Morphological study on cataractogenesis of the Nakano mouse lens

· Background: Although some histopathological features on the Nakano mouse lens 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 examination of the sectioned lens specimen. · Results: (1) The Nakano mouse lens showed sustained transparency up to 19 days 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 around the 19th day. (2) The cataractous lens revealed degeneration of the epithelial cells and adjacent anterior cortical fibers at the 10th day. Swelling of the anterior cortical fibers became prominent, and swelling of the posterior cortical fibers occurred by the 15th day. Upon separation of the suture around the 20th day, fine opacity occurred in the perinuclear zone, which extended to the anterior cortex and finally led to the formation of a mature cataract. · Conclusions: These results indicate that epithelial degeneration is a major feature of cataract in the Nakano mouse, and the subsequent lens fiber swelling and posterior sutural separation are the underlying causes of the development of opacity.