Matrix metalloproteinase 13 loss associated with impaired extracellular matrix remodeling disrupts chondrocyte differentiation by concerted effects on multiple regulatory factors (original) (raw)

Methods. MMP-13 expression was ablated in primary human chondrocytes by stable retrotransduction of short hairpin RNA. The effects of MMP-13 knockdown on key regulators of chondrocyte differentiation (SOX9, runt-related transcription factor 2 [RUNX-2], and ␤-catenin) and angiogenesis (vascular endothelial growth factor [VEGF]) were scored at the protein level (by immunohistochemical or Western blot analysis) and RNA level (by real-time polymerase chain reaction) in high-density monolayer and micromass cultures under mineralizing conditions. Effects on cellular viability in conjunction with chondrocyte progression toward a hypertrophic-like state were assessed in micromass cultures. Alterations in SOX9 subcellular distribution were assessed using confocal microscopy in micromass cultures and also in osteoarthritic cartilage.