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STEM CELLS A cell that has the ability to continuously divide and differentiate (develop) into various other kind(s) of cells/tissues. Stem Cell Characteristics: 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) Self renewable: a cell that has the ability to continuously divide Pluripotent: ability to develop into several different kinds of cells/tissues Repair: ability to return function to damaged cells in the living organism Stem cells are unique body cells. • Stem cells have the ability to – divide and renew themselves – remain undifferentiated in form – develop into a variety of specialized cell types Stem cells are classified into three types. Totipotent: growing into any other cell type Pluripotent: growing into any cell type but a totipotent cell Multipotent: growing into cells of a closely related cell family Kinds of stem 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 foetus that will ultimately produce eggs or sperm (gametes). • Adult stem cells: are undifferentiated cells found among specialised or differentiated cells in a tissue or organ after birth. (Or) Stem cells found in adult organisms, for instance in bone marrow, are called adult stem cells. • Based on current research they appear to have a more restricted ability to produce different cell types and to self-renew. •Scientists have recently demonstrated that stem cells, both embryonic and adult, with the right laboratory culture conditions, differentiate into specialized cells. Embryonic stem cells Embryonic Stem Cells (ESC): received from: • Embryos created in vitro fertilization • Aborted embryos Source of ESC: 1. Blastocyst • “ball of cells” • 3-5 day old embryo • Stem cells give rise to multiple specialized cell types that make up the heart, lung, skin, and other tissues 2. Human ESC were only studied since 1998 • It took scientists 20 years to learn how to grow human ESC following studies with mouse ESC • How are embryonic stem cells harvested? • Human ES cells are derived from 4-5 day old blastocyst • Blastocyst structures include: • Trophoblast: outer layer of cells that surrounds the blastocyst & forms the placenta • Blastocoel: (“blastoseel”) the hollow cavity inside the blastocyst that will form body cavity • Inner cell mass: a group of approx. 30 cells at one end of the blastocoel: • Forms 3 germ layers that form all embryonic tissues (endoderm, mesoderm, ectoderm) Stages of Embryogenesis Stages of Embryogenesis Day 1 Fertilized egg 4/16/2014 Day 2 2-cell embryo Day 11-14 Dr. Hariom Yadav Tissue Differentiation Day 3-4 Multi-cell embryo Day 5-6 Blastocyst Blastocyst Diagram Development of specialized cells Adult stem cells • Adult Stem Cells (ASC): can be received from: – Limited tissues (bone marrow, muscle, brain) • Discrete populations of adult stem cells generate replacements for cells that are lost through normal wear and tear, injury or disease – Placental cord – Baby teeth Continued.. • Adult or somatic stem cells have unknown origin in mature tissues – Unlike embryonic stem cells, which are defined by their origin (inner cell mass of the blastocyst) • Adult stem cells typically generate the cell types of the tissue in which they reside – Stem cells that reside in bone marrow give rise to RBC, WBC and platelets – Recent experiments have raised the possibility that stem cells from one tissue can give rise to other cell types • This is known as PLASTICITY • Ex: Blood cells becoming neurons, Liver cells stimulated to produce insulin, Hematopoietic (blood cell producing) stem cells that become heart cells Applications • Basic research – clarification of complex events that occur during human development & understanding molecular basis of cancer • Molecular mechanisms for gene control • Role of signals in gene expression & differentiation of the stem cell • Stem cell theory of cancer • • Biotechnology(drug discovery & development) – stem cells can provide specific cell types to test new drugs – Safety testing of new drugs on differentiated cell lines – Screening of potential drugs • Cancer cell lines are already being used to screen potential antitumor drugs • Availability of pluripotent stem cells would allow drug testing in a wider range of cell types & to reduce animal testing Continued.. • Cell based therapies: – Regenerative therapy to treat Parkinson’s, Alzheimer’s, ALS, spinal cord injury, stroke, severe burns, heart disease, diabetes, osteoarthritis, and rheumatoid arthritis – Stem cells in gene therapy – Stem cells as vehicles after they have been genetically manipulated – Stem cells in therapeutic cloning – Stem cells in cancer • The use of stem cells offers many currently realized and potential benefits. – Stem cells are used to treat leukemia and lymphoma. – Stem cells may cure disease or replace damaged organs. – Stem cells may revolutionize the drug development process.