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Chronoaging versus photoaging
Distinguishing intrinsic from extrinsic aging matters because they damage the matrix through partly different molecular routes, and a peptide mechanism may be more relevant to one than the other. Intrinsic (chronological) aging is driven by time-dependent proc
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- Distinguishing intrinsic from extrinsic aging matters because they damage the matrix through partly different molecular routes, and a peptide mechanism may be more relevant to one than the other. Intrinsic (chronological) aging is driven by time-dependent processes — accumulating cellular senescence, mitochondrial decline, shortened telomeres, and a slow drop in growth-factor responsiveness — producing an atrophic dermis with reduced but relatively orderly collagen. Extrinsic aging, dominated by chronic ultraviolet exposure, drives a distinct pathology: UV generates reactive oxygen species that activate AP-1 and NF-κB, sharply inducing MMP-1, MMP-3, and MMP-9 while suppressing new procollagen synthesis. The result is solar elastosis — a build-up of abnormal, disorganised elastotic material alongside fragmented collagen. Because peptide research targets both the synthesis deficit and the degradative excess, the copper-peptide rationale is often framed as most relevant where the MMP–ROS