The Micromorphological Course of Irradiation-Induced Oral Mucositis in Rat

The Micromorphological Course of Irradiation-Induced Oral Mucositis in Rat

Abstract

Objectives:

To establish an experimental radiation-induced mucositis model in the Sprague-Dawley rat, and to use this model to study the temporal changes in morphology, including invasion by immune cells (polymorphonuclear (PMN) cells and macrophages – both activated M1 macrophages and wound healing M2 macrophages) following irradiation.

Materials and methods:

Irradiation was given as a single fraction treatment to the entire head using a conventional high-energy linear accelerator (Varian Clinac 2300 C/D). Treatment was in as single fractions of 20 Gy, using 6 MV photons. Morphological changes in irradiated lingual and buccal tissues were assessed using a haematoxylin-eosin staining, while invasion by immune cells was established by immunohistochemistry.

Results:

A single dose of 20 Gy gave rise to ulcerations and a manifest oral mucositis. Atrophy of the epithelial layer was seen on day 5 in the buccal specimens and on day 7 in the lingual specimens. Regeneration of the epithelial layer was observed day 13 in the buccal specimens and on day 17 in the lingual specimens. A peak influx of PMN cells was observed before a peak of macrophages was seen. The concentration of PMN cells decreased after the acute phase had passed – and was then lower than in control samples. A peak in the influx of general macrophages (ED 1 stain) was observed day 9, and also on day 11 of M2 macrophages (ED 2 stain).

Conclusion:

An experimental model of irradiation-induced oral mucositis was established in the Sprague-Dawley rat, using a high-energy linear accelerator, which provides a research platform for the study of radiotherapy-induced oral mucositis pathogenesis. A uniform morphological pattern was observed, showing a rapid healing process following irradiation. An influx of PMN cells peaked before the macrophage peak, whereas those peak of M2 macrophages occurred 2 days after the peak of general macrophages.