Adhesion formation within the equine digital flexor tendon sheath (DFTS) is a major complication of septic tenosynovitis and tendon injury, leading to impaired tendon gliding, persistent lameness, and poor performance outcomes. Fibrin deposition and inadequate fibrinolysis are key drivers of adhesion development, yet targeted fibrinolytic therapies for this condition remain limited. Tenecteplase, a modified tissue plasminogen activator with increased fibrin specificity and stability, represents a promising therapeutic candidate but has not been evaluated in equine tendon sheath–relevant systems.

The objective of this study is to evaluate the in vitro safety of tenecteplase in equine tendon sheath–derived cells and establish a model to evaluate the fibrinolytic potential in synovial fluid. In Aim 1, primary equine synovial fibroblasts and tenocytes will be exposed to a range of tenecteplase concentrations, with cytotoxicity assessed at multiple timepoints. In Aim 2, a fibrin clot formation and lysis assay in a synovial fluid matrix will be developed using a turbidimetric microplate method, adapted from established plasma fibrinolysis assays. Tenecteplase will be evaluated across a clinically relevant concentration range to confirm measurable fibrinolytic activity.

Tenecteplase is expected to demonstrate minimal cytotoxicity and measurable fibrinolytic activity under physiologically relevant conditions. This work will establish a reproducible in vitro platform to support future dose–response and comparative studies of fibrinolytic therapies within a synovial fluid environment. The long-term goal is to optimize safe and effective fibrinolytic therapies to prevent adhesion formation and improve clinical outcomes in horses with DFTS disease. Data generated from this study will support future in vivo investigations and comparative studies evaluating tenecteplase in comparison to other fibrinolytic agents.