Lumbar spine fusion by local gene therapy with a cDNA encoding a novel osteoinductive protein (LMP-1).
METHODS
A posterior arthrodesis animal model using local expression of a newly discovered osteoinductive protein delivered in bone marrow cells.


OBJECTIVE
To introduce the concept of local gene therapy and determine its feasibility for achieving lumbar spine fusion using a gene for a novel osteoinductive protein: LIM Mineralization Protein-1 (LMP-1).


BACKGROUND
Extensive work is currently underway to improve the healing success and morbidity associated with the gold standard bone-grafting material of autogenous iliac crest. As a result, alternative osteoinductive proteins and new delivery methods warrant investigation. The authors' laboratory recently identified a novel gene that had osteoinductive capacity in vitro and is therefore a candidate for a new in vivo osteoinductive agent.


METHODS
Single-level posterior lumbar and thoracic arthrodesis was attempted in 14 athymic rats. The graft material, which consisted of a devitalized bone matrix (no osteoinductive activity) soaked with 0.75 to 1.5 million bone marrow cells, was inserted with the dorsal spine exposed. In each rat, one site received marrow cells transfected with the cDNA encoding a novel osteoinductive protein. At the other site for a control, the marrow cells were transfected with the reverse copy of the cDNA that did not express any protein. Transfection of marrow cells for 2 hours was accomplished using the mammalian expression vector pCMV2. Rats were killed after 4 weeks, and the spines were evaluated by manual palpation, radiographs, and nondecalcified histology.


RESULTS
In the pivotal experiment, successful spine fusion was obtained in 9/9 (100%) of the sites receiving marrow cells transfected with the active LMP-1 cDNA and in 0/9 (0%) of the sites receiving marrow cells transfected with the reverse (inactive) LMP-1 cDNA. Radiographs and histology confirmed the manual palpation results, demonstrating controlled new bone formation in the carrier and marrow transfected with the active LMP-1 cDNA and essentially no bone induction in the sites treated with marrow cells that did not express the protein.


CONCLUSIONS
These data confirm that local delivery of the novel LMP-1 cDNA using bone marrow cells is feasible in vivo. Furthermore, these results demonstrate that posterior thoracic or lumbar spine fusion can be achieved in rats by local delivery of the LMP-1 cDNA.
Boden
S D
SD
Department of Orthopaedic Surgery, Emory University School of Medicine, Atlanta, Georgia, USA.
Titus
L
L
Hair
G
G
Liu
Y
Y
Viggeswarapu
M
M
Nanes
M S
MS
Baranowski
C
C
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D001363:Awards and Prizes; D001854:Bone Marrow Cells / Q000166:cytology; D002352:Carrier Proteins / Q000235:genetics*; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors; D047908:Intracellular Signaling Peptides and Proteins; D060588:LIM Domain Proteins; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D009985:Orthopedics; D011859:Radiography; D051381:Rats; D011923:Rats, Nude; D013123:Spinal Fusion / Q000379:methods*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; D047908:Intracellular Signaling Peptides and Proteins; D060588:LIM Domain Proteins; C484380:PDLIM7 protein, human