A study of microvasculature in normal and inflammatory synovial membranes in the rabbit using light and electron microscopy and freeze fracture.

The Authors made a study of microvasculature in normal and inflammatory synovial membranes in the rabbit, by light and electron microscopy and with the use of freeze fracture. The synovial membrane of the knee was studied in 15 normal rabbits and in 22 rabbits in whom immunization with mycobacterium tuberculosis crude cytoplasmic water soluble extract had provoked inflammatory synovitis. A comparison between normal and inflammatory synovia by light microscopy showed, in inflammatory synovitis, a significant increase in the number of congested and obliterated microvessels (p less than 0.001) and in the number of endothelial nuclei per microvessel (p less than 0.0001). By electron microscopy no specific alteration of synovial microvessels was observed. A significant increase was found in the number of venules in inflammatory synovitis (p less than 0.01). The number of simple interendothelial tight junctions, defined by 1 or 2 interendothelial contacts, and of complex interendothelial tight junctions, defined by 3 or more interendothelial contacts, was similar in venules and in capillaries of inflammatory synovitis and of normal controls. The mean number and mean spacing of junctional strands in interendothelial tight junctions was similar in the microvessels of inflammatory synovitis and of normal controls. The Authors conclude that inflammation does not provoke specific alterations in synovial microvasculature but could induce an adaptative state resulting in increased synovial permeability.