Tenascin-C and type I and III collagen expression in total Achilles tendon rupture. An immunohistochemical study

Tendon tissue degeneration and changes in collagen composition play a role in spontaneous rupture of the human Achilles tendon. Tenascin-C has been shown to be present in the tissue pathology and changes in tissue loading. We made an immunohistological study of the expression of tenascin-C and type I and III collagens in ruptured human Achilles tendons.

Three tissue samples in ten individuals, one from the Achilles tendon rupture and two control samples from four and sixteen centimeters proximal in same tendon were collected at surgery. The specimen were fixed and labelled with specific antibodies to type I and III procollagens (PICP, PINP and PIIINP), mature type III collagen (IIINTP) and tenascin-C. The amount of reacting tissue was evaluated visually and graded on a semiquantitative scale.

No difference in the expression of tenascin-C was found between the sites. Instead, mature type III collagen content (p=0.008) and type III collagen synthesis (p=0.016) were significantly increased at the rupture site relative to the control site 2. The amount of newly synthesized type I collagen (PINP, PICP) was relatively high at all sites, as expected.

The expression of type III collagen is increased at the rupture site in the human Achilles tendon, but that of tenascin-C remains unchanged. This finding supports a tissue composition alteration background for Achilles tendon rupture, while the role of mechanical loading at the rupture site remains controversial.