Four Phases of Healing
A wound heals in overlapping stages, and peptide signals orchestrate each handover.
Stop 1 of 10 on the Repair Line.
Healing looks like one process from the outside, but it is a relay of four phases that overlap. Each hands over to the next through chemical signals, many of them peptides and small proteins.
1. Hemostasis (minutes)
Platelets plug the break and a fibrin mesh forms a clot. The platelets also release growth factors, including PDGF (platelet-derived growth factor), which call in the next wave of cells.
2. Inflammation (hours to a few days)
Immune cells arrive to clear bacteria and debris. Signals such as cytokines and chemokines guide them. This phase is necessary, but when it does not end, wounds stall.
3. Proliferation (days to weeks)
New tissue forms. Fibroblasts lay down collagen, new blood vessels grow under the influence of VEGF, and skin cells at the edges migrate to close the surface. EGF and FGF families of growth factors drive much of this.
4. Remodeling (weeks to months or longer)
Collagen is reorganized and cross-linked, and the scar gains strength. Even a mature scar does not reach the strength of unwounded skin.
What is used in medicine
Only a few growth-factor-based products have regulatory approval for wounds. Becaplermin, a topical PDGF gel, was approved for diabetic foot ulcers, and its use carries labeling restrictions. Many other candidates have shown promise in animals and then underperformed in human trials, partly because the wound environment is hostile to peptides, full of enzymes that break them down.
The takeaway
When a product claims to "speed healing", ask which phase it acts on. A signal that helps in phase three could be useless, or even unhelpful, if applied in phase two. Timing and context run through all of repair biology.
End of this stop
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Education only, not medical advice. See the service notice.