Tripeptide-29

Dosing from the Literature

Published for skin: nothing tested; one supplier suggests 0.1–1.0% of a product. Not published: whether it reaches live skin, or any trial of creams with it.

As a cosmetic ingredient, Tripeptide-29 has no dose in the drug sense, only a percentage of a finished product, and no trial or label gives one. One raw-material supplier's formulation guidelines suggest 0.1–1.0% (read October 2026); no study has tested any level on human skin.

What It Is

Tripeptide-29 is the International Nomenclature of Cosmetic Ingredients (INCI) name for a synthetic peptide of glycine, proline and hydroxyproline, as the EU's CosIng register defines it. PubChem lists it as Gly-Pro-Hyp (glycine, L-proline, trans-4-hydroxy-L-proline; CAS Registry Number 2239-67-0), with the formula C₁₂H₁₉N₃O₅ and a molecular weight of about 285.3 daltons.

The biological rationale for Tripeptide-29 begins with the structure of native collagen. Collagen — the most abundant protein in the human body and the dominant structural component of dermis, tendon, ligament, bone, and cartilage — is built from polypeptide alpha chains organized as a repeating Gly-X-Y triplet, where X is most often proline and Y is most often 4-hydroxyproline. Surveys of the collagen sequence database show that of the more than 400 possible Gly-X-Y triplets, only a limited subset appear in significant numbers, and Gly-Pro-Hyp is the single most abundant triplet across fibrillar collagens. Gly-Pro-Hyp is, in a literal sense, the minimal repeating signal unit of mature collagen architecture.

In cosmetic formulation, the Tripeptide-29 thesis is matrikine (a signaling fragment from broken-down skin matrix) signaling: small collagen-derived fragments that escape complete proteolytic clearance can engage cell-surface receptors on dermal fibroblasts and signal a "tissue-needs-collagen" state, prompting fibroblasts to ramp up procollagen synthesis. The classical matrikine literature, established for fragments such as the C-terminal nonapeptide (a chain of 9 amino acids) of type IV collagen and the famous palmitoyl-pentapeptide-4 (Matrixyl) sequence Lys-Thr-Thr-Lys-Ser, frames small collagen fragments as endogenous wound-healing signals. Tripeptide-29 is positioned within this framework as the minimal, most-conserved collagen fragment carrier of that signal.

Tripeptide-29 differs from several adjacent ingredients. It is not a hydrolyzed collagen, although hydrolyzed collagen contains Gly-Pro-Hyp among many other peptides. It is not Pro-Hyp, the dipeptide (a chain of 2 amino acids) collagen-fragment that has accumulated the most direct fibroblast (a cell that builds collagen) in vitro evidence. It is not palmitoyl-tripeptide-1, palmitoyl-tripeptide-5, or any of the lipidated tripeptide derivatives that travel under "Tripeptide" naming with different sequences. It is not collagen tripeptide hydrolysates (CTPs), which are mixtures of small peptides enriched in Gly-Pro-Hyp but not pure Gly-Pro-Hyp. On an ingredient label, "Tripeptide-29" names synthetic Gly-Pro-Hyp alone (CosIng; PubChem); other "tripeptide" names are different molecules with different evidence.

As a cosmetic ingredient, Tripeptide-29 sits in an unusual evidence gap. The mechanistic primary literature on Gly-Pro-Hyp is reasonably substantial — absorption studies, fibroblast culture studies, structural biology of the collagen triple helix, and wound-healing studies all reference the GPH triplet. PubMed returns no record for the name Tripeptide-29 and lists no randomized controlled trial of a cream with it as the named active ingredient. This profile attempts to honestly bridge that gap.

Mechanism of Action

The mechanistic claims for Tripeptide-29 in topical cosmetics are extrapolated from three converging streams of evidence: structural biology of native collagen, in vitro fibroblast pharmacology of small collagen-derived peptides, and the broader matrikine-signaling literature. None of these streams was generated by applying Tripeptide-29 to human skin in a controlled trial, and the leap from "Gly-Pro-Hyp does X in cell culture" to "Tripeptide-29 in a serum does X in human skin" is not trivial.

• Most-conserved collagen triplet — Gly-Pro-Hyp is the single most abundant Gly-X-Y triplet in the fibrillar collagens (types I, II, III) that dominate dermal extracellular matrix. The 1998 Gly-X-Y frequency analysis (Ramshaw, Shah, Brodsky, J Struct Biol; PMID 9724608) established that of the >400 theoretically possible Gly-X-Y combinations, a small set predominate, with Gly-Pro-Hyp at the top.
• Triple-helix stabilizer — In collagen-mimetic peptide research, repeats of Gly-Pro-Hyp form the stable "host" triple helix into which other triplets are placed to measure how each changes the helix's stability (Ramshaw et al., 1998).
• Plasma appearance after oral collagen ingestion — After 8 healthy volunteers drank 5 g of collagen hydrolysate, Gly-Pro-Hyp peaked in their plasma at about 0.1 nmol/mL, on average about 50 minutes later, against about 12 nmol/mL for Pro-Hyp (Taga et al., 2022). In a 2005 study, hydroxyproline-containing peptides, mostly Pro-Hyp, peaked at 20–60 nmol/mL 1–2 hours after people took 9.4–23 g of gelatin hydrolysate (Iwai et al., 2005, PMID 16076145). In rats, Gly-Pro-Hyp from a collagen tripeptide preparation reached the blood intact (Sontakke et al., 2016, PMID 27573716; Yamamoto et al., 2015). This documents systemic absorption after oral intake; it does not address topical penetration.
• Resistance to plasma peptidases — Gly-Pro-Hyp and Pro-Hyp stayed intact for 2 hours in rat plasma and gut fluid, which the authors link to their absorption after oral collagen (Sontakke et al., 2016, PMID 27573716); the enzyme DPP-IV cannot cut the bond between Pro and Hyp (Hatanaka et al., 2014).
• Fibroblast proliferation signal — indirectly through Pro-Hyp — In rats given a collagen tripeptide preparation, dipeptides cut from the ends of Gly-Pro-Hyp and the other tripeptides also appeared in the blood (Yamamoto et al., 2015); Pro-Hyp is the one left when Gly-Pro-Hyp loses its glycine. In cell culture, Pro-Hyp increased the migration and growth of mouse skin fibroblasts (Shigemura et al., 2009, J Agric Food Chem 57:444) and the proliferation (1.5-fold) and hyaluronic acid synthesis (3.8-fold) of human dermal fibroblasts at 200 nmol/mL (Ohara et al., 2010, J Dermatol). Whether Gly-Pro-Hyp from a cream reaches living skin cells, intact or as Pro-Hyp, has not been shown.
• p75NTR-positive fibroblast subset — Pro-Hyp appears to selectively engage a p75 neurotrophin-receptor-positive subset of mouse skin fibroblasts (Asai et al., 2020, J Funct Foods), proposing a mesenchymal-stem-cell-like progenitor target rather than blanket fibroblast stimulation. The authors suggest Pro-Hyp acts on these cells at wound sites and has little effect on the resident fibroblasts of normal tissue.
• Type I procollagen (supplier in vitro data) — One raw-material supplier's own tests report that its Tripeptide-29 raised the procollagen I released by cultured human dermal fibroblasts over 48 hours, by 103% at 0.01% of the culture medium and by 506% at 1%. These data come from the supplier and are not peer-reviewed.
• MMP balance modulation (claimed) — Some manufacturer literature attributes a downregulation of matrix metalloproteinase 1 (MMP-1; interstitial collagenase) and matrix metalloproteinase 3 (MMP-3; stromelysin-1) to GPH exposure in fibroblasts.
• Platelet-collagen recognition (caveat) — In an entirely separate context, platelet glycoprotein VI (GPVI), the platelet collagen receptor, specifically recognizes Gly-Pro-Hyp when collagen activates platelets (Knight et al., 1999, PMID 10341844). The smallest collagen motif that activates it holds two Gly-Pro-Hyp triplets, and activation needed cross-linked triple-helical peptides (Smethurst et al., 2007); Tripeptide-29 is a single triplet.
• Topical penetration — the biggest open question — At 285 Da, Tripeptide-29 is below the often-cited 500-Da limit above which molecules generally cannot easily cross the stratum corneum (Aldag et al., 2016). Manufacturers therefore claim adequate penetration for dermal fibroblast engagement. There is, however, no peer-reviewed Franz-cell or in vivo human skin-permeation study published for Tripeptide-29 specifically. Whether topically applied GPH actually reaches viable epidermal layers and the papillary dermis at meaningful concentrations is, for now, an extrapolation from molecular weight rather than a measured fact.
• Bottom line on mechanism — Gly-Pro-Hyp reaches human plasma after oral collagen (Taga et al., 2022), and Pro-Hyp, its breakdown product, acts on skin fibroblasts in culture (Shigemura et al., 2009; Ohara et al., 2010). The leap to "topical Tripeptide-29 in a serum upregulates dermal collagen synthesis in human skin" is not supported by direct evidence; it is supported by mechanistic plausibility and analogy.

What the Research Shows

Tripeptide-29's research base is unusual: the underlying molecule (Gly-Pro-Hyp) has substantial primary biochemistry, biophysics, and absorption literature, but the finished cosmetic ingredient has essentially no peer-reviewed clinical trial literature in human skin. This section separates the two cleanly.

• Gly-Pro-Hyp absorption — Iwai 2005 — The pivotal study by Iwai and colleagues (Iwai et al., J Agric Food Chem, 2005; PMID 16076145) demonstrated that ingestion of 9.4–23 g of gelatin hydrolysate in healthy humans produces transient elevations of hydroxyproline-containing peptides in peripheral plasma reaching 20–60 nmol/mL within 1–2 hours. Identified peptide species included Pro-Hyp (the dominant constituent), Ala-Hyp, Ala-Hyp-Gly, Pro-Hyp-Gly, Leu-Hyp, Ile-Hyp, and Phe-Hyp. This established the existence of food-derived collagen peptides in human circulation as a measurable phenomenon.
• Gly-Pro-Hyp enrichment in skin — Yazaki 2017 — Yazaki et al. (J Agric Food Chem 2017; PMID 28244315) extended the Iwai work by showing that ingestion of collagen tripeptide preparations leads to plasma enrichment of Gly-Pro-Hyp specifically (not just Pro-Hyp), and that GPH and its hydrolytic product Pro-Hyp are transported to the skin in mouse models. The study identified 17 collagen-derived peptide species in plasma, with GPH the most enriched after CTP ingestion.
• Gly-Pro-Hyp / Pro-Hyp absorption pharmacokinetics — Sontakke 2016 — Sontakke et al. (PMID 27573716) characterized the enzymatic stability, intestinal permeability, and absorption of GPH and Pro-Hyp in rat models, reporting differential bioavailability of the two peptides (Pro-Hyp ~19% vs GPH ~4%) and confirming biotransformation of GPH to Pro-Hyp in vivo. Relevant for understanding what circulating species actually reaches peripheral tissue.
• Pro-Hyp fibroblast proliferation — Shigemura 2009 — Shigemura et al. (J Agric Food Chem 2009;57:444-449) demonstrated that Pro-Hyp dose-dependently increases the migration and growth of fibroblasts from mouse skin in collagen-gel culture. This is the cleanest single-paper mechanistic basis for the matrikine claim, although the active species in this assay is Pro-Hyp (the dipeptide), not GPH (the tripeptide). Subsequent work has shown some fibroblast cell lines do not respond to Pro-Hyp, complicating the "general fibroblast stimulator" narrative.
• Pro-Hyp / Hyp-Gly fibroblast verification with hydroxyprolyl-peptide-free serum — Asai et al. (Int J Mol Sci 2020, 21:229) revisited the fibroblast proliferation claim using fetal bovine serum specifically depleted of endogenous hydroxyprolyl peptides. The replication confirmed an effect in primary cultured mouse skin fibroblasts but raised concerns about prior literature that did not control for background hydroxyprolyl peptide content in standard FBS — a methodological caveat for older positive in vitro studies.
• p75NTR fibroblast specificity — Asai 2020 (J Funct Foods) — Asai and colleagues (Mouse skin fibroblasts with mesenchymal stem cell marker p75 neurotrophin receptor proliferate in response to prolyl-hydroxyproline) reported that Pro-Hyp specifically engages a small p75NTR-positive subpopulation of fibroblasts, suggesting the matrikine effect targets wound-healing progenitor cells rather than the broad fibroblast population. Relevant for re-framing the magnitude of the expected effect in normal, non-injured skin.
• Gly-X-Y collagen sequence frequency — Ramshaw 1998 — Ramshaw, Shah, and Brodsky (PMID 9724608) established the canonical Gly-X-Y triplet frequency analysis for collagen, demonstrating Gly-Pro-Hyp's dominant frequency in fibrillar collagens. This is the structural-biology paper that grounds the "GPH is the most representative collagen triplet" framing used in cosmetic marketing.
• Gly-Pro-Hyp / GPVI platelet recognition — Knight 1999 — Knight et al. (PMID 10341844) demonstrated that platelet glycoprotein VI specifically recognizes the Gly-Pro-Hyp sequence to mediate collagen-induced platelet activation. Mechanistically interesting because it confirms that there exist mammalian cell-surface receptors that distinguish GPH from related triplets (Gly-Pro-Pro, Gly-Pro-Ala, Gly-Pro-Arg) at high specificity. This receptor is platelet-restricted and not a topical-cosmetic safety concern at use levels, but it grounds the principle that GPH is a recognized signal motif.
• Broader oral collagen-peptide-hydrolysate skin literature — Proksch 2014 — Proksch et al. (Skin Pharmacol Physiol 2014;27(1):47-55; PMID 23949208) randomized 69 women aged 35–55 to 2.5 g or 5 g per day of a specific bioactive collagen peptide (Verisol) or placebo for 8 weeks. Statistically significant improvement in skin elasticity in both treatment groups versus placebo at week 8. Critical caveat: Verisol is a hydrolyzed collagen mixture (oral, ingested), not Tripeptide-29 in a topical cosmetic; the connection to Tripeptide-29 is the presence of GPH among the active species in plasma after Verisol ingestion.
• Asserin 2015 oral collagen RCT — PMID 26362110 — Asserin et al. (J Cosmet Dermatol 2015;14:291-301) ran two placebo-controlled trials on oral collagen peptide supplementation, reporting significant 8-week improvement in skin hydration and 4-week improvement in dermal collagen density and decrease in collagen fragmentation by reflectance confocal microscopy. Again, oral hydrolysate, not Tripeptide-29 — but representative of the broader collagen-peptide skin literature on which Tripeptide-29 marketing leans.
• Bolke 2019 collagen supplement RCT — PMID 31627309 — Bolke et al. (Nutrients 2019;11(10):2494) randomized to a collagen-peptide-containing nutricosmetic blend versus placebo, reporting improvement in skin hydration, elasticity, roughness, and density. Multi-ingredient formulation makes attribution to collagen peptides specifically (let alone GPH) impossible.
• Choi 2019 systematic review — PMID 30681787 — Choi et al. (J Drugs Dermatol 2019;18(1):9-16) systematically reviewed 11 randomized controlled trials of oral collagen supplementation for dermatological applications (805 total patients; 8 trials of collagen hydrolysate 2.5–10 g/day for 8–24 weeks; 2 trials of collagen tripeptide 3 g/day for 4–12 weeks; 1 trial of collagen dipeptide). Conclusion: preliminary results promising for skin elasticity and hydration; methodological quality variable; no trial in this systematic review tested topical Tripeptide-29.
• Kim 2018 LMWCP RCT (Nutrients) — Kim et al. (Nutrients 2018;10:826) tested an oral low-molecular-weight collagen peptide preparation containing >15% Gly-X-Y tripeptide content including 3% Gly-Pro-Hyp, randomized double-blind placebo-controlled in 64 subjects for 12 weeks. Improvement in skin hydration, elasticity, and wrinkling. The closest the broader literature gets to a "GPH-enriched preparation" RCT — but still oral, still a multi-component preparation, and still not topical Tripeptide-29.
• Kim 2022 LMWCP RCT — PMID 36516059 — Kim et al. (J Med Food 2022) reported a randomized double-blind placebo-controlled trial of low-molecular-weight collagen peptides for photoaged facial skin, demonstrating improvements in wrinkles, elasticity, hydration, and barrier integrity. Same caveats — oral, multi-component, not topical Tripeptide-29.
• Bauza 2004 collagen-like hexapeptide (a chain of 6 amino acids) topical — PMID 15648443 — A double-blind clinical study of a synthetic collagen-like hexapeptide (not Tripeptide-29) at 3% topical formulation versus placebo in 20 women aged 40–62 reported antiwrinkle effect on Crow's feet area. This is the closest precedent in the published literature for a "synthetic collagen-fragment topical with measured antiwrinkle effect," and it is not Tripeptide-29 — but it documents that the general approach has a non-zero probability of producing a measurable effect in human skin.

Human Data

To be unambiguous: at the time of this writing, there are no published, peer-reviewed, randomized, placebo-controlled clinical trials of finished topical cosmetic formulations containing Tripeptide-29 (Gly-Pro-Hyp) as the named active ingredient indexed in PubMed. Effect claims for Tripeptide-29 in topical cosmetics derive from three indirect evidence streams:

• Stream 1 — Oral collagen-peptide hydrolysate human RCTs. Randomized placebo-controlled trials have tested collagen hydrolysates taken by mouth for skin hydration, elasticity, density and wrinkles; the eight hydrolysate trials in a 2019 systematic review gave 2.5–10 g a day for 8–24 weeks to people with skin aging, dry skin, cellulite or pressure ulcers (Choi et al., 2019). Representative pivotal studies include Proksch 2014 (PMID 23949208), Asserin 2015 (PMID 26362110), Bolke 2019 (PMID 31627309), Kim 2018 (Nutrients 10:826), Schunck 2015 cellulite arm (PMID 26561784), Genovese 2017 (PMID 28528342), and Kim 2022 (PMID 36516059). Effect sizes are modest but reasonably consistent across multiple independent RCTs, particularly for skin elasticity and hydration. None of these trials were testing Tripeptide-29 as a finished cosmetic. They were testing oral hydrolysates that contain GPH among many other peptide species, after gut digestion and systemic absorption.
• Stream 2 — Pharmacokinetic studies of GPH in human plasma. Iwai 2005 (PMID 16076145), Yazaki 2017 (J Agric Food Chem; PMID 28244315), Sontakke 2016 (in rats; PMID 27573716), and the npj Science of Food 2022 paper on Gly-3Hyp-4Hyp (Taga 2022) document that GPH and related collagen peptides are absorbed from the gut and reach peripheral plasma after oral collagen ingestion; in the 2022 paper, GPH peaked at about 0.1 nmol/mL after 5 g of collagen hydrolysate. This documents systemic exposure, not topical penetration or dermal delivery from a cosmetic vehicle. The translation to topical use is an extrapolation, not a measurement.
• Stream 3 — Choi 2019 systematic review, oral collagen tripeptide subset. Within the Choi systematic review (PMID 30681787), two of the 11 included trials specifically tested oral "collagen tripeptide" preparations (3 g per day for 4–12 weeks) with reported improvement in skin elasticity and hydration. These trials are on enriched-tripeptide oral hydrolysates, not pure Tripeptide-29 and not topical formulations.
• Indirect topical precedent. Bauza et al. (PMID 15648443) tested a 3% topical synthetic collagen-like hexapeptide (different sequence, not Tripeptide-29) versus placebo in 20 women, reporting antiwrinkle effect at the Crow's feet area. This is the published precedent that small synthetic collagen-fragment peptides applied topically can produce measurable cosmetic outcomes in controlled studies — a precedent, not direct evidence for Tripeptide-29 specifically.
• Tangential finished-product trials. A small set of cosmetic-industry abstracts and posters describe finished products containing Tripeptide-29 alongside other actives (peptide complexes, hyaluronic acid, niacinamide, retinol) with reported subject-graded improvements over baseline. These are typically open-label, sponsor-conducted, and not peer-reviewed in PubMed-indexed journals; attribution of effect to Tripeptide-29 specifically is impossible given multi-ingredient formulations.

The honest summary: when a Tripeptide-29 marketing claim says "clinically proven," the underlying citation chain almost always traces back to (a) oral collagen-hydrolysate human RCTs that did not test the cosmetic, (b) in vitro fibroblast assays on Pro-Hyp or GPH that did not test human skin, or (c) sponsor-conducted unpublished consumer-perception studies of finished products containing many ingredients. None of those is the same thing as a peer-reviewed RCT of Tripeptide-29 in a vehicle versus the same vehicle without it. Until such a trial exists, "Limited Evidence" is the accurate characterization.

Reconstitution & Storage

Tripeptide-29 is sold to cosmetic makers as a raw material and to consumers in finished creams and serums, not as a vial to mix. No published study gives handling or storage figures for it; one raw-material supplier's documents (read October 2026) list these for its Tripeptide-29 product:

→ Calculator — vial-to-syringe math

Side Effects & Risks

No peer-reviewed safety study of Tripeptide-29 has been published, and the Cosmetic Ingredient Review (CIR) has not assessed it: its ingredient index does not list it (read October 2026). What is on record:

• Irritation and allergy (not studied in people) — PubMed lists no human patch test or case report for it. One raw-material supplier reports laboratory tests in which its Tripeptide-29 did not irritate skin or eye models, was not predicted to be a skin sensitizer (OECD 442C and 442D) and was not mutagenic (Ames test); these are the supplier's tests, not peer-reviewed.
• No systemic safety data — No safety study has tested Tripeptide-29 itself by mouth or by injection. Oral collagen supplements reported no adverse events in the placebo-controlled trials a 2019 review covered (Choi et al., 2019), and in a 12-week trial of 64 people, none reported adverse symptoms from a preparation with 3% Gly-Pro-Hyp taken at 1,000 mg a day (Kim et al., 2018); those are oral mixtures, not the pure tripeptide on skin.
• Pregnancy, breastfeeding and children — Not studied: PubMed lists no study of Tripeptide-29 in any of these groups.
• Drug interactions — Not studied.
• WADA / sport considerations — Tripeptide-29 is not specifically named on the World Anti-Doping Agency Prohibited List. As a topical cosmetic ingredient with no documented systemic absorption to plasma at meaningful concentrations from cosmetic application, it has no plausible doping relevance.

Bloodwork & Monitoring

No trial, label or guideline sets monitoring for Tripeptide-29, and no trial has tested it on skin. Oral collagen-peptide trials measured skin hydration, collagen density and collagen fragmentation with skin instruments (Asserin et al., 2015), and one ran serial blood tests and found no abnormalities (Kim et al., 2022).

Commonly Stacked With

No published study tests Tripeptide-29 with any other ingredient. To see what it is sold with, Kalios checked 50 product ingredient lists that include it (the first 50 an online ingredient database shows, October 2026; a few are two versions of one product).

Stacking this? Read the receipt →

→ Calculator — vial-to-syringe math

Legal Status

Related Compounds

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References

1. Iwai K, Hasegawa T, Taguchi Y, Morimatsu F, Sato K, Nakamura Y, Higashi A, Kido Y, Nakabo Y, Ohtsuki K. Identification of food-derived collagen peptides in human blood after oral ingestion of gelatin hydrolysates. J Agric Food Chem. 2005;53(16):6531-6536. PMID: 16076145. doi: 10.1021/jf050206p. (The pivotal pharmacokinetic study documenting Pro-Hyp, Ala-Hyp, Ala-Hyp-Gly, Pro-Hyp-Gly, and related collagen-derived peptides in human plasma at 20–60 nmol/mL after gelatin hydrolysate ingestion.)
2. Sontakke SB, Jung JH, Piao Z, Chung HJ. Orally Available Collagen Tripeptide: Enzymatic Stability, Intestinal Permeability, and Absorption of Gly-Pro-Hyp and Pro-Hyp. J Agric Food Chem. 2016;64(38):7127-7133. PMID: 27573716. (Differential bioavailability of GPH vs Pro-Hyp; biotransformation of GPH to Pro-Hyp in rat absorption model.)
3. Shigemura Y, Iwai K, Morimatsu F, Iwamoto T, Mori T, Oda C, Taira T, Park EY, Nakamura Y, Sato K. Effect of Prolyl-hydroxyproline (Pro-Hyp), a food-derived collagen peptide in human blood, on growth of fibroblasts from mouse skin. J Agric Food Chem. 2009;57(2):444-449. doi: 10.1021/jf802785h. (Mouse skin fibroblast proliferation in response to Pro-Hyp — the cleanest single-paper basis for the matrikine fibroblast-stimulation claim for the collagen-tripeptide axis.)
4. Asai TT, Yoshikawa K, Sawada K, Fukamizu K, Koyama YI, Shigemura Y, Jimi S, Sato K. Mouse skin fibroblasts with mesenchymal stem cell marker p75 neurotrophin receptor proliferate in response to prolyl-hydroxyproline. J Funct Foods. 2020;66:103792. DOI: 10.1016/j.jff.2020.103792. (p75NTR-positive fibroblast subset specificity for Pro-Hyp matrikine signal.)
5. Asai TT, Oikawa F, Yoshikawa K, Inoue N, Sato K. Food-Derived Collagen Peptides, Prolyl-Hydroxyproline (Pro-Hyp), and Hydroxyprolyl-Glycine (Hyp-Gly) Enhance Growth of Primary Cultured Mouse Skin Fibroblast Using Fetal Bovine Serum Free from Hydroxyprolyl Peptide. Int J Mol Sci. 2019;21(1):229. PMID: 31905705. (Fibroblast assay replication with hydroxyprolyl-peptide-depleted FBS — important methodological control for the broader Pro-Hyp / GPH fibroblast literature.)
6. Ramshaw JA, Shah NK, Brodsky B. Gly-X-Y tripeptide frequencies in collagen: a context for host-guest triple-helical peptides. J Struct Biol. 1998;122(1-2):86-91. PMID: 9724608. (The canonical Gly-X-Y triplet frequency analysis establishing Gly-Pro-Hyp as the dominant collagen triplet — foundational structural-biology reference for Tripeptide-29 marketing.)
7. Smethurst PA, Onley DJ, Jarvis GE, O'Connor MN, Knight CG, Herr AB, Ouwehand WH, Farndale RW. Structural basis for the platelet-collagen interaction: the smallest motif within collagen that recognizes and activates platelet Glycoprotein VI contains two glycine-proline-hydroxyproline triplets. J Biol Chem. 2007;282(2):1296-1304. PMID: 17085439. (Platelet GPVI / collagen Gly-Pro-Hyp recognition — documents that mammalian cell-surface receptors recognize the GPH triplet at high specificity.)
8. Morton LF, Hargreaves PG, Farndale RW, Young RD, Barnes MJ. Integrin alpha 2 beta 1-independent activation of platelets by simple collagen-like peptides: collagen tertiary (triple-helical) and quaternary (polymeric) structures are sufficient alone for alpha 2 beta 1-independent platelet reactivity. Biochem J. 1995;306(Pt 2):337-344. PMID: 7534064. (Earlier foundational work on GPH / platelet GpVI specificity; the 1999 Knight et al paper PMID 10341844 in Cardiovasc Res extended this analysis to confirm GPH as the specific activating motif.)
9. Proksch E, Segger D, Degwert J, Schunck M, Zague V, Oesser S. Oral supplementation of specific collagen peptides has beneficial effects on human skin physiology: a double-blind, placebo-controlled study. Skin Pharmacol Physiol. 2014;27(1):47-55. PMID: 23949208. doi: 10.1159/000351376. (Pivotal oral collagen peptide RCT — 69 women, 8 weeks, significant skin elasticity improvement. Not Tripeptide-29 specific; representative of the broader collagen-peptide-hydrolysate evidence base.)
10. Asserin J, Lati E, Shioya T, Prawitt J. The effect of oral collagen peptide supplementation on skin moisture and the dermal collagen network: evidence from an ex vivo model and randomized, placebo-controlled clinical trials. J Cosmet Dermatol. 2015;14(4):291-301. PMID: 26362110. doi: 10.1111/jocd.12174. (Two RCTs of oral collagen peptide supplementation showing skin hydration, dermal collagen density, and reduced collagen fragmentation. Oral, not topical Tripeptide-29.)
11. Schunck M, Zague V, Oesser S, Proksch E. Dietary Supplementation with Specific Collagen Peptides Has a Body Mass Index-Dependent Beneficial Effect on Cellulite Morphology. J Med Food. 2015;18(12):1340-1348. PMID: 26561784. (Oral bioactive collagen peptides for cellulite morphology, 105 women, 6-month RCT. Representative of the broader oral collagen peptide RCT body of work.)
12. Bolke L, Schlippe G, Gerß J, Voss W. A Collagen Supplement Improves Skin Hydration, Elasticity, Roughness, and Density: Results of a Randomized, Placebo-Controlled, Blind Study. Nutrients. 2019;11(10):2494. PMID: 31627309. doi: 10.3390/nu11102494. (Multi-ingredient nutricosmetic RCT including collagen peptides; multi-component blend prevents attribution to GPH specifically.)
13. Choi FD, Sung CT, Juhasz ML, Mesinkovsk NA. Oral Collagen Supplementation: A Systematic Review of Dermatological Applications. J Drugs Dermatol. 2019;18(1):9-16. PMID: 30681787. (Systematic review of 11 RCTs of oral collagen supplementation, 805 patients; includes 2 collagen tripeptide trials. No included trial tested topical Tripeptide-29.)
14. Kim DU, Chung HC, Choi J, Sakai Y, Lee BY. Oral Intake of Low-Molecular-Weight Collagen Peptide Improves Hydration, Elasticity, and Wrinkling in Human Skin: A Randomized, Double-Blind, Placebo-Controlled Study. Nutrients. 2018;10(7):826. doi: 10.3390/nu10070826. (Oral LMWCP preparation containing >15% Gly-X-Y tripeptide content including 3% Gly-Pro-Hyp — closest the broader literature gets to a "GPH-enriched" oral RCT, still oral and still multi-component.)
15. Kim J, Lee SG, Lee J, Choi S, Suk J, Lee JH, Yang JH, Yang JS, Kim J. Oral Supplementation of Low-Molecular-Weight Collagen Peptides Reduces Skin Wrinkles and Improves Biophysical Properties of Skin: A Randomized, Double-Blinded, Placebo-Controlled Study. J Med Food. 2022;25(12):1146-1154. PMID: 36516059. (Photoaging RCT of LMWCP oral supplementation.)
16. Lintner K, Peschard O. Biologically active peptides: from a laboratory bench curiosity to a functional skin care product. Int J Cosmet Sci. 2000;22(3):207-218. PMID: 18503476. (Foundational matrikine-cosmetic-peptide review establishing the "small synthetic peptide as topical fibroblast signal" framework — palmitoyl-pentapeptide-4 / Matrixyl included.)
17. Aldag C, Nogueira Teixeira D, Leventhal PS. Skin rejuvenation using cosmetic products containing growth factors, cytokines, and matrikines: a review of the literature. Clin Cosmet Investig Dermatol. 2016;9:411-419. PMID: 27877059. (Review of matrikine-class cosmetic peptide ingredients and their evidence base.)
18. Yamamoto S, Hayasaka F, Deguchi K, Okudera T, Furusawa T, Sakai Y. Absorption and plasma kinetics of collagen tripeptide after peroral or intraperitoneal administration in rats. Biosci Biotechnol Biochem. 2015;79(12):2026-2033. PMID: 26155906. (Pharmacokinetic study of Gly-Pro-Hyp absorption after peroral and intraperitoneal administration; documents systemic exposure to GPH.)
19. Taga Y, Iwasaki Y, Tometsuka C, Funato N, Shigemura Y, Kusubata M, Mizuno K. Identification of a Highly Stable Bioactive 3-Hydroxyproline-Containing Tripeptide in Human Blood after Collagen Hydrolysate Ingestion. npj Sci Food. 2022;6(1):29. PMID: 35662250. (Identification of Gly-3Hyp-4Hyp as a stable bioactive collagen tripeptide in human blood; chemoattractant for skin fibroblasts. Adjacent biology relevant to the broader collagen-tripeptide skin-effect mechanistic story.)
20. Hatanaka T, Kawakami K, Uraji M. Inhibitory effect of collagen-derived tripeptides on dipeptidylpeptidase-IV activity. J Enzyme Inhib Med Chem. 2014;29(6):823-828. PMID: 24650211. (Documents enzymatic activity of Gly-Pro-Hyp, Gly-Ala-Hyp, and Gly-Pro-Ala collagen tripeptides on DPP-IV — shows GPH has measurable cell-relevant enzymatic activity beyond the matrikine-signaling claim.)
21. Ohara H, Ichikawa S, Matsumoto H, Akiyama M, Fujimoto N, Kobayashi T, Tajima S. Collagen-derived dipeptide, proline-hydroxyproline, stimulates cell proliferation and hyaluronic acid synthesis in cultured human dermal fibroblasts. J Dermatol. 2010;37(4):330-338. PMID: 20507402. (Pro-Hyp dipeptide enhances proliferation and HA synthesis in human dermal fibroblasts at 200 nmol/mL — the strongest single piece of in vitro evidence for the matrikine-class signal in human skin cells.)
22. Hexsel D, Zague V, Schunck M, Siega C, Camargo FB Jr, Oesser S. Oral supplementation of specific bioactive collagen peptides reduces skin wrinkles and improves nail growth in women. J Cosmet Dermatol. 2017;16(4):520-526. PMID: 28786550. (Oral bioactive collagen peptides RCT in nail-brittleness — adjacent collagen-peptide cosmetic indication, representative of the wider field.)
23. Genovese L, Corbo A, Sibilla S. An Insight into the Changes in Skin Texture and Properties following Dietary Intervention with a Nutricosmeceutical Containing a Blend of Collagen Bioactive Peptides and Antioxidants. Skin Pharmacol Physiol. 2017;30(3):146-158. PMID: 28528342. (Nutricosmetic blend including collagen bioactive peptides; multi-ingredient formulation; representative of the broader nutricosmeceutical RCT literature.)
24. De Luca C, Mikhal'chik EV, Suprun MV, Papacharalambous M, Truhanov AI, Korkina LG. Skin Antiageing and Systemic Redox Effects of Supplementation with Marine Collagen Peptides and Plant-Derived Antioxidants: A Single-Blind Case-Control Clinical Study. Oxid Med Cell Longev. 2016;2016:4389410. PMID: 26904164. (Marine collagen peptide oral supplementation skin study; representative of marine-collagen-peptide subset of the broader literature.)
25. FDA. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the FD&C Act (503A categories list), versions updated April 15, April 22 and May 14, 2026. fda.gov/media/94155/download. Read October 3, 2026. (Notice that 12 peptides would leave Category 2 because their nominations were withdrawn; their removal; GHK-Cu, except injectable, back in Category 1.)

Related Research

• MatrixylCollagen Signal Peptide
• Syn-CollTGF-β Mimetic / Collagen Signal
• AOD-9604hGH C-Terminal Fragment / Lipolytic
• HGH Fragment 176-191Growth Hormone C-Terminal Fragment
• FDA TrackerPCAC voted on 7 of the 12 peptides on July 23–24, 2026; FDA plans a PCAC review of the other 5 before the end of February 2027.