The development of sites of metaplastic change in regenerating tendon

Summary The development of cartilage and bone in the regenerating segment of the tendon of Achilles following transection has been studied with regeneration taking place in situ, and also following transplantation to a subcutaneous site. Prior to transplantation regeneration was allowed to proceed in situ for various periods of time.It was observed that cartilage and bone develop from the cells of certain pre-cartilaginous areas which represent a metaplasia from fibroblasts. Transplantation to the subcutaneous site at a stage of regeneration when pre-cartilaginous or cartilaginous foci are present leads to the eventual development of bone in the transplant. Transplants made prior to the development of pre-cartilage or cartilage do not show bony metaplasia.It is concluded that the tension of muscle pull is a factor stimulating the metaplastic transformation of fibroblasts to chondroblasts, but once this transformation has occurred the progression to bony metaplasia continues, independently of tension.Supported by a grant from the Medical Research Council of Canada.