VARIABILITY IN THE CELL PHENOTYPE OF AGGREGATES OR CLONES OF HUMAN OSTEOARTHRITIC CARTILAGE - A CASE-REPORT

Human samples of articular cartilage from the knee of a clinically cla ssified osteoarthritic patient, assessed by arthroscopy as part of the surgical treatment, was studied by light and transmission electron mi croscopy. This particular case differed from others already reported i n the variability of cell phenotype within the aggregates or ''clones' ' frequently present in the osteoarthritic cartilage. The most common morphology of ''clonal'' cells forming the aggregates were large and r ounded with an euchromatic nucleus. The cytoplasm was characterized by the presence of alternately clear and dense sites. At the ultrastruct ural level it was seen that the clear sites were formed by disrupted i ntermediates filaments and small particles, and that the dense sites w ere constituted by the segregation of different organelles of the chon drocytes. In addition, there were atypical aggregates composed only by secretory cells or by degenerating chondrocytes. Furthermore, a compl ex structure consisting of a very large cell inside a giant lacunae de limited by electron-dense material with small vesicles is described as a novel finding. The variability in the chondrocyte phenotype of the aggregates described here could be an indication of a better prognosis ; nevertheless, the follow-up of the evolution of this patient is need ed in order to know the final outcome.