Animal Experimental Study Of The Generation And Development Of External Auditory Canal And Middle Ear Cholesteatoma

ObjectiveTo induce cholesteatoma in Mongolian Gerbils and observe the modality of its local growth and destruction.MethodTo conduct our study, Mongolian gerbils, Meriones unguiculatus, between 2 and 6 months of age with a total number of 50 were used. All these 50 animals were examed under microscope to confirm the double ear external auditory canal and tympanic membrane integrity. For each animal, the same surgical procedure of ligation of the right external auditory canal was performed after anesthetized and we choose the left ear as the comparison. Then these 50 animals were randomizedly divided into five groups. After all these procedure, the states of growth of the middle ear cholesteatoma were observed 15,30,45,60,90 days after the operation. The staging of the induced middle ear cholesteatoma was also conducted. Finally, we took the cholesteatoma tissue to perform the pathological examination.ResultWe succeeded in inducing middle ear cholesteatoma in 38 animals.The total achievement ratio was 76%. And the corresponding achievement ratio for each group is relatively 50%(15days),60%(30days),80%(45days),90%(60days),100%(90days). Open the double bulla, we can see cholesteatoma grew into the right bullae, and along with the time extending, the circumscription of encroachment was gradually enlarged. Pathological examination showed that there was sac formed obveriously. The lateral layer of the sac was composed by inflammatory cells and fibrous tissue. And the inner layer was stratified squamous epithelium. There was a great quantity of deciduous epithelium tissue and cuticularization. At the same time, we can see massive inflammatory cells infiltration, mucus effusion and calcification.ConclusionSurgical procedure of ligation of the external auditory canal can easily induce external auditory canal and middle ear cholesteatoma in Mongolian gerbils. The achievement ratio is relatively high.The growth and development of cholesteatoma in the model rats have the same characteristic with the cholesteatoma in human beings. Aplication of Mongolian gerbils, Meriones unguiculatus to set up an animal model is an ideal method to study the pathogenesy and destruction performance of external auditory canal and middle ear cholesteatoma.