Melamine negatively affects oocyte architecture, oocyte development and fertility in mice.
OBJECTIVE
Does melamine have a toxic effect on oocyte development and fertility in vivo?


CONCLUSIONS
Melamine had toxic effects on oocyte quality and fertility due to its effects on the oocyte cytoskeleton, apoptosis and autophagy induction, and epigenetic modifications in an in vivo mouse model.


BACKGROUND
Melamine is a chemical compound that is widely used during the manufacture of amino resins and plastics. In 2008, melamine was reported to adulterate milk and infant formulas in China, which sparked food safety concerns worldwide. Ingesting melamine may result in reproductive damage, and bladder or kidney stones, which can lead to bladder cancer.


METHODS
Mice were randomly assigned to three groups and fed a diet that included melamine (0, 10 and 50 mg/kg/day) for 8 weeks. The in vivo effect of melamine on female reproduction was examined.


METHODS
We used immunofluorescent staining, western blotting and qRT-PCR to examine the effect of melamine on oocyte quality.


RESULTS
Our results showed the following effects of this melamine-containing diet. (i) Ovary weights were reduced in melamine fed mice. Oocyte developmental competence was also reduced, as shown by reduced polar body extrusion rates. (ii) Melamine feeding resulted in abnormal oocyte cytoskeletons, as shown by increased rates of aberrant spindles and reduced actin microfilament expression. (iii) Melamine exposed oocytes had higher rates of abnormal mitochondrial distributions and early stage apoptosis/autophagy, which were shown by increased microtubule-associated protein 1 light chain 3 (LC3) protein expression level and caspase 9, autophagy-related protein 14 (atg14), and lc3 mRNA levels. (iv) Fluorescence intensity analysis showed that DNA methylation levels were reduced in the oocytes of melamine fed mice. Histone methylation levels were also altered, as Di-methyl-Histone H3 (Lys4) (H3K4me2) level was increased and Tri-methyl-Histone H3 (Lys9) (H3K9me3), Di-methyl-Histone H3 (Lys9) (H3K9me2), and Tri-methyl-Histone H3 (Lys27) (H3K27me3) levels were reduced in oocytes from melamine fed mice. (v) The litter sizes of melamine fed mice were significantly reduced when compared with those of controls.


CONCLUSIONS
Although we examined the possible effects of melamine on oocyte quality and fertility, we did not determine the effect of melamine on offspring development.


CONCLUSIONS
Our findings indicate that melamine plays a major role in oocyte quality and fertility. This information could contribute to a better understanding of melamine toxicity in female reproduction.


BACKGROUND
This study was supported by the National Basic Research Program of China (2014CB138503) and the Natural Science Foundation of Jiangsu Province (BK20140030). The authors have no conflict of interest to disclose.
College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
Xing
X
Duan
College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
Xiao-Xin
XX
Dai
College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
Teng
T
Wang
College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China.
Hong-Lin
HL
Liu
College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China sunsc@njau.edu.cn.
Shao-Chen
SC
Sun
D000818:Animals; D005260:Female; D005298:Fertility / Q000187:drug effects*; D051379:Mice; D008813:Mice, Inbred ICR; D009865:Oocytes / Q000187:drug effects*; D011897:Random Allocation; D014227:Triazines / Q000008:administration & dosage / Q000633:toxicity*
D014227:Triazines; C011907:melamine
cytoskeleton; epigenetic modifications; melamine; mitochondria; oocyte quality