# Effects of Ageing, Oestrogen Level and Altered Dietary Loading on Rat Mandibular Cartilage—A Polarised Light Microscopy Study

## TL;DR

This study used polarized light microscopy to examine how age, estrogen levels, and diet affect the structure of rat mandibular cartilage.

## Contribution

The study reveals how aging and dietary changes influence collagen fibril structure in rat mandibular cartilage, with diet having a significant impact.

## Key findings

- Ageing increased collagen fibril orientation angles, especially in the superficial layer of cartilage.
- Harder diets significantly altered collagen fibril orientation and retardance in specific cartilage regions.
- Oestrogen deficiency increased fibril orientation angles and disrupted collagen structure coherence.

## Abstract

The mandibular condylar cartilage (MCC) of rats was examined with polarised light microscopy (PLM) to study the effects of ageing, oestrogen level, and altered dietary loading on the structure of the MCC.

96 Sprague–Dawley rats were separated into 12 groups based on their age (5 months [young] and 14 months [old]), oestrogen status (ovariectomised [OVX], non‐ovariectomised [non‐OVX]), and diet (hard, normal, or soft). The MCC specimens were examined using PLM to evaluate the orientation and retardation of collagen fibrils. The MCC was segmented sagittally into three distinct regions: anterior, most superior, and posterior. For each segment, the PLM values at varying depths were statistically compared across different groups using an N‐way analysis of variance (ANOVA).

Ageing significantly increased collagen fibril orientation angles with respect to cartilage surface across all segments, particularly in the superficial layer, indicating structural modifications. Oestrogen deficiency (OVX) tended to increase fibril orientation angles and caused incoherence in retardance. In the anterior segment, a harder diet increased fibre orientation angles, while in the most superior segment it decreased retardance, further impacting collagen structure.

Age and dietary loading significantly influenced collagen fibril orientation and retardance, with ageing generally leading to increased fibril orientation angles and often resulting in increased retardance. Dietary variations, particularly harder diets, emerged as a key factor with more substantial effects on collagen structure, affecting both fibre orientation and retardance.