Expression of Toll-like receptors 2, 3, 4, 6, 9, and MD-2 in the normal equine cornea, limbus, and conjunctiva.

This study aims to identify the presence of TLRs 2, 3, 4, 6, 9, and MD-2 in healthy horse eye tissues, which could provide insights into the mechanism behind fungal keratitis and possibly aid in developing new treatment methods for equines and humans alike.

Research Problem and Aim

• The problem this research addresses is rooted in the study of Toll-like receptors (TLRs) present in human corneal cells. Notably, TLRs 2 and 4 are the main receptors that identify and respond to the patterns associated with fungal invasion in humans.
• As such, this research aimed to determine if the same TLRs, along with others (3, 6, 9) and MD-2, were expressed in equine (horse) eye tissues, including the cornea, limbus, and conjunctiva. This was a step towards understanding how these receptors might interact during an instance of infectious keratitis, primarily fungal keratitis.

Methods

• Eye tissues were collected from seven horses that had been euthanized and showed no signs of eye disease.
• After collecting the samples, RNA extraction was carried out with the inclusion of DNase-1 digestion. This process was then followed by RT-PCR, a common molecular biology technique used to amplify the amount of a specific RNA. This procedure was employed to determine the expression of the target TLRs and MD-2.
• The final products of these procedures were then subjected to electrophoresis, a technique used to separate and visualize the desired substances, using an agarose gel of 1.5% concentration.
• The resulting bands from the electrophoresis were then visualised via ethidium bromide staining.

Results

• The researchers found that TLRs 2, 3, 4, 6, 9, and MD-2 were present in the cornea, limbus, and conjunctiva of each horse.
• However, the expression of TLR3 was not observable in the dorsal and ventral conjunctiva tissues of one horse.

Implications

• These findings confirm the presence of TLRs in healthy equine eye tissues. Therefore, it could add to our understanding of their function in the pathogenesis of fungal keratitis, including the development of new treatment protocols for both equines and humans.
• The expression of TLRs in the equine eye tissues also highlights the potential for these samples to serve as a model for human fungal keratitis.
• Additional studies researching the combined expression of TLRs and their respective induced cytokine profile during equine fungal keratitis could deepen our understanding of the progression of this disease.