Fig. 5

Atsttrin-mediated anabolic effect in chondrocyte primarily depends on TNFR2-Akt/Erk1/2 signaling. a Atsttrin-mediated GAG synthesis largely depended on TNFR2. Mouse femoral head cartilage cultured with or without addition of Atsttrin for 7 days, measured by GAG synthesis assay. b, c Transcriptional levels of aggrecan (ACN) and type II collagen (Col II). Primary chondrocytes were isolated from WT, TNFR1^–/–, and TNFR2^–/– mice, cultured in absence or presence of Atsttrin, and transcriptional levels measured by real-time PCR. d Atsttrin strongly activated Akt signaling and slightly activated Erk1/2 signaling in WT and TNFR1^–/– chondrocytes, but lost this activation in TNFR2^–/– chondrocytes. e, f Transcriptional levels of ACN and Col II in chondrocytes. Chondrocytes were isolated and cultured without or with Atsttrin in absence or presence of 1 μM Erk1/2 signal blocker U0126. g, h Transcriptional levels of ACN and Col II in chondrocytes. Chondrocytes were isolated and cultured without or with Atsttrin in absence or presence of 1 μM Akt signaling blocker Wortmannin. I, j Transcriptional levels of ACN and Col II in chondrocytes. Chondrocytes were isolated and cultured without or with Atsttrin in absence or presence of 1 μM U0126 and Wortmannin. Values are mean ± SEM of six mice. *p < 0.05, **p < 0.01 versus WT or PBS group. Con control, NS not significant, PBS phosphate-buffered saline, WT wildtype, TNFR tumor necrosis factor receptor, Wort Wortmannin