Clinical Neuroscience

The dermal papilla (DP) provide instructive signals required to activate epithelial progenitors and initiate hair follicle regeneration. DP cell numbers fluctuate over the hair cycle, and hair loss is associated with gradual depletion/atrophy of DP cells. How DP cell numbers are maintained in healthy follicles remains unclear. We performed in vivo fate mapping of adult hair follicle dermal sheath (DS) cells to determine their lineage relationship with DP and found that a subset of DS cells are retained following each hair cycle, exhibit self-renewal, and repopulate the DS and the DP with new cells. Ablating these hair follicle dermal stem cells and their progeny retarded hair regrowth and altered hair type specification, suggesting that they function to modulate normal DP function. This work identifies a bipotent stem cell within the adult hair follicle mesenchyme and has important implications toward restoration of hair growth after injury, disease, and aging.

Traumatic neuroma in continuity (NIC) results in profound neurological deficits, and its management poses the most challenging problem to peripheral nerve surgeons today. The absence of a clinically relevant experimental model continues to handicap our ability to investigate ways of better diagnosis and treatment for these disabling injuries. Various injury techniques were tested on Lewis rat sciatic nerves. Optimal experimental injuries that consistently resulted in NIC combined both intense focal compression and traction forces. Nerves were harvested at 0, 5, 13, 21, and 65 days for histological examination. Skilled locomotion and ground reaction force (GRF) analysis were performed up to 9 weeks on the experimental (n = 6) and crush-control injuries (n = 5). Focal widening, disruption of endoneurium and perineurium with aberrant intra-and extrafascicular axonal regeneration and progressive fibrosis was consistently demonstrated in 14 of 14 nerves with refined experimental injuries. At 8 weeks, experimental animals displayed a significantly greater slip ratio in both skilled locomotor assessments, compared to nerve crush animals ( p < 0.01). GRFs of the crush-injured animals showed earlier improvement compared to the experimental animals, whose overall GRF patterns failed to recover as well as the crush group. We have demonstrated histological features and poor functional recovery consistent with NIC formation in a rat model. The injury mechanism employed combines traction and compression forces akin to the physical forces at play in clinical nerve injuries. This model may serve as a tool to help diagnose this injury earlier and to develop intervention strategies to improve patient outcomes.

Despite the innate capacity of peripheral nervous system to regenerate, patients with severe nerve injury, especially those subjected to chronic nerve denervation, never regain full function, despite conventional nerve repair. The goal of this thesis is to iteratively evaluate a SC population derived from rodent and human skin towards the ultimate goal of improved autologous cell transplantation therapy to augment nerve repair. Skin derived precursors (SKPs) are multipotent stem cells with phenotypic similarities to neural crest cells. Upon transplantation into dysmyelinated or injured peripheral nerves, neonatal SKP-SCs survive, ensheath and myelinate regenerating axons and demonstrate superior indices of axonal regeneration. In this thesis, we demonstrate for the first time that, neonatal SKP-SCs therapy improves functional recovery in an array of behavioral tests in acute and delayed nerve repair models. Towards our goal of autologous therapies, we assessed adult SKP-SCs (aSKP-SCs), for promyelinating transcription factor expression, proliferation, neurite outgrowth, and remyelination. We also isolated and cultured SCs from acutely (day 5 post injury) and chronically (day 56 post injury) denervated nerves and performed detailed immunophenotypic characterization. Our data suggest that acutely denervated SCs are very potent but chronically denervated nerve SCs fail to exhibit comparable myelinating phenotype, exhibit retarded proliferation, show diminished neurite outgrowth, and demonstrate inferior in vitro/in vivo myelination as compared to acutely injured nerve SCs. We found that aSKP-SCs are very similar to acutely or embryonic nerve SCs and significantly superior to chronically denervated nerve SCs. We asked if there is a similar population of SCs in adult human skin, which may exhibit similarities to aSKP-SCs. We explored a novel population of SCs from human skin and compared them to human nerve derived SCs. Our data indicates that human skin derived SCs also express markers of promyelinating SC phenotype, and in preliminary experiments appears to have the capacity to ensheath and myelinate rodent axons in NOD-SCID mice. We further conclude that aSKP-SCslike population of SCs exists in adult human skin, which shows great promise and requires further exploration to ascertain their potential for enhanced nerve repair in animal models of nerve injury, prior to clinical translation.

While damaged peripheral nerves demonstrate some potential to regenerate, complete functional recovery remains infrequent, owing to a functional loss of supportive Schwann cells distal to the injury. An emerging solution to improve upon this intrinsic regenerative capacity is to supplement injured nerves with stem cells derived from various tissues. While many of these strategies have proven successful in animal models, few studies have examined the behavior of transplanted stem cells in vivo, including whether they survive and differentiate. In previous work, we demonstrated that cells derived from neonatal rodent dermis (skin-derived precursor cells, or SKPs) could improve regenerative parameters when transplanted distal to both acute and chronic nerve injuries in Lewis rats. The aim of this work was to track the fate of these cells in various nerve injury paradigms and determine the response of these cells to a known glial growth factor. Here, we report that SKPs survive, respond to local cues, differentiate into myelinating Schwann cells, and avoid complete clearance by the host's immune defenses for a minimum of 10 weeks. Moreover, the ultimate fate of SKPs in vivo depends on the nerve environment into which they are injected and can be modified by inclusion of heregulin-1β.

Object Cell therapy is a promising candidate among biological or technological innovations sought to augment microsurgical techniques in peripheral nerve repair. This report describes long-term functional regenerative effects of cell therapy in the rat injury model with a focus on sensory recovery. Methods Schwann cells were derived from isogenic nerve or skin precursor cells and injected into the transected and immediately repaired sciatic nerve distal to the injury site. Sensory recovery was assessed at weeks 4, 7, and 10. Axonal regeneration was assessed at Week 11. Results By Week 10, thermal sensitivity in cell therapy groups returned to a level indistinguishable from the baseline (p &gt; 0.05). Immunohistochemistry at 11 weeks after injury showed improved regeneration of NF+ and IB4+ axons. Conclusions: The results of this study show that cell therapy significantly improves thermal sensation and the number of regenerated sensory neurons at 11 weeks after injury. These findings...

OBJECTIVE Intravital spectral imaging of the large, deeply situated nerves in the rat peripheral nervous system (PNS) has not been well described. Here, the authors have developed a highly stable platform for performing imaging of the tibial nerve in live rodents, thus allowing the capture of high-resolution, high-magnification spectral images requiring long acquisition times. By further exploiting the qualities of the topically applied myelin dye Nile red, this technique is capable of visualizing the detailed microenvironment of peripheral nerve demyelination injury and recovery, while allowing us to obtain images of exogenous Schwann cell myelination in a living animal. METHODS The authors caused doxorubicin-induced focal demyelination in the tibial nerves of 25 Thy-1 GFP rats, of which 2 subsets (n = 10 each) received either BFP-labeled SKP-SCs or SCs to the zone of injury. Prior to acquiring images of myelin recovery in these nerves, a tibial nerve window was constructed using a...

Deciphering avenues to adequately control malignancies in the peripheral nerve will reduce the need for current, largely-ineffective, standards of care which includes the use of invasive, nerve-damaging, resection surgery. By avoiding the need for en bloc resection surgery, the likelihood of retained function or efficient nerve regeneration following the control of tumor growth is greater, which has several implications for long-term health and well-being of cancer survivors. Nerve tumors can arise as malignant peripheral nerve sheath tumors (MPNST) that result in a highly-aggressive form of soft tissue sarcoma. Although the precise cause of MPNST remains unknown, studies suggest that dysregulation of Schwann cells, mediated by the microenvironment, plays a key role in tumor progression. This study aimed to further characterize the role of local microenvironment on tumor progression, with an emphasis on identifying factors within tumor suppressive environments that have potential fo...

Stroke thrombolysis is limited by the &quot;last-seen well&quot; principle, which defines stroke onset time. A significant minority of stroke patients (~15%) awake with their symptoms and are by definition ineligible for thrombolysis because they were &quot;last-seen well&quot; at the time they went to bed implying an interval that is most often greater than three hours. A single-centre prospective, safety study was designed to thrombolyse 20 subjects with stroke-on-awakening. Patients were eligible for inclusion if they were last seen well less than 12 hours previously, specifically including those who awoke from sleep with their stroke deficits. They had a baseline computed tomogram (CT) scan with an ASPECTS score greater than 5, no evidence of well-evolved infarction and a CT angiogram / Trans-cranial Doppler ultrasound study demonstrating an intracranial arterial occlusion. Patients fulfilled all other standard criteria for stroke thrombolysis. The primary outcome was safety def...

Background Risk of a subsequent stroke following an acute transient ischemic attack (TIA) or minor stroke is high. The ABCD2 tool was proposed as a method to triage these patients using five clinical factors. Modern imaging of the brain was not included. The present study quantified the added value of magnetic resonance imaging (MRI) factors to the ABCD2 tool. Methods Patients with TIA or minor stroke were examined within 12 h and had a brain MRI within 24 h of symptom onset. Primary outcomes were recurrent stroke and functional impairment at 90 days. A new tool, ABCD2+ MRI, was created by adding diffusion-weighted imaging lesion and vessel occlusion status to the ABCD2 tool. The predictive accuracy of both tools was quantified by the area under the curve (AUC). Results One hundred and eighty patients were enrolled and 11·1% had a recurrent stroke within 90 days. The predictive accuracy of the ABCD2+MRI was significantly higher than ABCD2 (AUC of 0·88 vs. 0·78, P = 0·01). Those with...

Minor stroke and transient ischemic attack with an intracranial occlusion are associated with neurological deterioration and disability. Tenecteplase (TNK-tissue-type plasminogen activator) compared with alteplase is easier to administer, has a longer half-life, higher fibrin specificity, possibly a lower rate of intracranial hemorrhage, and may be an ideal thrombolytic agent in this population. TNK-Tissue-Type Plasminogen Activator Evaluation for Minor Ischemic Stroke With Proven Occlusion (TEMPO-1) was a multicenter, prospective, uncontrolled, TNK-tissue-type plasminogen activator dose-escalation, safety, and feasibility trial. Patients with a National Institutes of Health Stroke Scale ≤5 within 12 hours of symptom onset, intracranial arterial occlusion on computed tomographic angiography and absence of well-evolved infarction were eligible. Fifty patients were enrolled; 25 patients at a dose of 0.1 mg/kg, and 25 patients at 0.25 mg/kg. Primary outcome was the rate of drug-related...

Background Nerinetide, an eicosapeptide that interferes with post-synaptic density protein 95, is a neuroprotectant that is effective in preclinical stroke models of ischaemia-reperfusion. In this trial, we assessed the efficacy and safety of nerinetide in human ischaemia-reperfusion that occurs with rapid endovascular thrombectomy in patients who had an acute ischaemic stroke. Methods For this multicentre, double-blind, randomised, placebo-controlled study done in 48 acute care hospitals in eight countries, we enrolled patients with acute ischaemic stroke due to large vessel occlusion within a 12 h treatment window. Eligible patients were aged 18 years or older with a disabling ischaemic stroke at the time of randomisation, had been functioning independently in the community before the stroke, had an Alberta Stroke Program Early CT Score (ASPECTS) greater than 4, and vascular imaging showing moderate-to-good collateral filling, as determined by multiphase CT angiography. Patients were randomly assigned (1:1) to receive intravenous nerinetide in a single dose of 2•6 mg/kg, up to a maximum dose of 270 mg, on the basis of estimated or actual weight (if known) or saline placebo by use of a real-time, dynamic, internet-based, stratified randomised minimisation procedure. Patients were stratified by intravenous alteplase treatment and declared endovascular device choice. All trial personnel and patients were masked to sequence and treatment allocation. All patients underwent endovascular thrombectomy and received alteplase in usual care when indicated. The primary outcome was a favourable functional outcome 90 days after randomisation, defined as a modified Rankin Scale (mRS) score of 0-2. Secondary outcomes were measures of neurological disability, functional independence in activities of daily living, excellent functional outcome (mRS 0-1), and mortality. The analysis was done in the intention-to-treat population and adjusted for age, sex, baseline National Institutes of Health Stroke Scale score, ASPECTS, occlusion location, site, alteplase use, and declared first device. The safety population included all patients who received any amount of study drug. This trial is registered with ClinicalTrials.gov, NCT02930018.

IMPORTANCE Some patients have poor outcomes despite small infarcts after endovascular therapy (EVT), while others with large infarcts do well. Understanding why these discrepancies occur may help to optimize EVT outcomes. OBJECTIVE To validate exploratory findings from the Endovascular Treatment for Small Core and Anterior Circulation Proximal Occlusion with Emphasis on Minimizing CT to Recanalization Times (ESCAPE) trial regarding pretreatment, treatment-related, and posttreatment factors associated with discrepancies between follow-up infarct volume (FIV) and 90-day functional outcome. DESIGN, SETTING, AND PARTICIPANTS This cohort study is a post hoc analysis of the Safety and Efficacy of Nerinetide in Subjects Undergoing Endovascular Thrombectomy for Stroke (ESCAPE-NA1) trial, a double-blind, randomized, placebo-controlled, international, multicenter trial conducted from March 2017 to August 2019. Patients who participated in ESCAPE-NA1 and had available 90-day modified Rankin Scale (mRS) scores and 24-hour to 48-hour posttreatment follow-up parenchymal imaging were included. EXPOSURES Small FIV (volume Յ25th percentile) and large FIV (volume Ն75th percentile) on 24-hour computed tomography/magnetic resonance imaging. Baseline factors, outcomes, treatments, and poststroke serious adverse events (SAEs) were compared between discrepant cases (ie, patients with 90-day mRS score Ն3 despite small FIV or those with mRS scores Յ2 despite large FIV) and nondiscrepant cases. MAIN OUTCOMES AND MEASURES Area under the curve (AUC) and goodness of fit of prespecified logistic models, including pretreatment (eg, age, cancer, vascular risk factors) and treatment-related and posttreatment (eg, SAEs) factors, were compared with stepwise regression-derived models for ability to identify small FIV with higher mRS score and large FIV with lower mRS score. RESULTS Among 1091 patients (median [IQR] age, 70.8 [60.8-79.8] years; 549 [49.7%] women; median [IQR] FIV, 24.9 mL [6.6-92.2 mL]), 42 of 287 patients (14.6%) with FIV of 7 mL or less (ie, Յ25th percentile) had an mRS score of at least 3; 65 of 275 patients (23.6%) with FIV of 92 mL or greater (ie, Ն75th percentile) had an mRS score of 2 or less. Prespecified models of pretreatment factors (ie, age, cancer, vascular risk factors) associated with low FIV and higher mRS score performed similarly to models selected by stepwise regression (AUC, 0.92 [95% CI, 0.89-0.95] vs 0.93 [95% CI, 0.90-0.95]; P = .42). SAEs, specifically infarct in new territory, recurrent stroke, pneumonia, and congestive heart failure, were associated with low FIV and higher mRS scores; stepwise models also identified 24-hour hemoglobin as treatment-related/posttreatment factor (continued) Key Points Question Why do some patients have poor outcomes despite small infarcts after endovascular therapy, while others with large infarcts fare better? Findings In this cohort study of 1091 patients who received endovascular therapy as part of a randomized clinical trial, discrepancies between infarct volume and functional outcome were associated with prespecified pretreatment factors, such as age, cancer, and vascular risk factors, as well as posttreatment factors, such as infarct in new territory, stroke progression, intracerebral hemorrhage, recurrent stroke, pneumonia, and heart failure. Models including these factors performed similar to those derived from stepwise regressions. Meaning In this study, discrepancies between outcome and infarct volume were associated with pretreatment and posttreatment factors, including complications related to index stroke evolution, secondary prevention, and quality of stroke unit care.