Search

Objective: Icaritin, one effective metabolite of Herba Epimedii-derived flavonoid icariin, has a strong osteogenic activity. However, its action mechanism remains unclear. Since primary cilia have been shown to play a pivotal role in regulating the osteogenesis, we hypothesized primary cilia are indispensable in mediating icaritin osteogenic effect., Materials and Methods: Primary rat calvarial osteoblasts were transfected with siRNA1 targeting intraflagellar transport protein 88 (IFT88), a protein required for ciliogenesis, to prevent formation of primary cilium and were treated with 10 -6  M icaritin., Results: Alkaline phosphatase (ALP) activity was significantly increased after 3 days in cells transfected with scrambled siRNA control and treated by icaritin (SC+I group) compared to cells transfected with scrambled siRNA control only (SC group). ALP activity after IFT88 siRNA1 transfection and icaritin treatment (siRNA1+I group) was significantly lower than that of SC+I group. Formation of ALP positively stained colonies after 6 days, osteocalcin secretion after 9 days and formation of calcified nodules after 12 days displayed a similar tendency among the three groups. mRNA expression of osteogenesis-related genes ALP, BMP-2, COL1α, RUNX-2 and OSX after 24 h was significantly increased in SC+I group, but was not different with SC group in siRNA1+I group. Protein levels of BMP-2, COL1α, RUNX-2 and OSX after 48 h showed the similar tendency with gene expression., Conclusion: Primary cilia are important in mediating icaritin-stimulated osteogenic differentiation and may be a novel target for pharmacological therapies for bone loss.

Pulsed electromagnetic fields (PEMFs) have been considered as a potential candidate for the prevention and treatment of osteoporosis, however, the mechanism of its action is still elusive. We have previously reported that 50Hz 0.6mT PEMFs stimulate osteoblastic differentiation and mineralization in a primary cilium- dependent manner, but did not know the reason. In the current study, we found that the PEMFs promoted osteogenic differentiation and maturation of rat calvarial osteoblasts (ROBs) by activating bone morphogenetic protein BMP-Smad1/5/8 signaling on the condition that primary cilia were normal. Further studies revealed that BMPRII, the primary binding receptor of BMP ligand, was readily and strongly upregulated by PEMF treatment and localized at the bases of primary cilia. Abrogation of primary cilia with small interfering RNA sequence targeting IFT88 abolished the PEMF-induced upregulation of BMPRII and its ciliary localization. Knockdown of BMPRII expression level with RNA interference had no effects on primary cilia but significantly decreased the promoting effect of PEMFs on osteoblastic differentiation and maturation. These results indicated that PEMFs stimulate osteogenic differentiation and maturation of osteoblast by primary cilium-mediated upregulation of BMPRII expression and subsequently activation of BMP-Smad1/5/8 signaling, and that BMPRII is the key component linking primary cilium and BMP-Smad1/5/8 pathway. This study has thus revealed the molecular mechanism for the osteogenic effect of PEMFs., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objective: To study whether low-frequency pulsed electromagnetic fields promotes the differentiation of cultured rat osteoblasts through the cAMP/PKA signal pathway., Methods: Rat calvarial osteoblasts isolated by enzyme digestion were exposed to 50 Hz 0.6 mT low-frequency pulsed electromagnetic field for varying lengths of time, and the concentration of cAMP and levels of phosphorylated PKA in the cells were assayed. In cells treated with DDA to inhibit the activity of adenylate cyclase, the changes of ALP activity and transcription of osteogenic gene were detected after exposure to low-frequency pulsed electromagnetic field. The changes of osteogenic gene transcription and protein expression were tested in the osteoblasts pretreated with KT5720 in response to low-frequency pulsed electromagnetic field exposure., Results: The intracellular cAMP concentration in the cells increased significantly at 20 min during exposure to low-frequency pulsed electromagnetic field, began to decrease at 40 min during the exposure, and increased again after a 2-h exposure; the same pattern of variation was also observed in p-PKA level. Application of DDA and KT5720 pretreatment both suppressed the increase in ALP activity and osteogenic gene transcription induced by electromagnetic field exposure., Conclusion: Low- frequency pulsed electromagnetic field exposure improves the differentiation of cultured rat osteoblasts by activating cAMP/PKA signal pathway.

Objective: To establish a collagen hydrogel three-dimensional culture model with rat calvarial osteoblasts (ROBs)., Methods: ROBs were obtained through enzyme digestion of segregated neonatal SD rat skull. The collagen hydrogel three-dimensional culture model was established by mixing ROBs with different concentrations of type I rat tail collagen (collagen concentration of 1, 2, 3 mg/mL), DMEM medium and NaOH under adjusted PH and a temperature of 37 degrees C. Cell viability and activity were detected by FDA/PI staining and CCK-8 3 d after cell culture. The optimal culture method of 3D collagen hydrogel was identified. Cell distribution was observed using scanning electron microscopy and HE staining., Results: ROBs collagen was formed firmly at 2 mg/mL, which had significantly higher levels of cell viability and activity than those at 1 mg/mL and 3 mg/mL. Scanning electron microscopy and HE staining showed that cells under the 2 mg/mL collagen culture system adhered with collagen tightly and distributed homogeneously., Conclusion: A collagen hydrogel 3D culture model was established successfully by mixing ROBs with collagen at 2 mg/mL.

Objective: To establish osteoblast model, primary cilla model was removed by chloral hyrate, observe effects of osteoblast primary cilla moved on enhancing ALP staining and calcified nodules staining in electromagnetic field., Methods: Three 3-day-old male SD rats weighed between 6 and 9 g were killed, cranial osteoblast was drawed and adherencing cultured respectively. Cells were subcultured and randomly divided into 4 groups until reach to fusion states. The four groups included chloral hydrate non-involved group (control group), 2 mM, 4 mM and 8 mM chloral hydrate group, and cultured in 37 °C, 5% CO2 incubator for 72 h. Morphology of primary cilla was observed by laser confocal scanning microscope, and incidence of osteoblast primary cilia was analyzed by Image-Pro Plus 6.0 software. Cells in the correct concentration group which can removed cillia most effectively were selected and divided into 3 groups, including control group (C), Electromagnetic fields group (EMFs), and EMFs with 4 mM chloral hydrate group. DMEM nutrient solution contained 10%FBS were added into three groups and cultured for 9 days and formation of ALP were observed by histochemical staining of alkaline phosphatase. After 12 days' cultivation, formation of mineralization nodes was observed by alizarin red staining., Results: Compared with control group and 2mM chloral hydrate group,4 mM chloral hydrate group could effectively remove osteoblast primary cilla (P<0.01). Removal of osteoblast primary cilla could weaken the formation of ALP and mineralization nodes in osteoblast in EMFS. Compared with EMFs group, the area of ALP and mineralization nodes in EMFs with 4 mM chloral hydrate group were decreased obviously (P<0.01)., Conclusion: 4mM chloral hydrate could effectively remove osteoblast primary cilia. Primary cilla participate in EMFs promoting formation of ALP and mineralization nodes in osteoblast and provide new ideas for exploring mechanism of EMFs promoting osteoblast maturation and mineralization.

Objective: To investigate the effects of icariin on the differentiation and maturation of rat calvarial osteoblasts(ROB) in collagen hydrogel three-dimensional culture., Methods: ROB were obtained by enzyme digestion from the segregated neonatal SD rats skull and were embedded in 2 mg/mL rat tail collagen for three-dimensional culture. The growth state of ROB was observed by FDA/PI staining, HE staining and scanning electron microscopy. ROB were treated with icariin at the concentration of 1 × 10⁻⁴, 1 × 10⁻⁵, 1 × 10⁻⁶ and 1 × 10⁻⁷ mol/L respectively. The activity of alkaline phosphatase(ALP) was detected after 3, 6, 9 d of icariin treatment. Three-dimensional cultured ROB were treated with optimal concentration icariin for 12, 24, 36, 48 h and total RNA was extracted and the mRNA expressions of bone morphogenetic protein-2 (BMP-2), Runt-related transcription factor 2 (RUNX-2) and Osterix were detected by real time RT-PCR. The protein expression of BMP-2, RUNX-2 and Osterix were examined by Western-blotting., Results: ROB were cultured in collagen hydrogel successfully. FDA/PI staining, HE staining, and scanning electron microscopy showed that ROB adhered with collagen tightly and distributed homogeneously. Icariin at final concentration of 1 × 10⁻⁵, 1 × 10⁻⁶ and 1×10⁻⁷ mol/L all enhanced the activity of ALP of collagen hydrogel three-dimensional cultured ROB, and 1 × 10⁻⁶ mol/L was the optimal concentration. Besides, icariin (1 × 10⁻⁶ mol/L) increased mRNA and protein expression of BMP-2、RUNX-2 and Osterix compared to control group., Conclusion: Icariin can enhance the expression of osteogenic markers of ROB in collagen hydrogel three-dimensional culture significantly.

Although pulsed electromagnetic fields (PEMFs) have been approved as a therapy for osteoporosis, action mechanisms and optimal parameters are elusive. To determine the optimal intensity, exposure effects of 50 Hz PEMFs of 0.6-3.6 mT (0.6 interval at 90 min/day) were investigated on proliferation and osteogenic differentiation of cultured calvarial osteoblasts. All intensity groups stimulated proliferation significantly with the highest effect at 0.6 mT. The 0.6 mT group also obtained the optimal osteogenic effect as demonstrated by the highest ALP activity, ALP(+) CFU-f colony formation, nodule mineralization, and expression of COL-1 and BMP-2. To verify our hypothesis that the primary cilia are the cellular sensors for PEMFs, osteoblasts were also transfected with IFT88 siRNA or scrambled control, and osteogenesis-promoting effects of 0.6 mT PEMFs were found abrogated when primary cilia were inhibited by IFT88 siRNA. Thus primary cilia of osteoblasts play an indispensable role in mediating PEMF osteogenic effect in vitro., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

Objective: To investigate the estrogenic activity of icariin and genistein with estrogen-dependent human breast cancer (MCF-7) cells., Method: MCF-7 cells were incubated with media containing 5% charcoal dextran-treated FBS in phenol red-free media for 48 h. CCK-8 kit was used to study the impact of defferent concentration of icariin and genistein on MCF-7 proliferation in vitro. Optimal concentration icariin and genistein were added into medium and total RNA was isolated after 12, 24, 36, 48 h. The gene expression of ERalpha, ERbeta, PS2, and PR were investigated by Real-time RT-PCR Total protein was also isolated and secretion of ERalpha, ERbeta, PS2, and PR were examined by Western blot., Result: 10 micromol x L(-1) icariin and genistein could promote the proliferation of MCF-7 evidently. However, the ability of genistein to promote the proliferation was better than icariin. With the concentration of 10 micromol x L(-1), genistein group had a stronger expression of ERa, PS2 and PR mRNA levels than icariin while ERbetaexpression had no significant difference in two group. The same effects were detected by western blotting., Conclusion: Both genistein and icariin have a strong estrogen-like effect, but the estrogenic activity of genistein is stronger than icariin. It showed that the activity of icariin is stron-ger than genistein to promote ROB maturation. So it must be that icariin promotes the maturation of osteoblasts in vitro by a estogen-independent mechanism.

An effective method for preventing bone loss is by promoting osteoblast differentiation and bone formation. While dexamethasone has been routinely used as a classical inducer for osteoblast differentiation, limitations have been observed with its usage, including its varied effects on expression of osteoblast genes in different species and its potentials in suppressing osteoblastic differentiation and mineralization. In this study, we assessed the ability of flavonoid icariin in enhancing differentiation and mineralization of cultured rat primary osteoblasts in the absence of dexamethasone. It was found that, compared to the non-stimulated control, icariin at 10(-5) M produced a higher alkaline phosphatase activity, more and larger areas of alkaline phosphatase-positive colonies (CFU-FALP) and mineralized nodules, more osteocalcin secretion and calcium deposition, higher levels of mRNA expression of alkaline phosphatase, osteoblastic transcription factors osterix and runt-related transcription factor 2, and collagen 1α, higher levels of protein expression of collagen 1α, alkaline phosphatese, osterix, and runt-related transcription factor 2. In addition, icariin at 10(-5) M was always more potent than dexamethasone at its optimal concentration of 10(-8) M on the above osteoblast differentiation and mineralization markers. Taken together, our studies demonstrated that icariin has a pronounced ability in promoting osteoblast differentiation in vitro in the absence of dexamethasone., (Georg Thieme Verlag KG Stuttgart · New York.)

Objective: To investigate the molecular mechanisms of icariin (ICA) in regulating the bone formation of osteoblasts and the bone resorption of osteoclasts., Methods: Primary osteoblast cell cultures were obtained from newborn rat calvarial. Calcified nodules were stained by alizarin red. The mRNA levels of osterix (OSX), runt-related transcription factor 2 (Runx-2), alkaline phosphatase (ALP), Collagen1, osteoprotegerin (OPG), and receptor activator of nuclear factor-ΚB ligand (RANKL) were analyzed by quantitative real-time RT-PCR, the protein levels of OPG, RANKL, and Collagen1 were examined by Western blotting, and the intracellular Ca(2+) concentration of osteoblasts was measured on a flow cytometer using the Cellquest program., Results: Compared with control group, ICA markedly promoted bone formation by significant up-regulating the gene expressions of OSX, Runx-2,ALP, and Collagen1, the protein expression of Collagen1(all P<0.01), and the Ca(2+) concentration. Furthermore, ICA remarkably inhibited bone resorption by significant up-regulating the mRNA and protein expressions of OPG as well as the OPG/RANKL ratio., Conclusions: ICA could promote bone formation of osteoblasts through inducting the gene expressions of OSX,Runx-2, ALP and Collagen1, and the protein expressions of Collagen1, and by increasing the Ca (2+) concentration. Moreover, ICA could inhibit bone resorption of osteoclasts through regulating OPG/RANKL signal pathway.