Study of Experimental Animal Model of Oral Precancerous Lesions in Rats

Objective: To establish an experimental animal model of oral precancerous lesions in rats. Methods: 57 Wistar rats were randomly divided into experimental group ,control group and propylene glycol group. The 0.5% 4-nitroquinoline 1-oxide( 4-NQO) in propylene glycol was painted on middle palate three times per week in experimental group rats, prolylene glycol group was painted with prolylene glycol only,the control group was left unpainted .Groups of animals were killed at intervals ranging from 8,12 and 20 weeks after the first painting. Their palatal mucosa were removed for histopathological and proliferative cell nuclear antigene(PCNA) label index(PI) assessment. Results: The palate in rats treated with 4-NQO for 8 weeks showed hyperplasia (89.0%) and mild dysplasia (11.0%); those for 12 weeks showed mild dysplasia (11.0%) and moderate dysplasia (66.7%) and severe dysplasia (22,3); those for 20 weeks showed in situ carcinoma to well-differentiated invasive squamous cell carcinoma. The severity of lesions and PI corresponded to the duration of 4-NQO painting.Conclusion: In the rat palate model, continuous application of 4-NQO for 12 weeks results in moderate or severe dysplasia.The results indicate that 4-NQO reliably produced preneoplastic palate mucosa lesions, which morphologically and histologically mimic human oral carcinogenesis,and 12 weeks is the best time for observation of oral precancerous lesions.