The Effect of Amniotic Membrane Transplantation on Tendon-Healing in a Rabbit Achilles Tendon Model

Extracellular matrix scaffolds have been examined for the repair of tendon rupture and biological materials have been reported to be promising in terms of promoting fast and natural healing by host cells with concurrent resorption of the materials. The present study investigated the healing effect of amniotic membrane, as a biological extracellular matrix scaffold, on the ruptured Achilles tendon in a rabbit model. Ten rabbits were allocated to histological evaluations at zero, two, four, and six weeks and thirteen rabbits were allocated to biomechanical studies at the same periods. Both hindlimbs underwent surgery, with one hindlimb serving as a control for the other. A partial transverse laceration through the lateral two thirds of the midsubstance of the Achilles tendon was made and left unrepaired. For the experimental limb, the laceration site was wrapped with amniotic membrane. Histological evaluation was performed with use of hematoxylin and eosin stain and immunohistochemical stain for collagen type I and III. Tensile force of the tendons was tested for biomechanical analysis and modulus was calculated. Macroscopically, there was no definitive difference in peritendinous adhesion and the cross-sectional areas of the laceration sites between two groups (p>0.05). Histologically, inflammatory response was the most apparent at two weeks in both groups and cellularity of inflammatory cells at two weeks was significantly lower in the treatment group, including neutrophils (p<0.05), mononuclear cells (p<0.05), and total cell count (p<0.05). The collagen type I and III structures were more organized in the treatment group, especially at six weeks. Biomechnically, the modulus of the tendons at four weeks was significantly higher in the treatment group (p<0.05). In conclusion, amniotic membrane enhanced maturation of the histological organization of the fibroblasts and collagen fibers, and improved the material property of the lacerated tendons in the early healing period.