This review proposes a tripartite regulatory framework for the Skin Extracellular Microenvironment
(SEM), which the authors conceptualize as three cross-talked functional domains: hydration,
nutritional, and signaling microenvironments. It systematically elaborates on the core functional
architectures of each component—for instance, Hyaluronic Acid (HA) as the foundational
element of the hydration microenvironment, collagen-based transport pathways in the nutritional
microenvironment, and multi-axis signal networks (inflammatory, biochemical, mechanical) in the
signaling microenvironment. Based on this, age-related dynamic alterations within each domain
were further delineated: the hydration microenvironment undergoes progressive HA degradation
and reduced biosynthesis, leading to decreased skin water retention, increased transepidermal water
loss, and clinical manifestations like dryness and fine lines; the nutritional microenvironment exhibits
microvascular degeneration, disrupted nutrient transport, and advanced glycation end-product
accumulation, impairing extracellular matrix metabolic homeostasis; the signaling microenvironment
suffers from chronic inflammation, TGF- /Smad pathway imbalance, and mechanical signaling
dysfunction, triggering a cascade of "inflammatory activation uncontrolled degradation
mechanical disruption." Cross-regulatory interactions among the three microenvironments (e.g.,
hydration-signaling coupling via TGF- /HAS2) are summarized to highlight their integrated regulatory
nature. Additionally, targeted anti-aging strategies are discussed: exogenous HA supplementation
and endogenous activation for the hydration microenvironment, metabolic substrate supply
(e.g., proline, trace elements) for the nutritional microenvironment, and multi-pathway modulation
(e.g., anti-inflammatory agents, platelet-rich plasma, collagen stimulants) for the signaling microenvironment,
with particular attention to the synergistic effects observed in combination approaches
such as mesotherapy-based cocktails and exosome therapy. Overall, this framework integrates previously
fragmented SEM research and provides a coherent theoretical basis for evidence-based clinical
anti-aging strategies and future precision interventions targeting skin aging.