Salvianolic Acid B Prevents Bone Loss in Prednisone-Treated Rats through Stimulation of Osteogenesis and Bone Marrow Angiogenesis

Abstract

Glucocorticoid (GC) induced osteoporosis (GIO) is caused by the long-term use of GC for treatment of autoimmune and inflammatory diseases. The GC related disruption of bone marrow microcirculation and increased adipogenesis contribute to GIO development. However, neither currently available anti-osteoporosis agent is completely addressed to microcirculation and bone marrow adipogenesis. Salvianolic acid B (Sal B) is a polyphenolic compound from a Chinese herbal medicine, Salvia miltiorrhiza Bunge . The aim of this study was to determine the effects of Sal B on osteoblast bone formation, angiogenesis and adipogenesis-associated GIO by performing marrow adipogenesis and microcirculation dilation and bone histomorphometry analyses. (1) In vivo study: Bone loss in GC treated rats was confirmed by significantly decreased BMD, bone strength, cancellous bone mass and architecture, osteoblast distribution, bone formation, marrow microvessel density and diameter along with down-regulation of marrow BMPs expression and increased adipogenesis. Daily treatment with Sal B (40 mg/kg/d) for 12 weeks in GC male rats prevented GC-induced cancellous bone loss and increased adipogenesis while increasing cancellous bone formation rate with improved local microcirculation by capillary dilation. Treatment with Sal B at a higher dose (80 mg/kg/d) not only prevented GC-induced osteopenia, but also increased cancellous bone mass and thickness, associated with increase of marrow BMPs expression, inhibited adipogenesis and further increased microvessel diameters. (2) In vitro study: In concentration from 10 −6 mol/L to 10 −7 mol/L, Sal B stimulated bone marrow stromal cell (MSC) differentiation to osteoblast and increased osteoblast activities, decreased GC associated adipogenic differentiation by down-regulation of PPARγ mRNA expression, increased Runx2 mRNA expression without osteoblast inducement, and, furthermore, Sal B decreased Dickkopf-1 and increased β-catenin mRNA expression with or without adipocyte inducement in MSC. We conclude that Sal B prevented bone loss in GC-treated rats through stimulation of osteogenesis, bone marrow angiogenesis and inhibition of adipogenesis.

Salvianolic acid B stimulates osteogenesis in dexamethasone-treated zebrafish larvae

“…Excessive Dex can evoke osteoporosis by depressing osteoblastic bone formation in humans and higher vertebrates. Excess GC also inhibits osteoblast differentiation and bone nodule formation in bone marrow stroma stem cells [1] , consistent with our previous studies [16] . Furthermore, previous reports indicate that GC induces the inhibition of osteogenesis in zebrafish larvae 21 , consistent with our present results.…”

“…Our previous study [16,18] showed that Sal B in vitro promoted bone marrow stromal cell differentiation into osteoblasts, increased osteoblast activity and decreased GC associated adipogenic differentiation. Moreover, an aqueous extract of Radix Salviae miltiorrhizae, of which the main ingredient is Sal B, prevented GC-induced bone loss [16] .…”

“…Our previous study [16,18] showed that Sal B in vitro promoted bone marrow stromal cell differentiation into osteoblasts, increased osteoblast activity and decreased GC associated adipogenic differentiation. Moreover, an aqueous extract of Radix Salviae miltiorrhizae, of which the main ingredient is Sal B, prevented GC-induced bone loss [16] . Our data from this study showed that Sal B increased bone formation at concentrations ranging from 0.2 to 2 μmol/L in a dose-dependent manner by promoting osteoblastic differentiation and bone matrix mineralization in zebrafish larvae, consistent with our previous findings in vitro [16,18] .…”

“…Moreover, an aqueous extract of Radix Salviae miltiorrhizae, of which the main ingredient is Sal B, prevented GC-induced bone loss [16] . Our data from this study showed that Sal B increased bone formation at concentrations ranging from 0.2 to 2 μmol/L in a dose-dependent manner by promoting osteoblastic differentiation and bone matrix mineralization in zebrafish larvae, consistent with our previous findings in vitro [16,18] . Importantly, Sal B ranging from 0.5 to 10.0 μmol/L attenuated the decrease of osteoblast differentiation and bone matrix mineralization induced by Dex in a dose-dependent manner, particularly at 2 μmol/L.…”

“…As a polyphenolic acid compound with seven phenolic hydroxyl groups, Sal B is one of the strongest natural antioxidants [14,15] and is metabolized in vivo into tanshinol, another aqueous bioactive ingredient of Salvia miltiorrhiza and a strong natural antioxidant containing two phenolic hydroxyl groups ( Figure 1). Interestingly, our previous studies demonstrated that both Sal B and tanshinol promoted osteoblastic differentiation and functions in vitro, and the aqueous extracts of Salvia miltiorrhiza, of which the major components are Sal B and tanshinol, effectively prevented osteopenia in rats treated with long-term excessive prednisone [16][17][18] .…”