| Background: Brachial plexus injury,especially brachial plexus root avulsion injury(BPA),can cause complete paralysis of the upper limbs,which is the most serious injury of the upper limbs.The treatment is difficult and the prognosis is poor.It often occurs in young adults and brings a huge psychological and economic shock to patients and their families.There are many pathogenic factors of injury,including penetrating injury,fall,trauma caused by motor vehicles,newborn birth injury and so on.Although it is difficult to determine the exact amount of new BPA every year worldwide,its incidence has been on the rise with the popularity of extreme sports and the increase in the number of survivors of motor vehicle accidents.In 70% of brachial plexus severe stretch injuries,avulsion of nerve roots occurs,which permanently separates the spinal cord from the surrounding effectors(muscles).This leads to the irreversible death of motor neurons in the anterior horn of the spinal cord due to the loss of nutritional innervation and the surrounding harmful substances,resulting in the loss of motor function.BPA is a kind of preganglionic nerve injury,which generally needs to be treated by nerve transfer or functional muscle transplantation and reconstruction,but it has poor curative effect and inevitably sacrifices normal nerve tissue,which expands the scope of injury and the risk of secondary operation.In recent years,the in situ replantation of avulsed nerve has attracted more and more attention by researchers,which has the advantages of simple operation and less side effects.In the previous work,we have studied this treatment method and proved the effectiveness of the method,but the simple in situ replantation cannot make the postoperative function recovery satisfactory.In the mechanism of BPA injury,the primary traumatic violence can cause nerve tissue damage,bleeding,and tissue edema,further induce oxidative stress,inflammatory cell infiltration,bloodspinal cord barrier(BSCB)destruction and other secondary injury at the injury site,and induce extensive degeneration and apoptosis of motor neurons in the anterior horn of the spinal cord,resulting in difficulties in nerve regeneration and functional recovery.Among them,oxidative stress and inflammation are the most important processes leading to massive destruction of nerve tissue in secondary injury.After mechanical shock caused by primary traumatic violence,a large amount of reactive oxygen species(ROS)are produced at the injured site,resulting in oxidative stress,causing damage to lipids,proteins and DNA,resulting in the death of a large number of neurons.At the same time,microglia were activated after BPA to produce a large amount of interleukin-6(IL-6).Together with up-regulated pro-inflammatory cytokines such as tumor necrosis factor α(TNF-α)and interleukin-1β(IL-1β),a large number of inflammatory cells were recruited and migrated to the injured site,and the interaction produced a series of cascade reactions,which reached the peak within 24-72 hours after injury,aggravating nerve tissue edema,further reduce the survival rate of motor neurons and hinder the recovery of motor function.In order to improve the treatment satisfaction of in situ replantation after BPA,effective antiinflammatory and anti-oxidant therapies are carried out at the same time of early in situ replantation of avulsed nerve,which is of great significance to reduce secondary injury and effectively promote nerve regeneration and functional recovery.Astaxanthin(AST)is a kind of non-vitamin A carotenoid with strong fat solubility,which has the same anti-oxidant effect as carotenoids,strong ability to quench singlet oxygen and capture free radicals,and neuroprotective effect of antiinflammation and anti-apoptosis.Folic acid(FC)is an essential water-soluble B vitamin for human growth and development,which shows a strong effect in anti-inflammatory treatment.At the same time,FC is converted into tetrahydrofolic acid(THF)in the body,which is involved in the synthesis of purines and pyrimidines and the mutual transformation of amino acids,and participates in the growth and development of the nervous system,which provides a guarantee for the repair of nerve injury.Materials and methods: The model of in situ replantation of C6 nerve root after BPA injury was established in adult female SD rats.According to the principle of random distribution,BPA replantation model rats were divided into 4 groups with 18 rats in each group: operation control group(Control),astaxanthin(AST)treatment group,folic acid(FC)treatment group and astaxanthin combined with folic acid(AST+FC)treatment group.The AST group was administered via oral gavage of AST(75mg/kg)at 3 h after surgery and given intraperitoneal injection of physiological saline solution;the FC group was given intraperitoneal injection of FC(80ug/kg)physiological saline solution and olive oil(1mL/kg)via oral gavage;the AST+FC group was given intragastric administration of AST(75mg/kg)and FC(80ug/kg)physiological saline solution intraperitoneal injection;the control group was given olive oil(1mL/kg)via oral gavage and intraperitoneal injection of physiological saline solution.The methods for evaluating the efficacy were as follows:(1)24 hours after surgery,the ROS content in the acute phase of injured spinal cord tissue was measured by immunofluorescence method,and the IL-6 content in the spinal cord anterior horn tissue of the injured side C5-C7 was measured by spectrophotometry;(2)Terzis grooming behavior test(TGT)was performed once a week from 2nd to 6th weeks after surgery to evaluate the motor function of the affected limbs;(3)At the 6th week after surgery,the motoneurons in the anterior horn of the spinal cord were labeled retrograde by injecting fluorescent gold(FG)through the musculocutaneous nerve,and the number of motoneurons in the anterior horn of the injured spinal cord was measured;(4)At the 6th week after surgery,the survival rate of motoneurons in the anterior horn of the C6 segment of the injured spinal cord was measured by immunofluorescence;(5)At the 6th week after surgery,the muscle fiber diameter of the injured side of biceps brachii was measured by hematoxylin-eosin staining(HE);(6)At 6 weeks after surgery,the compound action potential of biceps brachii and musculocutaneous nerve was detected by electromyogram(EMG).Results: After treatment with AST and FC,the results showed that compared with the control group,AST group had better anti-oxidant effect than FC group,and FC group had better antiinflammatory effect than AST group at 24 hours after surgery.The combination of the two had a synergistic effect in early anti-inflammation and anti-oxidation.At six weeks after surgery,AST and FC could promote the recovery of motor function of the affected limb,increase the diameter of biceps brachii muscle fiber and the amplitude of compound action potential of biceps brachii and myocutaneous nerve,retain more functional motor neurons,and promote the survival rate of motor neurons in the anterior horn of spinal cord.Conclusions:(1)Astaxanthin and folic acid both have good anti-inflammatory and antioxidant effects.The early intake of astaxanthin showed better anti-oxidant effect than folic acid,while folic acid showed better anti-inflammatory effect,and the synergistic effect of astaxanthin and folic acid promoted the recovery of brachial plexus function.(2)After the nerve root was replanted in situ after BPA injury,the early anti-inflammatory and anti-oxidant therapy increased the survival rate of motor neurons in the anterior horn of the injured spinal cord,made them have more functional neurons and promoted the recovery of muscle indicators,promoted the recovery of nerve function,and provided a new method for clinical treatment of brachial plexus avulsion injury. |
