Gene therapy involves introducing correct genes into patient cells to treat diseases caused by faulty genes. It was first conceptualized in 1972 and the first FDA-approved trial was in 1990. There are two main types - germline therapy modifies heritable germ cells while somatic therapy modifies non-heritable body cells. Common targets for skin gene therapy are keratinocytes, melanocytes and fibroblasts, which can be modified to treat genetic skin disorders, cancers and infections. While promising, gene therapy faces challenges like transient gene expression, immune reactions and safety issues with viral vectors.

1. Gene therapy in dermatology
REFERENCE
1.IADVL
By
Dr Stefi Rani,
DVL PG 1yr

2. ● Gene therapy was first conceptualized in 1972 by
Friedmann. The first U.S. Food and Drug Administration
(FDA)-approved gene therapy experiment was carried out for
ADASCID (Adenosine deaminase deficiency-severe
combined immunodeficiency) in 1990 in the United States.
● It was used in 2006 for the treatment of melanoma and HIV,
and in 2008 for chronic myeloid leukemia. In 2013, its use for
acute lymphocytic leukemia was reported.

3. INTRODUCTION
● A gene is the indivisible, universal unit of information,
hereditary in all living organisms.
● Genes are specific areas of DNA, which encode proteins and
hence become the essential engines of an organism and
human health.
● Replacement of a faulty gene or adding a new gene in an
attempt to cure a disease or improve the body’s ability to fight a
disease is known as gene therapy.

4. ● Different cell types of the epidermis, such as keratinocytes,
melanocytes and fibroblasts, have the potential to be
genetically modified to treat/improve a broad spectrum of
diseases, including genetically inherited skin disorders, tumor
syndromes, metabolic disorders, and infectious diseases.
● Various skin disorders for which gene therapy has been
experimentally carried out with good results include
epidermolysis bullosa (EB), ichthyosis, melanoma, etc.

5. Principles of gene therapy
Gene inhibition
Making diseased cells
more evident to the
immune system
Fixing mutated
genes
Replacing
mutated genes
PRINCIPLES OF GENE THERAPY

6. Replacing a defective gene by introducing a correct gene will help
in re-establishment of the normal function of the body. It can be
done by various methods as follows:
1. Replacing mutated genes: Some cells become diseased
because certain genes work incorrectly or no longer work at all.
Replacing these defective genes may help treat certain diseases.

8. 2. Fixing mutated genes or inactivating mutated genes: Mutated genes
causing disease can be turned off so that they no longer produce a
disease by the help of promoters in the noncoding region. Similarly,
healthy genes which help prevent disease can be turned on so that
they inhibit the disease.
3. Making diseased cells more evident in the immune system:
Sometimes the immune system does not attack diseased cells
because it does not recognize them as intruders.

10. Gene therapy can be used to train the immune system to recognize
the cells that are a threat and get rid of them -Immunotherapy.
4. Gene inhibition: The defective gene can be inhibited by
presenting another gene that either hinders the expression or
interfere with the action of the defective gene.

11. TYPES OF GENE THERAPY
All cells within the physical body contain genes, making them potential
targets for gene therapy.
Gene therapy can be of two types:
1. Germ line therapy : Germ line therapy uses germ cells, such as
sperm or eggs, which are modified by introducing functional genes in their
genome. This results in permanent changes that are passed down to
subsequent generations. The advantage of germ line gene therapy is its
potential for offering a permanent therapeutic effect for all who inherit the
target gene.

12. Drawbacks of germ line therapy
● Germ line therapy is technically more difficult and raises many ethical
challenges.
●It involves a lot of scientific uncertainty, risk, and research on early
embryos.
●It has a higher risk than somatic gene therapy and often leads to
unintentional, irreversible consequences.

13. 2. Somatic gene therapy :
Somatic gene therapy uses therapeutic genes that are transferred
into somatic cells of the patient. It is safer and more conservative
as it affects only the targeted cells in the patient and is not passed
on to future generations. The effects of somatic cell therapy are
thus short-lived.

14. Drawbacks of somatic gene therapy
●The cells of most tissues ultimately die and are replaced by new cells;
repeated treatments over the course of the individual’s life span are thus
required to maintain the therapeutic effect.
● Transporting the gene to the target cells or tissue is at times difficult but
it is easier compared to germ line therapy.

16. VECTOR
● The molecule that carries the therapeutic gene to the target
gene in the cell is named a vector.
● The success of gene therapy depends heavily on proper
selection of the vector.
● Vectors are often viral, nonviral, and hybrid .

18. STRATEGIES FOR GENE DELIVERY
Two approaches for delivering genetic material exist: In vivo and ex vivo.
1. In vivo technique: (Cells are modified inside the body) :
● In vivo gene therapy entails delivery of modified genes directly to the skin
cells inside the patient’s body. Different methods can be used for delivering
the genes, including injection, gene gun, bioplastic particle insertion,
electroporation and by topical application to the skin.
● The advantages of this technique are that costly cultures are not required and
it can be done at medical centers.The disadvantages are that the treatment is
less effective because of low transfection frequency and immune reaction

20. 2. Ex vivo technique: (Cells are modified outside the body and then
transplanted back into the body)
● This type of gene therapy is named ex vivo because it requires
culture of the patient’s cells outside the body. They are transduced in
vitro; then these genetically altered cells are returned to the patient.
● The patient’s cells are harvested, cultivated, and incubated with
vectors carrying a corrective or therapeutic gene within the laboratory.
These cells containing the new genetic information are then
transplanted back to the patient from whom they were derived.

23. METHODS OF GENE DELIVERY
1. Topical method
2. Ultrasound
3. Needle-free syringe
4. Handheld instruments - gene gun
5. Hydrodynamic injections

24. Methods to Enhance Gene Delivery
Physical methods Chemical methods
1. Electroporation 1. Lipoplexes
2. Gene gun 2. Polyplexes
3. Sonoporation 3. Inorganic nanoparticles
4. Magnetofection

25. SIDE EFFECTS OF GENE THERAPY
1. Transient gene expression
2. Unwanted immune reaction
3. Targeting wrong cells
4. Risk of infection by viral vectors
5. Risk of malignancy
6. Not suitable for diseases with multiple etiologies

26. GENE THERAPY IN SKIN
● Genes for about 100 skin disorders have been
identified.Monogenetic skin disorders can be corrected easily as there
is replacement of only one gene.
● With the advent of gene therapy, there is better understanding of the
cellular and molecular biology of human tissues and that of the skin.
● This understanding has raised hopes for the development of
techniques for cure of various inflammatory reactions of the skin,
wound healing, and carcinogenesis.

27. ● The therapeutic gene is delivered by a vector to the patient’s target
cells.
● Target cells for gene therapy in skin diseases Keratinocytes ,
Fibroblasts , Melanocytes ,Macrophages,Hair follicles & Endothelial
cells.
● Keratinocytes: Gene therapy using keratinocytes as target cells can
be used for many skin disorders and systemic diseases.

28. Advantages of use of keratinocytes for gene therapy are the following:
1. Easy accessibility.
2. Ease of administration.
3. Easy monitoring of treated tissues.
4.Targeted gene expression to dividing or nondividing cells.
5. Continuous proliferation of cells throughout life if keratinocyte
stem cells are used.
6. Defined conditions for culture of keratinocytes.
7. Well-characterized biology of epidermis at cellular and molecular levels.

29. 8. Long-term transfection.
9. Vascularization of epidermis
10. Surgical removal of aberrant tissue when required.
11. High levels of gene expression and keratinocyte specificity have
resulted from the use of certain epidermal promoters as vectors.
12. Epidermis and keratinocytes can also be used for application of
liposomal and ballistic gene transfer techniques.
13. Skin is a versatile bioreactor. It can synthesize and secrete proteins
into the systemic circulation.

30. Melanocytes: Transduction capacity and persistence for several
weeks in infected melanocytes were found to be present in
lentivirus.Transduction of melanocytes for a short period can be done
by adenovirus.
Fibroblasts: Fibroblasts are excellent targets for gene therapy for
patients with Epidermolysis bullosa dystrophica. They have many
advantages over keratinocytes.

31. Advantages of use of fibroblasts for gene therapy are the following:
1. Their technical ease of use.
2. The ability of exogenously delivered fibroblasts
to reside where delivered and continuously deliver type VII collagen to the
host’s basement membrane zone, where it incorporates and forms
anchoring fibril structures.
3. More robust cells than keratinocytes.

32. 4. Decreased susceptibility to growth arrest and differentiation than
epidermal progenitors.
5. Ability to be frozen and stored for re-administration, unlike epidermal
sheets, which are fragile and must be immediately used.
6. Purified fibroblasts can be delivered to intact skin via intradermal
injection, eliminating the need for subsequent wound care, which is in
contrast to epidermal cells, which require wounding for successful
engraftment.

33. Stem cells: Holoclone keratinocytes are stem cells in keratinocyte
population. They are considered as the best target cells for gene
therapy. Stem cells provide transgene expression for the entire life
span (more than 150 cell generations).
Hair follicles: The hair follicles, where expression of transduced
genes has been already achieved, are of particular interest for gene
therapy, as it has been discovered that they contain highly pluripotent
stem cells.

34. Gene therapy has been tried for the following dermatological conditions:
1. Mechanobullous disorders—EB (simplex, junctional, and dystrophic
variants)
2. Keratinization disorders—Ichthyosis (X-linked, lamellar, and
epidermolytic hyperkeratosis), Netherton syndrome, Palmoplantar
keratodermas, Pachyonychia congenita types 1 and 2 .
3. Metabolic disorders—Porphyria

35. 4.Malignancies—Melanoma, Squamous cell carcinoma
5. Disorders of gene instability and DNA repair— Xeroderma
pigmentosum (XP)
6. Infectious disorders—human papilloma virus, HIV, Influenza virus,
Human T-cell lymphotropic virus, Herpes simplex virus
7. Others—Basal cell nevus syndrome, eczemas, hair growth, and
wounds.

36. THANK YOU