Fig. 7: The 4-1BB-p38 MAPK-Dkk1 signaling pathway in BMSCs of aged mice.

When 4-1BBL binds to 4-1BB on BMSCs from aged mice, 4-1BB signaling is activated so that p38 MAPK is phosphorylated. DKK1 expression is upregulated in response to p38 MAPK phosphorylation. DKK1 blocks Wnt/β-catenin signaling pathway and then dampens the BMSC osteogenic differentiation potential of aged mice.