In vivo effects of low-frequency low energy pulsing electromagnetic fields (PEMFs) on gene expression during the inflammation phase of bone repair

It has been widely demonstrated that pulsed low-frequency electromagnetic fields (PEMFs) positively affect bone repair. The aim of this study is to highlight if PEMFs influence cell metabolic activity during the replacement of the blood clot with granulation tissue in the inflammation phase of bone repair. Four equal transcortical holes were made, at the same diaphyseal level, in both metacarpals (McIII) of five male adult horses. The left McIII were exposed to PEMFs 24 hr/day; the right untreated McIII were used as controls. Eight days after surgery, the horses were sacrificed. We investigated the effect of PEMFs on 1) histological aspects of the lesion, 2) histochemical detection of the bone marker alkaline phosphatase, and 3) molecular markers as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and transforming growth factor-β1 (TGF-β) by reverse transcriptase-polymerase chain reaction amplification (RT-PCR). The histological analysis indicates that the blood clot, in both PEMF treated and control holes, is being replaced by granulation tissue extending from the endosteal towards the periosteal side of the lesion. TALP positive areas do not exactly correspond to the areas where fibroblasts are present, these being wider than the former. The study of the expression of the mRNA of TGF-β1 shows no differences between treated holes and control ones. The expression of TNF-α and IL-6 however, is not univocal, being sometimes more expressed, sometimes less in treated or control holes. These data show that PEMFs exposure affects the expression of inflammatory cytokines (TNF-α and IL-6) during the very early stages of bone repair. On the contrary TFG β expression and histological findings are not modified by PEMF exposure at least in this experimental condition.