Exposure Duration Is a Determinant of the Effect of Sinusoidal Electromagnetic Fields on Peak Bone Mass of Young Rats.

We proposed a three-step strategy to obtain the optimal therapeutic parameters, which is composed of large-scale screening at cellular level, verification in animal experiments, and confirmation by a clinical trial. The objective of the current study was to test the feasibility of our strategy. Newborn rat calvarial osteoblasts were treated by 50 Hz 1.8 mT sinusoidal electromagnetic fields (SEMFs) with 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 h/days, respectively. The osteogenic differentiation and maturation of the osteoblast were assayed and compared to obtain the optimal duration. One-month-old growing rats were then treated by the same SEMFs with 0.5, 1.5, and 2.5 h/days, respectively, and the peak bone mass was analyzed after 2 months. It was found that the optimal exposure duration to promote the osteogenic differentiation and maturation of osteoblasts was 1.5 h/days, judging by the increasing degrees of ALP activity, calcified nodules formed, the gene and protein expression levels of Runx-2, BMP-2, and Col-I, as well as the expression levels of signaling proteins of the BMP-2/Smad1/5/8 pathway. The highest increase of peak bone mass after 2 months was also obtained by 1.5 h/days, judging by the results of X-ray dual-energy absorptiometry, mechanical property analysis, micro-CT scanning, and serum bone turnover marker examinations. The above results indicated that exposure duration is a determinant for the therapeutic effect of EMFs, and the optimal therapeutic effects only can be obtained by the optimal exposure duration.

Icariin attenuates hypoxia-induced oxidative stress and apoptosis in osteoblasts and preserves their osteogenic differentiation potential in vitro.

OBJECTIVES: Icariin, a prenylated flavonol glycoside isolated from traditional Chinese medicinal herb of the genus Epimedium, has been demonstrated to be a potential alternative therapy for osteoporosis, and its action mechanism so far has been mainly attributed to its phytoestrogenic property. As blood supply to bone is considerably reduced with ageing and by the menopause, we hypothesized that icariin treatment would reduce bone loss by preventing ischaemia-induced hypoxic damages to bone. MATERIALS AND METHODS: To investigate effects of icariin treatment on cultured rat calvarial osteoblasts exposed to hypoxic conditions (2% oxygen). RESULTS: Compared to normoxic control, cell viability decreased with time to 50% by 48 h in the hypoxic group, and icariin attenuated the reduction, dose dependently, with 10(-6) and 10(-5)  m concentrations showing significant protective effects. Icariin also inhibited increase of lactate dehydrogenase activity in culture media. Measurements on oxidative stress, cell cycling and cell survival indicated that icariin protected osteoblasts by reducing production of reactive oxygen species and malondialdehyde, increasing superoxide dismutase activity, arresting the cell cycle and inhibiting apoptosis. Icariin also preserved osteogenic differentiation potential of the hypoxic cells in a dose-dependent manner, compared to the hypoxia alone group, as revealed by increased levels of RUNX-2, OSX and BMP-2 gene expression, alkaline phosphatase activity, and formation of mineralized nodules. CONCLUSIONS: Our results demonstrated that icariin attenuated oxidative stress and apoptosis and preserved viability and osteogenic potential of osteoblasts exposed to hypoxia in vitro, and suggested that its anti-osteoporotic effect may be attributed to its anti-hypoxic activity and phytoestrogenic properties.

Pathobiology and prevention of cancer chemotherapy-induced bone growth arrest, bone loss, and osteonecrosis.

Cancer chemotherapy has been recognized as one severe risk factor that influences bone growth and bone mass accumulation during childhood and adolescence. This article reviews on the importance of this clinical issue, current understanding of the underlying mechanisms for the skeletal defects and potential preventative strategies. Both clinical and basic studies that appeared from 1990 to 2010 were reviewed for bone defects (growth arrest, bone loss, osteonecrosis, and/or fractures) caused by paediatric cancer chemotherapy. As chemotherapy has become more intensive and achieved greater success in treating paediatric malignancies, skeletal complications such as bone growth arrest, low bone mass, osteonecrosis, and fractures during and/or after chemotherapy have become a problem for some cancer patients and survivors particularly those that have received high dose glucocorticoids and methotrexate. While chemotherapy-induced skeletal defects are likely multi-factorial, recent studies suggest that different chemotherapeutic agents can directly impair the activity of the growth plate and metaphysis (the two major components of the bone growth unit) through different mechanisms, and can alter bone modeling/remodeling processes via their actions on bone formation cells (osteoblasts), bone resorption cells (osteoclasts) and bone "maintenance" cells (osteocytes). Intensive use of multi-agent chemotherapy can cause growth arrest, low bone mass, fractures, and/or osteonecrosis in some paediatric patients. While there are currently no specific strategies for protecting bone growth during childhood cancer chemotherapy, regular BMD monitoring and exercise are have been recommended, and possible adjuvant treatments could include calcium/vitamin D, antioxidants, bisphosphonates, resveratrol, and/or folinic acid.

Effects of acute 5-fluorouracil chemotherapy and insulin-like growth factor-I pretreatment on growth plate cartilage and metaphyseal bone in rats.

With the intensified use of chemotherapy and improved survival rates for childhood malignancies, it has become increasingly apparent that some children or adult survivors show poor bone growth and develop osteoporosis. As a step to investigate underlying mechanisms, this project examined short-term effects in rats of chemotherapy agent 5-fluorouracil (5-FU) on cell proliferation, apoptosis, and bone formation at tibial growth plate cartilage and its adjacent bone-forming region metaphysis. In addition, since insulin-like growth factor (IGF-I) is important for bone growth, we examined whether IGF-I pretreatment would potentially protect growth plate cartilage and bone cells from chemotherapy damage. Two days after a single high dose of 5-FU injection, proliferation of growth plate chondrocytes and metaphyseal osteoblasts/preosteoblasts was dramatically suppressed, and apoptosis was induced among osteoblasts and preosteoblasts. As a result, there was a reduction in the chondrocyte number and zonal height at the proliferative zone and a decline in the number of osteoblasts and preosteoblasts on the metaphyseal trabecular bone surface. At day 2, no obvious deleterious effects were observed on the height of the growth plate hypertrophic zone and the bone volume fraction of the metaphyseal primary spongiosa trabeculae. At day 10, while cell proliferation and growth plate structure returned to normal, there were slight decreases in trabecular bone volume, body length increase, and tibial length. While pretreatment with 1-week IGF-I systemic infusion did not attenuate the suppressive effect of 5-FU on proliferation in both growth plate and metaphysis, it significantly diminished apoptotic induction in metaphysis. These results indicate that growth plate cartilage chondrocytes and metaphyseal bone cells are sensitive to chemotherapy drug 5-FU and that IGF-I pretreatment has some anti-apoptotic protective effects on metaphyseal bone osteoblasts and preosteoblasts.