1. ¹Center of Molecular Orthopaedics, Harvard Medical School, Boston, MA 02115, USA
2. ²University Hospital of Orthopaedic Surgery, Graz 8036, Austria
3. ³Department of Orthopedic Surgery, Koenig-Ludwig-Haus, Julius-Maximilians-University, Wuerzburg 97074, Germany
4. ⁴Department of Orthopaedic Surgery, Children's Hospital of Boston and Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA

Correspondence: Martha Meaney Murray, Department of Orthopaedic Surgery, Children's Hospital of Boston, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA. Fax: (617) 730-0459. E-mail: marthamurray@childrens.harvard.edu

^*These authors contributed equally to this work.

Received 17 October 2003; Accepted 15 March 2004.

Abstract

The inability of the ruptured anterior cruciate ligament (ACL) of the knee joint to heal spontaneously presents numerous clinical problems. Here we describe a novel, gene-based approach to augment ACL healing. It is based upon the migration of cells from the ruptured ends of the ligament into a collagen hydrogel laden with recombinant adenovirus. Cells entering the gel become transduced by the vector, which provides a basis for the local synthesis of gene products that aid repair. Monolayers of bovine ACL cells were readily transduced by first-generation, recombinant adenovirus, and transgene expression remained high after the cells were incorporated into collagen hydrogels. Using an in vitro model of ligament repair, cells migrated from the cut ends of the ACL into the hydrogel and were readily transduced by recombinant adenovirus contained within it. The results of experiments in which GFP was used as the transgene suggest highly efficient transduction of ACL cells in this manner. Moreover, during a 21-day period GFP⁺ cells were observed more than 6 mm from the severed ligament. This distance is ample for the projected clinical application of this technology. In response to TGF-₁ as the transgene, greater numbers of ACL cells accumulated in the hydrogels, where they deposited larger amounts of type III collagen. These data confirm that it is possible to transduce ACL cells efficiently in situ as they migrate from the ruptured ACL, that transduction does not interfere with the cells' ability to migrate distances necessary for successful repair, and that ACL cells will respond in a suitable manner to the products of the transgenes they express. This permits optimism over a possible clinical use for this technology.