Histomorphological Study of the Meibomian Glands in New Zealand White Rabbits (Oryctolagus cuniculus): A Light Microscopic Investigation

Abstract

Background and Objective: The meibomian glands are specialised holocrine sebaceous glands that are encapsulated within the tarsus of the eyelids in domestic animals. The secretion of these glands, called meibum, is important for the stability of the precorneal tear film and for the health of the ocular surface. While the clinical and veterinary significance of these glands has been established, there are no detailed histological or morphometric studies available for New Zealand White rabbits (Oryctolagus cuniculus). The objective of this study was to identify the histomorphological features of meibomian glands in this breed and to provide quantitative morphometric data related to the number of meibomian glands between eyelid positions (i.e. upper and lower) and between male and female rabbits. Materials and Methods: Eyelid specimens were collected from ten clinically normal New Zealand White rabbits (5 males, 5 females; 10-14 months old; 3-5 kg) immediately after slaughter. The specimens were fixed in 10% buffered formalin for 72 hours and processed using standard histological techniques. Tissue sections (5µm) were stained using the Hematoxylin and Eosin (H&E), Periodic Acid- Schiff (PAS), and Masson's Trichrome staining protocols and examined with a light microscope. Results: The mean number of meibomian glands from both the left and right upper eyelids (27.4±0.3 and 26.8±0.4) was significantly greater (P<0.001) than the mean number of meibomian glands from both the left and right lower eyelids (21.3±0.2 and 20.6±0.2). No significant differences in laterality or sex were observed. Histologically, the meibomian glands contained multiple branched acini leading into short ductules that connected to one central excretory duct. Lipocytes in the meibomian glands contained numerous cytoplasmic vacuoles, consistent with holocrine secretion. PAS staining revealed a continuous basement membrane around the meibomian glands, and Masson's Trichrome staining demonstrated collagen surrounding the ducts. Conclusions: The histomorphological features of meibomian glands in New Zealand White rabbits are similar to those reported in other domestic species and differ from those reported for other domestic species. These findings provide baseline reference data for veterinary ophthalmology researchers and for clinicians who provide services to laboratory animal species.