Fig 1: The decrease of BMP circulating concentration and the deficiency of BMP/Smad signaling in IDD patients. (A-F) Serum concentrations of BMPs. Circulating levels of BMP1 (A), BMP2 (B), BMP3 (C), BMP4 (D), BMP5 (E), and BMP7 (F) were measured in serum samples obtained from healthy controls (n = 20) and IDD patients (n = 20). *P < 0.05 and **P < 0.01. (G) The protein levels of BMP/Smad signaling molecules. Total cell extracts from the IVDs in one control and different Pfirrmann grades (I-IV) were subjected to immunoblots to examine the protein levels of BMPR1a, BMPR1b, BMPR2, Smad1/5/8, pSSmad1/5/8, Smad4, and β-Actin (loading control).