Figure 1
From: Progress in spondylarthritis. Mechanisms of new bone formation in spondyloarthritis
Roles of BMPs and WNTs in endochondral bone formation. (a) Physiological endochondral bone formation is stimulated by bone morphogenetic proteins (BMPs). Wingless-type like (WNT) signaling plays a supportive role in relation to BMPs. However, some WNTs have a negative effect on early chondrocyte differentiation. (b) In the presence of inflammation, tumour necrosis factor (TNF) may stimulate BMP signalling but also the expression of DKK1, which acts a WNT antagonist. The balance between TNF, BMP and WNT signalling may determine the onset and progression of ankylosis. DKK, dickkopf.