[The correlation between tissue injury and calcium oxalate crystal production in rat's lung with experimental Aspergillus niger infection].

It is well known that calcium oxalate crystals (crystal) are commonly found in Aspergillus niger (A. niger) infection site. However, there have been no pathological reports of crystal production and tissue injury using an animal model. I experienced a case with pulmonary aspergilloma and infiltration shadow of the lung that I guessed resulted in crystal-induced inflammation. I performed animal experiments to investigate the possibility of crystals to cause tissue injury. Two different types of immunosuppressed rat models; i.e. cortisone acetate (CA) and CA + cyclophosphamide (CPM) induced-immunodeficiency models (CA model, CA + CPM model), were used for the experiments. In both models, rats were infected with A. niger. Then, the lungs were removed and examined histopathologically. The crystals were rarely found in both models on the third day after inoculation and it increased as time passed. However, more growth of hyphae and more production of crystals were observed in the CA + CPM model. In the CA model, crystal depositions in the bronchial epithelium and erosion of the bronchial epithelium adjacent to the crystals were observed. Crystal depositions in the bronchial epithelium were also seen in the CA + CPM model. In this lesion, severe erosions of the bronchial epithelium and invasion of A. niger mycelium into the tissue were observed. These findings suggest, the crystals in the bronchial epithelium may expand and destroy the cells around them. Therefore, I think that the crystals can induce tissue injury. However, in alveolar portions, depositions of crystals were seen mainly in the margin rather than in the central part of mycelial growth, but no findings indicating injury of the alveolar epithelial cells by crystals were seen. Therefore, possibility of crystals to cause tissue injury in the alveolar portion is not yet clear.