O1093 CELLULAR REGENERATION DURING CALLUS DISTRACTION

Abstract

Aims: The purpose of this study was to describe the histologic adaptation of the femoral artery wall to the strechtening derived from femoral lengthening by callus distraction. Methods: In 32 New Zealand white rabbits a left femoral bone lengthening was carried out with a total distraction of 30% of initial length. The study was divided into eight progressives stages and at the end of each stage both femoral arteries were excised and prepared for light microscopy and ultrastructural analysis. Results: Light microscopy: Changes in the media layer architecture were observed since lengthening of the 15% of the initial length, reaching its maximum by lengthening of 30% of initial length. Six month after the end of the distraction, the media layer still showed morphologic changes compared to the unlengthened group. U.E.: During the greatest distraction period and one month thereafter the Smooth Muscle cells of the media lost its contractile characteristics and greatly increased their syntesis organelles, and mytosis and isolated binuclear cells are observed representing and accelerated cell proliferation. Six months after the end of the distraction the muscular cells returned almost completely to the normal contractile state. Conclusions: The response of the arterial wall against the strechtening is more a regenerative response due to the muscle cells than a reparative response of the connective tissue. This study suggest that with the greatest distraction, and one month later, the muscle cells change from the original contractile phenotype to a synthetic phenotype, that is a prerequisite for cellular proliferation. The return to the original characteristics six months thereafter could support the reversibility of the cellular phenotype opposite to the progressive elongation.