Ocular Surface in Zn-Deficient Rats

Abstract

Purpose: We studied the cornea and conjunctiva of Zn-deficient rats with an electron microscope and time-of-flight secondary ion mass spectrometry (TOF-SIMS) to elucidate the role of trace elements in the cornea and conjunctiva. Materials and Methods: Twenty-one-day-old Wistar Kyoto rats were fed a Zn-deficient diet and deionized water for 7 weeks and then killed. The control rats were fed a Zn-deficient diet and deionized water supplemented with 3 mg Zn/100 ml. After 7 weeks on the deficient diet, another group of rats was given drinking water containing 3 mg Zn/100 ml and the usual diet containing 4.7 mg Zn/100 g for 8 weeks for recovery. The cornea and conjunctiva were examined by electron microscopy and TOF-SIMS. Results: Microvilli and microplicae in the most superficial layer of the epithelium of the Zn-deficient rat conjunctiva and cornea were prominently reduced, and dark cells were significantly increased. The numbers of goblet cells were decreased in the conjunctiva of the Zn-deficient group. Zn, Ca and Al ions were significantly fewer, but K, Fe, Cl and S ions were significantly more numerous in the Zn-deficient group than in the control group. In the cornea of the Zn-deficient group, there was significantly more Cl but less Ca and vitamin C than in the controls. Discussion: Zn deficiency may interfere with protein, nucleic acid and collagen synthesis through the reduction of Zn-containing enzymes. Myosin-like substance, actin filaments and tonofibrils are important structural components for microvilli and microplicae in the epithelium. Maldevelopment of these structural components may be related to disturbed activities of Zn-containing enzymes in protein and collagen synthesis because of Zn deficiency. In addition, Zn deficiency caused changes in the levels of Zn and other trace elements such as Ca, Al, S, Fe, and Cl and vitamin C. Conclusion: Zn deficiency resulted in poorly developed microvilli and microplicae on the ocular surface tissues, reduced the number of goblet cells and changed the quantity of trace elements and vitamin C.

Conditional Deletion of the Mouse Klf4 Gene Results in Corneal Epithelial Fragility, Stromal Edema, and Loss of Conjunctival Goblet Cells

“…Additional symptoms of dry eye such as a reduced number of microvilli on the Klf4CN corneal surface along with the corneal epithelial bulli strengthen the link between dry eye syndrome and Klf4. A reduced number of microvilli on the superficial corneal epithelial cells and a reduced number of conjunctival goblet cells were also observed in rats fed a zincdeficient diet, providing additional circumstantial evidence for the involvement of zinc finger transcription factors such as KLF4 in ocular surface development and maintenance (28).…”

Impression cytology with scanning electron microscopy: a new method in the study of conjunctival microvilli

“…9,10 Riboflavin, zinc, vitamin E, vitamin A, and magnesium deficiency was found to cause alterations of microvilli and goblet cells of the corneo-conjunctival epithelium in rats. [25][26][27] This suggests that the exchange of nutrients between the tear film and the conjunctival epithelium is altered in this condition. However, it is not known whether the alteration originates in microvilli or goblet cells.…”

Intestinal morphology assessments of rats fed phytic acid extract from sweet potato (Ipomoea batatas) and IP6

“…It is a highly nutritious crop with high levels of ascorbic acid, starch, vitamins of the B complex and anthocyanins . Positive association between zinc status and goblet cells are well established, with zinc‐deficient mice having poorly developed microvilli and microplicae on the ocular surface tissues and reduced numbers of goblet cells . A zinc‐finger transcription factor Klf4 (formerly GKLF) expressed in the epithelia of many organs is also shown to play an important role in proliferation and/or differentiation of many cells with specificity for goblet cells .…”