Ultrastructure of Osteoarthritic Articular Cartilage

Abstract

The ultrastructure of 10 osteoarthritic femoral atricular cartilage specimens obtained from patients (52-80years) undergoing total knee replacement and 10 age-matched non-osteoarthritic cartilage specimens obtained from cadavers (51-82years) was studied. The non-osteoarthritic cartilage had chondrocytes having a secretary cell characteristic with prominent nucleus and well developed organelles. With advancing age, the chondrocytes showed cellular processes extending into surrounding matrix. The pericellular matrix showed coarse collagen fibres and a finely filamentous area. Some of the cells contained a lipid drop and electron dense glycogen particles. In the osteoarthritic cartilage most of the cells appeared normal but chondrocytes near the fibrillated surface had dilated and irregular endoplasmic reticulum. Some pinocytotic vesicles, glycogen and lipid bodies were found in most of the chondrocytes. Few apoptotic cells with condensed cytoplasm were also observed. The various cell organelles could not be identified in these apoptotic cells. Electron dense lipid deposits in the cartilage matrix as well as the intracytoplasmic glycogen deposits were much increased in the osteoarthritic cartilage as compared to the control group. Calcium deposits were also seen in between the bundles of collagen fibres. Collection of perinuclear intracytoplasmic fine filaments was present in the chondrocytes near the fibrillated areas. Cell density of the cartilage was also reduced in the osteoarthritic cartilage which is due mainly to the death of chondrocytes in situ since the remains of necrotic cells were observed in the cartilage matrix. In the areas of deep fibrillation, the proliferation of deeper chondrocytes to form abnormal multicellular clusters was seen.