The transient chondrocyte phenotype in osteophytic cartilage - a role of PEDF?

Pigment Epithelium-Derived Factor (PEDF) has recently been identified as a factor that is significantly upregulated in late-stage osteoarthritic cartilage in which chondrocytes are confronted with terminal differentiation and cell death. Since PEDF is known to induce cell death of endothelial cells, it may also be responsible for terminal differentiation and cell death in cartilage. Using cDNA microarray analysis, we found PEDF among the factors with the strongest differential expression and significant higher levels (118.5-fold) in osteophytic cartilage compared with articular cartilage. This study explored if PEDF interferes with the stable chondrocyte phenotype by promoting terminal differentiation or cell death.