Histopathological study of hereditary cataractous lenses in SCR strain rat

A new cataractous rat strain, Shumiya Cataract Rat (SCR), which was derived from the cross-breeder formed between the spontaneous hypertensive rat and the Zucker fatty rat, was studied by light and electron microscopy. The earliest change was the occurrence of some displaced nuclei in the posterior cortical fibres at birth. By 2 weeks of age, mild dysplasia of the anterior suture, aggregated epithelial cells overlying the sutural area, and poorly differentiated epithelial cells at the bow area were observable. At 3 weeks, unusually dense lens fibres near dense epithelial cells were found at the equator, and some epithelial cells showed accellularity after 4 weeks. Swelling and liquefaction of the lens fibres appeared in the anterior cortex by this stage. By 6 weeks, these changes extended toward the equatorial region. At 7 weeks, a sutural gap occurred at the anterior polar area, and this gap reached a maximum at 8 weeks. At this time, swelling of the posterior extremities of the lens fibres appeared, showing a small placoid opacity of the posterior subcapsular region under a dissecting microscope. At 10 weeks, small amounts of liquefaction were observed in this region. Between 10.5 and 11 weeks, as the posterior suture of liquefaction were observed in this region. Between 10.5 and 11 weeks, as the posterior suture separated, opacification appeared around the separated sutural area and rapidly developed into a mature cataract. The mechanism of cataract formation in the SCR rat lens may be associated with the continuous occurrence of a small proportion of poorly-differentiated epithelial cells at the bow area and sutural dysplasia of the anterior lens fibres.