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Case Reports
. 2023 Jan;36(1):45-48.
doi: 10.1293/tox.2022-0062. Epub 2022 Nov 2.

Two cases of cartilaginous metaplasia in the sclera of Japanese White rabbits

Kotaro Yamada  1 , Yoshinori Yamagiwa  1 , Miki Masatsugu  1 , Yu Haranosono  1
Affiliations
Case Reports

Two cases of cartilaginous metaplasia in the sclera of Japanese White rabbits

Kotaro Yamada et al. J Toxicol Pathol. 2023 Jan.

Abstract

Spontaneous cartilaginous metaplasia of the sclera has not been reported in rabbits. Herein, we report two cases of spontaneous cartilaginous metaplasia in the sclera of Japanese White (JW) rabbits. Case 1 was noted in a 14-week-old male Kbs:JW rabbit that received a single ocular instillation of 20% isoproterenol (IP) a day before necropsy, and showed no abnormalities in clinical signs, ophthalmological assessments, and necropsy. Case 2 was noted in a 38-week-old male Kbs:JW rabbit that was housed under light-emitting diode (LED) lighting for 26 weeks and showed no effects of LED on clinical signs, ophthalmological assessments, and necropsy. Histological sections of the eyes of both animals were prepared and stained with hematoxylin and eosin (H&E) and Alcian blue, and immunohistochemical staining for vimentin was performed. The H&E-stained specimens showed focal hyaline cartilage-like tissues distributed between the scleral fibers at the posterior pole in both cases. The surrounding scleral fibers were compressed and/or partially destroyed by the cartilage-like tissue. The cartilage-like matrix was stained blue by Alcian blue, and immunohistochemistry showed that chondrocyte-like cells were positive for vimentin. Based on these findings, we diagnosed cartilaginous metaplasia in the sclera of Kbs:JW rabbits. The lesion was farther from the IP administration site in Case 1 and was not accompanied by other ophthalmological or histopathological abnormalities in either of the cases. This implies that the lesions occurred spontaneously owing to the abnormal differentiation of neural crest-derived cells.

Keywords: cartilage; clera; eye; metaplasia; rabbit.

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Figures

Fig. 1.
Fig. 1.
Right eye of a 14-week-old male Japanese White rabbit. A: A lesion (arrow) is focally observed at the posterior pole of the sclera (H&E, bar=2 mm). Inset: basophilic tissue is focally observed at the posterior pole of the sclera (H&E, bar=200 μm). VC: vitreous cavity; Re: retina; Ch: choroid; Sc: sclera. B: High magnification of A. The tissue is observed between the collagen fiber bundles located in the intermediate layer of the sclera. The lesion consists of a basophilic cartilage-like matrix and oval or polygonal chondrocyte-like cells within the cavities. The surrounding scleral fibers are compressed and partially destroyed by the cartilage-like tissue (H&E, bar=20 μm). C: The cartilage-like matrix is stained in blue and penetrates the scleral fibers (Alcian blue staining, bar=20 μm).
Fig. 2.
Fig. 2.
Right eye of a 38-week-old male Japanese White rabbit. A lesion is focally observed at the posterior pole of the sclera. A: The tissue consists of a basophilic cartilage-like matrix and oval cells with foamy cytoplasm. The basophilic matrix penetrates the scleral fibers, and as in Case 1, the cartilage tissue compresses the surrounding scleral fibers (H&E, bar=20 μm). Ch: choroid; Sc: sclera. B: The cartilage-like matrix is stained in blue (Alcian blue staining, bar=20 μm).
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