Early expression of marker genes in the rabbit medial collateral and anterior cruciate ligaments: The use of different viral vectors and the effects of injury

Gene therapy is a technique that may offer advantages over current methods of cytokine delivery to ligaments. To determine if implanted genes could be expressed in normal and injured knee ligaments, the medial collateral liga ment and anterior cruciate ligament were studied in 18 rabbits. A retrovira l ex vivo technique using allograft medial collateral ligament and anterior cruciate ligament fibroblasts and an adenoviral in vivo technique were com pared as methods for delivering the LacZ marker gene to knee ligaments. Bil ateral knee surgeries were performed, and the rabbits were equally divided into three groups. Group 1 received the retrovirus and the medial collatera l ligament was ruptured, Group 2 received the adenovirus and the medial col lateral ligament was ruptured, and Group 3 received the adenovirus and the medial collateral ligament was not injured. The anterior cruciate ligament was not injured in any group. The medial collateral and anterior cruciate l igaments of the right knees received 10(6) allografted, transduced ligament fibroblasts or 10(9) adenovirus particles, whereas the ligaments of the le ft knee received a similar volume of saline solution only. Equal numbers of rabbits were killed at 10 days, 3 weeks, and 6 weeks following the procedu re. Ligament samples were stained with X-gal to detect the expression of th e LacZ gene product, beta-galactosidase. LacZ gene expression was evident i n ruptured and uninjured medial collateral ligaments as well as in the ante rior cruciate ligament. The expression lasted between 10 days and 3 weeks i n the medial collateral and anterior cruciate ligaments with use of the ret rovirus and between 3 and 6 weeks in the medial collateral ligament and at least 6 weeks in the anterior cruciate ligament with the adenovirus. The le ngth of gene expression in the ruptured and uninjured medial collateral lig aments did not differ. These preliminary studies indicate that gene transfe r to normal and injured knee ligaments is possible.