Post on 21-Apr-2015
transcript
STEM CELL GENE MANIPULATION AND DELIVERY AS SYSTEMIC THEREPUTICS
P.AnushaM.Pharmacy
119A2S0302
What are stem cellsStem cells are the raw material from
which all of the body’s mature, differentiated cells are made. Stem cells give rise to brain cells, nerve cells, heart cells, pancreatic cells, etc. They have the potential to replace cell tissue that has been damaged or destroyed by severe illnesses.
They can replicate themselves over and over for a very long time.
Two Kinds of Stem CellsEmbryonic (also called “pluripotent”) stem
cells are capable of developing into all the cell types of the body.
Adult stem cells are more difficult to identify, isolate, and purify.
Stem cells based upon their sourceEmbryonic stem cells obtained from the
undifferentiated inner mass cells of a blastocyst, (an embryo that is between 50 to 150 cells)
Umbilical cord blood derived from the blood of the placenta and umbilical cord after birth
Adult stem cells undifferentiated cells found among differentiated cells of a specific tissue and are mostly multipotent cells Bone marrowAdipose tissueCNS stem cellsUmbilical Cord Blood
Embryonic Stem Cells:
Two Sources of Embryonic Stem Cells Excess fertilized eggs from IVF (in-vitro
fertilization) clinics
Therapeutic cloning (somatic cell nuclear transfer)
Stem cell therapy
Stem cell therapy is most often regarded as a means to provide replacement of specific cells for repair of a damaged or failing organ. Therefore, great efforts have been made to identify both ideal sources of cells, and those with the greatest differentiate potential, so that multiple cellular phenotypes can be obtained.
However, recentstudies have provided compelling evidence that, in some diseasestates, engraftment of transplanted stem cells may not, in fact, berequired to gain a therapeutic benefit.
stem cells exert their benefit by selectively seeking out areas of injury/damage within the
body and serving as a reservoir of cytokines and growth factors that promote repair of the endogenous cellular pool within the damaged organs.
These findings suggest that stem cells would be ideally suited as vehicles for delivering therapeutic genes or drugs to damaged/ diseased tissues.
Adult stem cell gene manipulation The prototypic example of adult stem cells, the hematopoietic stem cell. Although they are relatively rare in the human body, these cells can be readily isolated
from bone marrow or after mobilization into peripheral blood. After in vitro manipulation, these cells may be retransplanted into patients by
injection into the bloodstream, where they travel automatically to the place in the bone marrow in which they are functionally active.
Another adult bone marrow-derived stem cell type with potential use as a vehicle for gene transfer is the mesenchymal stem cell, which has the ability to form cartilage, bone, adipose (fat) tissue.
The traditional method to introduce a therapeutic gene into hematopoietic stem cells from bone marrow or peripheral blood involves the use of a vector derived from a certain class of virus, called a retrovirus.
However, these particular retroviral vectors were only capable of transferring the therapeutic gene into actively dividing cells. Since most adult stem cells divide at a relatively slow rate, efficiency was rather low.
Vectors derived from other types of retroviruses (lentiviruses) and adenoviruses have the potential to overcome this limitation, since they also target non-dividing cells.
The major drawback of these methods is “insertional mutagenesis.” and difficult to ex-vivo manipulation.
•
embryonic stem cell gene manipulation
Following derivation, human embryonic stem cells areeasily accessible for controlled and specific geneticmanipulation. When this facility is combined with their rapid growth,
remarkable stability, and ability to mature in vitro into multiple cell types of the body, human embryonic stem cells are attractive potential tools for
gene therapy. First, human embryonic stem cells could be genetically manipulated to introduce the therapeutic gene. This gene may either be active or awaiting later activation, once the modified embryonic stem cell has differentiated into the desired cell type.
The therapeutic gene needs to be introduced into the
cell type used for therapy. Genes may be introduced
into cells by transfection or transduction.Transfection utilizes chemical or physical
methods to introduce new genes into cells.Transduction utilizes viral vectors for DNA
transfer. Viruses, by nature, introduce DNA or RNA into cells very efficiently.
parameter that must be carefully monitored is the random integration into the host genome, since this process can induce mutations or serious gene dysfunction.
However, several copies of the therapeuticgene may also be integrated into the genome, helpingto bypass positional effects and gene silencing. Positional effects are caused by certain areas within thegenome and directly influence the activity of theintroduced gene. Gene silencing refers to the phenomenonwhereby over time, most artificially introducedactive genes are turned off by the host cell, amechanism that is not currently well understood
Gene silencing and positional effects can be avoided by to introduce the gene of interest specifically into a defined region of the genome by the gene targeting technique ( homologous recombination ).
Gene manipulated stem cell deliveryTherapeutic gene
The therapeuticgene is packagedinto a deliveryvehicle such asa retrovirus
and injectedinto the patient
Adult stem cells
embryonic stem cells
Genetically modified ES
Invitro differentiated stem cell
Adult stem cells areisolated and propagatedin the laboratory.
Therapeutic gene
The therapeutic geneis packaged into adelivery vehicle suchas a retrovirus andintroduced into thecells.
The genetically modifiedcells are reintroducedinto the patient
Direct delivery Cell based delivery
Applications of manipulated stem cells for delivery as systemic therapeuticsAny disease in which there is tissue degeneration
can be a potential candidate for stem cell therapies.
Alzheimer’s disease Parkinson’s disease Spinal cord injury Heart disease Severe burns Diabetes
Stem cells for Alzheimer’s disease Stem cells could, however, be genetically
modified so as to deliver substances to the Alzheimer brain, to stop cells from dying and stimulate the function of existing cells.
Manipulated stem cells for Parkinson's disease
Stem cells for diabetes
Drug TestingStem cells could allow scientists to test new drugs using
human cell line which could speed up new drug development.
Only drugs that were safe and had beneficial effects in cell line testing would graduate to whole animal or human testing.
It would allow quicker and safer development of new drugs.
Limbal stem Cell therapy The treatment is known
as limbal stem cell therapy, and the patients who received the treatment suffered from chemical burn or genetic disease know as aniridia
By replacing the limbal stem cells, the cornea begins to clear up as the cells are replaced with the healthy transparent layer again.