669 Senescence-associated secretion of vesicular miR-23a-3p and its impact during the paracrine crosstalk of dermal and epidermal cells

The chronic accumulation of senescent cells with age and their development of a senescence-associated secretory phenotype (SASP) is thought to be one of the main contributors of age-associated skin deterioration. It is characterized by the secretion of pro-inflammatory cytokines and extracellular matrix remodeling enzymes among others that impair tissue homeostasis, while their transient presence enhances regeneration and wound healing. Recently, we identified miRNAs enclosed in extracellular vesicles (EV) as novel members of the SASP, which we termed ‘miR-SASP’. In the present study we aim to evaluate the vesicular crosstalk between dermal and epidermal cells and assessed the impact of the HDF derived miR-SASP on primary epidermal keratinocytes (NHEK). We confirmed the transfer of EV-miRNAs derived from HDF to NHEK in monolayers and in human skin equivalents and verified the presence of EVs in human skin sections by TEM. While the transient incubation with EVs derived from senescent HDF ameliorated the wound healing capacity of NHEK, we observed an impaired differentiation potential after long-term exposure. Finally, we identified the highly secreted miR-23a-3p as a crucial mediator of the miR-SASP by an enhanced healing capacity after its overexpression in NHEK. To summarize, we here uncovered the age-related contribution of EV-enclosed miRNAs and their impact on NHEK functionality in vitro. The consequence of senescence-associated EV-miRNAs in human skin equivalents and in vivo remains to be investigated.