Osteoporosis is a reduction in skeletal mass because of the loss of osteoblastic activity or an increase in osteoclastic activity. The survival of osteoblast cells plays a crucial role in the development of osteoporosis. Asperosaponin VI (ASA VI) is a kind of saponin in the medicinal herb Dipsacus asper Wall which has long been used as an antiosteoporosis drug. The assay of cell proliferation, alkaline phosphatase (ALP) activity and measurement of mineralized matrix, showed that ASA VI exhibited a significant induction of proliferation, differentiation and mineralization in MC3T3-E1 and primary osteoblastic cells. Induction of differentiation by ASA VI was associated with increased bone morphogenetic protein-2 (BMP-2), indicating that BMP-2 is essential in ASA VI to mediate osteoblast maturation and differentiation. In addition, ASA VI may induce differentiation by increasing the activity of p38 and ERK1/2. In conclusion, ASA VI may induce osteoblast maturation and differentiation, and then increase bone formation via increasing BMP-2 synthesis, and activating p38 and ERK1/2.
RTS treatment can effectively suppress the loss of bone mass induced by OVX and in vitro evidence suggests this could be through actions on both osteoblasts and osteoclasts.
Radix Dipsaci total saponins (RTS) are primary active components of Radix Dipsaci, which is administered orally for the treatment of osteoporosis according to Chinese Medicine. RTS have also been shown to reduce the risk of bone fractures in rats. However, the detailed molecular mechanisms underlying their action remain elusive. In the present study, the ability of RTS to increase alkaline phosphatase activity, osteocalcin levels and the degree of mineralization was investigated in MC3T3‑E1 mouse osteoblast precursor cells. In addition, the associated molecular mechanism was detected. The results revealed that RTS exerted an effect on osteoblastic maturation and differentiation. Induction of differentiation by RTS was associated with an increase in the expression levels of bone morphogenetic protein‑2 (BMP‑2), phosphorylated (P)‑Smad1/5/8, P‑ERK1/2, P‑p38 and Runt‑related transcription factor 2 (Runx2). Blocking BMP‑2 expression with noggin significantly reduced the levels of osteoblastic differentiation and subsequently attenuated the expression levels of P‑Smad1/5/8, P‑ERK1/2, P‑p38 and Runx2. This indicated that RTS induced osteoblastic differentiation through BMP‑2/mitogen‑activated protein kinase/Smad1/5/8‑dependent Runx2 signaling pathways and that it may be a promising agent for enhancing bone formation.
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