Dynamics of macrophage polarization support persistence in a whole living organism.

Numerous intracellular bacterial pathogens interfere with macrophage function, including macrophage polarization, to establish a niche and persist. However, the spatiotemporal dynamics of macrophage polarization during infection within host remain to be investigated. Here, we implement a model of persistent Typhimurium infection in zebrafish, which allows visualization of polarized macrophages and bacteria in real time at high resolution.

An arginase 2 promoter transgenic line illuminates immune cell polarisation in zebrafish.

Innate immune responses to inflammation and infection are complex and represent major challenges for developing much needed new treatments for chronic inflammatory diseases and drug-resistant infections. To be ultimately successful, the immune response must be balanced to allow pathogen clearance without excess tissue damage, processes controlled by pro- and anti-inflammatory signals. The roles of anti-inflammatory signalling in raising an appropriate immune response are underappreciated, representing overlooked potential drug targets.

Segmentation-based tracking of macrophages in 2D＋time microscopy movies inside a living animal.

The automated segmentation and tracking of macrophages during their migration are challenging tasks due to their dynamically changing shapes and motions. This paper proposes a new algorithm to achieve automatic cell tracking in time-lapse microscopy macrophage data. First, we design a segmentation method employing space-time filtering, local Otsu's thresholding, and the SUBSURF (subjective surface segmentation) method.

Metastatic recurrence in colorectal cancer arises from residual EMP1 cells.

Around 30-40% of patients with colorectal cancer (CRC) undergoing curative resection of the primary tumour will develop metastases in the subsequent years. Therapies to prevent disease relapse remain an unmet medical need. Here we uncover the identity and features of the residual tumour cells responsible for CRC relapse.

Macrophages undergo a behavioural switch during wound healing in zebrafish.

In response to wound signals, macrophages are immediately recruited to the injury where they acquire distinct phenotypes and functions, playing crucial roles both in host defense and healing process. Although macrophage phenotypes have been intensively studied during wound healing, mostly using markers and expression profiles, the impact of the wound environment on macrophage shape and behaviour, and the underlying mechanisms deserve more in-depth investigation. Here, we sought to characterize the dynamics of macrophage recruitment and behaviour during aseptic wounding of the caudal fin fold of the zebrafish larva.

Damage-Induced Calcium Signaling and Reactive Oxygen Species Mediate Macrophage Activation in Zebrafish.

Immediately after a wound, macrophages are activated and change their phenotypes in reaction to danger signals released from the damaged tissues. The cues that contribute to macrophage activation after wounding are still poorly understood. Calcium signaling and Reactive Oxygen Species (ROS), mainly hydrogen peroxide, are conserved early wound signals that emanate from the wound and guide neutrophils within tissues up to the wound.

Pseudomonas aeruginosa OprF plays a role in resistance to macrophage clearance during acute infection.

While considered an extracellular pathogen, Pseudomonas aeruginosa has been reported to be engulfed by macrophages in cellular and animal models. However, the role of macrophages in P. aeruginosa clearance in vivo remains poorly studied.

Pro-resolving mediator protectin D1 promotes epimorphic regeneration by controlling immune cell function in vertebrates.

Background And Purpose: Specialized pro-resolving mediators (SPMs) are a family of lipids controlling the resolution of inflammation and playing a role in many processes including organ protection and tissue repair. While SPMs are potent bioactive molecules in vivo, their role in epimorphic regeneration of organs in vertebrates has not been tested. Using the zebrafish larva as a robust regenerative vertebrate system, we studied the role of the SPM neuroprotectin/protectin D1 (PD1) during the caudal fin fold regeneration.

Neutrophils use superoxide to control bacterial infection at a distance.

Understanding the roles of neutrophils and macrophages in fighting bacterial infections is a critical issue in human pathologies. Although phagocytic killing has been extensively studied, little is known about how bacteria are eliminated extracellularly in live vertebrates. We have recently developed an infection model in the zebrafish embryo in which leukocytes cannot reach the injected bacteria.