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May 31, 2026Saja Hussain Dilfy
Department of Biology, College of Education for Pure Science, University of Wasit.
Abstract
Background: The pineal gland is an essential neuroendocrine organ that secretes melatonin and regulates
biological rhythms. This gland’s structure deteriorates with age and is frequently connected to hormonal
and nutritional deficits. The purpose of this study was to assess the age-related histological alterations in
male rats’ pineal glands and investigate their relationship to melatonin levels, blood vitamin D3, and the
expression of vitamin D receptors (VDR).
Methods and Procedures: Three age groups of thirty-six male Wistar rats were created: Group I (young,
three months), Group II (middle-aged, nine months), and Group III (old, eighteen months). Hematoxylin
and Eosin (H&E) and Masson’s Trichrome stains were used for the histological analysis. Serum
25(OH)D3, 1,25(OH)₂D3, and melatonin were evaluated using biochemical methods, and semiquantitative immunohistochemistry (H-score) was used to measure VDR expression.
Results: Significant progressive shrinkage of the pineal gland, as indicated by a decline in nuclear
diameter, pinealocyte count, and gland volume, was linked to aging (p < 0.01). Histological results showed
widespread calcification (corpora arenacea) and a significant rise in interstitial fibrosis (from 8% in Group
I to 42% in Group III). According to biochemical findings, aged rats’ serum melatonin and vitamin D3
levels significantly decreased (p < 0.01). Additionally, the H-score decreased from 142.4 in young rats to
55.2 in the oldest group, indicating a significant decline in VDR immunoreactivity with age. Vitamin D3
levels and pineal structural integrity and VDR expression were found to be strongly positively correlated
by Pearson correlation analysis (r = 0.889).
Conclusion: The findings show a strong correlation between decreased melatonin production and the
degradation of the Vitamin D3-VDR axis and age-related pineal gland degeneration. These results imply that vitamin D3 may have a neuroprotective function in preserving the pineal gland’s histological vitality and reducing age-related fibrosis and calcification.
