Expression, purification, and characterization of recombinant mouse nerve growth factor in Chinese hamster ovary cells

•We established and isolated monoclonal rmNGF expression CHO-S cells.•We purified the rmNGF with a high purity.•The rmNGF was analyzed comprehensively.•The structure of rmNGF was identical to the theoretical structure.•The biological activity of rmNGF was comparable with the extracted mNGF on the market.

Mouse NGF (mNGF) extracted from mouse submaxillary gland has been approved on the market in China for treating nerve damage caused by N-hexane poisoning for over a decade, and many researches showed the clinical effectiveness of mNGF for the treatment of other nerve system diseases. The extracted mNGF have risks of potential viral contamination due to the animal origin. Here, we report the successful expression, purification, and characterization of recombinant mNGF (rmNGF). An expression plasmid of mouse nerve growth factor (mNGF) was constructed and transfected into CHO-S cells. Stable transfectants were obtained using a two-phase selection scheme with the addition of different concentrations of methotrexate and puromycin. Recombinant mNGF (rmNGF) was purified from cell culture medium by a two-step procedure: cation exchange followed by size-exclusion chromatography. The purity of rmNGF was 98.6% determined by size exclusion high performance liquid chromatography (SEC-HPLC). The molecular weight, isoelectric point and N-terminal sequence of rmNGF were identical to the theoretical values entirely. In TF-1/MTS, the specific activity of the protein was approximately 1.7 × 106 U/mg against rhNGF (the reference standard). In DRGs, the specific activity was approximately 7.3 × 105 AU/mg against mNGF (the reference standard). Our results showed that a high quality of rmNGF with marked biological activity comparable with mNGF was produced, and laid the basis for further research and development of rmNGF.