Ultra-structural characteristics of bovine granulosa cells associated with maintenance of oestradiol production in vitro

Bioengineering Approaches to Improve In Vitro Performance of Prepubertal Lamb Oocytes

Juvenile in vitro embryo technology (JIVET) provides exciting opportunities in animal reproduction by reducing the generation intervals. Prepubertal oocytes are also relevant models for studies on oncofertility. However, current JIVET efficiency is still unpredictable, and further improvements are needed in order for it to be used on a large-scale level. This study applied bioengineering approaches to recreate: (1) the three-dimensional (3D) structure of the cumulus–oocyte complex (COC), by constructing—via bioprinting technologies—alginate-based microbeads (COC-microbeads) for 3D in vitro maturation (3D-IVM); (2) dynamic IVM conditions, by culturing the COC in a millifluidic bioreactor; and (3) an artificial follicular wall with basal membrane, by adding granulosa cells (GCs) and type I collagen (CI) during bioprinting. The results show that oocyte nuclear and cytoplasmic maturation, as well as blastocyst quality, were improved after 3D-IVM compared to 2D controls. The dynamic 3D-IVM did not enhance oocyte maturation, but it improved oocyte bioenergetics compared with static 3D-IVM. The computational model showed higher oxygen levels in the bioreactor with respect to the static well. Microbead enrichment with GCs and CI improved oocyte maturation and bioenergetics. In conclusion, this study demonstrated that bioengineering approaches that mimic the physiological follicle structure could be valuable tools to improve IVM and JIVET.

Expression profiling of primary cultured buffalo granulosa cells from different follicular size in comparison with their in vivo counterpart

This study aimed to: (i) characterize cultured granulosa cells (GCs) from different follicle sizes morphologically and molecularly; and (ii) select a suitable model according to follicular size that maintained GC function during culture. Buffalo ovaries were collected from a slaughterhouse and follicles were classified morphologically into: first group ≤ 4 mm, second group 5-8 mm, third group 9-15 mm and fourth group 16-20 mm diameter. GC pellets were divided into two portions. The first portion served as the control fresh pellet, and the secondwas used for 1 week for GC culture. Total RNA was isolated, and qRT-PCR was performed to test for follicle-stimulating hormone receptor (FSHR), cytochrome P450 19 (CYP19), luteinizing hormone/choriogonadotropin receptor (LHCGR), proliferating cell nuclear antigen (PCNA), apoptosis-related cysteine peptidase (CASP3), anti-Müllerian hormone (AMH), and phospholipase A2 group III (PLA2G3) mRNAs. Estradiol (E2) and progesterone (P4) levels in the culture supernatant and in follicular fluids were measured using enzyme-linked immunosorbent assay (ELISA). Basic DMEM-F12 medium maintained the morphological appearance of cultured GCs. The relative abundance of FSHR, CYP19, and LHCGR mRNAs was 0.001 ≤ P ≤ 0.01 and decreased at the end of culture compared with the fresh pellet. There was a fine balance between expression patterns of the proliferation marker gene (PCNA) and the proapoptotic marker gene (CASP3). AMH mRNA was significantly increased (P < 0.001) in cultured GCs from small follicles, while cultured GCs from other three categories (5-8 mm, 9-15 mm and 16-20 mm) showed a clear reduction (P < 0.001). Interestingly, the relative abundance of PLA2G3 mRNA was significantly (P < 0.001) increased in all cultured GCs. E2 and P4 concentrations were significantly (P < 0.001) decreased in all cultured groups. Primary cultured GCs from small follicles could be a good model for better understanding follicular development in Egyptian buffaloes.

Physiological responses of cultured bovine granulosa cells to elevated temperatures under low and high oxygen in the presence of different concentrations of melatonin

Our understanding of the effects of temperature on granulosa cell (GC) physiology is primarily limited to in vitro studies conducted under atmospheric (∼20% O₂) conditions. In the current series of factorial experiments we identify important effects of O₂ level (i.e. 5% vs 20% O₂) on GC viability and steroidogenesis, and go onto report effects of standard (37.5 °C) vs high (40.0 °C) temperatures under more physiologically representative (i.e. 5%) O₂ levels in the presence of different levels of melatonin (0, 20, 200 and 2000 pg/ml); a potent free-radical scavenger and abundant molecule within the ovarian follicle. Cells aspirated from antral (4-6 mm) follicles were cultured in fibronectin-coated wells using serum-free M199 for up to 144 h. At 37.5 °C viable cell number was enhanced and luteinization reduced under 5 vs 20% O₂. Oxygen level interacted (P < 0.001) with time in culture to affect aromatase activity and cell estradiol (E₂) production (pg/mL/10⁵ cells). These decreased between 48 and 96 h for both O₂ levels but increased again by 144 h for cells cultured under 5% but not 20% O₂. Progesterone (P₄) concentration (ng/mL/10⁵ cells) was greater (P < 0.001) under 20 vs 5% O₂ at 96 and 144 h. Cell number increased (P < 0.01) with time in culture under 5% O₂ irrespective of temperature. However, higher doses of melatonin increased viable cell number at 40.0 °C but reduced viable cell number at 37.5 °C (P = 0.004). Melatonin also reduced (P < 0.001) ROS generation at both O₂ levels across all concentrations. E₂ increased with time in culture at both temperatures under 5% O₂, however P₄ declined between 96 and 144 h at 40.0 but not 37.5 °C. Furthermore, melatonin interacted (P < 0.001) with temperature in a dose dependent manner to increase P₄ at 37.5 °C but to reduce P₄ at 40.0 °C. Transcript expression for HSD3B1 paralleled temporal changes in P₄ production, and those for HBA were greater at 5% than 20% O₂, suggesting that hemoglobin synthesis is responsive to changes in O₂ level. In conclusion, 5% O₂ enhances GC proliferation and reduces luteinization. Elevated temperatures under 5% O₂ reduce GC proliferation and P₄ production. Melatonin reduces ROS generation irrespective of O₂ level and temperature, but interacts with temperature in a dose dependent manner to influence GC proliferation and luteinization.

Norepinephrine stimulates progesterone production in highly estrogenic bovine granulosa cells cultured under serum-free, chemically defined conditions

BACKGROUND

Since noradrenergic innervation was described in the ovarian follicle, the actions of the intraovarian catecholaminergic system have been the focus of a variety of studies. We aimed to determine the gonadotropin-independent effects of the catecholamine norepinephrine (NE) in the steroid hormone profile of a serum-free granulosa cell (GC) culture system in the context of follicular development and dominance.

METHODS

Primary bovine GCs were cultivated in a serum-free, chemically defined culture system supplemented with 0.1% polyvinyl alcohol. The culture features were assessed by hormone measurements and ultrastructural characteristics of GCs.

RESULTS

GCs produced increasing amounts of estradiol and pregnenolone for 144h and maintained ultrastructural features of healthy steroidogenic cells. Progesterone production was also detected, although it significantly increased only after 96h of culture. There was a highly significant positive correlation between estradiol and pregnenolone production in high E2-producing cultures. The effects of NE were further evaluated in a dose-response study. The highest tested concentration of NE (10 (-7) M) resulted in a significant increase in progesterone production, but not in estradiol or pregnenolone production. The specificity of NE effects on progesterone production was further investigated by incubating GCs with propranolol (10 (-8) M), a non-selective beta-adrenergic antagonist.

CONCLUSIONS

The present culture system represents a robust model to study the impact of intrafollicular factors, such as catecholamines, in ovarian steroidogenesis and follicular development. The results of noradrenergic effects in the steroidogenesis of GC have implications on physiological follicular fate and on certain pathological ovarian conditions such as cyst formation and anovulation.

Unravelling the needs of singly in vitro-produced bovine embryos: from cumulus cell co-culture to semi-defined, oil-free culture conditions

Producing bovine in vitro embryos individually is a challenge as it generally leads to impaired embryo development. Earlier research optimised a single embryo in vitro production (IVP) protocol using serum, cumulus cells and oil during culture. As some of these factors are undesirable in certain circumstances, the present study investigated their necessity and possible interactions, and defined their role during single-embryo culture. Although the cumulus cell monolayer produced progesterone, it appeared not to be a key factor in supporting single-embryo development. Because in vitro culture in large medium volumes was shown to impair single-embryo development, two new oil-free culture protocols were tested. Using a 30-µL droplet of medium in 96-well plates with a small surface area resulted in comparable blastocyst rates to those obtained under oil. When serum was used, co-culture with cumulus cells seems necessary, leading to consistently high blastocyst rates. Finally, a serum-free, oil-free culture system using insulin, transferrin, selenium and BSA resulted in embryos with similar total cell numbers and apoptotic cell ratios, but blastocyst rates did not equal those obtained with serum and co-culture. This research additionally stresses the fact that specific interaction mechanisms between somatic cells and a developing in vitro embryo are far from unravelled.

Proliferative potential and phenotypic analysis of long-term cultivated human granulosa cells initiated by addition of follicular fluid

PURPOSE

The aim of this study was to develop and optimize a strategy for long-term cultivation of luteinizing human granulosa cells (GCs).

METHODS

GCs were cultivated in DMEM/F12 medium supplemented with 2% fetal calf serum. In vitro proliferation of GCs was supported by follicular fluid as well as FSH and growth factors.

RESULTS

The cultured GCs were maintained for 45 days with a doubling time of 159 ± 24 h. GCs initiated by the addition of follicular fluid and cultivated under low serum conditions reached 10 ± 0.7 population doublings. GCs maintain the typical phenotypic expression and the telomere length according to specific culture conditions.

CONCLUSION

Our present study has demonstrated that GCs can be maintained in vitro for at least 45 days and this cell model can be beneficial when studying hormonal regulation associated with follicular maturation and preparation of oocytes for fertilization.

In vitro maturation of human oocytes in a follicle-mimicking three-dimensional coculture

OBJECTIVE

To verify the hypothesis that a three-dimensional, follicle-mimicking structure enhances in vitro maturation yields without hormonal supplementation in an in vitro maturation program.

DESIGN

Feasibility study; 204 anonymous denuded germinal vesicles retrieved from gonadotropin-treated women were cultured for 48 hours without hormonal supplementation in microdrop culture or in a three-dimensional coculture with granulosa cells in a barium alginate membrane.

SETTING

An assisted reproduction center in Italy.

PATIENT(S)

One hundred twenty-two informed women.

INTERVENTION(S)

Germinal vesicles retrieved after ovarian stimulation were denuded and cultured without hormonal supplementation in microdrop culture or in a three-dimensional coculture with granulosa cells enclosed in the core of a barium alginate capsule.

MAIN OUTCOME MEASURE(S)

Oocyte maturation and morphological investigation of follicle-mimicking structures.

RESULT(S)

Statistically significantly higher oocyte maturation yields were obtained by using the three-dimensional coculture system enclosed in a barium alginate membrane (after 48 hours: coculture, 90.3%; microdrop, 52.0%; odds ratio, 8.51). Morphological investigation indicated that after 48 hours of coculture, the decumulated oocyte appeared to be surrounded by a pseudocumulus structure that lies on the inner surface of the alginate membrane and protrudes toward the capsule's lumen.

CONCLUSION(S)

The maturation yield of cocultured oocytes is eightfold higher than that achieved with a microdrop maturation technique, making a higher number of gametes available for IVF programs. Stereomicroscopic morphological survey indicates a reassembly of granulosa cells surrounding oocyte zona, mimicking an antral cumulus oophorus.

Transient transfection of porcine granulosa cells after 3D culture in barium alginate capsules

Three-dimensional culture systems in barium alginate capsules can be employed to maintain primary granulosa cells in an undifferentiated state for almost 6 days. This is due to a self-organization of cells in a pseudofollicular structure. The transfection of primary granulosa cells is a necessary condition when employing these culture systems for several purposes, for example as an in vitro toxicity test or the development of oocytes or zygotes. In this work, the feasibility of two transient transfection techniques (liposome-mediated and electroporation) was assessed in primary porcine granulosa cells after a 6-day culture in an artificial extracellular matrix (barium alginate membrane). Human recombinant green fluorescent protein was chosen as a molecular readout, and protein expression was assessed after 48 hours from transfection. Liposome-mediated transfection gave low transfection levels, with increasing yields from 2 to 12 microgDNA/ml of medium; the maximum percentage (85.7%) was reached at 12 microgDNA/ml of medium. Electroporation-mediated transfection yields were higher: the best results (81.7% of transfected cells) were achieved with two 50V pulses and 12 microg/ml DNA. The application of a single or double pulse (50V) at 4 mgDNA/ml gave negligible results. These results indicate that primary granulosa cell cultured in barium alginate capsules can be transfected by electroporation with high transfection yields.

Follicle-Like Model by Granulosa Cell Encapsulation in a Barium Alginate–Protamine Membrane

Granulosa cells from bovine and porcine ovaries were cultured either in monolayer or in follicle-like barium alginate capsules for 6 days. Morphological investigation by electron scanning microscopy indicated that culture in a three-dimensional (3D) system allows self-organization of spherical-polyhedral shape cells. The luteinization index (progesterone:17beta-estradiol ratio) was significantly higher for monolayer cells than for the 3D cell culture system, confirming the results of morphological analysis and indicating more physiological growth. The encapsulated 3D culture system appears to be a promising way of obtaining in vitro maturation and development of follicles and oocytes.

Paracrine effects of oocyte secreted factors and stem cell factor on porcine granulosa and theca cells in vitro

Oocyte control of granulosa and theca cell function may be mediated by several growth factors via a local feedback loop(s) between these cell types. This study examined both the role of oocyte-secreted factors on granulosa and thecal cells, cultured independently and in co-culture, and the effect of stem cell factor (SCF); a granulosa cell derived peptide that appears to have multiple roles in follicle development. Granulosa and theca cells were isolated from 2-6 mm healthy follicles of mature porcine ovaries and cultured under serum-free conditions, supplemented with: 100 ng/ml LR3 IGF-1, 10 ng/ml insulin, 100 ng/ml testosterone, 0-10 ng/ml SCF, 1 ng/ml FSH (granulosa), 0.01 ng/ml LH (theca) or 1 ng/ml FSH and 0.01 ng/ml LH (co-culture) and with/without oocyte conditioned medium (OCM) or 5 oocytes. Cells were cultured in 96 well plates for 144 h, after which viable cell numbers were determined. Medium was replaced every 48 h and spent medium analysed for steroids. Oocyte secreted factors were shown to stimulate both granulosa cell proliferation (P < 0.001) and oestradiol production (P < 0.001) by granulosa cells throughout culture. In contrast, oocyte secreted factors suppressed granulosa cell progesterone production after both 48 and 144 hours (P < 0.001). Thecal cell numbers were increased by oocyte secreted factors (P = 0.02), together with a suppression in progesterone and androstenedione synthesis after 48 hours (P < 0.001) and after 144 hours (P = 0.02), respectively. Oocyte secreted factors also increased viable cell numbers (P < 0.001) in co-cultures together with suppression of progesterone (P < 0.001) and oestradiol (P < 0.001). In granulosa cell only cultures, SCF increased progesterone production in a dose dependent manner (P < 0.001), whereas progesterone synthesis by theca cells was reduced in a dose dependent manner (P = 0.002). Co-cultured cells demonstrated an increase in progesterone production with increasing SCF dose (P < 0.001) and an increase in oestradiol synthesis at the highest dose of SCF (100 ng/ml). In summary, these findings demonstrate the presence of a co-ordinated paracrine interaction between somatic cells and germ cells, whereby oocyte derived signals interact locally to mediate granulosa and theca cell function. SCF has a role in modulating this local interaction. In conclusion, the oocyte is an effective modulator of granulosa-theca interactions, one role being the inhibition of luteinization.

Effect of extracellular matrix proteins on in vitro testosterone production by rat Leydig cells

The aim of this study was to detect the effect of extracellular matrix (ECM) proteins on rat Leydig cell shape, adhesion, expression of integrin subunits and testosterone production, in vitro. Leydig cells isolated from adult rats were cultured on plates uncoated or coated with different concentrations of laminin-1, fibronectin, or type IV collagen in the presence or absence of hCG for 3 or 24 hr. A significant increase of cell adhesion and of alpha3, alpha5, and beta1 integrin subunit expression was observed when cells were cultured on ECM proteins, compared to those grown on uncoated plates. Leydig cells cultured on glass coverslips coated with ECM proteins for 24 hr exhibited elongated shapes with long cell processes (spreading), while cells cultured on uncoated plates showed few cell processes. A significant decrease in testosterone production was observed when basal and hCG-stimulated Leydig cells were cultured for 3 or 24 hr on plates coated with type IV collagen (12 and 24 microg/cm(2)) compared to uncoated plates. A significant though a slighter decrease in testosterone production was also observed in cells cultured on plates coated with fibronectin (12 and 24 microg/cm(2)), compared to uncoated plates. Laminin-1 did not modify testosterone production under basal or hCG stimulated conditions. These results suggest that ECM proteins are able to modulate Leydig cell steroidogenesis, in vitro.

Models of luteinization

Luteinization is essential to the success of early gestation. It is the process by which elements of the ovarian follicle, usually including both theca interna and granulosa cells, are provoked by the ovulatory stimulus to develop into the corpus luteum. Although there are significant species differences in luteinization, some elements pervade, including the morphological and functional differentiation to produce and secrete progesterone. There is evidence that luteinization results in granulosa cell exit from the cell cycle. The mechanisms that appear to control luteinization include intracellular signalling pathways, cell adhesion factors, intracellular cholesterol and oxysterols, and perhaps progesterone itself as a paracrine or intracrine regulator. Cell models of luteinization, along with some of the conflicting observations on the luteinization process, are discussed in this review.

Growth and antrum formation of bovine preantral follicles in long-term culture in vitro

Culture of preantral follicles has important biotechnological implications through its potential to produce large quantities of oocytes for embryo production and transfer. A long-term culture system for bovine preantral follicles is described. Bovine preantral follicles (166 +/- 2.15 micrometer), surrounded by theca cells, were isolated from ovarian cortical slices. Follicles were cultured under conditions known to maintain granulosa cell viability in vitro. The effects of epidermal growth factor (EGF), insulin-like growth factor (IGF)-I, FSH, and coculture with bovine granulosa cells on preantral follicle growth were analyzed. Follicle and oocyte diameter increased significantly (P < 0.05) with time in culture. FSH, IGF-I, and EGF stimulated (P < 0.05) follicle growth rate but had no effect on oocyte growth. Coculture with granulosa cells inhibited FSH/IGF-I-stimulated growth. Most follicles maintained their morphology throughout culture, with the presence of a thecal layer and basement membrane surrounding the granulosa cells. Antrum formation, confirmed by confocal microscopy, occurred between Days 10 and 28 of culture. The probability of follicles reaching antrum development was 0.19 for control follicles. The addition of growth factors or FSH increased (P < 0.05) the probability of antrum development to 0.55. Follicular growth appeared to be halted by slower growth of the basement membrane, as growing follicles occasionally burst the basement membrane, extruding their granulosa cells. In conclusion, a preantral follicle culture system in which follicle morphology can be maintained for up to 28 days has been developed. In this system, FSH, EGF, and IGF-I stimulated follicle growth and enhanced antrum formation. This culture system may provide a valuable approach for studying the regulation of early follicular development and for production of oocytes for nuclear/embryo transfer, but further work is required.