Formaldehyde vapor-induced chronic tracheitis in relation to the expression of S-100 proteins

Abstract

Background and objective: Formaldehyde is the most widely used chemical in daily life; thus, chronic exposure to formaldehyde has been shown to have adverse effects on different organs in humans and animals. Different of industries use formaldehyde including the medical, detergent, cosmetic, food, rubber, metal, wood, leather, petroleum, and agricultural industries and as a hydrogen sulfide scavenger in oil operations. This research was designed to investigate variable tracheal changes arising from chronic formaldehyde exposure by measuring different histomorphometric parameters in accordance with S-100 protein expression. Methods: In this experiment, twenty Wister rats were used, divided into the control group (n=10) and the experimental group (n=10). Animals in the experimental group had approximately 21 days of formaldehyde vapor 40ppm. At the end of the study tracheal samples were collected and used for histopathologic assessments and IHC staining. Results: In comparison to the control group, the experimental group revealed various histological lesions in tracheal structures from lining epithelium till adventitia including highest degrees and scores of; Epithelial necrosis, goblet cell hyperplasia, fibrosis in the submucosa, squamous metaplasia, chronic tracheitis and glandular changes. Results of IHC showed that the S-100 expression in the experimental group displayed higher percentages in different cells (epithelial cells, chondrocytes, and inflammatory cells) which were reported as strong intensity (3+), then moderate intensity (2+), and accompanied by weak intensity (1+), which revealed minimum percentages compared to the control-negative group in which the weak intensity (1+) recorded the highest percentages. Conclusion: Chronic exposure to formaldehyde causes significant histological changes that may lead to cancer induction. S-100 may appear as pro-inflammatory and proliferative marker, also S-100 expression associated with chondrocyte hypertrophy.