ABSTRACT
Gpr126/Adgrg6 is an adhesion G protein‐coupled receptor essential for Schwann cell (SC) myelination with important contributions to repair after nerve crush injury. Despite critical ...functions in myelinating SCs, the role of Gpr126 within nonmyelinating terminal Schwann cells (tSCs) at the neuromuscular junction (NMJ), is not known. tSCs have important functions in synaptic maintenance and reinnervation, and after injury tSCs extend cytoplasmic processes to guide regenerating axons to the denervated NMJ. In this study, we show that Gpr126 is expressed in tSCs, and that absence of Gpr126 in SCs (SC‐specific Gpr126 knockout, cGpr126) results in a NMJ maintenance defect in the hindlimbs of aged mice, but not in young adult mice. After nerve transection and repair, cGpr126 mice display delayed NMJ reinnervation, altered tSC morphology with decreased S100β expression, and reduced tSC cytoplasmic process extensions. The immune response promoting reinnervation at the NMJ following nerve injury is also altered with decreased macrophage infiltration, Tnfα, and anomalous cytokine expression compared to NMJs of control mice. In addition, Vegfa expression is decreased in muscle, suggesting that cGpr126 non‐cell autonomously modulates angiogenesis after nerve injury. In sum, cGpr126 mice demonstrated delayed NMJ reinnervation and decreased muscle mass following nerve transection and repair compared to control littermates. The integral function of Gpr126 in tSCs at the NMJ provides the framework for new therapeutic targets for neuromuscular disease.
Gpr126 is expressed in terminal Schwann cells.
Terminal Schwann cell cytoplasmic processes are reduced in Schwann cell‐specific Gpr126 knockout mice after injury.
Gpr126 is integral to terminal Schwann cell response to and NMJ recovery after nerve injury.
Introduction
In this study we present a reproducible technique to assess motor recovery after nerve injury via neuromuscular junction (NMJ) immunostaining and electrodiagnostic testing.
Methods
...Wild‐type mice underwent sciatic nerve transection with repair. Hindlimb muscles were collected for microscopy up to 30 weeks after injury. Immunostaining was used to assess axons (NF200), Schwann cells (S100), and motor endplates (α‐bungarotoxin). Compound motor action potential (CMAP) amplitude was used to assess tibialis anterior (TA) function.
Results
One week after injury, nearly all (98.0%) endplates were denervated. At 8 weeks, endplates were either partially (28.3%) or fully (71.7%) reinnervated. At 16 weeks, NMJ reinnervation reached 87.3%. CMAP amplitude was 83% of naive mice at 16 weeks and correlated with percentage of fully reinnervated NMJs. Morphological differences were noted between injured and noninjured NMJs.
Discussion
We present a reproducible method for evaluating NMJ reinnervation. Electrodiagnostic data summarize NMJ recovery. Characterization of wild‐type reinnervation provides important data for consideration in experimental design and interpretation.
Functional recovery in the end target muscle is a determinant of outcome after peripheral nerve injury. The neuromuscular junction (NMJ) provides the interface between nerve and muscle and includes ...non-myelinating terminal Schwann cells (tSCs). After nerve injury, tSCs extend cytoplasmic processes between NMJs to guide axon growth and NMJ reinnervation. The mechanisms related to NMJ reinnervation are not known. We used multiple mouse models to investigate the mechanisms of NMJ reinnervation in both sexes, specifically whether macrophage-derived vascular endothelial growth factor-A (Vegf-A) is crucial to establishing NMJ reinnervation at the end target muscle. Both macrophage number and Vegf-A expression increased in end target muscles after nerve injury and repair. In mice with impaired recruitment of macrophages and monocytes (
-/- mice), the absence of CD68+ cells (macrophages) in the muscle resulted in diminished muscle function. Using a Vegf-receptor 2 (VegfR2) inhibitor (cabozantinib; CBZ) via oral gavage in wild-type (WT) mice resulted in reduced tSC cytoplasmic process extension and decreased NMJ reinnervation compared with saline controls. Mice with Vegf-A conditionally knocked out in macrophages (
mice) demonstrated a more prolonged detrimental effect on NMJ reinnervation and worse functional muscle recovery. Together, these results show that contributions of the immune system are integral for NMJ reinnervation and functional muscle recovery after nerve injury.
This work demonstrates beneficial contributions of a macrophage-mediated response for neuromuscular junction (NMJ) reinnervation following nerve injury and repair. Macrophage recruitment occurred at the NMJ, distant from the nerve injury site, to support functional recovery at the muscle. We have shown hindered terminal Schwann cell (tSC) injury response and NMJ recovery with inhibition of: (1) macrophage recruitment after injury; (2) vascular endothelial growth factor receptor 2 (VegfR2) signaling; and (3) Vegf secretion from macrophages. We conclude that macrophage-derived Vegf is a key component of NMJ recovery after injury. Determining the mechanisms active at the end target muscle after motor nerve injury reveals new therapeutic targets that may translate to improve motor recovery following nerve injury.
Background:
Surgical intervention with combined myectomy and neurectomy followed by functioning free muscle transplantation has been proposed to effectively resolve the problem of postparalytic ...facial synkinesis since 1985, and it continues to be the authors’ standard of care. The authors aim to provide evidence that this surgical strategy is effective for treatment of synkinesis and smile quality.
Methods:
One hundred three patients with postparalytic facial synkinesis were investigated (1985 to 2020). They all underwent extensive removal of the synkinetic muscles and triggered facial nerve branches in the cheek, nose, and neck regions, followed by gracilis functioning free muscle transplantation for facial reanimation. Ninety-four patients (50 with type II and 44 with type III postparalytic facial synkinesis), all of whom had at least 1 year of postoperative follow-up, were included in the study. Patient demographics and functional and aesthetic evaluations before and after surgery were collected.
Results:
In the yearly distribution of the facial paralysis reconstruction, the incidence of surgical intervention increased from 15 percent before 2012 up to 24 percent in the years after. Young adults (79 percent) and female patients (63 percent) were the dominant population. Results showed a significant improvement of the facial smile quality, with more teeth visible while smiling, and a long-lasting decrease of facial synkinesis. Ninety-six percent of patients did not require botulinum toxin type A injection after surgery. Revision surgery for secondary deformity was 53 percent.
Conclusions:
Combined myectomy and neurectomy followed by functioning free muscle transplantation for type II and III synkinetic patients leads to promising and long-lasting results despite high revision rates. Refined techniques to decrease the revision rates are needed in the future.
CLINICAL QUESTION/LEVEL OF EVIDENCE:
Therapeutic, IV.
Terminal Schwann cells (tSCs), nonmyelinating glial cells at the neuromuscular junction (NMJ), are integral to NMJ development, function, remodeling, and response to injury. It is essential to ...understand their requirement for NMJ function. In this study, the authors assessed consequences of immune-mediated tSC ablation in adult S100 -GFP mice of both sexes in homeostasis and after nerve injury.
The authors examined NMJ morphology and function in the extensor digitorum longus muscle during homeostasis at post-tSC ablation days 3, 14, and 42 and after peroneal nerve transection and immediate repair at 3 and 6 weeks after nerve injury and tSC ablation (postinjury and ablation).
tSC ablation resulted in significant decreases ( P < 0.05) in tSC numbers per NMJ and end plate fragmentation. NMJ innervation and EDL tetanic force were significantly decreased at post-tSC ablation day 14 ( P < 0.05) and tSCs reestablished their NMJ coverage at post-tSC ablation day 42. After nerve injury, motor end plate fragmentation increased ( P < 0.01) with tSC ablation compared with injured control mice. NMJ reinnervation and extensor digitorum longus tetanic force were significantly reduced ( P < 0.001), even at 6 weeks postinjury and ablation, compared with control mice.
These results add to the understanding that tSCs, with their proregenerative potential, help maintain NMJ integrity in homeostasis and are necessary for NMJ reinnervation after peripheral nerve injury.
Terminal Schwann cells are integral for efficient NMJ recovery after nerve injury. This cell population may provide a novel therapeutic target to improve outcomes for patients with nerve injuries; additional investigation is warranted.
Objectives
This study aimed to investigate the association between salivary matrix metalloproteinase‐1 (MMP‐1) and clinicopathological parameters of oral cavity squamous cell carcinoma (OSCC) and ...compare the prognostic efficacy of salivary MMP‐1 and other established circulating markers for OSCC.
Methods
Saliva specimens from 479 OSCC subjects were examined using an enzyme‐linked immunosorbent assay. The area under the curve (AUC) values of salivary MMP‐1 and other markers were calculated, and survival analyses were conducted using Kaplan–Meier and multivariate regression methods.
Results
Salivary MMP‐1 showed good discrimination in predicting overall survival, with an AUC of 0.638, which was significantly higher than that of albumin (0.530, p = .021) and Charlson comorbidity index (0.568, p = .048) and comparable with neutrophil‐to‐lymphocyte ratio (0.620, p = .987), platelet‐to‐lymphocyte ratio (0.575, p = .125), and squamous cell carcinoma antigen (0.609, p = .605). Elevated levels of salivary MMP‐1 were significantly associated with higher pT classification, pN classification, overall pathological stage, positive extranodal extension, tumor differentiation, positive lymphovascular invasion, positive perineural invasion, and tumor depth (p all <.05). Multivariate analyses indicated that a higher level of salivary MMP‐1 (≥2060.0 pg/mL) was an independent predictive factor of poorer overall survival (adjusted hazard ratio: 1.421 95% confidential interval: 1.014–1.989, p = .041).
Conclusion
The study found that the salivary MMP‐1 level was significantly associated with many adverse clinicopathological parameters of OSCC. In OSCC, it was found to have superior efficacy in predicting prognosis and was an independent prognostic factor of post‐treatment outcome.
Level of evidence
3.
Salivary MMP‐1 showed a significantly higher AUC than albumin and CCI and a higher or comparable AUC to the NLR, the PLR, and SCCA in predicting overall survival in OSCC patients. The study also indicates that patients with high levels of salivary MMP‐1 have poorer prognosis in terms of OS and DSS. Overall, these findings may facilitate development of a noninvasive and user‐friendly salivary detection tool for OSCC treatment.
The presence of online learning resources has grown tremendously in recent years. They provide powerful and yet easily accessible means of learning and sharing knowledge. Online learning resources ...now encompass all aspects of medicine, and microsurgery is no exception. International Microsurgery Club is a closed, invitation-only group based on the Facebook social media platform. It was initiated on May 6, 2016, with the primary objectives of providing a convenient forum for discussing challenging cases, sharing valuable resources, and providing opportunities for research collaboration. The membership of International Microsurgery Club has grown to over 8700 at 2 years’ existence, and continues to expand. International Microsurgery Club has become one of the largest online platforms for global microsurgeons. Here, the authors share their experience on how to establish a successful online platform for medical education.
Objectives
The aim of this meta‐analysis is to evaluate the potential benefits of postoperative radiotherapy (PORT) in patients with pN1 oral cavity squamous cell carcinoma.
Methods
A literature ...search through major databases was conducted until January 2023. The adjusted hazard ratio (aHR) or risk ratio (RR) with 95% confidence intervals (CIs) of different survival outcomes were extracted and pooled.
Results
Ten studies published between 2005 and 2022, with a pooled patient population of 2888, were included in this meta‐analysis. Due to differences in study design and reported outcomes, the studies were categorized into distinct groups. In pN1 patients without extranodal extension (ENE), PORT was associated with a significant improvement in overall survival (OS) (aHR 0.76, 95% CI: 0.61–0.94). In pN1 patients without ENE and positive margins, PORT improved OS (aHR 0.71, 95% CI: 0.56–0.89) and was associated with a lower regional recurrence rate (RR 0.35, 95% CI: 0.15–0.83). However, in pN1 patients without ENE, positive margins, perineural invasion, and lymphovascular invasion, there were no significant differences observed between the PORT and observation groups in either 5‐year OS (RR 0.48, 95% CI: 0.07–3.41) or 5‐year disease‐free survival (RR 0.37, 95% CI: 0.07–2.06).
Conclusions
The current study demonstrated that PORT has the potential to improve OS in pN1 disease. However, the decision of whether to administer PORT still hinges on diverse clinical scenarios, and additional research is necessary to furnish a more conclusive resolution.
Level of Evidence
2.
This meta‐analysis is the first to examine the role of PORT in pN1 OSCC patients. PORT improved survival in the patients only without ENE and positive margins. The benefit of PORT remains inconclusive in those studies excluding intermediate risk factors.
Nerve reconstruction after 6 months of denervation time in brachial plexus injuries (BPIs) can be inconsistent. A dilemma exists when the use of critical donor nerves for nerve transfers may lead to ...unreliable outcomes that would waste the donor nerve. The purpose of this study was to evaluate the long-term outcomes of elbow and shoulder function in patients with BPIs receiving nerve reconstruction in the delayed setting (i.e., 6-12 months after injury).
Data from patients with delayed BPIs who received a nerve transfer (including proximal and distal nerve transfer/grafting) at a tertiary medical center were retrospectively collected from January 1999 to March 2020. Demographics, extent of injury, mechanism of injury, and reconstructive methods were collected. Patients were categorized into two groups: non-pan-plexus BPI (C5-6, C5-7, and C5-8) and pan-plexus BPI (C5-T1). Acceptable outcome was defined as elbow flexion ≥ M3 status or shoulder abduction ≥ 60°.
Sixty-four patients were included in the study. The average time from injury to nerve reconstruction was 236 (range 180-441) days, and the average follow-up time was 66 months. In the non-pan-plexus BPI group (n = 43 patients), 74.4% of patients demonstrated M3 elbow flexion, and 48.8% of patients demonstrated M4 elbow flexion. Double fascicular transfer yielded better results and faster recovery than a single fascicular transfer. In the pan-plexus BPI group (n = 21 patients), 38.1% of patients reached M3 elbow flexion and 23.8% attained M4 elbow flexion. In the non-pan-plexus BPI group, the recovery rate of acceptable shoulder abduction was 53.5%, but only 23.5% of pan-plexus patients with BPI achieved acceptable shoulder abduction.
Nerve reconstruction can effectively restore functional elbow flexion and acceptable shoulder abduction in non-pan-plexus patients with BPI in the delayed setting. However, neither acceptable elbow flexion nor shoulder abduction could be consistently achieved in pan-plexus BPI. Judicious use of the donor nerves in pan-plexus injuries is required, in addition to preserving a donor nerve for a backup plan such as free-functioning muscle transplantation or tendon transfers.
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