Evaluation of heat shock protein (HSP) 27, 72 and 73 expression and apoptosis in normal and dyschondroplastic pig articular cartilage

This study was carried out to investigate the role of Heat Shock Proteins (HSPs) andapoptosis in normal articular cartilage and in the pathogenesis of dyschondroplasia, adisease characterized by a failure of chondrocyte differentiation. Four normal and eightdyschondroplastic medial humeral condyles of abattoir pigs, were processed forhistopathological and histochemical (Alcian Blue, Masson's trichrome) investigations.Immunohistochemical expression of HSP27, 72 and 73 was determined using astreptavidin-biotin-peroxidase technique. Apoptosis was evaluated performing TUNELmethod. A strong HSP27 immunoreactivity was detected within the hypertrophiedchondrocytes, in normal and dyschondroplastic articular cartilage, in clusters ofproliferating chondrocytes adjacent to areas of chondrolysis, as well as islands ofpersisting denatured cartilage. None or weak immunoreactivity was detected againstHSP72 and HSP73. Few TUNEL-positive chondrocytes were present in thehypertrophied layer of control samples; these positive cells seemed to increase indyschondroplastic samples, while there were no positive cells in islands of persistingcartilage. Although preliminary, our results seem to remark the important role of HSP27and apoptosis in swine articular cartilage metabolism and in the pathogenesis of swinedyschondroplasia: HSP27 functions in chondrocyte proliferation, differentiation,mechanical stress response and it could have a cytoprotective role in chondrocytes,protecting them against apoptosis.[...]