Development of a biocomposite to fill out articular cartilage lesions. Light, scanning and transmission electron microscopy of sheep chondrocytes cultured on a collagen I/III sponge

The regenerative capacity of hyaline articular cartilage is limited. Thus, lesions of this tissue are a pro-arthrotic factor, and up to now the conser vative treatment of cartilage lesions and arthrosis does not yield satisfyi ng results. Therefore, autologous transplantation of articular chondrocytes is being investigated in a variety of different assays. The aim of our stu dy was to create a mechanically stable cell-matrix implant with viable and active chondrocytes which could serve to fill out articular lesions created in the knees of sheep. For this purpose, articular cartilage was collected from knee lesions, chondrocytes were liberated enzymatically and seeded in culture flasks and cultured till confluency. Cells were then trypsinized a nd grown on a type I/III collagen matrix (Chondro-Gide(TM) Geistlich Biomat erials, Wolhusen, Switzerland) for 3, 6 and 10 days before being fixed and embedded for electron microscopy by routine methods. Scanning electron micr oscopy was performed after dehydration in acetone, critical point drying an d sputter-coating with gold-paladium, Light microscopically, clusters of chondrocytes can be seen on the surface of the matrix with a few cells growing into the matrix. Transmission electr on microscopic photographs yield a rather differentiated chondrocyte-like a ppearance, which is evidence of a matrix-induced redifferentiation after de differentiation during the growth period in the culture flasks. Scanning el ectron microscopic results show large, flattened chondrocytes without signs of differentiation on plastic, whereas chondrocytes grown on the Chondro-G ide(TM) sponge show a more roundish aspect wrapping firmly around the colla gen fibrils, exhibiting numerous contacts with the matrix. This cell-matrix biocomposite can now serve to fill out articular cartilage lesions created in the knees of sheep.