Gene Therapy in Vascular Surgery

1
Gene Therapy in Vascular Surgery

• Saint Barnabas Medical Center
• Frank Nami, M.D.

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What is gene therapy?

• DNA
• RNA
• Proteins

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What is the goal of gene therapy?

• Provide functional proteins
• Introduce recombinant DNA into a host
  cell/tissue, which initiates or accentuates
  expression of a protein that may alter the
  effects of a disease

4
Issues in gene therapy

• What is the best gene to treat each disease?
• Which cells should be targeted for gene transfer?
• How much gene transfer efficiency is required?
• Are current vectors feasible for clinical
  application?

5
Target diseases of gene therapy in vascular
surgery

• Graft proliferative disease
• Anastamotic stenosis (artificial graft, vein
  graft)
• Valve stenosis (vein graft)
• Critical limb ischemia
• Hypercholesterolemia
• Aneurysms

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Proliferative disease

• Cytotoxic gene therapy strategy can limit the
  proliferative response in balloon-injured porcine
  iliac artery and rat carotid artery by 86 and
  46 respectively

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Proliferative disease

• Cytostatic therapy
• Antisense oligonucleotides to cell-cycle
  regulators c-myb, c-myc, proliferating cell
  nuclear antigen (PCNA) and cdk2 possible
  effective targets for restenosis.
• Cylin inhibitors
• p21, p27, and tumor suppressor gene p53

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Therapeutic angiogenesis

• Gene therapy to achieve therapeutic angiogenesis
  is ideally simple the administration of genes
  encoding angiogenic growth factors.

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Therapeutic angiogenesis

• Poor runoff is a critical factor for enhancing
  graft proliferative disease.
• Therapeutic angiogenesis may improve the blood
  flow profile by increasing the vascular bed in
  the peripheral muscles and may thereby attenuate
  graft proliferative disease.

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Therapeutic angiogenesis

• Proteolytic degeneration of the basement membrane
  of a blood vessel wall and surround extracellular
  matrix.
• Migration of endothelial cells and pericytes into
  region of ischemia.
• Cells proliferate, new matrix proteins, form
  capillary networks.

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Therapeutic angiogenesis

• VEGF (Vascular Endothelial Growth Factor)
• FGF (Fibroblast Growth Factor)

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Therapeutic angiogenesis VEGF

• 100-2,000 mg of naked DNA encoding VEGF given
  intraarterially via catheter
• No significant improvement at lower doses
• But, 3 of 5 patients receiving 1,000 mg dose had
  improvement of blood flow on digital subtraction
  angiography

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Therapeutic angiogenesis VEGF

• IM VEGF injection in 9 patients with critical
  limb ischemia
• Successful gene expression documented by an
  increase in serum VEGF levels
• Average ABI at 2 weeks improved from 0.33 to 0.48
  (p0.02)

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Therapeutic angiogenesis VEGF

• Contrast angiography noted new collateral vessels
  in 7 limbs
• MRI revealed improved distal flow in 8 limbs
• Ischemic ulcers improved in 4 of 7 limbs
• 3 patients subsequently required below-knee
  amputation

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Therapeutic angiogenesis FGF

• FGF given intraarterially day 1 and day 30.
• Changes in claudication onset time and ABI not
  significant.
• Other endpoints such as walking distance and
  walking speed unchanged.

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Therapeutic angiogenesis FGF

• Intramuscularly given FGF in thigh and calf
• Significant decrease in rest pain noted.
• ABI also noted to be increased substantially.

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Retroviral vectors

• Two copies of single stranded RNA genome
• RNA converted into a double stranded DNA using
  reverse transcriptase
• Attractive vectors for gene transfer
• Target cells replicating, concern for insertional
  mutagenesis

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Adenoviral vectors

• Non-enveloped double-stranded DNA virus
• Early phase genes, late phase genes.

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Plasmid based vectors

• Direct gene transfer without a virus carrier.
• Lack of toxicity, ease of preparation, and
  administration.

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DNA liposome complexes

• Closed vesicles, internal aqueous membrane
  separated from the external medium by a bilayer
  lipid membrane.
• Undergo degradation after delivery.