The emerging role of miRNAs in biological aging and age-related diseases.

Ageing is a complex biological process characterised by the accumulation of molecular and cellular damage leading to functional decline and an increased risk of chronic disease and geriatric syndromes. Despite data showing that lifestyle modifications, such as caloric restriction and exercise, can lead to healthy ageing and greatly reduce the incidence of chronic disorders, no medical therapies exist to delay or prevent these conditions effectively. We also lack tools to effectively track the ageing process in a manner that predicts an individual's risk of chronic disease and assess response to lifestyle or medical interventions. This review explores the emerging role of microRNAs (miRNAs), which are small non-coding RNAs that regulate gene expression, as a unifying mechanism underlying the biology of ageing and age-related conditions, including cardiovascular and neurodegenerative diseases, metabolic syndromes, musculoskeletal disorders such as sarcopenia, osteoarthritis and osteoporosis, and various cancers. We also examine the interactions of miRNAs with various hallmarks of ageing, such as DNA damage, cellular senescence, and mitochondrial dysfunction. We then explore the challenges of translating miRNA-based approaches from preclinical promise to clinical utility, emphasizing the need for trial-level validation to correlate miRNA profiles with clinically meaningful, patient-centred endpoints. By consolidating these findings, this article puts miRNAs forward as a pivotal mechanism in geroscience, offering a novel framework to mitigate ageing-related multimorbidity and bridge the gap between lifespan and healthspan.