Establishment of in vitro cell culture models for the investigation of the pathogenesis of cartilage diseases

Abstract

The investigation of cartilage abnormalitiesin vitrois hampered by the limited amount of available tissue. Thus, the chondrocytes have to be isolated and amplified in cell culture prior to a detailed biochemical analysis. However, it is well-known that chondrocytes dedifferentiate during extensive monolayer culture, losing not only their typical morphology but also changing their biosynthetic repertoire. The cells start to express collagen type I instead of the cartilage specific collage type II and shift to a more fibroblast-like phenotype [1, 2]. In addition to these well-established molecular markers for the chondrocyte phenotype, we have recently demonstrated that collagen type IX as well as non-collagenous matrix proteins, such as the cartilage oligomeric matrix protein (COMP), are downregulated very rapidly [3]. Although the function of some of these marker proteins remain to be elucidated, their presence might be of critical importance for the cartilage specific behaviour of the cells. To overcome the downregulation or even loss of chondrocyte-specific proteins, a variety of three-dimensional matrices, e.g., agarose, alginate or other complex polymers which stabilise or even re-induce the chondrocytic phenotype after dedifferentiation have been established [3–5]. The influence of a surrounding three-dimensional matrix on functional aspects is underscored in recent transplantation experiments in rabbits using chondrocytes embedded in alginate and agarose [6, 7]. For the development of ourin vitrocell culture model, we have chosen the following approach (Fig.1): directly after isolation, the primary articular chondrocytes were provided with the gene of interest and either maintained in a short-term monolayer culture or embedded directly after isolation into an alginate matrix and cultured for several weeks.KeywordsAlginate BeadCell Culture ModelCartilage Oligomeric Matrix ProteinCartilage Oligomeric Matrix ProteinPrimary ChondrocytesThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.