Niacin Inhibits Apoptosis and Rescues Premature Ovarian Failure
Cellular Physiology and Biochemistry
Background/Aims: Over 99% of mouse and human ovarian follicles will undergo specialized cell death including atresia and apoptosis. Reduction of apoptosis may help reduce infertility and maintain the reproductive ability in women. Methods: 3-day B6D2F1 mice were used to culture small follicle and ovary tissue with niacin and 18-day mice were intraperitoneal injected with niacin to determine its effect on follicle development. Then establish 8-weeks POF animal model with cytoxan (CTX) or
... an (CTX) or radiation. Treatment group was given 0.1 mL of 100 mM niacin by an intraperitoneal injection twice before ovulation. The ovaries were collected and the follicles were counted and categorized, and ovarian histologic sections were stained for TUNEL. Ovarian function was then evaluated by monitoring ovulation. Microarray analyses, Western blot, immunofluorescence and real-time quantitative PCR were used to assess the mechanism of ovarian injury and repair. Results: We found that niacin promotes follicle growth in the immature oocyte and it increased the levels of a germ-line cell marker DDX4, and a cell proliferation marker PCNA in the ovary. Addition of niacin to the cell culture reduced oocyte apoptosis in vitro. Administration of niacin to treat premature ovarian failure (POF) in mouse models showed inhibition of follicular apoptosis under harmful conditions, such as radiation and chemotherapy damage, by markedly reducing cumulus cell apoptosis. Additionally, the number of developing follicles increased after administration of niacin. Conclusion: Niacin may have an important function in treating POF by reducing apoptosis in clinical applications. Fig. 3. The niacin affects cell arrest and apoptosis genes. A The cell arrest factor FOXO3 expression in wildtype group and in niacin group. (Red: FOXO3, Blue: DAPI) The DDX4 expression in the mice ovary in wildtype group and in niacin group. (Red: DDX4, Blue: DAPI) The DNA damage marker TUNNEL in wildtype group and in niacin group. (Green: Tunnel, Blue: DAPI) B Western blot analysis of protein expression in the niacin treated group and control group. The FOXO3 expression is slightly decreased and acetylation is increased and the SIRT1 expression is slightly decreased. The oocyte marker DDX4 is increased by niacin too. Even healthy women oocytes are sequestered in primordial follicles for decades and then recruited into the growing pool, but most will go through apoptosis or die. Granulosa cells control the oocyte's fate, and follicle growth requires granulosa cell proliferation. Granulosa cell death leads to follicle atresia. And cell death happens naturally when ovary suffers damage. If we can inhibit the cell death of granulosa cells, maybe we can help to reduce the exhausting speed of oocyte pool. Our results demonstrate that niacin promotes primary follicle development both in vitro and in vivo. We used 18 days fetal mice which ovary follicles are mainly dormant, we found Fig. 4 . The RNA microarray data of niacin group and normal control. A RNA microarray data for the 3d-mouse ovaries and niacin-treated 3d-mouse ovaries. The ovaries were collected, cut into several small pieces and cultured with or without niacin for 48 hours before RNA testing. A hierarchical clustering of differentially expressed genes in the ovaries of niacin-treated group and WT group. B Overview of gene expression comparing the WT and the niacin-treated group. The X and Y axes present the intensity of gene transcription in WT and niacin, respectively. The black dots indicate genes with no significant change in transcription level, while the red and green dots indicate up regulated and down regulated genes, respectively. C Genes involved in the cell proliferation and apoptosis pathways that were either up regulated or down regulated in the niacin-treated ovaries.