Lactoferrin Suppresses Loss of Corneal Epithelial Integrity in a Rabbit Short-Term Dry Eye Model

Abstract

Human tear fluid contains lactoferrin at the highest concentration. In patients with dry eye such as Sjogren's syndrome, the concentration of lactoferrin in the tears is approximately half the normal value. The present study utilizes a short-term rabbit dry eye model to evaluate if lactoferrin containing eye drops can reverse any of the damage produced by blockage of blinking with an ocular speculum. Damage was evaluated based on the extent of methylene blue staining in histological sections. After 3 h of desiccation, the amount of extractable dye recovered following sacrifice increased by more than 4-fold in the vehicle-treated eyes. However, in those rabbits treated with 1% lactoferrin, dye recovery was only 40% of the value in the vehicle-treated eyes. Between 1-3 h and over a concentration range from 0.01 to 1% lactoferrin, the decreases in staining were both time and concentration dependent. Alternatively, if 1% lactoferrin was applied during the desiccation period, there was partial restoration of corneal epithelial integrity. These results suggest that lactoferrin may be of therapeutic value in decreasing the loss of corneal epithelial integrity in dry eye.

Lactoferrin Expression by Bovine Ocular Surface Epithelia: A Primary Cell Culture Model to Study Lactoferrin Gene Promoter Activity

“…The level of tear LF in dry eye patients inversely correlated with the Rose Bengal staining score, an indicator of the severity of ocular surface damage in these patients [10] , thus pointing to a possible protective role of LF. A similar indication came from a study conducted on a short-term dry-eye rabbit model, in which the extent of ocular surface damage was much reduced in eyes treated with LF solutions [11] . Therefore, it is of medical interest to understand the regulatory mechanisms governing the production of LF by epithelial cells, and in particular it is an interest of ophthalmology to see whether ocular surface epithe-…”

Age-related Defects in Ocular and Nasal Mucosal Immune System and the Immunopathology of Dry Eye Disease

“…For experimental study of DED characteristics, a rabbit model is more suitable, because it presents decreased tear secretion and ocular surface changes, has a longer lifespan, and offers greater accessibility to the ocular surface tissues. 122–136 For studying specific causes of DED, such as defects of neuronal reflex loops, environmental changes, or evaporative DED, the rabbit model appears to recapitulate many underlying pathophysiologic mechanisms observed in humans. Because of the large exposed ocular surface in rabbits compared with mice, standard DED clinical tests, such as tear breakup time and fluorescein or rose Bengal staining of the ocular surface, can be much more easily performed in rabbits.…”

“…A short-term rabbit model for hyperevaporative DED has been created by preventing rabbits from blinking through the placement of lid specula or sutures. 122–136 After 2 h of desiccation induced by lid specula, dry spots appear on the rabbit corneal epithelial surface and stain with methylene blue. Because of the acuteness of the induced DED and the use of anesthetics (which themselves can decrease tear secretion), this rabbit model is not optimal for studying KCS pathogenesis, which is a chronic event.…”

“…We selected rabbits because numerous similarities exist between the rabbit and human ocular and nasal immune system in both homeostasis and inflammatory diseases 34,36,91,93,125,161–170 : (1) several immune-mediated ocular surface diseases, including inflammatory DED are similar in rabbits and humans 91,93,170,171 ; (2) rabbit conjunctiva-associated lymphoid tissues (CALT) closely resemble the human CALT 172–175 ; (3) similar to humans, rabbit palpebral conjunctiva contains an abundance of conjunctival lymphoid follicles (CLF) 173,176 ; (4) from a practical standpoint rabbits possess relatively large conjunctival surfaces and lacrimal glands offering abundant ocular mucosal tissue for immune cell studies; (5) because of the large exposed ocular surface in rabbits compared to mice, standard DED clinical tests, such as tear breakup time and fluorescein and rose bengal staining, can be much more easily performed in rabbits; (6) for practical reasons, surgical closure of the nasolacrimal ducts (NLDs) to determine the role of NALT in inflammatory DED is much easier in rabbits than in mice 122–136 ; and (7) during the past several years we have been studying the rabbit ocular mucosal immune system (OMIS). 93,95 We recently found that conjunctiva from young rabbits contains an abundance of functional T reg cells that produce anti-inflammatory cytokines, such as IL-10 and TGF-β, and suppress excessive ocular surface-resident Th1 CD4 + T-cell responses 93,177 (Figures 4 and 5).…”

“…We and others are developing an experimental rabbit model of DED that uses a desiccation-controlled room that allows low humidity and high airflow, which increases tear evaporation and leads to the clinical signs of DED. 122–136 Using this novel rabbit model and armed with the necessary rabbit immunological expertise and reagents, we are now poised to investigate the immune mechanisms of age-related deterioration and dysregulation of the OMIS that lead to inflammatory DED, and the role of NALT in inflammatory DED.…”