Ultrastructure of rabbit synovial membrane

Abstract

Recent electron microscopic studies of normal and pathological synovia have given a fresh insight into the structure and function of this tissue. The structure of human (Barland, Novikoff, and Hamer-man, 1962; Roy, Ghadially, and Crane, 1966) and guinea-pig synovium (Wyllie, More, and Haust, 1964) has been studied in some detail, but only brief accounts of normal rabbit synovium can be found in papers dealing with the removal of injected sub-stances from joints (Ball, Chapman, and Muirden, 1964; Cochrane, Davies, and Palfrey, 1965). The rabbit is the largest common laboratory rodent and as such its knee joint has been the subject of much study and many experimental procedures. It is therefore necessary to study and record the ultrastructure of the synovium of this valuable experimental animal in some detail. Material and Methods Synovial membrane was collected from the knee joints of seven normal rabbits weighing between 1,600 and 2,000 g. The animals were anaesthetized with ether. After cutting the suprapatellar tendon and reflecting the patella, a small piece of synovium measuring about 5 x 3 mm. was removed promptly from the infrapatellar region. The tissue was then placed on a piece of filter paper and dropped in buffered cold osmium (Palade, 1952). After fixation for 2 hours at 40 C., the tissue was cut into thin strips about 1 mm. wide. The synovial membrane with a minimum of subsynovial tissue was dissected off the filter paper leaving behind most of the collagenous and fatty tissue which would have inter-fered with the cutting of ultrathin sections. The synovial tissue was then processed according to the method of Glauert (1961) and orientated according to the method of Coulter (1962). Sections were cut with the Porter Blum microtome, mounted on uncoated copper grids, stained with lead citrate (Reynolds, 1963), and examined under the A.E.I. electron microscope using an accelerating voltage of 50 or 75 kV. Another piece of synovium from the same joint of each animal was fixed in formalin and processed for light microscopy with haematoxylin and eosin stain