BEP - Tendons & Ligaments

The effect of collagenase IV on the degradation rate of collagen in relation to the strain state within porcine tendons

Eliane van Hoef

Porcine tendons have been tested for their mechanical properties. Based on their properties, three regions are assigned: low stiffness region, transition region and high stiffness region. The project investigated whether MMPs influence the degradation kinetics of tendons per assigned region.

A typical knee injury is rupture of the anterior cruciate ligament (ACL). Due to the limited healing capacity of the ACL, patients often get a graft to replace the ruptured ACL. Although these reconstructions are considered to be a successful procedure, 5%-30% of the patients suffer with post-operative problems. In vivo, the graft undergoes a remodelling process, in which the graft transforms into an ACL. However, mechanical properties, that decrease during the process, never recover to native ACL levels, i.e. only to 50%-60% of the native ACL. The purpose of this project is to find out if matrix metalloproteases (MMPs) influence the degradation kinetics of tendons in a strain-dependent manner. It is hypothesized that degradation is elevated in the toe region (low strains), almost zero in the transition region (intermediate strains), and slightly elevated again in the high stiffness region (high strains). To gain insight into the mechanical properties of the porcine tendons, a failure test was done. Afterwards a contralateral set of samples was used for a stress-relaxation test. The samples were submerged in a collagenase IV solution or in PBS. Obtained data suggests that there is a relationship between the applied stretch to a tendon and the degradation rate of collagen, in agreement with the hypothesis. This could imply that during ACL reconstructive surgery, the amount of pre-tension applied is crucial for post-operative remodeling speed, which should be studied in more detail.