ABSTRACT
Objective To investigate efficiency and distribution of gene delivery to the injured tendons by microinjeetion and tissue reactions caused by different vectors. Methods By using a mi-croinjection technique, 10μl of pCMV-EGFP, pCAGGS-EGFP, AAV2-EGFP and Ad5-EGFP harboring enhanced green fluorescence protein (EGFP) gene were respectively injected to two sites of the proximal stump of 48 transected digital flexor tendons in 18 chickens. At days 3, 7, 14 and 21, the tendons wereharvested for observing distribution and expression of EGFP under a fluorescence microscope by using fro-zen tissue sections. The tendon sections were also stained with hematoxylin and eosin to examine inflam-mation caused by these vectors. The other 24 normal flexor tendons were served as controls. ResultsCompared with normal tendon tissues, the EGFP expression was observed in tendons at days 3, 7, 14 and21 after injection. The EGFP expression was observed at day 3 and reached peak at day 7 for all vectors.The EGFP expression was decreased at day 14 but seldom seen at day 21. EGFP was distributed evenly inthe injected tendon segment adjacent to the cut level. The EGFP expression in the tendons injected withAAV2-EGFP and Ad5-EGFP was higher than that with pCMV-EGFP and pCAGGS-EGFP injection, withinsignificant statistical difference upon the EGFP expression between AAV2-EGFP and Ads-EGFP vec-tors. Tissue reactions of the tendons caused by the liposome-plasmid vector ( including pCMV-EGFP and pCAGGS-EGFP) were the most prominent among all vectors. Infiltration of inflammatory cells, chiefly lymphocytes and neutrophilic granulocytes, were found. The tendons injected with AAV2 vectors presen-ted gentle inflammatory reactions. Conclusions Mieroinjection to two sites of each tendon stump deliv-ers the transgene to the entire tendon segment adjacent to the cut. Gene delivery by the AAV2 and Ad5 vectors has the highest cfficiency among four vectors tested, when expression level peaks at day 7 after in-jection and AAV2 vector causes the slightest tissue reactions in the tendons, indicating that the AAV2 vector is a promising gene delivery vector and microinjection is practical for tendon gene therapy.