Methodology of a rabbit model of chronic dacryocystitis

Abstract

Background Chronic dacryocystitis is a common infectious lacrimal apparatus disease.Whether infection factors or lacrimal duct obstruction play a major role in the process of recurrent lesions is still controversial.Establishing a reasonable animal model contributes to its pathogenesis study.However, an effective methodology on establishing chronic dacryocystitis animal model is lack. Objective This study was to develop a method of establishing chronic dacryocystitis animal model. Methods Sixty-six Japanese white rabbits were randomized into 6 groups and 11 for each, and the right eye of each rabbit served as the experimental eye.The solution of 2, 4-toluene disocyanate (TDI) with olive oil was droped in the right nasal cavity to induce allergic rhinitis in the temporary lacrimal duct obstruction group; 0.15 ml mixture of methyl methacrylate (MMA) with polymethyl methacrylate (PMMA) was injected into lacrimal duct via lacrimal punctum in the permanent lacrimal duct obstruction group; 0.3 ml Staphylococcus aureus suspension at the concentration of 1×107/ml was injected into lacrimal duct via punctum in the only bacterial inoculation group, and the Staphylococcus aureus suspension was injected folowing the operation of allergic rhinitis or mixture of MMA injection respectively in the temporary lacrimal duct obstruction+ bacterial group and permanent lacrimal duct obstruction+ bacterial group.An equal volume of sterile saline solution was injected into the lacrimal duct in the normal control group.The clinical manifestations were observed before operation, immediately at operation, 1 day and 7 days after operation as a criteria of model of chronic dacryocystitis.Sringing of lacrimal duct was performed to evaluate the lacrimal patency, and parallel lacrimal CT angiography of lacrimal duct was carried out to identify the location of obstruction.The specimens of lacrimal sac and duct walls were collected for the bactriology and histopathology examination.The use and care of the experimental amnimals comlied with ARVO Statement. Results The animals were observed for consecutive 3 months.No chronic dacryocystitis occurred in the temporary lacrimal duct obstruction group, only bacterial inoculation group, temporary lacrimal duct obstruction+ bacterial group and normal control group.The chronic dacryocystitis models were successfully established in 8 eyes in the permanent lacrimal duct obstruction group and 9 eyes in the permanent lacrimal duct obstruction+ bacterial group.The lacrimal duct was closed, with the liquid completely reflux in the model eyes by sringing of lacrimal duct.Lacrimal CT angiography displayed the visible completely blockage of nasolacrimal duct in nasolacrimal duct distal namely nasolacrimal duct bone and nasal segment of the turning point and a visible expansion of proximal of obstructive site.Gram-negative bacilli were found in the models of the permanent lacrimal duct obstruction group and Staphylococcus aureus was dominant bacteria in the permanent lacrimal duct obstruction+ bacterial group.No abnormality was found in the specimens from temporary lacrimal duct obstruction group, only bacterial inoculation group, temporary lacrimal duct obstruction+ bacterial group and normal control group, and infiltration of inflammatory cells and proliferatin of mucosa were seen in the model eyes of permanent lacrimal duct obstruction group and permanent lacrimal duct obstruction+ bacterial group. Conclusions Permanent obstruction of lacrimal duct is a necessary condition to the establishment of animal model of chronic dacryocystitis, which plays a key role in the occurrence of rabbit chronic dacryocystitis. Key words: Dacryocystitis, chronic; Model, animal; Lacrimal apparatus diseases; Nasolacrimal duct/pathology; Lacrimal duct obstruction