Intraepidermal Nerve Fiber Research Articles

TS-HDS autoantibody: clinical characterization and utility from real-world tertiary care center experience.

To evaluate clinical utility of trisulfated-heparin disaccharide (TS-HDS) IgM testing from real-world tertiary care center experience. Medical records of patients with positive TS-HDS antibodies who were evaluated at Mayo Clinic from 2009 to 2022 were reviewed. Seventy-seven patients (50 females) had positive TS-HDS antibody. Median age was 48 (9-77) years. Median titer was 25,000 (range 11,000-350,000). Twenty-six patients (34%) did not have objective evidence of peripheral neuropathy. Nine patients (12%) had other known causes of neuropathy. Among the remaining 42 patients, half presented with subacute progressive course; the other half had chronic indolent course. Most common phenotypes were length-dependent peripheral neuropathy (n = 20, 48%), length-dependent small-fiber neuropathy (n = 11, 26%), and non-length-dependent small-fiber neuropathy (n = 7, 17%). Nerve biopsies showed epineurial inflammatory cell collections in 2 but no interstitial abnormalities in the remaining 7. The majority of intraepidermal nerve fiber densities (7/10), thermoregulatory sweat tests (12/21) and autonomic reflex screens (27/49) were normal. Post-immunotherapy improvement in mRS/INCAT disability score/pain was only seen in 13/42 (31%) TS-HDS IgM positive patients. Patients presenting with sensory ganglionopathy, non-length dependent small-fiber neuropathy, or subacute progressive neuropathy with and without TS-HDS antibody responded similarly to immunotherapy (40% vs 80%, p = 0.30). TS-HDS IgM has limited phenotypic or disease specificity; it was found to be positive among patients with various neuropathy phenotypes as well as patients without objective evidence of neuropathy. Clinical improvement with immunotherapy, although was observed in a small proportion of TS-HDS IgM seropositive patients, was not more frequent when compared to seronegative patients with similar presentations.

Neuropathy in adolescents with type 1 diabetes: Confirmatory diagnostic tests, bedside tests, and risk factors

AimsTo estimate the prevalence of large fiber (LFN), small fiber (SFN), and autonomic neuropathy in adolescents with type 1 diabetes using confirmatory tests known from adults and to identify risk factors and bedside methods for neuropathy. MethodsSixty adolescents with type 1 diabetes (diabetes duration > five years) and 23 control subjects underwent neurological examination and confirmatory diagnostic tests for neuropathy, including nerve conduction studies, skin biopsies determining intraepidermal nerve fiber density, quantitative sudomotor axon reflex test (QSART), cardiovascular reflex tests (CARTs), and tilt table test. Possible risk factors were analyzed. Bedside tests (biothesiometry, DPNCheck®, Sudoscan, and Vagus®device) were compared with the confirmatory tests using ROC analysis. ResultsThe prevalence of neuropathies in the adolescents with diabetes (mean HbA1c 7.6% (60 mmol/mol)) was as follows: 14% confirmed/26% subclinical LFN, 2% confirmed/25% subclinical SFN, 20% abnormal QSART, 8% abnormal CARTs, and 14% orthostatic hypotension. Higher age, higher insulin dose, previous smoking, and higher triglycerides level were found to increase the relative risk for neuropathy. The bedside tests showed poor to acceptable concordance with the confirmatory tests (all, AUC ≤ 0.75). ConclusionsThe diagnostic tests confirmed the presence of neuropathy in adolescents with diabetes and underscore the importance of prevention and screening.

Expression in skin biopsies supports genetic evidence linking CAMKK2, P2X7R and P2X4R with HIV-associated sensory neuropathy

HIV-associated sensory neuropathy (HIV-SN) affects 14–38% of HIV+ individuals stable on therapy with no neurotoxic drugs. Polymorphisms in CAMKK2, P2X7R and P2X4R associated with altered risk of HIV-SN in Indonesian and South African patients. The role of CaMKK2 in neuronal repair makes this an attractive candidate, but a direct role for any protein is predicated on expression in affected tissues. Here, we describe expression of CaMKK2, P2X7R and P2X4R proteins in skin biopsies from the lower legs of HIV+ Indonesians with and without HIV-SN, and healthy controls (HC). HIV-SN was diagnosed using the Brief Peripheral Neuropathy Screen. Biopsies were stained to detect protein gene product 9.5 on nerve fibres and CaMKK2, P2X7R or P2X4R, and were examined using 3-colour sequential scanning confocal microscopy. Intraepidermal nerve fibre densities (IENFD) were lower in HIV+ donors than HC and correlated directly with nadir CD4 T-cell counts (r = 0.69, p = 0.004). However, IENFD counts were similar in HIV-SN+ and HIV-SN− donors (p = 0.19) and so did not define neuropathy. CaMKK2+ cells were located close to dermal and epidermal nerve fibres and were rare in HC and HIV-SN− donors, consistent with a role for the protein in nerve damage and/or repair. P2X7R was expressed by cells in blood vessels of HIV-SN− donors, but rarely in HC or HIV-SN+ donors. P2X4R expression by cells in the epidermal basal layer appeared greatest in HIV-SN+ donors. Overall, the differential expression of CaMKK2, P2X7R and P2X4R supports the genetic evidence of a role for these proteins in HIV-SN.

Gadolinium contrast agents: dermal deposits and potential effects on epidermal small nerve fibers

Small fiber neuropathy (SFN) affects unmyelinated and thinly myelinated nerve fibers causing neuropathic pain with distal distribution and autonomic symptoms. In idiopathic SFN (iSFN), 30% of the cases, the underlying aetiology remains unknown. Gadolinium (Gd)-based contrast agents (GBCA) are widely used in magnetic resonance imaging (MRI). However, side-effects including musculoskeletal disorders and burning skin sensations were reported. We investigated if dermal Gd deposits are more prevalent in iSFN patients exposed to GBCAs, and if dermal nerve fiber density and clinical parameters are likewise affected. 28 patients (19 females) with confirmed or no GBCA exposure were recruited in three German neuromuscular centers. ISFN was confirmed by clinical, neurophysiological, laboratory and genetic investigations. Six volunteers (two females) served as controls. Distal leg skin biopsies were obtained according to European recommendations. In these samples Gd was quantified by elemental bioimaging and intraepidermal nerve fibers (IENF) density via immunofluorescence analysis. Pain phenotyping was performed in all patients, quantitative sensory testing (QST) only in a subset (15 patients; 54%). All patients reported neuropathic pain, described as burning (n = 17), jabbing (n = 16) and hot (n = 11) and five QST scores were significantly altered. Compared to an equal distribution significantly more patients reported GBCA exposures (82%), while 18% confirmed no exposures. Compared to unexposed patients/controls significantly increased Gd deposits and lower z-scores of the IENF density were confirmed in exposed patients. QST scores and pain characteristics were not affected. This study suggests that GBCA exposure might alter IENF density in iSFN patients. Our results pave the road for further studies investigating the possible role of GBCA in small fiber damage, but more investigations and larger samples are needed to draw firm conclusions.

Skin Denervation Occurrence in Patients with Small Fiber Neuropathy Associated Symptoms Following Covid19 Vaccination and Infection (P13-8.004)

<h3>Objective:</h3> To determine the frequency of skin denervation in patients with SFN-related symptoms following Covid19 vaccination or infection. <h3>Background:</h3> Small fiber neuropathy (SFN) is associated with sensory and autonomic symptoms as well as fatigue, and is evident by skin biopsy which shows a reduction of the intra-epidermal nerve fiber density (IENFD) indicating skin denervation. These SFN-related symptoms are commonly reported following Covid19 vaccination and infection, and SFN was reported following both conditions. However, it is not clear if skin denervation is common in patients reporting these symptoms after Covid19 vaccination or infection. <h3>Design/Methods:</h3> A cross-sectional chart-review analysis of patients who were referred for a skin biopsy due to SFN-related symptoms during 2021. Patients were included if symptoms began within 1–60 days following Covid19 vaccination or infection. <h3>Results:</h3> We identified 22 patients, of which 17 (14 females, mean age 51, range 33–83) reported symptoms following vaccination. These occurred in 10 patients after the 1st, in 5 after the 2nd and in 2 after the 3rd dose, respectively. Symptoms following infection were reported by 5 patients (3 females, mean age 45, range 25–59). The mean time to symptoms onset following vaccination or infection was 9 and 27 days, respectively. All patients reported pain and sensory symptoms. Autonomic symptoms were reported by 8/17 (47%) following vaccination and by 3/5 patients (60%) following infection. Fatigue was reported by 11/17 patients (64%) following vaccination and by all patients following infection. Skin denervation was evident in 13/22 (59%) of patients; in 11/17 patients (64%) following vaccination and 2/5 patients (40%) following infection. Fisher’s exact test showed no correlation between skin denervation and autonomic symptoms (p=0.629) or fatigue (p=0.41). <h3>Conclusions:</h3> This small cohort showed that skin denervation occurs in about half of the patients with SFN-related symptoms following Covid19 vaccination or infection. <b>Disclosure:</b> Dr. Eltity has nothing to disclose. Dr. Zohar has nothing to disclose. Dr. Dori has received personal compensation in the range of $500-$4,999 for serving as a Consultant for TEVA. Dr. Dori has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Takeda . Dr. Dori has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Sanofi. Dr. Dori has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Medison Pharma. Dr. Dori has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Medison Pharma. The institution of Dr. Dori has received research support from Biogen. The institution of Dr. Dori has received research support from Pfizer. The institution of Dr. Dori has received research support from Alnylam therapeutics. Dr. Dori has received intellectual property interests from a discovery or technology relating to health care.

Serum Neurofilament Light Chain Levels in Small Fiber Neuropathy Patients with Skin Denervation and Ongoing Neuropathic Symptoms (P14-8.004)

<h3>Objective:</h3> To identify active axonal damage by measurement of serum neurofilament light chain (sNfL) levels in patients with small fiber neuropathy (SFN) and ongoing neuropathy symptoms. <h3>Background:</h3> SFN is associated with sensory symptoms and is evident by skin biopsy which show a reduction of the intraepidermal nerve fiber density (IENFD) indicating skin denervation. SFN patients may complain of prolonged/worsening symptoms, but it is not clear if this is associated with continuous axonal damage. <h3>Design/Methods:</h3> Blood samples were collected from 95 consecutive patients that were referred for a skin biopsy due to suspected SFN. All patients had symptoms that were consistent with a clinical diagnosis of SFN. Patients were excluded if they had clinical or imaging evidence for a central nervous system disorder, electrodiagnostic abnormalities or absence of electrodiagnostic evaluation. Following these exclusions, 34 patients were included for analysis. Skin biopsy was performed 2–3 months from symptoms onset by 4 patients, 4–12 months by 7, and after more than 12 months by 23. Severe skin denervation was defined by an intraepidermal nerve fiber density (IENFD) below the 5^th percentile per age, mild denervation when the IENFD was at the 5–20^th percentiles, and above the 20^th percentile was considered normal. <h3>Results:</h3> The majority of patients (29/34; 85%) showed normal sNfL levels and almost half of the patients showed skin denervation (15/34; 44%). Two patients with skin denervation (2/15; 13.3%) showed elevated sNfL, after 7 and more than 12 months from symptoms onset. The skin biopsy was normal in the other 3 patients with elevated sNfL, obtained 2, 8 and more than 12 months from symptoms onset. All patients with elevated sNfL had a history of chemotherapy treatment or immune-mediated disorders. <h3>Conclusions:</h3> In this cohort, a small portion of patients with SFN and skin denervation showed increased sNfL which indicated ongoing axonal damage. <b>Disclosure:</b> Dr. Zohar has nothing to disclose. Miss Qassim has nothing to disclose. Dr. Eltity has nothing to disclose. Dr. Keren has nothing to disclose. Efrat Shavit has nothing to disclose. Dr. Chapman has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Mapi Pharma. Dr. Chapman has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Sanofi Genzyme. Dr. Chapman has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Merk Serono. The institution of Dr. Chapman has received research support from Ministry Of Industry. Dr. Dori has received personal compensation in the range of $500-$4,999 for serving as a Consultant for TEVA. Dr. Dori has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Takeda . Dr. Dori has received personal compensation in the range of $500-$4,999 for serving as a Consultant for Sanofi. Dr. Dori has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Medison Pharma. Dr. Dori has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Medison Pharma. The institution of Dr. Dori has received research support from Biogen. The institution of Dr. Dori has received research support from Pfizer. The institution of Dr. Dori has received research support from Alnylam therapeutics. Dr. Dori has received intellectual property interests from a discovery or technology relating to health care.

Abnormal intraepidermal nerve fiber density in disease: A scoping review.

Intraepidermal nerve fiber density (IENFD) has become an important biomarker for neuropathy diagnosis and research. The consequences of reduced IENFD can include sensory dysfunction, pain, and a significant decrease in quality of life. We examined the extent to which IENFD is being used as a tool in human and mouse models and compared the degree of fiber loss between diseases to gain a broader understanding of the existing data collected using this common technique. We conducted a scoping review of publications that used IENFD as a biomarker in human and non-human research. PubMed was used to identify 1,004 initial articles that were then screened to select articles that met the criteria for inclusion. Criteria were chosen to standardize publications so they could be compared rigorously and included having a control group, measuring IENFD in a distal limb, and using protein gene product 9.5 (PGP9.5). We analyzed 397 articles and collected information related to publication year, the condition studied, and the percent IENFD loss. The analysis revealed that the use of IENFD as a tool has been increasing in both human and non-human research. We found that IENFD loss is prevalent in many diseases, and metabolic or diabetes-related diseases were the most studied conditions in humans and rodents. Our analysis identified 73 human diseases in which IENFD was affected, with 71 reporting IENFD loss and an overall average IENFD change of -47%. We identified 28 mouse and 21 rat conditions, with average IENFD changes of -31.6% and -34.7%, respectively. Additionally, we present data describing sub-analyses of IENFD loss according to disease characteristics in diabetes and chemotherapy treatments in humans and rodents. Reduced IENFD occurs in a surprising number of human disease conditions. Abnormal IENFD contributes to important complications, including poor cutaneous vascularization, sensory dysfunction, and pain. Our analysis informs future rodent studies so they may better mirror human diseases impacted by reduced IENFD, highlights the breadth of diseases impacted by IENFD loss, and urges exploration of common mechanisms that lead to substantial IENFD loss as a complication in disease.

Human IAPP is a contributor to painful diabetic peripheral neuropathy.

Peripheral neuropathy is a frequent complication of type 2 diabetes mellitus (T2DM). We investigated whether human islet amyloid polypeptide (hIAPP), which forms pathogenic aggregates that damage pancreatic islet β cells in T2DM, is involved in T2DM-associated peripheral neuropathy. In vitro, hIAPP incubation with sensory neurons reduced neurite outgrowth and increased levels of mitochondrial reactive oxygen species. hIAPP-transgenic mice, which have elevated plasma hIAPP levels without hyperglycemia, developed peripheral neuropathy as evidenced by pain-associated behavior and reduced intraepidermal nerve fiber (IENF) density. Similarly, hIAPP Ob/Ob mice, which have hyperglycemia in combination with elevated plasma hIAPP levels, had signs of neuropathy, although more aggravated. In wild-type mice, intraplantar and intravenous hIAPP injections induced long-lasting allodynia and decreased IENF density. Non-aggregating murine IAPP, mutated hIAPP (pramlintide), or hIAPP with pharmacologically inhibited aggregation did not induce these effects. T2DM patients had reduced IENF density and more hIAPP oligomers in the skin compared with non-T2DM controls. Thus, we provide evidence that hIAPP aggregation is neurotoxic and mediates peripheral neuropathy in mice. The increased abundance of hIAPP aggregates in the skin of T2DM patients supports the notion that hIAPP is a potential contributor to T2DM neuropathy in humans.

Comparison of Novel Wide-Field InVivo Corneal Confocal Microscopy With Skin Biopsy for Assessing Peripheral Neuropathy in Type 2 Diabetes.

Comparison of intraepidermal nerve fiber density with automated wide-field corneal nerve fiber density in participants with type 2 diabetes revealed no correlation between these parameters. Intraepidermal and corneal nerve fibers both detected neurodegeneration in type 2 diabetes, but only intraepidermal nerve fibers were associated with clinical measures of diabetic peripheral neuropathy. A lack of association of corneal nerves with peripheral neuropathy measures suggests that corneal nerve fibers may be a poor biomarker for diabetic peripheral neuropathy.

PD05-02 SMALL FIBER POLYNEUROPATHY AS A THERAPEUTIC TARGET FOR PATIENTS WITH INTERSTITIAL CYSTITIS/BLADDER PAIN SYNDROME

You have accessJournal of UrologyCME1 Apr 2023PD05-02 SMALL FIBER POLYNEUROPATHY AS A THERAPEUTIC TARGET FOR PATIENTS WITH INTERSTITIAL CYSTITIS/BLADDER PAIN SYNDROME Wyatt Whitman, Maxwell Sandberg, Dylan Wolff, Raymond Xu, Tyler Overholt, Robert Evans, Catherine Matthews, Gopal Badlani, and Stephen Walker Wyatt WhitmanWyatt Whitman More articles by this author , Maxwell SandbergMaxwell Sandberg More articles by this author , Dylan WolffDylan Wolff More articles by this author , Raymond XuRaymond Xu More articles by this author , Tyler OverholtTyler Overholt More articles by this author , Robert EvansRobert Evans More articles by this author , Catherine MatthewsCatherine Matthews More articles by this author , Gopal BadlaniGopal Badlani More articles by this author , and Stephen WalkerStephen Walker More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003229.02AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: In addition to a variety of co-occurring urological and non-urological symptoms and syndromes, we have found that ∼30% of patients with a diagnosis of interstitial cystitis/bladder pain syndrome (IC/BPS) also have small fiber polyneuropathy (SFPN). The objective of this study was to determine the association between SFPN and co-occurring symptoms and syndromes in IC/BPS patients. METHODS: Skin biopsies were taken from the distal calf of IC/BPS patients who were undergoing therapeutic hydrodistension (HOD). SFPN status (+ or -) was determined by counting intraepidermal nerve fibers (IENF) in a stained section from the biopsy and comparing the IENF density to normative reference values. Patient characteristics such as anesthetic bladder capacity (BC), Hunner lesion (HL) status, and glomerulations were determined at the time of hydrodistension under direct cystoscopy. Patient demographics, co-occurring medical conditions, and symptomatology was obtained via patient reports and review of medical records. To test for an association of SFPN+ with demographic and clinical characteristics, an optimized logistic regression model was created using variables with p<0.1 on univariable analysis and/or those with an established clinical relevance. Standard logistic regression diagnostics were utilized to ensure the model fit to the data RESULTS: Between October 2019 and April 2022 153 participants were enrolled (134F;19M). Mean age was 50.32 (±15.32). Overall, one third (50/153) were SFPN+. There was a statistically significant difference in the adjusted odds ratios (OR, [95% CI]) between the SFPN+ and SFPN- groups for chronic fatigue syndrome (3.054, [1.22, 7.68]) and diabetes mellitus (4.185, [1.471, 11.90]). CONCLUSIONS: SFPN is common in patients with IC/BPS and is significantly associated with concomitant diagnoses of chronic fatigue syndrome and diabetes mellitus. These findings suggest that for a large subset of IC/BPS patients that have a systemic pain disorder, SFPN may provide an important new therapeutic target. Source of Funding: R01 DK124599 © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e148 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Wyatt Whitman More articles by this author Maxwell Sandberg More articles by this author Dylan Wolff More articles by this author Raymond Xu More articles by this author Tyler Overholt More articles by this author Robert Evans More articles by this author Catherine Matthews More articles by this author Gopal Badlani More articles by this author Stephen Walker More articles by this author Expand All Advertisement PDF downloadLoading ...

Intraepidermal Nerve Fiber Density In Disease: A Scoping Review

Intraepidermal Nerve Fiber Density In Disease: A Scoping Review

The evaluation of small fibers in multiple sclerosis

Dysesthetic or ongoing extremity pain is a common symptom in all multiple sclerosis (MS) types. Although the pathology of the disease is the demyelination of central neurons, the patients may also complain of neuropathic pain in distal extremities that is generally related to A-delta and C fiber dysfunction. It is not known whether thinly myelinated and unmyelinated fibers are affected in MS patients. We aim to investigate the small fiber loss and its length dependency. We evaluated the skin biopsy taken from proximal and distal leg of MS patients with neuropathic pain. Six patients with primary progressive MS (PPMS), seven with relapsing-remitting MS (RRMS), seven with secondary progressive MS (SPMS) and as a control group ten age and sex-matched healthy controls were included. Neurological examination, electrophysiological evaluation and DN4 questionnaire were performed. Subsequently, skin punch biopsy from 10 cm above the lateral malleolus and proximal thigh were done. The biopsy samples were stained with PGP9.5 antibody and intraepidermal nerve fiber density (IENFD) was determined. The mean proximal IENFD was 8.58±3.58 fibers/mm among MS patients and 14.72±2.89 fiber/mm among healthy controls (p=0.001). However, the mean distal IENFD did not differ between MS patients and healthy controls (9.26±3.24 and 9.75±1.6 fiber/mm respectively. Although proximal and distal IENFD tends to be lower in MS patients with neuropathic pain, there was no statistically significant difference between MS patients with and without neuropathic pain CONCLUSION: Although MS is a demyelinating disease, unmyelinated fibers can also be affected. Our findings suggest non-length dependent small fiber neuropathy in MS patients.

The effect of surgical weight loss on diabetes complications in individuals with class II/III obesity.

The aim of this study was to determine the effect of bariatric surgery on diabetes complications in individuals with class II/III obesity (BMI > 35 kg/m2). We performed a prospective cohort study of participants with obesity who underwent bariatric surgery. At baseline and 2 years following surgery, participants underwent metabolic phenotyping and diabetes complication assessments. The primary outcomes for peripheral neuropathy (PN) were a change in intra-epidermal nerve fibre density (IENFD, units = fibres/mm) at the distal leg and proximal thigh, the primary outcome for cardiovascular autonomic neuropathy (CAN) was a change in the expiration/inspiration (E/I) ratio, and the primary outcome for retinopathy was a change in the mean deviation on frequency doubling technology testing. Among 127 baseline participants, 79 completed in-person follow-up (age 46.0 ± 11.3 years [mean ± SD], 73.4% female). Participants lost a mean of 31.0 kg (SD 18.4), and all metabolic risk factors improved except for BP and total cholesterol. Following bariatric surgery, one of the primary PN outcomes improved (IENFD proximal thigh, +3.4 ± 7.8, p<0.01), and CAN (E/I ratio -0.01 ± 0.1, p=0.89) and retinopathy (deviation -0.2 ± 3.0, p=0.52) were stable. Linear regression revealed that a greater reduction in fasting glucose was associated with improvements in retinopathy (mean deviation point estimate -0.7, 95% CI -1.3, -0.1). Bariatric surgery may be an effective approach to reverse PN in individuals with obesity. The observed stability of CAN and retinopathy may be an improvement compared with the natural progression of these conditions; however, controlled trials are needed.

A dual role of microbiota type 17 immunity in tissue repair and pain.

In this commentary, we discuss the findings of Enamorado etal. who have, for the first time, demonstrated that immunity to the microbiota enhances repair of cutaneous sensory nerves and epithelial tissues following skin injury. Commensal-specific IL-17 producing CD4+ T helper cells have direct contact with injured sensory neurons, inducing multiple epithelial and neuronal repair genes. We speculate that an altered balance of T cell populations in the skin of people with chronic neuropathic pain may contribute to a reduction in neuronal repair and the consequent decease in intraepidermal nerve fibre density and persistent pain.

Co-culture of iNeurons with primary human skin cells provides a reliable model to examine intercellular communication.

The skin is a sensory organ, densely innervated with various types of sensory nerve endings, capable of discriminating touch, environmental sensations, proprioception, and physical affection. Neurons communication with skin cells confer to the tissue the ability to undergo adaptive modifications during response to environmental changes or wound healing after injury. Thought for a long time to be dedicated to the central nervous system, the glutamatergic neuromodulation is increasingly described in peripheral tissues. Glutamate receptors and transporters have been identified in the skin. There is a strong interest in understanding the communication between keratinocytes and neurons, as the close contacts with intra-epidermal nerve fibers is a favorable site for efficient communication. To date, various coculture models have been described. However, these models were based on non-human or immortalized cell line. Even the use of induced pluripotent stem cells (iPSCs) is posing limitations because of epigenetic variations during the reprogramming process. In this study, we performed small molecule-driven direct conversion of human skin primary fibroblasts into induced neurons (iNeurons). The resulting iNeurons were mature, showed pan-neuronal markers, and exhibited a glutamatergic subtype and C-type fibers characteristics. Autologous coculture of iNeurons with human primary keratinocytes, fibroblasts, and melanocytes was performed and remained healthy for many days, making possible to study the establishment of intercellular interactions. Here, we report that iNeurons and primary skin cells established contacts, with neurite ensheathment by keratinocytes, and demonstrated that iNeurons cocultured with primary skin cells provide a reliable model to examine intercellular communication.

Peripheral sensory function in non-freezing cold injury patients and matched controls.

What is the central question of this study? Is peripheral sensory function impaired in the chronic phase of non-freezing cold injury (NFCI)? What is the main finding and its importance? Warm and mechanical detection thresholds are elevated and intraepidermal nerve fibre density is reduced in individuals with NFCI in their feet when compared to matched controls. This indicates impaired sensory function in individuals with NFCI. Interindividual variation was observed in all groups, and therefore a diagnostic cut-off for NFCI has yet to be established. Longitudinal studies are required to follow NFCI progression from formation to resolution ABSTRACT: The aim of this study was to compare peripheral sensory neural function of individuals with non-freezing cold injury (NFCI) with matched controls (without NFCI) with either similar (COLD) or minimal previous cold exposure (CON). Thirteen individuals with chronic NFCI in their feet were matched with the control groups for sex, age, race, fitness, body mass index and foot volume. All undertook quantitative sensory testing (QST) on the foot. Intraepidermal nerve fibre density (IENFD) was assessed 10cm above the lateral malleolus in nine NFCI and 12 COLD participants. Warm detection threshold was higher at the great toe in NFCI than COLD (NFCI 45.93 (4.71)°C vs. COLD 43.44 (2.72)°C, P=0.046), but was non-significantly different from CON (CON 43.92 (5.01)°C, P=0.295). Mechanical detection threshold on the dorsum of the foot was higher in NFCI (23.61 (33.59) mN) than in CON (3.83 (3.69) mN, P=0.003), but was non-significantly different from COLD (10.49 (5.76) mN, P>0.999). Remaining QST measures did not differ significantly between groups. IENFD was lower in NFCI than COLD (NFCI 8.47 (2.36) fibre/mm2 vs. COLD 11.93 (4.04) fibre/mm2 , P=0.020). Elevated warm and mechanical detection thresholds may indicate hyposensitivity to sensory stimuli in the injured foot for individuals with NFCI and may be due to reduced innervation given the reduction in IENFD. Longitudinal studies are required to identify the progression of sensory neuropathy from the formation of injury to its resolution, with appropriate control groups employed.

Critical Pronociceptive Role of Family 2 Voltage-Gated Calcium Channels in a Novel Mouse Model of HIV-Associated Sensory Neuropathy.

Some people living with HIV present painful sensory neuropathy (HIV-SN) that is pharmacoresistant, sex-associated, and a major source of morbidity. Since the specific mechanisms underlying HIV-SN are not well understood, the aim of our study was to characterize a novel model of painful HIV-SN by combining the HIV-1 gp120 protein and the antiretroviral stavudine (d4T) in mice and to investigate the pronociceptive role of the family 2 voltage-gated calcium channel (VGCC) α1 subunit (Cav2.X channels) in such a model. HIV-SN was induced in male and female C57BL/6 mice by administration of gp120 and/or d4T and detected by a battery of behavior tests and by immunohistochemistry. The role of Cav2.X channels was assessed by the treatment with selective blockers and agonists as well as by mRNA detection. Repeated administration with gp120 and/or d4T produced long-lasting touch-evoked painful-like behaviors (starting at 6days, reaching a maximum on day 13, and lasting up to 28days after treatment started), with a greater intensity in female mice treated with the combination of gp120 + d4T. Moreover, gp120 + d4T treatment reduced the intraepidermal nerve fibers and well-being of female mice, without altering other behaviors. Mechanistically, gp120 + d4T treatment induced Cav2.1, 2.2, and 2.3 transcriptional increases in the dorsal root ganglion and the Cav2.X agonist-induced nociception. Accordingly, intrathecal selective Cav2.2 blockade presented longer and better efficacy in reversing the hyperalgesia induced by gp120 + d4T treatment compared with Cav2.1 or Cav2.3, but also presented the worst safety (inducing side effects at effective doses). We conclude that the family 2 calcium channels (Cav2.X) exert a critical pronociceptive role in a novel mouse model of HIV-SN.

Assessing Corneal Confocal Microscopy and Other Small Fiber Measures in Diabetic Polyneuropathy.

Damage to small nerve fibers is common in diabetic polyneuropathy (DPN), and the diagnosis of DPN relies on subjective symptoms and signs in a combination with objective confirmatory tests, typically electrophysiology or intraepidermal nerve fiber density (IENFD) from skin biopsy. Corneal confocal microscopy (CCM) has been introduced as a tool to detect DPN. However, it is unclear if CCM can reliably be used to diagnose DPN and how the technique compares with other commonly used measures of small fiber damage, such as IENFD, cold detection threshold (CDT), and warm detection threshold (WDT). Therefore, we assessed and compared the use of CCM, IENFD, CDT, and WDT in the diagnosis of DPN in patients with type 2 diabetes. In this cohort study, the participants underwent detailed neurologic examination, electrophysiology, quantification of IENFD, CCM, and quantitative sensory testing. Definition of DPN was made in accordance with the Toronto criteria for diabetic neuropathy (without relying on IENFD and thermal thresholds). A total of 214 patients with at least probable DPN, 63 patients without DPN, and 97 controls without diabetes were included. Patients with DPN had lower CCM measures (corneal nerve fiber length [CNFL], nerve fiber density, and branch density), IENFD, CDT, and WDT compared with patients without DPN (p ≤ 0.001, <0.001, 0.002, p < 0.001, p = 0.003, and <0.005, respectively), whereas there was no difference between controls and patients with diabetes without DPN. All 3 CCM measures showed a very low diagnostic sensitivity with CNFL showing the highest (14.4% [95% CI 9.8-18.4]) and a specificity of 95.7% (88.0-99.1). In comparison, the sensitivity of abnormal CDT and/or WDT was 30.5% (24.4-37.0) with a specificity of 84.9% (74.6-92.2). The sensitivity of abnormal IENFD was highest among all measures with a value of 51.1% (43.7-58.5) and a specificity of 90% (79.5-96.2). CCM measures did not correlate with IENFD, CDT/WDT, or neuropathy severity in the group of patients with DPN. CCM measures showed the lowest sensitivity compared with other small fiber measures in the diagnosis of DPN. This indicates that CCM is not a sensitive method to detect DPN in recently diagnosed type 2 diabetes. This study provides Class III evidence that CCM measures aid in the detection of DPN in recently diagnosed type 2 diabetics but with a low sensitivity when compared with other small fiber measures.

Cutaneous α-Synuclein Signatures in Patients With Multiple System Atrophy and Parkinson Disease.

Multiple system atrophy (MSA) is a progressive neurodegenerative disorder caused by the abnormal accumulation of α-synuclein in the nervous system. Clinical features include autonomic and motor dysfunction, which overlap with those of Parkinson disease (PD), particularly at early disease stages. There is an unmet need for accurate diagnostic and prognostic biomarkers for MSA and, specifically, a critical need to distinguish MSA from other synucleinopathies, particularly PD. The purpose of the study was to develop a unique cutaneous pathologic signature of phosphorylated α-synuclein that could distinguish patients with MSA from patients with PD and healthy controls. We studied 31 patients with MSA and 54 patients with PD diagnosed according to current clinical consensus criteria. We also included 24 matched controls. All participants underwent neurologic examinations, autonomic testing, and skin biopsies at 3 locations. The density of intraepidermal, sudomotor, and pilomotor nerve fibers was measured. The deposition of phosphorylated α-synuclein was quantified. Results were compared with clinical rating assessments and autonomic function test results. Patients with PD had reduced nerve fiber densities compared with patients with MSA (p < 0.05, all fiber types). All patients with MSA and 51/54 with PD had evidence of phosphorylated α-synuclein in at least one skin biopsy. No phosphorylated α-synuclein was detected in controls. Patients with MSA had greater phosphorylated α-synuclein deposition (p < 0.0001) and more widespread peripheral distribution (p < 0.0001) than patients with PD. These results provided >90% sensitivity and specificity in distinguishing between the 2 disorders. α-synuclein is present in the peripheral autonomic nerves of patients with MSA and when combined with synuclein distribution accurately distinguishes MSA from PD. This study provides Class II evidence that measurement of phosphorylated α-synuclein in skin biopsies can differentiate patients with MSA from those with PD.

Corneal Sub-Basal Nerve Plexus in Non-Diabetic Small Fiber Polyneuropathies and the Diagnostic Role of In Vivo Corneal Confocal Microscopy.

In vivo corneal confocal microscopy (IVCM) allows the immediate analysis of the corneal nerve quantity and morphology. This method became, an indispensable tool for the tropism examination, as it evaluates the small fiber plexus in the cornea. The IVCM provides us with direct information on the health of the sub-basal nerve plexus and indirectly on the peripheral nerve status. It is an important tool used to investigate peripheral polyneuropathies. Small-fiber neuropathy (SFN) is a group of neurological disorders characterized by neuropathic pain symptoms and autonomic complaints due to the selective involvement of thinly myelinated Aδ-fibers and unmyelinated C-fibers. Accurate diagnosis of SFN is important as it provides a basis for etiological work-up and treatment decisions. The diagnosis of SFN is sometimes challenging as the clinical picture can be difficult to interpret and standard electromyography is normal. In cases of suspected SFN, measurement of intraepidermal nerve fiber density through a skin biopsy and/or analysis of quantitative sensory testing can enable diagnosis. The purpose of the present review is to summarize the current knowledge about corneal nerves in different SFN. Specifically, we explore the correlation between nerve density and morphology and type of SFN, disease duration, and follow-up. We will discuss the relationship between cataracts and refractive surgery and iatrogenic dry eye disease. Furthermore, these new paradigms in SFN present an opportunity for neurologists and clinical specialists in the diagnosis and monitoring the peripheral small fiber polyneuropathies.