Different Expression of Fibronectin and Tgf-Beta in Adhesion and Adhesion Free Tendon Repairs

Principal Investigator: Peter C. Amadio, M.D.
Project Coordinator: Chunfeng Zhao, M.D. — zhao.chunfeng@mayo.edu

Figure 1: Immunolocalization of FN (x400) (a) The epitenon cell layer covering the lacerated portion had dense positive staining of FN in group A. (b) Positive staining of FN was observed in the epitenon cell layer of the intact tendon.

Flexor tendon healing is often complicated by the formation of adhesions despite early active motion protocols. It is well known that migrating fibroblasts are responsible for adhesion formation, however, the pathophysiology of adhesion formation is not well understood. Fibronectin (FN) and TGF-beta are major contributions of adhesion formation. Our aim in this study was to compare the expression of FN and TGF-beta type I receptor (RI) in tendons healing with and without adhesions. Histology & Immunohistochemistry were performed on specimens from a canine study of flexor tendon healing 21 days after repair. We subdivided the specimens into groups that had no adhesions, significant adhesions, and contralateral control. Immunohistochemical analysis consistently demonstrated positive staining for FN and RI.

Figure 2: Observation of adhesion (a: x40; b,c,d,e: x400). (a) HE staining showed single cellular adhesion (left square) and sheet-like cellular adhesion (right square) between tendon (T) and surrounding tissue (S). (b) Epitenon in the left square of figure 6a had expression of FN. (c) FN expressed in migrated fibroblasts in the right square of figure 3a. (d) Epitenon cells in the left square of figure 6a had expression of TGF-beta type I receptor (RI). (e) RI was detected on migrated fibroblasts in the right square of figure 3a.

A large amount of FN was observed in the thick epitenon and in the epitenon cells in the group with no adhesions and in the control group (Fig. 1). Epitenon cells and fibroblasts were labeled for FN and RI in group with significant adhesions. It appears that FN and RI are upregulated in the epitenon in those tendons with heavy adhesion formation (Fig. 2).