Stem Cell Technology

Stem Cell

•         A cell that has the ability to continuously divide and differentiate (develop) into various other kind(s) of cells/tissues

Stages of Embryogenesis

Bone Marrow Stem Cells        

                                                    

Embryonic	Adult Stem Cells
▫         Totipotent ▫            Differentiation into ANY cell type ▫         Known Source ▫         Large numbers can be harvested from embryos ▫         May cause immune rejection ▫         Rejection of ES cells by recipient has not been shown yet	•         Multi or pluripotent ▫         Differentiation into some cell types, limited outcomes •         Unknown source •         Limited numbers, more difficult to isolate •         Less likely to cause immune rejection, since the patient’s own cells can be used

History of Human Stem Cell Research

•         In 1968, the first bone marrow transplant was successfully used in treatment of Severe combined immunodeficiency

•         Since the 1970’s, bone marrow transplants have been used for treatment of immunodeficiencies and leukemias

History of Human Embryonic Cell Research

•         1954 – John Enders received a Nobel prize in Medicine for growing polio virus in human embryonic kidney cells

History of Human Embryonic Stem Cell Research

In 1998, James Thomson (University of Wisconsin-Madison) isolated cells from the inner cell mass of the early embryo, and developed the first human embryonic stem cell lines.

History of Somatic Cell Nuclear Transfer (Cloning)

•         1952 – Briggs and King cloned tadpoles

•         1996 – The first mammal cloned from adult cells was Dolly, the sheep.

History of Cloning

Possible Uses of Stem Cell Technology

•         Replaceable tissues/organs

•         Repair of defective cell types

•         Delivery of genetic therapies

•         Delivery chemotherapeutic agents

Unknowns in Stem Cell/Cloning Research

•         It is uncertain that human embryonic stem cells in vitro can give rise to all the different cell types of the adult body.

•         It is unknown if stem cells cultured in vitro (apart from the embryo) will function as the cells do when they are part of the developing embryo

Challenges to Stem Cell/Cloning Research

•         Stem cells need to be differentiated to the appropriate cell type(s) before they can be used clinically.

•         Recently, abnormalities in chromosome number and structure  were found in three human ESC lines.

•         Stem cell development or proliferation must be controlled once placed into patients.

•         Possibility of rejection of stem cell transplants as foreign tissues is very high.

•         Contamination by viruses, bacteria, fungi, and Mycoplasma possible.

•         The use of mouse “feeder” cells to grow ESC could result in problems due to xenotransplantation (complicating FDA requirements for clinical use).