Elevated Myl9 reflects the Myl9-containing microthrombi in SARS-CoV-2-induced lung exudative vasculitis and predicts COVID-19 severity.

The mortality of coronavirus disease 2019 (COVID-19) is strongly correlated with pulmonary vascular pathology accompanied by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection-triggered immune dysregulation and aberrant activation of platelets. We combined histological analyses using field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy analyses of the lungs from autopsy samples and single-cell RNA sequencing of peripheral blood mononuclear cells to investigate the pathogenesis of vasculitis and immunothrombosis in COVID-19. We found that SARS-CoV-2 accumulated in the pulmonary vessels, causing exudative vasculitis accompanied by the emergence of thrombospondin-1-expressing noncanonical monocytes and the formation of myosin light chain 9 (Myl9)-containing microthrombi in the lung of COVID-19 patients with fatal disease. The amount of plasma Myl9 in COVID-19 was correlated with the clinical severity, and measuring plasma Myl9 together with other markers allowed us to predict the severity of the disease more accurately. This study provides detailed insight into the pathogenesis of vasculitis and immunothrombosis, which may lead to optimal medical treatment for COVID-19.

TM2D3, a mammalian homologue of Drosophila neurogenic gene product Almondex, regulates surface presentation of Notch receptors.

Notch signaling is an evolutionarily conserved mechanism required for numerous types of cell fate decisions in metazoans. It mediates short-range communication between cells with receptors and ligands, both of which are expressed on the cell surfaces. In response to the ligand-receptor interaction, the ligand and the extracellular domain of the Notch receptor (NECD) in the complex are internalized into ligand-expressing cells by endocytosis, a prerequisite process for the conformational change of the membrane proximal region of Notch to induce critical proteolytic cleavages for its activation. Here we report that overexpression of transmembrane 2 (TM2) domain containing 3 (TM2D3), a mammalian homologue of Drosophila melanogaster Almondex (Amx), activates Notch1. This activation requires the ligand-binding domain in Notch1 and the C-terminal region containing TM2 domain in TM2D3. TM2D3 physically associates with Notch1 at the region distinct from the ligand-binding domain and enhances expression of Notch1 on the cell surface. Furthermore, cell surface expression of Notch1 and Notch2 is reduced in Tm2d3-deficient cells. Finally, amx-deficient Drosophila early embryos exhibit impaired endocytosis of NECD and Delta ligand, for which surface presentation of Notch is required. These results indicate that TM2D3 is an element involved in Notch signaling through the surface presentation.

Clinical and Histological Effects of Partial Blood Flow Impairment in Vascularized Lymph Node Transfer.

Regarding vascularized lymph node transfer (VLNT) for lymphedema, partial blood flow impairment in transferred lymph node (LN) flaps may adversely affect the therapeutic results. We investigated the clinical and histological effects of partial blood flow impairment in LN flaps. In upper extremity lymphedema cases, based on ultrasonographic examination at 2 weeks after VLNT, we compared the treatment results depending on whether the postoperative blood flow in transferred LNs was good (Group G) or poor (Group P). Novel partial ischemia and congestion of LN flap mouse models were developed to determine their histological features. In 42 cases, significant differences were observed between Group G (n = 37) and Group P (n = 5) based on the amount of volume reduction (136.7 ± 91.7 mL and 55.4 ± 60.4 mL, respectively; p = 0.04) and lymph flow recanalization rate in indocyanine green fluorescent lymphography (67.6% and 0%, respectively; p = 0.0007). In mouse models, thrombi formation in the marginal sinus and numerous Myl9/12-positive immunocompetent cells in follicles were observed in congested LNs. Blood flow maintenance in the transferred LNs is an essential factor influencing the therapeutic effect of VLNT. Postoperatively, surgeons should closely monitor blood flow in the transferred LNs, particularly in cases of congestion.

The new preparation method for paraffin-embedded samples applying scanning electron microscopy revealed characteristic features in asthma-induced mice.

In bronchial asthma patients, mucous cell metaplasia (MCM) and fibrosis occur in the bronchial epithelium and interstitium, respectively. The mucus and collagen fibers are identified by Periodic acid-Schiff stain (PAS) or Sirius red stain on optical microscopy. On a scanning electron microscope (SEM) observation, formalin-fixed-paraffin-embedded specimens have high insulation, thereby attenuating the scattered electron signals leading to insufficient contrast. Moreover, there were no staining methods for SEM observation, which characterizes the changes in epithelium and interstitium by enhancing the scattered electrons. In this study, we established a method of coating osmium thin film on pathological tissue specimens using plasma chemical vapor deposition technology. This method ensured the intensity of scattered electron signals and enabled SEM observation. Furthermore, we found that morphological changes in MCM and interstitial fibrosis could be characterized by Grocott stain, which we optimized to evaluate pathological remodeling in bronchial asthma. Using these techniques, we compared asthma-induced mice with Amphiregulin (Areg) knockout mice, and found that Areg induce MCM, but the production of Grocott-stain-positive substrate in the interstitium is Areg-independent. The method developed in this study provides an understanding of the pathological spatial information linked to the ultrastructural changes in cells and interstitium due to disease-related signaling abnormalities.

Increased Myosin light chain 9 expression during Kawasaki disease vasculitis.

Introduction: Kawasaki disease (KD) is an acute systemic vasculitis that predominantly afflicts children. KD development is known to be associated with an aberrant immune response and abnormal platelet activation, however its etiology is still largely unknown. Myosin light chain 9 (Myl9) is known to regulate cellular contractility of both non-muscle and smooth muscle cells, and can be released from platelets, whereas any relations of Myl9 expression to KD vasculitis have not been examined. Methods: Plasma Myl9 concentrations in KD patients and children with febrile illness were measured and associated with KD clinical course and prognosis. Myl9 release from platelets in KD patients was also evaluated in vitro. Myl9 expression was determined in coronary arteries from Lactobacillus casei cell wall extract (LCWE)-injected mice that develop experimental KD vasculitis, as well as in cardiac tissues obtained at autopsy from KD patients. Results and discussion: Plasma Myl9 levels were significantly higher in KD patients during the acute phase compared with healthy controls or patients with other febrile illnesses, declined following IVIG therapy in IVIG-responders but not in non-responders. In vitro, platelets from KD patients released Myl9 independently of thrombin stimulation. In the LCWE-injected mice, Myl9 was detected in cardiac tissue at an early stage before inflammatory cell infiltration was observed. In tissues obtained at autopsy from KD patients, the highest Myl9 expression was observed in thrombi during the acute phase and in the intima and adventitia of coronary arteries during the chronic phase. Thus, our studies show that Myl9 expression is significantly increased during KD vasculitis and that Myl9 levels may be a useful biomarker to estimate inflammation and IVIG responsiveness to KD.

Ang II-stimulated migration of vascular smooth muscle cells is dependent on LR11 in mice.

Medial-to-intimal migration of SMCs is critical to atherosclerotic plaque formation and remodeling of injured arteries. Considerable amounts of the shed soluble form of the LDL receptor relative LR11 (sLR11) produced by intimal SMCs enhance SMC migration in vitro via upregulation of urokinase-type plasminogen activator receptor (uPAR) expression. Here, we show that circulating sLR11 is a novel marker of carotid intima-media thickness (IMT) and that targeted disruption of the LR11 gene greatly reduces intimal thickening of arteries through attenuation of Ang II-induced migration of SMCs. Serum concentrations of sLR11 were positively correlated with IMT in dyslipidemic subjects, and multivariable regression analysis suggested sLR11 levels as an index of IMT, independent of classical atherosclerosis risk factors. In Lr11-/- mice, femoral artery intimal thickness after cuff placement was decreased, and Ang II-stimulated migration and attachment of SMCs from these mice were largely abolished. In isolated murine SMCs, sLR11 caused membrane ruffle formation via activation of focal adhesion kinase/ERK/Rac1 accompanied by complex formation between uPAR and integrin alphavbeta3, a process accelerated by Ang II. Overproduction of sLR11 decreased the sensitivity of Ang II-induced activation pathways to inhibition by an Ang II type 1 receptor blocker in mice. Thus, we demonstrate a requirement for sLR11 in Ang II-induced SMC migration and propose what we believe is a novel role for sLR11 as a biomarker of carotid IMT.

Noninvasive, objective evaluation of lower extremity lymphedema severity using shear wave elastography: A preliminary study.

BACKGROUND: Increased skin and subcutaneous tissue stiffness in patients with early-stage lymphedema has been reported. The purpose of this study was to examine the use of shear wave elastography (SWE) for evaluating lower extremity lymphedema (LEL). METHODS: For 10 lower extremities of normal controls and 72 limbs of patients with gynecological cancer whose lymphatic function was categorized into six stages based on the range of dermal backflow (DBF) observed in indocyanine green (ICG) lymphography, SWE was performed and shear wave velocity (SWV) of the dermis and three layers of subcutaneous tissue at the thigh and calf were recorded. Twenty-five patients underwent thigh tissue histological and dermal thickness examinations. RESULTS: The strongest correlation between the ICG DBF stage and SWV during SWE was observed on the dermal layer of the thigh (p < 0.01, R = 0.67). There was a significant correlation between the dermal thickness of the thigh and the ICG DBF stage (p < 0.01, R = 0.87) and also between the dermal thickness of the thigh and SWV (p < 0.01, R = 0.73). CONCLUSION: Noninvasive, objective evaluation of LEL severity using SWE was well correlated with lymphatic function as determined by ICG lymphography. The DBF changes in the dermis of the thigh best reflected the changes in lymphatic function. Dermal thickness variations may partially account for differences in SWV.

Calcification in Werner syndrome associated with lymphatic vessels aging.

In addition to the symptoms of aging, the main symptoms in Werner syndrome (WS), a hereditary premature aging disease, include calcification of subcutaneous tissue with solid pain and refractory skin ulcers. However, the mechanism of calcification in WS remains unclear. In this study, the histological analysis of the skin around the ulcer with calcification revealed an accumulation of calcium phosphate in the lymphatic vessels. Moreover, the morphological comparison with the lymphatic vessels in PAD patients with chronic skin ulcers demonstrated the ongoing lymphatic remodeling in WS patients because of the narrow luminal cross-sectional area (LA) of the lymphatic vessels but the increment of lymphatic microvessels density (MLVD). Additionally, fluorescence immunohistochemical analysis presented the cytoplasmic distribution and the accumulation of WRN proteins in endothelial cells on remodeling lymphatic vessels. In summary, these results point out a relationship between calcification in lymphatic vessels and the remodeling of lymphatic vessels and suggest the significance of the accumulation of WRN mutant proteins as an age-related change in WS patients. Thus, cytoplasmic accumulation of WRN protein can be an indicator of the decreasing drainage function of the lymphatic vessels and the increased risk of skin ulcers and calcification in the lymphatic vessels.

Detection of Nonpalpable Tiny Axillary Lymph Nodes Surrounded by Adipose Tissue Using a Near-Infrared Camera.

Background: It is not always possible to detect nonpalpable small lymph nodes (LNs) surrounded by adipose tissue under the wavelength of visible light. A newly developed near-infrared camera with InGaAs element was able to capture photographs using light at >1000-nm wavelength, at which the difference in absorbance between water and lipids is large. This study investigated the ability to detect nonvisible small LNs using light at 1300-nm wavelength. Methods and Results: Following retrieval of LNs through axillary LN dissection from 20 patients with breast cancer, residual specimens were simultaneously photographed using light at 970-, 1070-, 1200-, 1300-, 1450-, and 1600-nm wavelengths. A total of 45 specimens were observed pathologically at the selected portions in which the 1300-nm light was absorbed (high absorbance group [HA group], n = 25) and those in which the 970-nm light was absorbed instead (low absorbance group [LA group], n = 20). All specimens categorized in the HA group detected the LNs, whereas none of those categorized in the LA group detected an LN. The sensitivity and specificity in the identification of an LN were 1.0. The LNs detected using this camera were significantly smaller than those detected by surgeons (3.00 ± 2.93 mm vs. 5.90 ± 3.91 mm, p < 0.01). Discussion: The light at 1300-nm wavelength was absorbed by axillary LNs. This camera detected LNs that were undetectable by surgeons. This novel technology may be applied to lymphatic microsurgery and contribute to the development of a minimally invasive LN dissection method.

CD44 signaling through focal adhesion kinase and its anti-apoptotic effect.

Adhesion molecules can initiate intracellular signaling. Engagement of CD44 either by its natural ligand hyaluronan or a specific antibody on a cell line induced tyrosine phosphorylation and activation of focal adhesion kinase (FAK), which then associated with phosphatidylinositol 3-kinase (PI3K) and activated mitogen-activated protein kinase at its downstream. However, the introduction of dominant negative Rho into the cells inhibited the CD44-stimulated FAK phosphorylation. Cells expressing CD44 were significantly resistant to etoposide-induced apoptosis. This anti-apoptotic effect was cancelled by the inhibition of either Rho, FAK or PI3K. These results may indicate a signaling pathway from CD44 to mediate the resistance against drug-induced apoptosis in cancer cells.

Fragmented hyaluronan is an autocrine chemokinetic motility factor supported by the HAS2-HYAL2/CD44 system on the plasma membrane.

Hyaluronan (HA) is synthesized by HA synthase (HAS) 1, HAS2 and HAS3, and degraded by hyaluronidase (HYAL) 1 and HYAL2 in a CD44-dependent manner. HA and HYALs are intricately involved in tumor growth and metastasis. Random cell movement is generally described as chemokinesis, and represents an important step at the beginning of tumor cell liberation from the primary site. To investigate the roles of HAS2 and HYAL2/CD44 in cell motility, we examined HeLa-S3 cells showing spontaneous chemokinesis. HeLa-S3 cells expressed HAS2 and HAS3. siRNA-mediated knockdown of HAS2 decreased spontaneous chemokinesis of HeLa-S3 cells. Although HeLa-S3 cells secreted 50 ng/ml of high molecular weight (HMW)-HA (peak: 990 kDa) into the culture supernatant after 6 h of culture, exogenously added HMW-HA did not enhance spontaneous chemokinesis of the cells. These observations suggested that HeLa-S3 cells may have a self-degrading system for HA to regulate their spontaneous chemokinesis. To examine this possibility, we investigated the effects of siRNA-mediated knockdown of HYAL2 or CD44 on the spontaneous chemokinesis of HeLa-S3 cells. Knockdown of either molecule decreased the spontaneous chemokinesis of the cells. Low molecular weight (LMW)-HA (23 kDa) reversed the HYAL2 siRNA-mediated reduction in spontaneous chemokinesis of HeLa-S3 cells to the level in control cells stimulated with the same HA. These findings indicate that the HAS2-HYAL2/CD44 system may support spontaneous chemokinesis of human cancer cells through self-degradation of HMW-HA to produce LMW-HA by an autocrine mechanism. Consequently, our study may further expand our understanding of HA functions in cancer.