PEG-MGF

PEG-MGF (PEGylated mechano growth factor) is a synthetic peptide based on the E-domain of mechano growth factor (MGF), with a polyethylene glycol (PEG) chain attached. MGF is an IGF-1 splice variant, IGF-1Ec in humans and IGF-1Eb in rodents, first found by Goldspink's laboratory in stretched rabbit muscle (Yang et al., 1996); most papers used a synthetic copy of the last 24 residues of its E-domain (Matheny et al., 2010).

As of October 2026, PubMed indexes no primary study of PEG-MGF itself, and a 2026 review found no peer-reviewed human studies of it (Dominikowski et al., 2026).

PubChem has only supplier entries for PEG-MGF, with no defined structure.

Published work relevant to PEG-MGF falls into six areas, each summarized with its model. None of the primary studies tested PEG-MGF or gave the peptide to people.

IGF-1 splicing and the original MGF work

The IGF-1 gene is spliced into isoforms that share mature IGF-1 but end in different E-peptides. In rabbit muscle under active stretch, Goldspink's laboratory cloned an extra isoform, IGF-1Eb (Ec in humans), whose E-domain carries a 52 base pair insert that shifts the reading frame. It appeared within hours to days of altered activity and was nearly absent in control muscle (Yang et al., 1996). The transcript was named mechano growth factor for its apparent role in muscle remodeling (Matheny et al., 2010). Model: rabbit skeletal muscle.

The E-domain peptide in muscle cells

In C2C12 mouse myoblasts, the MGF E-domain peptide increased proliferation and inhibited terminal differentiation, unlike mature IGF-1, and an antibody blocking the IGF-1 receptor did not prevent this (Yang and Goldspink, 2002). In human myogenic precursor cells, the 24-residue peptide, named MGF-Ct24E, increased migration and raised u-PA, u-PAR and MMP-7 expression, by a route the authors suggested bypassed the IGF-1 receptor (Mills et al., 2007). Models: mouse and human muscle cells in culture.

Heart and brain injury models

In sheep with induced infarcts, the E-domain peptide preserved cardiac function, with 35 percent less compromised myocardium than controls at eight days (Carpenter et al., 2008). In mice, a synthetic E-domain analog given at infarction preserved contractility at 2 weeks, and in H9c2 rat cardiomyoblasts it entered cells without IGF-1 receptor activation and blocked stress-induced apoptosis (Mavrommatis et al., 2013).

In gerbils with transient brain ischemia, the C-terminal peptide protected vulnerable neurons, and in hippocampal slice cultures its effect outlasted that of IGF-1 (Dluzniewska et al., 2005). In 6-hydroxydopamine-lesioned rats, the 24-residue peptide reduced nigral dopamine neuron loss (Quesada et al., 2009). Models: sheep, mice, gerbils, rats, and cell and slice cultures.

Bone and cartilage cells

In MC3T3-E1 mouse osteoblast-like cells, MGF-Ct24E stimulated proliferation 1.4 times more than IGF-1. In rabbits with 5 mm radius defects given 28.5 or 57 µg/kg on five days, the higher amount raised the radiographic closure rate and histology scores over no peptide (Deng et al., 2011).

Piglet growth plate cartilage expressed MGF, but adding MGF peptides to growth plate chondrocyte cultures did not change proliferation (Schlegel et al., 2013). A 2019 study of the peptide in rat intervertebral disc cells was retracted by its journal in 2024 (Xu et al., 2019). Models: mouse, piglet and rat cells, and rabbits.

Failed replications and the debate over MGF

Teams at two pharmaceutical companies could not reproduce the core cell findings: at up to 500 ng/ml, the peptide did not change proliferation or differentiation of C2C12 cells, primary human myoblasts or primary mouse muscle stem cells, though mature IGF-1 stimulated proliferation (Fornaro et al., 2014). With synthetic rodent E-peptides in C2C12 cells, another group found that signaling, proliferation and migration effects depended on the IGF-1 receptor (Brisson and Barton, 2012).

A 2010 review noted that no peptide matching synthetic MGF had been isolated from cells, tissues or body fluids (Matheny et al., 2010). In mice with contused, macrophage-depleted calf muscle, an MGF peptide did not change fiber regeneration, though fibrosis fell (Liu et al., 2019). Models: mouse and human muscle cells and mice.

Why PEG was added, and what is known about PEG-MGF

Stabilized versions of the E-domain peptide also exist; in the replication study, neither a stabilized nor the native peptide activated ERK in cardiac myocytes (Fornaro et al., 2014).

A 2026 review notes that PEGylation is promoted commercially to raise stability and prolong exposure, but that evidence cited for PEG-MGF comes from MGF biology and synthetic E-domain peptides, that PEGylation changes pharmacokinetics and tissue exposure so native-peptide effects cannot be assumed for the conjugate, and that no half-life has been reported. It rates PEG-MGF in its lowest evidence tier (Dominikowski et al., 2026). Models: cardiac myocytes and a literature review.