Are matrix and vascular changes involved in the pathogenesis of deep digital flexor tendon injury in the horse?

This study investigates if there are changes in the blood vessel frequency, proteoglycan staining intensity, and matrix composition of the horse’s deep digital flexor tendon (DDFT) in cases of chronic foot pain. The results show that horses with chronic foot pain had increased blood vessel frequency, increased proteoglycan staining intensity, and altered matrix composition, which might indicate degenerative changes.

Research Method

• The research took samples from the DDFT of 10 mature horses that were age-matched. Among these, one group of horses (Group L) had a history of chronic foot pain, while the other group (Group N) had no history of forelimb lameness.
• The samples were examined using a histological analysis of sections stained with haematoxylin and eosin to determine the frequency and location of blood vessels.
• The matrix proteoglycan was assessed semi-quantitively using safranin 0 fast green staining.
• The blood vessels’ frequency and immunoreactivity were judged using factor VIII immunolocalisation.

Research Findings

• The results showed a higher frequency of blood vessels and increased proteoglycan staining intensity in Group L compared to Group N.
• Micro-anatomical differences in the matrix and tenocytes were observed between the two groups.
• There was decreased factor VIII staining within the vascular structure of horses in Group L as compared to Group N, suggesting alteration in vascular composition.

Significance and Conclusions

• The altered matrix composition in the DDFT of horses in Group L suggests that chronic foot pain could potentially be linked with degenerative changes.
• The increase in blood vessel frequency may be a reparative response to a degenerative tendonopathy. This could point towards the body’s attempt to heal the degenerative process in the tendon.
• The findings provide crucial insights into possible pathogenesis of DDFT injury in horses, which may assist future research into the diagnosis, prevention, and treatment of related conditions.