Transection Injury Research Articles

Neuroregenerative effects of polyethylene glycol and FK-506 in a rat model of sciatic nerve injury

The recently introduced polyethylene glycol (PEG) treatment restores axonal continuity after nerve injury, leading to rapid recovery of nerve function. The impact of PEG therapy on neuroregeneration has not yet been compared with any intervention with an established proneuroregenerative potential. FK-506 is an immunosuppressive agent with documented proneuroregenerative potential in nerve injury models. The aim of this study was to compare the effects of PEG therapy and preinjury FK-506 administration in rats with sciatic nerve transection injury. Four groups of male Sprague Dawley rats (seven per group) underwent sciatic nerve transection with primary repair. Group A received placebo injections, group B placebo injections and PEG treatment, group C FK-506 injections, and group D both FK-506 injections and PEG treatment. Clinical outcomes were assessed by the skin prick test and Sciatic Functional Index (SFI). Regenerated nerves underwent histomorphometric analysis. The histomorphometric analysis demonstrated that compared with the controls, nerve specimens from all treated groups showed signs of enhanced neuroregeneration (higher mean axonal area) (p<0.001). The histomorphometric parameters for group D (PEG + FK-506), mean axonal area (p<0.001) and axonal count (p>0.05), were significantly better than those in the other study groups. The Form factor was closest to its optimal values in group B (p<0.0001). At the end of the study, mean skin prick test scores in all treated groups were significantly higher than those in controls (p>0.05). During the first postoperative week, PEG-treated rats (groups B and D) presented with higher values of the SFI than animals from groups A and C, but the difference was not statistically significant. Combined therapy with PEG and FK-506 seems to produce better neuroregeneration outcomes than a simple suture-based repair complemented with either PEG or FK-506 treatment.

Laryngeal adductor function following potassium titanyl phosphate laser welding of the recurrent laryngeal nerve.

Recurrent laryngeal nerve (RLN) transection injuries may occur during thyroidectomy and other surgical procedures. Laser nerve welding has been shown to cause less technique-related axonal damage than the traditional suture method. We compared functional adductor results using these two methods of RLN repair. Animal model. Canine hemilarynges underwent pretreatment testing of laryngeal adductor function, followed by RLN transection and repair using potassium titanyl phosphate (KTP) laser welding (n = 8) or microneural suture (n = 16) techniques. Six months later, adductor function was measured again and expressed as a proportion of the pretreatment value. The mean laryngeal adductor pressure ratios were 82.4% (95% confidence interval [CI]: 72.8%-92.0%) for the laser repair group and 55.5% (95% CI: 49.4%-61.6%) for the suture control group, with a difference of 26.9% (95% CI: 15.3%-38.5%). Both spontaneous and stimulated glottic closure was observed in the laser welding and microsuture repair groups. Laser nerve welding resulted in greater strength of adduction than suture repair of an acutely transected RLN. Suture anastomosis may traumatize more axons than the laser. Stronger vocal fold adduction is associated clinically with better protection from aspiration and improved voice outcomes. KTP laser welding should be considered for anastomosis of the RLN and other nerves. NA Laryngoscope, 130:1764-1769, 2020.

Classic axon guidance molecules control correct nerve bridge tissue formation and precise axon regeneration.

The peripheral nervous system has an astonishing ability to regenerate following a compression or crush injury; however, the potential for full repair following a transection injury is much less. Currently, the major clinical challenge for peripheral nerve repair come from long gaps between the proximal and distal nerve stumps, which prevent regenerating axons reaching the distal nerve. Precise axon targeting during nervous system development is controlled by families of axon guidance molecules including Netrins, Slits, Ephrins and Semaphorins. Several recent studies have indicated key roles of Netrin1, Slit3 and EphrinB2 signalling in controlling the formation of new nerve bridge tissue and precise axon regeneration after peripheral nerve transection injury. Inside the nerve bridge, nerve fibroblasts express EphrinB2 while migrating Schwann cells express the receptor EphB2. EphrinB2/EphB2 signalling between nerve fibroblasts and migrating Schwann cells is required for Sox2 upregulation in Schwann cells and the formation of Schwann cell cords within the nerve bridge to allow directional axon growth to the distal nerve stump. Macrophages in the outermost layer of the nerve bridge express Slit3 while migrating Schwann cells and regenerating axons express the receptor Robo1; within Schwann cells, Robo1 expression is also Sox2-dependent. Slit3/Robo1 signalling is required to keep migrating Schwann cells and regenerating axons inside the nerve bridge. In addition to the Slit3/Robo1 signalling system, migrating Schwann cells also express Netrin1 and regenerating axons express the DCC receptor. It appears that migrating Schwann cells could also use Netrin1 as a guidance cue to direct regenerating axons across the peripheral nerve gap. Engineered neural tissues have been suggested as promising alternatives for the repair of large peripheral nerve gaps. Therefore, understanding the function of classic axon guidance molecules in nerve bridge formation and their roles in axon regeneration could be highly beneficial in developing engineered neural tissue for more effective peripheral nerve repair.

Prothrombin, alone or in complex concentrates or plasma, reduces bleeding in a mouse model of blood exchange-induced coagulopathy

Prothrombin complex concentrates (PCC) are fractionated plasma protein drugs that reverse warfarin anticoagulation. PCC may control more general bleeding. We sought to identify the dominant procoagulant factor in PCC in vivo. We tested PCC or coagulation factor (F) treatment in CD1 mice made coagulopathic by exchange of whole blood for washed red cells. Anesthetized mice were transfused with murine fresh-frozen plasma (mFFP), PCC, mixtures of human vitamin K-dependent proteins (VKDP) (prothrombin, FVII, FIX, or FX), or purified single human VKDP, immediately prior to tail transection (TT), liver laceration (LL), or intravascular laser injury (ILI). Plasma donor mice were treated with vehicle or control antisense oligonucleotide (ASO-CON) or ASO specific for prothrombin (FII) (ASO-FII) to yield mFFP or ASO-CON mFFP or ASO-FII mFFP. Blood losses were determined spectrophotometrically (TT) or gravimetrically (LL). Thrombus formation was quantified by intravital microscopy of laser-injured arterioles. PCC or four factor- (4F-) VKDP or prothrombin significantly reduced bleeding from TT or LL. Omission of prothrombin from 4F-VKDP significantly reduced its ability to limit bleeding. Mice transfused with ASO-FII mFFP demonstrated inferior haemostasis versus those transfused with ASO-FII following TT, LL, or ILI. Prothrombin is the dominant procoagulant component of PCC and could limit bleeding in trauma.

Local FK506 delivery at the direct nerve repair site improves nerve regeneration.

The objective of this study is to assess the efficacy of local tacrolimus (FK506) delivery to improve outcomes in the setting of nerve transection injury. FK506 embedded poly(lactide-co-caprolactone) films capable of extended, localized release of FK506 were developed. FK506 rate of release testing and bioactivity assay was performed. Mouse sciatic nerve transection and direct repair model was used to evaluate the effect extended, local delivery of FK506 had on nerve regeneration outcomes. Linear release of FK506 was observed for 30 days and released FK506 matched control levels of neurite extension in the dorsal root ganglion assay. Groups treated with local FK506 had greater gastrocnemius muscle weight, foot electromyogram, and number of axons distal of the repair site than non-FK506 groups. Results of this study indicate that extended, localized delivery of FK506 to nerve injuries can improve nerve regeneration outcomes in a mouse sciatic nerve transection and repair.

Thoracic Spinal Cord Hemisection Surgery and Open-Field Locomotor Assessment in the Rat.

Spinal cord injury (SCI) causes disturbances in motor, sensory, and autonomic function below the level of the lesion. Experimental animal models are valuable tools to understand the neural mechanisms involved in locomotor recovery after SCI and to design therapies for clinical populations. There are several experimental SCI models including contusion, compression, and transection injuries that are used in a wide variety of species. A hemisection involves the unilateral transection of the spinal cord and disrupts all ascending and descending tracts on one side only. Spinal hemisection produces a highly selective and reproducible injury in comparison to contusion or compression techniques that is useful for investigating neural plasticity in spared and damaged pathways associated with functional recovery. We present a detailed step-by-step protocol for performing a thoracic hemisection at the T8 vertebral level in the rat that results in an initial paralysis of the hindlimb on the side of the lesion with graded spontaneous recovery of locomotor function over several weeks. We also provide a locomotor scoring protocol to assess functional recovery in the open-field. The locomotor assessment provides a linear recovery profile and can be performed both early and repeatedly after injury in order to accurately screen animals for appropriate time points in which to conduct more specialized behavioral testing. The hemisection technique presented can be readily adapted to other transection models and species, and the locomotor assessment can be used in a variety of SCI and other injury models to score locomotor function.

Prognostic imaging of iatrogenic and traumatic ureteral injury by near-infrared fluorescence.

Iatrogenic or traumatic ureteral injuries are life-threatening but difficult to diagnose early. Ureteral visualization is essential for both the prevention and diagnosis of iatrogenic or traumatic ureter injuries. In the present study, we evaluated the feasibility of near-infrared (NIR) with ZW800-1C as a diagnostic tool of iatrogenic or traumatic ureteral injury in addition to ureter visualization, compared to methylene blue. With mice model, we compared the image quality of ZW800-1C with methylene blue for ureter visualization. We also made ureter perforation, obstruction, crushing injury, and transection model with mice and evaluated the feasibility of ZW800-1C for diagnostic tool for ureteral injuries. We could confirm the ureter in the ZW800-1C images in maximally 30 minutes after injection, and the ureter was visible until NIR imaging concluded at 180 minutes after injection. However, methylene blue failed to provide clear ureter imaging during the same period. ZW800-1C imaging successfully visualized ureters subjected to obstruction, transection, perforation, and crush injuries, although urinary leakage was not visible by eye. Our results indicate ZW800-1C is better suited for ureter visualization than methylene blue and that ZW800-1C has considerable potential for the early diagnosis of various ureteral injuries.

Different functional bio-scaffolds share similar neurological mechanism to promote locomotor recovery of canines with complete spinal cord injury

Many studies have shown that rodents exhibit a certain degree of spontaneous motor function recovery even if they suffer from spinal cord complete transection injury. However, the characteristics of spontaneous locomotor recovery and its associated neurobiological mechanisms are unclear. In this study, we observed that spontaneous locomotor function recovery of hind limbs could also be detected in a canine thoracic (T8) spinal cord complete transection model. In addition, the spontaneous locomotor recovery of canines could be further promoted by chronic implantation of Taxol- or human bone marrow mesenchymal stem cell-modified bio-scaffolds. Moreover, functional bio-scaffolds implantation promoted locomotor outcome could be significantly weakened (drop to the spontaneous recovery level) but not totally abolished by resection in the lesion site. The neurological mechanism for functional bio-scaffolds improved locomotor outcome was primarily dependent on the formation of neuronal bridging but not the long-distance regeneration of descending motor axons throughout the lesion gap. Besides that, we found that spontaneously achieved locomotor recovery of hind limbs was unable to be weaken by repetitive resection of the lesion area, indicating the mechanism for spontaneous locomotor recovery was independent on functional neurological bridging throughout the lesion gap.

Endovascular Repair of Axillary Artery Transection with a Stent Graft following Blunt Trauma

Transection injuries of the axillary artery are rare and typically involve surgical repair. This case describes an emergent endovascular treatment option, using a stent graft, in a patient that was deemed as high risk for open surgery.

Impact of Spinal Cord Injury and Chronically Induced Orthostatic Hypotension on Left Ventricular Contractility and Stiffness

IntroductionComplete spinal cord injury (SCI) above the T3 spinal level is associated impaired left ventricular (LV) systolic function. However, the effect on diastolic structure and function has yet to be examined. Furthermore, high thoracic SCI impairs centrally‐derived cardiovascular responses to postural change, leading to the development of orthostatic hypotension (OH) post‐SCI. While it has been demonstrated that these frequent bouts of OH cause impairments in cerebrovascular function, it is not known whether this hemodynamic instability also impairs cardiac function.MethodsThis study examined the effect of SCI on LV systolic and diastolic function in the presence or absence of daily bouts of acutely induced OH. 22 rats were divided into four groups: 1. Rats with a sham injury and no daily OH (SHAM, n=5), 2. Rats with a sham injury and daily induced OH (SHAM‐OH, n=6), 3. Rats with a complete T3 transection injury and daily induced OH (T3‐OH, n=5), 4. Rats with a complete T3 transection and no daily OH (T3‐SCI, n=6). 9 weeks after surgery, LV pressure‐volume (PV) catheterization was performed to assess LV basal PV indices, as well as cardiac contractility and stiffness. Furthermore, the coupling of the arterial system and the left ventricle was characterized to examine the influence of SCI and/or OH on the efficiency of the interaction between the LV and arterial system.ResultsCompared to both SHAM and SHAM‐OH, the T3‐SCI and T3‐OH groups experienced significant reductions in systolic blood pressure, LV stroke work and cardiac output (all p&lt;0.023). The T3‐OH group demonstrated an increase in arterial elastance compared to both the SHAM‐OH and SHAM groups (p&lt;0.014). T3‐SCI and T3‐OH groups exhibited reduced end‐systolic elastance compared to both SHAM and SHAM‐OH (p&lt;0.04). No difference was found in LV stiffness between the four groups. Finally, the ratio of ventricular‐vascular coupling was found to be significantly increased in the T3‐OH group compared to all other groups (all P&lt;0.019).ConclusionComplete high thoracic and cervical SCI causes a reduction in LV contractile function. Combined high thoracic SCI and daily OH impairs ventricular‐vascular coupling via changes in arterial compliance.Support or Funding InformationHeart and Stroke Foundation of Canada (HSFC), International Collaborations on Repair Discoveries (ICORD), Natural Sciences and Engineering Research Council of Canada (NSERC), Blusson Integrated Cures Partnership (BICP).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Abstract 88: Local Delivery of FK506 to a Mouse Sciatic Nerve Injury Increases Nerve Regeneration Outcomes

PURPOSE: In the clinic, there are limited treatment strategies for the repair of peripheral nerve injuries, and the majority of off-the-shelf nerve repair devices lack added functionality. Direct repair is among the most commonly performed nerve repair procedures and presently there is no clinical therapeutic available that improves outcomes after direct repair. The objective of this study is to assess the efficacy of local, controlled delivery of FK506 to improve nerve regeneration outcomes in the setting of nerve transection injury and repair. METHODS: Solvent casting techniques were used to embed FK506 into poly(lactide-co-caprolactone) (PLC) films for the creation of a nerve wrap – drug delivery system that is capable of an extended, localized release of FK506 to injured nerves. In vitro drug rate of release testing and drug bioactivity assays were performed to determine the FK506 release profile and to verify release FK506 bioactivity. A mouse sciatic transection and direct-suture repair model was used to evaluate the effect local, controlled FK506 delivery could have on nerve regeneration outcomes greater than direct-suture repair alone. Animals were sacrificed at 6 weeks for electrophysiological assessment, determination of gastrocnemius muscle mass recovery, and sciatic nerve histological evaluation. RESULTS: A linear release (R2=0.991) of FK506 for 30+ days was observed for two FK506 loading concentrations (0.01 % and 0.05% w/w of FK506/PLC). The released FK506 matched control FK506 levels of neurite extension in the dorsal root ganglion assay. Relative gastrocnemius muscle weight, relative foot EMG, and total number of axons distal of the repair site were significantly greater in mice treated with the 0.01% FK506 nerve wrap than the non-drug groups. For the 0.05% nerve wraps, the total axon count distal to the repair site was found to be significantly greater, but no significant differences were observed for the other metrics. CONCLUSION: Results of this study indicate that extended, localized delivery of FK506 to a mouse sciatic transection and direct repair can improve nerve regeneration outcomes in a sciatic nerve transection and repair model. A dose-dependent response in the nerve regeneration metrics was observed, indicating there is an optimal dose range for local delivery of FK506.

Effect of lesion proximity on the regenerative response of long descending propriospinal neurons after spinal transection injury

BackgroundThe spinal cord is limited in its capacity to repair after damage caused by injury or disease. However, propriospinal (PS) neurons in the spinal cord have demonstrated a propensity for axonal regeneration after spinal cord injury. They can regrow and extend axonal projections to re-establish connections across a spinal lesion. We have previously reported differential reactions of two distinct PS neuronal populations—short thoracic propriospinal (TPS) and long descending propriospinal tract (LDPT) neurons—following a low thoracic (T10) spinal cord injury in a rat model. Immediately after injury, TPS neurons undergo a strong initial regenerative response, defined by the upregulation of transcripts to several growth factor receptors, and growth associated proteins. Many also initiate a strong apoptotic response, leading to cell death. LDPT neurons, on the other hand, show neither a regenerative nor an apoptotic response. They show either a lowered expression or no change in genes for a variety of growth associated proteins, and these neurons survive for at least 2 months post-axotomy. There are several potential explanations for this lack of cellular response for LDPT neurons, one of which is the distance of the LDPT cell body from the T10 lesion. In this study, we examined the molecular response of LDPT neurons to axotomy caused by a proximal spinal cord lesion.ResultsUtilizing laser capture microdissection and RNA quantification with branched DNA technology, we analyzed the change in gene expression in LDPT neurons following axotomy near their cell body. Expression patterns of 34 genes selected for their robust responses in TPS neurons were analyzed 3 days following a T2 spinal lesion. Our results show that after axonal injury nearer their cell bodies, there was a differential response of the same set of genes evaluated previously in TPS neurons after proximal axotomy, and LDPT neurons after distal axotomy (T10 spinal transection). The genetic response was much less robust than for TPS neurons after proximal axotomy, included both increased and decreased expression of certain genes, and did not suggest either a major regenerative or apoptotic response within the population of genes examined.ConclusionsThe data collectively demonstrate that the location of axotomy in relation to the soma of a neuron has a major effect on its ability to mount a regenerative response. However, the data also suggest that there are endogenous differences in the LDPT and TPS neuronal populations that affect their response to axotomy. These phenotypic differences may indicate that different or multiple therapies may be needed following spinal cord injury to stimulate maximal regeneration of all PS axons.

Per-Oral Pyloromyotomy (POP) for Medically Refractory Post-Surgical Gastroparesis

BackgroundPost-surgical gastroparesis (psGP) is putatively related to vagal denervation from either therapeutic transection or inadvertent injury. Here, we present a series of patients undergoing endoscopic per-oral pyloromyotomy (POP) as a treatment for medically refractory psGP. MethodsPatients identified from a prospectively maintained database of patients undergoing POP procedures at our institution from January 2016 to January 2018 were included. Surgical history, symptom scores, and gastric emptying studies before and 3 months after POP were additionally recorded. ResultsDuring the study period, 177 POP procedures were performed, of which 38 (21.5%) were for psGP. The study cohort was 84.2% female with a mean body mass index of 27.6 kg/m2 and mean age of 55.2 years. Common comorbidities included hypertension (34.2%), depression (31.6%), and gastroesophageal reflux disease (28.9%). Hiatal/paraesophageal hernia repair (39.5%) or fundoplication (36.8%) preceded psGP diagnosis most often. The mean operative time was 30 ± 20 min. There were no intraoperative complications. Mean postoperative length of stay was 1.2 days. There were two readmissions within 30 days, one for melena and one for dehydration. The mean improvement in total Gastroparesis Symptom Index Score was 1.29 (p = 0.0002). The mean 4-h gastric retention improved from a pre-POP mean of 46.4 to 17.9% post-POP. Normal gastric emptying was noted in 50% of subjects with available follow-up imaging. ConclusionPOP is a safe and effective endoscopic therapy for patients with psGP. POP should be considered a reasonable first-line option for patients with medically refractory psGP and may allow stomach preservation.

Disruption of RAB-5 Increases EFF-1 Fusogen Availability at the Cell Surface and Promotes the Regenerative Axonal Fusion Capacity of the Neuron.

Following a transection injury to the axon, neurons from a number of species have the ability to undergo spontaneous repair via fusion of the two separated axonal fragments. In the nematode Caenorhabditis elegans, this highly efficient regenerative axonal fusion is mediated by epithelial fusion failure-1 (EFF-1), a fusogenic protein that functions at the membrane to merge the two axonal fragments. Identifying modulators of axonal fusion and EFF-1 is an important step toward a better understanding of this repair process. Here, we present evidence that the small GTPase RAB-5 acts to inhibit axonal fusion, a function achieved via endocytosis of EFF-1 within the injured neuron. Therefore, we find that perturbing RAB-5 activity is sufficient to restore axonal fusion in mutant animals with decreased axonal fusion capacity. This is accompanied by enhanced membranous localization of EFF-1 and the production of extracellular EFF-1-containing vesicles. These findings identify RAB-5 as a novel regulator of axonal fusion in C. elegans hermaphrodites and the first regulator of EFF-1 in neurons.SIGNIFICANCE STATEMENT Peripheral and central nerve injuries cause life-long disabilities due to the fact that repair rarely leads to reinnervation of the target tissue. In the nematode Caenorhabditis elegans, axonal regeneration can proceed through axonal fusion, whereby a regrowing axon reconnects and fuses with its own separated distal fragment, restoring the original axonal tract. We have characterized axonal fusion and established that the fusogen epithelial fusion failure-1 (EFF-1) is a key element for fusing the two separated axonal fragments back together. Here, we show that the small GTPase RAB-5 is a key cell-intrinsic regulator of the fusogen EFF-1 and can in turn regulate axonal fusion. Our findings expand the possibility for this process to be controlled and exploited to facilitate axonal repair in medical applications.

RETRACTED: Macrophage-Derived Slit3 Controls Cell Migration and Axon Pathfinding in the Peripheral Nerve Bridge

SummarySlit-Robo signaling has been characterized as a repulsive signal for precise axon pathfinding and cell migration during embryonic development. Here, we describe a role for Sox2 in the regulation of Robo1 in Schwann cells and for Slit3-Robo1 signaling in controlling axon guidance within the newly formed nerve bridge following peripheral nerve transection injury. In particular, we show that macrophages form the outermost layer of the nerve bridge and secrete high levels of Slit3, while migratory Schwann cells and fibroblasts inside the nerve bridge express the Robo1 receptor. In line with this pattern of Slit3 and Robo1 expression, we observed multiple axon regeneration and cell migration defects in the nerve bridge of Sox2-, Slit3-, and Robo1-mutant mice. Our findings have revealed important functions for macrophages in the peripheral nervous system, utilizing Slit3-Robo1 signaling to control correct peripheral nerve bridge formation and precise axon targeting to the distal nerve stump following injury.

Laparoscopic end-to-end biliary reconstruction with T-tube for transected bile duct injury during laparoscopic cholecystectomy

PurposeThis report describes the laparoscopic end-to-end biliary reconstruction with T-tube for transected bile duct injury (BDI) during laparoscopic cholecystectomy.MethodsWe performed a retrospective descriptive analysis for all patients with a transected BDI at a single institution. We collected and analyzed data for injury site and type, reconstruction methods, conversion rate, previous intervention, and outcomes.ResultsBetween January 2014 and December 2017, 2,901 patients underwent laparoscopic cholecystectomy at a single institution. Among them, 8 patients experienced a transected BDI during laparoscopic cholecystectomy, so the surgeon performed laparoscopic end-to-end biliary reconstruction with T-tube. Our patient series consisted of 6 women (75%) and 2 men (25%) with a mean age of 48.3 years (median, 49 years; range, 29–77 years). Two cases were converted to open surgery. The most common injured site was the common bile duct (5 of 8, 62.5%). The most common injury type, using Bismuth's classification system, was type I (3 of 8, 37.5%). The mean operating time was 136.8 minutes (median, 135.0 minutes; range, 0–180.0 minutes). The mean hospital stay was 7.0 days (median, 4.5 days, range: 3.0–21.0 days). The mean follow-up was 36.4 months (median, 34.0 months; range, 16.0–63.0 months). We observed one postoperative complication during the follow-up period. The patient had an anastomosis site leakage and was cured after reoperation.ConclusionLaparoscopic end-to-end biliary reconstruction with T-tube for transected BDI during laparoscopic cholecystectomy seems to be safe and feasible in selected patients. However, long-term follow-up to identify complications from bile duct stricture remains important.

Immunohistochemical localization of nerve injury-induced protein-1 in mouse tissues.

Nerve injury-induced protein (Ninjurin)-1 is a cell adhesion molecule that is upregulated in neurons and Schwann cells after transection injury in rats. In this study, we investigated the localization of Ninjurin-1 in various tissues, including the cerebrum, sciatic nerve, spleen, lung, stomach, ileum, colon, liver, pancreas, kidney, testis, and skin in C57BL/6 mice, using Western blotting and immunohistochemistry. Western blot analysis showed that Ninjurin-1 was differentially expressed among organs. Ninjurin-1 was abundant in skin and ileum, weakly expressed in cerebrum, and moderately expressed in the other organs studied. Immunohistochemical analysis largely confirmed the results of the western blot analysis with often localization of Ninjurin-1 in the regions with abundant connective tissues. In addition, Ninjurin-1 was differentially expressed in various cell types in the tissues under the investigation. These findings suggest that Ninjurin-1 may play organ-specific roles in development and homeostasis of many organs.

Etomidate affects the anti-oxidant pathway to protect retinal ganglion cells after optic nerve transection.

Our previous studies revealed that etomidate, a non-barbiturate intravenous anesthetic agent, has protective effects on retinal ganglion cells within 7 days after optic nerve transection. Whether this process is related to anti-oxidative stress is not clear. To reveal its mechanism, we established the optic nerve transection injury model by transecting 1 mm behind the left eyeball of adult male Sprague-Dawley rats. The rats received an intraperitoneal injection of etomidate (4 mg/kg) once per day for 7 days. The results showed that etomidate significantly enhanced the number of retinal ganglion cells retrogradely labeled with Fluorogold at 7 days after optic nerve transection. Etomidate also significantly reduced the levels of nitric oxide and malonaldehyde in the retina and increased the level of glutathione at 12 hours after optic nerve transection. Thus, etomidate can protect retinal ganglion cells after optic nerve transection in adult rats by activating an anti-oxidative stress response. The study was approved by the Animal Ethics Committee at Air Force Medical University, China (approval No. 20180305) on March 5, 2018.

Managing the nerve gap: New tools in the peripheral nerve repair toolbox

End-to-end repair of a peripheral nerve transection injury remains the gold standard. Delayed repair, nerve debridement and early functional mobilisation may all increase repair site tension, which impedes axon regeneration and must be avoided. Prompt diagnosis, referral to a specialist and exploration can minimise the nerve retraction, debridement and gap size, and societal benefit will be achieved through adopting a standardised approach to management. However, early exploration may provide challenges in defining the extent of the injury zone and therefore the adequacy of nerve debridement. Repair site tension can be reduced with 'sutureless' nerve approximation in a conduit, interposition of autologous graft or with interposed processed nerve allograft. Sutures can be avoided through interposition de-tensioning grafts and use of tissue glues. However, a large gap in a conduit will not support robust regeneration and grafts have two neurorrhaphy sites for axons to negotiate. Autologous graft has a donor site morbidity that may be unacceptable. An algorithm for peripheral nerve reconstruction should include the use of conduits and allograft as de-tensioning devices, avoiding the morbidity associated with autologous nerve grafting.

Diffusion tensor tractography to visualize axonal outgrowth and regeneration in a 4-cm reverse autograft sciatic nerve rabbit injury model

ABSTRACTBackground: Diffusion tensor tractography (DTT) has recently been shown to accurately detect nerve injury and regeneration. This study assesses whether 7-tesla (7T) DTT imaging is a viable modality to observe axonal outgrowth in a 4 cm rabbit sciatic nerve injury model fixed by a reverse autograft (RA) surgical technique.Methods: Transection injury of unilateral sciatic nerve (4 cm long) was performed in 25 rabbits and repaired using a RA surgical technique. Analysis of the nerve autograft was performed at 3, 6, and 11 weeks postoperatively and compared to normal contralateral sciatic nerve, used as control group. High-resolution DTT from ex vivo sciatic nerves were obtained using 3D diffusion-weighted spin-echo acquisitions at 7-T. Total axons and motor and sensory axons were counted at defined lengths along the graft.Results: At 11 weeks, histologically, the total axon count of the RA group was equivalent to the contralateral uninjured nerve control group. Similarly, by qualitative DTT visualization, the 11-week RA group showed increased fiber tracts compared to the 3 and 6 weeks counterparts. Upon immunohistochemical evaluation, 11-week motor axon counts did not significantly differ between RA and control; but significantly decreased sensory axon counts remained. Nerves explanted at 3 weeks and 6 weeks showed decreased motor and sensory axon counts.Discussion: 7-T DTT is an effective imaging modality that may be used qualitatively to visualize axonal outgrowth and regeneration. This has implications for the development of technology that non-invasively monitors peripheral nerve regeneration in a variety of clinical settings.