BACKGROUND:: PKH-26 has been successfully applied to label bone marrow mesenchymal stem cells (BMSCs). OBJECTIVE:: To evaluate the effect of PKH-26 on the labeling and tracing of BMSCs via tracheal transplantation and vein transplantation and to detect the migration of labeled BMSCs into the injured sites. METHODS:: BMSCs were cultured by adherence method. PKH-26 labeled 3-5 passage BMSCs were injected into the recipient rats via the tail vein. Rats in the control groups were injected with the same amount of PBS. RESULTS AND CONCLUSION:: After PKH-26 labeling procedure, almost all BMSCs were labeled with red fluorescence under inverted fluorescence microscope, indicating that the labeling method has high sensitivity and efficiency. In vivo tracing showed that red fluorescence was still visible at 8 weeks post-surgery at the recipient and transplanted trachea, with most red fluorescence shown at the anastomotic part. There was basically no red fluorescence visible at the recipient trachea that was further away from the anastomotic site. These indicated that BMSCs can migrate to the impaired trachea after injected via the tail vein. Also, the BMSCs can further migrate from the recipient tracheal edge to the transplanted trachea and finally locate at the implant site. The highly stable PKH-26 red fluorescence in vivo indicated that it can be used in tracing studies that need long-term observation.Han Y, Pang CJ, Lan N, Tong XJ, Shi WJ. Labeling and tracing bone marrow mesenchymal stem cells with PKH-26 in vivo.Zhongguo Zuzhi Gongcheng Yanjiu yu Linchuang Kangfu. 2011;15(45): 8469-8473.[http://www.crter.cn http://en.zglckf.com]