Purification and modification by polyethylene glycol of a new human basic fibroblast growth factor mutant-hbFGF(Ser25,87,92)

Fibroblast growth factor 2 dimer with superagonist in vitro activity improves granulation tissue formation during wound healing

Site-specific chemical dimerization of fibroblast growth factor 2 (FGF2) with the optimal linker length resulted in a FGF2 homodimer with improved granulation tissue formation and blood vessel formation at exceptionally low concentrations. Homodimers of FGF2 were synthesized through site-specific linkages to both ends of different molecular weight poly(ethylene glycols) (PEGs). The optimal linker length was determined by screening dimer-induced metabolic activity of human dermal fibroblasts and found to be that closest to the inter-cysteine distance, 70 Å, corresponding to 2 kDa PEG. A straightforward analysis of the kinetics of second ligand binding as a function of tether length showed that, as the polymerization index (the number of monomer repeat units in the polymer, N) of the tether decreases, the mean time for second ligand capture decreases as ∼N(3/2), leading to an enhancement of the number of doubly bound ligands in steady-state for a given (tethered) ligand concentration. FGF2-PEG2k-FGF2 induced greater fibroblast metabolic activity than FGF2 alone, all other dimers, and all monoconjugates, at each concentration tested, with the greatest difference observed at low (0.1 ng/mL) concentration. FGF2-PEG2k-FGF2 further exhibited superior activity compared to FGF2 for both metabolic activity and migration in human umbilical vein endothelial cells, as well as improved angiogenesis in a coculture model in vitro. Efficacy in an in vivo wound healing model was assessed in diabetic mice. FGF2-PEG2k-FGF2 increased granulation tissue and blood vessel density in the wound bed compared to FGF2. The results suggest that this rationally designed construct may be useful for improving the fibroblast matrix formation and angiogenesis in chronic wound healing.

Expression and purification of biologically active human FGF2 containing the b'a' domains of human PDI in Escherichia coli

Among the members of the fibroblast growth factor (FGF) family that affect the growth, differentiation, migration, and survival of many cell types, FGF2 is the most abundant in the central nervous system. Because of its wound healing effects, FGF2 has potential as a therapeutic agent. The protein is also added to the culture media to maintain stem cells. Expression and purification procedures for FGF2 that are highly efficient and low cost have been intensively investigated for the past two decades. Our current study focuses on the purification of FGF2 fused with b'a' domains of human protein disulfide isomerase to elevate overexpression, solubility, and stability with a simplified experimental procedure using only ion exchange chromatography, as well as on the confirmation of the biological activity of FGF2 on fibroblast Balb/c 3T3 cells and hippocampal neural cells.

A heparin-mimicking polymer conjugate stabilizes basic fibroblast growth factor

Basic fibroblast growth factor (bFGF) is a protein that plays a crucial role in diverse cellular functions, from wound healing to bone regeneration. However, a major obstacle to the widespread application of bFGF is its inherent instability during storage and delivery. Here, we describe the stabilization of bFGF by covalent conjugation with a heparin-mimicking polymer, a copolymer consisting of styrene sulfonate units and methyl methacrylate units bearing poly(ethylene glycol) side chains. The bFGF conjugate of this polymer retained bioactivity after synthesis and was stable to a variety of environmentally and therapeutically relevant stressors--such as heat, mild and harsh acidic conditions, storage and proteolytic degradation--unlike native bFGF. Following the application of stress, the conjugate was also significantly more active than the control conjugate system in which the styrene sulfonate units were omitted from the polymer structure. This research has important implications for the clinical use of bFGF and for the stabilization of heparin-binding growth factors in general.

Chemical modification of recombinant human keratinocyte growth factor 2 with polyethylene glycol improves biostability and reduces animal immunogenicity

Recombinant human keratinocyte growth factor 2 (rhKGF-2) is a member of fibroblast growth factor protein family currently being investigated for its promising significant effects in treating epithelial damage. Molecular modification with polyethylene glycol (PEGylation) is an effective approach to improve protein biostability and decrease protein immunogenic activity. In this study, we modified rhKGF-2 through PEGylation at N-terminal residue using 20 kDa PEG-phenyl-isothiocyanate (PIT-PEG20K). PEGylated rhKGF-2 is then purified to near homogeneity by Sephadex G-25 gel filtration followed by a Heparin Sepharose TM CL-6B affinity chromatography. This PEGylated rhKGF-2 retained about 60% of mitogenic activity compared to the non-modified rhKGF-2. Its relative thermal stability at normal physiological temperature and structural stability were significantly enhanced. Moreover, the immunogenicity of PEGylated rhKGF-2 in mice is significant decreased compared to non-modified rhKGF-2. These results suggest that PEGylation of rhKGF-2 could be a more effective approach to the pharmacological and therapeutic application of rhKGF-2.