C-terminal peptide (hCTP) of human chorionic gonadotropin enhances in vivo biological activity of recombinant Japanese eel follicle-stimulating hormone and luteinizing hormone produced in FreeStyle 293-F cell lines

Development of a biotechnology process for the production of a novel hyperglycosylated long-acting recombinant bovine follicle-stimulating hormone

Follicle-stimulating hormone (FSH) is an important protein used for bovine ovarian hyperstimulation in multiple ovulation and embryo transfer technology (MOET). Several attempts to produce bovine FSH (bFSH) in recombinant systems have been reported, nonetheless, up to date, the most commonly used products are partially purified preparations derived from porcine or ovine (pFSH or oFSH) pituitaries. Here we describe the development of a biotechnology process to produce a novel, hyperglycosylated, long-acting recombinant bFSH (LA-rbFSH) by fusing copies of a highly O-glycosylated peptide. LA-rbFSH and a nonmodified version (rbFSH) were produced in suspension CHO cell cultures and purified by IMAC with high purity levels (>99%). LA-rbFSH presented a higher glycosylation degree and sialic acid content than rbFSH. It also demonstrated a notable improvement in pharmacokinetic properties after administration to rats, including a higher concentration in plasma and a significant (seven-fold) reduction in apparent clearance (CLapp). In addition, the in vivo specific bioactivity of LA-rbFSH in rats was 2.4-fold higher compared to rbFSH. These results postulate this new molecule as an attractive substitute for commercially available porcine pituitary-derived products.

Establishment of cell-lines stably expressing recombinant Japanese eel follicle-stimulating hormone and luteinizing hormone using CHO-DG44 cells: fully induced ovarian development at different modes

The gonadotropins (Gth), follicle-stimulating hormone (Fsh) and luteinizing hormone (Lh), play central roles in gametogenesis in vertebrates. However, available information on their differential actions in teleost, especially in vivo, is insufficient. In this study, we established stable CHO-DG44 cell lines expressing long-lasting recombinant Japanese eel Fsh and Lh with extra O-glycosylation sites (Fsh-hCTP and Lh-hCTP), which were produced in abundance. Immature female eels received weekly intraperitoneal injections of Gths. Fsh-hCTP induced the entire ovarian development by 8 weeks from the beginning of injection; thus, the ovaries of most fish were at the migratory nucleus stage while the same stage was observed in eels after 4 weeks in the Lh-hCTP-treated group. In contrast, all pretreated and saline-injected eels were in the pre-vitellogenic stage. Gonadosomatic indices in the Fsh-hCTP-treated group were significantly higher than those in the Lh-hCTP group at the migratory nucleus stage because of the significantly higher frequency of advanced ovarian follicles. Ovarian mRNA levels of genes related to E2 production (cyp11a1, cyp17a1, cyp19a1, hsd3b, fshr, and lhr) were measured using real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). All genes were induced by both Fsh-hCTP and Lh-hCTP, with a peak at either the mid- or late vitellogenic stages. Transcript abundance of cyp19a1 and fshr in the Lh-hCTP group were significantly higher than those in the Fsh-hCTP group, whereas no difference in the expression of other genes was observed between the groups. Fluctuations in serum levels of sex steroid hormones (estradiol-17β, 11-ketotestosterone, and testosterone) in female eels were comparable in the Fsh-hCTP and Lh-hCTP groups, thus increasing toward the maturational phase. Furthermore, the fecundity of the eels induced to mature by Fsh-hCTP was significantly higher than that induced by Lh-hCTP. These findings indicate that Fsh and Lh can induce ovarian development in distinctively different modes in the Japanese eel.

Anguillid Eels as a Model Species for Understanding Endocrinological Influences on the Onset of Spawning Migration of Fishes

Simple Summary

Endocrine regulation has been thought to play a major role in the onset of migration. Anguillid eels provide a good model for studying the onset mechanisms of migrations to breeding areas, because the process of the onset of migration occurs in inland waters. In this review, we summarize information about the silvering process in anguillid eels and the dynamics of mRNA expression of neurohormones and pituitary hormones, thyroid hormones, and sex steroids associated with the onset of the spawning migration. We also provide new results. Because 11-KT drastically increases during silvering, the role of 11-KT in the onset of spawning migration was discussed in detail.

Abstract

Anguillid eels are the iconic example of catadromous fishes, because of their long-distance offshore spawning migrations. They are also a good model for research on the onset mechanisms of migrations to breeding areas, because the migrations begin in inland waters. When eels transform from yellow eels to silver eels, it is called silvering. Silver eels show various synchronous external and internal changes during silvering, that include coloration changes, eye-size increases, and gonadal development, which appear to be pre-adaptations to the oceanic environment and for reproductive maturation. A strong gonadotropic axis activation occurs during silvering, whereas somatotropic and thyrotropic axes are not activated. Among various hormones, 11-ketotestosterone (11-KT) drastically increases during spawning migration onset. Gradual water temperature decreases simulating the autumn migratory season, inducing 11-KT increases. Administration of 11-KT appeared to cause changes related to silvering, such as early-stage oocyte growth and eye enlargement. Moreover, 11-KT may be an endogenous factor that elevates the migratory drive needed for the spawning migration onset. These findings suggested that water temperature decreases cause 11-KT to increase in autumn and this induces silvering and increases migratory drive. In addition, we newly report that 11-KT is associated with a corticotropin-releasing hormone that influences migratory behavior of salmonids. This evidence that 11-KT might be among the most important factors in the spawning migration onset of anguillid eels can help provide useful knowledge for understanding endocrinological mechanisms of the initiation of spawning migrations.

Production of recombinant Japanese eel (Anguilla japonica) growth hormones and their effects on early-stage larvae

Growth hormone (Gh) regulates somatic growth in fishes, particularly through the Gh - insulin-like growth factor-I (Igf-I) axis. In this study, recombinant Japanese eel Ghs with or without C-terminal peptides of human chorionic gonadotropin (CTP), which are known to prolong the half-life, were produced using the HEK 293 and CHO expression system. The effect of recombinant Gh administration to eel larvae on their somatic growth was investigated in short-term feeding experiments, and it was found that three types of recombinant Ghs with CTP (CTP-reGh, reGh-CTP and reGh-CTP × 2) were more effective in promoting somatic growth in eel larvae than recombinant Ghs without CTP. Among the three recombinant Ghs with CTP, reGh-CTP × 2 had the highest growth-promoting effects, however only when provided in the short term. After long-term administration of reGh-CTP × 2, there was no difference in growth between the Gh administrated group and the control group. The survival rate of eel larvae were not affected by recombinant Ghs. In addition, the mRNA expression of gh, Gh receptors, Igf-I and IGF-II were measured by quantitative real-time PCR, and significant reductions in the expression of gh, Gh receptors and Igf-I were observed. These findings provide useful tools to study the mechanisms of somatic growth and increase understanding of Gh regulation in anguillid eel larvae.