Intracellular collagen fibres in regenerating tendon.

Intracytoplasmic collagen fibres contained in elongated membrane-bound structures were observed in fibroblasts of regenerating tendon in the later stages of the repair process. The observations appear to support the hypothesis that collagen fibres of the intercellular matrix may be phagocytosed by the cells and degraded in the intracellular environment. Phagocytosis of extracellular collagen fibres probably represents an additional mechanism of collagen resorption during the later stages of remodelling of the regenerating tendon.