Immunohistochemistry of the extracellular matrix of the normal equine lamina cribrosa.

This research aims to identify and locate the structural molecules within the extracellular matrix (ECM) of a healthy adult horse’s lamina cribrosa – a structural part of the eye. By examining these details, the researchers hope to find comparison points to horses suffering from glaucoma. The study found the lamina cribrosa in a regular horse contained collagen, laminin, elastin, and fibrillin, with the most intense presence being collagen. Comparisons indicate that the structure of the equine lamina cribrosa is similar to that of a dog, and may provide protection for the optic nerve during periods of increased eye pressure.

Methods

• The study made use of five healthy adult horses aged between 5 and 10. The horses’ eyes were fixed in a neutral buffered formalin at 10 percent and embedded in paraffin.
• Rabbit-derived polyclonal antibodies were used against human elastin, laminin, fibrillin-1, and three types of collagen, while goat-derived polyclonal antibodies were used against one type of collagen. These antibodies constituted the primary antibodies for the study.
• Histologic sections from the lamina cribrosa and optic nerve head were stained using primary antibody dilutions, a biotinylated link antibody, horseradish peroxidase-labeled streptavidin, and a chromogen. The researchers then interpreted these staining patterns qualitatively.

Results

• The lamina cribrosa in the horses’ eyes showed positive labeling for several types of collagen, as well as elastin, laminin, and fibrillin.
• Among these, the most intensely stained was type VI collagen. This was followed by types III and I.
• In terms of blood vessels on the lamina, they tested weakly positive for laminin and slightly positive for type IV collagen.
• Additionally, the ECM found at the point where the lamina attaches to the sclera had more intense labeling for types I and VI collagen than the lamina plates themselves.

Conclusions

• The lamina cribrosa of the adult horse is similar to that observed in dogs. It contains both elastic and collagen fibers, with the most predominant type being type VI collagen.
• However, both the normal horse and dog lamina feature more intense staining of type VI collagen than the normal human lamina cribrosa.
• The robust macromolecular structure of the equine lamina cribrosa suggests that it may offer some protection to the optic nerve axons during periods of elevated eye pressure.