Electron microscopy and synovial pathology

A review of the histopathological evidence on the pathogenesis of cartilage destruction in rheumatoid arthritis

These are three ways of cartilage destruction as summarized in Fig. 1. The relative significance of the contribution among them to the pathogenesis of cartilage destruction varies individually. It appears important here to note that chondrocytes themselves are not actively involved in the pannus formation. Chondrocytes only provide a basis for extension of the pannus by proteolytic digestion of cartilage matrix. It is however possible in some individuals that the digestion of cartilage by chondrocytes plays the predominant role in their cartilage destruction. Besides the autonomous proliferative potential of pannus tissue, it seems evident that active synovitis is the main cause of cartilage loss. This is quite important from the therapeutic view point, because we can expect to halt the disease process causing joint deformities by controlling the active synovitis.

An ultrastructural and light microscopic study of the synovium in ochronotic arthropathy

The synovium in two well-documented cases of alkaptonuric ochronosis was studied by transmission electron and light microscopy. A feature of alkaptonuria previously unreported in the English-language literature was the presence of phagocytosis of large collagen fibrils by synovial macrophages in both cases. The origin of these fibrils appeared to have been shards of ochronotic cartilage and areas of metaplastic cartilage. This finding suggests that active remodeling of the synovial tissues occurs in advanced ochronotic arthropathy. Numerous shards of ochronotic cartilage were embedded in the synovium. In addition, small aggregates of large collagen fibrils encrusted with apparent ochronotic pigment were occasionally noted in the interstitium. These aggregates of ochronotic collagen are best described as microshards, and they have not generally been recognized in the literature. What appeared by light microscopy to represent ochronotic pigment deposition in interstitial collagen actually represented embedded microshards of ochronotic cartilage in the interstitium. Slender and elongated microshards were most likely to be confused by light microscopy as ochronotic interstitial collagen.

Degradation in vivo of articular cartilage in rheumatoid arthritis and juvenile chronic arthritis by cathepsin G and elastase from polymorphonuclear leukocytes

Peroxidase-anti-peroxidase (PAP) staining and specific antibodies against cathepsin G and elastase from polymorphonuclear leukocytes (PMN) were applied to pannus-free and microscopically intact superficial articular cartilage. Restricted local deposits containing cathepsin G and elastase were found in three of ten patients with seropositive rheumatoid arthritis (RA), in one of three patients with seronegative RA and in one patient with juvenile chronic arthritis (JCA). Similarly, localized deposits of IgG and C3 were found in the patients with seropositive RA and JCA, but not in the patient with seronegative RA. Adjacent sections exhibited esterase activity in and around the PMN. In proteinase-positive areas from patients with seropositive RA the inhibitors alpha 1-proteinase inhibitor (alpha 1-PI) and alpha 2-macroglobulin (alpha 2-MG) were present in two of three and one of three patients, respectively. In JCA only alpha 1-proteinase inhibitor was present, and in seronegative RA no inhibitors were found. No staining of articular cartilage was observed in a patient with psoriatic arthritis. One of three cases with osteoarthritis exhibited patchy superficial staining for IgG only. In articular cartilage covered by pannus, in three patients with seropositive RA, in one with seronegative RA and in the patient with JCA a few regions with variably dense PMN infiltrates were observed. Cathepsin G, elastase and esterase activity were found in and around the PMN. In one of the three patients with seropositive RA the adjacent cartilage-pannus junction exhibited distinct staining for cathepsin G and elastase, but not for IgG/C3 and proteinase inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)

Study of enzyme inhibitors in the rheumatoid pannus-cartilage area

Immunoperoxidase studies were carried out on the pannus-cartilage junction (PCJ) of patients with rheumatoid arthritis (RA) and psoriatic arthritis to investigate the distribution of the enzyme inhibitors alpha 2 macroglobulin (alpha 2 M) and alpha 1 antitrypsin (alpha 1 AT). Comparisons were made with the equivalent synovial cartilage junctional area in osteoarthritis (OA). In all 12 patients with RA, prominent deposits of alpha 2 M and alpha 1 AT were found within the PCJ whereas in OA patients and the case of psoriatic arthritis fewer or no deposits were seen. Inhibitors were localised in pannus synovial lining cells, perivascular inflammatory cells, macrophage and fibroblast-like cells invading the cartilage as well as along the junctional cartilage matrix and in the adjacent pannus-free cartilage. Deposits of immunoglobulins were found in similar areas to enzyme inhibitors. The presence of enzyme inhibitors at the PCJ suggests that this area is not unprotected against enzymatic attack. Thus the concept that pannus is a prime area for cartilage damage because aggressive, invasive cells release destructive enzymes in an environment free from inhibitors should be reviewed.

Polymorphonuclear granulocytes in rheumatic tissue destruction. III. an electron microscopic study of PMNs at the pannus-cartilage junction in rheumatoid arthritis

Metatarsophalangeal and metacarpophalangeal joints from 3 patients with rheumatoid arthritis were investigated electron microscopically with regard to the occurrence of polymorphonuclear granulocytes (PMNs) at the pannus-cartilage junction. In all 3 cases PMNs could be detected at the junction and within the cartilaginous matrix. PMN cytoplasmic processes surrounded collagenous islands in the cartilage. From the morphological findings it is deduced that PMNs are cells capable of destroying cartilage in inflammatory joint diseases, in particular in rheumatoid arthritis.

Ultrastructural localization and in situ analysis of iron, bismuth, and gold inclusions

The purpose of this article is to review ultrastructural and electron probe X-ray analytical studies on metallic deposits in cells. The metals that will be dealt with are iron, bismuth, and gold, mainly because they have been extensively studied in recent years. The nature and chemical composition of endogenously (e.g., from breakdown of autologous blood) and exogenously (e.g., after a transfusion or injection of iron compounds) produced hemosiderin (i.e., iron deposits) has been the subject of time-hallowed controversies. Quite a few of these have now been resolved by ultrastructural studies and the atomic composition of such deposits has been determined by electron probe X-ray analysis. The interest in bismuth centers around the fact that this is one of the two metals (the other being lead) that produces quite large intranuclear inclusions. Here again much has been learned by ultrastructural and X-ray analytical studies. The interest in gold stems from the fact that soluble salts of this metal are used for the treatment of rheumatoid arthritis and current studies with the above-mentioned techniques indicates how gold produces its beneficial and toxic effects.