Submicroscopic Structure of Synovial Membrane in the Adult Pig

Abstract

Acta vet. Bmo 60,1991: 3-13.The synovial membrane of adult pigs was investigated. Samples were obtained from hip joints of pigs of both sexes at 15 to 24 months after birth. The tissues were processed in the routine manner to be examined by light and transmission electron microscopy.The synovial membrane in adult pigs involved two types of synovialocytes, A and B, which were arranged on its surface in 2 to 3 layers. Type A cells near the surface presented as single cells while B cells formed small clusters. These contained. apart from typical fully differentiated cell types, also transient A-B types which had all characteristics of A cells together with bodies corresponding in size and appearance to secretory granules of B cells. The cytoplasm of both A and B cells showed the presence of intracytoplasmic filaments. Type A cells had the basal membrane while in type B cells this was absent.Near the membrane surface the fibrillar component of synovial matrix consisted of collagen fibrils which, in areas penetrated with synovialocyte projections, were unmasked and protruded into the articular cavity. In surface layers, aperiodic filaments were prevailing while towards deeper layers increasing numbers of typical collagen fibrils running in various directions were observed. Aperiodic collagen fibrils penetrating through the B-cell membrane were seen repeatedly. When approaching the cell membrane they attained a periodic appearance. SynOfJial membrane, A, B, A-B synOfJialocytes, matrix synuvialisThe synovial membrane plays a major role in both physiology and pathology of the joint. This has been a reason for thorough studies of its building units, i.e. cells and intercellular matter. Even though these building elements have been investigated for nearly 250 years (Hunter 1743 -see Ghadially 1983), the information is still incomplete. At first attention was given to the synovial membrane of adults in experiments with mammalian animal species and later in man. Many authors have studied and described the microscopic structure of synovial membrane under physiologic, experimental and pathologic conditions (for review see Horky 1981; Ghadially 1982). The present trend, which is to gain a deeper insight into its structure and particularly into the development of its functions in relation to advancing differentiation, makes the use of young unmature animals including embryos (for review see Horky 1984.The submicroscopic structure, histochemical and cytochemical properties, and immunohistochemical characteristics have been reported under physiologic and pathologic conditions in different mammalian and avian species (Langer and Huth 1960; Barland et a1.1962;Cutlip and Cheville 1973;Horky et a!. 1975;Fell et al. 1976; Linek and Porte 1978; Horky 1981 Horky , 1984Ghadially 1982; Okada etal. 1981; Tofft and Ef'fendy 1985; Karatzias et al. 1986; Gaines et a1. 1987;Itokazu et al. 1988;Lukoschek et al. 1988) and others. These observations revealed the presence of two types of synovial cells in the synovial membrane of all the species...

The Ultrastructure of Equine Synovial Membrane

“…These bodies were also observed in the synovial matrix close to the membrane surface and it is suggested that they are released into the articular cavity where they may, for instance, take part in the digestion of cartilage intercellular matter (Dingle 1984). In contrast to our earlier observations (Horky 1990(Horky , 1991 as well as the literature data, the synovial membrane in the horse did not have the transient A-B cell types. A further difference is the finding of intracytoplasmic ftlaments which are not present in the synovial membrane of cattle (Horky 1984) or pigs in early postnatal periods (Horky 1990).…”

“…A further difference is the finding of intracytoplasmic ftlaments which are not present in the synovial membrane of cattle (Horky 1984) or pigs in early postnatal periods (Horky 1990). In both cell types, the basement membrane, absent in the pig (Horky 1990(Horky , 1991, was developed. In B-cells, we failed to detect the penetration of collagen fibrils through the cell membrane of B cells.…”

“…The synovial membrane, its structure and function has so far received considerable attention (reviewed by Ghadially 1983;Horky 1990Horky , 1991 and the studies in various mammalian species have been concerned with joint under physiological conditions as well as with those affected by disease (Gangel 1984;Hilbert et al 1984;Worral et al 1991). This abundance of information, however, has contained only few data related to the In describing the cells (synoviocytes) we followed the original classification of Bar I and et al 1962).…”

“…Equine synovial membrane is also mentioned in the work of Gangel (1984) and Hilbert et al (1984) dealing with the properties of synovial fluid. These facts and our long-term involvement in studies on synovial membranes (Horky 1990(Horky , 1991(Horky , 1993) have led to a decision to investigate this structure in the horse and thus contribute to information on this articular component in this mammalian species.…”