Histological reappraisal of IgA nephropathy: the role of glomerular pattern of injury and mesangial complement deposition.

BACKGROUND: There is a clear need to refine the histological assessment in IgA Nephropathy (IgAN). We sought to investigate the clinical significance of the light microscopy (LM) pattern of glomerular injury and of the intensity of mesangial C3 staining in IgAN. METHODS: We conducted a retrospective, observational study that included all patients with biopsy-proven primary IgAN that had at least 12 months of follow-up. The LM pattern of glomerular injury was reevaluated based on a modified HAAS classification. Mesangial C3 deposition by immunofluorescence (IF) staining was scored semi-quantitatively. The study primary composite endpoint was defined as doubling of serum creatinine or ESRD (dialysis, renal transplant or eGFR < 15 ml/min). The secondary study endpoint was eGFR decline per year. RESULTS: This cohort included 214 patients with IgAN (mean age, 41.4 ± 12.6 years), with a mean eGFR and median 24-h proteinuria of 55.2 ± 31.5 ml/min/1.73m2 and 1.5 g/day (IQR:0.8-3.25), respectively. The most frequent LM pattern was the mesangioproliferative (37.4%), followed by the sclerotic (22.5%) and proliferative/necrotizing patterns (21.4%). Regarding the IF findings, mild-moderate and intense mesangial C3 staining was present in 30.6% and 61.1% of patients, respectively. Those with sclerosing and crescentic patterns had the worst renal survival (5-year renal survival of 48.8% and 42.9%) and the highest rate of eGFR change/year (-2.32 ml/min/y and - 2.16 ml/min/y, respectively) compared to those with other glomerular patterns of injury. In addition, those with intense C3 staining reached the composite endpoint more frequently compared to those without intense C3 staining (35.5% vs. 21.4%, p = 0.04). After multivariate adjustment, patients with crescentic and sclerosing patterns had a 3.6-fold and 2.1-fold higher risk for the composite endpoint compared to those with mesangioproliferative pattern, while an intense mesangial C3 deposition being also associated with a worse renal outcome (HR, 3.33; 95%CI, 1.21-9.2). CONCLUSIONS: We have shown that the LM pattern of glomerular injury and the intensity of mesangial C3 deposition might stratify more accurately the renal outcome in patients with IgAN.

Lupus nephritis with cryoglobulinemic glomerulonephritis features: a diagnostic conundrum.

In this clinical case, we report an atypical and unique presentation of systemic lupus erythematosus (SLE) in a 39-year-old female with nephrotic syndrome. The patient exhibited class IV plus V lupus nephritis and extensive immune complex deposition within the intracapillary and arteriolar regions suggestive of cryoglobulinemic glomerulonephritis, despite no detectable circulating cryoglobulins. Electron microscopy revealed cryoglobulin-like deposit distribution in all glomerular examined compartments, namely subendothelial, intramembranous, subepithelial, and mesangial, apparently extending from the capillary hyaline thrombi. The case highlights the possibility of severe renal injury in SLE without circulating cryoglobulins and the diverse kidney manifestations associated with the disease. However, the impact on patient outcome was minimal, as classical treatment (id est National Institute of Health regimen) remained effective.

Switching Rat Resident Macrophages from M1 to M2 Phenotype by Iba1 Silencing Has Analgesic Effects in SNL-Induced Neuropathic Pain.

Resident macrophages from dorsal root ganglia are important for the development of traumatic-induced neuropathic pain. In the first 5-7 days after a traumatic sciatic nerve injury (i.e., spinal nerve ligation (SNL), spared nerve injury (SNI), sciatic nerve transection or sciatic nerve ligation and transection), Ionized binding adapter protein 1 (Iba1) (+) resident macrophages cluster around dorsal root ganglia neurons, possibly contributing to nerve injury-induced hypersensitivity. Since infiltrating macrophages gradually recruited to the lesion site peak at about 7 days, the first few days post-lesion offer a window of opportunity when the contribution of Iba1 (+) resident macrophages to neuropathic pain pathogenesis could be investigated. Iba1 is an actin cross-linking cytoskeleton protein, specifically located only in macrophages and microglia. In this study, we explored the contribution of rat Iba1 (+) macrophages in SNL-induced neuropathic pain by using intra-ganglionic injections of naked Iba1-siRNA, delivered at the time the lesion occurred. The results show that 5 days after Iba1 silencing, Iba1 (+) resident macrophages are switched from an M1 (pro-inflammatory) phenotype to an M2 (anti-inflammatory) phenotype, which was confirmed by a significant decrease of M1 markers (CD32 and CD86), a significant increase of M2 markers (CD163 and Arginase-1), a reduced secretion of pro-inflammatory cytokines (IL-6, TNF-α and IL-1ß) and an increased release of pro-regenerative factors (BDNF, NGF and NT-3) which initiated the regrowth of adult DRG neurites and reduced SNL-induced neuropathic pain. Our data show for the first time, that it is possible to induce macrophages towards an anti-inflammatory phenotype by interacting with their cytoskeleton.

The atomic portrait of SARS-CoV-2 as captured by cryo-electron microscopy.

Transmission electron microscopy has historically been indispensable for virology research, as it offers unique insight into virus function. In the past decade, as cryo-electron microscopy (cryo-EM) has matured and become more accessible, we have been able to peer into the structure of viruses at the atomic level and understand how they interact with the host cell, with drugs or with antibodies. Perhaps, there was no time in recent history where cryo-EM was more needed, as SARS-CoV-2 has spread around the globe, causing millions of deaths and almost unquantifiable economic devastation. In this concise review, we aim to mark the most important contributions of cryo-EM to understanding the structure and function of SARS-CoV-2 proteins, from surface spikes to the virus core and from virus-receptor interactions to antibody binding.

CD36 - A novel molecular target in the neurovascular unit.

CD36 is an integral membrane protein primarily known for its function as a fatty acid transporter, yet also playing other biological roles from lipid metabolism to inflammation modulation. These pleiotropic effects are explained by the existence of multiple different ligands and the extensive distribution in numerous cell types. Moreover, the receptor is related to various pathologies and it may prove to be a good target for prospective therapeutic strategies. In the neurovascular unit (NVU), CD36 is expressed in cells like microglia, microvascular endothelial cells, astrocytes and neurons. In the normal brain, CD36 was proven to be involved in phagocytosis of apoptotic cells, oro-sensory detection of dietary lipids, and fatty acid transport across the blood brain barrier (BBB). CD36 was also acknowledged as a potentially important player in central nervous system (CNS) disorders, such as Alzheimer Disease-associated vascular dysfunction and oxidative stress and the neuroinflammatory response in stroke. Despite continuous efforts, the therapeutic arsenal for such diseases is still scarce and there is an increasing interest in discovering new molecular targets for more specific therapeutic approaches. In this review, we summarize the role of CD36 in the normal function of the NVU and in several CNS disorders, focusing on the dysregulation of the NVU and the potential therapeutic modulation.

IgA nephropathy with serum ANCA positivity: case series and literature review.

The co-occurrence of IgA nephropathy (IgAN) and positive anti-neutrophil cytoplasmic autoantibodies (ANCA) serology is uncommon. In the present case series and literature review, we aimed to clarify the impact of ANCA on pathogenesis, clinical and histopathology presentation, and outcome in IgAN patients. We report four patients with an overlap lesion of IgAN-ANCA positive. Also, we performed a narrative review of all biopsy-proven published case series. Only 1.2% patients had ANCA in our 330-biopsy-proven IgAN cohort. We compared our data with previous reports-6 case series and 3 small retrospective studies-a total of 103 patients. All patients but one had eGFR below 15 mL/min at diagnosis. Besides rapidly decreasing eGFR, all presented with proteinuria around 1.5 g/day and dysmorphic microhematuria, suggesting glomerular inflammation. Systemic symptoms suggestive for ANCA vasculitis were seen in half of our patients, but only one patient had hemorrhagic alveolitis. Patients from our cohort responded to the intensive immunosuppressive regimens used in ANCA-positive vasculitis with renal involvement. However, in the follow-up, one patient had a relapse followed by septic shock related to immunosuppression and one patient started hemodialysis. In the review, we found that IgAN-ANCA -positive patients are characterized by vasculitis-like lesions and clinically by a rapidly progressive decline in kidney function, which was reversed by an aggressive induction immunosuppressive protocol used in ANCA vasculitis. Checking ANCA serology seems useful in patients with rapidly progressive IgAN for therapeutic and prognostic reasons.

Investigating LMNA-Related Dilated Cardiomyopathy Using Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

LMNA-related dilated cardiomyopathy is an inherited heart disease caused by mutations in the LMNA gene encoding for lamin A/C. The disease is characterized by left ventricular enlargement and impaired systolic function associated with conduction defects and ventricular arrhythmias. We hypothesized that LMNA-mutated patients' induced Pluripotent Stem Cell-derived cardiomyocytes (iPSC-CMs) display electrophysiological abnormalities, thus constituting a suitable tool for deciphering the arrhythmogenic mechanisms of the disease, and possibly for developing novel therapeutic modalities. iPSC-CMs were generated from two related patients (father and son) carrying the same E342K mutation in the LMNA gene. Compared to control iPSC-CMs, LMNA-mutated iPSC-CMs exhibited the following electrophysiological abnormalities: (1) decreased spontaneous action potential beat rate and decreased pacemaker current (If) density; (2) prolonged action potential duration and increased L-type Ca2+ current (ICa,L) density; (3) delayed afterdepolarizations (DADs), arrhythmias and increased beat rate variability; (4) DADs, arrhythmias and cessation of spontaneous firing in response to ß-adrenergic stimulation and rapid pacing. Additionally, compared to healthy control, LMNA-mutated iPSC-CMs displayed nuclear morphological irregularities and gene expression alterations. Notably, KB-R7943, a selective inhibitor of the reverse-mode of the Na+/Ca2+ exchanger, blocked the DADs in LMNA-mutated iPSC-CMs. Our findings demonstrate cellular electrophysiological mechanisms underlying the arrhythmias in LMNA-related dilated cardiomyopathy.

Sex and Age-Related Differences in Neuroinflammation and Apoptosis in Balb/c Mice Retina Involve Resolvin D1.

(1) Background: The pro-resolving lipid mediator Resolvin D1 (RvD1) has already shown protective effects in animal models of diabetic retinopathy. This study aimed to investigate the retinal levels of RvD1 in aged (24 months) and younger (3 months) Balb/c mice, along with the activation of macro- and microglia, apoptosis, and neuroinflammation. (2) Methods: Retinas from male and female mice were used for immunohistochemistry, immunofluorescence, transmission electron microscopy, Western blotting, and enzyme-linked immunosorbent assays. (3) Results: Endogenous retinal levels of RvD1 were reduced in aged mice. While RvD1 levels were similar in younger males and females, they were markedly decreased in aged males but less reduced in aged females. Both aged males and females showed a significant increase in retinal microglia activation compared to younger mice, with a more marked reactivity in aged males than in aged females. The same trend was shown by astrocyte activation, neuroinflammation, apoptosis, and nitrosative stress, in line with the microglia and Müller cell hypertrophy evidenced in aged retinas by electron microscopy. (4) Conclusions: Aged mice had sex-related differences in neuroinflammation and apoptosis and low retinal levels of endogenous RvD1.

Successful Treatment of Catastrophic Antiphospholipid Syndrome Using Rituximab: Case Report and Review of the Literature.

BACKGROUND: Kidney involvement is a frequent complication of systemic lupus erythematosus (SLE) and kidney biopsy is essential in differentiating lupus nephritis (LN) from thrombotic microangiopathy (TMA) secondary to antiphospholipid autoantibodies (aPL). Association between antiphospholipid syndrome (APS) and acquired hemophilia due to inhibitors was very rarely described in SLE patients. CASE PRESENTATION: We present the case of a 61-year-old male diagnosed with SLE who acquired deficiency of clotting factor VIII due to circulating inhibitors, admitted for acute kidney injury (AKI), microangiopathic hemolytic anemia, thrombocytopenia, and diplopia. Kidney biopsy showed TMA due to APS, but no signs of LN. Head computed tomography identified low dense areas in the white matter, suggesting small blood vessels' involvement. A diagnosis of probable catastrophic antiphospholipid syndrome (CAPS) was established and treatment with low molecular weight heparin, intravenous methylprednisolone, plasmapheresis, and rituximab was initiated, followed by resolution of AKI, diplopia, and TMA with complete depletion of CD19+B-lymphocytes (CD19+B-Ly) after one month. We further review the current knowledge regarding pathogenesis and management of CAPS in SLE patients. CONCLUSIONS: Targeted therapy was possible after kidney biopsy, improving renal and general prognosis. CD19+B-Ly repopulation preceded biological relapse, so monitoring of CD19+B-Ly may serve as a tool to predict relapses and guide rituximab therapy.

Gene expression profile of adhesion and extracellular matrix molecules during early stages of skeletal muscle regeneration.

Skeletal muscle regeneration implies the coordination of myogenesis with the recruitment of myeloid cells and extracellular matrix (ECM) remodelling. Currently, there are no specific biomarkers to diagnose the severity and prognosis of muscle lesions. In order to investigate the gene expression profile of extracellular matrix and adhesion molecules, as premises of homo- or heterocellular cooperation and milestones for skeletal muscle regeneration, we performed a gene expression analysis for genes involved in cellular cooperation, migration and ECM remodelling in a mouse model of acute crush injury. The results obtained at two early time-points post-injury were compared to a GSE5413 data set from two other trauma models. Third day post-injury, when inflammatory cells invaded, genes associated with cell-matrix interactions and migration were up-regulated. After day 5, as myoblast migration and differentiation started, genes for basement membrane constituents were found down-regulated, whereas genes for ECM molecules, macrophage, myoblast adhesion, and migration receptors were up-regulated. However, the profile and the induction time varied according to the experimental model, with only few genes being constantly up-regulated. Gene up-regulation was higher, delayed and more diverse following more severe trauma. Moreover, one of the most up-regulated genes was periostin, suggestive for severe muscle damage and unfavourable architecture restoration.

Multi-Omics Data Integration in Extracellular Vesicle Biology-Utopia or Future Reality?

Extracellular vesicles (EVs) are membranous structures derived from the endosomal system or generated by plasma membrane shedding. Due to their composition of DNA, RNA, proteins, and lipids, EVs have garnered a lot of attention as an essential mechanism of cell-to-cell communication, with various implications in physiological and pathological processes. EVs are not only a highly heterogeneous population by means of size and biogenesis, but they are also a source of diverse, functionally rich biomolecules. Recent advances in high-throughput processing of biological samples have facilitated the development of databases comprised of characteristic genomic, transcriptomic, proteomic, metabolomic, and lipidomic profiles for EV cargo. Despite the in-depth approach used to map functional molecules in EV-mediated cellular cross-talk, few integrative methods have been applied to analyze the molecular interplay in these targeted delivery systems. New perspectives arise from the field of systems biology, where accounting for heterogeneity may lead to finding patterns in an apparently random pool of data. In this review, we map the biological and methodological causes of heterogeneity in EV multi-omics data and present current applications or possible statistical methods for integrating such data while keeping track of the current bottlenecks in the field.

Age-related ultrastructural changes of the basement membrane in the mouse blood-brain barrier.

The blood-brain barrier (BBB) is essential for a functional neurovascular unit. Most studies focused on the cells forming the BBB, but very few studied the basement membrane (BM) of brain capillaries in ageing. We used transmission electron microscopy and electron tomography to investigate the BM of the BBB in ageing C57BL/6J mice. The thickness of the BM of the BBB from 24-month-old mice was double as compared with that of 6-month-old mice (107 nm vs 56 nm). The aged BBB showed lipid droplets gathering within the BM which further increased its thickness (up to 572 nm) and altered its structure. The lipids appeared to accumulate toward the glial side of the BM. Electron tomography showed that the lipid-rich BM regions are located in small pockets formed by the end-feet of astrocytes. These findings suggest an imbalance of the lipid metabolism and that may precede the structural alteration of the BM. These alterations may favour the accretion of abnormal proteins that lead to neurodegeneration in ageing. These findings warrant further investigation of the BM of brain capillaries and of adjoining cells as potential targets for future therapies.

Unveiling Ga(III) phthalocyanine-a different photosensitizer in neuroblastoma cellular model.

Phthalocyanines (Pc) and their metallated derivatives are strongly considered for photodynamic therapy (PDT) possessing unique properties as possible new photosensitizers (PS). We have used toxicological assessments, real-time monitoring of cellular impedance, and imagistic measurements for assessing the in vitro dark toxicity and PDT efficacy of Ga(III)-Pc in SHSy5Y neuroblastoma cells. We have established the non-toxic concentration range of Ga(III)-Pc, a compound which shows a high intracellular accumulation, with perinuclear distribution in confocal microscopy. By choosing Ga(III)Pc non-toxic dose, we performed in vitro experimental PDT hampering cellular proliferation. Our proposed Ga(III)-Pc could complete a future PS panel for neuroblastoma alternate therapy.

Electrophysiological abnormalities in induced pluripotent stem cell-derived cardiomyocytes generated from Duchenne muscular dystrophy patients.

Duchenne muscular dystrophy (DMD) is an X-linked progressive muscle degenerative disease, caused by mutations in the dystrophin gene and resulting in death because of respiratory or cardiac failure. To investigate the cardiac cellular manifestation of DMD, we generated induced pluripotent stem cells (iPSCs) and iPSC-derived cardiomyocytes (iPSC-CMs) from two DMD patients: a male and female manifesting heterozygous carrier. Dystrophin mRNA and protein expression were analysed by qRT-PCR, RNAseq, Western blot and immunofluorescence staining. For comprehensive electrophysiological analysis, current and voltage clamp were used to record transmembrane action potentials and ion currents, respectively. Microelectrode array was used to record extracellular electrograms. X-inactive specific transcript (XIST) and dystrophin expression analyses revealed that female iPSCs underwent X chromosome reactivation (XCR) or erosion of X chromosome inactivation, which was maintained in female iPSC-CMs displaying mixed X chromosome expression of wild type (WT) and mutated alleles. Both DMD female and male iPSC-CMs presented low spontaneous firing rate, arrhythmias and prolonged action potential duration. DMD female iPSC-CMs displayed increased beat rate variability (BRV). DMD male iPSC-CMs manifested decreased If density, and DMD female and male iPSC-CMs showed increased ICa,L density. Our findings demonstrate cellular mechanisms underlying electrophysiological abnormalities and cardiac arrhythmias in DMD.

Exosomal Expression of CXCR4 Targets Cardioprotective Vesicles to Myocardial Infarction and Improves Outcome after Systemic Administration.

Cell therapy has been evaluated to enhance heart function after injury. Delivered cells mostly act via paracrine mechanisms, including secreted growth factors, cytokines, and vesicles, such as exosomes (Exo). Intramyocardial injection of cardiac-resident progenitor cells (CPC)-derived Exo reduced scarring and improved cardiac function after myocardial infarction in rats. Here, we explore a clinically relevant approach to enhance the homing process to cardiomyocytes (CM), which is crucial for therapeutic efficacy upon systemic delivery of Exo. By overexpressing exosomal CXCR4, we increased the efficacy of plasmatic injection of cardioprotective Exo-CPC by increasing their bioavailability to ischemic hearts. Intravenous injection of ExoCXCR4 significantly reduced infarct size and improved left ventricle ejection fraction at 4 weeks compared to ExoCTRL (p < 0.01). Hemodynamic measurements showed that ExoCXCR4 improved dp/dt min, as compared to ExoCTRL and PBS group. In vitro, ExoCXCR4 was more bioactive than ExoCTRL in preventing CM death. This in vitro effect was independent from SDF-1α, as shown by using AMD3100 as specific CXCR4 antagonist. We showed, for the first time, that systemic administration of Exo derived from CXCR4-overexpressing CPC improves heart function in a rat model of ischemia reperfusion injury These data represent a substantial step toward clinical application of Exo-based therapeutics in cardiovascular disease.

Telocyte's contacts.

Telocytes (TC) are an interstitial cell type located in the connective tissue of many organs of humans and laboratory mammals. By means of homocellular contacts, TC build a scaffold whose meshes integrity and continuity are guaranteed by those contacts having a mechanical function; those contacts acting as sites of intercellular communication allow exchanging information and spreading signals. Heterocellular contacts between TC and a great variety of cell types give origin to mixed networks. TC, by means of all these types of contacts, their interaction with the extracellular matrix and their vicinity to nerve endings, are part of an integrated system playing tissue/organ-specific roles.

Investigating the cardiac pathology of SCO2-mediated hypertrophic cardiomyopathy using patients induced pluripotent stem cell-derived cardiomyocytes.

Mutations in SCO2 are among the most common causes of COX deficiency, resulting in reduced mitochondrial oxidative ATP production capacity, often leading to hypertrophic cardiomyopathy (HCM). To date, none of the recent pertaining reports provide deep understanding of the SCO2 disease pathophysiology. To investigate the cardiac pathology of the disease, we were the first to generate induced pluripotent stem cell (iPSC)-derived cardiomyocytes (iPSC-CMs) from SCO2-mutated patients. For iPSC generation, we reprogrammed skin fibroblasts from two SCO2 patients and healthy controls. The first patient was a compound heterozygote to the common E140K mutation, and the second was homozygote for the less common G193S mutation. iPSC were differentiated into cardiomyocytes through embryoid body (EB) formation. To test the hypothesis that the SCO2 mutation is associated with mitochondrial abnormalities, and intracellular Ca2+ -overload resulting in functional derangements and arrhythmias, we investigated in SCO2-mutated iPSC-CMs (compared to control cardiomyocytes): (i) the ultrastructural changes; (ii) the inotropic responsiveness to ß-adrenergic stimulation, increased [Ca2+ ]o and angiotensin-II (AT-II); and (iii) the Beat Rate Variability (BRV) characteristics. In support of the hypothesis, we found in the mutated iPSC-CMs major ultrastructural abnormalities and markedly attenuated response to the inotropic interventions and caffeine, as well as delayed afterdepolarizations (DADs) and increased BRV, suggesting impaired SR Ca2+ handling due to attenuated SERCA activity caused by ATP shortage. Our novel results show that iPSC-CMs are useful for investigating the pathophysiological mechanisms underlying the SCO2 mutation syndrome.

Reaching out: junctions between cardiac telocytes and cardiac stem cells in culture.

Telocytes (TCs) were previously shown by our group to form a tandem with stem/progenitor cells in cardiac stem cell (CSC) niches, fulfilling various roles in cardiac renewal. Among these, the ability to 'nurse' CSCs in situ, both through direct physical contact (junctions) as well as at a distance, by paracrine signalling or through extracellular vesicles containing mRNA. We employed electron microscopy to identify junctions (such as gap or adherens junctions) in a co-culture of cardiac TCs and CSCs. Gap junctions were observed between TCs, which formed networks, however, not between TCs and CSCs. Instead, we show that TCs and CSCs interact in culture forming heterocellular adherens junctions, as well as non-classical junctions such as puncta adherentia and stromal synapses. The stromal synapse formed between TCs and CSCs (both stromal cells) was frequently associated with the presence of electron-dense nanostructures (on average about 15 nm in length) connecting the two opposing membranes. The average width of the synaptic cleft was 30 nm, whereas the average length of the intercellular contact was 5 µm. Recent studies have shown that stem cells fail to adequately engraft and survive in the hostile environment of the injured myocardium, possibly as a result of the absence of the pro-regenerative components of the secretome (paracrine factors) and/or of neighbouring support cells. Herein, we emphasize the similarities between the junctions described in co-culture and the junctions identified between TCs and CSCs in situ. Reproducing a CSC niche in culture may represent a viable alternative to mono-cellular therapies.

Telocyte dynamics in psoriasis.

The presence of telocytes (TCs) as distinct interstitial cells was previously documented in human dermis. TCs are interstitial cells completely different than dermal fibroblasts. TCs are interconnected in normal dermis in a 3D network and may be involved in skin homeostasis, remodelling, regeneration and repair. The number, distribution and ultrastructure of TCs were recently shown to be affected in systemic scleroderma. Psoriasis is a common inflammatory skin condition (estimated to affect about 0.1-11.8% of population), a keratinization disorder on a genetic background. In psoriasis, the dermis contribution to pathogenesis is frequently eclipsed by remarkable epidermal phenomena. Because of the particular distribution of TCs around blood vessels, we have investigated TCs in the dermis of patients with psoriasis vulgaris using immunohistochemistry (IHC), immunofluorescence (IF), and transmission electron microscopy (TEM). IHC and IF revealed that CD34/PDGFRα-positive TCs are present in human papillary dermis. More TCs were present in the dermis of uninvolved skin and treated skin than in psoriatic dermis. In uninvolved skin, TEM revealed TCs with typical ultrastructural features being involved in a 3D interstitial network in close vicinity to blood vessels in contact with immunoreactive cells in normal and treated skin. In contrast, the number of TCs was significantly decreased in psoriatic plaque. The remaining TCs demonstrated multiple degenerative features: apoptosis, membrane disintegration, cytoplasm fragmentation and nuclear extrusion. We also found changes in the phenotype of vascular smooth muscle cells in small blood vessels that lost the protective envelope formed by TCs. Therefore, impaired TCs could be a 'missed' trigger for the characteristic vascular pathology in psoriasis. Our data explain the mechanism of Auspitz's sign, the most pathognomonic clinical sign of psoriasis vulgaris. This study offers new insights on the cellularity of psoriatic lesions and we suggest that TCs should be considered new cellular targets in forthcoming therapies.

FIB-SEM tomography of human skin telocytes and their extracellular vesicles.

We have shown in 2012 the existence of telocytes (TCs) in human dermis. TCs were described by transmission electron microscopy (TEM) as interstitial cells located in non-epithelial spaces (stroma) of many organs (see www.telocytes.com). TCs have very long prolongations (tens to hundreds micrometers) named Telopodes (Tps). These Tps have a special conformation with dilated portions named podoms (containing mitochondria, endoplasmic reticulum and caveolae) and very thin segments (below resolving power of light microscopy), called podomers. To show the real 3D architecture of TC network, we used the most advanced available electron microscope technology: focused ion beam scanning electron microscopy (FIB-SEM) tomography. Generally, 3D reconstruction of dermal TCs by FIB-SEM tomography revealed the existence of Tps with various conformations: (i) long, flattened irregular veils (ribbon-like segments) with knobs, corresponding to podoms, and (ii) tubular structures (podomers) with uneven calibre because of irregular dilations (knobs) - the podoms. FIB-SEM tomography also showed numerous extracellular vesicles (diameter 438.6 ± 149.1 nm, n = 30) released by a human dermal TC. Our data might be useful for understanding the role(s) of TCs in intercellular signalling and communication, as well as for comprehension of pathologies like scleroderma, multiple sclerosis, psoriasis, etc.