Progress of researches on acupuncture treatment of spinal cord injury by promoting axonal regeneration

Based on the growth factor theory, external inhibition theory, and neuronal intrinsic theory, we, in this paper, summed up the potential mechanisms of acupuncture in the treatment of spinal cord injury (SCI) by promoting the axonal regeneration in recent years. Acupuncture can promote the repairment of SCI by (1) regulating the expressions of spinal cord growth factors (such as nerve growth factor, brain derived neurotrophic factor, neurotrophin-3, glial cell line-derived neurotrophic factor, ciliary neurotrophic factor, insulin-like growth factor, etc.) to support neuronal survival and axon growth; (2) inhibiting the expression of spinal cord myelin growth inhibitor Nogo protein and oligodendrocyte myelin glycoprotein (OMgp), requlating axon guide molecules Sema3A and Wnt family, etc., and inhibiting the formation of astryocyte scar to create a favorable local microenvironment for axon regeneration; and (3) regulating spinal phosphatase and tensin homolog deleted on chromosome ten (PTEN)/mammalian target of rapamycin (mTOR) signaling, down-regulating Ras homolog gene family member A (RhoA)/ Rho-associated protein kinase Ⅱ (ROCK Ⅱ) signaling, up-regulating mitogen-activated protein kinase kinase (MAPK)/ extracellular signalregulated kinase (ERK) signaling, cAMP/ protein kinase A (PKA) signaling, etc.. In addition, we also found that by modulating axon regeneration, acupuncture therapy can not only effectively restore motor function in SCI patients, but also improve neurogenic bladder symptoms.