Evidence for autocrine or paracrine roles of alpha2-macroglobulin in regulation of estradiol production by granulosa cells and development of dominant follicles

Expression and characterization of the serum proteome from yak induced into estrus by improved nutrition

Regulation of estrus plays a crucial role in the livestock industry. It is reported that providing better nutrition can induce early estrus in animals. However, little is known about the major endocrine and physiological mechanisms that could enhance estrus in anestrus animals. Hence in the current research two different groups of yaks, non-breeding season (February-June, NBS) estrus yaks as the experiment group and breeding season (July-September, BS) estrus animals as the control group were compared using the isobaric tags for relative and absolute quantitation (iTRAQ) technique. Study displayed that cold season supplementation significantly improved growth performance, serum biochemical indicators and reproductive hormone concentrations in yaks. We also identified 25 differentially expressed proteins in yak serum using iTRAQ proteomics. Go and KEGG analysis indicated that calcium signaling pathway and beta-alanine metabolism may be candidate pathways for seasonal estrus induced by nutrition. Differential protein expression was validated using parallel reaction monitoring (PRM). The results of this study initially identified A2M, IGF2, A1BG and APOA1 as candidate proteins for seasonal estrus induced by nutrition. Altogether, In conclusion, our results show that providing additional nutrients in the cold season can improve yak productivity and reproductive efficiency, and provide a new reference.

Successful reversal of ovarian hyperstimulation syndrome in a mouse model by rapamycin, an mTOR pathway inhibitor

Ovarian hyperstimulation syndrome (OHSS) is a potentially life-threatening, iatrogenic complication of ovarian stimulation in assisted reproduction technology. This complex syndrome is characterised by enlarged ovaries with multiple corpora luteum, elevated sex steroid hormones in serum and increased capillary permeability. Until now, the pathogenesis of OHSS remains obscure, and no absolute strategy can fully prevent OHSS without any side effect on ovulation and clinical pregnancy. Using cultured human or mouse granulosa cells, our study revealed the time-dependent activation of the mTOR signaling pathway after human chorionic gonadotropin (hCG) treatment. The involvement of the mTOR signaling pathway was also observed in the development of OHSS in a mouse model. Selectively inhibiting mTOR signals by only two injections of rapamycin (2 mg/kg body weight), before or just after hCG treatment, significantly reduced vascular leakage and the severity of OHSS symptoms. Although ovarian angiogenesis was significantly inhibited, rapamycin could not decrease the elevated levels of vascular endothelial growth factor, IL-6 and IL-11 in OHSS ovaries. Further study showed the functional roles of the mTOR signaling pathway in the hyperstimulation-induced ovarian extracellular matrix remodeling as the expression of α2M, a broad proteolytic inhibitor in both ovary and serum, was dramatically decreased after rapamycin treatment. Since a single injection of rapamycin during superovulation had no side effects on ovulation and early embryonic development, we propose rapamycin may be a good candidate to lower and prevent the risk of OHSS in the future.

Estrogen Promotes Mandibular Condylar Fibrocartilage Chondrogenesis and Inhibits Degeneration via Estrogen Receptor Alpha in Female Mice

Temporomandibular joint degenerative disease (TMJ-DD) is a chronic form of TMJ disorder that specifically afflicts people over the age of 40 and targets women at a higher rate than men. Prevalence of TMJ-DD in this population suggests that estrogen loss plays a role in the disease pathogenesis. Thus, the goal of the present study was to determine the role of estrogen on chondrogenesis and homeostasis via estrogen receptor alpha (ERα) during growth and maturity of the joint. Young and mature WT and ERαKO female mice were subjected to ovariectomy procedures and then given placebo or estradiol treatment. The effect of estrogen via ERα on fibrocartilage morphology, matrix production, and protease activity was assessed. In the young mice, estrogen via ERα promoted mandibular condylar fibrocartilage chondrogenesis partly by inhibiting the canonical Wnt signaling pathway through upregulation of sclerostin (Sost). In the mature mice, protease activity was partly inhibited with estrogen treatment via the upregulation and activity of protease inhibitor 15 (Pi15) and alpha-2-macroglobulin (A2m). The results from this work provide a mechanistic understanding of estradiol on TMJ growth and homeostasis and can be utilized for development of therapeutic targets to promote regeneration and inhibit degeneration of the mandibular condylar fibrocartilage.

Hampered cumulus expansion of porcine cumulus-oocyte complexes by excessive presence of alpha2 -macroglobulin is likely mediated via inhibition of zinc-dependent metalloproteases

In vitro maturation (IVM) in serum causes hampered expansion of porcine cumulus-oocyte complexes (COCs) due to excessive alpha₂ -macroglobulin (A2M). This study investigated two hypotheses that could explain the effect of A2M: (i) binding of epidermal growth factor (EGF) to A2M, followed by its decreased availability; and (ii) inhibition of zinc-dependent metalloproteases. Cumulus expansion was evaluated based on the diameter of the COCs, the proportion of COCs participating in a floating cloud and the proportion of COCs with loss of cumulus cells. The first hypothesis of decreased EGF availability was tested by increasing the EGF concentration (20 and 50 ng/mL vs. 10 ng/mL), but was not confirmed because cumulus expansion did not improve. To verify the second hypothesis of inhibited zinc-dependent metalloproteases, the effect of tissue inhibitor of metalloproteases-3 (TIMP-3) on cumulus expansion during IVM with and without A2M was investigated. To immuno-neutralize A2M, serum was pre-incubated with A2M antibodies. Impaired cumulus expansion because of TIMP-3 could only be observed during IVM in 10% of serum with A2M antibodies. No effect of TIMP-3 was observed in medium without A2M antibodies. These results indicate that A2M and TIMP-3 share a common target, a zinc-dependent metalloprotease. Future research is directed toward the identification of the protease involved.

De novo Assembly and Analysis of the Chilean Pencil Catfish Trichomycterus areolatus Transcriptome

Trichomycterus areolatus is an endemic species of pencil catfish that inhabits the riffles and rapids of many freshwater ecosystems of Chile. Despite its unique adaptation to Chile's high gradient watersheds and therefore potential application in the investigation of ecosystem integrity and environmental contamination, relatively little is known regarding the molecular biology of this environmental sentinel. Here, we detail the assembly of the Trichomycterus areolatus transcriptome, a molecular resource for the study of this organism and its molecular response to the environment. RNA-Seq reads were obtained by next-generation sequencing with an Illumina® platform and processed using PRINSEQ. The transcriptome assembly was performed using TRINITY assembler. Transcriptome validation was performed by functional characterization with KOG, KEGG, and GO analyses. Additionally, differential expression analysis highlights sex-specific expression patterns, and a list of endocrine and oxidative stress related transcripts are included.

Interaction between thyroglobulin and ADAMTS16 in premature ovarian failure

Objective

The aim of the present study was to examine whether interactions between polymorphisms in the thyroglobulin and ADAM metallopeptidase with thrombospondin type 1 motif, 16 (ADAMTS16) genes are associated with the development of premature ovarian failure (POF).

Methods

A total of 75 patients with POF and 196 controls were involved in this study. We used a GoldenGate assay to genotype single nucleotide polymorphisms (SNPs). Logistic regression analysis was performed to identify POF-associated polymorphisms and synergistic interactions between polymorphisms in the thyroglobulin and ADAMTS16 genes.

Results

Single gene analyses using logistic regression analysis showed no significant association between polymorphisms in the two genes and POF. In the results from interaction analyses, we found seven synergistic interactions between the polymorphisms in thyroglobulin and ADAMTS16, although there was no combination showing p-values lower than the significant threshold using the Bonferroni correction. When the AG genotype was present at the rs853326 missense SNP, the A and G alleles at the tagging SNPs rs16875268 and rs13168665 showed significant interactions (odds ratios=5.318 and 16.2 respectively; 95% confidence intervals, 1.64-17.28 and 2.08-126.4; p=0.0054 and 0.0079).

Conclusion

Synergistic interactions between polymorphisms in the thyroglobulin and ADAMTS16 genes were associated with an increased risk of POF development in Korean women.

Midkine and cytoplasmic maturation of mammalian oocytes in the context of ovarian follicle physiology

Midkine (MK) was originally characterized as a member of a distinct family of neurotrophic factors functioning in the CNS. However, it was later discovered that MK is abundantly expressed in ovarian follicles. Since then, the physiological roles of this molecule in the ovary have been steadily investigated. During the in vitro maturation (IVM) of oocytes MK was shown to promote the cytoplasmic maturation of oocytes, as indicated by post-fertilization development. This effect of MK could be mediated via its pro-survival (anti-apoptotic) effects on the cumulus-granulosa cells that surround oocytes. The oocyte competence-promoting effects of MK are discussed in the context of the recently discovered involvement of MK in the full maturation of ovarian follicles. MK was at the frontline of a new paradigm for neurotrophic factors as oocytetrophic factors. MK may promote the developmental competence of oocytes via common signalling molecules with the other neurotrophic factor(s). Alternatively or concomitantly, MK may also interact with various transmembrane molecules on cumulus-granulosa cells, which are important for ovarian follicle growth, dominance and differentiation, and act as a unique pro-survival factor in ovarian follicles, such that MK promotes oocyte competence. MK, along with other ovarian neurotrophic factors, may contribute to the optimization of the IVM system.

LINKED ARTICLES

This article is part of a themed section on Midkine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-4.

Comparative proteome analysis of porcine follicular fluid and serum reveals that excessive alpha(2)-macroglobulin in serum hampers successful expansion of cumulus-oocyte complexes

Porcine follicular fluid (pFF) constitutes the micro-environment of the maturing oocyte. Although pFF is a transudate of serum, in pigs, it is superior to serum in promoting in vitro expansion of the cumulus cells, a specialized cell population surrounding the oocyte. A comparative proteome analysis of autologous serum and pFF was performed to investigate proteins involved in successful cumulus expansion of porcine oocytes. iTRAQ labeling followed by 2-D LC ESI-Q-TOF MS/MS revealed 63 proteins common to both fluids of which the abundance of 13 proteins was significantly different (p<0.05). Seven proteins were more concentrated in serum whereas six proteins were more abundant in pFF. To investigate the importance of these proteins, the cumulus matrices of COCs were collected after in vitro maturation in media supplemented with either of both biologically fluids and then subjected to 2-D PAGE analysis. alpha(2)-Macroglobulin and CH4 and secrete domains of swine IgM, which were both less abundant in pFF, were absent from cumulus matrix extracts after in vitro maturation in pFF. Although both proteins were incorporated in the matrices of cumulus-oocyte complexes matured in serum, depletion of alpha(2)-macroglobulin from serum could significantly compensate for the impaired cumulus expansion of oocytes matured in serum.

New insights into molecular pathways associated with flatfish ovarian development and atresia revealed by transcriptional analysis

Background

The Senegalese sole (Solea senegalensis) is a marine flatfish of increasing commercial interest. However, the reproduction of this species in captivity is not yet controlled mainly because of the poor knowledge on its reproductive physiology, as it occurs for other non-salmonid marine teleosts that exhibit group-synchronous ovarian follicle development. In order to investigate intra-ovarian molecular mechanisms in Senegalese sole, the aim of the present study was to identify differentially expressed genes in the ovary during oocyte growth (vitellogenesis), maturation and ovarian follicle atresia using a recently developed oligonucleotide microarray.

Results

Microarray analysis led to the identification of 118 differentially expressed transcripts, of which 20 and 8 were monitored by real-time PCR and in situ hybridization, respectively. During vitellogenesis, many up-regulated ovarian transcripts had putative mitochondrial function/location suggesting high energy production (NADH dehydrogenase subunits, cytochromes) and increased antioxidant protection (selenoprotein W2a), whereas other regulated transcripts were related to cytoskeleton and zona radiata organization (zona glycoprotein 3, alpha and beta actin, keratin 8), intracellular signalling pathways (heat shock protein 90, Ras homolog member G), cell-to-cell and cell-to-matrix interactions (beta 1 integrin, thrombospondin 4b), and the maternal RNA pool (transducer of ERBB2 1a, neurexin 1a). Transcripts up-regulated in the ovary during oocyte maturation included ion transporters (Na⁺-K⁺-ATPase subunits), probably required for oocyte hydration, as well as a proteinase inhibitor (alpha-2-macroglobulin) and a vesicle calcium sensor protein (extended synaptotagmin-2-A). During follicular atresia, few transcripts were found to be up-regulated, but remarkably most of them were localized in follicular cells of atretic follicles, and they had inferred roles in lipid transport (apolipoprotein C-I), chemotaxis (leukocyte cell-derived chemotaxin 2,), angiogenesis (thrombospondin), and prevention of apoptosis (S100a10 calcium binding protein).

Conclusion

This study has identified a number of differentially expressed genes in the ovary that were not previously found to be regulated during ovarian development in marine fish. Specifically, we found evidence, for the first time in teleosts, of the activation of chemoattractant, angiogenic and antiapoptotic pathways in hypertrophied follicular cells at the onset of ovarian atresia.

Glial-derived neurotrophic factor promotes ovarian primordial follicle development and cell-cell interactions during folliculogenesis

Female fertility is determined in part by the size and development of the primordial follicle pool. The current study investigates the role of glial cell-line-derived neurotrophic factor (GDNF) in the regulation of primordial follicle development in the ovary. Ovaries from 4-day-old female rat pups were maintained in organ culture for 10 days in the absence (control) or presence of GDNF or kit ligand (KL)/stem cell factor. Ovaries treated with GDNF contained a significant increase in developing follicles, similar to that observed with KL treatment previously shown to promote follicle development. The actions of GDNF on the ovarian transcriptome were investigated with a microarray analysis. Immunohistochemical studies demonstrated that GDNF is localized to oocyte cytoplasm in follicles of all developmental stages, as well as to cumulus granulosa cells and theca cells in antral follicles. GDNF receptor alpha1 (GFRalpha1) staining was localized to oocyte cytoplasm of primordial and primary follicles, and at reduced levels in the oocytes of antral follicles. GFRalpha1 was present in mural granulosa cells of antral follicles, theca cells, and ovarian surface epithelium. The localization studies were confirmed with molecular analysis. Microarray analysis was used to identify changes in the ovarian transcriptome and further elucidate the signaling network regulating early follicle development. Observations indicate that GDNF promotes primordial follicle development and mediates autocrine and paracrine cell-cell interactions required during folliculogenesis. In contrast to the testis, ovarian GDNF is predominantly produced by germ cells (oocytes) rather than somatic cells.

Follicle selection in cattle and horses: role of intrafollicular factors

The eminent event in follicle selection during a follicular wave in monovular species is diameter deviation, wherein one follicle continues to grow (developing dominant) and other follicles (subordinates) begin to regress. In cattle, the IGF system, oestradiol and LH receptors are involved in the intrafollicular events initiating deviation as indicated by the following: (1) concentrations of free IGF-I and oestradiol in the follicular fluid and number of LH receptors in the follicular wall increase more dramatically in the future dominant follicle than in the future subordinate follicles before the beginning of deviation and (2) ablation of the largest follicle (LF) or injection of recombinant human IGF (rhIGF)-I into the second LF at the expected beginning of deviation increases the concentrations of oestradiol in second LF before the expected beginning of deviation between second LF and third LF. In horses, an increase in free IGF-I, oestradiol, inhibin-A and activin-A is greater in the future dominant follicle than in other follicles before the beginning of deviation. However, free IGF-I is the only one of these four factors needed for the initiation of deviation in horses as indicated by the following: (1) ablation of LF at the expected beginning of deviation increases the concentrations of free IGF-I in second LF before the beginning of deviation between second LF and third LF but does not increase the other factors; (2) injection of rhIGF-I into second LF at the expected beginning of deviation causes second LF to continue to grow and become a codominant follicle and (3) injection of IGF-binding protein-3 into LF at the expected beginning of deviation causes LF to regress and second LF to become dominant. Thus, the dramatic changes in the IGF system in LF compared to other follicles before the beginning of deviation play a crucial role in the events that lead to the beginning of diameter deviation in both cattle and horses. Oestradiol and LH receptors also play a role in cattle. These intrafollicular events prepare the selected follicle for the decreasing availability of FSH and increasing availability of LH. The other follicles of the wave have the same future capability but do not have adequate time to attain a similar preparatory stage.

FSH stimulates the expression of the ADAMTS-16 protease in mature human ovarian follicles

We report the characterization of full-length human ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs)-16, a novel member of the disintegrin and metalloproteinase with thrombospondin motifs (hence ADAMTS) family. ADAMTS-16 is highly expressed both in the kidney and in the ovary, where it is predominantly expressed in the parietal granulosa cells of pre-ovulatory follicles but only slightly expressed in cells of the cumulus oophorus. In fully differentiated luteinizing granulosa cells, follicle-stimulating hormone and forskolin induces expression of ADAMTS-16, suggesting that it is regulated via the cAMP pathway. Luteinizing hormone had a minor effect on the expression of ADAMTS-16. ADAMTS-16 is capable of cleaving alpha2-macroglobulin (MG), a common substrate for proteases, which is present at high concentrations in the follicular fluid of ovarian follicles. These studies provide the first evidence that ADAMTS-16 is an active protease and suggest a physiological role of ADAMTS-16 in ovarian follicles, at least during the pre-ovulatory phase.

Evidence of a local negative role for cocaine and amphetamine regulated transcript (CART), inhibins and low molecular weight insulin like growth factor binding proteins in regulation of granulosa cell estradiol production during follicular waves in cattle

The ability of ovarian follicles to produce large amounts of estradiol is a hallmark of follicle health status. Estradiol producing capacity is lost in ovarian follicles before morphological signs of atresia. A prominent wave like pattern of growth of antral follicles is characteristic of monotocous species such as cattle, horses and humans. While our knowledge of the role of pituitary gonadotropins in support of antral follicle growth and development is well established, the intrinsic factors that suppress estradiol production and may help promote atresia during follicular waves are not well understood. Numerous growth factors and cytokines have been reported to suppress granulosa cell estradiol production in vitro, but the association of expression of many such factors in vivo with follicle health status and their physiological significance are not clear. The purpose of this review is to discuss the in vivo and in vitro evidence supporting a local physiological role for cocaine and amphetamine regulated transcript, inhibins and low molecular weight insulin like growth factor binding proteins in negative regulation of granulosa cell estradiol production, with emphasis on evidence from the bovine model system.

alpha2-Macroglobulin in the marine fish Sparus aurata

The alpha2-macroglobulin proteinase inhibitors (alpha2Ms) are a family of plasma proteins with the unique ability to inhibit a broad spectrum of proteinases, but are also known as binding proteins for many growth factors and cytokines, including growth hormone and members of the transforming growth factor-beta superfamily. A partial cDNA (475 amino acids) encoding the C-terminus of alpha2M was cloned from the liver of the marine teleostean fish Sparus aurata. The deduced amino acid sequence of the cloned fragment showed 58-60% similarity to carp alpha2Ms. Northern blot analysis of hepatic alpha2M revealed a transcript of about 5 kb. A transcript of a similar size was detected in 1-day larvae. Steady state levels of alpha2M in larvae increased gradually on subsequent days post-hatching. alpha2M expression in embryos was determined by RT-PCR and started in embryos aged 8 h post-fertilization, but not earlier. RT-PCR of muscle RNA detected alpha2M also in fish muscle, albeit with a lower expression than in the liver. Immunoreactive-alpha2M was found in yolk syncytial layer of 3-day larvae and in livers from larvae and adults. Immunoreactive-alpha2M was also identified in soluble total proteins from young larvae with a pattern resembling that of plasma. These data demonstrate that the alpha2M gene is expressed early in fish development. Moreover, in addition to its major expression in liver, alpha2M is expressed also in fish muscle.