SUBMICROSCOPIC STRUCTURE OF THE HUMAN JOINT CARlUAGE AND SYNOVIAL MEMBRANE IN OCHRONOSIS

Horky D.: Submicroscopic Structure of the Human Joint Cartilage and Synovial Membrane in Ochronosis. Acta vet. Bmo,.50, 1981: 131-156. Using a transmission electron .lInd Sc8nning electron microscope the joint cartilage and synovial membrane were studied in 5 persons of the age from 30 to 55 years. In its majority the superficial cartilage layer is absent due to arthritic changes caused by the deposition of granules of ochronotic pigment in the intercellular substance of the cartilage. In regiOns with It well-preserved cartilage distinct sings of arthrosis are evident on its surface. In the cytoplasm of chondrocytes of the middle layer vesicleS appear filled with ochronotic pigment in variOus stages of polymerization. The aperiodic fibres which penetrate into· the proximity of the chondrocytes multiply so that the pericellular matrix disappears. A small amount of· granules ofthe ochronotic pigment is deposited in this area; whereas in the intercellular matrix they appear in a large amount both in the form of granules and in layers deposited between thick collagen fibres. In the deep . layer there are signs of degeneration of chondrocytes. In the cytoplasm autophagic vacuoles occur formed by pigment granules, secondary lysosomes, lipid droplets and cOncentrically layered membranes of the granular endoplasmic reticulum. In the scanning electron microscope deep defects are distinctly evident on the sUrface and empty chondrocyte capsules with mound-like contoured edges. Both oil the bottom of these capsules and on the surface of the cartilage deposited are crystals of ochronotic pigment, cell debris and solitary cells. Short sections of the synovial membrane are covered with a confluent layer of cells of a transient type. No pigment occurs in the thus arranged synovial membrane. The major part of the synovial membrane surface is pigment with a layer of intercellular substance in which granules of oChronotic covered are deposited. Nearer to the surface the synovialocytes resemble fibrocytes and small amounts. of granules of pigment occur in' their cytoplasm. Synovialocytes situated deeper are of intennediary type and in their cytoplasm pigmen!; is deposited in the form of large deposits of. as much as 2 pm in size. Man,ochronosis, joint cartilage, synovial membrane, ochrOnotic pigment. Alkaptonuria is II' relatively rare disorder of amino acid metabi>lism with reCessive heredity characterized by the excretion products of urine degradation. In some. cases homogentisic acid is one of the products of this degradation deposited in tissues. This condition' is defined asochronosis. The disease is caused by a defect of oxida:seof homogentisic acid (;LaDu et al. 1958, 1966) and the disorder occurs in tyJ;'osine metabolism.' . . . . OChronosis was described for the first tbrie by Virchow (1866) on necrotic material. In 1!)22 Albrecht recognized the connection between alkliptOl!1uria and ochronosis. 'Following this period a nUlllber of studies were published dealing. with this disorder of tyrOsinemetabo!ism. A I:eview of biochemical aspects oftqe. disease and its clinical manifestations is given in the stlWies ofC ervenansky et al. (1959) and Jaffe (1972). . " . '" .. ' '.' .' '. . .. '. Morphological data are incomparably . rarer; The fu:st more detailed info.rmation was given by Pope (1906) see Laskarand Sa'rgison (1910). Kleinschmidt (1922), Garrod (1923), Hertz.blu;g (1945), Lichtenst.einand l<aphm (1954), Cooper andMQran. (1957), O'Brien