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Madiha Khalid
07-arid-1610
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Use of DNA as a pharmaceutical agent to treat disease.
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The most common form involves DNA that encodes a
functional, therapeutic gene to replace a mutated gene.
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Other forms involve using DNA that encodes a
therapeutic protein drug.
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Once inside, the DNA becomes expressed by the cell
machinery, resulting in the production of therapeutic
protein, which in turn treats the patient's disease.
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A vector delivers a therapeutic gene into patient’s target
cell.
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Functional proteins are created from therapeutic gene
causing cells to return to a normal state.
Gene therapy may be classified into the two following
types
 Somatic gene therapy
In somatic gene therapy, the therapeutic genes are
transferred into the somatic cells (non sex-cells), or body, of
a patient.
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Germ line gene therapy
In germ line gene therapy, germ cells(sperm or
eggs), are modified by the introduction of functional genes,
which are integrated into their genomes.
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Ex vivo: where cells are modified outside the body and
then transplanted again.
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Cardiovascular disease remains the leading cause of
morbidity and mortality in developed countries.
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The emergence of human gene therapy in the early
1990s led to numerous attempts, both experimental and
clinical, to treat cardiovascular disease with gene
therapy strategies.
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Gene therapy holds considerable promise for the
treatment of cardiovascular disease and may provide
novel therapeutic solutions for both genetic disorders
and acquired pathophysiologies such as arteriosclerosis
and heart failure
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Recombinant DNA technology and the sequencing of
the human genome have made candidate therapeutic
genes available for cardiovascular diseases.
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However, progress in the field of gene therapy for
cardiovascular disease has been modest.
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one of the key reasons is the lack of gene
delivery systems for localizing gene therapy to specific
sites to optimize transgene expression and efficacy.
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Because cardiovascular disease is characteristically
localized, the site-specific targeting of gene therapy for
the cardiovascular system is necessary.
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For efficient delivery of therapeutic genes to the
cardiovascular system, a series of barriers have to be
overcome.
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The gene vectors need to pass through the endothelial
barriers in capillary walls when systemically injected.
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Plasmid faces a threat of being degraded rapidly by the
immune system or DNAse in serum before transfection.
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Viral gene vectors need to avoid the immunoreaction in
circulation and transduction of non-target organs, mainly
liver and spleen.
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The plasmid needs to avoid being entrapped into
lysosome or the endosome, where it will be degraded.
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The gene vector has to penetrate the nuclear
membrane to achieve the goal of gene therapy.
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A variety of cardiovascular therapeutic gene constructs
have been studied in vitro and in vivo.
These constructs can be categorized into several
groups
The tumor-suppressor p53
Metalloprotease inhibitor 3
hepatocyte growth factor
superoxide dismutase [SOD]
sarcoplasmic/endoplasmic reticulum calcium ATPase 2
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Mostly 2 types of vectors are used
Non-viral gene vectors
Plasmid DNA
Antisense and decoy RNA
Viral gene verctors
Retroviruses and lentiviruses
Adenoviruses
Adeno-associated viruses
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Low toxicity,
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Considered to be the safest choice for therapeutic gene
transfer
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Unfortunately, the inherently low expression
limited clinical situations in which low and transient
expression of the transgene is required.
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Ongoing efforts to optimize the plasmid backbone via:
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tissue-specific enhancers
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prevent premature silencing
It increase and stabilize the levels of transgene
expression obtainable with non-viral vectors.
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Inactivates gene involved in disease process
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Antisense specific to target gene disrupts the translation
of faulty gene
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Aqueous compartments enclose by membrane
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Protect DNA from undesirable degradation during
transfection
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Plasmid can be covered with lipids to form micelles or
liposomes
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Low efficiency due to lack of ability in term of ‘
endosomal escape.
Can infect more than one type of cell
 New gene can be inserted into wrong position in the cell
 DNA can unintentionally be inserted into patient’s
reproductive system and resultant changes will pass to
next generation
 Transferred gene can be over expressed
 Protein in excess will be harmful
 Could cause an immune reaction
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The main purpose is:
To provide the method of transport to deliver the
formulation containing the gene vector to the intended
site of action.
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Minimizing the contact between the gene vector and
bodily fluids prior to arrival at the intended location
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Reducing this contact decreases the dilution of the
vector and protects the surface of the vector from nonspecific interactions that are typically detrimental to its
activity.
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The most straightforward approach to myocardial gene
delivery is the direct needle injection of the vector
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However, this approach has low efficiency; transduced
cells are typically observed only along the needle track
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But transgene expression is usually low because of the
rapid removal of the vector, which is intensified by the
local inflammatory reaction initiated by needle-related
tissue damage
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Coronary artery catheterization is:
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Minimally invasive and well-established procedure that
allows homogenous gene delivery to each territory of
the heart
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The major advantages of this approach are that it is
minimally invasive and relatively safe
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Thus, it is especially attractive for patients with endstage heart failure.
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Simplest and less invasive method
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Among current available methods of cardiac gene
delivery
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In rodents, injection into the tail vein results in
successful cardiac gene expression
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Dilution by the systemic blood circulation compromises
the vector concentration in the cardiac circulation,
uptake by other organs such as liver, lung, and spleen
before the vectors reach the heart is another issue
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UTMD is an immense potential target-specific gene
delivery tool.
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Microbubbles (MBs) of UTMD, which may consist of
lipids, albumin, saccharide, biocompatible polymers and
other materials are traditionally used as ultrasound
contrast agents due to their physical property of
reflecting ultrasound.
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Microbubble as cavitation nucleus could expand and
contract under the effect of ultrasound, and disrupted
when the acoustic pressure reaches a much higher
level.
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The mechanism is based on the specific response of
the microbubbles upon exposure to ultrasound,namely
sonoporation.
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Microbubbles may oscillate when exposed to
ultrasound, and then these oscillating microbubbles
may rupture. So, the gene therapy vector incorporated
with microbubbles can be released with high local
concentrations at the site of interest.
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Meanwhile, the destruction of MBs may transiently
induce transient holes in membranes and cause entry of
gene into target cells.
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Low toxicity
Low immunogenicity
Low invasiveness
MB can be intravenously injected
Great potential for repetitive application
Organs can be targeted with high specificity
Improve the efficiency
Regarded as a new choice for gene therapy
UTMD constitutes the most efficient method to deliver
transgene up till now.
Translation of gene therapies into routine medical practice
will require the development and optimization of novel
delivery systems capable control of gene vector
biodistribution and activity.
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Zhi-Yi Chen1, Yan Lin1, Feng Yang1, Lan Jiang1 and Shu ping
Ge2Gene therapy for cardiovascular disease mediated by
ultrasound and microbubbles, Chen et al. Cardiovascular
Ultrasound 2013, 11:11.
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Lisa Tilemann, Kiyotake Ishikawa, Thomas Weber, and Roger J.
Hajjar, Gene Therapy for Heart Failure, Circ Res. 2012 March 2;
110(5): 777–793.
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Julie A. Wolfram, PhD; J. Kevin Donahue, MD, Gene Therapy to
Treat Cardiovascular Disease
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Elizabeth G. Nabel MD,Gene Therapy for Cardiovascular
Disease,2013
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Ilia Fishbein, Michael Chorny, and Robert J Levy,Site-specific gene
therapy for cardiovascular disease,March 2010