Phenotypic Characteristic Reference The synthesis of the cartilage proteoglycan biomarker, aggrecan, as well as synthesis of small leucine-rich proteoglycans, decorin and biglycan was confirmed 37 High-density cultures express the cartilage-specific transcription factor, SOX9 38 IL-1β activated ERK1/2, p38 and JNK resulting in increased COX-2 and PGE2 synthesis 39 Expression of functional adiponectin (ApN) receptors 40 PGE2 stimulated TLR4 synthesis while activating ERK1/2, PI3K/Akt, PKA/CREB and NF-κB resulting in IL-6 gene expression 41 PGD2/15d-PGJ2 down-regulated TLR-4, while up-regulating caveolin-1 resulting in inhibition of PGE2-dependent ERK1/2, PI3K and PKA activation 41

Table 1: Some major phenotypic characteristics of t/c28a2 juvenile human chondrocytes.