[Low-frequency pulsed electromagnetic fields promotes rat osteoblast differentiation in vitro through cAMP/PKA signal pathway].

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.

Sinusoidal electromagnetic fields promote bone formation and inhibit bone resorption in rat femoral tissues in vitro.

Effects of sinusoidal electromagnetic fields (SEMFs) on bone metabolism have not yet been well defined. The present study investigated SEMF effects on bone formation and resorption in rat femur bone tissues in vitro. Cultured femur diaphyseal (cortical bone) and metaphyseal (trabecular bone) tissues were treated with 50 Hz 1.8 mT SEMFs 1.5 h per day for up to 12 days and treatment effects on bone formation and resorption markers and associated gene expression were examined. Treatment with SEMFs caused a significant increase in alkaline phosphatase (ALP) activity and inhibited the tartrate-resistant acid phosphatase (TRACP) activity in the femoral diaphyseal or metaphyseal tissues. SEMFs also significantly increased levels of mRNA expression of osterix (OSX), insulin-like growth factor (IGF-1) and ALP in the bone tissues. SEMF treatment decreased glucose content and increased lactic acid contents in the culture conditioned medium. In addition, treatment with SEMFs decreased mRNA expression levels of bone resorption-related genes TRACP, macrophage colony stimulating factor (M-CSF) and cathepsin K (CTSK) in the cultured bone tissues. In conclusion, the current study demonstrated that treatment with 1.8 mT SEMFs at 1.5 h per day promoted bone formation, increased metabolism and inhibited resorption in both metaphyseal and diaphyseal bone tissues in vitro.

Pulsed electromagnetic fields promote osteoblast mineralization and maturation needing the existence of primary cilia.

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.

Effect of sinusoidal electromagnetic field on bone mineral density and histomorphometry of rats at different time points.

OBJECTIVE: To investigate the effect of 50 Hz 0.1 mT sinusoidal electromagnetic field at different time points on bone mineral density(BMD)and histomorphometry in rats. METHODS: Totally 50 6-week-old female SD rats were equally randomized into 5 groups: control group,45-minute group,90-minute group,180-minute group,and 270-minute group. Except for the control group,the other four groups were given magnetic intervention in the 50-Hz 0.1-mT sinusoidal electromagnetic field for 45 minutes,90 minutes,180 minutes,or 270 minutes,respectively,on a daily basis. After 8 weeks,the total body BMD,femur BMD,and vertebral BMD were measured by dual-energy X-ray absorptiometry. The left tibia and the fifth lumbar vertebrae were separated for bone tissue static and dynamic analyses. RESULTS: Compared with control group,the 90-minute group and the 180-minute group had significantly different total body BMD(P<0.01,P<0.05),while no such significant difference was seen in the 45-minute group and 270-minute group (P>0.05). The femur,vertebral BMD,serum biochemical markers,and the static parameters of the fifth lumbar vertebrae tissue showed significant differences in the 90-minute group,180-minute group,and 270-minute group(P<0.01),but not in the 45-minute group (P>0.05). As shown by double fluorescent labeling,the distance was sorted in an order of 90-minute group>180-minutes group>270-minute group>45-minutes group>control group. CONCLUSION: The 50-Hz 0.1-mT sinusoidal electromagnetic field can effectively increase bone mineral density and improve bone morphology;however,the intervention effectiveness differs at different time points,with the best effectiveness seen at 90 minutes.

Experimental study on the molecular mechanism of anthraquinone cathartics in inducing melanosis coli / 中国结合医学杂志

<p><b>OBJECTIVE</b>To explore the significance of colonic epithelial cell apoptosis and tumor necrosis factor α (TNF-α) changing in pathogenesis of melanosis coli (MC) in guinea pig and the molecular mechanism of rhubarb (Rhu) in inducing the disease, by means of using different dosages of Rhu to induce the disease.</p><p><b>METHODS</b>One hundred and forty-four male guinea pigs, clean grade, were randomized according to their body weight into 5 groups, the untreated normal group and the 4 Rhu groups treated, respectively, with different doses of Rhu, 3 g/kg·d for low dose (Rhu-l) group, 6 g/kg·d for moderate dose (Rhu-m) group, 12 g/kg·d for high dose (Rhu-h) group and 24 g/kg·d for super-high dose (Rhu-s) group via gastric infusion. All animals were sacrificed 60 days later, their viscera were taken for observing the pathologic and morphologic changes with HE, melanin and melatonin staining, and the apoptosis of colonic epithelial cells was detected with TUNEL stain and transmission electric microscopy. In addition, the levels of TNF-α in serum and colonic tissue were measured using ELISA and RT-PCR.</p><p><b>RESULTS</b>The pathological changes of MC could be found by naked eye in all Rhu groups, especially apparent at caecum and proximal end of colon, but did not found in gallbladder, jejunum and ileum. In normal guinea pigs, the colonic membrane was pink in color with no apparent pigment deposition. Membranous color deepened in the Rhu groups depending on the dosage of Rhu used. MC scoring showed the highest scores revealed in the Rhu-s group (6.00±0.00), which was significantly different to those in the Rhu-l (3.86±0.69), Rhu-m (4.43±0.79) and Rhu-h groups (4.88±0.35, all P<0.05). Levels of cell apoptosis in colon and TNF-α in serum in all Rhu groups were higher than those in the normal group (P<0.01), but showed no significant difference among the Rhu groups (P>0.05). Moreover, a positive correlation was found in the degree of induced MC with apoptosis rate and TNF-α level.</p><p><b>CONCLUSIONS</b>Rhu (anthraquinone purgatives) had apparent effect on inducing MC; its molecular mechanism is maybe to destroy intestinal mucosal barrier and advance proinflammatory factor TNF-α releasing, which leads to colonic epithelial cells apoptosis, and finally induce the change of MC due to the deposition of brown pigments, i.e. the macrophage phagocytized apoptotic body, on the colonic membrane.</p>