In vitro bone-cell response to a capacitively coupled electrical field. The role of field strength, pulse pattern, and duty cycle.
Newborn rat calvarial bone cells were grown to confluence and subjected to a matrix of sine wave 60-kHz capacitively coupled electrical signals of various field strengths, pulse-burst patterns, and duty cycles. Both [3H] thymidine incorporation into DNA and alkaline phosphatase activity were evaluated in field strengths ranging from 0.0001 to 20 mV/cm, with pulse-burst patterns ranging from continuous to 5 milliseconds ON/495 milliseconds OFF, with daily duty cycles ranging from 0.25% to 25%. A significant increase in proliferation occurred in field strengths of 0.1, 1, and 20 mV/cm when the signal was applied continuously for six hours. Significant proliferation also occurred when the 20-mV/cm field was pulsed for six hours at 5 milliseconds ON/495 milliseconds OFF and at 5 milliseconds ON/245 milliseconds OFF. No change in alkaline phosphatase activity occurred in the 20-mV/cm field with any signal. At 1 mV/cm, there was a significant decrease in alkaline phosphatase activity in the continuous signal and in the 5 milliseconds ON/62 milliseconds OFF signal; in the lower fields evaluated, there was an actual decrease in alkaline phosphatase activity with some of the signals. The field strength plays a dominant role in determining the bone-cell's proliferative response, and to a lesser extent the alkaline phosphatase activity response, to a capacitively coupled electric field. The pulse configuration and the duty cycle are also important, but only if the proper field strength is being applied to the cell.
Brighton
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McKay Laboratory of Orthopaedic Surgery Research, Department of Orthopaedic Surgery, University of Pennsylvania School of Medicine, Philadelphia 19104-6081.
Okereke
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Pollack
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Clark
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D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001842:Bone and Bones / Q000166:cytology / Q000378:metabolism; D002478:Cells, Cultured; D004247:DNA / Q000032:analysis; D004558:Electric Stimulation; D066298:In Vitro Techniques; D010012:Osteogenesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D013936:Thymidine / Q000378:metabolism
D004247:DNA; D000469:Alkaline Phosphatase; D013936:Thymidine