2015 ISAKOS Biennial Congress ePoster #308
Tendon Regeneration Needs Time and Traction Force: Using the Film Model Method
Yoshinori Ohashi, MD, Kanazawa, Ishikawa JAPAN
Junsuke Nakase, MD, PhD, Kanazawa, Ishikawa JAPAN
Hiroyuki Tsuchiya, Kanazawa, Ishikawa JAPAN
Kanazawa University Hospital, Kanazawa, Ishikawa, JAPAN
FDA Status Not Applicable
Summary: Injured tendons produce a gel-like substance, called tendon gel. After traction of the gel, a new band of aligned collagen fibrils appeared, and the gel in the early phase was longer than in the late phase. We suspect that the collagen molecular binding grew stronger with maturation of the tendon gel. Our findings indicate that maturation of the tendon gel was essential for tendon regeneration.
Injured tendons have a self-repairing ability that involves both intrinsic and extrinsic processes. The initial tendon healing phase was recently observed using the film model method. Injured tendons reportedly produce a gel-like substance, or tendon gel, which changes to a regenerated tendon upon mechanical loading. In the present study, we aimed to artificially load tendon gel and observe its dynamic change to a regenerated tendon under light microscopy, as well as with motion imaging and histological evaluation.
We used 20 adult male mice (body weight range, 30–40 g) in this study. In the first step of the film model method, part of the Achilles tendon was transected with fine scissors close to its insertion on the medial head of the gastrocnemius. Then, the proximal and distal ends of the transected tendons were placed 1 mm apart on a sheet of thin plastic film and were anchored facing each other. Finally, the transected tendons were covered with another sheet of film and remained between the films for 10 days (D10) or 15 days (D15) post-tenotomy. On D10 or D15, the mice were sacrificed, the films were removed, and the translucent tendon gel connected to the tendon stump was harvested. The tendon gel underwent traction for 24 h with a draft load of 24.5 × 10-4 N while it was kept moist; this process was captured through light microscopic motion images. After traction, the change in the length of the tendon gel was evaluated between the pre-traction and post-traction periods and compared between groups using Student’s t-tests. Statistical significance was established at p < 0.05. Then, the tendon gels were stained with hematoxylin-eosin (H-E) and Elastica van Gieson (EVG).
Before traction, the tendon gel contained randomly distributed collagen fibrils. After mechanical loading for 24 h, white lines were noted in the edge of the tendon gel in both D10 and D15 groups. On light microscopy, these lines were found to be a new band of aligned collagen fibrils, indicating a regenerated tendon. In the D10 and D15 groups, the lengths of the tendon gels were extended (mean, 0.97 ± 0.40 mm and 0.13 ± 0.83 mm, respectively; p = 0.019). H-E staining did not show new blood vessels or fibrous scar tissue, but indicated the collection of small round cells near the boundary line of the tendon stamps and tendon gel in the D10 group and spread widely throughout the tendon gel in the D15 group. No elastic fibers were detected by EVG staining; however, we noted the collagen fibrils were aligned in each group.
Discussion And Conclusion
After mechanical loading, the tendon gel dynamically changed to a regenerated tendon. The tensile strength of the tendon gel was different between the D10 and D15 groups. We suspect that the collagen molecular binding grew stronger with maturation of the tendon gel. Our findings indicate that maturation of the tendon gel and mechanical loading were essential for tendon regeneration.