N. N. Costa

Expression of PLIN2 and PLIN3 during oocyte maturation and early embryo development in cattle.

In vitro-produced embryos store high lipid content in cytoplasmic lipid droplets (LD), and reduction or removal of LD has been demonstrated to improve freeze-thaw viability. The Perilipin Adipophilin Tail-interacting Protein of 47 kD (PAT) family of proteins is involved in the formation and regulation of LD in many cell types, but their presence has not been addressed either in cattle oocytes or preimplantation embryos. Therefore, this study aimed to detect the expression of PAT family transcripts (Perilipin-2 [PLIN2] and Perilipin-3 [PLIN3]) in immature and in vitro-matured (IVM) oocytes, and in in vitro-produced embryos at the stages of two to four cells, eight to 16 cells, morulae (MO), and blastocyst (BL). The expression of PLIN3 was downregulated in response to IVM, and PLIN2 was comparatively more expressed than PLIN3 in IVM oocytes (P < 0.001). During the early stages of embryo development, PLIN2 expression reached its peak at the MO stage (P < 0.001) and decreased again at the BL stage. In contrast, PLIN3 was expressed in low levels during the earliest stages of development, slightly upregulated at the MO stage (P < 0.05), and greatly increased its expression at the BL stage (15-fold; P < 0.001). PLIN3 was comparatively more expressed than PLIN2 during embryo culture in most stages analyzed (P < 0.05), except in eight- to 16-cell embryos. These results indicate that PLIN2 might be involved in the maintenance of lipid stocks necessary to support embryo development after fertilization of IVM oocytes. Also, we hypothesize that PLIN3 is the main PAT protein responsible for stabilization of LD formed in consequence of the acute lipid load seen during embryo development. We confirmed the presence of both PLIN2 and PLIN3 proteins in BL at Day 7 using immunocytochemistry: these PAT proteins colocalized with LD stained with BODIPY. PLIN3 seemed to be more ubiquitously spread out in the cytoplasm than PLIN2, consistent with the pattern seen in adipocytes. These findings suggest that both elderly (bigger) and newly formed (smaller) LD, positive for PLIN2 and PLIN3 respectively, coexist in blastocysts. To our knowledge this is the first report showing that transcripts of the PAT family are present in cattle oocytes and embryos.

Derivation of sperm from xenografted testis cells and tissues of the peccary (Tayassu tajacu).

Because the collared peccary (Tayassu tajacu) has a peculiar Leydig cell cytoarchitecture, this species represents a unique mammalian model for investigating testis function. Taking advantage of the well-established and very useful testis xenograft technique, in the present study, testis tissue and testis cell suspensions from immature collared peccaries (n=4; 3 months old) were xenografted in SCID mice (n=48) and evaluated at 2, 4, 6, and 8 months after grafting. Complete spermatogenesis was observed at 6 and 8 months after testis tissue xenografting. However, probably due to de novo testis morphogenesis and low androgen secretion, functionally evaluated by the seminal vesicle weight, a delay in spermatogenesis progression was observed in the testis cell suspension xenografts, with the production of fertile sperm only at 8 months after grafting. Importantly, demonstrating that the peculiar testicular cytoarchitecture of the collared peccary is intrinsically programmed, the unique Leydig cell arrangement observed in this species was re-established after de novo testis morphogenesis. The sperm collected from the xenografts resulted in diploid embryos that expressed the paternally imprinted gene NNAT after ICSI. The present study is the first to demonstrate complete spermatogenesis with the production of fertile sperm from testis cell suspension xenografts in a wild mammalian species. Therefore, due to its unique testicular cytoarchitecture, xenograft techniques, particularly testis cell suspensions, may represent a new and very promising approach to evaluate testis morphogenesis and to investigate spermatogonial stem cell physiology and niche in the collared peccary.

Effect of triiodothyronine on developmental competence of bovine oocytes

Developmental competence of in vitro-matured bovine oocytes is a limiting factor in production of embryos in vitro. Several studies have suggested a potential positive effect of thyroid hormones on cultured oocytes and/or their supporting cells. Therefore, the aim of the present study was to ascertain whether medium supplementation with triiodothyronine (T3) improved subsequent developmental competence of in vitro-matured bovine oocytes. For this purpose, we first documented (using reverse transcription PCR) that whereas bovine cumulus cells expressed both thyroid hormone receptor (TR)-α and TRβ, immature bovine oocytes expressed TRα only. Thereafter, to test the effects of TH on developmental competence, abattoir-derived oocytes were matured in vitro in a medium containing 0, 25, 50, or 100 nM T3 and subjected to in vitro fertilization. Embryo quality was evaluated by assessing cleavage and blastocyst rates, morphological quality, development kinetics, and total cell number on Day 8 of culture. Notably, addition of 50 or 100 nM T3 to the in vitro maturation medium increased (P < 0.05) the rate of hatched blastocysts on the eighth day of culture, as compared with other groups (62.4 ± 11.7, 53.1 ± 16.3, and 32.4 ± 5.3, respectively). Next, the relative expression levels of genes related to embryo quality POU-domain transcription factor (POU5F1) and glucose transporter-1 (GLUT 1) were compared between in vivo- and in vitro-produced blastocysts. On the basis of the previous experiments, IVP embryos originating from oocytes that were matured in vitro in the presence or absence of 50 nM T3 were evaluated. The treatment had no effect (P > 0.05) on gene expression. We concluded that supplementation of bovine oocyte in vitro maturation medium with T3 may have a beneficial effect on the kinetics of embryo development.

Characterization of folliculogenesis and the occurrence of apoptosis in the development of the bovine fetal ovary.

The aim of this research was to perform in situ quantification, morphometry evaluation, and apoptosis analysis of ovarian follicular wall cells in mechanically isolated follicles obtained from ovaries of bovine fetuses (Bos taurus indicus) between 3 and 9 months of age. Apoptosis was evaluated using the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay. The number of isolated follicles increased from 3 months onward (102.5 ± 141.1, mean ± SEM), peaked at 6 months (12855.0 ± 9030.1), and then decreased by 7 months (3208.7 ± 3249.5), consistent with atresia occurring at these stages. Follicular density was greatest at 4 months, consistent with a sudden boost in follicular activity independent of a corresponding increase in ovarian size. Antral follicles were first observed at 5 months. As fetal age increased, there was a tendency for the percentage of primordial and primary follicles to decrease, and the percentage of secondary follicles to increase. However, the high variability (P < 0.05) for all follicle populations up to 5 months of age precluded further interpretation of these results. Oocyte diameter increased from the primordial (23.6 ± 4.4 μm) to the secondary follicular stages (38.0 ± 14.9 μm). Apoptosis was observed in ovaries from all fetal ages analyzed. We concluded that preantral follicles could be isolated from bovine fetuses by 3 months of age, with apoptosis affecting ovarian follicular dynamics throughout fetal life.

Addition of L-arginine to the fertilization medium enhances subsequent bovine embryo development rates

Although L-Arginine (ARG) has been reported as a promising bovine sperm capacitation agent, its effects on embryo development are still poorly understood. Herein, we compared the effects of ARG and/or heparin (HEP) addition to the fertilization medium for bovine oocytes on sperm capacitation and embryo development. We chose 10 mM ARG based on blastocyst development rates in a titration experiment. Addition of ARG and/or HEP to the fertilization medium resulted in similar rates of blastocyst development (P > 0.05). However, when ARG, but not HEP, was combined with a nitric oxide (NO) synthase inhibitor (N-Nitro-L-ARG-methyl ester, 10 mM) blastocyst development was decreased (P < 0.05). To assess the effects on capacitation, bovine sperm were incubated for 0, 3, and 6 hours in fertilization medium containing ARG and/or HEP and/or N-Nitro-L-ARG-methyl esterand acrosomal exocytosis rates were evaluated using fluorescein isothiocyanate conjugated Pisum sativum lectin (FITC-PSA) staining and flow cytometry. With HEP, acrosomal exocytosis rates were highest by 3 hours of incubation; however, by 6 hours, rates were similar for HEP and/or ARG (P > 0.05) and higher than those in control media (P < 0.05). Although both ARG and HEP increased sperm NO production (P < 0.05), combination with L-NAME only precluded acrosomal exocytosis when ARG added alone in the medium (P > 0.05). These results suggest that although both ARG and HEP supported sperm capacitation, only the effects of the former were driven via NO production. Moreover, ARG was also as effective as HEP at improving blastocyst development rates. Therefore, ARG may be used as a low-cost alternative sperm capacitation agent for bovine in vitro embryo production.

Systemic and local anti-Mullerian hormone reflects differences in the reproduction potential of Zebu and European type cattle

This study was conducted to evaluate plasma anti-Mullerian hormone (Pl AMH), follicular fluid AMH (FF AMH) and granulosa cell AMH transcript (GC AMH) levels and their relationships with reproductive parameters in two cattle subspecies, Bos taurus indicus (Zebu), and Bos taurus taurus (European type cattle). Two-dimensional ultrasound examination and serum collection were performed on Zebu, European type and crossbreed cows to determine antral follicle count (AFC), ovary diameter (OD) and Pl AMH concentration. Slaughterhouse ovaries for Zebu and European type cattle were collected to determine FF AMH concentrations, GC AMH RNA levels, AFC, oocyte number, cleavage and blastocyst rate. Additionally GC AMH receptor 2 (AMHR2) RNA level was measured for European type cattle. Relationship between AMH and reproductive parameters was found to be significantly greater in Zebu compared to European cattle. Average Pl AMH mean ± SE for Zebu and European cattle was 0.77 ± 0.09 and 0.33 ± 0.24 ng/ml respectively (p = 0.01), whereas average antral FF AMH mean ± SE for Zebu and European cattle was 4934.3 ± 568.5 and 2977.9 ± 214.1 ng/ml respectively (p < 0.05). This is the first published report of FF and GC AMH in Zebu cattle. Levels of GC AMHR2 RNA in European cattle were correlated to oocyte number (p = 0.01). Crossbred animals were found more similar to their maternal Zebu counterparts with respect to their Pl AMH to AFC and OD relationships. These results demonstrate that AMH reflects differences between reproduction potential of the two cattle subspecies therefore can potentially be used as a reproductive marker. Furthermore these results reinforce the importance of separately considering the genetic backgrounds of animals when collecting or interpreting bovine AMH data for reproductive performance.

Fetal sex alters maternal anti-Mullerian hormone during pregnancy in cattle

Anti-Mullerian hormone (AMH) is expressed by both male and female fetuses during mammalian development, with males expressing AMH earlier and at significantly higher concentration. The aim of the current study was to explore the potential impact of pregnancy and fetal sex on maternal AMH and to determine if plasma (Pl) AMH or placenta intercotyledonary membrane and cotyledonary AMH receptor 2 (AMHR2) mRNA expression differ in pregnant cows carrying male vs. female fetuses. AMH levels in blood were measured using a bovine optimized ELISA kit. Cows pregnant with a male fetus were observed to have a significantly greater difference in Pl AMH between day 35 and 135 of gestation. Average fetal AMH level between 54 and 220days of gestation was also observed to be significantly higher in male vs. female fetuses. Intercotyledonary membranes and cotyledons were found to express AMHR2 between days 38 and 80 of gestation at similar levels in both fetal sexes. These findings support the hypothesis that fetal sex alters maternal Pl AMH during pregnancy in cattle.

Increasing of blastocyst rate and gene expression in co-culture of bovine embryos with adult adipose tissue-derived mesenchymal stem cells

PurposeDespite advances in the composition of defined embryo culture media, co-culture with somatic cells is still used for bovine in vitro embryo production (IVEP) in many laboratories worldwide. Granulosa cells are most often used for this purpose, although recent work suggests that co-culture with stem cells of adult or embryonic origin or their derived biomaterials may improve mouse, cattle, and pig embryo development.Materials and methodsIn experiment 1, in vitro produced bovine embryos were co-cultured in the presence of two concentrations of bovine adipose tissue-derived mesenchymal cells (b-ATMSCs; 103 and 104 cells/mL), in b-ATMSC preconditioned medium (SOF-Cond), or SOF alone (control). In experiment 2, co-culture with 104 b-ATMSCs/mL was compared to the traditional granulosa cell co-culture system (Gran).ResultsIn experiment 1, co-culture with 104 b-ATMSCs/mL improved blastocyst rates in comparison to conditioned and control media (p < 0.05). Despite that it did not show difference with 103 b-ATMSCs/mL (p = 0.051), group 104 b-ATMSCs/mL yielded higher results of blastocyst production. In experiment 2, when compared to group Gran, co-culture with 104 b-ATMSCs/mL improved not only blastocyst rates but also quality as assessed by increased total cell numbers and mRNA expression levels for POU5F1 and G6PDH (p < 0.05).ConclusionsCo-culture of bovine embryos with b-ATMSCs was more beneficial than the traditional co-culture system with granulosa cells. We speculate that the microenvironmental modulatory potential of MSCs, by means of soluble substances and exosome secretions, could be responsible for the positive effects observed. Further experiments must be done to evaluate if this beneficial effect in vitro also translates to an increase in offspring following embryo transfer. Moreover, this study provides an interesting platform to study the basic requirements during preimplantation embryo development, which, in turn, may aid the improvement of embryo culture protocols in bovine and other species.