Effect of social isolation on rat ovary and the possible protective role of melatonin: light, electron microscopic, biochemical and molecular study

Background: Social Isolation (SI) is an influential stressor
in animals and humans, which has a negative impact on mental
and physical health. It is associated with increased oxidative
stress and decreased antioxidant capacity. Melatonin (MT) is
well known by its antioxidant properties that help in prevention
of tissue damage.
Aim of Study: The present study aimed to investigate the
harmful effect of SI on rat ovary and the possible protective
role of MT.
Material and Methods: Twenty adult female albino rats
were divided into four groups; five rats in each (control, MT,
SI and SI + MT). Histological examination was done using
hematoxylin and eosin, semithin sections were stained with
toluidine blue and ultrathin sections were performed. Measurements of Malondialdehyde (MDA) and Superoxide Dismutase (SOD) activity in ovarian tissue were carried out.
Quantitative analysis of SIRT1 gene expression was done by
real-time Polymerase Chain Reaction (PCR). Morphometric
measurements were also performed.
Results: Light microscopic examination of ovarian follicles
from SI group showed shrunken granulosa cells with pyknotic
nuclei and irregular oocytes with rarified cytoplasm. Cytoplasmic vacuolation was observed in granulosa cells, theca
cells and granulosa lutein cells. Ultrastructural examination
of granulocsa cells showed swollen mitochondria and abundant
lipid droplets. The oocytes exhibited disrupted microvilli.
There was significant decrease in the mean follicular diameter,
granulosa and theca layer thickness in SI group compared to
control group. These morphological changes were associated
with significant increase in MDA and decrease in SOD activity,
in addition to increased SIRT1 gene expression. Concomitant
administration of MT improved the previously mentioned
alterations.
Conclusion: Social isolation induced histological, ultrastructural and morphometric changes in the ovary of rats.
These changes were associated with oxidative stress, decreased