The cycling gonad: retinoic-acid synthesis and degradation patterns during adult zebrafish Danio rerio oogenesis

Effects of vitamin A supplementation on ovarian development of Astyanax lacustris (Teleostei: Characidae) during the non-breeding season

Vitamin A (VA) is essential for fish reproduction, however, knowledge of VA requirement of broodstock fish is scarce. We investigated the physiological role of VA supplementation in the ovarian maturation of Astyanax lacustris throughout the non-breeding season. Adult females were distributed in five nutritional treatments, which differed by the amount of VA supplemented in a plant-based diet: T1 = 0, T2 = 1800, T3 = 3600, T4 = 7200, and T5 = 14,400 IU kg^-1 of VA for 60 days after a period of 16 days feeding on a diet poor in VA to reduce body VA content. Plasma total lipids (TL), lipoproteins, and 17β-estradiol (E₂) levels were measured after 30 and 60 days. Somatic indexes and morphophysiological ovarian parameters were calculated and VA concentration was analyzed in the ovaries and liver after 60 days. VA supplementation did not increase the concentration of this nutrient in the liver and ovaries. E₂ plasma level increased in animals fed on 3600 IU kg^-1 of VA (T3) after 60 days and females from T5 group presented a higher RF after 60 days. Ovarian development increased after 60 days compared to that after 30 days, confirmed by the higher gonadosomatic index (all groups). The supplementation with the highest VA level increased RF and decreased plasma TL (after 30 days) and low-density lipoprotein (LDL) (after 60 days) concentrations, showing a potential to improve reproduction even during the non-breeding season; however, its nutritional requirements of VA could be higher.

Basal characterization and in vitro differentiation of putative stem cells derived from the adult mouse ovary

Lately, stem cell approaches have provided new information on reproductive organ function and additionally recommended novel treatment possibilities. The type(s) and differentiation potential of stem cells present in the mammalian ovary are largely unknown; while oogonial stem cells have been reported, we explored the possibility that multipotent stem cells may reside in the ovary and have wide differentiation potential. In this experimental study, homogenates of whole mouse ovaries were sorted using the stem cell surface markers stem cell antigen-1 and stage specific embryonic antigen-1/CD15. Viable double-positive cells 3-10 μm in diameter were evaluated immediately after sorting and after culture using differentiation conditions. Ovarian-derived stem cells were differentiated into the three main cell types: adipocytes, chondrocytes, or osteocytes. The subsequent culture was performed in media containing bone morphogenetic protein 4 (BMP-4) and/or retinoic acid (RA). RA, BMP-4 or the two agents in combination, consistently stimulated germ cell gene expression. RA treatment strongly stimulated germline gene expression and also the development of cells that were morphologically reminiscent of oocytes. The germ cell genes Dazl, Ddx4, Figla, Gdf-9, Nobox, Prdm9, and Sycp-1 were all detected at low levels. Remarkably, treatment with BMP-4 alone significantly increased protein expression of the granulosa cell product anti-Müllerian hormone (AMH). We have shown that an inclusive isolation protocol results in the consistent derivation of multipotent stem cells from the adult ovary; these cells can be differentiated towards the germ cell fate (RA alone), somatic ovarian cell fate as indicated by AMH production (BMP-4 alone), or classical mesenchymal cell types. Taken together, these data suggest the presence of multipotent mesenchymal stem cells in the murine ovary.

Metabolomic changes and polyunsaturated fatty acid biosynthesis during gonadal growth and development in the sea urchin Strongylocentrotus intermedius

Strongylocentrotus intermedius is an important commercial species of sea urchin distributed in the coastal waters of China. However, the metabolomic changes that accompany its gonadal growth and development stages remain unclear. In this study, we have histologically observed gonad growth stages, analyzed the fatty acid composition, and employed an untargeted metabolomic approach to investigate the metabolites associated with the gonadal growth and development of S. intermedius, as well as the biosynthesis and metabolism of polyunsaturated fatty acids (PUFAs) at different stages and in different sexes. The gonad mass of sea urchin increased from 0.70 ± 0.18 g in January (at the recovering stage) to 8.78 ± 2.89 g in July (the reproductive stage), with the GSI increasing from 4.02 ± 0.88% to 16.86 ± 2.79%. We have analyzed 34 types of fatty acids, such as arachidonic acid, eicosapentaenoic acid, etc., of which PUFAs were the dominant fatty acid class in this species, accounting for >48.55% of the total. In the metabolomic analysis, linolelaidic acid, sciadonic acid, cis-8,11,14,17-eicosatetraenoic acid, adrenic acid, docosapentaenoic acid, and tetracosapentaenoic acid were detected in the differentially expressed metabolites of the unsaturated fatty acids biosynthesis pathway. We found that the most significant functional pathways during gonadal growth and development were "arachidonic acid metabolism", "alpha-linolenic acid metabolism" and "linoleic acid metabolism", which are all related to fatty acid metabolism. These results will provide valuable information on the possible presence of both exogenous and endogenous fatty acids in sea urchin gonads and the metabolomic changes in S. intermedius during gonadal growth periods, and will further our understanding of the intermediary metabolism and the molecular bases of growth traits in this species.