Morphological study on cataractogenesis of the Nakano mouse lens

Background: Although some histopathological features on the Nakano mouse le ns have been pointed out by a few investigators, there seem to have been no detailed studies on the sequential changes that occur. Methods: We used the following two approaches: (1) Observation of the whole lens by dissection microscopy and (2) light and electron microscopic exami nation of the sectioned lens specimen. Results: (1) The Nakano mouse lens showed sustained transparency up to 19 d ays after birth, fine opacity at the 20th day, and development of a mature cataract around the 30th day. In addition, although the Y-shaped posterior suture was normal at the 15th day, bending of the suture line appeared arou nd the 19th day. (2) The cataractous lens revealed degeneration of the epit helial cells and adjacent anterior cortical fibers at the 10th day. Swellin g of the anterior cortical fibers became prominent, and swelling of the pos terior cortical fibers occurred by the 15th day. Upon separation of the sut ure around the 20th day, fine opacity occurred in the perinuclear zone, whi ch extended to the anterior cortex and finally led to the formation of a ma ture cataract. Conclusions: These results indicate that epithelial degeneration is a major feature of cataract in the Nakano mouse, and the subsequent lens fiber swe lling and posterior sutural separation are the underlying causes of the dev elopment of opacity.