Epidemiology of peripheral nerve and brachial plexus injuries in a trauma population.

BACKGROUND: Understanding patterns of peripheral nerve injuries (PNIs) and brachial plexus injuries (BPIs) is essential to preventing and appropriately managing nerve injuries. We sought to assess the incidence, cause, and severity of PNIs and BPIs sustained by patients with trauma. METHODS: We conducted a retrospective review of the Trauma Registry Database (January 2002 to December 2020) to identify patients with PNIs or BPIs. RESULTS: We evaluated data from 24 905 patients with trauma; 335 (1.3%) sustained PNIs (81% male; mean age 36 yr, standard deviation [SD] 16 yr) and 64 (0.3%) sustained BPIs (84% male; mean age 35, SD 15 yr). Nerves in the upper extremities were more commonly affected than those in the lower extremities. Sharp injuries (39.4%) and motorcycle accidents (32.8%) were the most frequent causes of PNIs and BPIs, respectively. Other common causes of PNI were motor vehicle collisions (16.7%) and gunshot wounds (12.8%). Many patients with PNIs (69.0%) and BPIs (53%) underwent operative management. The most frequent reconstruction for PNI was primary nerve repair (66%), while nerve transfers (48%) were more frequently used for BPI. CONCLUSION: Nerve injuries in the trauma population have decreased over the last 3 decades with shifts in mechanisms of injury and use of imaging, electrodiagnostic tests, and surgery. Nerve injuries are often complex and time-sensitive to treat; understanding changes in trends is important to ensure optimal patient management.

Behavioral and axon histomorphometric analyses after intraneural transplantation of human skin- and nerve-derived Schwann cells in nude rats.

INTRODUCTION/AIMS: We have recently isolated and expanded skin-derived Schwann cells (Sk-SCs) from human skin and showed that they are largely similar to nerve-derived Schwann cells (N-SCs). Here, we extend our investigation into functional assessments of the nude rats that received human Sk-SCs and N-SCs after intraneural delivery into crushed and decellularized tibial nerve in adult nude rats. METHODS: Sk-SCs, N-SCs, dermal fibroblasts, or control culture medium was injected into the crushed and decellularized tibial nerve using in situ repeated freeze-thaw cycles. Animals were then subjected to a ladder rung walking test, nociceptive von Frey testing, and walking gait analysis weekly. Animals were euthanized 6 weeks after surgery, gastrocnemius and soleus muscles were weighed, distal nerves were harvested, and whole semithin cross-sections were analyzed using segmentation software. RESULTS: N-SC-injected and dermal fibroblast-injected animals improved significantly at 4 to 6 weeks postinjury in nociceptive assessment compared with medium-injected controls. Sk-SCs recovered more rapidly in tibial functional index at 2 weeks postinjury compared with medium-injected controls. No significant difference was observed for the ladder rung walking test or muscle weight ratio. Histologically, the number of myelinated axons was significantly higher in all cell injection groups compared with medium-injected controls. No significant difference was observed in g ratio, axon diameter, or myelin thickness. DISCUSSION: Cell injection significantly improved axon regeneration across an in situ decellularized nerve segment. However, a more human cell-permissive animal model is required to delineate functional differences between cell types for preclinical transplantation studies.

Causalgia: A Review of Nerve Resection, Amputation, Immunotherapy, and Amputated Limb CRPS II Pathology.

BACKGROUND: Causalgia and complex regional pain syndrome (CRPS) type II with nerve injury can be difficult to treat. Surgical peripheral nerve denervation for causalgia has been largely abandoned by pain clinicians because of a perception that this may aggravate a central component (anesthesia dolorosa). METHODS: We selectively searched Pubmed, Cochrane, MEDLINE, EMBASE, CINAHL Plus, and Scopus from 1947 for articles, books, and book chapters for evidence of surgical treatments (nerve resection and amputation) and treatment related to autoimmunity and immune deficiency with CRPS. RESULTS: Reviews were found for the treatment of causalgia or CRPS type II (n = 6), causalgia relieved by nerve resection (n = 6), and causalgia and CRPS II treated by amputation (n = 8). Twelve reports were found of autoimmunity with CRPS, one paper of these on associated immune deficiency and autoimmunity, and two were chosen for discussion regarding treatment with immunoglobulin and one by plasma exchange. We document a report of a detailed and unique pathological examination of a CRPS type II affected amputated limb and related successful treatment with immunoglobulin. CONCLUSIONS: Nerve resection, with grafting, and relocation may relieve uncomplicated causalgia and CRPS type II in some patients in the long term. However, an unrecognized and treatable immunological condition may underly some CRPS II cases and can lead to the ultimate failure of surgical treatments.

Barriers to Surgical Intervention and Factors Influencing Motor Outcomes in Patients with Severe Peripheral Nerve Injury: A Province Wide Cohort Study.

INTRODUCTION: Despite the importance of timing of nerve surgery after peripheral nerve injury, optimal timing of intervention has not been clearly delineated. The goal of this study is to explore factors that may have a significant impact on clinical outcomes of severe peripheral nerve injury that requires reconstruction with nerve transfer or graft. MATERIALS AND METHODS: Adult patients who underwent peripheral nerve transfer or grafting in Alberta were reviewed. Clustered multivariable logistic regression analysis was used to examine the association of time to surgery, type of nerve repair, and patient characteristics on strength outcomes. Cox proportional hazard regression analysis model was used to examine factors correlated with increased time to surgery. RESULTS: Of the 163 patients identified, the median time to surgery was 212 days. For every week of delay, the adjusted odds of achieving Medical Research Council strength grade ≥ 3 decreases by 3%. An increase in preinjury comorbidities was associated with longer overall time to surgery (aHR 0.84, 95% CI 0.74-0.95). Referrals made by surgeons were associated with a shorter time to surgery compared to general practitioners (aHR 1.87, 95% CI 1.14-3.06). In patients treated with nerve transfer, the adjusted odds of achieving antigravity strength was 388% compared to nerve grafting; while the adjusted odds decreased by 65% if the injury sustained had a pre-ganglionic injury component. CONCLUSION: Mitigating delays in surgical intervention is crucial to optimizing outcomes. The nature of initial nerve injury and surgical reconstructive techniques are additional important factors that impact postoperative outcomes.

A Multi-Stage Bioprocess for the Expansion of Rodent Skin-Derived Schwann Cells in Computer-Controlled Bioreactors.

Regenerative therapies for the treatment of peripheral nerve and spinal cord injuries can require hundreds of millions of autologous cells. Current treatments involve the harvest of Schwann cells (SCs) from nerves; however, this is an invasive procedure. Therefore, a promising alternative is using skin-derived Schwann cells (Sk-SCs), in which between 3-5 million cells can be harvested from a standard skin biopsy. However, traditional static planar culture is still inefficient at expanding cells to clinically relevant numbers. As a result, bioreactors can be used to develop reproducible bioprocesses for the large-scale expansion of therapeutic cells. Here, we present a proof-of-concept SC manufacturing bioprocess using rat Sk-SCs. With this integrated process, we were able to simulate a feasible bioprocess, taking into consideration the harvest and shipment of cells to a production facility, the generation of the final cell product, and the cryopreservation and shipment of cells back to the clinic and patient. This process started with 3 million cells and inoculated and expanded them to over 200 million cells in 6 days. Following the harvest and post-harvest cryopreservation and thaw, we were able to maintain 150 million viable cells that exhibited a characteristic Schwann cell phenotype throughout each step of the process. This process led to a 50-fold expansion, producing a clinically relevant number of cells in a 500 mL bioreactor in just 1 week, which is a dramatic improvement over current methods of expansion.

Comparison of human skin- and nerve-derived Schwann cells reveals many similarities and subtle genomic and functional differences.

Skin is an easily accessible tissue and a rich source of Schwann cells (SCs). Toward potential clinical application of autologous SC therapies, we aim to improve the reliability and specificity of our protocol to obtain SCs from small skin samples. As well, to explore potential functional distinctions between skin-derived SCs (Sk-SCs) and nerve-derived SCs (N-SCs), we used single-cell RNA-sequencing and a series of in vitro and in vivo assays. Our results showed that Sk-SCs expressed typical SC markers. Single-cell sequencing of Sk- and N-SCs revealed an overwhelming overlap in gene expression with the exception of HLA genes which were preferentially up-regulated in Sk-SCs. In vitro, both cell types exhibited similar levels of proliferation, migration, uptake of myelin debris and readily associated with neurites when co-cultured with human iPSC-induced motor neurons. Both exhibited ensheathment of multiple neurites and early phase of myelination, especially in N-SCs. Interestingly, dorsal root ganglion (DRG) neurite outgrowth assay showed substantially more complexed neurite outgrowth in DRGs exposed to Sk-SC conditioned media compared to those from N-SCs. Multiplex ELISA array revealed shared growth factor profiles, but Sk-SCs expressed a higher level of VEGF. Transplantation of Sk- and N-SCs into injured peripheral nerve in nude rats and NOD-SCID mice showed close association of both SCs to regenerating axons. Myelination of rodent axons was observed infrequently by N-SCs, but absent in Sk-SC xenografts. Overall, our results showed that Sk-SCs share near-identical properties to N-SCs but with subtle differences that could potentially enhance their therapeutic utility.

Stem-cell-based therapies to enhance peripheral nerve regeneration.

Peripheral nerve injury remains a major cause of morbidity in trauma patients. Despite advances in microsurgical techniques and improved understanding of nerve regeneration, obtaining satisfactory outcomes after peripheral nerve injury remains a difficult clinical problem. There is a growing body of evidence in preclinical animal studies demonstrating the supportive role of stem cells in peripheral nerve regeneration after injury. The characteristics of both mesoderm-derived and ectoderm-derived stem cell types and their role in peripheral nerve regeneration are discussed, specifically focusing on the presentation of both foundational laboratory studies and translational applications. The current state of clinical translation is presented, with an emphasis on both ethical considerations of using stems cells in humans and current governmental regulatory policies. Current advancements in cell-based therapies represent a promising future with regard to supporting nerve regeneration and achieving significant functional recovery after debilitating nerve injuries.

Recent advances in nerve repair.

Peripheral nerve injuries are extremely devastating, and their management is exceedingly complex. Microsurgical repair is the mainstay of treatment and this includes direct nerve repair, nerve grafts, nerve tubes and nerve transfers. Today, nerve transfers are being widely performed due to an increased understanding of cortical plasticity, motor re-education and perioperative rehabilitation, and they are now known to produce excellent functional outcomes. This manuscript reviews the current strategies for nerve repair, including comments on outcomes, with special emphasis on existing nerve transfer techniques.

The immunomodulatory properties of adult skin-derived precursor Schwann cells: implications for peripheral nerve injury therapy.

Skin-derived precursor Schwann cell (SKPSC) therapy has been identified as a potentially beneficial treatment for peripheral nerve injuries. One hypothesised mechanism by which SKPSCs enhance recovery is via the modulation of macrophages. In the present study, we investigated the immunomodulatory properties of adult rat SKPSCs, and demonstrated that these cells expressed a battery of cytokines, including interferon-γ (IFN-γ), interleukin (IL)-1ß, and, most abundantly, IL-6. Whereas macrophages exposed to depleted or fibroblast-conditioned medium secreted minimal amounts of tumor necrosis factor-α (TNF-α), in the presence of SKPSC-conditioned medium, macrophages secreted > 500 pg/mL TNF-α. Following the transplantation of SKPSCs into injured rat sciatic nerves, we observed an SKPSC density-dependent increase in the number of macrophages (Pearson's r = 0.66) and an SKPSC density-dependent decrease in myelin debris (Pearson's r = -0.68). To determine the effect of IL-6 in a proinflammatory context, macrophage cultures were primed with either lipopolysaccharide (LPS)/IFN-γ/IL-1ß or LPS/IFN-γ/IL-1ß + IL-6, and this showed a 212% and 301% increase in the number of inducible nitric oxide synthase (iNOS)-positive proinflammatory macrophages respectively. In contrast to neurons exposed to conditioned medium from unprimed macrophages, neurons treated with conditioned medium from proinflammatory-primed macrophages showed a 13-26% reduction in neurite outgrowth. Anti-IL-6 antibody combined with SKPSC transplant therapy following nerve injury did not alter macrophage numbers or debris clearance, but instead reduced iNOS expression as compared with SKPSC + IgG-treated rats. SKPSC + anti-IL-6 treatment also resulted in a two-fold increase in gastrocnemius compound muscle action potential amplitudes as compared with SKPSC + IgG treatment. Understanding the mechanisms underlying immunomodulatory aspects of SKPSC therapy and developing approaches to manipulate these responses are important for advancing Schwann cell-based therapies.

Inter-microcarrier transfer and phenotypic stability of stem cell-derived Schwann cells in stirred suspension bioreactor culture.

Emerging bioreactor technologies offer an effective way for scaled-up production of large numbers of cells for cell therapy applications. One of the clinical paradigms where cell therapy can be an asset is restorative neurosciences. Nerve repair can benefit from the injections of stem cells and/or Schwann cells, acting as a source for axon myelination, myelin debris clearance, and trophic support. We have adapted microcarrier-based suspension bioreactor culture for Schwann cells (SCs) differentiated from a new stem cell source - skin-derived precursors (SKPs). SKP-derived SCs attach and grow on different types of microcarriers in both static and stirred culture, with Cytodex 3 and CultiSpher-S found most effective. Inter-microcarrier migration of SKP-SCs represents a key mechanism for rapid expansion and colonization in stirred suspension culture. We have shown that microcarrier-expanded SKP-SCs cells express Schwann cell markers p75-NTR, GFAP and S100 and retain their key ability to myelinate axons both in vitro and in vivo. Scaled-up microcarrier-based production of SKP-SCs in suspension bioreactors appears feasible for timely generation of sufficient cell numbers for nerve repair strategies.

The mechanism underlying combined medial and lateral plantar and tibial intraneural ganglia in the tarsal tunnel.

Intraneural ganglion cysts in the tarsal tunnel are rare. We present a patient who had an intraneural ganglion cyst involving the medial and lateral plantar and distal tibial nerves. Magnetic resonance imaging revealed evidence to support the joint-related (i.e., subtalar) origin of the cyst. Careful reinterpretation of the imaging supported a phasic mechanism (i.e., cross-over) to explain the interrelated pathogenesis of the intraneural cyst within the three nerves. This mechanism is analogous to that described for the prototypes-the peroneal, tibial and sciatic nerves in the knee region-and can be generalized to other nerves in the foot and ankle region. We believe that understanding the pathogenesis sheds light on the effective treatment.

Adult brachial plexus injuries: Surgical strategies and approaches.

Traumatic brachial plexus injuries are devastating injuries commonly affecting the young population and leading to significant socioeconomic losses to the society. The results of brachial plexus surgery have been severely disappointing in the past. However, several technological advancements and newer surgical techniques, especially the advent of distal nerve transfers over recent years, have led to a paradigm shift in the outcome of patients with these injuries. The best time window for surgery is the first 3 months after injury, and the next best time is the next 3 months. The timing is a crucial factor as the neuromuscular junctions degenerate in 20-24 months. The presence of spontaneous fibrillations in a muscle on electromyography is an indication of denervated yet vital muscle. The restoration of elbow flexion is a priority followed closely by restoration of shoulder abduction and stabilization. The various surgical strategies in brachial plexus injuries should be directed toward accomplishing this goal. The global avulsion injuries have a poor outcome because of very limited source of donors in such types of injury whereas the partial injuries have a remarkable outcome in a majority of cases. This article presents the reader with the guidelines and management algorithms of repair strategy and various surgical approaches utilized in the surgical treatment of brachial plexus injuries.

Phase I/II trial of neoadjuvant sunitinib administered with weekly paclitaxel/carboplatin in patients with locally advanced triple-negative breast cancer.

The purpose of the study is to evaluate the feasibility and efficacy of adding sunitinib to paclitaxel/carboplatin in the neoadjuvant therapy of patients with triple-negative breast cancer (TNBC). Patients had histologically proven, previously untreated, triple-negative adenocarcinoma, with disease limited to the breast and axilla (clinical T1-T3, N0-N2, M0; T1N1M0 excluded). Following determination of the maximum tolerated doses in the phase I portion, patients in the phase II study received paclitaxel 70 mg/m(2) IV days 1, 8, and 15; carboplatin AUC 5.0 IV day 1; sunitinib 25 mg orally daily; treatment was administered for six 28-day cycles followed by definitive surgery. Sunitinib was resumed postoperatively to complete a 52-week course. Pathologic complete response (pCR) rate was the primary endpoint. Fifty-four patients enrolled; 41 received treatment in the phase II study. Sixteen patients (39 %) were able to complete six cycles of neoadjuvant therapy; 18 additional patients had surgery after completing 2-5 cycles of treatment. The pCR rate in these 34 evaluable patients was 35 %. The toxicity of the regimen was considerable, with myelosuppression resulting in numerous dose reductions and/or omissions of paclitaxel and carboplatin. Eleven patients (27 %) discontinued sunitinib during neoadjuvant therapy, and six patients (14 %) completed 52 weeks of single-agent sunitinib. In the neoadjuvant treatment of patients with TNBC, the combination of paclitaxel, carboplatin, and sunitinib was difficult to administer, and produced a pCR rate comparable to other less toxic regimens. This combination is not recommended for further evaluation. At present, sunitinib has no defined role in the treatment of breast cancer.

Management of brachial plexus injuries in adults: Clinical evaluation and diagnosis.

Brachial plexus injuries are devastating injuries that usually affect the younger population. The usual modes of injuries are roadside accidents, falls, and assaults. The affected individuals are crippled and may suffer from excruciating peripheral or central deafferentation pain for rest of their lives. The loss of functional capacity accounts for a significant number of man-hours lost at the workplace and consequent financial burden on the family. The results of brachial plexus reconstructive surgery have generally been unsatisfactory in the past. However, in recent decades, the efficacy of surgery has been proven beyond doubt, and there have been various published series in literature that have reported a good outcome after surgical management of these injuries. This has been made possible by the use of operating microscopes, better microsuture techniques for nerve graft and nerve or tendon transfer repair, and advanced perioperative electrophysiological techniques. The key to successful management lies in the proper clinical evaluation, supplemented with electrophysiology, preoperative imaging studies, and planning of surgical strategy. The partial injuries have a better outcome as compared with global palsies, and early referral should be emphasized. Selective combinations of nerve graft and transfers provide a moderate shoulder and elbow control. However, a multispecialty approach involving hand surgeons, plastic surgeons, and physiotherapists is required.

Recent advances in stem cell-mediated peripheral nerve repair.

A major advance in the field of peripheral nerve repair has been the advent of stem and progenitor cell use to supplement the regenerative environment in animal models of nerve injury. As Schwann cell replacements, stem cells may be even better suited to promoting regeneration in these scenarios. We review the recent literature detailing the search for the definitive Schwann cell replacement cell, including a look at genetic modification of transplanted cells for nerve injury repair.

Skin-derived precursor Schwann cell myelination capacity in focal tibial demyelination.

INTRODUCTION: Skin-derived precursor cells (SKPs) are neural crest progenitor cells that can attain a Schwann cell-like phenotype through in vitro techniques (SKP-SCs). We hypothesized that SKP-SCs could produce mature myelin and, in doing so, facilitate the recovery of a focal demyelination injury. METHODS: We unilaterally injected DiI-labeled, green fluorescent protein (GFP)-producing SKP-SCs into the tibial nerves of 10 adult Lewis rats (with contralateral media control), 9 days after bilateral doxorubicin injury (0.38 µg). Tibial compound motor action potentials (CMAPs) were followed for 57 days. A separate morphometric cohort also included a Schwann cell injection group. RESULTS: SKP-injected nerves recovered fastest in terms of electrophysiology and morphometry. SKP-SCs formed morphologically mature myelin, accounting for 15.3 ± 5.3% of the total myelin in SKP-SC-injected nerves. CONCLUSIONS: SKP-SCs are robustly capable of myelination. They improve the recovery of a focal tibial nerve demyelination model by myelinating a measured percentage of axons.

Aligned collagen-GAG matrix as a 3D substrate for Schwann cell migration and dendrimer-based gene delivery.

The development of artificial off-the-shelf conduits that facilitate effective nerve regeneration and recovery after repair of traumatic nerve injury gaps is of fundamental importance. Collagen-glycosaminoglycan (GAG) matrix mimicking Schwann cell (SC) basal lamina has been proposed as a suitable and biologically rational substrate for nerve regeneration. In the present study, we have focused on the permissiveness of this matrix type for SC migration and repopulation, as these events play an essential role in nerve remodeling. We have also demonstrated that SCs cultured within collagen-GAG matrix are compatible with non-viral dendrimer-based gene delivery, that may allow conditioning of matrix-embedded cells for future gene therapy applications.

Surgery for mononeuropathies.

Advancement in microsurgical techniques and innovative approaches including greater use of nerve and tendon transfers have resulted in better peripheral nerve injury (PNI) surgical outcomes. Clinical evaluation of the patient and their injury factors along with a shift toward earlier time frame for intervention remain key. A better understanding of the pathophysiology and biology involved in PNI and specifically mononeuropathies along with advances in ultrasound and magnetic resonance imaging allow us, nowadays, to provide our patients with a logical and sophisticated approach. While functional outcomes are constantly being refined through different surgical techniques, basic scientific concepts are being advanced and translated to clinical practice on a continuous basis. Finally, a combination of nerve transfers and technological advances in nerve/brain and machine interfaces are expanding the scope of nerve surgery to help patients with amputations, spinal cord, and brain lesions.

Novel AAV variants with improved tropism for human Schwann cells.

Gene therapies and associated technologies are transforming biomedical research and enabling novel therapeutic options for patients living with debilitating and incurable genetic disorders. The vector system based on recombinant adeno-associated viral vectors (AAVs) has shown great promise in recent clinical trials for genetic diseases of multiple organs, such as the liver and the nervous system. Despite recent successes toward the development of novel bioengineered AAV variants for improved transduction of primary human tissues and cells, vectors that can efficiently transduce human Schwann cells (hSCs) have yet to be identified. Here, we report the application of the functional transduction-RNA selection method in primary hSCs for the development of AAV variants for specific and efficient transgene delivery to hSCs. The two identified capsid variants, Pep2hSC1 and Pep2hSC2, show conserved potency for delivery across various in vitro, in vivo, and ex vivo models of hSCs. These novel AAV capsids will serve as valuable research tools, forming the basis for therapeutic solutions for both SC-related disorders or peripheral nervous system injury.