Premium
Quantification of expression levels of cellular differentiation markers does not support a general shift in the cellular phenotype of osteoarthritic chondrocytes
Author(s) -
Gebhard Pia Margarethe,
Gehrsitz Angelika,
Bau Brigitte,
Söder Stephan,
Eger Wolfgang,
Aigner Thomas
Publication year - 2003
Publication title -
journal of orthopaedic research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1016/s0736-0266(02)00094-3
Subject(s) - cartilage , phenotype , type ii collagen , chemistry , osteoarthritis , microbiology and biotechnology , chondrocyte , cellular differentiation , type i collagen , gene expression , pathology , gene , biology , endocrinology , anatomy , biochemistry , medicine , alternative medicine
Many studies have shown increased anabolic activity in osteoarthritic cartilage and have suggested changes in the cellular phenotypes of articular chondrocytes. Most of these studies relied on non‐quantitative technologies, which did not allow the estimation of the relative importance of the different differentiation phenomena. In the present study, we developed and used quantitative PCR assays for collagen types I, II(total), IIA, III, and X as marker genes indicating cellular synthetic activity (collagen type II) as well as differentiation pattern of chondrocytes (collagen types I, IIA, III, and X) and quantified these genes in normal, early degenerative, and late stage osteoarthritic cartilage in parallel. At first sight, our results confirmed previously published data showing hardly any expression of collagen genes in normal and significantly enhanced expression in osteoarthritic cartilage. This included collagen types II, III, and IIA, but also collagen types I(α1) and X. However, if one considers the ratios of the various markers of chondrocytic differentiation in comparison to collagen type II, the main synthetic product of differentiated chondrocytes, no shift in the cellular phenotype was detectable. In fact, expression ratios remained constant or were even decreased in osteoarthritic cartilage. Our results confirm that normal adult human articular chondrocytes display hardly any expression activity of the collagen types investigated, whereas osteoarthritic chondrocytes show very increased synthetic activity. The largely unchanged ratios of collagen subtypes investigated indicate that no general shift in the cellular phenotype does occur in osteoarthritic cartilage as suggested by previous investigations. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.