Melatonin Modifies Histone Acetylation During In Vitro Maturation of Mouse Oocytes.

OBJECTIVES: We evaluated the effect of melatonin, as a potent antioxidant agent, on glutathione (GSH) and reactive oxygen species (ROS) levels, as well as histone H3 lysine 9 (H3K9), and H4 lysine 12 (H4K12) acetylation when added to oocytes culture medium. MATERIALS AND METHODS: In this experimental study, two in vitro and in vivo groups were used. In the in vitro group, cumulus oocyte complexes (COCs) from the ovaries of B6D2F1 mice were cultured in maturation medium containing two doses of melatonin (10-9 and 10-6 M) and without melatonin [control group treated with dimethyl sulfoxide (DMSO)] for 22-24 hour. The cumulus expansion and nuclear status were monitored by an inverted microscope. Next, COCs were isolated from the oviducts of superovulated mice and studied as the in vivo group. In in vitro and in vivo matured oocytes, GSH and ROS levels were assessed by monochlorobimane (MCB) and 2-7-dichlorodihydrofluorescein diacetate (H2DCFDA) staining, respectively. Changes in histone acetylation were examined by immunofluorescent staining with specific antibodies against acetylated H3K9 and H4K12. RESULTS: The H4K12 acetylation and ROS levels were significantly higher in the oocytes matured in the in vitro group compared to the in vivo group (P<0.05). Furthermore, glutathione levels in the in vitro group were considerably lower than that of the in vivo group (P<0.05). Melatonin at the concentration of 10-6 M had the most substantial effect on nuclear maturation and histone acetylation as well as glutathione and ROS levels in the in vitro group (P<0.05). CONCLUSIONS: Exogenous melatonin improves the competence of mouse oocytes during in vitro maturation (IVM).

The ability of mouse nuclear transfer embryonic stem cells to differentiate into primordial germ cells.

Nuclear transfer embryonic stem cells (ntESCs) show stem cell characteristics such as pluripotency but cause no immunological disorders. Although ntESCs are able to differentiate into somatic cells, the ability of ntESCs to differentiate into primordial germ cells (PGCs) has not been examined. In this work, we examined the capacity of mouse ntESCs to differentiate into PGCs in vitro. ntESCs aggregated to form embryoid bodies (EB) in EB culture medium supplemented with bone morphogenetic protein 4(BMP4) as the differentiation factor. The expression level of specific PGC genes was compared at days 4 and 8 using real time PCR. Flow cytometry and immunocytochemical staining were used to detect Mvh as a specific PGC marker. ntESCs expressed particular genes related to different stages of PGC development. Flow cytometry and immunocytochemical staining confirmed the presence of Mvh protein in a small number of cells. There were significant differences between cells that differentiated into PGCs in the group treated with Bmp4 compared to non-treated cells. These findings indicate that ntESCs can differentiate into putative PGCs. Improvement of ntESC differentiation into PGCs may be a reliable means of producing mature germ cells.

DNA Methylation and Histone Acetylation Patterns in Cultured Bovine Adipose Tissue-Derived Stem Cells (BADSCs).

OBJECTIVE: Many studies have focused on the epigenetic characteristics of donor cells to improve somatic cell nuclear transfer (SCNT). We hypothesized that the epigenetic status and chromatin structure of undifferentiated bovine adipose tissue-derived stem cells (BADSCs) would not remain constant during different passages. The objective of this study was to determine the mRNA expression patterns of DNA methyltransferases (DNMT1, DNMT3a, DNMT3b) and histone deacetyltransferses (HDAC1, HDAC2, HDAC3) in BADSCs. In addition, we compared the measured levels of octamer binding protein-4 expression (OCT4) and acetylation of H3K9 (H3K9ac) in BADSCs cultures and different passages in vitro. MATERIALS AND METHODS: In this experimental study, subcutaneous fat was obtained from adult cows immediately post-mortem. Relative level of DNMTs and HDACs was examined using quantitative real time polymerase chain reaction (q-PCR), and the level of OCT4 and H3K9ac was analyzed by flow cytometry at passages 3 (P3), 5 (P5) and 7 (P7). RESULTS: The OCT4 protein level was similar at P3 and P5 but a significant decrease in its level was seen at P7. The highest and lowest levels of H3K9ac were observed at P5 and P7, respectively. At P5, the expression of HDACs and DNMTs was significantly decreased. In contrast, a remarkable increase in the expression of DNMTs was observed at P7. CONCLUSION: Our data demonstrated that the epigenetic status of BADSCs was variable during culture. The P5 cells showed the highest level of stemness and multipotency and the lowest level of chromatin compaction. Therefore, we suggest that P5 cells may be more efficient for SCNT compared with other passages.

The Effect of Melatonin on Maturation, Glutathione Level and Expression of H MGB1 Gene in Brilliant Cresyl Blue (BCB) Stained Immature Oocyte.

OBJECTIVE: Nutrients and antioxidants in the medium of immature oocyte have a profound effect on maturation, fertilization and development of resulting embryos. In this study the effects of melatonin as an antioxidant agent on maturation, glutathione level and expression of High mobility group box-1 (HMGB1) gene were evaluated in immature oocytes of mice stained with brilliant cresyl blue (BCB). MATERIALS AND METHODS: In this experimental study, immature oocytes were harvested from ovaries of Naval Medical Research Institute (NMRI) mice. Oocytes were stained with 26 µM BCB for 90 minutes and transferred to in vitro maturation medium containing varying doses of melatonin (10-12, 10-9, 10-6, 10-3 M) and without melatonin, for 22-24 hours. Maturation was monitored using an inverted microscope. Glutathione was assessed by monochlorobimane (MCB) staining and HMGB1 expression in mature oocyte was analyzed using real-time polymerase chain reaction (PCR). RESULTS: Melatonin in the concentration of 10-6 M had the most effect on maturation and HMGB1 expression of BCB+ oocytes (p<0.05). Meanwhile melatonin had no effects on glutathione levels. Additionally in immature BCB- oocytes, compared to the control group, melatonin did not affect cytoplasm maturation (p>0.05). CONCLUSION: In vitro treatment with melatonin increases the maturation and HMGB1 expression in BCB+ immature oocytes and has no significant effect on glutathione levels.