Physico-chemical properties of pregnant mare serum gonadotropin

Nanotechnology and Reproductive Management of Farm Animals: Challenges and Advances

Reproductive efficiency of farm animals has central consequences on productivity and profitability of livestock farming systems. Optimal reproductive management is based on applying different strategies, including biological, hormonal, nutritional strategies, as well as reproductive disease control. These strategies should not only guarantee sufficient reproductive outcomes but should also comply with practical and ethical aspects. For example, the efficiency of the biological- and hormonal-based reproductive strategies is mainly related to several biological factors and physiological status of animals, and of nutritional strategies, additional factors, such as digestion and absorption, can contribute. In addition, the management of reproductive-related diseases is challenged by the concerns regarding the intensive use of antibiotics and the development of antimicrobial resistant strains. The emergence of nanotechnology applications in livestock farming systems may present innovative and new solutions for overcoming reproductive management challenges. Many drugs (hormones and antibiotics), biological molecules, and nutrients can acquire novel physicochemical properties using nanotechnology; the main ones are improved bioavailability, higher cellular uptake, controlled sustained release, and lower toxicity compared with ordinary forms. In this review, we illustrate advances in the most common reproductive management strategies by applying nanotechnology, considering the current challenges of each strategy.

Activin A and equine chorionic gonadotropin recover reproductive dysfunction induced by neonatal exposure to an estrogenic endocrine disruptor in adult male mice

We aimed to elucidate the mechanism of action of estrogenic endocrine disruptors and the rescue of reproductive function, particularly the responsiveness of testes to eCG and/or activin A (ACT) after establishing reproductive disorders. Newborn male mice (n = 29) were randomly divided into an untreated group and three treatment groups that received diethylstilbestrol (DES; 100 mug per animal) subcutaneously on Postnatal Day 3 to establish reproductive disorders and daily treatment with PBS (controls: DES + PBS), eCG (eCG group: DES + eCG), or eCG + ACT (eCG + ACT group: DES + eCG + ACT) at 6-8 wk of age prior to mating. After treatment, the controls showed diminished Leydig cells in the testes and thin germ cell layers containing pyknotic germ cells and multinucleated cells. In the eCG and eCG + ACT groups, spermatids and Leydig cells increased markedly. The immunoexpression of androgen receptors in the eCG group and steroidogenic acute regulatory (STAR) protein in the eCG and eCG + ACT groups recovered to approximately the levels in the untreated group; plasma LH and testosterone levels also increased relative to those in the controls. In addition, the cell proliferation index, which is estimated from 5-bromo-2'-deoxyuridine immunoexpression in spermatogonia, increased significantly under eCG treatment, and even more with eCG + ACT. However, the numbers of germ and Leydig cells decreased at 12 wk of age. Thus, ACT and eCG help the testes to recover from the dysfunction induced by neonatal DES administration. Furthermore, the permanent male reproductive disorder induced by neonatal exposure to estrogenic agents may be more likely to result from dysfunction of the hypothalamic-pituitary axis than from dysfunction of the lower reproductive organs.

Antiequine chorionic gonadotropin (eCG) antibodies generated in goats treated with eCG for the induction of ovulation modulate the luteinizing hormone and follicle-stimulating hormone bioactivities of eCG differently

In dairy goats, treatments associating a progestogen and the equine chorionic gonadotropin (eCG) are the easiest way to induce and synchronize estrus and ovulation and to permit artificial insemination (AI) and/or out of season breeding. From the first treatment, the injection of eCG induces, in some females, the production of anti-eCG antibodies (Abs) that will interfere with the effectiveness of subsequent treatments. These anti-eCG Abs delay the preovulatory LH surge and the ovulation time, leading to poor fertility of the treated females. In this study, by in vitro bioassays, we show that anti-eCG Abs can positively or negatively modulate the LH and/or FSH bioactivities of eCG. Moreover, the modulation level of eCG bioactivity does not depend on the anti-eCG Ab affinity for eCG, as shown by surface plasmon resonance technology. The specificity of anti-eCG Abs tested by competitive ELISA highlighted the importance of a glycan environment in the recognition mechanism, especially the sialic acids specific to eCG. The different effects of anti-eCG Abs on eCG bioactivities could be explained by two hypotheses. First, steric hindrance preventing the interaction of eCG with its receptors would explain the inhibitory effect of some anti-eCG Abs; second, a conformational change in eCG by anti-eCG Abs could induce inhibition or potentiation of eCG bioactivities. It is significant that these modulations of eCG bioactivities by anti-eCG Abs impact mainly on the FSH bioactivity of eCG, which is essential for ovarian stimulation and subsequent fertility after treatment and AI, and to a lesser extent on LH bioactivity.

Expression of a single betaalpha chain protein of equine LH/CG in milk of transgenic rabbits and its biological activity

Equine chorionic gonadotropin (eCG) is a heavily glycosylated glycoprotein composed of non-covalently linked alpha- and beta-subunits. eCG possesses the particularity to bind to both LH and FSH receptors in species other than horses and to have a prolonged plasma half-life. All these properties make it of utmost interest for livestock fertilization program. Up to now, the only source of eCG is the serum of pregnant mare. Rabbit mammary gland is considered as a system able to produce recombinant glycoproteins in sufficient quantity for pharmaceutical use. Here we described the production of a recombinant single betaalpha chain of eLH/CG in the milk of transgenic rabbit. The construction of a single-chain permits to by-pass the problem of association-dissociation of the subunits. This recombinant hormone is greatly expressed (21.7 mg/l) and presents similar in vitro LH and FSH bioactivities. However, betaalphaeLH/CG shows an extremely rapid clearance (approximately 10 min), which could explain the absence of in vivo biological activity. So the rabbit mammary gland is not appropriate for the production of a recombinant active eLH/CG.

Humoral immune response to equine chorionic gonadotropin in ewes: association with major histocompatibility complex and interference with subsequent fertility

In dairy ewes, the use of eCG as a convenient hormone for the induction of ovulation is necessary for out-of-season breeding and artificial insemination (AI). In this report we show the presence of anti-eCG antibodies in plasma of treated ewes. The major histocompatibility complex (MHC) was involved in the individual variability of the humoral immune responses to eCG. We found significant associations between the anti-eCG response phenotype and some MHC class II alleles. The low immune response phenotype was associated with one MHC class II allele only in Lacaune ewes, and the high immune response phenotype was associated with one MHC class II allele both in Manech and in Lacaune ewes. In herds, the impact of residual anti-eCG antibodies on subsequent fertility after AI seems minimal because of an indirect elimination of high-responder ewes from AI breeding. Therefore, the true magnitude of the association between residual anti-eCG antibody concentration and fertility has been underestimated. An additional experiment without any high-responder female elimination showed a significant correlation between high residual antibody concentrations and lower lambing rate after AI at a fixed time, possibly because of a delayed preovulatory LH surge. The results suggest that anti-eCG antibody concentration is one risk factor for infertility after AI.

The negative effect of repeated equine chorionic gonadotropin treatment on subsequent fertility in Alpine goats is due to a humoral immune response involving the major histocompatibility complex

In dairy goats, the use of eCG as a convenient hormone for the induction of ovulation is necessary for out-of-season breeding and artificial insemination. However, repeated eCG treatments are followed by decreased fertility in goats inseminated at a fixed time after treatment. In this report, we show the presence of anti-eCG antibodies in plasma of treated goats. A 500 IU eCG injection induces a humoral response, with variable concentrations of anti-eCG antibody being produced in individual goats. The analysis of successive anti-eCG immune responses over several years has demonstrated the existence of different populations of goats, defined as low, medium, and high responders. By the use of two caprine microsatellites located inside (OLADRB) and outside (BM1258) the major histocompatibility complex (MHC), a significant association (p < 0.05) between the anti-eCG antibody response and some MHC-DRB alleles was found. Goats with high antibody concentrations at the time of eCG injection (> 2.5 microg/ml) exhibited a much lower kidding rate than did other females (41.3% vs. 66.7%). Lower fertility of these goats, inseminated at a fixed time after eCG treatment, might be due to the observed delay in estrus occurrence and the preovulatory LH surge.

Topography of equine chorionic gonadotropin epitopes relative to the luteinizing hormone and follicle-stimulating hormone receptor interaction sites

In order to localize the epitopes of equine chorionic gonadotropin (eCG) involved in interaction with luteinizing hormone (LH) and follicle-stimulating hormone (FSH) receptors, we used 14 monoclonal anti-eCG antibodies (mAbs). Different effects of these mAbs on the bioactivities of eCG were observed in in vitro bioassays, but the effects of each mAb on the two bioactivities were similar for all but four mAbs. All mAbs were found to inhibit the binding of eCG to LH receptors except 3A3 mAb, in radioreceptor assay. Six mAbs, which were strong inhibitors of eCG binding to LH receptors and of both bioactivities, recognized the same area on the alpha subunit of eCG. All others, except 3A3, recognized epitopes close to the former, and close to each other. 3A3 mAb had a hyperstimulatory effect on FSH bioactivity, and was the only mAb that did not inhibit binding. It appeared to recognize a different epitopic area. These observations suggest that there is a main antigenic area on eCG, which corresponds to the interaction site of eCG with both receptors. It mostly involves the alpha subunit and to a lesser extent the beta subunit.

Immunochemical study of equine chorionic gonadotropin (eCG/PMSG): antigenic determinants on alpha- and beta-subunits

In the present study we have established an immunochemical mapping of equine Chorionic Gonadotropin (eCG/PMSG) using three monoclonal antibodies (mAbs), namely the antibodies ECG01, E10 and D7, raised against the native hormone. These antibodies do not bind to reduced, alkylated hormone, suggesting that they recognize discontinuous rather than continuous epitopes. We have also assessed the reactivity of mAbs towards human CG, and ovine, porcine, equine and bovine LH and FSH. The antigenic determinant recognized by ECG01 is localized on the alpha-subunit of equine gonadotropins and of human CG and LH. The epitopes recognized by E10 and D7 mAbs appear to be very similar and are present on the beta-subunit of eCG and of LHs from all species tested, except hLH, as well as on porcine and equine FSHs. Attempts to specify the amino-acid residues involved in these epitopes suggest that ECG01 mAb might preferentially bind to residues around position 70 whereas the region around disulfide bridges Cys-88-Cys-90 might be involved in the epitopes recognized by D7 and E10 mAbs. Topographical relationships of epitopes show that ECG01 mAb never binds to eCG simultaneously with either D7 or E10 mAbs. Furthermore, simultaneous binding of D7 and E10 mAbs on eCG could not be achieved. Thus, these three epitopes appear to be closely located on the surface of eCG. Finally, ECG01 mAb inhibits eCG binding to LH and FSH receptors, suggesting that its antigenic site is closely related to hormone-receptor interaction site(s).

Purification and characterization of luteinizing hormone from the dromedary (Camelus dromedarius)

Luteinizing hormone (LH) has been purified from 150 dromedary pituitaries and its partial physicochemical, biological and immunological characterization has been achieved. Purification of the hormone was monitored by a porcine LH radioreceptor assay (RRA). In this system, the final camLH preparation exhibited an activity 0.6-fold that of highly purified porcine LH. The acid half-dissociation of camLH at equilibrium was observed at pH 4.2. A homologous camLH RRA was developed using the testicular plasma membrane fraction from prepubertal camels and radioiodinated, highly-purified camLH. Pituitary and chorionic gonadotropins (CG) from several mammalian species were compared to camLH in this system. The equine gonadotropins eLH and eCG were shown to be 6 times less potent in the camel RRA than in the porcine RRA, whereas the LH from other species exhibited similar activities in both systems. This particularity of camel LH receptors offers a new tool for the study of structural features of gonatropin interactions with their receptors.

Study of the superactivity of equine follicle-stimulating hormone in in vitro stimulation of rat Sertoli cells

We have previously shown that equine follicle-stimulating hormone (FSH) stimulates plasminogen activator secretion in Sertoli cells at much lower concentrations than would be expected from its relative binding activity. We have introduced the term 'superactivity' to designate this particular behavior. In the present study, we show that equine FSH triggers a long-lasting (20 h) plasminogen activator secretion, whereas rat, porcine and ovine FSH as well as equine LH and equine choriogonadotropin (CG) provoke a short-term response (2.5 h). Moreover, equine FSH was also shown to be superactive in the stimulation of estradiol secretion and cyclic AMP production. This indicates that the step responsible for the long-term stimulation by equine FSH is not located beyond cAMP accumulation. Equine and porcine FSH were found to be equally stable during incubation with the cells demonstrating that equine FSH superactivity was not due to higher stability. Besides, phosphodiesterase inhibition led to a similar increase in the responses to both hormones. This rules out the possibility that equine FSH superactivity is due to less stimulation of phosphodiesterase activity. All these data strongly suggest that equine FSH exhibits superactivity in rat Sertoli cells by stimulating adenylate cyclase activity for a much longer period of time than do all other gonadotropins. The molecular mechanism of this outstanding behavior remains to be elucidated.

Direct demonstration of intrinsic follicle-stimulating hormone receptor-binding activity in acid-treated equine luteinizing hormone

After dissociating equine gonadotropins as a function of time at pH 3, we examined them by radioligand assay and sodium dodecyl sulfate polyacrylamide gel electrophoresis under nondissociating conditions (low, 0.1% SDS). Equine follicle-stimulating hormone (FSH) rapidly lost its receptor-binding activity, and low SDS-polyacrylamide gels demonstrated dissociation into subunits. Maximum dissociation occurred after 20-30 min of pH 3 incubation. Equine luteinizing hormone (LH), however, retained most biologic activity and was largely intact after 72 h of pH 3 incubation. Dose-response curves of acid-treated equine LH and FSH and intact equine LH and FSH were compared in five types of radioligand receptor assays. LH and FSH receptor-binding activities of equine LH were unaffected by pH 3. Equine LH showed 19- and 32-times more activity in the rat testis FSH assay than it did in chicken or horse FSH assays, respectively, directly demonstrating the intrinsic FSH receptor-binding activity of equine LH and the relative lack of specificity for these hormone preparations of the rat FSH receptor. Acid-treated 95% of its biologic activity in FSH assays. In LH assays, the slight (0.2%) activity of equine FSH was relatively unaffected by acid treatment, suggesting that contamination by equine LH accounts for this activity.