Abstract
During tissue injury events, the innate immune system responds immediately to alarms sent from the injured cells, and the adaptive immune system subsequently joins in the inflammatory reaction. The control mechanism of each immune reaction relies on the orchestration of different types of T cells and the activators, antigen-presenting cells, co-stimulatory molecules, and cytokines. Mitochondria are an intracellular signaling organelle and energy plant, which supply the energy requirement of the immune system and maintain the system activation with the production of reactive oxygen species (ROS). Extracellular mitochondria can elicit regenerative effects or serve as an activator of the immune cells to eliminate the damaged cells. Recent clarification of the cytosolic escape of mitochondrial DNA triggering innate immunity underscores the pivotal role of mitochondria in inflammation-related diseases. Human mesenchymal stem cells could transfer mitochondria through nanotubular structures to defective mitochondrial DNA cells. In recent years, mitochondrial therapy has shown promise in treating heart ischemic events, Parkinson’s disease, and fulminating hepatitis. Taken together, these results emphasize the emerging role of mitochondria in immune-cell-mediated tissue regeneration and ageing.
Highlights
Organ injuries require tissue repair and regeneration, while subtle tissue injury leads to macrophage activation, and fibroblast or stromal cell proliferation, such as plaque formation in atherosclerosis
We focus on the role of immune cells in various tissue stages, from inflammation, through repair and regeneration, to tissue proliferation, with an emphasis on the emerging role of mitochondria in immune-cell-mediated tissue regeneration and ageing
Ageing in the immune system occurs in a similar manner as in other organ systems, and several phenotypic and molecular hallmarks of ageing are exhibited in immune cells, including decreased MHC II expression, decreased antibody production, altered toll-like receptor expression, limited diversity in B cell receptor repertoire, and restricted diversity in the T cell receptor repertoire [41]
Summary
Organ injuries require tissue repair and regeneration, while subtle tissue injury leads to macrophage activation, and fibroblast or stromal cell proliferation, such as plaque formation in atherosclerosis. Unhindered tissue regeneration, occurring under unknown mechanisms, leads to tissue proliferation, which could further cause unwanted insults, such as fibrosis in ageing. Both innate and adaptive immunity against environmental stimulus needs energy supplies. The mitochondrion has an indispensable role in the development and function of immune cells, from energy supply to the activation, proliferation, and phagocytosis, and ending with repairs and regeneration. With the help of mitochondrial reactive oxygen species (ROS), the immune cells execute complex functions, such as apoptosis, pyroptosis, netosis, and adaptive immunity activation. We focus on the role of immune cells in various tissue stages, from inflammation, through repair and regeneration, to tissue proliferation, with an emphasis on the emerging role of mitochondria in immune-cell-mediated tissue regeneration and ageing
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