Abstract:

Objective To compare morphologic characteristics of the corneal structures under light microscope and transmission electron microscope(TEM) among seven experimental animals which included BALB/c mice, guinea pigs, New Zealand rabbits, cats, dogs, pigs and cattle. Design Experimental study. Participants BALB/c mice, guinea pigs, New Zealand rabbits, cats, dogs, pigs and cattle. Methods BALB/c mice (8-12 weeks), guinea pigs (350-450g), New Zealand rabbits (2.5-3.5Kg), cats, dogs, pigs and cattle were chosen for study and six fresh eyeballs per kind were acquired. Cornea of each eye was fixated and sliced for observation under light microscope and TEM. Pictures were taken for comparison. Main Outcome Measures Corneal morphology and thickness of every layer, Bowman's membrane and Descemet's membrane exist or not, characteristics of basal layers and hemidesmosomes. Results In terms of thickness distribution, the central corneas of rabbits, dogs, pigs and cattle are thin, the limbal corneas of them are thick, which is similar to that of human corneas; the central corneas of guinea pigs and cats are thick, the limbal corneas of them are thin; the central cornea and limbal cornea thickness is similar in BALB/c mice. The thickness of central corneal epithelium of guinea pig is the nearest to that of human among seven kinds of animals. The average thickness of corneal epithelium, the thickness of central cornea, the thickness of central and paracentral corneal stroma of rabbits are the nearest to that of human. The thickness of corneal limbus of cattle is the nearest to that of human. The average thickness of corneal stroma of dog is the nearest to that of human. The thickness of Descemet's membrane of cattle is the nearest to that of human. The thickness of corneal endothelium, the thickness ratio of Descemet's membrane to endothelium of pig are the nearest to those of human. Under light microscope, the epithelial morphology of seven kinds of animalsis similar: stratified aquamous epithelial cells are long and flat, wing cells are polygonal, basal cells are single-layer cylindrical. It's unclear whether Bowman's membranes exist or not in the corneas of seven kinds of animal under light microscope. Under light microscope, the collageous fibers of corneal stroma are in alignment; the Descemet's membrane can be differentiated which is amorphous; the endothelium is single flat. Under TEM, there is no Bowman's membrane in  BALB/c mouse and dog cornea. However, the Bowman's membranes exist in the corneas of rabbits, cats, pigs and cattle. It's unclear whether the Bowman's membranes exist in the corneas of guinea pigs because of the unclear pictures. The Descemet's membrane in the cornea of BALB/c mouse appears like containing many shuttles or mitochondriae, however, in the cornea of cattle, it looks like latticework. The average diameters of hemidesmosomes of seven kinds of animals are as following: mice 0.16±0.01, rabbits 0.18±0.02, cats 0.27±0.06, dogs 0.19±0.08, pigs 1.72±0.08, cattle 1.13±0.82 μm. The average area of hemidesmosomes of seven kinds of animals are as following: mice 0.03, rabbits 0.04, cats 0.09, dogs 0.05, pigs 3.76, cattle 2.09 μm2.  The diameter and area of hemidesmosomes of BALB/c mice are the nearest to those of human. Conclusions Rabbit cornea is the most similar to human cornea in measured parameters. Therefore, in general, the rabbits have advantage in modeling corneal diseases. (Ophthalmol CHN, 2015, 24: 341-347)

Key words: cornea, animal model, comparison