Biomechanical properties of regenerated digital flexor tendon in immature newt following complete transection

BackgroundAdult newt (9-month-old) has become an emerging research model to study complete regeneration of injured adult tendon. If younger newts exhibit tendon regeneration similar to adult ones, they can be used as an additional experimental model, assuring a high- throughput of experiments using genetic manipulation owing to shorter period of growing.ObjectiveTo examine mechanical properties and tissue structure of tendon in immature Iberian ribbed newt following complete transection.MethodsDigital flexor tendon of the middle finger of the left hindlimb in 4- and 6-month-old Iberian ribbed newt (4mo and 6mo, respectively) was transected. Regenerated tendon was mechanically tested at 6 and 12 weeks postoperatively. Collagen fiber structure was also observed using two-photon microscopy.ResultsIn both 4mo and 6mo newts, regenerated tendon at 6 weeks exhibited significantly lower tensile strength than corresponding normal tendons and had unorganized collagen structure. At 12 weeks, Regenerated tendon in both groups had the strength comparable to normal controls. Additionally, the collagen structure seemed more organized compared to that at 6 weeks and comparable to controls. These phenomena were essentially similar to those in adult newts.Conclusion4mo and 6mo newts can also be used as experimental models of adult tendon regeneration research.