GENE THERAPYin Orthopedics

Mechanical stabilization & Biomechanical analysis—Alone !!???

Biology of soft tissue and bone healing needed for good outcome and success.

Eg: RA– dependent on action of growth factors, cytokines antigen presentations and protein interactions

OA– molecular biological, immunological & biochemical aspects play key role

Other disorders– Osteogenesis imperfecta, DMD – today’s treatment – only symptomatic

Genetic defect and biological effect to be understood to provide a curative treatment

Elegant technique Sustained local delivery of therapeutic

growth factors/cytokines using Viral/nonviral delivery vehicles(vectors) Genetic information– cDNA encoding the

protein of interest is inserted into living cell Potential to express the protein

Gene Therapy

Soft tissues Diff capacities to heal foll injuries

Healing by formation of scar– decreased mechanical stress than original tissues

Genes for specific growth factors Introduced into injured tissue

Musculoskeletal system

Directly– injected into tissue & inserts gene into surrounding cells

Indirectly– muscle/skin biopsy- cultured & vector introduced into cells

Viral– transduction Non viral-- transfection

Replication deficient retrovirus Adenovirus Adeno associated virus Herpes virus Lentivirus

Virus

Liposomes DNA-protein conjugates DNA-protein defective virus conjugates

Non viral systems

Therapies that will replace, repair and promote tissue regeneration

# healing involves many regenerative mechanisms.

BMP -- key molecule

Regenerative medicine in Orthopaedics

Impact of #-- Several members of BMP induced & activated

Synth by callus forming cells near # site BMP Network– Noggin Sonic hedgehog(shh) Hepatocyte growth factor(HGF) Vascular Endothelial Growth Factor(VEGF)

BMP

Major driving force for new treatment techniques—

Reduction of recovery time Least invasive

Current modalities—

Use of tissue graft, cell transplantations, artificial scaffolding.

Short half life and inherent instability of proteins

Requires high and multiple doses of proteins

Sustained release of biological agent at therapeutic levels

By transfer of gene encoding the therapeutic agent to the cells of the afflicted tissue or

By implanting cells that have been previously genetically modified

Gene therapy

Accelerated and enhanced Musculoskeletal tissue (Bone, ligament, tendon, cartilage) regeneration

Inhibit disease progression

Result

Bone and soft tissue healing Degenerative(OA,RA,disc) Congenital (OI,DMD,ED) Tumors

GT in Orthopaedic conditions?

Growth factors– BMP Accelerate healing of segmental defects BMP-7-mediated ex vivo gene transfer

based on Mesenchymal Stem Cells may accelerate callus formation in distraction osteogenesis and facilitate consolidation.

Hu J - J Orthop Res - 01-FEB-2007; 25(2): 241-51

Fracture Healing

Delayed administration of adenoviral BMP-2 vector improves the formation of bone in osseous defects

achieve radiological union, repair tissue with enhanced mineralization and greater mechanical strength

Betz OB - Gene Ther - 01-JUL-2007; 14(13): 1039-44

Recombinant BMP-2 used for spinal fusion successfully in clinical trials

Large dose needed for adequate bone repair

Comparison of lentiviral and adenoviral gene therapy for spinal fusion in rats.Miyazaki M - Spine - 1-JUN-2008; 33(13): 1410-7

Reconstructed ACL grafts undergo remodelling; no regeneration

With Gene Therapy Regenerate ACL from tendon graft

Ligament Healing

Use of rhBMP-2 or rhBMP-7 in an injectable calcium phosphate matrix in an intra-articular model of rabbit ACL reconstruction improved tendon-to-bone healing, based on histologic analysis and biomechanical testing.

Clinics in Sports Medicine - Volume 26, Issue 4 (October 2007)  

Adenovirus mediated Gene therapy with BMP-14 and BMP-12 increased tendon tensile strength in a rat model of Achilles tendon injury. –

Bolt P - J Bone Joint Surg Am - 01-JUN-2007; 89(6): 1315-20

Majewski M - Gene Ther - 01-AUG-2008; 15(16): 1139-46

Tendon Healing

Construction of eukaryotic expression plasmid of bFGF gene in rats and its expression in tenocytes.

– increase in expression of type I and III collagen mRNA--repair of tendons and ligaments.

Feng Y - J Huazhong Univ Sci Technolog Med Sci - 01-FEB-2007; 27(1): 27-30

Articular cartilage:

Highly organised Avascular Low healing capacity Degeneration/loss of articular surface—

challenging problem

Cartilage healing

regulatory molecules that augment the reparative activities of the cells, inhibit the cells' degradative activities-- include

insulin-like growth factor I, fibroblast growth factor 2, bone morphogenetic proteins 2, 4, and 7,

and interleukin-1 receptor antagonist.

Gene transfer into articular cartilage and synovial lining cells

protect existing cartilage and build new cartilage.

Gene therapy for articular cartilage repair.Trippel S - Proc Inst Mech Eng [H] - 01-JUL-2007; 221(5): 451-9

Articular chondrocytes are receptive to transduction

AAV vector mediated TGFbeta1-overexpression stimulates cartilage anabolism.

Studies Viral vectors used to transfer genes– IL-

1Ra, IGF-1 and GFAT gene to increase the capacity of joint tissues to synthesize glucosamine.

achieve long-term relief

Osteoarthritis

Amelioration of osteoarthritis by intra-articular hyaluronan synthase 2 gene therapy.

- Zhang DW - Med Hypotheses - 01-JAN-2007; 69(5): 1111-3

Attempts to block

Primary inflammatory mediators-- IL-1 Redirection of primary immune cells like Th-

1 and Th-2 lymphocytes

Rheumatoid Arthritis

new targets for gene therapy in the intervertebral disc–

TGF-beta1, TIMP-1, and LMP-1

Gene therapy for the treatment of degenerative disk disease.Hubert MG - J Am Acad Orthop Surg - 01-JUN-2008; 16(6): 312-9

Degenerative Disc D/s

Nucleus pulposus cellular longevity by telomerase gene therapy. - Chung SA - Spine - 15-MAY-2007; 32(11): 1188-96

Telomerase can extend the cellular lifespan of nucleus pulposus cells

prolong the production of extracellular matrix

The RANKL system therapeutic target in treatment of aseptic

periprosthetic loosening.

gene transfer using an AAV vector has protective effects against orthopaedic wear debris-induced bone loss.

WEAR DEBRIS-INDUCED OSTEOLYSIS:

Adenovirus-mediated transfer of siRNA against Runx2/Cbfa1 inhibits the formation of heterotopic ossification induced by BMP4 (in animal model.)

Lin L - Biochem Biophys Res Commun - 20-OCT-2006; 349(2): 564-72

H O

CONGENITAL mutations in cartilage oligomeric matrix

protein (COMP), (synthesized by chondrocytes)

causes two skeletal dysplasias: multiple epiphyseal dysplasia

(MED/EDM1), pseudoachondroplasia (PSACH), a

dwarfing condition

Detailed knowledge of pathology helpful in future treatment with gene therapy

Expression of mutant cartilage oligomeric matrix protein in human chondrocytes induces the pseudoachondroplasia phenotype.Merritt TM - J Orthop Res - 01-APR-2006; 24(4): 700-7

Lentivirus mediated Heme Oxygenase-1 gene transfer enhances myogenic precursor cell survival after autologous transplantation in pig skeletal muscle.

Laumonier T - Mol Ther - 01-FEB-2008; 16(2): 404-10

DMD & other muscle d/s

gene therapy may achieve induction of tumour necrosis and

increased tumour sensitivity to chemotherapy

Orthopaedic oncology

BMP-2 levels diminished after Perioperative radiation therapy in M/sk sarcoma

Gene therapy to enhance allograft incorporation after host tissue irradiation. - Santoni BG - Clin Orthop Relat Res - 01-AUG-2008; 466(8): 1921-9

Attenuated Salmonella typhimurium with IL-2 gene reduces pulmonary metastases in murine osteosarcoma.

- Sorenson BS - Clin Orthop Relat Res - 01-JUN-2008; 466(6): 1285-91

Pigment epithelium-derived factor overexpression inhibits orthotopic osteosarcoma growth, angiogenesis and metastasis.

Done in rats and humans- promising approach

Ek ET - Cancer Gene Ther - 01-JUL-2007; 14(7): 616-26

Novel cytosine deaminase fusion gene enhances the effect of radiation on breast cancer in bone by reducing tumor burden, osteolysis, and skeletal fracture.

- Goblirsch M - Clin Cancer Res - 15-MAY-2006; 12(10): 3168-76

Limited understanding of

Biochemical properties & Molecular mechanisms of connective

tissue

Gene Therapy- one of the most advanced and exciting concepts

For a better & less invasive treatment options