Mast cell surfaceome characterization reveals CD98 heavy chain is critical for optimal cell function.

BACKGROUND: Mast cells are involved in many distinct pathologic conditions, suggesting that they recognize and respond to various stimuli and thus require a rich repertoire of cell surface proteins. However, mast cell surface proteomes have not been comprehensively characterized. OBJECTIVE: We aimed to further characterize the mast cell surface proteome to obtain a better understanding of how mast cells function in health and disease. METHODS: We enriched for glycosylated surface proteins expressed in mouse bone marrow-derived cultured mast cells (BMCMCs) and identified them using mass spectrometry analysis. The presence of novel surface proteins in mast cells was validated by real-time quantitative PCR and flow cytometry analysis in BMCMCs and peritoneal mast cells (PMCs). We developed a clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) gene editing approach to disrupt genes of interest in BMCMCs. RESULTS: The glycoprotein enrichment approach resulted in the identification of 1270 proteins in BMCMCs, 378 of which were localized to the plasma membrane. The most common protein classes among plasma membrane proteins were small GTPases, receptors, and transporters. One such cell surface protein was CD98 heavy chain (CD98hc), encoded by the Slc3a2 gene. Slc3a2 gene disruption resulted in a significant reduction in CD98hc expression, adhesion, and proliferation. CONCLUSIONS: Glycoprotein enrichment coupled with mass spectrometry can be used to identify novel surface molecules in mast cells. Moreover, CD98hc plays an important role in mast cell function.

Mast cell sarcoma: clinicopathologic and molecular analysis of 10 new cases and review of literature.

Mast cell sarcoma (MCS) is an exceedingly rare form of mastocytosis characterized by invasive malignant mast cell growth and metastatic potential. Diagnosis of MCS is very challenging due to its marked morphologic variations and significant immunophenotypic overlap with other neoplasms. In this study, we undertook an extensive study of 10 cases of MCS from our series, with review of additional 24 cases from the literature, to better clarify the clinicopathologic and molecular features of MCS. From the analyses of our 10 cases, MCS equally involved males and females with a median age of 54.5 years (range 1-63). The bone was the most common site of involvement, as noted in 9/10 of cases. Two patients had prior germ cell tumors (mediastinal germ cell tumor and ovarian dysgerminoma), and concurrent systemic mastocytosis was noted in one of nine patients. Serum tryptase levels were elevated in 6/7 of patients, and 3/9 of patients had mast cell activation symptoms. Morphologically, the tumor cells were typically large and pleomorphic with frequent reactive eosinophils. By immunohistochemical staining, MCS consistently expressed CD43 (8/8), CD117 (10/10), and mast cell tryptase (10/10), as well as CD13 (3/3) and CD33 (10/10), with variable positivity of CD2 (1/9), CD25 (4/9), CD30 (5/8), and CD68 (5/9). Notably, KIT D816V was not detected in nine cases in our study, although two cases had other mutations of KIT gene. Seven out of eight patients received chemotherapy with or without radiotherapy. However, the response was poor, and four out of eight patients died within a median follow-up interval of five months. Taken together, there are no standardized therapeutic regimens available for MCS at this time, and the prognosis is dismal. Therefore, it is critical to further investigate and characterize this rare entity, with the hope of improving diagnostic accuracy and providing more effective, targeted therapies.

MrgX2-SNAP-tag/cell membrane chromatography model coupled with liquid chromatography-mass spectrometry for anti-pseudo-allergic compound screening in Arnebiae Radix.

Pseudo-allergic reactions (PARs) are IgE-independent hypersensitivity reactions. Mas-related G protein-coupled receptor-X2 (MrgX2) was proved the key receptor of PAR. The anti-pseudo-allergic compound discovery based on MrgX2 was of great value. Cell membrane chromatography (CMC) based on MrgX2 provides a convenient and effective tool in anti-pseudo-allergic compound screening and discovery, and further improvements of this method are still needed. In this work, SNAP-tag was introduced at C-terminal of Mas-related G protein-coupled receptor (MrgX2-SNAP-tag), and an MrgX2-SNAP-tag/CMC model was then conducted using CMC technique. Comparative experiments showed that the new model not only satisfied the good selectivity and specificity of screening but also exhibited more stable and longer life span than traditional MrgX2/CMC model. By coupling with HPLC-MS, two compounds were screened out from Arnebiae Radix and identified as shikonin and acetylshikonin. Nonlinear chromatography was performed to study the interactions between two screened compounds and MrgX2, and binding constant (KA) of shikonin and acetylshikonin with MrgX2 were 2075.67 ± 0.34 M-1 and 32201.36 ± 0.35 M-1, respectively. Furthermore, ß-hexosaminidase and histamine release assay in vitro demonstrated that shikonin (1-5 µM) and acetylshikonin (2.5-10 µM) could both antagonize C48/80-induced allergic reaction. In conclusion, the MrgX2-SNAP-tag/CMC could be a reliable model for screening pseudo-allergy-related components from complex systems.

Systemic mastocytosis in adults: 2021 Update on diagnosis, risk stratification and management.

OVERVIEW: Systemic mastocytosis (SM) results from a clonal proliferation of abnormal mast cells (MC) in extra-cutaneous organs. DIAGNOSIS: The major criterion is presence of multifocal clusters of spindled MC in the bone marrow. Minor diagnostic criteria include elevated serum tryptase level, abnormal MC CD25 expression, and presence of KITD816V mutation. RISK STRATIFICATION: Establishing SM subtype as per the World Health Organization classification system is an important first step. Broadly, patients either have indolent/smoldering SM (ISM/SSM) or advanced SM, the latter includes aggressive SM (ASM), SM with associated hematological neoplasm (SM-AHN), and mast cell leukemia (MCL). Identification of poor-risk mutations (ie, ASXL1, RUNX1, SRSF2, NRAS) further refines the risk stratification. Recently, clinical and hybrid clinical-molecular risk models have been developed to more accurately assign prognosis in SM patients. MANAGEMENT: Treatment goals for ISM patients are primarily directed towards anaphylaxis prevention/symptom control/osteoporosis treatment. Patients with advanced SM frequently need MC cytoreductive therapy to ameliorate disease-related organ dysfunction. High response rates have been seen with small-molecule inhibitors that target mutant-KIT, including midostaurin (Food and Drug Administration approved) or avapritinib (investigational). Other options for MC cytoreduction include cladribine or interferon-α, although head-to-head comparisons are lacking. Treatment of SM-AHN primarily targets the AHN component, particularly if an aggressive disease such as acute myeloid leukemia is present. Allogeneic stem cell transplant can be considered in such patients, or in those with relapsed/refractory advanced SM. Imatinib has a limited therapeutic role in SM; effective cytoreduction is limited to those with imatinib-sensitive KIT mutations.

Mast cells and collagen fibrillogenesis.

This article presents 20 combinations of histochemical stainings for the determination of mast cell co-localization with the fibrous component of the connective tissue in the fibrillogenesis course. Best results were obtained using metachromatic detection of mast cells in combination with silver or picro-fuchsin impregnation, staining with brilliant green using van Gieson staining, and a combination of aniline blue staining with neutral red. Proposed variants of histochemical protocols open up new opportunities to analyze the participation of mast cells in extracellular matrix remodeling of the tissue microenvironment in the course of adaptive and pathological processes. Results obtained expand the current theoretical views of the process of fibrillogenesis in the extracellular matrix. They also shed new light on the participation of mast cell secretion components in the molecular mechanisms of fiber formation.

Mast Cell ß-Tryptase Is Enzymatically Stabilized by DNA.

Tryptase is a tetrameric serine protease located within the secretory granules of mast cells. In the secretory granules, tryptase is stored in complex with negatively charged heparin proteoglycans and it is known that heparin is essential for stabilizing the enzymatic activity of tryptase. However, recent findings suggest that enzymatically active tryptase also can be found in the nucleus of murine mast cells, but it is not known how the enzmatic activity of tryptase is maintained in the nuclear milieu. Here we hypothesized that tryptase, as well as being stabilized by heparin, can be stabilized by DNA, the rationale being that the anionic charge of DNA could potentially substitute for that of heparin to execute this function. Indeed, we showed that double-stranded DNA preserved the enzymatic activity of human ß-tryptase with a similar efficiency as heparin. In contrast, single-stranded DNA did not have this capacity. We also demonstrated that DNA fragments down to 400 base pairs have tryptase-stabilizing effects equal to that of intact DNA. Further, we showed that DNA-stabilized tryptase was more efficient in degrading nuclear core histones than heparin-stabilized enzyme. Finally, we demonstrated that tryptase, similar to its nuclear localization in murine mast cells, is found within the nucleus of primary human skin mast cells. Altogether, these finding reveal a hitherto unknown mechanism for the stabilization of mast cell tryptase, and these findings can have an important impact on our understanding of how tryptase regulates nuclear events.

Proteoglycans involved in bidirectional communication between mast cells and hippocampal neurons.

BACKGROUND: Mast cells (MCs) in the brain can respond to environmental cues and relay signals to neurons that may directly influence neuronal electrical activity, calcium signaling, and neurotransmission. MCs also express receptors for neurotransmitters and consequently can be activated by them. Here, we developed a coculture model of peritoneal MCs, incubated together with dissociated hippocampal neurons for the study of cellular mechanisms involved in the mast cell-neuron interactions. METHODS: Calcium imaging was used to simultaneously record changes in intracellular calcium [Ca2+]i in neurons and MCs. To provide insight into the contribution of MCs on neurotransmitter release in rat hippocampal neurons, we used analysis of FM dye release, evoked by a cocktail of mediators from MCs stimulated by heat. RESULTS: Bidirectional communication is set up between MCs and hippocampal neurons. Neuronal depolarization caused intracellular calcium [Ca2+]i oscillations in MCs that produced a quick response in neurons. Furthermore, activation of MCs with antigen or the secretagogue compound 48/80 also resulted in a neuronal [Ca2+]i response. Moreover, local application onto neurons of the MC mediator cocktail elicited Ca2+ transients and a synaptic release associated with FM dye destaining. Neuronal response was partially blocked by D-APV, a N-methyl-D-aspartate receptor (NMDAR) antagonist, and was inhibited when the cocktail was pre-digested with chondroitinase ABC, which induces enzymatic removal of proteoglycans of chondroitin sulfate (CS). CONCLUSIONS: MC-hippocampal neuron interaction affects neuronal [Ca2+]i and exocytosis signaling through a NMDAR-dependent mechanism.

Dexamethasone Promotes Keratinocyte Proliferation by Triggering Keratinocyte Growth Factor in Mast Cells.

BACKGROUND: The skin is a dynamic body organ that can be activated by both central and local hypothalamic-pituitary-adrenal axis systems. This phenomenon might be the crucial explanation why stress can cause relapse of chronic inflammatory skin diseases, such as psoriasis. Here, we determined the effects of mast cells on keratinocyte proliferation under stress hormone stimulation. METHODS: We subcutaneously injected dexamethasone on the shaved back of mice and evaluated histological changes and keratinocyte growth factor (KGF) expression on dermal mast cells. Further, human mast cell line (HMC-1) and keratinocyte cell line (HaCaT) cells were treated with dexamethasone in vitro to observe the extent of proliferation and the expression of KGF. Finally, the supernatants of HMC-1 cells treated with dexamethasone were used for the culture of HaCaT cells to investigate the effect on proliferation. RESULTS: We observed epidermal thickening in dexamethasone-injected mice, accompanied by an increase in the number of KGF-expressing dermal mast cells. Similar to mouse dermal mast cells, KGF was highly expressed in the human mast cell line HMC-1 following stimulation with dexamethasone. Further, dexamethasone-treated mast cells promoted keratinocyte proliferation in vitro. However, the effects of mast cells on keratinocytes were significantly diminished in the presence of anti-KGF-blocking antibodies. CONCLUSION: Taken together, our results show that a stressful environment may disturb skin barrier homeostasis through mast cell-derived KGF expression.

Mast cell chymase degrades fibrinogen and fibrin.

BACKGROUND: The accumulation of immunoreactants and fibrinoid necrosis of postcapillary vessel walls are common pathological features of cutaneous immune complex vasculitis. In more advanced lesions, these immunoreactants are subject to proteolysis. Mast cell chymase is a powerful enzyme that can degrade several substrates including the extracellular matrix. Heparin can influence the catalytic properties of chymase. OBJECTIVES: To study the effects of recombinant human (rh) chymase on fibrinogen, coagulation and fibrinolysis, and to relate these effects to the pathogenesis of vasculitis. METHODS: The colocalization of chymase and fibrin in vasculitis specimens was analysed by immunohistochemical double staining. Fibrinogen and fibrin were treated with rh-chymase and the effects were studied in vitro by sodium dodecylsulfate polyacrylamide gel electrophoresis and a variety of clotting and fibrin gel experiments. The effects of rh-chymase on vasculitis cryosections were analysed by direct immunofluorescence. RESULTS: Chymase-positive mast cells were associated with fibrin-positive vessels in vasculitis cryosections. Rh-chymase degraded the alpha-, beta- and gamma-chains of fibrinogen, while heparin enhanced the degradation of the beta-chain. Rh-chymase pretreatment of fibrinogen prolonged thrombin-induced clotting time. Fibrinogen degradation products induced by rh-chymase increased the clotting time of human plasma. Rh-chymase degraded fibrin gel prepared from fibrinogen or human plasma. Immunofluorescence staining positivity of fibrin in vasculitis cryosections decreased after pretreatment with rh-chymase for 24 h, and heparin enhanced this effect. CONCLUSIONS: Mast cell chymase may constitute a previously unrecognized endogenous anticoagulant and fibrinolytic enzyme, and may be involved in the clearance of fibrin from vessel walls in aged vasculitis lesions.

Inhibitory Effects of Phenylpropanoid Derivatives from Oenanthe javanica on Antigen-Stimulated Degranulation in RBL-2H3 Cells.

Two diacyldaucic acids (1 and 2), an α,ß-unsaturated γ-lactone-type lignan (3) and its derivatives (4-6), and 12 known compounds were isolated from a traditional East Asian vegetable, Oenanthe javanica. The absolute configuration of 1 was validated by obtaining (+)-osbeckic acid through acid hydrolysis. The absolute configurations of 3-5 were determined by comparing their experimental and computed ECD data. The conclusion was supported by applying the phenylglycine methyl ester method to 3. Compound 6 was obtained as an interconverting mixture of isomers in a 3:1 trans- cis ratio. Several water-soluble components (1, 3, and 6) showed concentration-dependent inhibitory effects on antigen-stimulated degranulation in RBL-2H3 cells without producing any direct cytotoxicity against RBL-2H3 or HeLa cells.

Proteomic Analysis of Lipid Rafts from RBL-2H3 Mast Cells.

Lipid rafts are highly ordered membrane microdomains enriched in cholesterol, glycosphingolipids, and certain proteins. They are involved in the regulation of cellular processes in diverse cell types, including mast cells (MCs). The MC lipid raft protein composition was assessed using qualitative mass spectrometric characterization of the proteome from detergent-resistant membrane fractions from RBL-2H3 MCs. Using two different post-isolation treatment methods, a total of 949 lipid raft associated proteins were identified. The majority of these MC lipid raft proteins had already been described in the RaftProtV2 database and are among highest cited/experimentally validated lipid raft proteins. Additionally, more than half of the identified proteins had lipid modifications and/or transmembrane domains. Classification of identified proteins into functional categories showed that the proteins were associated with cellular membrane compartments, and with some biological and molecular functions, such as regulation, localization, binding, catalytic activity, and response to stimulus. Furthermore, functional enrichment analysis demonstrated an intimate involvement of identified proteins with various aspects of MC biological processes, especially those related to regulated secretion, organization/stabilization of macromolecules complexes, and signal transduction. This study represents the first comprehensive proteomic profile of MC lipid rafts and provides additional information to elucidate immunoregulatory functions coordinated by raft proteins in MCs.

Stretchable and Photocatalytically Renewable Electrochemical Sensor Based on Sandwich Nanonetworks for Real-Time Monitoring of Cells.

Stretchable electrochemical (EC) sensors have broad prospects in real-time monitoring of living cells and tissues owing to their excellent elasticity and deformability. However, the redox reaction products and cell secretions are easily adsorbed on the electrode, resulting in sensor fouling and passivation. Herein, we developed a stretchable and photocatalytically renewable EC sensor based on Au nanotubes (NTs) and TiO2 nanowires (NWs) sandwich nanonetworks. The external Au NTs are used for EC sensing, and internal TiO2 NWs provide photocatalytic performance to degrade contaminants, which endows the sensor with excellent EC performance, high photocatalytic activity, and favorable mechanical tensile property. This allows highly sensitive recycling monitoring of NO released from endothelial cells and 5-HT released from mast cells under their stretching states in real time, therefore providing a promising tool to unravel elastic and mechanically sensitive cells, tissues, and organs.

Mast cell glycosaminoglycans.

Mast cells contain granules packed with a mixture of proteins that are released on degranulation. The proteoglycan serglycin carries an array of glycosaminoglycan (GAG) side chains, sometimes heparin, sometimes chondroitin or dermatan sulphate. Tight packing of granule proteins is dependent on the presence of serglycin carrying these GAGs. The GAGs of mast cells were most intensively studied in the 1970s and 1980s, and though something is known about the fine structure of chondroitin sulphate and dermatan sulphate in mast cells, little is understood about the composition of the heparin/heparan sulphate chains. Recent emphasis on the analysis of mast cell heparin from different species and tissues, arising from the use of this GAG in medicine, lead to the question of whether variations within heparin structures between mast cell populations are as significant as variations in the mix of chondroitins and heparins.

Phenotypic variability in human skin mast cells.

Mast cells (MCs) are unique constituents of the human body. While inter-individual differences may influence the ways by which MCs operate in their skin habitat, they have not been surveyed in a comprehensive manner so far. We therefore set out to quantify skin MC variability in a large cohort of subjects. Pathophysiologically relevant key features were quantified and correlated: transcripts of c-kit, FcεRIα, FcεRIß, FcεRIγ, histidine decarboxylase, tryptase, and chymase; surface expression of c-Kit, FcεRIα; activity of tryptase, and chymase; histamine content and release triggered by FcεRI and Ca(2+) ionophore. While there was substantial variability among subjects, it strongly depended on the feature under study (coefficient of variation 33-386%). Surface expression of FcεRI was positively associated with FcεRIα mRNA content, histamine content with HDC mRNA, and chymase activity with chymase mRNA. Also, MC signature genes were co-regulated in distinct patterns. Intriguingly, histamine levels were positively linked to tryptase and chymase activity, whereas tryptase and chymase activity appeared to be uncorrelated. FcεRI triggered histamine release was highly variable and was unrelated to FcεRI expression but unexpectedly tightly correlated with histamine release elicited by Ca(2+) ionophore. This most comprehensive and systematic work of its kind provides not only detailed insights into inter-individual variability in MCs, but also uncovers unexpected patterns of co-regulation among signature attributes of the lineage. Differences in MCs among humans may well underlie clinical responses in settings of allergic reactions and complex skin disorders alike.

Formulation, optimization and characterization of cationic polymeric nanoparticles of mast cell stabilizing agent using the Box-Behnken experimental design.

OBJECTIVE: The present research work was intended to develop and optimize sustained release of biodegradable chitosan nanoparticles (CSNPs) as delivery vehicle for sodium cromoglicate (SCG) using the circumscribed Box-Behnken experimental design (BBD) and evaluate its potential for oral permeability enhancement. METHODS: The 3-factor, 3-level BBD was employed to investigate the combined influence of formulation variables on particle size and entrapment efficiency (%EE) of SCG-CSNPs prepared by ionic gelation method. The generated polynomial equation was validated and desirability function was utilized for optimization. Optimized SCG-CSNPs were evaluated for physicochemical, morphological, in-vitro characterizations and permeability enhancement potential by ex-vivo and uptake study using CLSM. RESULTS: SCG-CSNPs exhibited particle size of 200.4 ± 4.06 nm and %EE of 62.68 ± 2.4% with unimodal size distribution having cationic, spherical, smooth surface. Physicochemical and in-vitro characterization revealed existence of SCG in amorphous form inside CSNPs without interaction and showed sustained release profile. Ex-vivo and uptake study showed the permeability enhancement potential of CSNPs. CONCLUSIONS: The developed SCG-CSNPs can be considered as promising delivery strategy with respect to improved permeability and sustained drug release, proving importance of CSNPs as potential oral delivery system for treatment of allergic rhinitis. Hence, further studies should be performed for establishing the pharmacokinetic potential of the CSNPs.

Randomly organized lipids and marginally stable proteins: a coupling of weak interactions to optimize membrane signaling.

Eukaryotic lipids in a bilayer are dominated by weak cooperative interactions. These interactions impart highly dynamic and pliable properties to the membrane. C2 domain-containing proteins in the membrane also interact weakly and cooperatively giving rise to a high degree of conformational plasticity. We propose that this feature of weak energetics and plasticity shared by lipids and C2 domain-containing proteins enhance a cell's ability to transduce information across the membrane. We explored this hypothesis using information theory to assess the information storage capacity of model and mast cell membranes, as well as differential scanning calorimetry, carboxyfluorescein release assays, and tryptophan fluorescence to assess protein and membrane stability. The distribution of lipids in mast cell membranes encoded 5.6-5.8bits of information. More information resided in the acyl chains than the head groups and in the inner leaflet of the plasma membrane than the outer leaflet. When the lipid composition and information content of model membranes were varied, the associated C2 domains underwent large changes in stability and denaturation profile. The C2 domain-containing proteins are therefore acutely sensitive to the composition and information content of their associated lipids. Together, these findings suggest that the maximum flow of signaling information through the membrane and into the cell is optimized by the cooperation of near-random distributions of membrane lipids and proteins. This article is part of a Special Issue entitled: Interfacially Active Peptides and Proteins. Guest Editors: William C. Wimley and Kalina Hristova.

The architectural relationship of components controlling mast cell endocytosis.

Eukaryotic cells use multiple routes for receptor internalization. Here, we examine the topographical relationships of clathrin-dependent and clathrin-independent endocytic structures on the plasma membranes of leukemia-derived mast cells. The high affinity IgE receptor (FcεRI) utilizes both pathways, whereas transferrin receptor serves as a marker for the classical clathrin-mediated endocytosis pathway. Both receptors were tracked by live-cell imaging in the presence or absence of inhibitors that established their differential dependence on specific endocytic adaptor proteins. The topology of antigen-bound FcεRI, clathrin, dynamin, Arf6 and Eps15-positive structures were analyzed by 2D and 3D immunoelectron microscopy techniques, revealing their remarkable spatial relationships and unique geometry. We conclude that the mast cell plasma membrane has multiple specialized domains for endocytosis. Their close proximity might reflect shared components, such as lipids and adaptor proteins, that facilitate inward membrane curvature. Intersections between these specialized domains might represent sorting stations that direct cargo to specific endocytic pathways.

Acidic environment augments FcεRI-mediated production of IL-6 and IL-13 in mast cells.

Although blood pH is maintained in a narrow range of around pH 7.4 in living organisms, inflammatory loci are characterized by acidic conditions. Mast cells tend to reside close to the surface of the body in areas such as the mucosa and skin where they may be exposed to exogenous acids, and they play an important role in immune responses. However, little is known about the effects of extracellular acidification on the functions of mast cell. Here, we found that extracellular acidification increased the dinitrophenyl-conjugated human serum albumin (DNP-HSA)-induced production of interleukin (IL)-6 and IL-13 in MC/9 cells or bone marrow-derived mouse mast cells sensitized with anti-DNP IgE. Extracellular acidification also inhibited migration of MC/9 cells toward DNP-HSA. In addition, acidic pH stimulated antigen-induced activation of p38 mitogen-activated protein kinase (MAPK) and protein kinase B (Akt). These findings suggest that extracellular acidification augmented antigen/IgE-induced and FcεRI-mediated production of IL-6 and IL-13 in mast cells, and that this was associated with the enhancement of p38 MAPK and Akt activation.

Adult-onset mastocytosis in the skin is highly suggestive of systemic mastocytosis.

Adult-onset urticaria pigmentosa/mastocytosis in the skin almost always persists throughout life. The prevalence of systemic mastocytosis in such patients is not precisely known. Bone marrow biopsies from 59 patients with mastocytosis in the skin and all available skin biopsies (n=27) were subjected to a meticulous cytological, histological, immunohistochemical, and molecular analysis for the presence of WHO-defined diagnostic criteria for systemic mastocytosis: compact mast cell infiltrates (major criterion); atypical mast cell morphology, KIT D816V, abnormal expression of CD25 by mast cells, and serum tryptase levels >20 ng/ml (minor criteria). Systemic mastocytosis is diagnosed when the major diagnostic criterion plus one minor criterion or at least three minor criteria are fulfilled. Systemic mastocytosis was confirmed in 57 patients (97%) by the diagnosis of compact mast cell infiltrates plus at least one minor diagnostic criterion (n=42, 71%) or at least three minor diagnostic criteria (n=15, 25%). In two patients, only two minor diagnostic criteria were detectable, insufficient for the diagnosis of systemic mastocytosis. By the use of highly sensitive molecular methods, including the analysis of microdissected mast cells, KIT D816V was found in all 58 bone marrow biopsies investigated for it but only in 74% (20/27) of the skin biopsies. It is important to state that even in cases with insufficient diagnostic criteria for systemic mastocytosis, KIT D816V-positive mast cells were detected in the bone marrow. This study demonstrates, for the first time, that almost all patients with adult-onset mastocytosis in the skin, in fact, have systemic mastocytosis with cutaneous involvement.

Characteristics of the New Mast Cell-Rich Nodal Structure in the Rat Skin Surface.

Background: : Acupuncture, practiced for millennia, lacks a clear anatomical definition for acupoints. A prevailing theory suggests that acupoints overlap with skin areas with higher mast cell density. Skin spots stained with intravenously infused Evans blue (EB), indicative of neurogenic inflammation, have recently been posited as acupoints in rats. Objectives: : To demonstrate the concordance between EB-reactive skin spots and mast cell-enriched acupoints. Methods: : We employed staining and RNA-seq analysis to delineate the morphological characteristics and gene expression profiles of EB-reactive skin spots in rats. Results: : EB infusion revealed a novel nodal structure on the rat skin surface, visible to the naked eye, with dimensions of approximately 1 mm in both diameter and height. Around 30 such nodes were identified on one side of the abdominal area, spaced roughly 3 mm apart, excluding the linea alba. RNA-seq analysis indicated that the gene expression patterns within these nodes markedly differed from both non-nodal skin areas and lymph nodes. Histological examination using toluidine blue revealed a significantly greater mast cell count in the nodes than in non-nodal skin regions. Additionally, the nodes stained positively with Alcian blue and Hemacolor, reagents known to mark primo vascular tissues. Conclusion: : Our findings suggest that EB-reactive nodes are indeed rich in mast cells. Further research is warranted to establish these skin nodes as surface primo nodes.