Electric fields and proliferation in a chronic wound model.

A wound model for decubitus and leg ulcers consisting of human dermal fibroblasts in type I collagen dermal "equivalent" matrix (DEM) was exposed in vitro to electric fields similar to postulated endogenous fields in wounds. After an 8-10 day maturation period, conductivity of DEM samples was determined. Then, DEM samples were mounted in oval windows equidistant between Ag/AgCl agar electrodes in exposure chambers containing serum-free medium. A known low-frequency sinusoidal current was then applied for 12 h, and the average electric field amplitude was calculated in the region of the cells. After a 6 h hiatus, 3H-thymidine was introduced for 6 h. This was followed by assay. Over a series of trials, field amplitude ranged from 18 to 1,000 mV/m at frequencies of 10 and 100 Hz. Proliferation was measured by total DNA and 3H-thymidine incorporation. Results indicated that a narrow amplitude window between 37 and 50 mV/meter at 10 Hz yielded increases in proliferation: At maximum (41 mV/m), there was a 70% increase in total DNA (P < .01). Increases occurred in 3H-thymidine incorporation at 41-50 mV/m but not at other amplitudes (P < .05). Increases in total DNA at 41 mV/m occurred at 10 Hz but not 100 Hz (P < .01). 3H-thymidine incorporation was in agreement (P < .05). Response was also a function of cell density within matrix. Proliferation occurred in the same amplitude and frequency ranges in which endogenous fields are expected to occur.