Skin biology
The rooms peptides walk into
Layers, fibroblasts, matrix, oxidative stress, aging clocks, wound literature. Read this if the encyclopedia names start to blur.
Architecture
Skin layers
Epidermis, dermis, hypodermis — three layers with different jobs. Peptides only make sense once you know which layer they are even talking to.
The writing room
The dermis
If epidermis is the wall, dermis is the timber frame. Most of the encyclopedia’s signal peptides are aimed at the cells that build that frame.
The authors
Fibroblasts
The dermal cell that writes matrix. Most signal peptides are fan mail addressed to this cell.
The sentence they write
Extracellular matrix
Collagen, elastin, fibronectin, laminins, hyaluronic acid — the dermis is a material, not a void.
The memo
Collagen signaling
Cells do not see a bottle. They see concentration, fragments, TGF-β, copper, stretch. This is the pathway most signal peptides are trying to join.
The molecule
What a peptide is
Short chains of amino acids. In cosmetics they are signals, carriers, enzyme decoys, or — sometimes — just a word on a box.
The rust
Oxidative stress
UV, pollution, and metabolism make reactive oxygen. Antioxidant enzymes — some copper-dependent — are how tissue answers.
Several clocks
Skin aging pathways
Photoaging, intrinsic aging, immune aging, glycation, nuclear-lamina drift. No single peptide sits on all of them.
The original literature
Wound healing
GHK-Cu’s first reputation was not a serum. It was tissue repair. Knowing that history keeps the cosmetic claims in their lane.