APMIS 107: 311-7, 1999 Printed in Denmark zyxwvutsrqponm . All rights reserved Copyright Q APMIS 1999 APWUg ISSN 0903-4641 zyx Stereological quantification of mast cells zy in human synovium z TINE ENGBERG DAMSGAARD,' FLEMMING BRANDT S0RENSEN,2 TROELS HERLIN' and PETER OLUF SCHI0TZ' 'Research Laboratory, Department of Pediatrics, and 2Stereological Research Laboratory, University Institute of Pathology, Aarhus University Hospital, Aarhus, Denmark Damsgaard, T. E., Serensen, F. B., Herlin, T. & Schietz, P. 0. Stereological quantification of mast cells in human synovium. APMIS 1999;107:311-7. Mast cells participate in both the acute allergic reaction as well as in chronic inflammatory diseases. Earlier studies have revealed divergent results regarding the quantification of mast cells in the human synovium. The aim of the present study was therefore to quantify these cells in the human synovium, using stereological techniques. Different methods of staining and quantification have previously been used for mast cell quantification in human synovium. Stereological techniques provide precise and unbiased information on the number of cell profiles in two-dimensional tissue sections of, in this case, human synovium. In 10 patients suffering from osteoarthritis a median of 3.6 mast cells/mm2synovial membrane was found. The total number of cells (synoviocytes, fibroblasts, lymphocytes, leukocytes) present was 395.9 cells/mm2 (median). The mast cells constituted 0.8% of all the cell profiles present in the synovium. A significantly positive correlation was demonstrated between the number of mast cells and the total number of cells. Thus, the present study reports stereological quantification of the mast cells and the total number of cells in synovium from patients with osteoarthritis. A possible link between the mast cell and osteoarthritis is discussed upon obtaining a precise estimate of cell profiles in human synovium. Key words: Mast cell; osteoarthritis; stereology. T. Engberg Damsgaard, Research Laboratory, Department of Pediatrics, Skejby Sygehus, Aarhus University Hospital, Brendstrupgaardsvej 100, DK-8200 Aarhus N, Denmark. The mast cell has previously been investigated in various chronic inflammatory diseases such as arthritis zyxwvutsrq (5, 12). This ubiquitous cell has been shown to be present in the arthritic as well as the normal human synovium (5, 7, 11, 12, 14, 21) and has been observed in increased numbers at the site of cartilage erosion in the rheumatoid joint (4). Activation of the mast cell can be obtained by a range of different biological substances, for instance antigen-specific IgE, neuropeptides, cytokines, and sensitized by IgE-rheumatoid factors (1, 13, 19, 20, 26,28). Upon appropriate activation various inflammatory mediators, proteases and cytokines are released from the Received January 5, 1998. Accepted September 14, 1998. mast cell (2, 3, 10, 23-25, 29). Thus, the mast cell possesses the potential to participate in the inflammation seen in early-stage osteoarthritis as well as in cartilage erosion, followed by end- stage chronic synovitis and synovial fibrosis, and may thereby contribute to the clinical mani- festations of arthritis. Previous studies addressing quantification of synovial mast cells have yielded divergent results regarding the number of cells and their distri- bution. The mast cells have been quantified in synovia from patients with rheumatoid ar- thritis, osteoarthritis and other arthritic dis- orders as well as synovia from non-arthritic pa- tients (5, 7, ll, 12, 14, 21). Although these studies have yielded divergent results, a consist- ent finding has been that the number of mast cells is higher in synovia from patients with ar- 31 1