Table 2.

Role of Wnt signaling during late stages of cartilage development and adulthood.

Promoting Effects
Wnt-4	Expressed in periphery of joint interzone and hypertrophic chondrocytes Accelerates chondrocyte terminal differentiation Induces terminal differentiation of growth plate cartilage
Wnt8	Promotes chondrocyte hypertrophy
β-catenin high level	Increases cell hypertrophy through RUNX-2 or IHH signaling activation Induces collagen X expression
Inhibitory Effects
Wnt-5aWnt-5b	Inhibits hypertrophic maturation of chondrocytes through NF-κB stimulation and RUNX-2 inhibition
FRZB	Expressed in prechondrogenic mesenchymal condensations and in epiphyseal pre-articular chondrocytes Blocks chondrocyte maturation and prevents endochondral ossification in vivo Promotes glycosaminoglycan synthesis and expression of Sox9 and collagen II in vitro
DKK-1	Expressed at sites of programmed cell death in apical ectodermal ridge Expressed at higher level in articular cartilage than growth plate cartilage Promotes glycosaminoglycan synthesis and expression of Sox9 and collagen II in vitro Inhibits chondrocyte hypertrophy
Fzl1Fzl7	Blocks/delays chondrocyte hypertrophy
sFRP-1sFRP-3	Delays terminal differentiation of hypertrophic chondrocytes