The best peptides for skin research

This guide reflects our reading of the literature on dermatological research that was published in 2026. We compare these compounds by the specificity of their mechanism and by their line of study, and we point out where the claims go further than the evidence.

This is a ranked guide to the best research-grade peptides for skin that are intended for laboratory work in 2026, and not a review of cosmetic serums or of skincare for consumers. The three compounds that make it onto the shortlist are GHK-Cu (copper tripeptide-1, a signal for collagen and elastin), melanotan II (an analogue of α-MSH, for models of melanogenesis) and the BPC-157 + TB-500 stack (angiogenesis and the migration of fibroblasts in work on the repair of wounds). Each one of them represents a mechanism of its own, a line of study of its own and a route of supply of its own for research.

This guide ranks them by their application in research, and not by the claims of marketing. You will see which peptide fits your endpoint of interest, how each one of them acts at the molecular level and which dose ranges appear in the published literature for your model system.

GHK-Cu, the synthesis of collagen and elastin in fibroblasts; topical and subcutaneous models.

Melanotan II, melanogenesis mediated by MC1R and MC4R; it is worth checking its legal status against the requirements currently in force before any purchasing decision is made.

BPC-157 + TB-500, protocols for wound healing that combine angiogenesis and the sequestration of actin.

Pre-filled pen format, with the dose dialled directly in milligrams on the dose dial, which keeps every administration identical in research that involves repeated dosing.

Cosmetic peptide serums belong to a category of their own and are mentioned only in order to set the context [2].

Peptides for skin research: the essentials

• GHK-Cu is the standard for studies of the synthesis of collagen and elastin in dermal fibroblasts, with published working concentrations of 1-10 µM in vitro.
• Melanotan II 20 mg drives melanogenesis through the agonism of MC1R and MC4R and is supplied as a multi-dose pen for reproducible subcutaneous dosing in research models.
• BPC-157 + TB-500 target complementary phases of wound healing: early angiogenesis and the adhesion of fibroblasts (BPC-157) plus the migration and remodelling that are driven by actin (TB-500).
• Pre-filled multi-dose pens dial the dose in milligrams and provide traceability of the batch, something that matters for the reproducibility of protocols.
• All three peptides are supplied exclusively for laboratory and analytical purposes; it is worth checking their regulatory status before you buy.

What are peptides for skin research?

Peptides for skin research are short chains of amino acids (normally of 3 to 10 residues) that are studied in vitro and in animal models for the way they interact with dermal fibroblasts, melanocytes, keratinocytes and the proteins of the extracellular matrix such as collagen, elastin and decorin. They are supplied exclusively for laboratory and analytical purposes, and not for human use. All of the Body Pharm products fall within that classification of research use only.

Three functional classes dominate the literature on skin [2].

Signalling peptides tell the fibroblasts to upregulate the proteins of the matrix. GHK-Cu is a tripeptide (Gly-His-Lys) that was first isolated from human plasma by Pickart in 1973 and complexed with copper(II) in order to obtain an active redox signal [1].

Carrier peptides deliver trace elements (almost always copper) to active enzymatic centres. GHK-Cu fulfils that role as well.

Melanocortin agonists bind to MC1R and MC4R in order to drive the synthesis of eumelanin. Melanotan II is a cyclic heptapeptide analogue of α-MSH, synthesised for the first time in the early 1990s at the University of Arizona by Hadley and colleagues [3].

Regenerative peptides, BPC-157 (a fragment of 15 amino acids from the gastric Body Protection Compound) and TB-500 (a synthetic fragment of thymosin β4), are studied in models of wound repair for their effect on angiogenesis and the migration of fibroblasts, because they address different phases of the healing of tissue.

The depth of protocol for the signalling and melanocortin compounds is on pages of their own: How to dose GHK-Cu and How to dose melanotan II.

Top picks: the best peptides for skin in research (2026)

This is a ranked selection of research-grade peptides for skin in research on the dermis, on collagen and on pigmentation, headed by the copper peptide that underpins most of the published work on the remodelling of skin. It is not a guide to cosmetic serums or to over-the-counter skincare, which belong to a category of their own and are mentioned only in order to set the context [2]. Each pick is a research peptide from the Body Pharm catalogue, supplied as a multi-dose injectable pen with a validated dose, exclusively for in vitro and laboratory use.

• Best overall / most complete mechanism: GHK-Cu. The copper tripeptide standard (Gly-His-Lys-Cu²⁺) for research on collagen and elastin, which upregulates collagen I, collagen III, elastin and decorin in models of dermal fibroblasts while at the same time modulating the turnover of MMP-1 and MMP-2 (Pickart and Margolina, 2018) [4]. Protocol details: How to dose GHK-Cu.
• Best for research on pigmentation / melanogenesis: Melanotan II 20 mg. A cyclic analogue of α-MSH which, as an agonist of MC1R and MC4R, drives the synthesis of eumelanin in models of melanocytes (Hadley and Dorr, 2006) [3]. Protocol details: How to dose melanotan II.
• Best for research on wound repair / regeneration: BPC-157 + TB-500 combination pen. The pentadecapeptide BPC-157 paired with a fragment of thymosin β4, studied for FAK-paxillin signalling, angiogenesis and the migration of fibroblasts across complementary phases of the repair of soft tissue and of the extracellular matrix (Chang et al., 2011) [5].

GHK-Cu is the point of entry for the majority of programmes that focus on skin, because the endpoints of collagen synthesis are the best documented in the dermal literature. The full details of the mechanism and line of study for each pick are set out further down. All three formats ship to Spain in 2026 with research labelling.

GHK-Cu: the copper peptide for research on collagen

GHK-Cu is the copper-bound tripeptide Gly-His-Lys-Cu²⁺, which is studied for its stimulation of the synthesis of collagen and elastin in dermal fibroblasts at nanomolar concentrations. Its dual identity as a chelator of copper and as a signalling peptide separates it from the cosmetic peptides that carry no metal and lies at the root of most of the published results on dermal remodelling since the late 1980s.

Mechanism of action

The peptide binds Cu²⁺ with an affinity that is close to physiological and transports it across membranes. The copper cofactor activates lysyl oxidase (which cross-links collagen and elastin) and superoxide dismutase. Independently of the transport of copper, GHK acts as a transcriptional signal. Pickart and Margolina (2018) describe an upregulation of the expression of transforming growth factor beta-1 (TGF-β1), of the synthesis of decorin and of the deposition of collagen I and III in cultures of human dermal fibroblasts [4]. The production of collagen that is described increases by up to 70% compared with untreated controls.

GHK-Cu modulates the turnover of the extracellular matrix by suppressing matrix metalloproteinase 1 (MMP-1) and MMP-2 while at the same time raising the tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2). In models of fibroblasts, the net effect is less degradation of the matrix together with greater deposition. That balance is the reason why the peptide is studied for the remodelling of photoaged skin and not only for the acute closure of wounds.

There are researchers who ask themselves whether the effects of GHK-Cu that are observed in fibroblast assays in vitro carry over to topical or subcutaneous administration in living tissue. The answer depends on the choice of vehicle and on the time of exposure, and both of them must be declared in any protocol.

Published research 2009-2024

Gorouhi and Maibach (2009, International Journal of Cosmetic Science) reviewed the controlled ex vivo and in vivo studies on topical peptides in aged skin and classified them into signal peptides, enzyme-inhibitor peptides, neurotransmitter-inhibitor peptides and carrier peptides, with the copper peptide complexes among the signal and carrier peptides [2]. Pickart and Margolina (2018, International Journal of Molecular Sciences) catalogued the effects of GHK-Cu on gene expression across more than 4000 genes in fibroblast assays and documented the upregulation of decorin, of integrins and of antioxidant response elements [4]. The in vivo concentrations from after 2022 and the updated mechanistic work could not be verified in the corpus of sources for this guide and are deliberately omitted rather than approximated.

The Body Pharm GHK-Cu pen: format and traceability

Body Pharm's GHK-Cu is supplied as a pre-filled multi-dose injectable pen, with 50 mg in total in a 3 ml cartridge, and it ships to Spain in 2026 with research labelling. The dose dial shows the dose directly in milligrams. Each unit carries a batch number that is linked to its filling record, so that the dose-response data can be checked against a single batch.

For the dialled doses and the parameters for storage, see How to dose GHK-Cu.

Note on research methodology If you cite evidence on GHK-Cu in a research report, separate (a) the in vitro data from fibroblasts, (b) the ex vivo data from skin explants and (c) the in vivo data from topical or subcutaneous application. The sizes of the effects do not carry over in a linear way between models. A concentration of copper peptide is meaningless if the vehicle (saline solution, liposomal or cream base) and the time of exposure are not declared alongside it.

GHK-Cu dose ranges in research

The published research on GHK-Cu clusters around two distinct dose regimes that should not be mixed up in experimental reports.

In vitro fibroblast assays: Pickart and Margolina (2018, International Journal of Molecular Sciences) and the wider literature on fibroblasts describe working concentrations of 1-10 µM of GHK-Cu in the culture medium [4]. The effects on gene expression are measurable on the panel of more than 4000 genes that was mentioned earlier in this guide.

Ex vivo work with skin explants: topical vehicles usually deliver GHK-Cu at 0.05-0.2% w/v in saline solution or in liposomal carriers. The exact values vary according to the publication and the vehicle, and they should be taken directly from the methods section of the study that is cited in each case.

In vivo animal models: the subcutaneous ranges in mg/kg from the rodent studies of 2023 to 2025 are not verified in the corpus of sources for this guide and are deliberately not approximated here. If you are planning protocols in animals, go to the primary papers on PubMed instead of relying on secondary summaries.

The vehicle and the time of exposure must be reported alongside any data on concentration. The bioavailability of copper peptides changes considerably between saline solution, liposomal carriers and cream bases.

For the doses dialled on the dose dial and the parameters for storage of the Body Pharm pen format, see How to dose GHK-Cu. Everything above serves only to situate the research model. GHK-Cu is supplied exclusively for in vitro and laboratory research, and not for human use.

Melanotan II 20 mg: research on melanogenesis

Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone (α-MSH) that is used in research models to study induced melanogenesis and the pharmacology of the melanocortin receptors. It is a non-selective agonist of MC1R and MC4R. The downstream signal through adenylate cyclase (AC), cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) drives the transcription of tyrosinase and the synthesis of eumelanin in cultured melanocytes.

Key features of the receptor and of the signalling pathway that are commonly cited:

• Agonism of MC1R in epidermal melanocytes upregulates microphthalmia-associated transcription factor (MITF) and tyrosinase, and shifts the production of pigment towards eumelanin.
• Agonism of MC4R in the hypothalamus is the mechanism that lies behind the non-pigmentary effects (appetite, libido) described in the early work on human pharmacology. It is a confounder in any whole-organism model.
• The cAMP and PKA signal is the canonical cascade of second messengers that links the binding to the receptor with melanogenic gene expression.
• The cyclic lactam backbone confers resistance to proteases compared with linear α-MSH and extends the plasma half-life in pharmacokinetic models.
• The photoprotection endpoints in the published research usually measure the shift in the minimal erythema dose (MED) and the density of constitutive pigment, rather than direct biomarkers of damage from UV.

The context of the published research

The 2006 review by Hadley and Dorr in Peptides remains the most cited pharmacological summary; it reviews the historical milestones, the early clinical studies and the commercialisation of the melanocortin analogues, melanotan I and melanotan II included, and remains the starting reference on their pharmacology [3]. The more recent reviews on melanocortin agonists in research on pigmentation (from 2023 onwards) should be consulted directly on PubMed. The specific dose ranges in subcutaneous models of melanogenesis from 2023 to 2026 are not verified in the corpus of sources used for this guide and should be taken from the primary methods sections before any protocol is designed.

Supply and format

The Body Pharm Melanotan II pen (20 mg) is a pre-filled multi-dose pen for the subcutaneous route, with a 3 ml cartridge and shipping to Spain in 2026. It arrives ready to use and the dose dial shows the dose directly in milligrams, so the same figure means the same thing in every replicated experiment. The research protocol is a loading phase of 200 mcg a day, rising to 500 mcg a day, and a maintenance of 200 mcg twice a week. Discreet shipping within Spain keeps the transit times short, something that is relevant to the stability of the peptide in any longitudinal research design.

For the dialled doses and the parameters for storage that are specific to this format, see How to dose melanotan II. The handling of the device matches what is described in How to dose GHK-Cu, so anyone who uses both peptides in parallel can standardise their procedures.

Regulatory status and use

The regulatory status of research peptides, melanotan II included, for 2025-2026 is not verified against the requirements currently in force from the authorities in the corpus of sources for this guide. Check it directly with the competent authority before any purchasing decision. Melanotan II 20 mg is supplied exclusively for in vitro and laboratory research and is not intended for human use.

Melanotan II versus natural alpha-MSH: the key differences

Melanotan II is used in research in preference to endogenous alpha-MSH because its cyclic lactam structure and the substitution of a D-amino acid at position 7 give it resistance to proteolysis and a considerably longer plasma half-life. That is what makes the dose-response curves reproducible between replicated experiments.

Plasma half-life: the cyclic, protease-resistant structure gives melanotan II a considerably longer plasma half-life than linear alpha-MSH; in the pilot phase I study by Dorr et al. (1996, Life Sciences), five low subcutaneous doses on alternate days were enough to produce measurable pigmentation in healthy volunteers [6]. That reference dates from before 2023, but it remains the standard human citation in the literature on melanocortins in 2026.

Affinity for the receptor: melanotan II is a non-selective agonist of MC1R, MC3R, MC4R and MC5R, whereas endogenous alpha-MSH shows preferential binding to MC1R in cutaneous melanocytes.

Usefulness in research: the extended half-life allows less frequent administration in subcutaneous models of melanogenesis and reduces the variance that comes from handling. The doses dialled on the dose dial are described in How to dose melanotan II.

BPC-157 + TB-500: research on the repair of skin and soft tissue

BPC-157 and TB-500 are combined in research on the repair of soft tissue because they address phases of healing that are distinct and complementary. BPC-157 drives early angiogenesis and the adhesion of fibroblasts by way of the signal from focal adhesion kinase (FAK) and paxillin. TB-500 (a fragment of thymosin beta-4) accelerates the polymerisation of actin, the migration of keratinocytes and the remodelling of the extracellular matrix in the phases of proliferation and remodelling.

BPC-157: mechanism and rationale in cutaneous repair

BPC-157 (Body Protection Compound-157) is a synthetic pentadecapeptide of 15 amino acids derived from a protective sequence that was identified in human gastric juice. In rat tendon fibroblasts, Chang et al. (2011, Journal of Applied Physiology) described that BPC-157 accelerates the outgrowth of fibroblasts from tendon explants, increases their survival under oxidative stress and stimulates their migration in a dose-dependent manner, with increased phosphorylation of FAK and paxillin, the pathway that controls the adhesion of fibroblasts to the provisional matrix [5]. That same pathway takes part in the activation of vascular endothelial growth factor receptor 2 (VEGFR2) and provides a plausible mechanism for the angiogenic effects that are observed in models of tendon and of skin flaps. Whether specifically dermal replications from 2024 to 2026 exist is something worth checking directly on PubMed before citing them in a report.

TB-500: mechanism and rationale in cutaneous repair

TB-500 is the active fragment of 17 amino acids of thymosin beta-4 (Tβ4), the main G-actin-sequestering peptide in the cells of mammals. The review by Goldstein and Kleinman (2015, Expert Opinion on Biological Therapy) summarised the role of Tβ4 in promoting the migration of keratinocytes and endothelial cells, in reducing inflammatory infiltrates and in lowering the density of scar tissue in full-thickness wounds in rodent and porcine models [7]. The mechanism is twofold: the release of actin monomers as the cell membrane depolarises drives the extension of lamellipodia, while the parallel upregulation of laminin-5 supports the rebuilding of the basement membrane.

Why BPC-157 and TB-500 are combined

The combination is justified by the logic of covering the phases. BPC-157 dominates the early vascular and fibroblast signal; TB-500 directs the migration and remodelling driven by actin in the middle and late phases. Neither of the two peptides reproduces the mechanism of the other in the published rodent models of cutaneous repair. Those who study full-thickness wounds are combining them more and more, instead of scaling up a single active principle.

Coverage of the early phase (BPC-157): angiogenesis by way of VEGFR2 and the endothelial FAK-paxillin signal, plus the recruitment of fibroblasts in the window between the inflammatory and proliferative phases.

Coverage of the middle to late phase (TB-500): the sequestration of actin monomers frees G-actin for the extension of lamellipodia and favours the migration of keratinocytes and fibroblasts across the bed of the wound during proliferation and remodelling.

Targets that do not overlap: vascular and signalling (BPC-157) as against cytoskeletal and migratory (TB-500), which reduces redundancy in a combined protocol.

Antifibrotic endpoint: the documented downregulation of TGF-β1 by TB-500 in animal models is the specific reason for adding it when the quality of the scar is being measured and not only the rate of closure.

For a comparison of mechanism and protocol, see the Body Pharm BPC-157 vs TB-500 comparison.

Comparison table of the peptides' mechanisms (2026)

The three peptide systems that are purchased most often for skin research occupy distinct molecular niches. GHK-Cu drives the remodelling of the matrix, melanotan II drives melanogenesis and BPC-157 + TB-500 drive the repair of wounds. The table below summarises the receptor target, the signalling pathway, the application, the published dose ranges and the Body Pharm dosing-pen format, for a direct comparison before you select the protocol.

Complementary protocol resources

• How to dose GHK-Cu, the doses dialled on the dose dial and the equivalent working concentrations in µM for research with fibroblasts and topical research.
• How to dose melanotan II, a subcutaneous titration scheme in line with the range of Hadley and Dorr.

Footnote: all of the dose ranges cited above come from the published research literature in their original experimental models (µM in vitro, mg/kg in rodents or subcutaneous mg in research models). Body Pharm products are supplied exclusively for research and analytical purposes and are not intended for human or animal use.

How Body Pharm supplies peptides for skin research

Body Pharm supplies peptides for skin research in the format of a sealed multi-dose injectable pen with a validated dose, with full traceability of the batch. The products are shipped discreetly within Spain exclusively for research and analytical purposes. These products are not authorised medicines and they are not intended for human or animal use.

The pen format matters for the integrity of the research. Each pen is sealed at the factory with a verified total mass (for example, the 20 mg of the Melanotan II pen in the comparison table above) and it arrives ready to use. The steps of the dose dial are mechanically validated and are read in milligrams, which makes serial sampling and replication across a study cohort considerably more consistent.

Storage for the whole range: between 2 and 8 °C protected from light; 24 months unopened and 12 months from the first puncture; up to 30 days at room temperature (maximum 30 °C) if you have no fridge available. Let the pen reach room temperature before you inject and do not freeze it.

What traceability of the batch means in practice

Each pen is delivered with a unique batch number that is linked to its documentation of purity. For those doing research, that means:

• A specific batch number on the device and on the outer packaging, associated with its corresponding analytical record.
• Data on purity (HPLC and, where applicable, mass spectrometry) that are tied to that batch and not to a generic product specification.
• The possibility of referencing the same batch across replicated experiments, which is the minimum standard of reproducibility in any peptide-based protocol in vitro or in rodents.

Shipping and regulatory position

Orders are shipped in neutral, tamper-evident packaging, with standard tracked shipping within Spain (3-5 working days). Research peptides that are sold exclusively for laboratory and analytical purposes fall outside the framework of the authorisation of medicines. It is worth checking the current position of the authorities before you buy, since the classification of particular compounds can change independently of the labelling of the product.

For the two compounds that are ordered most often for skin research, the protocol pages on this site provide the working details that complement the format of supply. How to dose GHK-Cu deals with the doses dialled on the dose dial and the working concentrations in µM for assays with fibroblasts. How to dose melanotan II describes the subcutaneous titration scheme that is used in research models of melanogenesis.

How to choose the right skin peptide for your research

The right peptide is the one that fits the signalling pathway that you are measuring. Three decision points cover the majority of research programmes that focus on skin in 2026.

Synthesis of collagen or remodelling of the extracellular matrix → GHK-Cu. Use it when the measure is procollagen I and III, the expression of MMPs or the proliferation of fibroblasts in monolayer or in 3D skin equivalents. The dialled doses and the working concentrations in µM for those assays are described in How to dose GHK-Cu.

Pathways of melanogenesis or pigmentation → Melanotan II 20 mg. Appropriate when the endpoint is the activity of tyrosinase, the ratio between eumelanin and pheomelanin or the signal mediated by MC1R in cultures of melanocytes or in rodent models. Subcutaneous titration for the latter is covered in How to dose melanotan II.

Wound healing, repair of soft tissue or multiphase remodelling of the matrix → BPC-157 + TB-500 combination pen. Choose it when the model includes incisional or excisional wounds, the formation of granulation tissue or angiogenic and actin-cytoskeleton endpoints in the same arm.

Designs with parallel arms. Programmes that compare the production of collagen with the kinetics of repair usually run GHK-Cu and the BPC-157 + TB-500 combination as separate arms with a common vehicle control, rather than administering them together.

Each compound has a dosing page of its own in the guides section of Body Pharm, with the doses dialled on the dose dial, the conditions of storage and the working concentrations cited in the source literature for each model.

Frequently Asked Questions

What is GHK-Cu used for in skin research? GHK-Cu is a copper-binding tripeptide that is studied for its effect on the activity of dermal fibroblasts, the synthesis of procollagen I and III and the modulation of matrix metalloproteinases. The applications in research include 2D fibroblast monolayers, 3D skin equivalents and ex vivo skin explants that measure the turnover of the extracellular matrix. The working protocols are described in How to dose GHK-Cu.

Is melanotan II legal in Spain? Melanotan II is not an authorised medicine for human use and it is sold exclusively as a research chemical. It is worth checking its exact regulatory status against the requirements currently in force from the authorities before you buy. Subcutaneous titration in models of melanogenesis is described in How to dose melanotan II.

What is the difference between BPC-157 and TB-500 for cutaneous repair? BPC-157 is a gastric pentadecapeptide of 15 amino acids that is studied for its angiogenic and granulation-tissue endpoints, whereas TB-500 is a synthetic fragment of thymosin β4 that is studied for the remodelling of the actin cytoskeleton and the migration of keratinocytes. The combination is used when both pathways are measured in the same wound-healing arm.

Can research peptides be used in studies of collagen synthesis? Yes. GHK-Cu is the standard reference compound for measurements of procollagen I and III in fibroblast culture, normally at working concentrations in µM in serum-free or low-serum medium. The endpoints include ELISA, qPCR for COL1A1 and COL3A1 and hydroxyproline assays in 3D skin constructs.

Where can I buy peptides for skin research in Spain? Body Pharm supplies GHK-Cu, Melanotan II 20 mg and the BPC-157 + TB-500 combination pen in a dosing-pen format for laboratory research, with shipping to Spain and documentation of the batch. The products are sold exclusively for research purposes and are not intended for human consumption.

Next steps

Start by identifying the research endpoint that fits your protocol: synthesis of collagen (GHK-Cu), melanogenesis (melanotan II) or wound healing (BPC-157 + TB-500). Once you have chosen the peptide, visit the corresponding dosing guide, How to dose GHK-Cu or How to dose melanotan II, to take the working concentrations and the dialled doses for your model system. Check the current regulatory position of the compound you have chosen before you place an order with Body Pharm.

Sources

1. Pickart L, et al. GHK Peptide as a Natural Modulator of Multiple Cellular Pathways in Skin Regeneration. Biomed Res Int. 2015. pubmed.ncbi.nlm.nih.gov/26236730
2. Gorouhi F, Maibach HI. Role of topical peptides in preventing or treating aged skin. Int J Cosmet Sci. 2009. pubmed.ncbi.nlm.nih.gov/19570099
3. Hadley ME, Dorr RT. Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization. Peptides. 2006. pubmed.ncbi.nlm.nih.gov/16412534
4. Pickart L, Margolina A. Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data. Int J Mol Sci. 2018. pubmed.ncbi.nlm.nih.gov/29986520
5. Chang CH, et al. The promoting effect of pentadecapeptide BPC 157 on tendon healing involves tendon outgrowth, cell survival, and cell migration. J Appl Physiol (1985). 2011. pubmed.ncbi.nlm.nih.gov/21030672
6. Dorr RT, et al. Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study. Life Sci. 1996. pubmed.ncbi.nlm.nih.gov/8637402
7. Goldstein AL, Kleinman HK. Advances in the basic and clinical applications of thymosin β4. Expert Opin Biol Ther. 2015. pubmed.ncbi.nlm.nih.gov/26096726