Developing a pro-regenerative biomaterial scaffold microenvironment requires T helper 2 cells

Muscle injuries and strategies for improving their repair

Satellite cells are tissue resident muscle stem cells required for postnatal skeletal muscle growth and repair through replacement of damaged myofibers. Muscle regeneration is coordinated through different mechanisms, which imply cell-cell and cell-matrix interactions as well as extracellular secreted factors. Cellular dynamics during muscle regeneration are highly complex. Immune, fibrotic, vascular and myogenic cells appear with distinct temporal and spatial kinetics after muscle injury. Three main phases have been identified in the process of muscle regeneration; a destruction phase with the initial inflammatory response, a regeneration phase with activation and proliferation of satellite cells and a remodeling phase with maturation of the regenerated myofibers. Whereas relatively minor muscle injuries, such as strains, heal spontaneously, severe muscle injuries form fibrotic tissue that impairs muscle function and lead to muscle contracture and chronic pain. Current therapeutic approaches have limited effectiveness and optimal strategies for such lesions are not known yet. Various strategies, including growth factors injections, transplantation of muscle stem cells in combination or not with biological scaffolds, anti-fibrotic therapies and mechanical stimulation, may become therapeutic alternatives to improve functional muscle recovery.

Immunity by equilibrium

The classical model of immunity posits that the immune system reacts to pathogens and injury and restores homeostasis. Indeed, a century of research has uncovered the means and mechanisms by which the immune system recognizes danger and regulates its own activity. However, this classical model does not fully explain complex phenomena, such as tolerance, allergy, the increased prevalence of inflammatory pathologies in industrialized nations and immunity to multiple infections. In this Essay, I propose a model of immunity that is based on equilibrium, in which the healthy immune system is always active and in a state of dynamic equilibrium between antagonistic types of response. This equilibrium is regulated both by the internal milieu and by the microbial environment. As a result, alteration of the internal milieu or microbial environment leads to immune disequilibrium, which determines tolerance, protective immunity and inflammatory pathology.

Inhibition of eosinophils degranulation by Ketotifen in a patient with milk allergy, manifested as bronchial asthma--an electron microscopic study

Electron microscopic studies provided evidence that a patient with cow's milk allergy, manifested as bronchial asthma, has prominent eosinophil granule discharge, attributable to the release of cytotoxic major basic protein (MBP). This finding illustrates a critical role of eosinophil MBP in anaphylactic injury induced by food allergen. Patient white blood cells pretreated with Ketotifen revealed intact ultrastructure of eosinophils granules and cytoplasm. Inhibition of eosinophils degranulation by Ketotifen demonstrates a new pharmacologic mode of action of this anti-allergic, anti-anaphylactic agent.