Increased collagenolytic activity in severed and sutured tendons following topical application of exogenous collagen in chickens

Chondroitin sulfate-coated polyhydroxyethyl methacrylate membrane prevents adhesion in full-thickness tendon tears of rabbits

Polyhydroxyethyl methacrylate (pHEMA) membranes coated on one side with chondroitin sulfate (CS) were used to block adhesion physically and to reduce friction between healing flexor tendons and the surrounding tissue in rabbit forepaws after surgical repair. Digits with pHEMA-only, standard tendon sheath repair, and with no sheath repair were the controls. Over 12 weeks the CS-coated membranes were evaluated for joint flexion, adhesion limitation, and tendon healing progress. The membranes initially allowed for better flexion (ie, for 6 weeks), but their relative superior effectiveness faded afterward. Histology showed that adhesions were less severe and healing was better in the CS-pHEMA membranes at 3 and 6 weeks. If further studies determine precise amounts or thicknesses of CS coats that will maximize its healing properties, CS-pHEMA should prove useful in clinical settings in which restoration of tendon sheath integrity with a minimum of adhesions is not possible.

A biomechanical study of tendon adhesion reduction using a biodegradable barrier in a rabbit model

Adhesion formation associated with tendon surgery is a widespread problem in which a healing tendon becomes adherent via scar tissue to surrounding structures such as bone, muscle, skin, tendon sheath, or other tendons. A model is described in which adhesions were generated reproducibly between the plantaris and Achilles tendons of the rabbit using a partial tenotomy, a Bunnel suture, and immobilization. Using this model, the effect of an absorbable barrier, INTERCEED (TC7), on adhesion formation was investigated. This material, which is a fabric comprised of oxidized regenerated cellulose, was found to diminish significantly the extent and severity of intertendinous adhesions, assessed both mechanically and histologically. No evidence of a foreign body reaction was observed.

Topically applied halofuginone, an inhibitor of collagen type I transcription, reduces peritendinous fibrous adhesions following surgery

To test in vivo the effect of previously observed inhibition of collagen type I transcription by the plant alkaloid Halofuginone, deep flexor tendons of 12 chickens were severed and sutured, and Halofuginone was applied topically at the site of surgery. Intact tendons, and severed but untreated tendons served as controls. The effect of the treatment was assessed by histological, biochemical, and biomechanical examinations of the operated and intact tendons three weeks after surgery. The results indicated an almost complete absence of fibrous peritendinous adhesions in the histologic sections of the Halofuginone treated tendons. There was a statistically significant decrease in collagen contents of and in both force and energy required to pull out the Halofuginone treated tendons from their sheath, relative to the untreated controls. Halofuginone had no effect on the cellularity of the healing tissue. We conclude that Halofuginone is a potent inhibitor of fibrous peritendinous adhesions with potentially important clinical applications.

Neutral metalloprotease from tendons

Tendon repair following trauma, rupture, or surgery involves both synthesis and degradation of collagen in order to reweave new collagen bundles in with the old. Using an in situ assay on polyacrylamide gels containing gelatin, we have identified protease activity from tendon tissue and from tendon cells in culture. A population of synovial cells from the epitenon surrounding the tendon as well as the tendon fibroblasts themselves were examined. The cells and the conditioned medium from both cell populations exhibited a major band of gelatin-degrading activity at 70 kdaltons and a minor band of activity at 60 kdaltons. When preparations were reacted with p-aminophenylmercuric acetate (APMA) before electrophoresis, a third band appeared at 63 kdaltons. The main band at 70 kdaltons comigrated with a [35S]methionine-radiolabeled protein band. Inhibitor and pH studies identified the enzymes as neutral metalloproteases requiring disulfide bonds for activity. No proteolytic activity was detected on casein-containing gels, ruling out the presence of stromelysin. Since electrophoresis in the presence of SDS would separate the metalloprotease from the smaller molecular weight inhibitor (TIMP), these in situ assays provide a sensitive screening system for gelatin-degrading enzymes present in tendon without prior removal of TIMP.

Decreased adhesion formation in flexor tendons by topical application of enriched collagen solution--a histological study

In order to improve gliding function of damaged flexor tendons in chickens, we topically applied enriched collagen solution (ECS) to the tendon sheaths of severed tendons. Previous studies using the same experimental model showed improvement of gliding function in the damaged tendons biomechanically and increased collagenolytic activity in the area of the damage after application of ECS. In the present study we evaluated the influence of ECS on peritendinous adhesion formation and on the healing process of the tendons histologically. We found that topically applied ECS reduced adhesion formation, mostly during the first week, without adversely affecting tendon healing or scar maturation.