Physiological Mechanisms of Paracrine Signaling in Tissue Aging and Repair

Review Article

Abstract

Cellular senescence is a fundamental physiological mechanism characterized by stable cell cycle arrest coupled with a hyperactive secretory metabolism. While historically viewed merely as a mechanism to prevent tumorigenesis, the accumulation of senescent cells acts as a primary driver of organismal aging and tissue dysfunction. The Senescence-Associated Secretory Phenotype (SASP) constitutes the functional output of these cells, mediating autocrine and paracrine signaling through a complex secretome of cytokines, chemokines, growth factors, and matrix metalloproteinases. The physiological cascade initiating the SASP requires the integration of nuclear DNA damage signals and mitochondrial metabolic perturbations, culminating in the activation of cytosolic DNA sensing pathways such as cGAS-STING. Functionally, these paracrine signals exhibit antagonistic pleiotropy: acute expression facilitates wound healing, tissue remodeling, and tumor suppression, whereas chronic persistence fundamentally disrupts the tissue microenvironment. This pathological shift drives chronic low-grade inflammation, induces secondary senescence in neighboring cells via the bystander effect, and overwhelms immune clearance mechanisms. The molecular regulation of the SASP provides the mechanistic basis for age-related physiological decline and emphasizes the secretome as a critical target for therapeutic intervention to extend healthspan