The effects of electromagnetic field on distraction osteogenesis and new bony tissue were investigated. Twenty-five New Zealand rabbits were divided into an experimental (12 rabbits) and a control (13 rabbits) group. An osteotomy was performed on the right tibia in the diaphyseal region in both groups. The experimental group was exposed to a magnetic field of 50 Hz 1.0 mT for 3 hours a day for 13 weeks. The control group was kept in a similar environment but with no electromagnetic field. The distraction was continued until an increase of 10 mm was achieved. At weeks 4, 8, and 13, radiography, scintigraphy, and a biopsy were performed in both groups, and the results were statistically analyzed. The X-ray results were similar in both groups at all times. On the other hand while the scintigraphic and histopathological results were similar at weeks 4 and 13 in both groups, the osteoblastic activity was significantly greater in the experimental group at week 8 (p < 0.01). In conclusion an electromagnetic field increases the osteoblastic activity and osteogenesis, but has little effect during the remodeling phase.
Animals ; *Electromagnetic Fields ; Osteoblasts/physiology/radiation effects ; Osteogenesis/radiation effects ; *Osteogenesis, Distraction ; Osteotomy ; Rabbits

OBJECTIVETo seek for the appropriate concentration, at which IGF-II can exerts its strong effects on postirradiation proliferation, physiological function and differentiation of the rat's osteoblast-like cells (ROB).

METHODSThe osteoblast-like cells used were isolated from the calvariae of neonatal (one-day-old) SD rats by sequential enzymatic digestion. The third passages of the cells were irradiated with gamma-ray from a (60)Co source at the doses of 100, 400, 600, and 900 cGy. The medium was changed immediately after irradiation and 5 concentrations of IGF-II, i.e., 0, 0.1, 1.0, 10.0, and 100.0 microgram/L were added. 6 days after radiation (9 days in culture), the examination, or the measurement of relative cell number, was carried out.

RESULTSRadiation inhibited the ROB, even lethally. IGF-II completely counteracted the inhibitory effects when the cells were exposed to the radiation at lower dose (100 cGy), and partially when at higher dose (400 cGy). But after the radiation at much higher dose as 900 cGy, the damages were irreversible, even with the existence of this growth factor.

CONCLUSIONSAt least a portion of effective recovery of postirradiation damages may be due to IGF-II-induced radioresistance. Incubation with IGF-II can increase radioresistance or repair of radiation-induced cells damages. However, this effect depends on the dose of radiation.

Animals ; Cell Division ; drug effects ; radiation effects ; Cells, Cultured ; Dose-Response Relationship, Drug ; Dose-Response Relationship, Radiation ; Insulin-Like Growth Factor II ; pharmacology ; Osteoblasts ; drug effects ; physiology ; radiation effects ; Radiation Tolerance ; drug effects ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo investigate the effect of exposure to static magnetic fields (SMFs) of 3.9 mT on proliferation and differentiation of osteoblasts in vitro.

METHODSThe newborn rat calvarial osteoblasts were isolated by enzyme digestion and randomly divided into 9 groups after one passage. The intensity of the SMFs was 3.9 mT. The cells were exposed in the SMFs for 0 (control group), 0.5, 1.0, 1.5, 2.0, 2.5, 3, 3.5 and 4.0 h groups respectively. They were observed under the contrast phase microscope each day. After 48 h, cell proliferation was assayed by MTT method. The alkaline phosphatase (Alkaline Phosphatase, ALP) activities and calcium content were measured after 3, 6, 9, and 12 days exposed with SMFs. The ALP positive colonies were histochemically stained after 8 days and the calcified nodules were stained by Alizarin Bordeaux after 10 days; BMP-2, Runx-2 and Opg mRNA expression were measured after SMFs treatment in 0, 24, 48 and 72 h.

RESULTSContrast with control group, all SMFs groups enhanced cell proliferation (P < 0.01 or P < 0.05), and they promoted maturation and mineralization of the osteoblasts. The results showed that SMFs improved the ALP activity, promoted calcium content, boost BMP-2, Runx -2 and Opg mRNA expression.

CONCLUSIONThe cells exposed to the SMFs of 3.9 mT at 2.5 h apparently promote proliferation and differentiation of osteoblasts in vitro.

Animals ; Bone Morphogenetic Protein 2 ; genetics ; Calcium ; metabolism ; Cell Differentiation ; radiation effects ; Cell Proliferation ; radiation effects ; Core Binding Factor Alpha 1 Subunit ; genetics ; Magnetic Fields ; Osteoblasts ; physiology ; radiation effects ; Osteoprotegerin ; genetics ; Rats ; Rats, Sprague-Dawley ; Time Factors