A novel in vitro model to investigate behavior of articular chondrocytes in osteoarthritis.

OBJECTIVE

To investigate in vivo simulation of the microenvironment in which osteoarthritis (OA) chondrocytes are cultured in vitro.

METHODS

Human articular chondrocytes were cultured under normoxic and hypoxic conditions. Cells were cultured on standard culture plastic or a porous polyHEMA surface that closely resembles the in vivo cartilage microarchitecture. Morphological changes to the cells were demonstrated by fluorescent staining with DAPI and vinculin. Proteoglycan and type II collagen protein levels were assessed using established techniques. Matrix metalloproteinase-1 (MMP-1) production was assessed by ELISA. The gene expression of type II collagen and SOX9 was measured using real-time polymerase chain reaction.

RESULTS

Cells grown on culture plastic were seen to be flat and hexagonal. Cells cultured on the porous polyHEMA surface exhibited morphology in keeping with the in vivo microenvironment. Glycosaminoglycan release in hypoxia was high from cells cultured on standard culture plastic. Transcriptional expression of type II collagen was upregulated in hypoxia and by culture on the polyHEMA surface. Transcriptional expression of SOX9 in hypoxia was upregulated compared to normoxia; no significant effect was seen by varying the culture surface. Translational expression of type II collagen was upregulated at 20% oxygen on the polyHEMA surface compared to culture plastic and this was related to MMP-1 expression.

CONCLUSION

Culture of chondrocytes in hypoxia and on a porous surface simulates the in vivo microenvironment and illustrates the molecular mechanisms of OA.