Changes of pro-inflammatory and anti-inflammatory macrophages after peripheral nerve injury

Macrophages are notable immune cells that are recruited to the injury sites after peripheral nerve injury. Following peripheral nerve injury, increasing numbers of macrophages engulf debris and promote nerve regeneration. However, changes of pro-inflammatory (M1) and anti-inflammatory (M2) macrophages, two types of macrophages with dissimilar biological functions, have not been discovered. In the current study, the expression profiles of M1 and M2 macrophage marker genes in the sciatic nerve stumps and dorsal root ganglions (DRGs) after rat sciatic nerve injury were determined using RNA sequencing. Robust up-regulation of macrophage marker genes was observed in the injured sciatic nerve stumps as compared with in the DRGs. Measurement of the dynamic expression levels of M1 macrophage specific marker genes CD38 and Gpr18 as well as M2 macrophage specific marker genes Egr2 and Myc suggested that M1 macrophages were highly involved at all tested time points after peripheral nerve injury while M2 macrophage might be more involved in the later phase after nerve injury. Dynamic changes of M1 macrophage-inducing miRNAs showed that miR-18a, miR-19b, miR-21, miR-29a, and miR-29b were elevated in the injured nerve stump. These up-regulated miRNAs might mediate macrophage polarization by targeting multiple genes, such as Pten. Collectively, our study explored the unique temporal patterns of pro-inflammatory and anti-inflammatory macrophages after peripheral nerve injury for genetic aspects and provided a deeper understanding of the cellular and molecular basis of microenvironment reconstruction after peripheral nerve injury.

The temporal patterns of pro-inflammatory and anti-inflammatory macrophages after peripheral nerve injury.     

神经预变性促进周围神经桥接后神经再生的初步研究

目的探讨经过体内预变性的神经用于周围神经缺损桥接修复的效果。方法 SD大鼠20只,制作右侧坐骨神经压榨伤动物模型,3 d后,取坐骨神经用于对侧行神经桥接,在桥接后0 d、3 d、7 d、14 d取材,应用ED1和NF200染色比较双侧神经再生速度及神经纤维内巨噬细胞浸入情况。结果压榨伤后3 d,远端神经纤维内见大量ED1染色阳性巨噬细胞侵入,NF200阳性染色成棒状或碎片状;神经桥接后3 d、7 d、14 d,预变性组与对照组桥接远端均可见大量ED1染色阳性巨噬细胞侵入,经过预变性的神经内神经再生速度明显提高。结论 经过体内预变性的神经用于周围神经缺损桥接修复可明显促进神经再生,其机制可能是巨噬细胞的早期侵入,有利于神经生长抑制物的清除。     

Conductive conduit small gap tubulization for peripheral nerve repair

Despite advances in surgical techniques, functional recovery following epineurial neurorrhaphy of transected peripheral nerves often remains quite unsatisfactory. Small gap tubulisation is a promising approach that has shown potential to traditional epineurial neurorrhaphy in the treatment of peripheral nerve injury. Thus, the goal of this study is to evaluate sciatic nerve regeneration after nerve transection, followed by small gap tubulization using a reduced graphene oxide-based conductive conduit. In vitro, the electrically conductive conduit could promote Schwann cell proliferation through PI3K/Akt signaling pathway activation. In vivo, the results of electrophysiological and walking track analysis suggest that the electrically conductive conduit could promote sensory and motor nerve regeneration and functional recovery, which is based on the mechanisms of selective regeneration and multiple-bud regeneration. These promising results illustrate electrically conductive conduit small gap tubulization as an alternative approach for transected peripheral nerve repair.

rGO-based conductive nerve conduit as a scaffold to bridge peripheral nerve transected injury and 2 mm gap provides a suitable microenvironment for axons selective regeneration.     

CSF-1 signaling mediates recovery from acute kidney injury

Renal tubule epithelia represent the primary site of damage in acute kidney injury (AKI), a process initiated and propagated by the infiltration of macrophages. Here we investigated the role of resident renal macrophages and dendritic cells in recovery from AKI after ischemia/reperfusion (I/R) injury or a novel diphtheria toxin–induced (DT-induced) model of selective proximal tubule injury in mice. DT-induced AKI was characterized by marked renal proximal tubular cell apoptosis. In both models, macrophage/dendritic cell depletion during the recovery phase increased functional and histologic injury and delayed regeneration. After I/R-induced AKI, there was an early increase in renal macrophages derived from circulating inflammatory (M1) monocytes, followed by accumulation of renal macrophages/dendritic cells with a wound-healing (M2) phenotype. In contrast, DT-induced AKI only generated an increase in M2 cells. In both models, increases in M2 cells resulted largely from in situ proliferation in the kidney. Genetic or pharmacologic inhibition of macrophage colony-stimulating factor (CSF-1) signaling blocked macrophage/dendritic cell proliferation, decreased M2 polarization, and inhibited recovery. These findings demonstrated that CSF-1–mediated expansion and polarization of resident renal macrophages/dendritic cells is an important mechanism mediating renal tubule epithelial regeneration after AKI.     

Expression of the lactate transporter MCT1 in macrophages

This study evaluated macrophage expression of the stereospecific lactate transporter, MCT1, and the effects of lipopolysaccharide (LPS), tumor necrosis factor (TNFa), or nitric oxide (NO) on MCT1 mRNA and protein levels and lactate transporter activity. Peritoneal and J774.1 macrophages were treated with either saline, LPS (10 or 100 ng/mL), dexamethasone (100 nM), and dexamethasone + LPS. Cells were harvested at 4, 8, and 16 h after treatment and processed for total RNA and protein isolation. LPS treatment significantly increased macrophage MCT1 mRNA expression at 4 and 8 h compared with the saline-treated cells. Dexamethasone did not alter MCT1 mRNA levels. Treatment of J774.1 macrophages with TNFalpha (1 ng/mL) or nitric oxide (DETA-NO, 100 microM) also significantly increased MCT1 mRNA levels at 4 and 8 h after treatment. LPS and TNFalpha treatment significantly increased MCT1 protein levels at 8 and 16 h after treatment. Lactate transporter activity in J774.1 macrophages was measured by uptake of 14C-labeled lactate. LPS and TNFalpha treatment significantly augmented lactate uptake, 12 h after administration; however, nitric oxide treatment did not affect lactate uptake. Thus, our data demonstrated that stimulated peritoneal and J774.1 macrophages express the lactate transporter, MCT, and that LPS and TNFalpha regulate MCT1 mRNA and protein levels.     

周围神经损伤的早期显微外科修复

目的探索周围神经损伤早期显微外科修复的临床效果及预后。方法根据神经损伤的部位及程度应用不同的显微外科方法进行修复。具体方法为神经探查、神经松解、神经外膜修补、神经外膜端端吻合、神经束膜端端吻合、神经移植、神经移位、神经植入等。结果共修复周围神经118例12条166处，获随访72例12条98处，运动功能恢复达M3以上31．82％，感觉功能恢复达S3以上67．74％，其中前臂内外侧皮神经、股外侧皮神经、腓肠神经损伤修复后感觉恢复均达到S3，28处指神经损伤修复后感觉恢复达s3以上占82．14％，尺神经、腓总神经的运动功能无一例恢复，桡神经及股神经的运动功能恢复最理想。结论应用显微外科技术早期修复周围神经损伤效果良好，但应注意修复时机及方式。     

Penetrating injuries to the nerves of the lower extremity: principles of diagnosis and treatment

Background. Lower extremity nerve injuries caused by wounds are often not noticed immediately after trauma. The purpose of this article was to analyze the localization of penetrating injuries to the nerves, the mechanism and extent of the lesions, and the microsurgical techniques used. The diagnostic and therapeutic basics in penetrating injuries of lower extremity nerves are also described. Material and methods. The clinical material consisted of 67 patients treated surgically for penetrating injuries of lower extremity nerves. Results. In our material we observed penetrating injuries to the common peroneal nerve (41 cases), tibial nerve (9 cases), sciatic nerve (6 cases), combined common peroneal and tibial nerves (8 cases), and miscellaneous (foot injuries, 3 cases). The mechanism of injury included 51 cases of neurotmesis (primary injuries) and 16 cases of nerve compression (secondary injuries). In 5 cases, lesions of the major vessels and common peroneal and tibial nerves were observed. Conclusions. Penetrating injuries to the common peroneal nerve are the most frequent lesions of the peripheral nervous system within the lower limbs. The early detailed inspection of wounds, especially those localized in areas posing a particular threat to peripheral nerves, is an essential part of surgical treatment.     

Accelerating axonal growth promotes motor recovery after peripheral nerve injury in mice

Although peripheral nerves can regenerate after injury, proximal nerve injury in humans results in minimal restoration of motor function. One possible explanation for this is that injury-induced axonal growth is too slow. Heat shock protein 27 (Hsp27) is a regeneration-associated protein that accelerates axonal growth in vitro. Here, we have shown that it can also do this in mice after peripheral nerve injury. While rapid motor and sensory recovery occurred in mice after a sciatic nerve crush injury, there was little return of motor function after sciatic nerve transection, because of the delay in motor axons reaching their target. This was not due to a failure of axonal growth, because injured motor axons eventually fully re-extended into muscles and sensory function returned; rather, it resulted from a lack of motor end plate reinnervation. Tg mice expressing high levels of Hsp27 demonstrated enhanced restoration of motor function after nerve transection/resuture by enabling motor synapse reinnervation, but only within 5 weeks of injury. In humans with peripheral nerve injuries, shorter wait times to decompression surgery led to improved functional recovery, and, while a return of sensation occurred in all patients, motor recovery was limited. Thus, absence of motor recovery after nerve damage may result from a failure of synapse reformation after prolonged denervation rather than a failure of axonal growth.     

Enhanced in vivo survival of Schwann cells by a synthetic oxygen carrier promotes sciatic nerve regeneration and functional recovery

Local hypoxia in the early stages of peripheral nerve injury is a challenge for axonal regeneration. To address this issue, perfluorotributylamine (PFTBA)‐based oxygen carrying fibrin hydrogel was prepared and injected into Schwann cell (SC)‐seeded collagen‐chitosan conduits to increase oxygen supply to SCs within the conduits. The conduit containing PFTBA‐SC gel was then applied to bridge a 15‐mm sciatic nerve defect in rats. It was observed that most of the GFP‐labeled SCs initially seeded in the PFTBA hydrogel remained alive for approximately 28 days after their in vivo implantation. The number of SCs was significantly higher in the PFTBA‐SC scaffold than that in the SC scaffold without PFTBA. In addition, nerve regeneration and functional recovery were examined after nerve injury repair. We found that the PFTBA‐SC scaffold was capable of promoting axonal regeneration and remyelination of the regenerated axons. Further studies showed the PFTBA‐SC scaffold was able to accelerate the recovery of motor and sensory function of the regenerating nerves. Electrophysiological analysis showed area under the curve of compound muscle action potential and nerve conduction velocity were also improved, and gastrocnemius muscle atrophy was partially reversed by PFTBA‐SC scaffold. Furthermore, microvessel density analysis showed PFTBA‐SC composites were beneficial for microvascular growth, which provided sustained oxygen for regenerating nerve in the later stages of nerve regeneration. In conclusion, enhanced survival of SCs by PFTBA is capable of promoting sciatic nerve regeneration and functional recovery, which provides a new avenue for achieving better functional recovery in the treatment of peripheral nerve injuries. Copyright © 2016 John Wiley & Sons, Ltd.     

经颅磁电刺激促进周围神经再生的电生理学研究

目的;研究经颅磁电刺激后损伤坐骨神经的电生理学变化,探索一种促进周围神经功能恢复的有效治疗方法。方法：用电生理学方法观察磁电刺激对周围神经恢复的影响,并与对照组进行比较。结果：磁电刺激组受损坐骨神经的潜伏期较对照组缩短,差异有显著意义。实验组的波幅较对照组增高,神经传导速度也较对照组增快,但无显著差异。结论：经颅磁电刺激可能具有促进受损周围神经再生和传导功能恢复的作用。     

Sutureless nerve repair at the fascicular level using a nerve coupler

Peripheral nerves are transected in many traumatic injuries of the extremities. Satisfactory functional regeneration of such nerves often fails to occur after repair with sutures. Possible reasons for these failures include poor alignment of nerves or fascicles, intrusion of scar tissue into the nerve junction, and outgrowth of nerve tissue from the repair site. This animal study describes an experimental method of sutureless, monofascicular peripheral nerve repair using a resorbable nerve coupler in the rat model. The first version of this coupler shows approximately equal performance to suture repair. Histology and electrophysiology assessments after regeneration showed that the polyglycolic acid (PGA) tube repairs were functionally equal to monofascicular suture junctions as well as being quicker and simpler to perform. Modified coupler designs based on this and other work show greater promise. Collateral studies are using similar versions of the nerve coupler as a vehicle for the insertion of chemical and neuro-electronic factors that may enhance nerve regeneration.     

A (heat) shock to the system promotes peripheral nerve regeneration

Peripheral nerves are easily damaged, resulting in loss of motor and sensory function. Recovery of motor and sensory function after peripheral nerve injury is suboptimal, even after appropriate surgical repair. This is due to the slow rate of axonal elongation during regeneration and atrophic changes that occur in denervated Schwann cells and target muscle with proximal lesions. One way to solve this problem is to accelerate the rate at which the axons regenerate. In this issue of the JCI, Ma and colleagues show that this can be achieved in mice by overexpression of heat shock protein 27, providing hope for enhanced functional recovery in patients after peripheral nerve damage.     

周围神经术前肌电图结果与术中所见的比较研究及误诊原因分析

目的 探讨肌电图(EMG)检查对周围神经损伤的诊断意义，分析误诊的原因。方法 收集2000年1月至2003年4月行手术治疗的周围神经损伤患者63例(69条神经)，按神经损伤特点分为开放性周围神经损伤组、闭合性周围神经损害组、臂丛损伤组和神经修复后再生组，各组患者均于术前进行肌电图检测，并将检测结果与术中所见进行比较、分析。结果 开放性周围神经损伤组术前EMG对神经完全损伤的诊断符合率为73.08％，与术中所见结果比较，差异有统计学意义。闭合性周围神经损害组对受损神经的定性、定位诊断，均在术中得到证实。臂丛损伤组的大体定位正确率达96．30％，完全符合率达70．37％；对臂丛完全根性损伤的检出率为68．52％，与磁共振的检出率(55．56％)相比，差异无统计学意义。神经修复后再生组5条神经，EMG结果与术中所见3条符合，2条不符合。69条神经中，EMG检查完全符合率为71.01％，基本符合率为85．51％，完全不符率为13．04％；假阳性率为4．49％，假阴性率为22．73％。结论 EMG检查对损伤神经的定位、定性诊断及神经修复后再生状况的评价在临床诊治中具有重要的指导意义，但可出现假阳性及假阴性结果，且以运动诱发电位的假阴性为多。术前EMG与磁共振检查相结合，可提高对臂丛神经完全根性损伤的检出率。     

同种异体神经复合体修复兔周围神经缺损

背景：应用种植许旺细胞的去细胞同种异体神经复合体修复周围神经缺损,探索其对神经再生及功能恢复有更好的促进作用,并且免疫原性非常小。目的：用种植胎兔许旺细胞的去细胞同种异体神经复合体修复兔缺损的坐骨神经,观察移植神经周围免疫细胞的变化及功能恢复。方法：48只新西兰白兔随机分成实验组和对照组。两组动物均切除一段坐骨神经,造成2.0cm长的缺损,实验组用种植胎兔许旺细胞的同种异体神经复合体修复坐骨神经;对照组仅用去细胞同种异体神经修复。移植后1,4,8周光镜观察移植段坐骨神经周围肌肉组织中免疫细胞的浸润情况,计数每个高倍视野免疫细胞的数量。移植后4,8,16周大体观察兔的足部溃疡形成及愈合情况,大体观察神经愈合情况;肌电图检查桥接段坐骨神经的传导速度。结果与结论：手术区局部均未出现明显的排斥反应,实验组足部溃疡愈合情况优于对照组。移植后1周移植段坐骨神经周围肌肉组织中有大量淋巴细胞及巨噬细胞浸润,实验组明显多于对照组（P〈0.05）;移植后4周,浸润的免疫细胞两组均较1周后明显减少,实验组减少更明显。移植后8周,浸润的免疫细胞更加减少,但两组间比较差异无显著性意义（P〉0.05）。移植后4周时,两组均未见明显的神经传导,8,16周神经传导速度实验组均优于对照组（P〈0.05）。提示,种植许旺细胞的去细胞同种异体神经复合体免疫原性非常小,对神经再生及功能恢复有更好的促进作用。     

坐骨神经牵拉伤模型MR扩散张量成像与病理的对照

背景：磁共振弥散张量成像可以显示周围神经损伤的弥散变化并进行定量研究,因而在显示神经损伤及再生方面具有良好的应用前景。目的：探讨兔坐骨神经急性牵拉伤弥散张量成像的可靠性,明确弥散张量参数在神经损伤诊断中的价值及病理学基础。方法：选取32只新西兰白兔建立右后肢坐骨神经退变与修复模型,左后肢为假手术侧。采用1．5TMRI机于术后1d,3d,1周,2周,3周,4周,6周,8周行双侧坐骨神经弥散张量成像,进行DTT重建,测量各向异性分数、表观扩散系数;然后进行病理检查。结果与结论：牵拉伤后1d弥散张量成像仅显示神经近段,损伤段及远段中断;牵拉伤后1周远段出现细、短纤维束;牵拉伤后2-6周远段纤维束增多、增粗;牵拉伤8周神经纤维大部分恢复正常。1d-8周牵拉段、牵拉远段各向异性分数值与假手术侧差异有显著性意义（P〈0．05）;1d-1周牵拉近段各向异性分数值与假手术侧差异有显著性意义（P〈0．05）。1-8周不同牵拉段表观扩散系数值与假手术侧差异均无显著性意义。神经牵拉伤早期各向异性分数值下降的病理改变是髓鞘板层疏松,崩解,轴索崩解;各向异性分数值升高的病理基础是髓鞘、轴索再生。结果可见DTT纤维示踪成像可清晰、直观、早期显示兔坐骨神经牵拉伤的异常改变,各向异性分数值测量可作为监测坐骨神经牵拉伤后退变及再生的敏感方法。     

Treatment of traumatic peripheral nerve injury

Peripheral nerve injuries are caused by traction, laceration and missile injury. Primary surgical repair is recommended for clean, sharp injuries that cause transection of a nerve. In compressed, stretched or contused nerves, surgical repair at three months is indicated if functional recovery has not occurred. Electromyography and nerve conduction studies are helpful in deciding which patients need secondary repair. Recovery is possible for 18 months following injury. Since nerve regeneration occurs at a rate of one inch per month, the distance from the nerve injury to the innervated muscle must be less than 18 inches. Therefore, the outcome is generally better in distal lesions than in proximal ones.     

Niemann-Pick C1 protects against atherosclerosis in mice via regulation of macrophage intracellular cholesterol trafficking

Niemann-Pick C1 (NPC1) is a key participant in cellular cholesterol trafficking. Loss of NPC1 function leads to defective suppression of SREBP-dependent gene expression and failure to appropriately activate liver X receptor-mediated (LXR-mediated) pathways, ultimately resulting in intracellular cholesterol accumulation. To determine whether NPC1 contributes to regulation of macrophage sterol homeostasis in vivo, we examined the effect of NPC1 deletion in BM-derived cells on atherosclerotic lesion development in the Ldlr-/- mouse model of atherosclerosis. High-fat diet-fed chimeric Npc1-/- mice reconstituted with Ldlr-/-Npc1-/- macrophages exhibited accelerated atherosclerosis despite lower serum cholesterol compared with mice reconstituted with wild-type macrophages. The discordance between the low serum lipoprotein levels and the presence of aortic atherosclerosis suggested that intrinsic alterations in macrophage sterol metabolism in the chimeric Npc1-/- mice played a greater role in atherosclerotic lesion formation than did serum lipoprotein levels. Macrophages from chimeric Npc1-/- mice showed decreased synthesis of 27-hydroxycholesterol (27-HC), an endogenous LXR ligand; decreased expression of LXR-regulated cholesterol transporters; and impaired cholesterol efflux. Lower 27-HC levels were associated with elevated cholesterol oxidation products in macrophages and plasma of chimeric Npc1-/- mice and with increased oxidative stress. Our results demonstrate that NPC1 serves an atheroprotective role in mice through regulation of LXR-dependent cholesterol efflux and mitigation of cholesterol-induced oxidative stress in macrophages.     

Single session of brief electrical stimulation immediately following crush injury enhances functional recovery of rat facial nerve

Peripheral nerve injuries lead to a variety of pathological conditions, including paresis or paralysis when the injury involves motor axons. We have been studying ways to enhance the regeneration of peripheral nerves using daily electrical stimulation (ES) following a facial nerve crush injury. In our previous studies, ES was not initiated until 24 h after injury. The current experiment tested whether ES administered immediately following the crush injury would further decrease the time for complete recovery from facial paralysis. Rats received a unilateral facial nerve crush injury and an electrode was positioned on the nerve proximal to the crush site. Animals received daily 30 min sessions of ES for 1 d (day of injury only), 2 d, 4 d, 7 d, or daily until complete functional recovery. Untreated animals received no ES. Animals were observed daily for the return of facial function. Our findings demonstrated that one session of ES was as effective as daily stimulation at enhancing the recovery of most functional parameters. Therefore, the use of a single 30 min session of ES as a possible treatment strategy should be studied in human patients with paralysis as a result of acute nerve injuries.     

地震致周围神经损伤的超声特征

目的 探讨地震所致周围神经损伤患者的晚期超声特征。方法 对34例地震所致周围神经损伤患者于伤后1年行高频超声检查,并与手术结果比较。结果 34例患者中,超声检出周围神经异常68条;9例为1条神经损伤, 17例2条神经损伤,8例累及3条及以上神经损伤。其中神经与周围瘢痕组织粘连、卡压48条,神经完全断裂6条,神经吻合术后5条,截肢术后神经末端创伤性神经瘤形成9条。超声与手术结果的符合率为97.06%。结论 地震所致周围神经损伤晚期以多条神经同时受损、1条神经多处损伤为特征,主要为瘢痕粘连、卡压所致。超声可对神经损伤进行定性和定位诊断。     

Vagal nerve stimulation blocks peritoneal macrophage inflammatory responsiveness after severe burn injury

ABSTRACT: Large surface area burn injuries lead to activation of the innate immune system, which can be blocked by parasympathetic inputs mediated by the vagus nerve. We hypothesized that vagal nerve stimulation (VNS) would alter the inflammatory response of peritoneal macrophages after severe burn injury. Male BALB/c mice underwent right cervical VNS before 30% total body surface area steam burn and were compared with animals subjected to burn alone. Peritoneal macrophages were harvested at several time points following injury and exposed to lipopolysaccharide (LPS) in culture conditions. The inflammatory response of peritoneal macrophages was measured by analyzing changes in nuclear factor κB p65 phosphorylation using flow cytometry. We found that peritoneal macrophages isolated from mice subjected to burn injury were hyperresponsive to LPS challenge, suggesting burn-induced macrophage activation. We identified a protective role for VNS in blocking peritoneal macrophage activation. Analysis of the phosphorylation state of nuclear factor κB pathway mediator, p65 Rel A, revealed a VNS-mediated reduction in p65 phosphorylation levels after exposure to LPS compared with burn alone. In combination, these studies suggest VNS mediates the inflammatory response in peritoneal macrophages by affecting the set point of LPS responsiveness.