Characteristics. Capable of dividing and renewing themselves for long periods of time (proliferation and renewal)

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1 STEM CELLS (p 2-8)

2 Overview The body is made up of about 200 different kinds of specialised cells, such as muscle cells, nerve cells, fat cells and skin cells. Cells with the capacity to give rise to the whole organism are called as stem cell. All cells in the body come from stem cells. They represent all different ways that human genes are expressed as proteins Researchers first extract stem cells from human embryos.

3 Characteristics Stem cells can be called as Blank cells (unspecialized) Capable of dividing and renewing themselves for long periods of time (proliferation and renewal) Have the potential to give rise to specialized cell types(differentiation) Have the capability to return function to the damaged cells in the living organisms.

4 Embryonic Stem and Germ Cells Embryonic stem cells come from a five to six-day-old embryo. They have the ability to form virtually any type of cell found in the human body. Embryonic germ cells are derived from the part of a human embryo or fetus that will ultimately produce eggs or sperm (gametes). Unipotency is a cell s capacity to give rise to only one cell type.

5 Often known as adult stem cells. Tissue Stem Cells Also includes stem cells isolated from fetal and cord blood. Reside in most tissues of the body where they are involved in repair and replacement. Already being used to treat patients (hematological malignancies, diseases of the immune system). Bone marrow Kidney Lung

6 Multipotent Stem Cells

7 Stem Cell Commitment Stem cells give rise to intermediate progenitor cells- transit amplifying cells. They produce differentiated population of cells. For example hematopoietic stem cells, they are multipotent but get commitment into a particular pathway in a stepwise process.

8 cells. Stem Cell Commitment The multipotent cells give rise to different commited progenitors which undergo many rounds of cell division to produce a population of cells of a given specialized type. In particular HSCs (Haemopoeitic/blood stem cells)give rise to one type that is capable of generating lymphoid cells and another type that results in generation of myeloid

9 Stem Cell Renewal Stem cells follow a mechanism to maintain their population while also generating differentiated populations- asymmetric cell division. They have the capacity to produce one cell similar to itself (i.e. continue being a stem cell) and also generate another cell that can proceed on a different pathway and differentiate. Several mechanisms exist within stem cells that determine asymmetric cell division like cell polarity. The microenvironment that controls the self-renewal and maintenance of stem cells- stem cell niche. It saves stem cells from depletion, while protecting the host from overproduction of stem cells.

10 Stem Cell Technology Pluripotent stem cells offer the possibility of a renewable source of replacement cells and tissues to treat a number of diseases and conditions.

11 Stem Cell Diseases It is possible that stem cells abnormality can be the basis for several diseases. Metaplasia is a switch that occurs in tissue differentiation which results in conversion of one type of cell to another type (not as a cell which is part of that tissue). It is often seen in lung cancers- pulmonary fibrosis. This represents a change that might be brought about by stem cells of that tissue rather than its mature cells. Also in many cancers especially of continuously renewing tissues, such as blood or skin, are in fact diseases of stem cells, because it is only the stem cells of blood or skin that stay for a sufficient length of time to accumulate the required number of genetic changes for malignant (cancerous) transformation.

12 Unknowns in Stem Cell 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.