the different techniques used in buffalo to produce transferable embryos in vitro, namely in vitro maturation and fertilization of immature oocytes and in vitro development of the resulting cleaved embryos to the blastocyst stage before transfer. The problems associated with IVP, the possible solutions and the new biotechniques linked to IVP are discussed.