Search Results (20)

Complete or partial loss of smell (anosmia), sometimes in association with distorted olfactory perceptions (parosmia), is a common neurological symptom affecting nearly 60% of patients suffering from post-acute neurological sequelae of COronaVIrus Disease of 2019 (COVID-19) syndrome, called long COVID. Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2) may gain access from the nasal cavity to the brain (neurotropism), and the olfactory route has been proposed as a peripheral site of virus entry. COVID-19 is a risk factor for developing Alzheimer’s Disease (AD), an age-dependent and progressive neurodegenerative disorder characterized in affected patients by early olfaction dysfunction that precedes signs of cognitive decline associated with neurodegeneration in vulnerable brain regions of their limbic system. Here, we summarize the recent literature data supporting the causal correlation between the persistent olfactory deterioration following SARS-CoV-2 infection and the long-delayed manifestation of AD-like memory impairment. SARS-CoV-2 infection of the olfactory neuroepithelium is likely to trigger a pattern of detrimental events that, directly and/or indirectly, affect the anatomically interconnected hippocampal and cortical areas, thus resulting in tardive clinical dementia. We also delineate future advancement on pharmacological and rehabilitative treatments to improve the olfactory dysfunction in patients recovering even from the acute/mild phase of COVID-19. Collectively, the present review aims at highlighting the physiopathological nexus between COVID-19 anosmia and post-pandemic mental health to favor the development of best-targeted and more effective therapeutic strategies in the fight against the long-term neurological complications associated with SARS-CoV-2 infection. Full article

Olfactory impairment is one of the most common diseases of the sense organs, and it is closely related to quality life. Although the molecular mechanism of olfaction was recently brought to light, the pathophysiology and effective treatments for olfactory dysfunction still remain challenging. Olfactory impairment can be caused by the degeneration of olfactory receptor neurons in the nose and also by the degeneration of the olfactory bulb of the olfactory cortex. Several studies have shown that stem cells promote the regeneration of the olfactory neuroepithelium after permanent damage in anosmic mice. Transplanted adipose stem cells differentiated into olfactory receptor neurons and endothelial cells. Recently, cell-free approaches using stem cell-derived secretome and extracellular vesicles (EVs) have emerged as a safer, more controllable alternative. These vesicles contain biologically active cargo such as neurotrophins, cytokines, and microRNAs that promote neurogenesis and modulate inflammation. Although direct application in anosmia models remains limited, findings from related neural injury models suggest that secretome- and EV-based therapies may achieve comparable regenerative efficacy to stem cell transplantation. This review summarizes current evidence on the regenerative capacity of stem cells and their secretome or EVs as therapeutic strategies for olfactory epithelium regeneration. Full article

Olfactory neuroblastoma (ONB) is an uncommon neuroendocrine malignancy arising from the olfactory neuroepithelium. ONB frequently presents with nonspecific sinonasal complaints, including nasal obstruction and epistaxis, and diagnosis can be obtained through a combination of physical examination, nasal endoscopy, and computed tomography and magnetic resonance imaging. Endoscopic resection with negative margins, with or without craniotomy, as necessary, is the standard of care for definitive treatment of ONB. Regional metastasis to the neck is often detected at presentation or may occur in a delayed fashion and should be addressed through elective neck dissection or radiation. Adjuvant radiotherapy should be considered, particularly in the case of high grade or tumor stage, as well as positive surgical margins. Systemic therapy is an area of active investigation in both the neoadjuvant and adjuvant setting, with many advocating in favor of induction chemotherapy for significant orbital or intracranial involvement prior to surgical resection. Various targeted immunotherapies are currently being studied for the treatment of recurrent or metastatic ONB. Prolonged locoregional and distant surveillance are indicated following definitive treatment, given the tendency for delayed recurrence and metastasis. Full article

Idiopathic intellectual disability (IID) encompasses the cases of intellectual disability (ID) without a known cause and represents approximately 50% of all cases. Neural progenitor cells (NPCs) from the olfactory neuroepithelium (NEO) contain the same information as the cells found in the brain, but they are more accessible. Some miRNAs have been identified and associated with ID of known etiology. However, in idiopathic ID, the effect of miRNAs is poorly understood. The aim of this study was to determine the miRNAs regulating the expression of mRNAs that may be involved in development of IID. Expression profiles were obtained using NPC–NEO cells from IID patients and healthy controls by microarray. A total of 796 miRNAs and 28,869 mRNAs were analyzed. Several miRNAs were overexpressed in the IID patients compared to controls. miR-25 had the greatest expression. In silico analysis showed that ROBO2 was the target for miR-25, with the highest specificity and being the most down-regulated. In vitro assay showed an increase of miR-25 expression induced a decrease in ROBO2 expression. In neurodevelopment, ROBO2 plays a crucial role in episodic learning and memory, so its down-regulation, caused by miR-25, could have a fundamental role in the intellectual disability that, until now, has been considered idiopathic. Full article

Traumatic brain injury (TBI) is defined as an injury to the brain by external forces which can lead to cellular damage and the disruption of normal central nervous system functions. The recently approved blood-based biomarkers GFAP and UCH-L1 can only detect injuries which are detectable on CT, and are not sensitive enough to diagnose milder injuries or concussion. Exosomes are small microvesicles which are released from the cell as a part of extracellular communication in normal as well as diseased states. The objective of this study was to identify the messenger RNA content of the exosomes released by injured neurons to identify new potential blood-based biomarkers for TBI. Human severe traumatic brain injury samples were used for this study. RNA was isolated from neuronal exosomes and total transcriptomic sequencing was performed. RNA sequencing data from neuronal exosomes isolated from serum showed mRNA transcripts of several neuronal genes. In particular, mRNAs of several olfactory receptor genes were present at elevated concentrations in the neuronal exosomes. Some of these genes were OR10A6, OR14A2, OR6F1, OR1B1, and OR1L1. RNA sequencing data from exosomes isolated from CSF showed a similar elevation of these olfactory receptors. We further validated the expression of these samples in serum samples of mild TBI patients, and a similar up-regulation of these olfactory receptors was observed. The data from these experiments suggest that damage to the neurons in the olfactory neuroepithelium as well as in the brain following a TBI may cause the release of mRNA from these receptors in the exosomes. Hence, olfactory receptors can be further explored as biomarkers for the diagnosis of TBI. Full article

Alzheimer’s disease (AD), as the main cause of dementia, affects millions of people around the world, whose diagnosis is based mainly on clinical criteria. Unfortunately, the diagnosis is obtained very late, when the neurodegenerative damage is significant for most patients. Therefore, the exhaustive study of biomarkers is indispensable for diagnostic, prognostic, and even follow-up support. AD is a multifactorial disease, and knowing its underlying pathological mechanisms is crucial to propose new and valuable biomarkers. In this review, we summarize some of the main biomarkers described in AD, which have been evaluated mainly by imaging studies in cerebrospinal fluid and blood samples. Furthermore, we describe and propose neuronal precursors derived from the olfactory neuroepithelium as a potential resource to evaluate some of the widely known biomarkers of AD and to gear toward searching for new biomarkers. These neuronal lineage cells, which can be obtained directly from patients through a non-invasive and outpatient procedure, display several characteristics that validate them as a surrogate model to study the central nervous system, allowing the analysis of AD pathophysiological processes. Moreover, the ease of obtaining and harvesting endows them as an accessible and powerful resource to evaluate biomarkers in clinical practice. Full article

The olfactory neuroepithelium (OE) is one of the few neuronal tissues where environmental pathogens can gain direct access. Despite this vulnerable arrangement, little is known about the protective mechanisms in the OE to prevent viral infection and its antiviral responses. We systematically investigated acute responses in the olfactory mucosa upon exposure to vesicular stomatitis virus (VSV) via RNA-seq. VSVs were nasally inoculated into C57BL/6 mice. Olfactory mucosae were dissected for gene expression analysis at different time points after viral inoculation. Interferon functions were determined by comparing the viral load in interferon receptor knockout (Ifnar1^−/− and Ifnlr1^−/−) with wildtype OE. Antiviral responses were observed as early as 24 h after viral exposure in the olfactory mucosa. The rapidly upregulated transcripts observed included specific type I as well as type III interferons (Ifn) and interferon-stimulated genes. Genetic analyses demonstrated that both type I and type III IFN signaling are required for the suppression of viral replication in the olfactory mucosa. Exogenous IFN application effectively blocks viral replication in the OE. These findings reveal that the OE possesses an innate ability to suppress viral infection. Type I and type III IFNs have prominent roles in OE antiviral functions. Full article

The study of neurodevelopmental molecular mechanisms in schizophrenia requires the development of adequate biological models such as patient-derived cells and their derivatives. We previously utilized cell lines with neural progenitor properties (CNON) derived from the superior or middle turbinates of patients with schizophrenia and control groups to study schizophrenia-specific gene expression. In this study, we analyzed single-cell RNA seq data from two CNON cell lines (one derived from an individual with schizophrenia (SCZ) and the other from a control group) and two biopsy samples from the middle turbinate (MT) (also from an individual with SCZ and a control). We compared our data with previously published data regarding the olfactory neuroepithelium and demonstrated that CNON originated from a single cell type present both in middle turbinate and the olfactory neuroepithelium and expressed in multiple markers of mesenchymal cells. To define the relatedness of CNON to the developing human brain, we also compared CNON datasets with scRNA-seq data derived from an embryonic brain and found that the expression profile of the CNON closely matched the expression profile one of the cell types in the embryonic brain. Finally, we evaluated the differences between SCZ and control samples to assess the utility and potential benefits of using CNON single-cell RNA seq to study the etiology of schizophrenia. Full article

During COVID-19 pandemic, clinicians have had to deal with an ever-increasing number of cases of olfactory disturbances after SARS-CoV-2 infections and in some people this problem persisted for long time after negativization from virus. This a prospective randomized controlled trial aims at evaluating the efficacy of ultramicronized palmitoylethanolamide (PEA) and Luteolin (LUT) (umPEA-LUT) and olfactory training (OT) compared to OT alone for the treatment of smell disorders in Italian post-COVID population. We included patients with smell loss and parosmia who were randomized and assigned to Group 1 (intervention group; daily treatment with umPEA-LUT oral supplement and OT) or Group 2 (control group; daily treatment with placebo and OT). All subjects were treated for 90 consecutive days. The Sniffin’ Sticks identification test was used to assess the olfactory functions at the baseline (T0) and the end of the treatment (T1). Patients were queried regarding any perception of altered olfaction (parosmia) or aversive smell, such as cacosmia, gasoline-type smell, or otherwise at the same observational points. This study confirmed the efficacy of combination of umPEA-LUT and olfactory training as treatment of quantitative smell alteration COVID-19 related, but the efficacy of the supplement for parosmia was limited. UmpEA-LUT is useful for the treatment of brain neuro-inflammation (origin of quantity smell disorders) but has limited/no effect on peripheral damage (olfactory nerve, neuro-epithelium) that is responsible of quality disorders. Full article

Olfactory capacity declines with aging, but increasing evidence shows that smell dysfunction is one of the early signs of prodromal neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease. The study of olfactory ability and its role in neurodegenerative diseases arouses much interest in the scientific community. In neurology, olfactory impairment is a potential early marker for the onset of neurodegenerative diseases, but the underlying mechanism is poorly understood. The loss of smell is considered a clinical sign of early-stage disease and a marker of the disease’s progression and cognitive impairment. Highlighting the importance of biological bases of smell and molecular pathways could be fundamental to improve neuroprotective and therapeutic strategies. We focused on the review articles and meta-analyses on olfactory and cognitive impairment. We depicted the neurobiology of olfaction and the most common olfactory tests in neurodegenerative diseases. In addition, we underlined the close relationship between the olfactory and cognitive deficit due to nasal neuroepithelium, which is a direct extension of the CNS in communication with the external environment. Neurons, Nose, and Neurodegenerative diseases highlights the role of olfactory dysfunction as a clinical marker for early stages of neurodegenerative diseases when it is associated with molecular, clinical, and neuropathological correlations. Full article

Loss of the sense of smell (anosmia) has been included as a COVID-19 symptom by the World Health Organization. The majority of patients recover the sense of smell within a few weeks postinfection (short-term anosmia), while others report persistent anosmia. Several studies have investigated the mechanisms leading to anosmia in COVID-19; however, the evidence is scattered, and the mechanisms remain poorly understood. Based on a comprehensive review of the literature, we aim here to evaluate the current knowledge and uncertainties regarding the mechanisms leading to short-term anosmia following SARS-CoV-2 infection. We applied an adverse outcome pathway (AOP) framework, well established in toxicology, to propose a sequence of measurable key events (KEs) leading to short-term anosmia in COVID-19. Those KEs are (1) SARS-CoV-2 Spike proteins binding to ACE-2 expressed by the sustentacular (SUS) cells in the olfactory epithelium (OE); (2) viral entry into SUS cells; (3) viral replication in the SUS cells; (4) SUS cell death; (5) damage to the olfactory sensory neurons and the olfactory epithelium (OE). This AOP-aligned approach allows for the identification of gaps where more research should be conducted and where therapeutic intervention could act. Finally, this AOP gives a frame to explain several disease features and can be linked to specific factors that lead to interindividual differences in response to SARS-CoV-2 infection. Full article

Animal models recapitulating COVID-19 are critical to enhance our understanding of SARS-CoV-2 pathogenesis. Intranasally inoculated transgenic mice expressing human angiotensin-converting enzyme 2 under the cytokeratin 18 promoter (K18-hACE2) represent a lethal model of SARS-CoV-2 infection. We evaluated the clinical and virological dynamics of SARS-CoV-2 using two intranasal doses (10⁴ and 10⁶ PFUs), with a detailed spatiotemporal pathologic analysis of the 10⁶ dose cohort. Despite generally mild-to-moderate pneumonia, clinical decline resulting in euthanasia or death was commonly associated with hypothermia and viral neurodissemination independent of inoculation dose. Neuroinvasion was first observed at 4 days post-infection, initially restricted to the olfactory bulb suggesting axonal transport via the olfactory neuroepithelium as the earliest portal of entry. Absence of viremia suggests neuroinvasion occurs independently of transport across the blood-brain barrier. SARS-CoV-2 tropism was neither restricted to ACE2-expressing cells (e.g., AT1 pneumocytes), nor inclusive of some ACE2-positive cell lineages (e.g., bronchiolar epithelium and brain vasculature). Absence of detectable ACE2 protein expression in neurons but overexpression in neuroepithelium suggest this as the most likely portal of neuroinvasion, with subsequent ACE2 independent lethal neurodissemination. A paucity of epidemiological data and contradicting evidence for neuroinvasion and neurodissemination in humans call into question the translational relevance of this model. Full article

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative pathogen of coronavirus disease 2019 (COVID-19). It is known as a respiratory virus, but SARS-CoV-2 appears equally, or even more, infectious for the olfactory epithelium (OE) than for the respiratory epithelium in the nasal cavity. In light of the small area of the OE relative to the respiratory epithelium, the high prevalence of olfactory dysfunctions (ODs) in COVID-19 has been bewildering and has attracted much attention. This review aims to first examine the cytological and molecular biological characteristics of the OE, especially the microvillous apical surfaces of sustentacular cells and the abundant SARS-CoV-2 receptor molecules thereof, that may underlie the high susceptibility of this neuroepithelium to SARS-CoV-2 infection and damages. The possibility of SARS-CoV-2 neurotropism, or the lack of it, is then analyzed with regard to the expression of the receptor (angiotensin-converting enzyme 2) or priming protease (transmembrane serine protease 2), and cellular targets of infection. Neuropathology of COVID-19 in the OE, olfactory bulb, and other related neural structures are also reviewed. Toward the end, we present our perspectives regarding possible mechanisms of SARS-CoV-2 neuropathogenesis and ODs, in the absence of substantial viral infection of neurons. Plausible causes for persistent ODs in some COVID-19 convalescents are also examined. Full article

A major problem in psychiatric research is a deficit of relevant cell material of neuronal origin, especially in large quantities from living individuals. One of the promising options is cells from the olfactory neuroepithelium, which contains neuronal progenitors that ensure the regeneration of olfactory receptors. These cells are easy to obtain with nasal biopsies and it is possible to grow and cultivate them in vitro. In this work, we used RNAseq expression profiling and immunofluorescence microscopy to characterise neurospheres-derived cells (NDC), that simply and reliably grow from neurospheres (NS) obtained from nasal biopsies. We utilized differential expression analysis to explore the molecular changes that occur during transition from NS to NDC. We found that processes associated with neuronal and vascular cells are downregulated in NDC. A comparison with public transcriptomes revealed a depletion of neuronal and glial components in NDC. We also discovered that NDC have several metabolic features specific to neuronal progenitors treated with the fungicide maneb. Thus, while NDC retain some neuronal/glial identity, additional protocol alterations are needed to use NDC for mass sample collection in psychiatric research. Full article

A close epidemiological link has been reported between cannabis use and schizophrenia (SCZ). However, biochemical markers in living humans related to the impact of cannabis in this disease are still missing. Olfactory neuroepithelium (ON) cells express neural features and offer a unique advantage to study biomarkers of psychiatric diseases. The aim of our study was to find exclusively deregulated proteins in ON cells of SCZ patients with and without a history of cannabis use. Thus, we compared the proteomic profiles of SCZ non-cannabis users (SCZ/nc) and SCZ cannabis users (SCZ/c) with control subjects non-cannabis users (C/nc) and control cannabis users (C/c). The results revealed that the main cascades affected in SCZ/nc were cell cycle, DNA replication, signal transduction and protein localization. Conversely, cannabis use in SCZ patients induced specific alterations in metabolism of RNA and metabolism of proteins. The levels of targeted proteins in each population were then correlated with cognitive performance and clinical scores. In SCZ/c, the expression levels of 2 proteins involved in the metabolism of RNA (MTREX and ZNF326) correlated with several cognitive markers and clinical signs. Moreover, use duration of cannabis negatively correlated with ZNF326 expression. These findings indicate that RNA-related proteins might be relevant to understand the influence of cannabis use on SCZ. Full article