Generation of an Immortalized Chondrocyte Cell Line from Osteoarthritis Articular Cartilage

Purpose: Primary human articular chondrocytes tend to senesce and lose their phenotype in vitro after a few passages. Chondrocyte cell lines available have been generated from cartilage sources different from synovial joints, and their usefulness for articular cartilage research is limited. For these reasons, the aim of this study was the generation of an immortalized chondrocyte cell line derived from the articular cartilage of a patient with osteoarthritis (OA). Methods: Primary OA articular chondrocytes were transduced with SV40 large T antigen (SV40LT) and telomerase reverse transcriptase (hTERT) by spinoculation employing retrovirus produced by Phoenix Amphotropic cells. Expression of SV40LT and hTERT in transduced chondrocytes was tested by immunofluorescence. Proliferative capacity and senescence were tested. The ability of transduced chondrocytes to produce a cartilage-like tissue and to respond to IL-1β was analysed. Results: An immortalized OA articular chondrocyte cell line was generated. Both transgenes were co-expressed in the nuclei of transduced chondrocytes. Immortalized chondrocytes acquired a high proliferation potential and showed no signs of senescence. Immortalized chondrocytes were able to form three-dimensional aggregates similar to those formed by primary OA articular chondrocytes, but failed to produce cartilage-like tissue. Immortalized chondrocytes retained the ability to respond to IL-1β stimulation in a similar way to primary chondrocytes, unlike the non-articular chondrocyte T/C28a2 cell line (Figure 1). Conclusions: OA articular chondrocytes were successfully immortalized by SV40LT and hTERT transduction. Immortalized chondrocytes acquired the ability to overcome senescence in vitro, but unable to form cartilage-like tissue under the tested conditions. However, this cell line might be useful for OA research, due to their ability to up-regulate inflammatory mediators in response to IL-1β similarly to primary OA articular chondrocytes.