title: Engineering insulin-like growth factor-1 for local delivery.
abstract: Insulin-like growth factor-1 (IGF-1) is a small protein that promotes cell survival and growth, often acting over long distances. Although for decades IGF-1 has been considered to have therapeutic potential, systemic side effects of IGF-1 are significant, and local delivery of IGF-1 for tissue repair has been a long-standing challenge. In this study, we designed and purified a novel protein, heparin-binding IGF-1 (Xp-HB-IGF-1), which is a fusion protein of native IGF-1 with the heparin-binding domain of heparin-binding epidermal growth factor-like growth factor. Xp-HB-IGF-1 bound selectively to heparin as well as the cell surfaces of 3T3 fibroblasts, neonatal cardiac myocytes and differentiating ES cells. Xp-HB-IGF-1 activated the IGF-1 receptor and Akt with identical kinetics and dose response, indicating no compromise of biological activity due to the heparin-binding domain. Because cartilage is a proteoglycan-rich environment and IGF-1 is a known stimulus for chondrocyte biosynthesis, we then studied the effectiveness of Xp-HB-IGF-1 in cartilage. Xp-HB-IGF-1 was selectively retained by cartilage explants and led to sustained chondrocyte proteoglycan biosynthesis compared to IGF-1. These data show that the strategy of engineering a "long-distance" growth factor like IGF-1 for local delivery may be useful for tissue repair and minimizing systemic effects.
authors.affiliation: Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Tomotake
authors.initials: T
authors.lastname: Tokunou
authors.forename: Rachel
authors.initials: R
authors.lastname: Miller
authors.forename: Parth
authors.initials: P
authors.lastname: Patwari
authors.forename: Michael E
authors.initials: ME
authors.lastname: Davis
authors.forename: Vincent F M
authors.initials: VF
authors.lastname: Segers
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Grodzinsky
authors.forename: Richard T
authors.initials: RT
authors.lastname: Lee
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001665:Binding Sites; D006493:Heparin / Q000378:metabolism; D066257:Heparin-binding EGF-like Growth Factor; D007334:Insulin-Like Growth Factor I / Q000008:administration & dosage / Q000235:genetics*; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics*; D051379:Mice; D011485:Protein Binding; D015202:Protein Engineering / Q000379:methods*; D051381:Rats; D011993:Recombinant Fusion Proteins
chemical_list: C587884:Hbegf protein, mouse; C587885:Hbegf protein, rat; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D011993:Recombinant Fusion Proteins; D007334:Insulin-Like Growth Factor I; D006493:Heparin