Corneal changes in manganese-deficient rats

This study was undertaken to examine the changes in the cornea due to dietary manganese (Mn) deficiency in Wistar-Kyoto rats, because there is a lack of information on the significance of manganese in the cornea.

Mature female Wistar-Kyoto albino rats were mated with males. All pregnant females were divided into Mn-deficient and control groups. The offspring were fed a Mn-deficient diet. When they reached age 3 months, Mn-deficient females were mated with Mn-deficient males. The offspring of this second generation of Mn-deficient rats continued to be fed on the Mn-deficient diet and were used for the experiment. The corneas were examined at age 2 months. After 3 months on a Mn-deficient diet, the rats were given a normal diet for a 3-month recovery experiment. The corneas were examined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM).

TEM revealed very few microvilli and bundles of tonofibrils and abnormal mitochondria in the corneal epithelium of Mn-deficient rats. The stroma was thin, and collagen fibers were decreased prominently in diameter. Descemet's membrane was thinner than in the control group. SEM showed many fewer microvilli in the Mn-deficient rats and more dark cells in the most superficial layer of epithelium. SEM also showed endothelial cells with a pentagonal instead of a hexagonal shape in Mn-deficient rats. Rats fed a normal diet for 3 months after Mn deficiency showed a normal serum Mn level and almost normal corneal structure.

This study suggested that the cornea needs Mn for the maintenance of its cell structure.