Peptides and skin healing: what the studies show for laser, microneedling and surgery

A controlled wound is a healing model

Ablative laser resurfacing, microneedling and any surgical incision are planned wounds. What dermatologists and plastic surgeons want from them is exactly what repair biology studies: fast re-epithelialization, good perfusion, orderly collagen and a scar that does not show. Three peptides in the catalog account for most of that literature: thymosin β4 and its fragment TB-500, BPC-157 and GHK-Cu, which are combined in the GLOW blend.

One rule runs through this article: every finding is attributed to the molecule its study used. Two molecules are sold under the name TB-500, the Ac-LKKTETQ fragment (short chain) and full-length 43-amino-acid thymosin β4 (long chain), and almost all of the literature, including every human trial, concerns the full protein. The difference is explained in TB-500 is not thymosin beta-4; the logic of combining the three peptides, in GLOW, KLOW and Wolverine.

Thymosin β4: more epithelium and a finer scar in animals

Full-length thymosin β4. In a rat full-thickness wound model, the protein given topically or intraperitoneally increased re-epithelialization by 42% over saline at day 4 and by as much as 61% at day 7; wounds contracted at least 11% more and showed more collagen and more vessels¹. In vitro, as little as 10 pg increased keratinocyte migration 2- to 3-fold¹. In db/db diabetic mice it increased contraction and collagen deposition, and in 26-month-old mice, whose healing was significantly delayed, it accelerated repair².

LKKTETQ fragment. In the same study, the synthetic heptapeptide LKKTETQ, which reproduces the actin-binding domain, promoted repair in the aged mice comparable to that of the full protein². It is the sequence of short-chain TB-500, but without the N-terminal acetylation, and it is the main published in-vivo skin finding for the fragment.

The finding closest to aesthetic concerns is the incision work. In rats, incisional wounds treated locally with full-length thymosin β4 healed with minimal scarring, were narrower and lost no breaking strength; they had more organized, mature collagen and few myofibroblasts³. For surgeons who do fat grafting there is an in-vitro finding: in adipose-derived stem cells from liposuction patients, thymosin β4 at 100 and 1000 ng/mL increased proliferation and resistance to apoptosis⁴.

From animal to patient: the thymosin β4 gel trials

Of the molecules in this article, full-length thymosin β4 has the broadest clinical program in skin wounds: three phase 2 trials of a RegeneRx topical gel (RGN-137 in the venous trial record). In venous ulcers, a phase 2 trial at eight European sites randomized 73 patients: safety was comparable to placebo, the 0.03% concentration suggested possible acceleration, and about 25% of patients achieved complete closure within 3 months⁵. The registry results show wounds closed at day 84 in 12 of 55 patients on thymosin β4 vs 4 of 17 on placebo⁶. In pressure ulcers (72 patients), the figures were 8 of 54 vs 3 of 18⁷.

In epidermolysis bullosa, the trial was stopped early for "Lack of patient availability and expiration of study drug": 30 of the 36 planned participants were randomized⁸. Wounds closed in 8 of 22 patients on thymosin β4 and 5 of 8 on placebo, with no significant difference; there was one adverse event in the active group and no serious ones⁸. The program's investigators highlight another angle: among patients who did heal, thymosin β4 accelerated closure by almost a month in the venous and pressure ulcer trials⁹.

BPC-157 in skin: CO2 laser, burns and diabetic wounds

The finding most directly relevant to aesthetic practice is a Zagreb group study with CO2 laser: in mice with dorsal laser injuries, a neutral cream with BPC-157 applied once daily consistently improved healing, macroscopically and microscopically, assessed at days 1, 7 and 21¹⁰. In deep partial-thickness burns covering 20% of body surface, the cream reduced edema, inflammatory cells and necrosis, increased capillaries and collagen fibers, preserved more follicles, reversed the poor re-epithelialization of controls at two weeks and increased the breaking strength of burned skin; silver sulfadiazine only increased collagen and reduced inflammatory cells¹¹. The peptide also counteracted the healing delay induced by methylprednisolone¹².

Two papers from other laboratories point the same way. In hyperglycemic rats, BPC-157 gel (as PL 14736) produced a dose-dependent acceleration of excisional wound healing, equivalent at the highest doses to becaplermin (PDGF-BB), a standard therapy for diabetic foot ulcers, with a trend toward more granulation tissue containing mature collagen than becaplermin¹³. A group in Xi'an, China, observed faster closure and more collagen at day 18 in alkali burns in rats, with increased VEGF in the wound and regulation of the ERK1/2 pathway¹⁴. Tendon and gut studies are reviewed in BPC-157 in the laboratory.

GHK-Cu: matrix, ischemia and microneedles

In wound chambers implanted in rats, GHK-Cu injections produced a concentration-dependent increase in collagen, glycosaminoglycans, DNA and protein; type I and III collagen mRNAs rose, and a control tripeptide had no effect¹⁵. In open wounds within an ischemic flap, the topical gel reduced initial area by 64.5% at day 13, vs 45.6% with vehicle and 28.2% untreated, with less TNF-α, MMP-2 and MMP-9¹⁶. In previously irradiated skin flaps, by contrast, there were no differences in ischemia, vessel number or VEGF¹⁷.

For microneedling, the available data concern penetration, not efficacy: in human skin in vitro, 134 ± 12 nanomoles of peptide and 705 ± 84 nanomoles of copper crossed microneedle-pretreated skin in 9 hours, vs almost none through intact skin, with no obvious signs of irritation in the safety models¹⁹. The only human trial after CO2 laser (13 patients) found no objective differences in erythema or wrinkles, although satisfaction was higher with GHK-Cu (P = 0.04)¹⁸. The other topical trials are in GHK-Cu: four decades of papers, few trials.

Hypertrophic scars and keloids

We found no peptide trials in keloids or hypertrophic scars, but there are laboratory signals. In keloid tissue, thymosin β4 mRNA was 66.98% lower than in hypertrophic scar and 62.48% lower than in normal skin; the authors propose that its insufficient expression may contribute to keloid formation²¹. In human dermal fibroblasts, GHK and GHK-Cu at 1 nM reduced IGF-2-induced TGF-β1 secretion, although free copper did the same²⁰. Together with the fewer myofibroblasts in thymosin β4-treated incisions³, these are coherent hypotheses that no one has tested in patients. The antimicrobial peptide LL-37, with two venous ulcer trials, is reviewed in LL-37 and antimicrobial peptides.

Where the evidence ends

• Almost everything is animal or in vitro. The full-length thymosin β4 gel trials did not clearly separate from placebo in the number of closed wounds⁶⁷⁸, and the GHK-Cu trial after CO2 laser showed no objective benefit¹⁸.
• For the LKKTETQ fragment there is a single in-vivo skin finding, in mice, and without the acetylation of commercial TB-500².
• The BPC-157 skin literature comes mainly from the Zagreb group¹⁰¹¹¹²; outside replication exists but is scarce¹³¹⁴.
• GHK-Cu results depend on the model: positive in rat ischemic wounds and null in irradiated skin¹⁶¹⁷.
• We found no published studies of the GLOW blend and no human trials of these peptides injected in aesthetic procedures.