Pulsed electromagnetic fields increase growth factor release by nonunion cells

The mechanisms involved in pulsed electromagnetic field stimulation of nonu nions are not known. Animal and cell culture models suggest endochondral os sification is stimulated by increasing cartilage mass and production of tra nsforming growth factor-beta 1, For the current study, the effect of pulsed electromagnetic field stimulation on cells from human hypertrophic (n = 3) and atrophic (n = 1) nonunion tissues was examined. Cultures were placed b etween Helmholtz coils, and an electromagnetic field (4.5-ms bursts of 20 p ulses repeating at 15 Hz) was applied to 1/2 of them 8 hours per day for 1, 2, or 4 days. There was a time-dependent increase in transforming growth f actor-beta 1 in the conditioned media of treated hypertrophic nonunion cell s by Day 2 and of atrophic nonunion cells by Day 4, There was no effect on cell number, [H-3]-thymidine incorporation, alkaline phosphatase activity, collagen synthesis, or prostaglandin E-2 and osteocalcin production, This i ndicates that human nonunion cells respond to pulsed electromagnetic fields in culture and that transforming growth factor-beta 1 production is an ear ly event, The delayed response of hypertrophic and atrophic nonunion cells (> 24 hours) suggests that a cascade of regulatory events is stimulated, cu lminating in growth factor synthesis and release.