PEG-MGF 2mg – Research Grade PEGylated Mechano Growth Factor

PEG-MGF is a PEGylated synthetic peptide corresponding to the unique C-terminal sequence of mechano growth factor (MGF), a splice variant of insulin-like growth factor 1 (IGF-1). The IGF1 gene produces several alternatively spliced mRNA isoforms with distinct E-peptide C-terminal extensions; MGF (also called IGF-1Ec in human nomenclature, or IGF-1Eb in the original rodent nomenclature where the homologous variant was first characterized) is the splice variant that includes exon 5, producing a precursor pro-IGF-1 with a unique C-terminal Ec-peptide extension. MGF expression in skeletal muscle is upregulated in response to mechanical loading and damage, and the Ec/MGF C-terminal peptide has been characterized in skeletal-muscle research as having biological activity distinct from mature IGF-1 itself.

The research-supply PEG-MGF peptide is a synthetic 24-amino-acid (approximately) peptide corresponding to the Ec/MGF C-terminal sequence, conjugated to polyethylene glycol (PEG) at a defined residue (typically the N-terminus) to provide a substantial increase in plasma half-life through reduced renal clearance and reduced proteolytic degradation. The native Ec/MGF C-terminal peptide is rapidly cleared and degraded in vivo (plasma half-life on the order of minutes); PEGylation extends the in-vivo half-life to a substantially longer window, supporting practical research-pharmacology dosing schedules in preclinical work.

The published research on MGF and on Ec/MGF C-terminal peptides has been led primarily by Geoffrey Goldspink and colleagues at University College London and by collaborating groups, with characterization of the MGF splice-variant biology, the muscle-stem-cell (satellite cell) activation effects of the C-terminal peptide, and the regenerative-muscle research applications in preclinical models. PEG-MGF is the PEGylated research-format of this C-terminal peptide.

This page is a research-only educational reference for PEG-MGF as a research peptide for skeletal-muscle and satellite-cell preclinical research. The peptide is not approved as a medicine and is not the subject of any clinical-research program. No medical or therapeutic claims are made on this page.

PEG-MGF consists of a synthetic peptide corresponding to the C-terminal Ec/MGF region of pro-IGF-1Ec, conjugated to polyethylene glycol (PEG) for extended plasma half-life. The Ec/MGF peptide sequence is the 24-residue extension produced by exon-5 inclusion in the IGF-1Ec splice variant. The PEG conjugate is typically a methoxy-polyethylene-glycol (mPEG) of defined molecular weight (commonly 5 kDa or 10 kDa for research-format preparations) attached at the N-terminus through standard PEGylation chemistry (mPEG-aldehyde or mPEG-NHS-ester). The PEG molecular weight contribution dominates the overall hydrodynamic radius and pharmacokinetic profile of the conjugate.

The IGF1 gene produces alternatively spliced mRNAs encoding pre-pro-IGF-1 precursors with distinct E-peptide C-terminal extensions. In humans, three principal IGF-1 isoforms are recognized: IGF-1Ea (the most abundant form in most tissues including liver), IGF-1Eb (a minor liver-expressed form), and IGF-1Ec (mechano growth factor, MGF; the form upregulated in skeletal muscle in response to mechanical loading and damage). All three isoforms produce the same mature IGF-1 hormone (a 70-amino-acid B-C-A-D domain peptide) after proteolytic cleavage of the E-peptide extension; the distinctive feature of each isoform is the specific C-terminal E-peptide sequence (Ea, Eb, or Ec), which is hypothesized to have biological activity in its own right after release from the pro-IGF-1 precursor.

The Ec/MGF C-terminal peptide has been characterized in skeletal-muscle research as a satellite-cell-activating signal distinct from mature IGF-1. The proposed mechanism is that mechanical loading and damage of skeletal muscle upregulates MGF (IGF-1Ec) splicing, the pro-IGF-1Ec precursor is processed to release both mature IGF-1 (which has the well-characterized IGF-1 anabolic-signaling effects through the IGF-1 receptor) and the free Ec/MGF C-terminal peptide (which is hypothesized to act on satellite cells — the muscle stem cell population — to promote their activation, proliferation, and contribution to muscle regeneration). The receptor target of the free Ec/MGF C-terminal peptide is not definitively established; it is hypothesized to be distinct from the IGF-1 receptor (because the peptide lacks the IGF-1 receptor-binding domain) and may involve a receptor specific to the C-terminal sequence or a heparan-sulfate-proteoglycan-mediated mechanism.

The published research on Ec/MGF peptides in skeletal-muscle biology has included cultured satellite-cell studies (with reports of proliferation and activation effects), in-vivo rodent muscle-damage and exercise-loading studies (with reports of satellite-cell activation, muscle hypertrophy, and regenerative response), and pharmacological studies of the PEGylated form supporting practical dosing schedules in preclinical work. The Goldspink laboratory and collaborating groups have produced the principal body of MGF and Ec/MGF research literature.

It is important to be clear about what PEG-MGF is not. It is not mature IGF-1 — the molecule is the C-terminal Ec/MGF peptide alone, not the IGF-1 hormone. It is not a growth-hormone substitute — MGF is a downstream IGF-1 splice variant relevant to skeletal-muscle biology but does not substitute for the broader endocrine functions of growth hormone. It is not an approved medicine — there are no approved indications for MGF, Ec/MGF peptides, or PEG-MGF in any jurisdiction. And it is not appropriate for non-research use — the published evidence is preclinical mechanistic work in cells and rodents, and the molecule is supplied as a research-supply peptide for laboratory use only. Use of MGF or PEG-MGF in any sports-performance or doping context would be prohibited under the World Anti-Doping Code, which bans peptide hormones and growth factors including IGF-1 and its analogs.

Insulin-like growth factor 1 was originally identified as the principal mediator of the postnatal somatotrophic growth effects of pituitary growth hormone, established through the somatomedin hypothesis of Daughaday, Salmon, and others in the 1950s and 1960s. The IGF-1 cDNA was cloned in the 1980s, establishing the molecular structure of the mature IGF-1 70-amino-acid peptide and the pro-IGF-1 precursor with E-peptide C-terminal extension. The alternative splicing of the IGF1 gene producing distinct E-peptide isoforms (Ea, Eb, Ec) was characterized through the 1980s and 1990s.

The recognition that one of these splice variants — IGF-1Ec, subsequently named mechano growth factor (MGF) based on its upregulation by mechanical loading and damage in skeletal muscle — has skeletal-muscle-specific biology emerged from the work of Geoffrey Goldspink and colleagues at University College London beginning in the 1990s. The Goldspink laboratory characterized the muscle-specific upregulation of MGF in response to stretch, exercise, and damage in animal models, and proposed that the unique C-terminal Ec peptide acts on satellite cells to promote regenerative muscle growth. Subsequent research from the Goldspink group and others characterized synthetic Ec/MGF C-terminal peptides in cultured satellite-cell systems and in in-vivo muscle-damage models with reports of satellite-cell activation and regenerative effects.

The pharmacological limitation of the native Ec/MGF C-terminal peptide is rapid clearance and degradation in vivo (plasma half-life on the order of minutes). PEGylation — covalent conjugation of polyethylene glycol — is a well-established strategy in protein and peptide pharmaceutical chemistry to extend plasma half-life through reduced renal clearance (the PEG-conjugated molecule exceeds the size cutoff for glomerular filtration) and reduced proteolytic degradation (the PEG chain provides steric protection against protease access). PEG-MGF as a research-format preparation applies this strategy to the Ec/MGF C-terminal peptide, providing a substantial extension of in-vivo exposure that supports practical dosing schedules in preclinical pharmacology research.

The clinical-translational development of MGF or Ec/MGF peptides has not advanced to approved medicines for any indication. There are no FDA, EMA, or equivalent regulatory approvals for any MGF/Ec-MGF-based therapeutic, and there are no large clinical-research programs publicly described for the molecule. The published evidence base is preclinical in-vitro and rodent in-vivo work on the Ec/MGF satellite-cell activation hypothesis, and use of PEG-MGF as a research-supply peptide for laboratory work in skeletal-muscle biology.

It is important to note that any non-research use of IGF-1, MGF, or related peptide hormones and growth factors in sports-performance contexts would be prohibited under the World Anti-Doping Code (S2 category of prohibited substances: "Peptide Hormones, Growth Factors, Related Substances and Mimetics"). The research-supply context of this page is academic and laboratory skeletal-muscle and satellite-cell research only.

The IGF1 gene structure includes six exons in humans, with alternative splicing producing distinct mRNA isoforms that encode pre-pro-IGF-1 precursors with different signal-peptide and E-peptide C-terminal sequences. The mature IGF-1 hormone (a 70-amino-acid B-C-A-D domain peptide structurally related to insulin) is the same in all isoforms; the differences are in the signal peptide (which is removed during secretion) and the E-peptide C-terminal extension of the pro-IGF-1 precursor (which is removed by proteolytic processing). In humans, three principal isoforms are recognized: IGF-1Ea (exons 1-2-3-4-6, the most abundant form in most tissues including liver, with E-peptide encoded by parts of exons 4 and 6); IGF-1Eb (exons 1-2-3-4-5, with E-peptide encoded by parts of exons 4 and 5; a minor liver-expressed form); and IGF-1Ec or MGF (exons 1-2-3-4-5-6, with E-peptide containing sequence from exons 4, 5, and 6; the form upregulated in skeletal muscle in response to mechanical loading and damage).

The principal observation that motivated the MGF research program is that IGF-1Ec / MGF mRNA expression is rapidly upregulated in skeletal muscle in response to mechanical loading (resistance exercise), passive stretch, and tissue damage in animal models, with kinetics distinct from the upregulation of IGF-1Ea in the same context. This temporal pattern suggested that MGF has a specific role in the early phase of muscle regenerative response, distinct from the longer-acting role of secreted IGF-1Ea-derived mature IGF-1.

The proposed mechanism is that processing of pro-IGF-1Ec releases both mature IGF-1 (which signals through the IGF-1 receptor with well-characterized PI3K/Akt and MAPK downstream effects on muscle protein synthesis, satellite-cell proliferation, and other anabolic effects) and the free Ec/MGF C-terminal peptide. The free Ec/MGF peptide is hypothesized to act on satellite cells — the resident muscle stem cell population that lies between the basal lamina and the sarcolemma of muscle fibers and that is responsible for postnatal muscle growth and regeneration — to promote their activation from the quiescent state, proliferation, and contribution to repair of damaged muscle fibers. The receptor target of the free Ec/MGF peptide is not definitively established; it is hypothesized to be distinct from the IGF-1 receptor (the C-terminal Ec peptide lacks the IGF-1 receptor-binding domain of mature IGF-1) and may involve a receptor specific to the C-terminal sequence or heparan-sulfate-proteoglycan-mediated mechanisms.

Cultured satellite-cell studies have reported effects of synthetic Ec/MGF peptides on satellite-cell proliferation, on expression of myogenic regulatory factors (Pax7, MyoD, myogenin), and on resistance to fusion (with the proposal that the Ec peptide promotes proliferative expansion of the satellite-cell population before subsequent fusion-mediated contribution to muscle-fiber repair). In-vivo rodent muscle-damage models (cardiotoxin injection, mechanical injury, exercise loading) have characterized satellite-cell activation, muscle hypertrophy, and regenerative-response endpoints with administration of Ec/MGF peptides.

PEGylation pharmacochemistry: polyethylene glycol is a flexible, hydrophilic, non-immunogenic polymer that is widely used in protein and peptide pharmaceutical chemistry to extend plasma half-life. The PEG chain increases the hydrodynamic radius of the conjugate, raising the effective molecular size above the glomerular filtration cutoff and substantially reducing renal clearance. The PEG chain also provides steric protection against protease access and antibody-mediated clearance, reducing degradation and immune-mediated removal. The trade-off is that PEG conjugation can reduce intrinsic receptor-binding affinity (the PEG chain partially shields the active-peptide surface from receptor engagement), so PEGylation chemistry and conjugation-site selection are typically optimized to balance pharmacokinetic extension against retained receptor activity. Multiple approved pharmaceutical proteins use PEGylation (PEG-interferons, PEG-asparaginase, PEG-G-CSF, others) and the chemistry is well-established for research-format peptide conjugates as well.

Distinguishing PEG-MGF from related areas: the molecule is not mature IGF-1 (and is not a substitute for IGF-1 in research applications requiring mature-IGF-1 effects through the IGF-1 receptor); it is not IGF-1 LR3 (long-R3-IGF-1, a synthetic IGF-1 variant with modified IGFBP binding used in research as a long-acting IGF-1 form); and the satellite-cell-activation mechanism is specifically the proposed Ec/MGF pharmacology, distinct from IGF-1-receptor-mediated effects.

PEG-MGF consists of a synthetic peptide corresponding to the C-terminal Ec/MGF sequence of pro-IGF-1Ec, conjugated to polyethylene glycol at the N-terminus. The Ec/MGF peptide is approximately 24 amino acids in length, with the sequence corresponding to the unique C-terminal extension produced by exon-5 inclusion in the IGF-1Ec splice variant. The PEG conjugate is typically a methoxy-polyethylene-glycol (mPEG) of 5 kDa or 10 kDa molecular weight attached through N-terminal amine-targeted chemistry (mPEG-aldehyde for selective N-terminal modification, or mPEG-NHS-ester for less selective amine targeting).

The peptide portion provides the molecular-recognition activity (the Ec/MGF sequence engaging its proposed satellite-cell receptor). The PEG portion provides the pharmacokinetic extension and the dominant contribution to overall hydrodynamic size and plasma circulation properties.

Research-grade PEG-MGF is produced by solid-phase peptide synthesis of the Ec/MGF peptide followed by PEGylation, purified to remove unreacted peptide, unreacted PEG, and conjugates of incorrect stoichiometry. The product is characterized by analytical HPLC (typically reversed-phase and size-exclusion methods to confirm conjugation and stoichiometry) and by mass spectrometry. The product is supplied as a sterile lyophilized powder in sealed vials. Lyophilized storage is at -20 °C or below in moisture-protected containers; reconstituted solutions in aqueous diluent are stored refrigerated and used within a defined window per peptide-stability practice. The PEG conjugate confers good aqueous solubility and good solid-state and solution stability.

In published preclinical skeletal-muscle and satellite-cell research, PEG-MGF and the unmodified Ec/MGF peptide have been used in several principal application areas:

Cultured satellite-cell research. Primary murine and human satellite cells isolated from skeletal muscle are treated with Ec/MGF peptide preparations to investigate effects on proliferation (BrdU incorporation, Ki67 staining), on expression of myogenic regulatory factors (Pax7 for satellite-cell identity, MyoD and myogenin for activation and differentiation progression), and on fusion behavior in differentiation cultures.

Cultured muscle-cell-line research. C2C12 mouse myoblasts and other muscle-cell lines are used as more tractable cell-culture systems to investigate Ec/MGF effects on myoblast biology, including proliferation, differentiation kinetics, myotube formation, and IGF-1-receptor-pathway-independent signaling.

In-vivo muscle damage and regeneration models. Cardiotoxin-induced muscle injury, mechanical-injury models, and chemical-injury models in mice are used to evaluate PEG-MGF administration for effects on satellite-cell activation kinetics, on regenerative myofiber formation, and on functional muscle recovery.

Exercise-loading and hypertrophy models. Mechanical-overload models (synergist ablation, resistance-training models) in rodents are used to evaluate PEG-MGF administration for effects on overload-induced muscle hypertrophy and on the satellite-cell contribution to hypertrophic growth.

Aging and sarcopenia preclinical models. Aged-rodent muscle research is used to investigate Ec/MGF peptide effects on the age-associated decline in satellite-cell number and activation capacity, on muscle regeneration kinetics in aged versus young animals, and on age-related changes in MGF splicing and expression.

Comparative IGF-1 isoform pharmacology. PEG-MGF is used alongside mature IGF-1, IGF-1 LR3, and other IGF-1-related research compounds in comparative pharmacology studies to dissect the contributions of IGF-1-receptor-mediated effects versus proposed Ec/MGF-specific satellite-cell effects in muscle-research contexts.

All applications are research-supply context: laboratory and academic use in cultured cell systems and rodent in-vivo models. The peptide is not for human consumption, is not a medicine, and is not appropriate for any non-research use. Use of MGF or IGF-1-related peptides in sports-performance contexts would be prohibited under the World Anti-Doping Code; the research-supply context of this page does not extend to such non-research use.

PEG-MGF sits within the IGF-1 isoform research-pharmacology landscape alongside mature IGF-1, IGF-1 LR3, and other IGF-1-related research compounds.

PEG-MGF is a PEGylated synthetic peptide corresponding to the C-terminal Ec/MGF region of pro-IGF-1Ec (mechano growth factor), a splice variant of insulin-like growth factor 1. The IGF1 gene produces alternatively spliced mRNAs encoding pre-pro-IGF-1 precursors with distinct E-peptide C-terminal extensions; MGF (IGF-1Ec) is the form upregulated in skeletal muscle in response to mechanical loading and damage. The C-terminal Ec peptide released by proteolytic processing of pro-IGF-1Ec has been characterized in skeletal-muscle research as a proposed satellite-cell-activation signal distinct from mature IGF-1, with a receptor target that is not definitively established. The PEGylation provides substantial pharmacokinetic extension over the native short-half-life peptide.

Published preclinical research from the Goldspink laboratory and collaborating groups has investigated MGF and Ec/MGF peptides in cultured satellite-cell systems, in cultured muscle-cell lines (C2C12 myoblasts), in in-vivo rodent muscle-damage and exercise-loading models, and in aging-related muscle research, with reported effects on satellite-cell proliferation, on myogenic-regulatory-factor expression, on regenerative myofiber formation, and on overload-induced muscle hypertrophy.

This page is research educational only. PEG-MGF is not approved as a medicine and is not the subject of any clinical-research program in human subjects. Research-supply PEG-MGF is intended for laboratory and academic skeletal-muscle and satellite-cell research; it is not for human consumption and is not appropriate for any non-research use. Use of MGF or IGF-1-related peptides in sports-performance contexts would be prohibited under the World Anti-Doping Code.