الفهرس 
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Abstract
Introduction &Aim of the work
INTRODUCTION
Until the early 1970s DNA was the most difficult cellular molecule for the
biochemist to analyze. Today the situation has changed entirely. It is now
possible to isolate a specific region of a genome, to produce a virtually
unlimited number of copies of it, and to determine the sequence of its
nucleotides. The science of gene therapy is derived from significant research
advances in the fields of genetics, molecular biology, clinical medicine, and
human genomics (Pandey and Mann, 2000)
The recognition of the role of genetic factors in diseases and the enormous
progress in identification of human genetic map made a very rapid progress in
clinical genetics and its utilization for human gene therapy.(Botstein et al.,
1980).
gene therapy can be defmed as the use of any of a collection of approaches for
the treatment of human disease that rely on the transfer of a gene that encodes a
functional protein into a cell or the transfer of an entity that will alter the
expression of an endogenous gene in a cell. (Verma and Somia. 1997)
Two critical steps are required for gene therapy using gene transfer techniques:
(l) the appropriate transfer of gene or genetic material and (2) the continued
gene expression at appropriate levels for therapy. (Thomas, 2001)
Gene transfer is either by direct transfer (in vivo) or laboratory manipulation
(ex vivo) and the transfer vehicles (vectors) are classified into viral and nonviral
methods, with each has its advantages and disadvantages. (Nicolas and
Kenneth ,2002)
viral vectors have been the preferred mechanism for transfer of nucleic acids
into tissues of interest, and they have dominated the field for some time with
their very high efficiency and prolonged expression, however the viral approach
still suffers from limitations including random integration into the host’s
genome, immunogenicity of the vector, and limitations in the insert size. More
importantly, there can be significant toxic side effects such as stimulation of an
immune response, inflammation and neutralizing antibodies associated with
repeat treatment, and other potentially serious toxic outcomes including death.
(Paul et al. , 1998)
Although viral vectors are more efficient than non-viral ones, vectors are not
only judged by their efficiency but also safety, which is actually more importarit
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Introduction & Aim of the work
according to current US FDA clinical trial regulations. Safe delivery includes
the use of low immunogenic components for the vector and specific delivery to
the diseased tissue, with which viral vector is struggling to achieve. Non-viral
vector is superior to viral vector in the safety aspect. In the meantime, the
efficiency of non-viral vector has been improved by different strategies and the
efforts are still ongoing. With these, non-viral vector is surpassing viral vector.
(Shyh-Dar and Leaf., 2007)
Non-viral vectors depend on modulation of genetic material (which is either
plasmids or oligonucleotides) to overcome biological barriers and achieve high
transfection using either physical (electrical, mechanical, and ultrasonic),
chemical (calcium phosphate, cationized liposomes, and cationized polymers)
methods. (Jackson et al. ,2006)
The eye is an attractive target for gene therapy strategies because of its
accessibility and immune-privileged characteristics, that the inflammatory and
immune reactions towards the gene vector and/or transgenic protein will not be
a major drawback. Also due to its relative small size, effective treatment of the
ocular tissues will require minor drug concentrations while the diffusion from
the eye into the circulation is limited due to blood-retinal barrier. ( Bloquel et
at. 2006)
The past few years have witnessed a remarkable increase in the number of
gene therapy studies to treat almost every disease of the eye. All types of
delivery systems, viral and non-viral, have been used. Although numerous
issues remain to be solved, the emerging picture is encouraging. Within the
experimental setting, conditions in the anterior and posterior segments have
been improved by the administration of genes encoding beneficial proteins. In
one case, vision has been restored in a congenitally blind animal. (Teresa
Borras 2003)
The transfer of genetic material into lacrimal epithelial cells and tissues, both
in vitro and in vivo, has been critical for the study of tear secretory mechanisms
and autoimmunity of the lacrimal gland. These studies will help in the
development of therapeutic interventions for autoimmune disorders such as
Sjogren’s syndrome and dry eye syndromes which are associated with lacrimal
dysfunction. These studies are also critical for future endeavors which utilize
the lacrimal gland as a reservoir for the production of therapeutic factors which
can be released in tears, providing treatment for diseases of the cornea and
posterior segment. (Shivaram et at. , 2006)
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Introduction &Aim of the work
Corneal gene therapy initially emerged in 1994 when its potential in
correcting acquired corneal inflammatory diseases was noted. However, most of
the research has focused on modulation, including immunomodulation, of
acquired medical conditions. This is feasible since control of the corneal
microenvironment can be attained by induction or knock-down of proteins
using corneal gene therapy. Corneal gene therapy have showed encouraging
results in Corneal graft survival, Corneal haze treatment, Modulation of wound
healing, Control of corneal neovascularization, and treatment of herpetic
stromal keratitis. (Rajiv et al., 2005)
Experiments for lenticular gene therapy are still in its preliminary phase.
However it has showed to prevent development of secondary cataracts in
experimental animals depending on anti-fibrotic therapy. Also several studies
were done successfully which are the base for future prevention of primary
cataract. (Miyamoto et al. ,2004) (Nami et al. , 2007)
Gene therapy showed great results on experimental animal models of
glaucoma with three different modalties for treatment: enhancement of
trabecular outflow), neuroprotection and Maintenance of filtering bleb of
trbeculectomy (Kazuhisa et al. 2004) (Alan et at , 2006)
Few trials for utilization of gene therapy in management of uveitis have been
made, however they showed impressive results both for endotoxin and
autoimmune enduceuveitis. Also treatment of uveal melanoma by genes
encoding plasminogen activator and angiostatin decreased tumor size and
metastasis in experiments. (Andrawiss et al., 2001) (Wei et al. 2006)
Most research in ocular gene therapy is being applied to retinal diseases with
the most extensively tested retinitis pigmentosa family of diseases because the
phenotypes of these conditions are well characterized in animal models and
many of the genes have been cloned (Christian BameI2006).
However, significant research effort has also been directed toward other
genetic and acquired retinal diseases, including retinal pigment epithelial (RPE)
and metabolic dystrophies, retinoblastoma, proliferative vitreoretinopathy., agerelated
macular degeneration, and choroidal neovascularization with much
impressive results in all of them. (Edward and Mark 2002) (Zarbin et al.
,2007).
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Introduction & Aim of the work
AIM OF THE WORK
The aim of the work is to di~~ ::cent development in gene therapy methods
regarding viral and non-viral ones, and its applications in different ocular
diseases; corneal, uveal, lenticular, retinal diseases and glaucoma.