Objective      To observe CTLA-4Ig protein expression in human marrow mesenchymal  stem cells (hMSCs) transfected with adenovirus-mediated CTLA-4Ig gene and the effect of gene modification on hMSCs induced osteogenesis.       Methods      hMSCs were transfected with adenovirus-mediated CTLA-4Ig gene. The transfection efficiency was identified by observing GFP expression and using FACS detection. The cell shape and cell cycle was compared before and after transfection. CTLA-4Ig protein expression in transfected hMSCs was detected by immunocytochemical method. After induction culture for 3 weeks

the specific markers for osteogenesis were examined.       Results      The isolated and cultured hMSCs were positive for CD105 and negative for CD34. The transfection efficiency of recombinant adenovirus-mediated CTLA-4Ig gene transfection was 81.14%. hMSCs with CTLA-4Ig gene (CTLA-4Ig-hMSCs) did not show marked changes in cell shape and growth. Immunocytochemical detection showed positive CTLA-4Ig expression in CTLA-4Ig-hMSCs and strongly positive alkali phosphatase staining

as well as positive expression of osteocalcin. Macrocyclin fluorescent labeling indicated there were calcium deposits among hMSCs.       Conclusion      hMSCs modified with CTLA4Ig gene can secrete target protein CTLA4Ig and maintain the characteristics of osteogenesis

which has the potential for repairing bone-defect in the bone tissue engineering.