Aging and Altered Gravity: A Cellular Perspective.

The elderly and astronauts exhibit strikingly similar phenotypes. Although much research has addressed the comparison between these two groups at the level of the whole organism or organ level, like the musculoskeletal system, comparative studies at the cellular level remain limited. Therefore, this article aims to address this gap by conducting an extensive scoping review, comparing cell function and alterations with advanced age to those observed in altered gravity. The broad review spans different cell types and species, highlighting the generic nature of aging and its relationship to gravity. We identified 165 signs of aging at the cell level, deducted from leading aging papers, and grouped them into 11 themes: DNA and epigenetics, mitochondria, nucleus, immune system, protein and metabolism, lysosome and degradation, cell cycle, cytoskeleton, extracellular matrix (ECM), cell mechanics, and cell signaling. Following this classification, we conducted a comprehensive search using the databases Web of Science and PubMed to examine the behavior of these signs in altered gravity conditions. The results reveal that only 29% of the responses are similar in (simulated) microgravity compared to biological aging, while others show contrasting behavior, thereby highlighting the complexity of cellular responses in these conditions. However, the majority of the signs remain unexplored in altered gravity. Mechanotransduction emerges as a potential key player in the observed phenotypic resemblances between aging and microgravity. Since there still is quite a lack of knowledge of aging-related effects on a cellular level in gravity-related research, we recommend further gravity research on the many components making up the links that facilitate mechanotransduction, which can aid in understanding the origins of these shared phenotypes and could lead to new insights into age-related and space-induced health challenges.