Figure 5.

Simplified diagram of EGFR/ErbB1 signaling pathways in MSC physiology. EGFR/ErbB1 ligands activate PLCγ pathway, p42/44 MAPK pathway, and PI3K/Akt pathways in MSCs [3]. PLCγ pathway plays a pivotal role in motogenic activity, whereas p42/44 MAPK pathway plays a key role in mitogenic activity and paracrine activities of certain factors such as VEGF [42, 43, 66, 67]. Sustained and strong activation of p42/44 MAPK pathway exerts cytoprotective and pro-osteogenic effects [44, 47], whereas PI3K/Akt pathway might exert anti-osteogenic effects [46].