RESUMEN
As the primary myelin-forming cells of the peripheral nervous system, Schwann cells (SCs) play a key role in the regeneration of injured peripheral nerves. However, hypoxia causes injury of SCs, as observed in peripheral neuropathies, including those caused by diabetes. So we investigated the effect of hypoxia/reoxygenation (H/R) on SCs in this study. To do so, SCs were cultured in hypoxic condition in vitro and then in normal condition for 24 hr; The effects H/R on SCs were evaluated by MTT (3(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide) assay, Hoechst staining, immunocytochemistry, western blotting, ELISA, and RT-PCR. H/R resulted in a significant decrease in SCs survival and an increase in caspase-3 activity. H/R also reduced the mRNA level of BDNF (brain derived neurotrophic factor) and its secretion, but NGF mRNA level was elevated in these cells. These observations showed that H/R induces death of primary cultured SCs, and different mechanisms responsible for regulating NGF and BDNF expression.
Asunto(s)
Hipoxia/fisiopatología , Factores de Crecimiento Nervioso/metabolismo , Regeneración Nerviosa/fisiología , Oxígeno/metabolismo , Enfermedades del Sistema Nervioso Periférico/fisiopatología , Células de Schwann/metabolismo , Animales , Apoptosis/fisiología , Factor Neurotrófico Derivado del Encéfalo/genética , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Caspasa 3/metabolismo , Supervivencia Celular/fisiología , Células Cultivadas , Neuropatías Diabéticas/metabolismo , Neuropatías Diabéticas/patología , Neuropatías Diabéticas/fisiopatología , Regulación hacia Abajo/fisiología , Hipoxia/metabolismo , Hipoxia/patología , Isquemia/metabolismo , Isquemia/patología , Isquemia/fisiopatología , Vaina de Mielina/fisiología , Vaina de Mielina/ultraestructura , Factor de Crecimiento Nervioso/genética , Factor de Crecimiento Nervioso/metabolismo , Factores de Crecimiento Nervioso/genética , Enfermedades del Sistema Nervioso Periférico/metabolismo , Enfermedades del Sistema Nervioso Periférico/patología , ARN Mensajero/metabolismo , Ratas , Ratas Sprague-Dawley , Regulación hacia Arriba/fisiología , Degeneración Walleriana/metabolismo , Degeneración Walleriana/patología , Degeneración Walleriana/fisiopatologíaRESUMEN
Previous studies have demonstrated that end-organ deprivation after peripheral nerve injury results in targeting of regenerating nerve fibers into inappropriate pathways, which leads to poor functional recovery. Here we studied the effect of electrical stimulation on the regeneration selectivity of motor nerves after peripheral nerve injury and end-organ deprivation. We found that end-organ deprivation reduced regenerating selectivity of motor nerves, total number of regenerating motoneurons, and level of neural trophic factors in the regenerating pathways after nerve injury (p < 0.05). Electrical stimulation successfully promoted motor nerve regeneration selectivity regardless of end-organ connections (p < 0.05). This increased selectivity was accompanied by an increase in the protein level of neural trophic factors in the distal nerve stumps by 3 weeks after nerve injury (p < 0.05). There was a similar increase in the protein level of these neural trophic factors in denervated muscle. However, the RNA level of these factors decreased both in the distal nerves and in the muscle. Despite the promising effect of promoting motor nerve regeneration selectivity, electrical stimulation did not prevent motoneuron loss caused by end-organ deprivation. The present study suggests that end organs contribute to the development of selective motor nerve regeneration by increasing the neurotrophic factors in the regeneration pathways. Electrical stimulation is an efficient strategy to ameliorate the deteriorated regeneration microenvironment caused by end-organ deprivation and to promote motor nerve regeneration selectivity when end-organ connections are deprived.