Ultracytochemistry of glycosaminoglycans in the canine knee synovium

The accurate localization and nature of glycosaminoglycans (GAGs) in the canine knee synovium were studied by ultracytochemical methods that involved high or low iron diamine-thiocarbohydrazide-silver proteinate (physical development) staining in combination with enzyme digestion control procedures. The results obtained indicated that heparan sulfates and hyaluronan were present mainly in the plasma membrane of the B (fibroblast-like) cells. In contrast, the plasma membrane of the A (macrophage-like) cells showed negative reactions after the histochemical examination. Dermatan sulfates, chondroitin sulfates (A and/or C) and hyaluronan were localized in the extracellular matrix of the synovial intima, whereby dermatan sulfates were confined to the fibrous component, whereas chondroitin sulfates and hyaluronan were found in the interfibrous matrix. Heparan sulfate was the only notable GAG molecular species localized in the basement membrane of the capillary wall. It is obvious that differences in the quality and localization of glycosaminoglycans in the canine synovial tissue are of specific interest in understanding normal functions as well as pathological alterations of the knee synovium in mammals.