Osteogenesis activity of isocoumarin a through the activation of the PI3K-Akt/Erk cascade-activated BMP/RUNX2 signaling pathway

Abstract

Bone formation refers to a series of complex events related to the activities of osteoblasts. In this study, we evaluated the osteogenesis activity of a natural compound named isocoumarin A that was isolated from the rhizomes of Polygonum amplexicaule on the non-transformed preosteoblastic cell line MC3T3-E1 for an in vitro study, and the results revealed that it increased the proliferation and promoted the mineralization of the extracellular matrix of MC3T3-E1 cells after treatment for 3 d in a dose-dependent manner. The cell metabolic activity peaked at 169% at 10 μM, and the activity of alkaline phosphatase (ALP) tripled to 15.94 U/mg compared with the control group. The protein levels of morphogenetic protein 2 (BMP-2), runt-related transcription factor 2 (RUNX2), ALP, and the mRNA levels of ALP, type I collagen (COL-1), and osteocalcin (OCN) were also upregulated after isocoumarin A administration. The mechanism investigation revealed that these effects were associated with the activation of the p-Akt/p-Erk1/2-activated BMP/RUNX2 signaling pathway. Subsequently, the in vivo investigation on the zebrafish embryos model demonstrated that isocoumarin A (0.30 mM) increased the number of vertebrae (5.38 ± 2.07 pcs) and the vertebral area (433.25 ± 111.77 μm2) in the development process of zebrafish embryos after a 7-day postfertilization (dpf) culture compared with the control group (2.50 ± 1.16 pcs and 209.75 ± 86.40 μm2). Together, these results indicated that isocoumarin A could be viewed as a promising candidate in early drug discovery and development to promote the healing of fractures and postmenopausal osteoporosis.