Distinct Effector B Cells Induced by Unregulated Toll-like Receptor 7 Contribute to Pathogenic Responses in Systemic Lupus Erythematosus.

Systemic Lupus Erythematosus (SLE) is characterized by B cells lacking IgD and CD27 (double negative; DN). We show that DN cell expansions reflected a subset of CXCR5- CD11c+ cells (DN2) representing pre-plasma cells (PC). DN2 cells predominated in African-American patients with active disease and nephritis, anti-Smith and anti-RNA autoantibodies. They expressed a T-bet transcriptional network; increased Toll-like receptor-7 (TLR7); lacked the negative TLR regulator TRAF5; and were hyper-responsive to TLR7. DN2 cells shared with activated naive cells (aNAV), phenotypic and functional features, and similar transcriptomes. Their PC differentiation and autoantibody production was driven by TLR7 in an interleukin-21 (IL-21)-mediated fashion. An in vivo developmental link between aNAV, DN2 cells, and PC was demonstrated by clonal sharing. This study defines a distinct differentiation fate of autoreactive naive B cells into PC precursors with hyper-responsiveness to innate stimuli, as well as establishes prominence of extra-follicular B cell activation in SLE, and identifies therapeutic targets.

Scleroderma Renal Crisis: Clues From the Physical Exam.

Scleroderma renal crisis (SRC) is a rare, life-threatening complication of systemic sclerosis (SSc) and can sometimes be the first manifestation of the disease.1 A 56-year-old female presented with acute encephalopathy requiring intubation and a systolic blood pressure of 230 mmHg; no information was available about her medical history.

Editorial Commentary: Tissue-Engineered Meniscal Scaffolds and Implants Show Promising Short-Term Outcomes While Long-Term Comparison With Meniscal Allograft Transplantation Is Pending.

Because of the prevalence of meniscal injuries and the difficulty treating irreparable tears and large defects, there has been increasing research and resultant engineering strategies over the past 20 years that have resulted in development of various meniscal scaffolds and meniscal implants. At this time, meniscal allograft transplant may be the "standard" consideration for the nonarthritis, meniscal deficient, stable, and properly aligned painful knee, but challenges include availability, preoperative planning and sizing, costs, and logistics. Newer tissue-engineered implants can minimize these concerns, and recent systematic review shows these may provide short-term improvement in knee pain and function. However, studies demonstrating long-term improvements remain pending, and it is unclear whether these implants will result in outcomes better than meniscal allograft transplant.

A functional aged human iPSC-cortical neuron model recapitulates Alzheimer's disease, senescence, and the response to therapeutics.

INTRODUCTION: The degeneration of cortical layers is associated with cognitive decline in Alzheimer's disease (AD). Current therapies for AD are not disease-modifying, and, despite substantial efforts, research and development for AD has faced formidable challenges. In addition, cellular senescence has emerged as a significant contributor to therapy resistance. METHODS: Human iPSC-derived cortical neurons were cultured on microelectrode arrays to measure long-term potentiation (LTP) noninvasively. Neurons were treated with pathogenic amyloid-ß (Aß) to analyze senescence and response to therapeutic molecules. RESULTS: Microphysiological recordings revealed Aß dampened cortical LTP activity and accelerated neuronal senescence. Aging neurons secreted inflammatory factors previously detected in brain, plasma, and cerebral spinal fluid of AD patients, in which drugs modulated senescence-related factors. DISCUSSION: This platform measures and records neuronal LTP activity in response to Aß and therapeutic molecules in real-time. Efficacy data from similar platforms have been accepted by the FDA for neurodegenerative diseases, expediting regulatory submissions. HIGHLIGHTS: This work developed a progerontic model of amyloid-ß (Aß)-driven cortical degeneration. This work measured neuronal LTP and correlated function with aging biomarkers. Aß is a driver of neuronal senescence and cortical degeneration. Molecules rescued neuronal function but did not halt Aß-driven senescence. Therapeutic molecules modulated secretion of inflammatory factors by aging neurons.

Identification of Factors that May Predict Career Trajectory Among Neuro-Ophthalmology Fellows.

BACKGROUND: There is modest literature regarding fellowship applicant factors that may predict future career achievement. We aim to characterize neuro-ophthalmology fellows and identify and analyze characteristics that may predict future career trajectory. METHODS: Data, including demographic information, academic background, scholarly activities, and practice information, were collected using publicly available sources, on individuals who completed neuro-ophthalmology fellowships from 2015 to 2021. Summary statistics describing the cohort were calculated. Prefellowship characteristics were compared with postfellowship characteristics to evaluate which prefellowship characteristics may predict postfellowship academic productivity and career achievement. RESULTS: Data were collected on 174 individuals (41.6% men, 58.4% women). Sixty-five percent were residency-trained in ophthalmology, 31% neurology, 1.7% both, and 1.7% pediatric neurology. Fifty-eight percent completed residency in the US, 8% in Canada, 32% internationally, and 2% in multiple locations. Among those practicing in the US/Canada, 63.8% practice at academic centers, 35.3% private practice, and 0.9% at both. Thirty-one percent completed additional subspecialty training and 17.8% additional graduate degrees. Completion of additional fellowship training or graduate degrees, and publication of more papers before fellowship, correlated with later academic productivity. There were no significant correlations between completion of an additional fellowship or graduate degree with current practice environment or attainment of leadership roles. There were no significant correlations between total publishing productivity prefellowship and practice environment or leadership roles postfellowship. CONCLUSIONS: Additional graduate degrees/subspecialty training, and prefellowship academic productivity, correlated with later academic productivity among neuro-ophthalmologists, suggesting that these metrics may be helpful in predicting future academic performance among fellowship applicants.

Evaluating a 3D deep learning pipeline for cerebral vessel and intracranial aneurysm segmentation from computed tomography angiography-digital subtraction angiography image pairs.

OBJECTIVE: Computed tomography angiography (CTA) is the most widely used imaging modality for intracranial aneurysm (IA) management, yet it remains inferior to digital subtraction angiography (DSA) for IA detection, particularly of small IAs in the cavernous carotid region. The authors evaluated a deep learning pipeline for segmentation of vessels and IAs from CTA using coregistered, segmented DSA images as ground truth. METHODS: Using 50 paired CTA-DSA images, the authors trained (n = 27), validated (n = 3), and tested (n = 20) a deep learning model (3D DeepMedic) for cerebrovasculature segmentation from CTA. A landmark-based coregistration algorithm was used for registration and upsampling of CTA images to paired DSA images. Segmented vessels from the DSA were used as the ground truth. Accuracy of the model for vessel segmentation was evaluated using conventional metrics (dice similarity coefficient [DSC]) and vessel segmentation-specific metrics, like connectivity-area-length (CAL). On the test cases (20 IAs), 3 expert raters attempted to detect and segment IAs. For each rater, the authors recorded the rate of IA detection, and for detected IAs, raters segmented and calculated important IA morphology parameters to quantify the differences in IA segmentation by raters to segmentations by DeepMedic. The agreement between raters, DeepMedic, and ground truth was assessed using Krippendorf's alpha. RESULTS: In testing, the DeepMedic model yielded a CAL of 0.971 ± 0.007 and a DSC of 0.868 ± 0.008. The model prediction delineated all IAs and resulted in average error rates of < 10% for all IA morphometrics. Conversely, average IA detection accuracy by the raters was 0.653 (undetected IAs were present to a significantly greater degree on the ICA, likely due to those in the cavernous region, and were significantly smaller). Error rates for IA morphometrics in rater-segmented cases were significantly higher than in DeepMedic-segmented cases, particularly for neck (p = 0.003) and surface area (p = 0.04). For IA morphology, agreement between the raters was acceptable for most metrics, except for the undulation index (α = 0.36) and the nonsphericity index (α = 0.69). Agreement between DeepMedic and ground truth was consistently higher compared with that between expert raters and ground truth. CONCLUSIONS: This CTA segmentation network (DeepMedic trained on DSA-segmented vessels) provides a high-fidelity solution for CTA vessel segmentation, particularly for vessels and IAs in the carotid cavernous region.

Biallelic variants in HPDL, encoding 4-hydroxyphenylpyruvate dioxygenase-like protein, lead to an infantile neurodegenerative condition.

PURPOSE: Dioxygenases are oxidoreductase enzymes with roles in metabolic pathways necessary for aerobic life. 4-hydroxyphenylpyruvate dioxygenase-like protein (HPDL), encoded by HPDL, is an orphan paralogue of 4-hydroxyphenylpyruvate dioxygenase (HPD), an iron-dependent dioxygenase involved in tyrosine catabolism. The function and association of HPDL with human diseases remain unknown. METHODS: We applied exome sequencing in a cohort of over 10,000 individuals with neurodevelopmental diseases. Effects of HPDL loss were investigated in vitro and in vivo, and through mass spectrometry analysis. Evolutionary analysis was performed to investigate the potential functional separation of HPDL from HPD. RESULTS: We identified biallelic variants in HPDL in eight families displaying recessive inheritance. Knockout mice closely phenocopied humans and showed evidence of apoptosis in multiple cellular lineages within the cerebral cortex. HPDL is a single-exonic gene that likely arose from a retrotransposition event at the base of the tetrapod lineage, and unlike HPD, HPDL is mitochondria-localized. Metabolic profiling of HPDL mutant cells and mice showed no evidence of altered tyrosine metabolites, but rather notable accumulations in other metabolic pathways. CONCLUSION: The mitochondrial localization, along with its disrupted metabolic profile, suggests HPDL loss in humans links to a unique neurometabolic mitochondrial infantile neurodegenerative condition.

Capacitively-Coupled ECG and Respiration for Sleep-Wake Prediction and Risk Detection in Sleep Apnea Patients.

Obstructive sleep apnea (OSA) patients would strongly benefit from comfortable home diagnosis, during which detection of wakefulness is essential. Therefore, capacitively-coupled electrocardiogram (ccECG) and bioimpedance (ccBioZ) sensors were used to record the sleep of suspected OSA patients, in parallel with polysomnography (PSG). The three objectives were quality assessment of the unobtrusive signals during sleep, prediction of sleep-wake using ccECG and ccBioZ, and detection of high-risk OSA patients. First, signal quality indicators (SQIs) determined the data coverage of ccECG and ccBioZ. Then, a multimodal convolutional neural network (CNN) for sleep-wake prediction was tested on these preprocessed ccECG and ccBioZ data. Finally, two indices derived from this prediction detected patients at risk. The data included 187 PSG recordings of suspected OSA patients, 36 (dataset "Test") of which were recorded simultaneously with PSG, ccECG, and ccBioZ. As a result, two improvements were made compared to prior studies. First, the ccBioZ signal coverage increased significantly due to adaptation of the acquisition system. Secondly, the utility of the sleep-wake classifier increased as it became a unimodal network only requiring respiratory input. This was achieved by using data augmentation during training. Sleep-wake prediction on "Test" using PSG respiration resulted in a Cohen's kappa (κ) of 0.39 and using ccBioZ in κ = 0.23. The OSA risk model identified severe OSA patients with a κ of 0.61 for PSG respiration and κ of 0.39 using ccBioZ (accuracy of 80.6% and 69.4%, respectively). This study is one of the first to perform sleep-wake staging on capacitively-coupled respiratory signals in suspected OSA patients and to detect high risk OSA patients based on ccBioZ. The technology and the proposed framework could be applied in multi-night follow-up of OSA patients.

Integrative analysis of rare copy number variants and gene expression data in alopecia areata implicates an aetiological role for autophagy.

Alopecia areata (AA) is a highly prevalent autoimmune disease that attacks the hair follicle and leads to hair loss that can range from small patches to complete loss of scalp and body hair. Our previous linkage and genome-wide association studies (GWAS) generated strong evidence for aetiological contributions from inherited genetic variants at different population frequencies, including both rare mutations and common polymorphisms. Additionally, we conducted gene expression (GE) studies on scalp biopsies of 96 patients and controls to establish signatures of active disease. In this study, we performed an integrative analysis on these two datasets to test the hypothesis that rare CNVs in patients with AA could be leveraged to identify drivers of disease in our AA GE signatures. We analysed copy number variants (CNVs) in a case-control cohort of 673 patients with AA and 16 311 controls independent of the case-control cohort of 96 research participants used in our GE study. Using an integrative computational analysis, we identified 14 genes whose expression levels were altered by CNVs in a consistent direction of effect, corresponding to gene expression changes in lesional skin of patients. Four of these genes were affected by CNVs in three or more unrelated patients with AA, including ATG4B and SMARCA2, which are involved in autophagy and chromatin remodelling, respectively. Our findings identified new classes of genes with potential contributions to AA pathogenesis.

S29434, a Quinone Reductase 2 Inhibitor: Main Biochemical and Cellular Characterization.

Quinone reductase 2 (QR2, E.C. 1.10.5.1) is an enzyme with a feature that has attracted attention for several decades: in standard conditions, instead of recognizing NAD(P)H as an electron donor, it recognizes putative metabolites of NADH, such as N-methyl- and N-ribosyl-dihydronicotinamide. QR2 has been particularly associated with reactive oxygen species and memory, strongly suggesting a link among QR2 (as a possible key element in pro-oxidation), autophagy, and neurodegeneration. In molecular and cellular pharmacology, understanding physiopathological associations can be difficult because of a lack of specific and powerful tools. Here, we present a thorough description of the potent, nanomolar inhibitor [2-(2-methoxy-5H-1,4b,9-triaza(indeno[2,1-a]inden-10-yl)ethyl]-2-furamide (S29434 or NMDPEF; IC50 = 5-16 nM) of QR2 at different organizational levels. We provide full detailed syntheses, describe its cocrystallization with and behavior at QR2 on a millisecond timeline, show that it penetrates cell membranes and inhibits QR2-mediated reactive oxygen species (ROS) production within the 100 nM range, and describe its actions in several in vivo models and lack of actions in various ROS-producing systems. The inhibitor is fairly stable in vivo, penetrates cells, specifically inhibits QR2, and shows activities that suggest a key role for this enzyme in different pathologic conditions, including neurodegenerative diseases.

Effect of protein type, concentration and oil droplet size on the formation of repulsively jammed elastic nanoemulsion gels.

Rheology of sodium caseinate (SC) and whey protein isolate (WPI)-stabilized nanoemulsions (NEs) was investigated as a function of protein (1-5 wt%) and oil (30 and 40 wt%) concentration and storage time. For SC NEs, gel strength increased with an increase in protein and oil concentration and a decrease in droplet size and below a critical size transformed into a strong elastic gel that did not flow under gravity. Surprisingly, WPI NEs, although stable and had similar droplet size to SC NEs, did not form elastic gels. The stability of the NEs was studied for 3 months, and no significant change was observed. Considerable higher storage modulus (G') of SC NEs compared to WPI NEs was attributed to an increased effective droplet volume fraction (φeff) due to a thicker steric barrier of SC compared to WPI. The DLVO interdroplet potential was used to calculate the thickness of the charge cloud at an overall repulsive interaction of 1 kBT, which was added to the steric barrier to calculate the effective droplet size and φeff. At the highest φeff (0.79) for 5% SC NEs with 40% oil, the nanodroplets and associated repulsive barrier randomly jammed, leading to the formation of a strong elastic gel. For WPI NEs, maximum φeff was 0.57, leading to a lack of jamming and viscous fluid-like behaviour. Re-plotting G' with φeff for SC NEs with different protein concentration showed a linear trend followed by a rapid increase in G' at a critical φeff, confirming the transition from weak glassy region to strong randomly jammed structure. SC-stabilized repulsively jammed NE-gels could be used as a novel soft material where a lower oil volume fraction and long-term stability is required.

Drug release kinetics of temperature sensitive liposomes measured at high-temporal resolution with a millifluidic device.

PURPOSE: Current release assays have inadequate temporal resolution ( ∼ 10 s) to characterise temperature sensitive liposomes (TSL) designed for intravascular triggered drug release, where release within the first few seconds is relevant for drug delivery. MATERIALS AND METHODS: We developed a novel release assay based on a millifluidic device. A 500 µm capillary tube was heated by a temperature-controlled Peltier element. A TSL solution encapsulating a fluorescent compound was pumped through the tube, producing a fluorescence gradient along the tube due to TSL release. Release kinetics were measured by analysing fluorescence images of the tube. We measured three TSL formulations: traditional TSL (DPPC:DSPC:DSPE-PEF2000,80:15:5), MSPC-LTSL (DPPC:MSPC:DSPE-PEG2000,85:10:5) and MPPC-LTSL (DPPC:MMPC:PEF2000,86:10:4). TSL were loaded with either carboxyfluorescein (CF), Calcein, tetramethylrhodamine (TMR) or doxorubicin (Dox). TSL were diluted in one of the four buffers: phosphate buffered saline (PBS), 10% bovine serum albumin (BSA) solution, foetal bovine serum (FBS) or human plasma. Release was measured between 37-45 °C. RESULTS: The millifluidic device allowed measurement of release kinetics within the first few seconds at ∼5 ms temporal resolution. Dox had the fastest release and highest release %, followed by CF, Calcein and TMR. Of the four buffers, release was fastest in human plasma, followed by FBS, BSA and PBS. CONCLUSIONS: The millifluidic device allows measurement of TSL release at unprecedented temporal resolution, thus allowing adequate characterisation of TSL release at time scales relevant for intravascular triggered drug release. The type of buffer and encapsulated compound significantly affect release kinetics and need to be considered when designing and evaluating novel TSL-drug combinations.

Molecular Landscape and Therapeutic Strategies against Colorectal Cancer.

Colorectal cancer (CRC) is the second leading cause of cancer deaths worldwide. Although the overall incidence of CRC is decreasing, the incidence of young-onset CRC, characterized by a diagnosis of CRC before age 50, is increasing. Outcomes for CRC patients are improving, partly due to comprehensive molecular characterization of tumors and novel therapeutic strategies. Advances in genomic and transcriptomic analyses using blood- and tumor-tissue-based sequencing have facilitated identification of distinct tumor subtypes harboring unique biological characteristics and therapeutic vulnerabilities. These insights have led to the development and incorporation of targeted therapies and immunotherapy in CRC treatment. In this review, we discuss the molecular landscape and key oncogenes/tumor suppressors contributing to CRC tumorigenesis, metastasis, and therapeutic resistance. We also discuss personalized therapeutic strategies for subsets of CRC patients and provide an overview of evolving novel treatments being evaluated in clinical trials.

Multiple Anomalous Coronary Arteries With Right Sinus of Valsalva Origin: A Case Report.

Coronary artery anomalies (CAA) define a wide array of congenital abnormalities that stem from the origin, course, and distribution of coronary arteries. CAAs can lead to severe complications such as arrhythmias, myocardial ischemia, and even sudden cardiac death. We describe the case of a 58-year-old female who presented to the emergency department with chest discomfort and shortness of breath and received a workup for acute coronary syndrome. She underwent a cardiac catheterization, which incidentally found an anomalous left anterior descending artery with a right sinus of Valsalva origin, an absent left circumflex coronary artery, and a dominant right coronary artery of unusually large caliber and distribution. There were no identified atherosclerotic plaques. This anomalous configuration of the coronary arteries is exceptionally rare. She required medical management with daily oral acetylsalicylic acid 81 mg, atorvastatin 80 mg, twice daily metoprolol tartrate 50 mg, and hydrocodone/acetaminophen 7.5mg/325 mg oral tablet to be taken every 4 h, as needed for severe pain. Despite optimal medical management, she continued to have chronic angina. A surgical evaluation by a cardiovascular surgeon deemed her anomaly to be inoperable.

Diffusion Basis Spectrum Imaging of White Matter in Schizophrenia and Bipolar Disorder.

Background: Multiple studies point to the role of neuroinflammation in the pathophysiology of schizophrenia (SCZ), however, there have been few in vivo tools for imaging brain inflammation. Diffusion basis spectrum imaging (DBSI) is an advanced diffusion-based MRI method developed to quantitatively assess microstructural alternations relating to neuroinflammation, axonal fiber, and other white matter (WM) pathologies. Methods: We acquired one-hour-long high-directional diffusion MRI data from young control (CON, n = 27), schizophrenia (SCZ, n = 21), and bipolar disorder (BPD, n = 21) participants aged 18-30. We applied Tract-based Spatial Statistics (TBSS) to allow whole-brain WM analyses and compare DBSI-derived isotropic and anisotropic diffusion measures between groups. Clinical relationships of DBSI metrics with clinical symptoms were assessed across SCZ and control participants. Results: In SCZ participants, we found a generalized increase in DBSI-derived cellularity (a putative marker of neuroinflammation), a decrease in restricted fiber fraction (a putative marker of apparent axonal density), and an increase in extra-axonal water (a putative marker of vasogenic edema) across several WM tracts. There were only minimal WM abnormalities noted in BPD, mainly in regions of the corpus callosum (increase in DTI-derived RD and extra-axonal water). DBSI metrics showed significant partial correlations with psychosis and mood symptoms across groups. Conclusion: Our findings suggest that SCZ involves generalized white matter neuroinflammation, decreased fiber density, and demyelination, which is not seen in bipolar disorder. Larger studies are needed to identify medication-related effects. DBSI metrics could help identify high-risk groups requiring early interventions to prevent the onset of psychosis and improve outcomes.

No Difference in Pullout Strength Between a Bio-inductive Implant and a Semitendinosus Tendon Graft in a Biomechanical Study of Medial Patellofemoral Ligament Repair Augmentation.

Purpose: To compare the pullout strength of a bio-inductive implant (BI) used to augment a medial patellofemoral ligament (MPFL) repair with the pullout strength of semitendinosus graft in a biomechanical cadaveric model. Methods: Six matched pairs of cadavers (12 knees) were used in the biomechanical testing comparing semitendinosus tendon (Semi-T) versus a BI. The Semi-T was harvested from 1 of the matched pairs. A standard double-bundle technique using 2 sockets in the upper two-thirds of the patella 15 mm apart was performed. After docking of the graft into the patella, the patella was dissected free of soft tissues and potted into a fixture to allow mechanical pull parallel to the transverse axis of the patella. The construct was pulled to failure. Results: There was no statistically significant difference in pullout strength (P = .77) between the BI group (249.3 ± 36.3 N) and Semi-T group (235.0 ± 113.6 N) double-bundle constructs. In the Semi-T group, 50% of the specimens (3 of 6 knees) failed via anchor pullout and a fourth specimen failed at the suture-anchor interface (16.7%), whereas in the BI group, 16.7% of the specimens (1 of 6 knees) failed by anchor pullout. Although the Semi-T group (49.5 ± 14.1 N/mm) showed significantly greater stiffness than the BI group (13.8 ± 0.6 N/mm, P < .01), pullout strength in the Semi-T group was highly variable: 50% of the specimens (3 of 6 knees) with semitendinosus constructs failed at 5 mm of displacement or less via graft or anchor pullout. Maximum load, displacement at failure, stiffness, and load at 5 mm were compared between the augmented and non-augmented control specimens using a 2-tailed non-equal variance Student t test. For all comparisons, P < .05 was considered to indicate a statistically significant difference. Conclusions: In this biomechanical study, augmentation of an MPFL reconstruction using a common double-bundle technique with a BI had the same pullout strength as a semitendinosus graft using the same technique in cadaveric knees. Clinical Relevance: MPFL repair after a patellar dislocation may be inadequate to restore the strength of the native MPFL and prevent recurrent patellar instability. Recurrent instability of the patella can result in progressive injury to the soft tissue and articular cartilage of the patella and femur. It is important to study the techniques used for MPFL repair to continually improve patient outcomes. Further testing of these additional techniques and clinical studies are needed to evaluate the implants used to augment MPFL repairs.

Paralumbar compartment syndrome, a rare sequela of deadlifting: a case report and review of current literature.

BACKGROUND: Compartment syndrome is a well-known phenomenon that is most commonly reported in the extremities. However, paralumbar compartment syndrome is rarely described in available literature. The authors present a case of paralumbar compartment syndrome after high intensity deadlifting. CASE PRESENTATION: 53-year-old male who presented with progressively worsening low back pain and paresthesias one day after high-intensity deadlifting. Laboratory testing found the patient to be in rhabdomyolysis; he was admitted for intravenous fluid resuscitation and pain control. Orthopedics was consulted, and Magnetic Resonance Imaging revealed significant paravertebral edema and loss of muscle striation. Given the patient's lack of improvement with intravenous and oral pain control, clinical and radiographic findings, there was significant concern for acute paralumbar compartment syndrome. The patient subsequently underwent urgent fasciotomy of bilateral paralumbar musculature with delayed closure. CONCLUSION: Given the paucity of literature on paralumbar compartment syndrome, the authors' goal is to promote awareness of the diagnosis, as it should be included in the differential diagnosis of intractable back pain after high exertional exercise. The current literature suggests that operative cases of paralumbar compartment syndromes have a higher rate of return to pre-operative function compared to those treated non-operatively. This case report further supports this notion. The authors recommend further study into this phenomenon, given its potential to result in persistent chronic exertional pain and irreversible tissue damage.

Establishment of a Serum-Free Human iPSC-Derived Model of Peripheral Myelination.

Myelination and the formation of nodes of Ranvier are essential for the rapid conduction of nerve impulses along axons in the peripheral nervous system (PNS). While many animal-based and serum-containing models of peripheral myelination have been developed, these have limited ability when it comes to studying genetic disorders affecting peripheral myelination. We report a fully induced pluripotent stem cell (iPSC)-derived human model of peripheral myelination using Schwann cells (SCs) and motoneurons, cultured in a serum-free medium on patterned and nonpatterned surfaces. Results demonstrated iPSC-derived SC-expressed early growth response protein 2 (Egr2), a key transcription factor for myelination, and after ∼30 days in coculture, hallmark features of myelination, including myelin segment and node of Ranvier formation, were observed. Myelin segments were stained for the myelin basic protein, which surrounded neurofilament-stained motoneuron axons. Clusters of voltage-gated sodium channels flanked by paranodal protein contactin-associated protein 1, indicating node of Ranvier formation, were also observed. High-resolution confocal microscopy allowed for 3D reconstruction and measurement of myelin g-ratios of myelin segments, with an average g-ratio of 0.67, consistent with reported values in the literature, indicating mature myelin segment formation. This iPSC-based model of peripheral myelination provides a platform to investigate numerous PNS diseases, including Charcot-Marie Tooth disorder, Guillian-Barre syndrome, chronic inflammatory demyelinating polyneuropathy, and antimyelin-associated glycoprotein peripheral neuropathy, with the potential for greater translatability to humans for improving the applicability for drug-screening programs.