BACKGROUND: Human keratinocyte growth factor-2 (hKGF-2) has extensive physiological functions, which plays an important role in embryonic development, tissue-repairing, nervous regeneration, vascularization and development of tumor.OBJECTIVE: To clone hKGF-2 gene, obtain the expression of hKGF-2 in Escherichia coli(E.coli) and determine its bioactivity, so as to provide experimental basis for further investigation.DESIGN: Open experiment.SETTING: Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention.MATERIALS: The experiment was conducted in State Key Laboratory of Viral Genetic Engineering, Institute for Viral Disease Control and Prevention of Chinese Center for Disease Control and Prevention. The temperature control expression vector pBV220 was constructed by State Key Laboratory of Viral Genetic Engineering; EcoR Ⅰ , BamH Ⅰ , T4 DNA ligase (Promega Co., Ltd.); The specific polymerase chain reaction (PCR) of hKGF-2 (Manufactured by Shanghai Boya Biotechnology Co., Ltd.); Heparin-Sepharose CL-6B (Pharmacia Company); PCR rapid purification kit,Trizol kits for total RNA extract, Kits for RT-PCR (GIBCO Co., Ltd.); Kits for rapid extraction of plasmid DNA (Boda Company); BL-21-codon plus compent cells (Stratagene Co., Ltd.).METHODS: High-expression strain BL-21 codon plus competent cells was used to express and purify initially recombinant hKGF-2 protein, and its activity was detected. RT-PCR was adopted to obtain hKGF-2 cDNA from lung tissues of naturally aborted fetus and clone it into pBV220 carri er plasmid. The hKGF-2 protein expressed in BL-21 codon plus competent cells of E.coli. Affinity chromatography and ion exchange chromatography were applied in isolation and purification, and the bioactivity of expression protein was determined in cell proliferation test.MAIN OUTCOME MEASURES: The length and sequence of cDNA segment in hKGF-2, the expression of hKGF-2 gene inE.coli and the purification of hKGF-2 activity.RESULTS: The segment of hKGF-2 cNDA was about 500 bp, and hKGF-2 protein highly expressed in BL-21, which had soluble expression in the supernatant. SDS-PAGE showed that the relative molecular mass was about 20000, and hKGF-2 protein could significantly promote the mitotic activity of NIH3T3 cells. The A value (490 nm) of hKGF-2 in the 1 μg/L, 5 μg/L and 10 μg/L groupswere higher than that in the blank control group, and the differences were significant (which were 0.174±0.022,0.220±0.029,0.306±0.050,0.066±0.004 respectively,P ＜ 0.001).CONCLUSION: hKGF-2 gene is successfully cloned, which highly expresses in BL-21 of the E.coli. Purified hKGF-2 protein can stimulate the proliferation of NIH3T3 cells and significantly promote its mitotic activity.