Converging synaptic and network dysfunctions in distinct autoimmune encephalitis.

Psychiatric and neurological symptoms, as well as cognitive deficits, represent a prominent phenotype associated with variable forms of autoimmune encephalitis, regardless of the neurotransmitter receptor targeted by autoantibodies. The mechanistic underpinnings of these shared major neuropsychiatric symptoms remain however unclear. Here, we investigate the impacts of patient-derived monoclonal autoantibodies against the glutamatergic NMDAR (NMDAR mAb) and inhibitory GABAaR (GABAaR mAb) signalling in the hippocampal network. Unexpectedly, both excitatory and inhibitory synaptic receptor membrane dynamics, content and transmissions are altered by NMDAR or GABAaR mAb, irrespective of the affinity or antagonistic effect of the autoantibodies. The effect of NMDAR mAb on inhibitory synapses and GABAaR mAb on excitatory synapses requires neuronal activity and involves protein kinase signalling. At the cell level, both autoantibodies increase the excitation/inhibition balance of principal cell inputs. Furthermore, NMDAR or GABAaR mAb leads to hyperactivation of hippocampal networks through distinct alterations of principal cell and interneuron properties. Thus, autoantibodies targeting excitatory NMDAR or inhibitory GABAaR trigger convergent network dysfunctions through a combination of shared and distinct mechanisms.

An In Vivo Model of Human Macrophages in Metastatic Melanoma.

Despite recent therapeutic progress, advanced melanoma remains lethal for many patients. The composition of the immune tumor microenvironment (TME) has decisive impacts on therapy response and disease outcome, and high-dimensional analyses of patient samples reveal the heterogeneity of the immune TME. Macrophages infiltrate TMEs and generally associate with tumor progression, but the underlying mechanisms are incompletely understood. Because experimental systems are needed to elucidate the functional properties of these cells, we developed a humanized mouse model reconstituted with human immune cells and human melanoma. We used two strains of recipient mice, supporting or not supporting the development of human myeloid cells. We found that human myeloid cells favored metastatic spread of the primary tumor, thereby recapitulating the cancer-supportive role of macrophages. We next analyzed the transcriptome of human immune cells infiltrating tumors versus other tissues. This analysis identified a cluster of myeloid cells present in the TME, but not in other tissues, which do not correspond to canonical M2 cells. The transcriptome of these cells is characterized by high expression of glycolytic enzymes and multiple chemokines and by low expression of gene sets associated with inflammation and adaptive immunity. Compared with humanized mouse results, we found transcriptionally similar myeloid cells in patient-derived samples of melanoma and other cancer types. The humanized mouse model described here thus complements patient sample analyses, enabling further elucidation of fundamental principles in melanoma biology beyond M1/M2 macrophage polarization. The model can also support the development and evaluation of candidate antitumor therapies.

Limited Nerve Regeneration across Acellular Nerve Allografts (ANAs) Coincides with Changes in Blood Vessel Morphology and the Development of a Pro-Inflammatory Microenvironment.

The use of acellular nerve allografts (ANAs) to reconstruct long nerve gaps (>3 cm) is associated with limited axon regeneration. To understand why ANA length might limit regeneration, we focused on identifying differences in the regenerative and vascular microenvironment that develop within ANAs based on their length. A rat sciatic nerve gap model was repaired with either short (2 cm) or long (4 cm) ANAs, and histomorphometry was used to measure myelinated axon regeneration and blood vessel morphology at various timepoints (2-, 4- and 8-weeks). Both groups demonstrated robust axonal regeneration within the proximal graft region, which continued across the mid-distal graft of short ANAs as time progressed. By 8 weeks, long ANAs had limited regeneration across the ANA and into the distal nerve (98 vs. 7583 axons in short ANAs). Interestingly, blood vessels within the mid-distal graft of long ANAs underwent morphological changes characteristic of an inflammatory pathology by 8 weeks post surgery. Gene expression analysis revealed an increased expression of pro-inflammatory cytokines within the mid-distal graft region of long vs. short ANAs, which coincided with pathological changes in blood vessels. Our data show evidence of limited axonal regeneration and the development of a pro-inflammatory environment within long ANAs.

Peripheral Nerve Injury After Deoxycholic Acid (ATX-101) Injection in an Experimental Rat Model.

BACKGROUND: Deoxycholic acid (ATX-101) is a drug administered by subcutaneous injection for local fat reduction. However, ATX-101 treatment has been reported to cause marginal mandibular nerve injury with noticeable functional deficits when targeting submental fat. As a cytolytic agent with some selectivity for adipocytes, ATX-101 may damage the lipid-rich myelin surrounding peripheral nerves. OBJECTIVES: This study seeks to characterize the nerve injection injury from ATX-101 in an experimental rat model. METHODS: Using a rat sciatic nerve injection model, intrafascicular and extrafascicular injections of deoxycholic acid (ATX-101) were compared to lidocaine (positive control) and saline (negative control). Nerves were harvested at a 2-week endpoint for histomorphometric analysis. RESULTS: Cross-sectional area of nerve injury was significantly increased by ATX-101 injection at 75±15% with intrafascicular ATX-101 (p<0.001), 41±21% with extrafascicular ATX-101 (p<0.01), and 38±20% with positive control lidocaine (p<0.01) compared to 7±13% with negative control saline. Demyelinating injury was a significant mechanism of injury in the affected nerve fibers compared to uninjured nerve fibers (p<0.04), but there was no difference in axon-to-myelin area ratio between the lidocaine and ATX-101 cohorts. After two weeks, Wallerian degeneration was evident with only small regenerating nerve fibers present in the ATX-101-injured groups compared to saline (2.54±0.26um vs 5.03±0.44um, p<0.001) in average width. CONCLUSIONS: Deoxycholic acid (ATX-101) is capable of extensive nerve injury in rats. The mechanism of action for ATX-101 does not preferentially target myelin more than other common neurotoxic agents. Appropriate knowledge of surgical anatomy and injection technique is necessary for any practitioners providing ATX-101 injections.

Electrical stimulation or tacrolimus (FK506) alone enhances nerve regeneration and recovery after nerve surgery, while dual use reduces variance and combines strengths of each in promoting enhanced outcomes.

INTRODUCTION/AIMS: Repaired nerve injuries can fail to achieve functional recovery. Therapeutic options beyond surgery, such as systemic tacrolimus (FK506) and electrical stimulation (E-stim), can improve recovery. We tested whether dual administration of FK506 and E-stim enhances regeneration and recovery more than either therapeutic alone. METHODS: Rats were randomized to four groups: E-stim, FK506, FK506 + E-stim, and repair alone. All groups underwent tibial nerve transection and repair. Two sets of animals were created to measure outcomes of early nerve regeneration using nerve histology (n = 36) and functional recovery (n = 42) (21- and 42-day endpoints, respectively). Functional recovery was measured by behavioral analyses (walking track and grid walk) and, at the endpoint, muscle mass and force. RESULTS: Dual E-stim and FK506 administration produced histomorphometric measurements of nerve regeneration no different than either therapeutic alone. All treatments were superior to repair alone (FK506, P < .0001; E-stim, P < .05; FK506 + E-stim, P < .05). The E-stim and FK506 + E-stim groups had improved behavioral recovery compared with repair alone (at 6 weeks: E-stim, P < .05; FK506 + E-stim, P < .01). The FK506 group had improved recovery based on walking-track analysis (at 6 weeks: P < .001) and muscle force and mass (P < .05). The concurrent use of both therapies ensured earlier functional recovery and decreased variability in functional outcomes compared with either therapy alone, suggesting a moderate benefit. DISCUSSION: Dual administration of FK506 and E-stim showed minimal additive effects to further improve regeneration or recovery compared with either therapy alone. The data suggest the combination of FK506 and E-stim appears to combine the relative strengths of each therapeutic.

Near-Infrared Carbon Nanotube Tracking Reveals the Nanoscale Extracellular Space around Synapses.

We provide evidence of a local synaptic nanoenvironment in the brain extracellular space (ECS) lying within 500 nm of postsynaptic densities. To reveal this brain compartment, we developed a correlative imaging approach dedicated to thick brain tissue based on single-particle tracking of individual fluorescent single wall carbon nanotubes (SWCNTs) in living samples and on speckle-based HiLo microscopy of synaptic labels. We show that the extracellular space around synapses bears specific properties in terms of morphology at the nanoscale and inner diffusivity. We finally show that the ECS juxta-synaptic region changes its diffusion parameters in response to neuronal activity, indicating that this nanoenvironment might play a role in the regulation of brain activity.

Assessing the Impact of Secondary Fluorescence on X-Ray Microanalysis Results from Semiconductor Thin Films.

The impact of secondary fluorescence on the material compositions measured by X-ray analysis for layered semiconductor thin films is assessed using simulations performed by the DTSA-II and CalcZAF software tools. Three technologically important examples are investigated: AlxGa1−xN layers on either GaN or AlN substrates, InxAl1−xN on GaN, and Si-doped (SnxGa1−x)2O3 on Si. Trends in the differences caused by secondary fluorescence are explained in terms of the propensity of different elements to reabsorb either characteristic or bremsstrahlung X-rays and then to re-emit the characteristic X-rays used to determine composition of the layer under investigation. Under typical beam conditions (7­12 keV), the quantification of dopants/trace elements is found to be susceptible to secondary fluorescence and care must be taken to prevent erroneous results. The overall impact on major constituents is shown to be very small with a change of approximately 0.07 molar cation percent for Al0.3Ga0.7N/AlN layers and a maximum change of 0.08 at% in the Si content of (SnxGa1−x)2O3/Si layers. This provides confidence that previously reported wavelength-dispersive X-ray compositions are not compromised by secondary fluorescence.

Controlling axonal regeneration with acellular nerve allograft limits neuroma formation in peripheral nerve transection: An experimental study in a swine model.

BACKGROUND: Symptomatic neuromata are a common indication for revision surgery following amputation. Previously described treatments, including traction neurectomy, nerve transposition, targeted muscle re-innervation, and nerve capping, have provided inconsistent results or are technically challenging. Prior research using acellular nerve allografts (ANA) has shown controlled termination of axonal regrowth in long grafts. The purpose of this study was to determine the ability of a long ANA to prevent neuroma formation following transection of a peripheral nerve in a swine model. MATERIALS AND METHODS: Twenty-two adult female Yucatan miniature swine (Sus scrofa; 4-6 months, 15-25 kg) were assigned to control (ulnar nerve transection only, n = 10), treatment (ulnar transection and coaptation of 50 mm ANA, n = 10), or donor (n = 2) groups. Nerves harvested from donor group animals were treated to create the ANA. After 20 weeks, the transected nerves including any neuroma or graft were harvested. Both qualitative (nerve architecture, axonal sprouting) and quantitative histologic analyses (myelinated axon number, cross sectional area of nerve tissue) were performed. RESULTS: Qualitative histologic analysis of control specimens revealed robust axon growth into dense scar tissue. In contrast, the treatment group revealed dwindling axons in the terminal tissue, consistent with attenuated neuroma formation. Quantitative analysis revealed a significantly decreased number of myelinated axons in the treatment group (1232 ± 540) compared to the control group (44,380 ± 7204) (p < .0001). Cross sectional area of nerve tissue was significantly smaller in treatment group (2.83 ± 1.53 mm2 ) compared to the control group (9.14 ± 1.19 mm2 ) (p = .0012). CONCLUSIONS: Aberrant axonal growth is controlled to termination with coaptation of a 50 mm ANA in a swine model of nerve injury. These early results suggest further investigation of this technique to prevent and/or treat neuroma formation.

Effect of Veau Class on Levator Veli Palatini Muscle Composition.

OBJECTIVE: To examine levator veli palatini muscle composition in patients with nonsyndromic cleft palate and investigate the impact of Veau class. DESIGN: Prospective cohort study. SETTING: Tertiary care academic hospital. PATIENTS/PARTICIPANTS: Thirteen patients with nonsyndromic cleft palate were recruited. INTERVENTIONS: During primary palatoplasty, a sample of levator veli palatini muscle was excised and prepared for histological analysis. MAIN OUTCOME MEASURES: Fat and collagen content were determined utilizing Oil Red and Sirius red stains, respectively, while muscle fiber cross-sectional areas were calculated from H&E-stained samples, with analysis using histomorphometric methods. Immunofluorescent staining of myosin heavy chain isoforms was performed. RESULTS: Patients underwent repair at 10.8 months of age (interquartile range [IQR] 10.2-12.9). Fat content of the levator veli palatini muscle was low in both groups, ranging from 0% to 5.2%. Collagen content ranged from 8.5% to 39.8%; neither fat nor collagen content showed an association with Veau classes. Mean muscle fiber cross-sectional area decreased with increasing Veau class, from 808 µm2 (range 692-995 µm2) in Veau II to 651 µm2 (range 232-750 µm2) in Veau III (P = .02). There was also a nonsignificant decrease in proportion of type I muscle fibers with increasing Veau class (44.3% [range 31.4%-84.4%] in Veau II vs 35.3% [range 17.4%-61.3%] in Veau III). CONCLUSIONS: Muscle fiber area in levator veli palatini muscles decreases in Veau III clefts in comparison to Veau II. The impact of these differences in velopharyngeal dysfunction requires further analysis of a larger cohort.

Autoimmunity and NMDA receptor in brain disorders: Where do we stand?

Over the past decades, the identification of autoimmune encephalitis in which patients express autoantibodies directed against neurotransmitter receptors has generated great hope to shed new light on the molecular mechanisms underpinning neurological and psychiatric conditions. Among these autoimmune encephalitides, the discovery of autoantibodies directed against the glutamatergic NMDA receptor (NMDAR-Ab), in the anti-NMDAR encephalitis, has provided some key information on how complex neuropsychiatric symptoms can be caused by a deficit in NMDAR signalling. Yet, NMDAR-Abs have also been detected in several neurological and psychiatric conditions, as well as in healthy individuals. In addition, these various NMDAR-Abs appear to have different molecular properties and pathogenicities onto receptors and synaptic functions. Here, we discuss the current view on the variety of NMDAR-Abs and, in particular, how these autoantibodies can lead to receptor dysfunction in neuronal networks. Since our mechanistic understanding on patients' NMDAR-Abs is still in its infancy, several complementary processes can be proposed and further in-depth molecular and cellular investigations will surely reveal key insights. Autoantibodies represent a great opportunity to gain knowledge on the etiology of neuropsychiatric disorders and pave the way for innovative therapeutic strategies. ONE SENTENCE SUMMARY: Current view on patients' autoantibody against NMDAR.

Quantification of Trace-Level Silicon Doping in Al x Ga1-xN Films Using Wavelength-Dispersive X-Ray Microanalysis.

Wavelength-dispersive X-ray (WDX) spectroscopy was used to measure silicon atom concentrations in the range 35-100 ppm [corresponding to (3-9) × 1018 cm-3] in doped AlxGa1-xN films using an electron probe microanalyser also equipped with a cathodoluminescence (CL) spectrometer. Doping with Si is the usual way to produce the n-type conducting layers that are critical in GaN- and AlxGa1-xN-based devices such as LEDs and laser diodes. Previously, we have shown excellent agreement for Mg dopant concentrations in p-GaN measured by WDX with values from the more widely used technique of secondary ion mass spectrometry (SIMS). However, a discrepancy between these methods has been reported when quantifying the n-type dopant, silicon. We identify the cause of discrepancy as inherent sample contamination and propose a way to correct this using a calibration relation. This new approach, using a method combining data derived from SIMS measurements on both GaN and AlxGa1-xN samples, provides the means to measure the Si content in these samples with account taken of variations in the ZAF corrections. This method presents a cost-effective and time-saving way to measure the Si doping and can also benefit from simultaneously measuring other signals, such as CL and electron channeling contrast imaging.

Evaluation for Late Nerve Transfer Surgery in Spinal Cord Injury: Predicting the Degree of Lower Motor Neuron Injury.

PURPOSE: Nerve transfer surgery is used to restore upper extremity function following cervical spinal cord injury (SCI) with substantial variation in outcomes. The injury pattern in SCI is complex and can include isolated upper motor neuron (UMN) and combined UMN/lower motor neuron (LMN) dysfunction. The purpose of the study was to determine the most effective diagnostic technique for determining suitable candidates for nerve transfer surgery in SCI. METHODS: Medical records were reviewed of patients who had nerve transfers to restore upper extremity function in SCI. Data collected included (1) preoperative clinical examination and electrodiagnostic testing; (2) intraoperative neuromuscular stimulation (NMS); and (3) nerve histopathology. Preoperative, intraoperative, and postoperative data were compared to identify predictors of isolated UMN versus combined UMN/LMN injury patterns. RESULTS: The study sample included 22 patients with 50 nerve transfer surgeries and included patients ranging from less than 1 year to over a decade post-SCI. Normal recipient nerve conduction studies (NCS) before surgery corresponded to the intraoperative presence of recipient NMS and postoperative histopathology that showed normal nerve architecture. Conversely, abnormal recipient NCS before surgery corresponded with the absence of recipient NMS during surgery and patterns of denervation on postoperative histopathology. Normal donor preoperative manual muscle testing corresponded with the presence of donor NMS during surgery and normal nerve architecture on postoperative histopathology. An EMG of corresponding musculature did not correspond with intraoperative donor or recipient NMS or histopathological findings. CONCLUSIONS: NCS better predict patterns of injury in SCI than EMG. This is important information for clinicians evaluating people for late nerve transfer surgery even years post-SCI. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic II.

Short-term evaluation of hepatic toxicity of titanium dioxide nanofiber (TDNF).

Various in vitro and in vivo studies have shown titanium dioxide nanoparticles (TDNPs) increase the production of reactive oxygen species and change the expression of genes and proteins involved in the inflammatory response and cell division. Although, the cytotoxicity of TDNPs has been shown to be largely dependent on the characteristics of the particles including shape and surface area. This present study investigates the effects of titanium dioxide nanofibers (TDNFs) with a diameter of 300-800 nm, on the histopathology of liver tissue, changes in feed efficiency and liver weights, changes in hepatic gene expression, and serum biochemical parameters in male Sprague-Dawley rats. Male Sprague-Dawley rats were fed concentrations of 0 ppm, 40 ppm, and 60 ppm TDNF by oral gavage for two weeks. Selected inflammatory response, oxidative stress, and regulatory cell cycle genes were measured by quantitative real-time polymerase chain reaction (qRT-PCR). Differences in gene expression compared to the 0 ppm group were observed in genes Gnat3, IghA, IL-1ß, p21, p53, and TNF-α. Histopathology, body and liver weights, and feed efficiency showed no significant differences. Albumin levels in all groups were not significantly higher than the reference range while ALT levels for all groups were high compared to the reference value. Currently, the results suggest TDNF does not exhibit significant hepatic toxicity. This may be explained by the rutile crystalline structure of the nanofibers, the lower concentration or the short duration of exposure toxic used during experimentation.

Nerve stepping stone has minimal impact in aiding regeneration across long acellular nerve allografts.

INTRODUCTION: Acellular nerve allografts (ANAs) yield less consistent favorable outcomes compared with autografts for long gap reconstructions. We evaluated whether a hybrid ANA can improve 6-cm gap reconstruction. METHODS: Rat sciatic nerve was transected and repaired with either 6-cm hybrid or control ANAs. Hybrid ANAs were generated using a 1-cm cellular isograft between 2.5-cm ANAs, whereas control ANAs had no isograft. Outcomes were assessed by graft gene and marker expression (n = 4; at 4 weeks) and motor recovery and nerve histology (n = 10; at 20 weeks). RESULTS: Hybrid ANAs modified graft gene and marker expression and promoted modest axon regeneration across the 6-cm defect compared with control ANA (P < 0.05), but yielded no muscle recovery. Control ANAs had no appreciable axon regeneration across the 6-cm defect. DISCUSSION: A hybrid ANA confers minimal motor recovery benefits for regeneration across long gaps. Clinically, the authors will continue to reconstruct long nerve gaps with autografts. Muscle Nerve 57: 260-267, 2018.

Transgenic SCs expressing GDNF-IRES-DsRed impair nerve regeneration within acellular nerve allografts.

Providing temporally regulated glial cell line-derived neurotrophic factor (GDNF) to injured nerve can promote robust axon regeneration. However, it is poorly understood why providing highly elevated levels of GDNF to nerve can lead to axon entrapment in the zone containing elevated GDNF. This limited understanding represents an obstacle to the translation of GDNF therapies to treat nerve injuries clinically. Here, we investigated how transgenic Schwann cells (SCs) overexpressing GDNF-IRES-DsRed impact nerve regeneration. Cultured primary SCs were transduced with lentiviruses (GDNF-overexpressing transgenic SCs), one of which provides the capability to express high levels of GDNF and regulate temporal GDNF expression. These SC groups were transplanted into acellular nerve allografts (ANAs) bridging a 14 mm rat sciatic nerve defect. GDNF-overexpressing transgenic SCs expressing GDNF for as little as 1 week decreased axon regeneration across ANAs and caused extensive extracellular matrix (ECM) remodeling. To determine whether additional gene expression changes beyond GDNF transgene expression occurred in GDNF-overexpressing transgenic SCs, microarray analysis of GDNF-overexpressing transgenic SCs compared to untreated SCs was performed. Microarray analysis revealed a set of common genes regulated in transgenic SC groups expressing high levels of GDNF compared to untreated SCs. A co-culture model of GDNF-overexpressing transgenic SCs with fibroblasts (FBs) revealed differential FB ECM-related gene expression compared to untreated SCs. These data suggest a component of axon entrapment is independent of GDNF's impact on axons. Biotechnol. Bioeng. 2017;114: 2121-2130. © 2017 Wiley Periodicals, Inc.

Assessment of the short-term toxicity of TiO2 nanofiber in Sprague Dawley rats.

Synthetic nanomaterials have many unique chemical and physical properties, mainly due to their high specific surface area and quantum confinement effect. Specifically, titanium dioxide (TiO2 ) nanomaterial has high stability, anticorrosive, and photocatalytic properties. However, there are concerns over adverse biological effects resulting from bioeffects. This study was to investigate adverse effects associated with acute ingestion of TiO2 nanofiber (TDNF). TDNF was fabricated via electrospinning method, followed by dissolution in water. Six- to seven-week-old male Sprague Dawley rats were exposed to a total of 0, 40, and 60 ppm of TDNF for 2 weeks via oral gavage. Serum total protein and weight gain during the course of this study displayed marginal concentration-dependent alterations. These findings were followed by a global gene expression analysis to identify which transcripts might be responsive to TNDF toxicity. Differentially expressed mRNA levels were dose-dependently higher in animals exposed to TNDF. The majority of the affected genes were biochemically involved in immune response and inflammation. We believe this is due to the fact that TNDF is unable to penetrate the cell and forms phagocytosis sites that trigger inflammatory and immune response. All results taken together, short-term ingestion of TNDF produced marginal effects indicative of inflammation. Finally, the broad gene expression data were validated through quantification of immunoglobulin heavy chain alpha (Igha). Igha gene was upregulated in treated groups, showing similar expression patterns to the global gene expression data.

Mechanism-based combination treatment dramatically increases therapeutic efficacy in murine globoid cell leukodystrophy.

Globoid cell leukodystrophy (GLD, Krabbe disease) is a lysosomal storage disease (LSD) caused by a deficiency in galactocerebrosidase (GALC) activity. In the absence of GALC activity, the cytotoxic lipid, galactosylsphingosine (psychosine), accumulates in the CNS and peripheral nervous system. Oligodendrocytes and Schwann cells are particularly sensitive to psychosine, thus leading to a demyelinating phenotype. Although hematopoietic stem-cell transplantation provides modest benefit in both presymptomatic children and the murine model (Twitcher), there is no cure for GLD. In addition, GLD has been relatively refractory to virtually every experimental therapy attempted. Here, Twitcher mice were simultaneously treated with CNS-directed gene therapy, substrate reduction therapy, and bone marrow transplantation to target the primary pathogenic mechanism (GALC deficiency) and two secondary consequences of GALC deficiency (psychosine accumulation and neuroinflammation). Simultaneously treating multiple pathogenic targets resulted in an unprecedented increase in life span with improved motor function, persistent GALC expression, nearly normal psychosine levels, and decreased neuroinflammation. Treating the primary pathogenic mechanism and secondary targets will likely improve therapeutic efficacy for other LSDs with complex pathological and clinical presentations.

Vascularization is delayed in long nerve constructs compared with nerve grafts.

INTRODUCTION: Nerve regeneration across nerve constructs, such as acellular nerve allografts (ANAs), is inferior to nerve auto/isografts especially in the case of long defect lengths. Vascularization may contribute to poor regeneration. The time course of vascular perfusion within long grafts and constructs was tracked to determine vascularization. METHODS: Male Lewis rat sciatic nerves were transected and repaired with 6 cm isografts or ANAs. At variable days following grafting, animals were perfused with Evans Blue albumin, and grafts were evaluated for vascular perfusion by a blinded observer. RESULTS: Vascularization at mid-graft was re-established within 3-4 days in 6 cm isografts, while it was established after 10 days in 6 cm ANAs. CONCLUSIONS: Vascular perfusion is reestablished over a shorter time course in long isografts when compared with long ANAs. The differences in vascularization of long ANAs compared with auto/isografts suggest regenerative outcomes across ANAs could be affected by vascularization rates. Muscle Nerve 54: 319-321, 2016.

The Effect of Short Nerve Grafts in Series on Axonal Regeneration Across Isografts or Acellular Nerve Allografts.

PURPOSE: To evaluate the regenerative effect of the additional suture line when using either isografts (ISOs) or acellular nerve allografts (ANAs) placed end-to-end to span a short gap in a rat model. METHODS: Rat sciatic nerves were transected and repaired with 2-cm nerve grafts (ISO or ANA). The grafts were 2 cm in length or a 1-cm segment was connected end-to-end to a 1-cm segment to yield a 2-cm length. At 8 weeks, extensor digitorum longus (EDL) muscle force and mass were measured. Nerves were harvested for histomorphometry. In a separate parallel study, the nerves were harvested 2 weeks following graft implantation to assess gene expression changes. RESULTS: All grafts demonstrated regeneration across the 2-cm segment(s). The additional suture line did not result in statistical differences in the number of myelinated nerve fibers that reached the distal nerve. However, when the graft types were compared, there was a significant decrease in nerve fibers in the ANA groups. The EDL muscle mass was significantly greater by using nerve ISOs compared with ANAs, regardless of an additional suture line, but there were no statistical differences noted in EDL muscle force. Gene expression analysis did not differ owing to an additional suture line. CONCLUSIONS: Minimal axonal loss and no functional deficits were identified with an additional suture line in this rodent short nerve gap model. CLINICAL RELEVANCE: Placing nerve grafts in series is a viable option for treating short nerve gaps; however, the use of autografts remains preferable over the use of ANAs.

Long-term functional recovery after facial nerve transection and repair in the rat.

BACKGROUND: The rodent model is commonly used to study facial nerve injury. Because of the exceptional regenerative capacity of the rodent facial nerve, it is essential to consider the timing when studying facial nerve regeneration and functional recovery. Short-term functional recovery data following transection and repair of the facial nerve has been documented by our laboratory. However, because of the limitations of the head fixation device, there is a lack of long-term data following facial nerve injury. The objective of this study was to elucidate the long-term time course and functional deficit following facial nerve transection and repair in a rodent model. METHODS: Adult rats were divided into group 1 (controls) and group 2 (experimental). Group 1 animals underwent head fixation, followed by a facial nerve injury, and functional testing was performed from day 7 to day 70. Group 2 animals underwent facial nerve injury, followed by delayed head fixation, and then underwent functional testing from months 6 to 8. RESULTS: There was no statistical difference between the average whisking amplitudes in group 1 and group 2 animals. CONCLUSION: Functional whisking recovery 6 months after facial nerve injury is comparable to recovery within 1 to 4 months of transection and repair, thus the ideal window for evaluating facial nerve recovery falls within the 4 months after injury.