Observations on the adult sternoclavicular joint and the neonatal costochondral junction in acquired and genetic disorders

• Main Author: Ghasemi, Nasrin
• Published: University of Manchester 2003
• Subjects: 616.7
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521491

The precise aetiopathogenesis of human osteoarthritis is still a matter of debate and controversy despite the fact that knowledge of many aspects of the disorder has dramatically increased in the past several decades. Human diarthrodial joints are complex structures and it has become very clear that different joints show variations in the prevalence, degree and intraarticular anatomical locations of the osteoarthritic process. The present studies were undertaken to determine the features of osteoarthritis exhibited by the human sternoclavicular joint. This joint is superficial in the body and readily accessible. It is sufficiently small to allow a relatively easy complete examination and is complex by virtue of its surface topologies and its intraarticular disc. Although the joint is, strictly speaking, not weight-bearing, in the human all movements of the upper limb result in transmission of forces across the joint. An unselected series of right and left sternoclavicular joints was collected at post-mortem examination. Whole and partial joint preparations were made for histological, histochemical, irmnunohistological and lectin histochemical studies. A particular use was made of large format photomicrographs to enable the observation and annotation of the features of osteoarthritis. A full range of features from normality to severe osteoarthritis was present in the series. Histochemical techniques were applied to detect the presence and distribution of glycosaminoglycans and collagen in different parts of the whole normal joint and those affected by osteoarthritis. Changes in disease were detected and recorded with a general reduction in glycosaminoglycans and collagen distribution. The histopathology of the osteoarthritis was graded by the histological-histochemical grading system as proposed by Mankin et al (1971). Mild to moderate changes were combined in one grade because differentiation between them was very difficult. According to this modified grading system 18 cases were normal, 44 had severe osteoarthritis and 58 cases showed mild to moderate osteoarthritic changes. The presence of clones of chondrocytes was the most common osteoarthritic change in sternoclavicular joints (76 cases) suggesting an attempted repair process. Lectin histochemistry was applied by the use of an extended panel of lectins to produce glycoprofiles of the cartilages in normal and diseased joints. This approach builds a detailed picture of the presence and distribution of the smaller molecular weight glycans in the cartilage. There is very little information about these potentially important structures in normal and osteoarthritic tissues. Differences in glycosylation patterns were observed and recorded. Chondrocytes of normal and osteoarthritic articular cartilage showed similar patterns of expression of the N-glycans especially high mannose and complex residues. However there were differences in the intensity of staining between normal and osteoarthritic cartilage indicating that either the quantity of glycans expressed or their accessibility were different. The matrix of the articular cartilage of the sternoclavicular joints showed reactions with a number of the lectins (HHA, PSA, LCA, e-PHA, UEA-I, MAA, EGA, PNA, DBA and MPA) due to the presence of high mannose and complex N-glycans with terminal mannose, fucose (terminal and core), terminal N-acetylglucosamine and N- or O-glycans with terminal beta galactose. However, the intensity of the lectin staining was different between normal and osteoarthritic cartilage. A higher intensity of lectin staining was seen in mild to moderate osteoarthritis compared to normal articular cartilage, perhaps because of attempted repair processes. Severe osteoarthritic cartilage showed less intensity of staining overall and this might be because of higher degradative enzyme activity. N-acetylgalactosamine (alpha1,3 linked as shown by DBA) was present in normal articular cartilage but absent from osteoarthritic cartilage. Moreover, N or O-glycans with beta-galacotyl termini (as shown by EGA) were present in osteoarthritic cartilage and absent in normal cartilage especially middle and deep zones. Therefore, DBA and EGA are potential good markers in distinguishing normal from osteoarthritic articular cartilage.