BACKGROUND: At present,enhanced green fluorescent protein(EGFP)is proved to be the best labeled molecule,with unique advantages,such as high fluorescence specificity,easy to be detected,and so on.Recombined retroviral vector EGFP-pLNCX2,which can stably express EGFP,can be construct using gene-engineering technique.Transfecting allogenic chondrocytes is indeed very useful to investigate the target gene expression and process of constructing tissue engineered cartilage in vivo.OBJECTIVE:To construct recombined retroviral vector EGFP-pLNCX2 which can stably express EGFP,and investigate optimal conditions for retrovirus transfection of chondrocytes.DESIGN:Randomized controlled observation.SETTING:Shanghai Jiao Tong University.MATERIALS:Thirty New Zealand rabbits of either gender,1 week of age,were purchased from Experimental Animal Center of Chinese Academy of Sciences.Amphotropic retrovirus package cell line PT67 pLNCX2 and pEGEP-C1 were purchased from Clontech Company;NIH 3T3 cell line was purchased from ATCC Company;DH5a Bacterium coli was preserved by the laboratory of Shanghai Jiao Tong University;Retroviral vector pLNCX2 was purchased from Clontech Company;pEGFP-C1 plasmid with EGFP were donated by professor Cong Xiao-qian from Chinese Academy of Sciences.METHODS:This experiment was carried out in the Shanghai Jiao Tong University in August 2005.Chondrocytes of New Zealand rabbits were isolated and cultured.The recombinant retroviral vector EGFP-pLNCX2,which can stably express EGFP,was constructed to transfect cultured chondrocytes from New Zealand rabbits by using gene engineering technique.Transfection results were observed under fluorescence microscope.Altogether 6×105 chondrocytes incubated in 10 cm-diameter flat plate were used to transfect retrovirus-EGFP immediately and at 12,24 and 48 hours after inoculation.One week later,EGFP expression efficiency was measured with flow cytometer,and best occasion for retrovirus transfecting primary chondrocytes.Enzyme-digested chondrocytes were inoculated for 24 hours to transfect retrovirus.After 250 mg/L G418 was added,chondrocytes were screened on the 2nd,3rd,4th,5th and 6th days separately.After phosphate buffer solution(PBS)washings,the transfection efficiency of chondrocytes was detected by flow cytometer,and the best occasion for G418 screening was observed.MAIN OUTCOME MEASURES:①EGFP-pLNCX2 transfection efficiency.②The best occasions for retrovirus transfecting primary chondrocytes and G418 screening.RESULTS: ①Retroviral vector EGFP-pLNCX2 transfected primary chondrocytes of rabbits,and high expression of transfected chondrocytes could be obtained through preliminary screening of G418.After being screened and expressing EGFP,chondrocytes kept normal morphology,with pseudopod adhering to the wall and matrix secreting vigorously.②The best occasion for retrovirus transfecting primary chondrocytes was at 24 hours after cell inoculation.The transfection efficiency determined with flow cytometer was 19.14% on the 5th day.The best occasion for G418 screening was on the 5th day after culture.Transfection efficiency of G418 screening was 55.75% on the 7th day.CONCLUSION:Recombinant retroviral vector EGFP-pLNCX2 can effectively transfect chondrocytes.The best occasion for retrovirus transfecting primary chondrocytes is at 24 hours after inoculation, and the best occasion for G418 screening is on the 5th day after culture.