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Dr. Abdullah Aldahmash Stem Cell – Definition • A cell which has the ability to continuously divide and differentiate into various other kinds of cells/tissues Classifications of stem cells I Potency Description Totipotent 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 II Adult Embryonic (Tissue Specific) Cloned (Somatic Cell Nuclear Transfer) Induced Adult stem cells (Tissue Specific Stem Cell) 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 Embryonic Stem Cell Embryonic human stem cells were first isolated in 1995 by Dr. James Thomson. Source of ESC is Blastocysts (IVF, SCNT) SCNT The aim of this procedure is to obtain stem cells that are genetically matched to the donor organism. Not all of the donor cell's genetic information is transferred, as the donor cell's mitochondria that contain their own mitochondrial DNA are left behind The basis of this technique is cloning animals (such as the famous Dolly, the sheep). The importance of SCNT-based stem cell research has been decreased by the development and improvement of alternative methods of generating stem cells. SCNT iPS It occurs by the introduction of a defined and limited set of transcription factors and culturing these cells under ES cells conditions. A retroviral-mediate introduced to four transcription factor (OCT3/4, SOX2, c-MYC, KLF4) could induce pluripotency. This protocols has been applied to mouse cells and human somatic cells. Nishikawa, S et.al., 2008 iPS Skin cells were taken from the tail tip of a sickle-cell model mouse. The cells were differentiated into hematopoietic cells. The produced cells were transfused back into the sick mouse Hanna J. et.al., 2007 +LIF Self-renewal differenti ation Thomson et al., 1998. Thomson et al., 1998. Secrete unknown factors to the media Characterization of Human ESCs SSEA-4 Sox-2 Sox9 Sox17 Oct-4 Beta-III tubulin Isolate inner cell mass (destroys embryo) Day 5-6 Blastocyst Inner cells (forms fetus) Culture cells “Special sauce” (largely unknown) Beta-cells Neurons Heart muscle Heart repaired The Promise of Stem Cell Technology Replacement of tissues/organs Repair of defective cell types. Study cell differentiation Toxicity testing. Understanding prevention and treatment of birth defects. Study of development and gene control. Study of drugs therapeutic potential. current advances in Stem Cells therapy Tissue engineering Cell based therapy Obstacles of Stem Cell Research How to find the right type of stem cells? How to put the stem cells into the right place? Will the stem cells perform the desired function in the body? Differentiation protocols for many cell types have not been developed.