Blood aging: From definition and mechanisms to clinical practice

It is generally believed that hematopoietic aging is a major driver or contributor of human aging. The hematopoietic system undergoes physiological or pathological changes with aging, which drive or contribute to the aging of almost all systems and organs in the body, leading to various age-related diseases, particularly malignant and non-malignant hematologic disorders. Although the term blood aging has been mentioned in a number of publications and is widely used in everyday life, its definition and research scope remain unclear to date. With the rapid advances in the aging research field involving overall, systemic/organ, cellular, and molecular aging, various aspects relevant to blood aging have permeated almost all areas of aging research, including hematopoietic stem/progenitor cell (HSC/HPC) aging, immunosenescence, inflammaging, etc. However, sharply contrasting with aging of other systems and organs, blood aging has not yet formed its own research field. This review article discusses the definition, scope, and mechanisms of blood aging and provides a comprehensive overview on this emerging area, encompassing physiological and pathological blood aging. Overall, this review aims to advance understanding of blood aging, clarify its definition and scope, and highlight underlying mechanisms, thereby providing a foundation for future research and strategies to promote healthy aging.