An ageing global population brings with it a significant burden of age-related morbidities. Recently, a novel intervention strategy to mitigate this burden has emerged, involving the use of Extracellular Vesicles (EV), comprising use of Microvesicles (MV) and Exosomes (Exo). These membranous vesicles are secreted by cells and mediate repair of cellular and tissue damage via paracrine mechanisms, involving interaction of their bioactive cargoes with stem cells. The actions of EV under normative and morbid conditions in the context of ageing remains largely unexplored. We now show that MV, but not Exo, from Pathfinder cells (PC), a putative stem cell regulatory cell type, enhance the repair of Human Dermal Fibroblast (HDF) and Mesenchymal Stem Cell (MSC) co-cultures following both mechanical and genotoxic stress. Critically, this effect was found to be both cellular age and stress-specific. Notably, MV treatment was unable to repair mechanical injury in older co-cultures, but still remained therapeutic following genotoxic stress. These observations were further confirmed in HDF and Vascular Smooth Muscle Cell (VSMC) co-cultures of increasing cellular age. In a model of comorbidity, comprising co-cultures of HDF and highly senescent Abdominal Aortic Aneurysm (AAA) VSMC, MV administration appeared to be senolytic following both mechanical and genotoxic stress, prior to enabling regeneration. To our knowledge, this is the first description of EV-based senolysis. It provides novel insight into understanding the biology of EV and the specific roles they play during tissue repair and ageing. These data will potentiate development of novel cell-free therapeutic interventions capable of attenuating age-associated morbidities and avoiding undesired effects. Ultimately, this might act as a possible intervention strategy to extend human healthspan.

Extracellular vesicles (EVs), comprising microvesicles (MVs) and exosomes (Exos), are membranous vesicles secreted by cells which mediate the repair of cellular and tissue damage via paracrine mechanisms. The action of EVs under normative and morbid conditions in the context of ageing remains largely unexplored. We demonstrate that MVs, but not Exos, from Pathfinder cells (PCs), a putative stem cell regulatory cell type, enhance the repair of human dermal fibroblast (HDF) and mesenchymal stem cell (MSC) co-cultures, following both mechanical and genotoxic stress. Critically, this effect was found to be both cellular age and stress specific. Notably, MV treatment was unable to repair mechanical injury in older co-cultures but remained therapeutic following genotoxic stress. These observations were further confirmed in human dermal fibroblast (HDF) and vascular smooth muscle cell (VSMC) co-cultures of increasing cellular age. In a model of comorbidity comprising co-cultures of HDFs and highly senescent abdominal aortic aneurysm (AAA) VSMCs, MV administration appeared to be senotherapeutic, following both mechanical and genotoxic stress. Our data provide insights into EVs and the specific roles they play during tissue repair and ageing. These data will potentiate the development of novel cell-free therapeutic interventions capable of attenuating age-associated morbidities and avoiding undesired effects.