Immunohistochemistry to assess glycosaminoglycan distribution. Cartilage sections immunohistochemically stained for (a,b) chondroitin-4-sulphate and (c,d) chondroitin-6-sulphate. Repair tissue from autologous chondrocyte implantation (ACI)-treated patients with the highest (a) (22-year-old) and lowest (b) (52-year-old) levels of chondroitin-4-sulphate measured by fluorophore-assisted carbohydrate electrophoresis (FACE). Biopsies of cartilage from a 22 yr old ACI patient (c) and its age-matched control (d) immunostained for chondroitin 6-sulphate. The pattern of immunostaining in repair tissue from the ACI-treated patient (c) with the highest levels of chondroitin-6-sulphate as measured by FACE demonstrated a pericellular pattern, similar to that seen in the age-matched cadaveric control tissue but there was also more widespread matrix staining (d).