Retinoic acid enhances ovarian steroidogenesis by regulating granulosa cell proliferation and MESP2/STAR/CYP11A1 pathway.

INTRODUCTION: Ovarian steroidogenesis not only affects the embryonic development and pregnancy outcome, but also associates with many diseases in mammals and women. Exploring the nutrients and mechanisms influencing ovarian steroidogenesis is critical to maintaining the optimal reproductive performance, as well as guaranteeing body health. OBJECTIVES: This research aimed to explore the effect of retinol metabolism on ovarian steroidogenesis and the underlying mechanisms. METHODS: Comparative transcriptomic analysis of ovaries from normal and low reproductive performance sows were performed to identify the main causes leading to low fertility. The metabolites regulating steroid hormones synthesis were investigated in ovarian granulosa cells. Gene interference, overexpression, dual-luciferase reporter assays, chromatin immunoprecipitation and transcriptome analysis were further conducted to explore the underlying mechanisms of Aldh1a1 mediating ovarian steroidogenesis. RESULTS: Transcriptome analysis of ovaries from normal and low reproductive performance sows showed the significant differences in both retinol metabolism and steroid hormones synthesis, indicating retinol metabolism probably influenced steroid hormones synthesis. The related metabolite retinoic acid was furtherly proven a highly active and potent substance strengthening estrogen and progesterone synthesis in ovarian granulosa cells. For the first time, we revealed that retinoic acid synthesis in porcine and human ovarian granulosa cells was dominated by Aldh1a1, and required the assistance of Aldh1a2. Importantly, we demonstrated that Aldh1a1 enhanced the proliferation of ovarian granulosa cells by activating PI3K-Akt-hedgehog signaling pathways. In addition, Aldh1a1 regulated the expression of transcription factor MESP2, which targeted the transcription of Star and Cyp11a1 through binding to corresponding promoter regions. CONCLUSION: Our data identified Aldh1a1 modulates ovarian steroidogenesis through enhancing granulosa cell proliferation and MESP2/STAR/CYP11A1 pathway. These findings provide valuable clues for improving ovarian health in mammals.

Establishment and application of high throughput screening cell model for nutrient regulation of embryonic development.

Embryo development exerts far-reaching influence on pregnancy outcome, postnatal development and lifelong health. Thereafter, to select functional nutrients to improve embryo development is of great importance. Herein, a stable porcine trophectoderm cell line expressing a luciferase reporter gene driven by a 1,009 bp PCNA gene promoter was constructed through lentiviral transduction and G418 selection. A high throughput screening assay was subsequently developed using the stable reporter cell line to screen a library of 225 nutrients. Seven nutrients with a minimum Z-score of 2.0 were initially identified to be capable of enhancing embryonic development. Among these nutrients, resveratrol, apigenin, and retinol palmitate were furtherly confirmed the beneficial effects for embryo development. Resveratrol significantly increased the expression of key genes involved in pTr cell proliferation and the number of S-phase cells. Resveratrol was furtherly confirmed to promote the expression of key genes in trophoblast development and increase embryo adhesion rate in vitro. Similarly, dietary 0.05% resveratrol supplementation significantly increased the number of embryo attachment and serum level of P4 and E2 in rats. Resveratrol could also improve maternal antioxidant levels and reduce intracellular ROS. Collectively, a high throughput screening cell model for nutrient regulation of embryonic development was established, which can be used to highly effectively select the potential candidates for embryo development. These findings have great implications for exploring optimal functional nutrients to improve embryo development, ultimately beneficial for pregnancy outcome, offspring postnatal development and lifelong health for human beings and mammalian animals.

Role of functional fatty acids in modulation of reproductive potential in livestock.

Fatty acids are not only widely known as energy sources, but also play important roles in many metabolic pathways. The significance of fatty acids in modulating the reproductive potential of livestock has received greater recognition in recent years. Functional fatty acids and their metabolites improve follicular development, oocyte maturation and embryo development, as well as endometrial receptivity and placental vascular development, through enhancing energy supply and precursors for the synthesis of their productive hormones, such as steroid hormones and prostaglandins. However, many studies are focused on the impacts of individual functional fatty acids in the reproductive cycle, lacking studies involved in deeper mechanisms and optimal fatty acid requirements for specific physiological stages. Therefore, an overall consideration of the combination and synergy of functional fatty acids and the establishment of optimal fatty acid requirement for specific stages is needed to improve reproductive potential in livestock.