The effect of vitamin A has been studied on lens regeneration in young (7 days old) as well as adult mice. A longitudinal slit was made under local anesthesia in the cornea over the lens. The lens was extracted intact through the incision. Intraperitonial injection of vitamin A (0.05 ml of 30 IU/ml in young and 0.05 ml of 50 IU/ml in adult) was given to the operated animals. Vitamin A was found to induce lens regeneration in not only young but also in adult mice. Regenerated lenses were similar in shape, size, transparency and histological features to normal intact lenses.

No abstract

After removal of both the lateral eyes of external gill stage tadpoles of the toad Bufo melanostictus, the pineal organ gets transformed into a median eye. This type of transformation occurs in tadpoles of both control and vitamin A treated groups. However, vitamin A increases the likelihood of homeotic regeneration (57% in the control group and 71% in the vitamin A treated group). Histological studies showed that the newly transformed median eye developed from the pineal organ. The pineal eye so developed possessed all components of a normal eye such as a retina, sensory cells and lens.

The present study supports previous finding that vitamin A can induce and accelerate lens regeneration in pigmented epithelial cells (PECs) of dorsal iris not only in amphibians but also in young and adult swiss albino mice, guinea pig, rabbit and pigs. In lens regeneration, several workers have shown that vitamin A possesses the mitogenic activity which causes functional impairment of retinoid receptors and thereby inhibits the lens regeneration. The purpose of present study is to know how retinoids and their derivatives interact with Retinoid X receptor (Rxr alpha) and thus helping in lens regeneration. The docking studies of human and mice Rxr alpha were performed against vitamin A and 9-cis retinoic acid (vitamin A1) using autodock and the results were analyzed using Discovery Studio from Accelrys. The results show that there is a significant similarity in interaction energy of Rxr alpha of mice and human. The highest rank docked energy of Rxr alpha mice with vitamin A was -11.65 kcal, which was much closed to -11.83 kcal of 9-cis retinoic acid. Similarly, in human Rxr alpha receptor, the highest docked energy showed the significant similarity with vitamin A (-12.19 kcal) and 9cis retinoic acid (-12.14 kcal). This study suggests that vitamin A shows effect on proliferation and differentiation similar to the 9-cis retinoic acid and also proves that vitamin A acts on Retinoid X alpha receptors and enhance lens regeneration in mammals.

After removal of lens from eye of Rana cyanophlyctis, the pigmented epithelial cells of dorsal iris started to proliferate and dedifferentiate and consequently regenerate lens. Vitamin A and ascorbic acid enhanced the percentage lens regeneration not only in young tadpoles but also in froglets. Lens regeneration ability declined with age of animals in both control as well as treated groups.