Immunohistochemical study of matrix metalloproteinases-2 and -9, macrophage inflammatory protein-2 and tissue inhibitors of matrix metalloproteinases-1 and -2 in normal, purulonecrotic and fungal infected equine corneas.

The research examines the roles of certain proteins – matrix metalloproteinases (MMPs)-2 and -9, macrophage inflammatory protein-2 (MIP-2), tissue inhibitors of matrix metalloproteinase (TIMP)-1 and -2 in corneas of horses that are affected by fungi and those that are purulonecrotic (dead tissue accompanied by pus formation). The study reveals that these proteins can provide insights into the development of fungal keratitis in horses.

Research Methodology

• The scientists worked with equine corneal samples that were preserved in paraffin. They segregated the samples into three categories — normal corneas, corneas infected with fungi (FA) and corrupt purulonecrotic corneas (PN) that were not infected with fungi.
• To explore the presence and impacts of proteins MMP-2, -9, MIP-2, TIMP-1, and -2, they performed immunohistochemical analysis on these samples. Additionally, they counted the number of immune-reactive inflammatory cells in the samples.
• Western blot method, a well-established technique in biochemistry and molecular biology to detect proteins in a particular sample, was used to confirm the existence of all four proteins – MMP-2, MMP-9, TIMP-1 and TIMP-2.

Key Findings

• All the targeted proteins – MMPs-2, -9, MIP-2, TIMP-1 and -2 showed significant immune-reactivity in the corneal epithelium of normal corneas, along with the epithelium, inflammatory cells, keratocytes and vascular endothelial cells of both problematic FA and PN samples.
• Both the FA and PN samples contained a significantly higher count of inflammatory cells when compared with the normal corneas.
• The results revealed a crucial correlation among the indicated proteins in inflammatory cell immune-reactivity. Both the FA and PN samples showed significantly correlated interactions among these proteins.
• Western blot analysis confirmed the presence of the targeted proteins in the corresponding samples.

Conclusions and Implications

• The research highlights the increased immune-reactivity of MMPs -2 and -9 in the FA and PN samples which indirectly tips towards the role of MIP-2 in attracting neutrophils, an important part of the immune system.
• The study also points out that matrix metalloproteinase tissue inhibitors, TIMP-1 and TIMP-2, are up-regulated in purulonecrotic and fungal keratitis, following the expression of MMP-2 and MMP-9.
• The perceivable correlation among the proteins may indicate a specific role they could be playing in the development of fungal keratitis in equines.