GHK-Cu is a copper-binding tripeptide found in human plasma. A research guide to its copper chemistry, the fibroblast, wound and gene-expression studies behind its reputation, the limits of that evidence, and how to handle a copper complex in the lab.
GHK (glycyl-L-histidyl-L-lysine) is a tripeptide present in human plasma, saliva and urine [6]. It was first described in 1973 by Loren Pickart and Martin Thaler as a factor in human serum that prolonged the survival of normal liver cells and stimulated the growth of hepatoma cells in culture [5]. GHK binds copper(II) tightly, and most research uses the copper complex, GHK-Cu. Since then it has been studied in fibroblast culture, animal wound models and, more recently, gene-expression datasets. This guide explains what those studies measured and where the evidence is strongest and weakest.
GHK's affinity for Cu(II) is similar to that of the copper-transport site on albumin [2], so the two can compete for copper in serum. X-ray and spectroscopic work by Hureau and colleagues clarified how the metal is held [9]. In solution, GHK-Cu is a monomer in which copper is bound by three nitrogen atoms: the free amine of glycine, the deprotonated amide nitrogen of the Gly-His peptide bond, and the imidazole nitrogen of histidine. The fourth equatorial position is occupied by a labile oxygen ligand. In the solid state, a carboxylate oxygen fills that position and the complex crystallizes as a dimer.
The same study found two properties that matter in the lab [9]. First, copper exchanges quickly between GHK molecules, which the authors attributed to a transient complex holding two GHK molecules per copper. Second, GHK-Cu is redox-inert under moderate conditions but can be reduced to Cu(I) at around -0.62 V (versus Ag/AgCl), at which point the copper is released. In other words, GHK-Cu is a stable complex but not a locked one. It can give up its copper to competing ligands or under reducing conditions.
Where does GHK come from? Maquart and colleagues pointed out that the sequence Gly-His-Lys occurs within the α2(I) chain of type I collagen, and suggested that proteases could release it at a wound site [4]. The idea neatly ties the peptide to the matrix it is studied for, but it remains a hypothesis.
Pickart's reviews report that plasma GHK is about 200 ng/mL at age 20 and declines to about 80 ng/mL by age 60 [1][6]. This decline is often quoted alongside the observation that the original 1973 experiment used plasma from young donors to improve the behavior of liver tissue from older donors [1]. The association is interesting, but a falling plasma level does not by itself show that GHK causes age-related changes in tissue repair.
The foundational cell study is Maquart et al. (1988) [4]. In fibroblast cultures, GHK-Cu stimulated collagen synthesis beginning between 10⁻¹² and 10⁻¹¹ M and reaching a maximum at 10⁻⁹ M, and the effect was independent of any change in cell number. That last point is important: the cells made more collagen each, rather than there simply being more cells. Later work summarized by Pickart describes GHK as stimulating both the synthesis and the breakdown of collagen and glycosaminoglycans, increasing dermatan sulfate, chondroitin sulfate and the proteoglycan decorin, and modulating both metalloproteinases and their inhibitors [6]. That balance of build-up and breakdown is why it is described as a remodeling molecule rather than simply a pro-fibrotic one.
One of the clearest controlled animal studies used 24 rats with full-thickness wounds created inside an ischemic skin flap, a model of poorly perfused tissue [3]. Wounds received a topical tripeptide-copper gel, the gel vehicle alone, or no application. By day 13, wound area had decreased by 64.5% with the GHK-Cu gel, 45.6% with vehicle and 28.2% in untouched controls, and GHK-Cu wounds contained significantly lower concentrations of TNF-α and of the matrix metalloproteinases MMP-2 and MMP-9. Including a vehicle arm is the detail to copy: the gel alone had an effect, and the peptide's contribution is the difference between the two. Reviews from Pickart's group also describe wound-healing effects in rat, mouse, pig and dog models and in hair follicle, bone and gastrointestinal tissue [6].
The most rigorous gene-expression work comes from an independent study of chronic obstructive pulmonary disease (COPD). Campbell and colleagues profiled lung tissue regions with different degrees of emphysema from smokers with COPD and identified 127 genes whose expression tracked with tissue destruction [7]. Genes involved in tissue repair, including the TGF-β pathway, actin organization and integrin signaling, fell as damage increased. Querying the Broad Institute's Connectivity Map, a reference library of gene-expression profiles from cultured human cells exposed to small molecules [8], they identified GHK as a compound whose profile reversed that signature. They then tested it directly: in human fibroblasts GHK reproduced TGF-β-like expression patterns, organized the actin cytoskeleton and raised integrin β1, and GHK restored the ability of fibroblasts from COPD lungs to contract and remodel collagen I gels [7].
Pickart's group has mined Connectivity Map data more broadly and reported that GHK shifts the expression of at least 4,000 human genes [6]; their 2018 review describes 31.2% of genes as changing by 50% or more [1]. These analyses are the source of the frequently repeated '4,000 genes' figure. They are useful for generating hypotheses. But they come from transcriptional profiles of cultured cell lines at the concentrations used in the Connectivity Map [8], and most were interpreted by the group that discovered the peptide. The COPD fibroblast work above shows what testing such a prediction experimentally looks like.
Most human data on GHK-Cu come from topical cosmetic formulations. Pickart's reviews summarize controlled studies in volunteers that reported changes in skin firmness, elasticity, fine lines and pigmentation [1][2]. Separately, Hostynek and colleagues measured penetration in vitro using human skin in flow-through diffusion cells, analyzing copper by inductively coupled plasma mass spectrometry. Copper applied as GHK-Cu permeated dermatomed skin over 48 hours, and a further portion was retained in the tissue [10]. These are findings about particular formulations and test systems, not about research-grade material.
Common approaches include collagen synthesis measurements in dermal fibroblast cultures, normalized to cell number [4]; collagen gel contraction and actin staining in fibroblasts [7]; transcriptomic profiling followed by pathway analysis and targeted confirmation [7][8]; ischemic or excisional wound models with vehicle controls and tissue cytokine and MMP measurements [3]; skin permeation in diffusion cells with ICP-MS copper analysis [10]; and, for the complex itself, EPR, X-ray absorption and cyclic voltammetry [9]. A well-controlled cell experiment usually includes four arms: GHK-Cu, GHK without copper, a copper salt at the matching copper concentration, and vehicle.
GHK-Cu is supplied as a blue powder; the color comes from the copper(II) complex. Store it at -20°C, sealed and dry, and let the vial reach room temperature before opening. Dissolve it in water or a simple buffer, and keep reducing agents and strong metal chelators such as EDTA out of stock solutions. Reduction can release the copper [9], and a strong chelator will compete with the peptide for it. When calculating molar concentrations, use the molecular weight of the complex (403.92 Da on the product page), not that of free GHK, and account for net peptide content if the certificate reports it.
Confirm identity by mass spectrometry and purity by HPLC. Northbridge Research Labs sends every batch for independent third-party testing, and published certificates are listed on our COA page.
Note: GHK-Cu is sold strictly for laboratory research use only. It is not for human or veterinary use.
Studied compound
GHK-Cu (Copper Peptide)
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