Effect of collagen length distribution and timing for repair on the active TGF-β concentration in tendon

Mannose-6-Phosphate Reduces Expression of Transforming Growth Factor β and Receptors in Rabbit Flexor Tendon Tenocytes

Transforming growth factor β (TGF-β) plays an important role in tendon healing and adhesion formation. Inhibiting expression of TGF-β and receptors might prevent adhesion after tendon injury and/or opening surgeries. Here, we aimed to examine the effects of mannose-6-phosphate (M6P), an inhibitor of TGF-β as a natural plant compound, on expression of TGF-β and receptors in tendon sheath fibroblasts, epitenon tenocytes, and endotenon tenocytes that were isolated from rabbit flexor toes. We enriched tendon sheath fibroblasts, epitenon tenocytes, as well as endotenon tenocytes from rabbit flexor tendons, and subsequently cultured these cell types individually. All 3 cell types were grouped into 2 groups randomly: the experiment group supplemented with M6P (the M6P Group), and the Control Group treated with vehicle. Expression of TGF-β and receptors was assessed with enzyme-linked immunosorbent assays. TGF-β1 expression in the mRNA level was also assessed by in situ hybridization and immunohistochemistry. Expression of TGF-β and receptors in the M6P Group was remarkably lower than that in the Control Group across all 3 cell types (P < 0.05). In the M6P Group, the expression ratio of TGF-β1 mRNA and the expression level of intracellular TGF-β1 mRNA in 3 cell types were significantly decreased than those in the Control Group (P < 0.05). Therefore, expression of TGF-β1 was significantly lower in all three types of tendon cell treated with M6P. Collectively, M6P is a negative regulator of TGF-β and receptors in cultured rabbit tendon sheath fibroblasts, epitenon tenocytes, and endotenon tenocytes.

Experimental study of tendon sheath repair via decellularized amnion to prevent tendon adhesion

The adhesion of tendon and surrounding tissue is the most common complication after repairing an injured tendon. The injured flexor tendons in zone II are frequently accompanied by tendon sheath defects, which lead to poor recovery. A variety of biological and non-biological materials have been recently used for repair or as substitute for tendon sheaths to prevent tendon adhesion. However, non-biological materials, such as polyethylene films, have been used to prevent tendon adhesions by mechanical isolation. The possibility of tendon necrosis and permanent foreign body remains due to the lack of permeability and the obstruction of nutrient infiltration. The natural macromolecule amniotic membrane derived from organisms is a semi-permeable membrane with the following characteristics: smooth; without vascular, nerve, and lymphatic; and rich in matrix, cytokines, enzymes, and other active ingredients. The unique structure of this membrane makes it an ideal biomaterial. In the experiment in Henry chicken, the model of tendon sheath defect and the flexor digitorum tendon in zone II was established and randomly divided into control group, medical membrane group, and decellularized amniotic membrane group. Samples were obtained at the 2nd, 4th, 8th, and 12th week after operation. General, histological, and biomechanical tests were performed to investigate the preventive effect of repaired tendon sheath by decallularized amniotic membrane. Experimental results showed the following: the amniotic membrane group and the medical membrane group had mild inflammatory reaction and tissue edema, and nearly no adhesion was observed in the surrounding tissue; the fibroblast-like cells were distributed in layers under the light microscope; the amniotic membrane group was denser than the medical membrane group cells, and numerous fibroblasts were disorganized in the control group. Biomechanical measurements showed that the sliding distance of tendon, the total flexion angle of the toes, and the tendon maximum tensile breaking strength at the early postoperative were significantly better than in the control group. Through this experiment, the amniotic membrane, as a natural biological substitute material in the construction of tendon sheath, can effectively inhibit exogenous healing and promote endogenous healing to prevent tendon adhesion.