Untersuchungen zum Vorkommen und zur Phänotypisierung von Mastzellen in der Synovialmembran von Hunden mit chronischen Arthritiden

The aim of the present study was to examine the occurrence of mast cells (MC) and the expression of immunoglobulin E (IgE) and of histamine receptor 4 (H4R) in the synovial membrane of dogs for obtaining knowledge about their possible involvement in the synovitis of dogs with cranial cruciate ligament (CCL) rupture and of dogs with chronic polyarthritis (PA). Formalin-fixed and paraffin-embedded synovial membrane samples from 35 dogs with CCL rupture (3 groups: mild, moderate and severe synovitis), from six dogs with PA and from eight control dogs with grossly and histopathologically normal knee joints were examined using a metachromatic staining method (kresylechtviolet, KEV) and a combined immuno- and enzyme-histochemical double labelling technique for detection of chymase and tryptase. KEV-positive MC and chymase-positive, tryptase-positive and both proteases containing MC (MCC, MCT, MCCT) were quantified and the results were evaluated statistically. Additionally, the synovial membrane samples were examined immunohistochemically for IgE- and H4R-positive cells. MC were found in the synovium of control dogs, of dogs with CCL rupture and in dogs with PA. In comparison to control dogs, dogs with CCL rupture had statistically significant more MC. In dogs with CCL rupture, mostly MCC, and in decreasing counts, MCT and MCCT were present. The finding that significantly more MCC were present in dogs with CCL rupture being associated with an increased degree of inflammation suggests that the protease chymase leads to an increase of the permeability of blood vessels thereby supporting the influx of inflammatory cells into the synovium. Also in dogs with polyarthritis MCC were the most frequently present mast cells type while MCT and MCCT were found less frequently. However, significant differences between control dogs and dogs with PA were not found which is possibly due to the small number of PA cases examined. In comparison with control dogs a higher number of IgE-and H4R-positive MC was detected in dogs with CCL rupture and PA, although the results were only statistically significant in dogs with CCL rupture. On the basis of the present investigations, the possible relevance of these findings concerning the devopment and persistence of synovitis in these dogs is not clear.