[Establishment of a dexamethasone-induced congenital cleft palate model in New Zealand rabbits]

Objective: To develop a new congenital cleft palate model suitable for the evaluation of cleft palate surgery and other related treatments. Methods: Ten New Zealand female rabbits (aged 40 weeks, 4.5-5.0 kg) were selected. The next day after mating with male rabbits of the same strain was regarded as the day 1 of gestation (GD1). Ten pregnant rabbits were enrolled with intramuscular injection 1.0 mg dosage of dexamethasone once a day from GD13 to GD16. The caesarean section was performed to obtain the newborn rabbits on GD31 for each pregnant rabbit. Then the rates of the survival and cleft palate rabbits were calculated. The rabbits were divided into two groups according to the method of random number table (10 non-cleft palate rabbits as the control group and 10 cleft palate rabbits as the experimental group). The body weights and physiological behaviors of the rabbits were evaluated and recorded at the age of 1, 2 and 4 weeks respectively after being fed by using standardized gastric tube feeding method. At 4 weeks old, three rabbits in each group were randomly selected for the observation of local anatomy of different layers of the mouth and upper jaw. The anatomical results were photographed for comparative analysis. Results: In this experiment, 48 infants of 10 pregnant rabbits survived under the condition with a survival rate of 66% (48/73), among which the incidence of cleft palate was 60% (29/48). All the rabbits in the control group and the experimental group were able to survive for at least 1 month with stable weight gain. There was no significant difference in weight (P>0.05) and physiological appearance between the two groups. In cleft palate group, most of fetuses showed complete cleft palate with significant differences in the anatomical structure of the upper jaw compared with the control group including the changes in the morphology of the palatal mucosa, the terminal distribution of the soft palate muscles, and the dysplasia and absence of bone structures along the mid-maxillary line. Conclusions: In this study, it was the first time to successfully establish the dexamethasone-induced congenital cleft palate model in New Zealand rabbits for cleft surgical research.