Large-scale production of biologically active human keratinocyte growth factor-2

High-level production of keratinocyte growth factor 2 in Escherichia coli

Recombinant human keratinocyte growth factor 2 (KGF-2), also known as repifermin, is used in various therapeutic applications. However, KGF-2 production has not been optimized for facilitating large-scale production. Therefore, we attempted to attain high-level production of bioactive KGF-2. KGF-2 was fused with 6HFh8 (6HFh8-KGF-2) at the tobacco etch virus protease cleavage site. The 6HFh8-KGF-2 was expressed in Escherichia coli with high expression levels of approximately 33% and 20% of soluble protein in flask culture and 5 L fermentation, respectively. 6HFh8-KGF-2 was purified via nickel affinity chromatography. To maintain a stable form of KGF-2, the conditions of the cleavage reaction were optimized based on the isoelectric point. KGF-2 was purified via ion-exchange chromatography to high purity (>99%) with an optimal purification yield (91%). Circular dichroism spectroscopy demonstrated that purified KGF-2 had a secondary structure and thermal stability similar to that of commercial KGF-2. Bioactivity assays indicated that purified KGF-2 could induce MCF-7 cell proliferation in the same manner as commercial KGF-2. These results demonstrate that bioactive KGF-2 was overexpressed in E. coli and purified to high quality. Our findings indicated that bioactive KGF-2 can be produced in large quantities in E. coli.

Toxicity Evaluation of Long-Term Topical Application of Recombinant Human Keratinocyte Growth Factor-2 Eye Drops on Macaca Fascicularis

Recombinant human keratinocyte growth factor-2 (rhKGF-2), an effective agent for the regeneration of epithelial tissue, was found to have great potential for use in treatments of corneal diseases that involve corneal epithelial defects. Furthermore, the safety of long-term and high-dose external use of KGF-2 eye drops in rabbits has been well established previously. The aim of this study is to determine the safe dose range and target organs for toxicity of rhKGF-2 eye drops in Macaca fascicularis (M. fascicularis). The M. fascicularis animals were administered with different doses of rhKGF-2 eye drops (125, 500, and 2000 μg/ml) for four consecutive weeks, followed by a 2 week recovery period. No significant differences in weight, electrocardiogram characteristics, blood and urine indexes, pathology, and bone marrow cells were detected among the animals in different groups. The corneas of some animals in the middle- and high-dose groups showed fluorescence when stained with sodium fluorescein, and then the staining disappeared on days 28 and 42. Anti-rhKGF-2 antibodies were detected in a small number of animals in the high-dose group, and their level decreased after rhKGF-2 withdrawal. No neutralizing antibodies were detected. The result demonstrated that there was no obvious adverse reaction when topical application of rhKGF-2 eye drops at the dosage of 125 or 500 μg/ml on the M. fascicularis. This study is of great significance for the future clinical transformation of rhKGF-2 eye drops.

Large-Scale Preparation of Highly Stable Recombinant Human Acidic Fibroblast Growth Factor in Escherichia coli BL21(DE3) plysS Strain

In this study, the optimum human aFGF gene encoding haFGF₁₃₅ was cloned in pET3c and transferred to Escherichia coli BL21(DE3) plysS. To enhance the yield of fermentation and the expression level of the target protein, the fermentation parameters, including temperature, pH, dissolved oxygen, glucose concentration, ammonium chloride concentration, induction time, and inducer (IPTG) concentration, were optimized. The optimized fermentation parameters were used in large-scale fermentation (30 L). Ion-exchange and heparin-affinity column chromatography techniques were used for separation and purification of rhaFGF₁₃₅ protein. HPLC, isoelectric focusing electrophoresis, and mass spectrometry were used to detect the purity, isoelectric point, and molecular weight and peptide map of rhaFGF₁₃₅ protein, respectively. Mitogenic activity of rhaFGF₁₃₅ protein was detected in NIH-3T3 cells and a full-thickness injury wound diabetic rat model. The production and expression level of rhaFGF₁₃₅ in the 30-L scale fermentation reached 80.4 ± 2.7 g/L culture and 37.8% ± 1.8%, respectively. The RP-HPLC and SDS-PAGE purity of the final rhaFGF₁₃₅ product almost reached 100%, and the final pure protein yield was 158.6 ± 6.8 mg/L culture. Finally, the cell and animal experiments showed that rhaFGF₁₃₅ retained a potent mitogenic activity. The large-scale process of rhaFGF₁₃₅ production reported herein is relatively stable and time-saving, and thus, it can be used as an efficient and economic strategy for the synthesis of rhaFGF₁₃₅ at the industrial level.

High-efficiency production of bioactive recombinant human fibroblast growth factor 18 in Escherichia coli and its effects on hair follicle growth

Using fusion tags, expression of recombinant human fibroblast growth factor 18 (rhFGF18) in mammalian cells and Escherichia coli has been extensively used for fundamental research and clinical applications, including chondrogenesis and osteogenesis, hair growth, and neuroprotection. However, high-level rhFGF18 expression is difficult and the products are often not homogeneous. Furthermore, fusion-tagged protein has higher immunogenicity and lower bioactivity, and the removal of the fused tag is expensive. To overcome the limitations of fusion-tagged expression of protein and to prepare soluble highly bioactive rhFGF18, we have developed a rapid and efficient expression strategy. Optimized hFGF18 gene was amplified by polymerase chain reaction and cloned into pET22b and pET3c vectors, then transformed into E. coli strains Origima (DE3) and BL21 (DE3)PlysS. The best combination of plasmid and host strain was selected, and only Origima (DE3)/pET3c-rhFGF18 was screened for high-level expressed rhFGF18. Under optimal conditions in a 30-L fermentor, the average bacterial yield and expression level of rhFGF18 of three batches were more than 652 g and 30 % respectively, after treatment with 1 mM isopropyl-thio-β-galactopyranoside for 10 h at 25 °C. The target protein was purified by CM Sepharose FF and heparin affinity chromatography. The purity of rhFGF18 was shown by HPLC to be higher than 95 %, and the yield was 155 mg/L. In vitro MTT assays demonstrated that the purified rhFGF18 could stimulate significant proliferation of NIH3T3 cells, and animal experiments showed that rhFGF18 could effectively regulate hair growth. In conclusion, this may be a better method of producing rhFGF18 to meet the increasing demand in its pharmacological application.