PEG-MGF

PEG-MGF is a polyethylene glycol-conjugated form of the peptide known as mechano growth factor. MGF corresponds to the 24 C-terminal residues of the E domain of IGF-1Eb, a splice variant of the IGF-1 gene generated by alternative splicing across exons 4, 5 and 6; the reading-frame shift yields a distinct C-terminal sequence not present in mature IGF-1. The synthetic peptide is what is studied under the MGF name, and no analogous peptide product of the Igf1 gene has been isolated from cultured cells, conditioned medium, or animal tissues or fluids. PEGylation is a conjugation strategy used with peptides of this kind to extend duration of activity.

PEG-MGF in the research literature

Reported activities of the synthetic E-domain peptide are mixed. In cell culture it has been described as increasing the proliferative life span of myogenic satellite cells and their fusion potential, and as a motogenic factor for myogenic precursor cells, modulating u-PA, u-PAR, MMP-7 and PAI-1 by a route that appears not to involve the IGF-1 receptor. Transgenic mice overexpressing MGF showed more BrdU-positive proliferating cells in the dentate gyrus and subventricular zone, and MGF increased the size and number of neurospheres from subventricular-zone neural stem cells in vitro.

Two laboratories, however, reported that the peptide at concentrations up to 500 ng/ml produced no measurable change in proliferation or differentiation of C2C12 myoblasts or primary skeletal muscle stem cells, and no activation of p-ERK in cardiac myocytes, while mature IGF-1 gave a clear response in the same assays. On PEGylation itself, C-terminally PEGylated analogs of a different releasing peptide retained potency in vitro and showed longer duration of activity in pig and mouse models, illustrating the general effect of the polymer.