The investigation of macrophage-mediated effect of pulsed magnetic field on rat sciatic nerve regeneration by local clodronate administration

Peripheral nerve injuries can result from mechanical trauma, thermal, chemical, congenital, or pathological etiologies. Failure to restore these damaged nerves can lead to the loss of muscle function, impared sensation, and painful neuropathies. Following nerve injury in the Peripheral Nervous System (PNS), resident and systemic monocytes rapidly invade the site of injury and, after a delay, the distal portion of injured nerve undergoing Wallerian Degeneration (WD). The role of macrophages during WD has been studied using different experimental approaches. During the axonal regenerating macrophages are known to produce and secrete over 100 different factors which include cytokines, growth factors, and proteolytic enzymes. These factors may act in manner to modulate tissue growth, wound repair, and phagocytosis.In our study, to create traumatic mononeuropathy model, right sciatic nerve of the wistar rats were crushed and the effects of Pulsed Magnetic Field (PMF) were determined on nerve recovery. Moreover, the aim of this study was to identify macrophage-mediated effects of PMF treatment on the mechanism underlying traumatic mononeuropathy model in rats and compared with experimental other groups.In our experiments all data were obtained in both the tibial (largely motor) and sural (sensor) distal sciatic branches of rats. In this study we used liposome encapsulated clodronate (LEC) to selectively deplete or reduce resident and systemic macrophages population during the degeneration-regeneration cycle. In traumatic mononeuropathy experiments, to obtain data about the effects of PMF, Crush, LEC and the combination of PMF and LEC groups in vitro electrophysiological methods (sucrose-gap), functional test, electron and light microscobic histomorphometric experiment were carried out. 4-Aminophyridine (4-Ap) and Tetraethylammonium (TEA) were used to determine fast and slow K+ channel development and localization after remyelination. After crush injury of the sciatic nerves, rats divided into five groups and exposed to PMF (1 h/day, intensity; 1,5 mT, consecutive frequency; 1-10-20-40 Hz).Our data show that the PMF may be a critical functional recovery effect on remyelination after peripheral nerve injury. Macrophages have been proven to be important effector cells during WD. They provide at least two basic functions: phagocytosis of degenerating myelin and production of cytokines and neurotrophic factors. PMF may stimulate macrophages to secret a factor that promotes axonal growth and myelin restoration. A unknown factor that initiates the regenerating processes a candidate for enhancing nerve recovery, and PMF seems to be one of the triggers of nerve regeneration. In addition, our results indicate that PMF application may be an effective therapeutic treatment of peripheral nerve injuries.Key words: Pulsed Electromagnetic Field, Peripheral nerve injury and regeneration, Macrophages, Liposome encapsulated clodronate, K+ channels.