pCMV–BMP-2–Transfected Cell–Mediated Gene Therapy in Anterior Cruciate Ligament Reconstruction in Rabbits

PurposeThis study investigated the effect of plasmid cytomegalovirus (pCMV)–bone morphogenetic protein 2 (BMP-2) gene therapy on the healing of the tendon-bone interface after anterior cruciate ligament (ACL) reconstruction in rabbits.MethodsThe pCMV–BMP-2 was synthesized from full-length human BMP-2 complementary deoxyribonucleic acid, followed by cloning into pCMV Script vector (Clontech Laboratories, Inc., San Jose, CA), and was delivered by a xenogeneic (rat kidney) cell line. The ACL was reconstructed by the transfer of extensor digital tendon in the proximal tibia. In the study group the pCMV–BMP-2 gene–transfected normal rat kidney cells mixed with calcium alginate gel were placed at the tendon-bone interface, whereas no pCMV–BMP-2 was used in the control group. The evaluations included radiography, bone mineral density, magnetic resonance imaging, biomechanical study, histologic examination, and immunohistochemical analysis.ResultsBone mineral density showed no significant difference between the groups (P > .05). Magnetic resonance imaging showed significantly better contact between tendon and bone in the study group compared with the control group (P < .0001). In the biomechanical study, significantly higher failure load and maximal graft tension were noted in the study group compared with the control group (P = .034). The modes of graft failure were rupture of the tendon proper in 78% and graft pullout from the bone tunnel in 22% of specimens in the study group versus graft rupture in 22% and graft pullout in 78% in the control group (P = .018). On histologic examination, the study group showed significantly better integration between tendon and bone, as well as more bone tissue around the tendon graft, than the control group (P = .0004). On immunohistochemical analysis, the study group showed significantly higher expressions of von Willebrand factor, vascular endothelial growth factor, proliferation cell nuclear antigen, and BMP-2 than the control group (P < .05).ConclusionsThe pCMV–BMP-2 gene therapy significantly improved the healing of tendon to bone and promoted angiogenesis and osteogenesis at the tendon-bone interface after ACL reconstruction in the rabbit model.Clinical RelevanceApplication of pCMV–BMP-2 gene therapy may be an effective adjunct therapy in ACL reconstruction.