Microgravity effects and aging physiology: similar changes or common mechanisms?

Abstract

Despite the use of preventive measures (including intense physical activity), cosmonauts and astronauts develop muscle atony and atrophy, insufficiency of the cardiovascular system, osteopenia, etc. All these changes, reminiscent of age-related physiological changes, occur in a healthy person in microgravity quite quickly - within a few months. Adaptation to the absence of gravity leads to the symptoms of aging, which are compensated after returning to Earth. The prospect of interplanetary flights raises the question of gravity thresholds, below which the main physiological systems will lose their functional potential, similar to aging, and affect life expectancy. An important role in the aging process belongs to the body’s cellular reserve - progenitor cells, which are involved in physiological remodeling and regenerative/reparative processes of all physiological systems. With age, progenitor cell count and the regenerative potential decreases. Moreover, their paracrine spectrum becomes pro-inflammatory during replicative senescence, disrupting tissue homeostasis. Mesenchymal stem/stromal cells (MSCs) are mechanosensitive, and therefore the absence of a gravitational stimulus causes serious changes in their functional status. The review compares the cellular effects of microgravity and changes developing in senescent cells, including stromal precursors.