Structural changes in intercellular junctions during keratinization of the stratum medium of the equine hoof wall.

The research article investigates the structural changes that occur in interconnected cells during the keratinization of the stratum medium in the hoof wall of horses. It notes the formation of three distinct junctions and the leakage of acid phosphatase, suggesting these changes lead to stable adhesion between fully keratinized cells.

Research Context

• The research focuses on the intertubular horn of the stratum medium of the equine hoof wall. These are specific cells in the horse’s hoof, which undergo a process called keratinization, essential in the development and strengthening of the hoof.

Type of Junctions Identified

• The study identifies three kinds of cell junctions: desmosomes, gap junctions, and septate-like junctions. Desmosomes and gap junctions were present across all strata. The septate-like junctions and an intercellular line, however, were observed in the distal stratum spinosum after the extrusion of the contents of membrane-coating granules. The authors suggest that these junctions facilitate the process of keratinization.

Role of Acid Phosphatase

• In the later stage of keratinization, a non-membrane-bound acid phosphatase reaction product is noted to leak into the intercellular space. However, it does not enter areas occupied by septate-like junctions and the intercellular line. Acid phosphatase is an enzyme known to play a role in various biological processes including the process of keratinization, thus its exclusion from certain areas is noteworthy.

Proposed Hypothesis

• The paper presents the hypothesis that the formation of septate-like junctions and the intercellular line, prior to the leakage of acid phosphatase into the intercellular space, creates stable areas of intercellular adhesion between fully keratinized cells. It essentially implies that these structural changes aid in the formation and stability of the horse’s hoof.