Computed microtomographic imaging of revascularization during healing of Achilles tendon injury

Angiogenesis in injured tendons may contribute to regeneration, but quantifying it post-injury has been mostly limited to 2D semi-quantitative histology. This study aimed to develop micro-CT as a 3D tool to quantitatively assess tendon blood vessels in an experimental animal model. Adult male Wistar rats (N = 36) had injuries induced in their Achilles tendons by needle insertion. The study included three post-injury groups: 12 hours post-injury (12H), 3 weeks post-injury (3W), and 8 weeks post-injury (8W). The uninjured left Achilles tendon served as the control for each group. Intravital cardiac perfusion with barium sulfate enhanced contrast between tendon and vasculature. Micro-CT imaging was performed on dissected tendons in proximal, middle, and distal regions to assess total volume, object count, and structural thickness from 3D reconstructions. Control tendons showed region-specific and age-related vascular changes, with a significant portion of blood supply originating from the muscle-tendon junction. Injury-induced vascular changes were detected by 3D micro-CT analysis. The 12H, 3W, and 8W groups exhibited increased total volume, structural thickness, and object volume in all tendon regions compared to controls (p < 0.05). Structure separation was also higher in the middle and distal regions of these groups (p < 0.05). Micro-CT combined with intravital contrast perfusion allows for 3D quantification of Achilles tendon angiogenesis, revealing a significant and sustained increase in vascularity post-injury, making it a valuable tool for studying vascularization during tendon injury and repair.