Connexin 43 mediated gap junctional communication enhances breast tumor cell diapedesis in culture

INTRODUCTION: Metastasis involves the emigration of tumor cells through the vascular endothelium, a process also known as diapedesis. The molecular mechanisms regulating tumor cell diapedesis are poorly understood, but may involve heterocellular gap junctional intercellular communication (GJIC) between tumor cells and endothelial cells. METHOD: To test this hypothesis we expressed connexin 43 (Cx43) in GJIC-deficient mammary epithelial tumor cells (HBL100) and examined their ability to form gap junctions, establish heterocellular GJIC and migrate through monolayers of human microvascular endothelial cells (HMVEC) grown on matrigel-coated coverslips. RESULTS: HBL100 cells expressing Cx43 formed functional heterocellular gap junctions with HMVEC monolayers within 30 minutes. In addition, immunocytochemistry revealed Cx43 localized to contact sites between Cx43 expressing tumor cells and endothelial cells. Quantitative analysis of diapedesis revealed a two-fold increase in diapedesis of Cx43 expressing cells compared to empty vector control cells. The expression of a functionally inactive Cx43 chimeric protein in HBL100 cells failed to increase migration efficiency, suggesting that the observed up-regulation of diapedesis in Cx43 expressing cells required heterocellular GJIC. This finding is further supported by the observation that blocking homocellular and heterocellular GJIC with carbenoxolone in co-cultures also reduced diapedesis of Cx43 expressing HBL100 tumor cells. CONCLUSION: Collectively, our results suggest that heterocellular GJIC between breast tumor cells and endothelial cells may be an important regulatory step during metastasis

A computationally designed antigen eliciting broad humoral responses against SARS-CoV-2 and related sarbecoviruses

The threat of spillovers of coronaviruses associated with the severe acute respiratory syndrome (SARS) from animals to humans necessitates vaccines that offer broader protection from sarbecoviruses. By leveraging a viral-genome-informed computational method for selecting immune-optimized and structurally engineered antigens, here we show that a single antigen based on the receptor binding domain of the spike protein of sarbecoviruses elicits broad humoral responses against SARS-CoV-1, SARS-CoV-2, WIV16 and RaTG13 in mice, rabbits and guinea pigs. When administered as a DNA immunogen or by a vector based on a modified vaccinia virus Ankara, the optimized antigen induced vaccine protection from the Delta variant of SARS-CoV-2 in mice genetically engineered to express angiotensin-converting enzyme 2 and primed by a viral-vector vaccine (AZD1222) against SARS-CoV-2. A vaccine formulation incorporating mRNA coding for the optimized antigen further validated its broad immunogenicity. Vaccines that elicit broad immune responses across subgroups of coronaviruses may counteract the threat of zoonotic spillovers of betacoronaviruses

The biomechanical and morphological characteristics of the ligamentum mucosum and its potential role in anterior knee pain.

Background: The ligamentum mucosum is composed of dense regular connective tissue and traverses from the distal femur to the infrapatellar fat pad. While the gross and histologic morphology has been studied, there is currently no evidence concerning the biomechanical properties of the ligamentum mucosum and the potential of anterior knee pain. The purpose of this study was to determine the anatomical, mechanical and histological properties of the ligamentum mucosum. Methods: Dissections were performed on cadaveric knee specimens (N = 18) and histological analysis (n = 6) was performed to define the anatomical characteristics of the ligamentum mucosum using standard hematoxylin and eosin (H&E), Masson\u27s trichrome, and immunohistochemical methods. Biomechanical testing (n = 5) was conducted to determine the tensile properties of the ligamentum mucosum. The peak load at failure, stiffness, and strain were analyzed. Results: Sixty-four percent of the knees had a ligamentum mucosum and the histological analysis confirmed it to be composed of dense regular connective tissue. Small peripheral nerves were identified in the junction between the ligamentum mucosum and the fat pad. The average (SD) peak force of failure, stiffness, and strain were 31.9 N (19.0), 5.1 N/mm (3.59), and 0.83 (0.14), respectively. Conclusions: The tensile strength and stiffness of the ligamentum mucosum is considerably less than the primary stabilizers of the knee joint. Based on these findings, it is improbable that the ligamentum mucosum has a meaningful effect on the kinematics of the extensor mechanism; perturbations of the tissue and the connected infrapatellar fat pad could potentially play a role in the pathogenesis of anterior knee pain. (C) 2018 Elsevier B.V. All rights reserved

Why does allergic contact dermatitis exist?

The skin immune system's propensity to produce allergic contact dermatitis (ACD) to harmless chemicals, while otherwise being an efficient defence system, represents a dermatological paradox. We postulate that a major role in signalling in ACD is played by Toll-like receptor (TLR)2 and TLR4, and arises from their activation by extracellular danger-associated molecular patterns (DAMPs). Ligand activation of TLR4/2 results in the expression of interleukins (ILs) IL-1β, IL-6, IL-12, IL-18 and IL-23, tumour necrosis factor-α and interferon-α. These cytokines promote acquisition of sensitization, and facilitate elicitation of contact allergy via multiple mechanisms, including the recruitment of CD4+ Th1 and Th17 cells. As Th1 cells secrete large amounts of DAMPs, a DAMP immune circuit (positive-feedback loop) is created. This is an important driver of skin sensitization and skin inflammation. Pathogenic extracellular bacteria, but not commensal bacteria, produce pathogen-associated molecular pattern molecules, which stimulate the expression of Th1- and Th17-promoting cytokines via TLR2 and TLR4. This also induces an immune circuit. The ability of the skin immune system to activate host defence mechanisms and to distinguish between pathogenic bacteria and commensals provides an explanation for why skin sensitization and ACD develop, as they are processes that rely on the same biological pathways. These pathways may also shed light on the pathogenesis of chronic pustular inflammatory dermatoses (e.g. acne vulgaris). The existence of safety signals from commensal bacteria, which prevent initiation of these pathways, may provide opportunities for novel therapeutic approaches to the treatment of inflammatory skin diseases. © 2013 The Authors. BJD © 2013 British Association of Dermatologists