Myofibroblasts in the accessory ligament (distal check ligament) and the deep digital flexor tendon of foals

Objective-To demonstrate myofibroblasts in the accessory ligament of the de ep digital flexor tendon tie, distal check ligament) and deep digital flexo r tendon of clinically normal feats. Sample Population-Tissue specimens from 25 foals that were necropsied for r easons unrelated to this study and unrelated to musculoskeletal disease. Procedure-The distal check ligament and deep digital flexor tendon of both forelimbs were examined histologically. Myofibroblasts were identified by i mmunohistochemical staining specific for alpha-smooth muscle actin (alpha - SMA). Results-Most of the cells in the distal check ligament and deep digital fle xor tendon of all foals stained positive for alpha -SMA. Conclusion and Clinical Relevance-Myofibroblasts made up most of the cells in the distal check ligament and deep digital flexor tendon of clinically n ormal foals. These cells have contractile ability and therefore, may play a role in flexure contracture of these tendons. The ability of tetracycline to chelate calcium or decrease the expression of the contractile protein al pha -smooth muscle actin could inhibit the myofibroblasts' ability to contr act, thus providing a rationale for tetracycline administration as a treatm ent of distal interphalangeal joint flexor deformity in foals.