Pulsed electromagnetic fields promote collagen production in bone marrow fibroblasts via athermal mechanisms
Primary and passaged cultures of fibroblasts (RBMFs) raised from the bone marrow stroma of young rabbits were treated with pulsed electromagnetic fields (PEMFs) from the start of each culture until 1 week after they became confluent. The PEMF treatment had no effect on cell proliferation, estimated by phase contrast microscopy, by3H-thymidine incorporation into DNA, or by total DNA assay. Collagen production, estimated by conversion of3H-proline to3H-hydroxy-proline in nondialyzable material was markedly elevated in postconfluent cultures, but not in cultures that had only just reached confluence. About 65% of3H-hydroxyproline was in low molecular weight form, and a correlation between collagen break-down and cyclic AMP (cAMP) levels in RBMFs was demonstrated by adding dibutyryl cAMP or prostaglandin E2 (PGE2) to the culture medium concurrently with3H-proline. The PEMF apparatus caused an insufficient temperature rise (less than 0.1°C) to account for these results. We propose that the rise in collagen production is consistent with the hypothesis that PEMFs act by reducing cAMP levels in RBMFs, and that thermal effects are insignificant.