Abstract: Objective:To isolate and culture the bone marrow mesenchymal stem cells from LacZ transgenic mouse (LacZ-MSC) and investigate its biological properties. Methods:Adherent method was used to isolate LacZ-MSC from whole bone marrow. After expansion in vitro, the growth characteristics of LacZ-MSC were observed and the cell cycle was analyzed by flow cytometry. The differentiation potential of LacZ-MSC was evaluated by osteogenic and adipogenic induction tests. The LacZ gene expression of LacZ-MSC was detected by X-gal staining. Results:After LacZ-MSC were cultured for 4 days, scattered needlelike adherent cells were observed, and colonies or fibrous fusion were formed between 5 and 8 days after culturing. During expansion in vitro, 1 to 3×10⁵ cells can be obtained after primary culture and the cell counts increased 10⁵-fold at the tenth passage. Then the proliferation ability of cells was gradually decreased. Flow cytometry analysis showed that the percentages of cells in G₀/G₁, G₂/M and S phases were 78.44%, 5.20% and 16.36%, respectively. LacZ-MSC cells had the potentiality to differentiate into bone cells and fat cells. X-gal staining showed that the cells expressed LacZ gene. Conclusion:LacZ-MSC was successfully isolated from the bone marrow of LacZ transgenic mouse, and the isolated cells could proliferatein vitro, indicating that broad application of LacZ-MSC between 3 and 10 passages may be prospected in tissue engineering.