The development of fibrocartilage in the elastic tendon of the chicken wing.

Abstract

The elastic tendon of the chicken wing has five morphologically distinct regions. One of these regions is a distally located fibrocartilage from which fibrous connections extend to the capsule of the distal radius. In adult birds, this region shows the characteristics of a tendon-compressed fibrocartilage, with an accumulation of proteoglycans between thick collagen bundles arranged in a basket-weave formation. Here we study the development of this fibrocartilage in order to of compare it with other tendon fibrocartilages and try to identify the factors involved in fibrocartilage differentiation. This fibrocartilage initially developed by cell enlargement and accumulation of vimentin, with simultaneous deposition of proteoglycans in the extracellular matrix and an increase in the amount and thickness of collagen bundles. Elastic fibers were minor components associated with the collagen bundles. Cells could be classified into two main types. One was typically fibrocartilaginous and the other was fibroblast-like, the latter occurring in close association with the collagen bundles. These results establish the steps in the development of the elastic tendon fibrocartilage and provide a basis for future studies.