Senescent-like border-associated macrophages regulate cognitive aging via migrasome-mediated induction of paracrine senescence in microglia.

Aging is a major risk factor for various neurological disorders, including Alzheimer's disease, and is associated with the accumulation of senescent cells, which can themselves propagate the senescence process through paracrine signaling. Migrasomes are organelles that form during cellular migration, detach from parent cells and mediate intercellular communication. Here we demonstrate that border-associated macrophages (BAMs) acquire senescence-associated properties during early brain aging, possibly due to prolonged exposure to amyloid beta. Senescent-like BAMs show elevated production of migrasomes, which convey senescence-associated signals including the apoptosis inhibitor of macrophage to neighboring cells. We show that microglia are prominent recipients of senescent-like BAM-derived migrasomes, and that through activation of CD16 in recipient cells, the apoptosis inhibitor of macrophage inhibits apoptosis and promotes senescence induction. Blocking migrasome induction in senescent-like BAMs through treatment with Tspan4-targeting siRNA-encapsulated liposomes ameliorates cognitive deficits in aged mice. Our findings suggest that migrasomes are potent vehicles of senescence-regulatory signals and represent a promising target for senomorphic therapy.