Dr. Abdullah AldahmashDr. Abdullah Aldahmash

Stem CellCell – Definition

• A cell which has the ability to continuously divide and differentiate into various other kinds of cells/tissues

Potency DescriptionTotipotent 1-3 days, differentiate into

embryonic and extraembryonic cell types

Pluripotent Descendants of totipotent cells and differentiate into cells of 3

germ layers

Multipotent Produce cells of a closely related family of cell (e.g. hematopoietic

stem cells

Oligopotent Differentiate into ONLY a few cells, such as lymphoid or myeloid

stem cells

Unipotent Produce ONLY one cell type (e.g. muscle stem cells)

Nullpotent The terminal cell

Classifications of stem cells IClassifications of stem cells I

Found in specific mature body tissues as well as the umbilical cord and placenta after birth.They also can be isolated of developing embryos’ different tissues

Adult stem cellsAdult stem cells ((Tissue Specific StemTissue Specific Stem Cell)Cell)

Embryonic Stem Embryonic Stem CellCell

Embryonic human stem Embryonic human stem cells were first isolated in cells were first isolated in 1995 by Dr. James 1995 by Dr. James Thomson.Thomson.Source of ESC is Source of ESC is Blastocysts (IVF, SCNT)Blastocysts (IVF, SCNT)

SCNTSCNT

The aim of this procedure is to obtain stem cells The aim of this procedure is to obtain stem cells that are genetically matched to the donor organism.that are genetically matched to the donor organism.Not all of the donor cell's genetic information is Not all of the donor cell's genetic information is transferred, as the donor cell's mitochondria that transferred, as the donor cell's mitochondria that contain their own mitochondrial DNA are left behind contain their own mitochondrial DNA are left behind The basis of this technique is cloning animals The basis of this technique is cloning animals (such as the famous Dolly, the sheep). (such as the famous Dolly, the sheep). The importance of SCNT-based stem cell The importance of SCNT-based stem cell research has been decreased by the development research has been decreased by the development and improvement of alternative methods of and improvement of alternative methods of generating stem cells. generating stem cells.

SCNTSCNT

iPSiPS

It occurs by the introduction of a It occurs by the introduction of a defined and limited set of defined and limited set of transcription factors and culturing transcription factors and culturing these cells under ES cells these cells under ES cells conditions.conditions.A retroviral-mediate introduced to A retroviral-mediate introduced to four transcription factor (OCT3/4, four transcription factor (OCT3/4, SOX2, c-MYC, KLF4) could SOX2, c-MYC, KLF4) could induce pluripotency.induce pluripotency.This protocols has been applied This protocols has been applied to mouse cells and human to mouse cells and human somatic cells.somatic cells.

Nishikawa, S et.al., 2008

iPSiPS

Skin cells were Skin cells were taken from the tail taken from the tail tip of a sickle-cell tip of a sickle-cell model mouse.model mouse.The cells were The cells were differentiated into differentiated into hematopoietic cells.hematopoietic cells.The produced cells The produced cells were transfused were transfused back into the sick back into the sick mouse mouse

Hanna J. et.al., 2007

+LIF

Self-renewalSelf-renewal differentdifferentiationiation

Thomson et al., 1998.

Thomson et al., 1998.

Secrete unknown factors to the media

Characterization of Human Characterization of Human ESCsESCs

Sox17

Sox9 Beta-III tubulin

SSEA-4 Sox-2 Oct-4

Isolate inner cell mass(destroys embryo)

Heart muscleNeurons

Beta-cells

“Special sauce”(largely unknown)

Day 5-6Blastocyst

Inner cells(forms fetus)

Outer cells

(forms placenta)

Heartrepaired

Culture cells

The Promise of Stem Cell The Promise of Stem Cell TechnologyTechnology

Replacement of tissues/organsReplacement of tissues/organsRepair of defective cell types.Repair of defective cell types.Study cell differentiationStudy cell differentiationToxicity testing.Toxicity testing.Understanding prevention and Understanding prevention and treatment of birth defects.treatment of birth defects.Study of development and Study of development and gene control.gene control.Study of drugs therapeutic Study of drugs therapeutic potential.potential.

current advances in Stem current advances in Stem Cells therapy Cells therapy

Cell based therapy

Tissue engineering

Obstacles of Stem Cell ResearchObstacles of Stem Cell Research

How to find the right type of stem cells? How to find the right type of stem cells?

How to put the stem cells into the right place?How to put the stem cells into the right place?

Will the stem cells perform the desired function in Will the stem cells perform the desired function in the body?the body?

Differentiation protocols for many cell types have Differentiation protocols for many cell types have not been developed.not been developed.