Screening The Optimum Stimulation Parameters Of Pulsed Electromagnetic Fields On Osteoblasts From Rat Calvarias

It has been proved that pulsed electromagnetic fields (PEMF) could bebeneficial on the bone nonunion and bone fracture in clinics for30years ago.However, the exact mechanism for PEMF affecting the bone mass is still not yetunderstood. Comparing with other physical or chemical treatment methods,PEMF has many unique advantages, such as improved, safety, low cost andnon-invasiveness. Although numerous studies have proved that PEMF couldsignificantly increased the bone mass and promote stimulate the bone fractureshealing, the parameters used in each group might not be totally the same, whichhave further influenced the systematical knowledge to the mechanism of PEMFon the bone formation. Based on these issues, we aimed to study PEMF withdifferent stimulation parameters (PEMF magnitude, frequency and duty cycles)on the calvarias extracted from the suckling rats. Based on the results in thisstudy, we expect to screen the optimum PEMF stimulation parameters in vitroand provide further potential clinical evidence for the clinical application ofPEMF on bone diseases. This study includes the following steps:1. Design of the PEMF stimulation device. The PEMF stimulation deviceconsists of the signal generator and coils. The signal generator could provide0~100Hz and0~10A electric current signal (includes pulsed bursts, single pulse,triangle waveform and sine waveform). Based on the theoretical calculation andexperimental measurements, the PEMF distribution inside the coils is uniform.2. The extraction, purification and identification of primary osteoblasts from ratcalvarias. The primary osteoblasts were confirmed by the positive effects ofalkaline phosphatase(ALP) staining and alizarin red staining.3. The effects of PEMF with different magnitudes on the osteoblastic activities.PEMF with15Hz and50%duty circle with different strengths (0.3,0.5,0.7,1.0,2.0,2.5,3.0and4.0mT) were used to stimulate the primary osteoblasts. Theresults indicated that PEMF with0.5,0.7,1.0and2.0mT significantly increasethe osteoblastic proliferation, but not in the0.3、2.5、3.0mT group.4.0mTgroup inhibited the cell proliferation. PEMF with0.5,0.7,1.0and2.0mTdramatically increased the cell differentiation, but not in the2.5and3.0mTgroups.0.3and4.0mT group was found to inhibit the cell differentiation.4. The effects of PEMF with different frequency on the osteoblastic activities.PEMF with1mT and50%duty circle with different frequency (15,30,50,75and100Hz) was used to stimulate the primary osteoblasts. The results indicated thatPEMF with15,30and50Hz significantly increase the osteoblastic proliferation,but not in the75Hz group.100Hz group inhibited the cell proliferation. PEMFwith15and30Hz dramatically increased the cell differentiation, but not in the50Hz groups.100Hz group was found to inhibit the cell differentiation.5. The effects of PEMF with different duty circles on the osteoblastic activities.PEMF with1mT and15Hz with different duty circles (10,20,40,60and80%) were used to stimulate the primary osteoblasts. The results indicated tha t PEMFwith20,40and60%significantly increase the osteoblastic proliferation, but notin the10and80%group. PEMF with10,20,40and60%dramatically increasedthe cell differentiation, but not in the80%groups.6. The effects of EMF with different waveforms on the osteoblastic activities.EMF with different waveforms (PEMF,REMF,SEMF,TEMF and SMF) wereused to stimulate the primary osteoblasts. The results indicated thatPEMF,REMF,significantly increase the osteoblastic proliferation, but not in theSEMF and SMF group. TEMF group inhibited the cell proliferation.PEMF,REMF and SMF dramatically increased the cell differentiations. TEMFgroup was found to inhibit the cell differentiation.