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STEM CELLS

STEM CELLS. A Novel Tool for the Regeneration of Damaged Organs. Advances in Stem Cell Technology. Lecture-1 (INTRODUCTION) Date: 17/10/16. Muhammad Tariq Awan - PhD 1 Department of Biotechnology, MUST, Mirpur Corresponding: stemcellbiologist@gmail.com. WHAT ARE STEM CELLS?.

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STEM CELLS

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  1. STEM CELLS A Novel Tool for the Regeneration of Damaged Organs Advances in Stem Cell Technology Lecture-1(INTRODUCTION) Date: 17/10/16 Muhammad Tariq Awan - PhD 1Department of Biotechnology, MUST, Mirpur Corresponding: stemcellbiologist@gmail.com

  2. WHAT ARE STEM CELLS? Stem Cells are un-differentiated cells and thus retain the ability to become some or all of the more than 200 different cell types in the body for the life time of the organism and thereby play a critical role in repairing organs and body tissues throughout life.

  3. PROPERTIES OF STEM CELLS STEM CELLS possess three main properties 1. Unspecialization 2. Self-renewal 3. Differentiation • 1. Stem Cells are unspecialized • They do not have any tissue-specific structures that allow for specialized function • Stem cells cannot work with its neighbors • 2. Stem cells can renew themselves for long periods • This is unlike muscle, blood or nerve cells • In the lab, a starting population of SCs that proliferate for many months yields millions of cells that continue to be unspecialized. • 3. Differentiation • Unspecialized stem cells give rise to specialized cells in response to external and internal chemical signals

  4. PROPERTIES OF STEM CELLS Self-Renewal Self-Renewal Differentiation Unspecialization

  5. POTENTIAL OF STEM CELLS (POTENCY) Stem cells have the capacity to differentiate into different specialized cell types

  6. Symmetric cell division At the beginning of embryonic development, stem cells undergo symmetric cell division. They divide symmetrically, where one cell splits and gives rise to two identical cells by Mitosis that have the same potential. This is why we said the stem cells in the early embryo remain the same and are identical.

  7. Asymmetric cell division When stem cells give rise to two cells that are different from each other. One of the cells remains a stem cell and the other changes into a progenitor cell. At blastocyst formation and gastrulation the stem cells start to divide asymmetrically. Progenitor cell is a young cell that will change into a mature cell type, like the epithelial cell in green. • Self-renews • Differentiates Progenitor cell Stem cell Stem cell

  8. Stem cell divide to produce a green progenitor cell which differentiates into a green skin cell. That stem cell can divide again,this time producing a different type of progenitor cell which matures into yet another cell type,like this brain cell. DIFFERENTIATION DIFFERENTIATION  SELF – RENEWAL 

  9. Totipotent This cell Can form the Embryo and placenta Pluripotent This cell Can form the Embryo Multi- potent Fully mature

  10. Totipotent: • Total potential to form any adult cell type or specialized tissue needed for embryonic development. • These stem cells can differentiate into embryonic and extraembryonic cell types. Such cells can construct a complete, viable organism. • These cells are produced from the fusion of an egg and sperm cell. Cells produced by the first few divisions of the fertilized egg are also totipotent. • Pluripotent: • Pluripotent stem cells are the descendants of totipotent cells and can differentiate into nearly all cells, i.e. cells derived from any of the three germ layers • Form most or all 210 • differentiated adult cell types

  11. Multipotent: • Multipotent stem cells can differentiate into a number of cells, but only those of a closely related family of cells. • Limited potential • Forms only multiple adult cell types • Oligodendrocytes • Neurons • Oligopotent stem cells can differentiate into only a few cells, such as lymphoid or myeloid stem cells. • Unipotent cells can produce only one cell type, their own, but have the property of self-renewal, which • distinguishes them from • non-stem cells • (e.g. progenitor cells, • muscle stem cells)

  12. TYPES OF STEM CELLS Embryonic Stem Cells (ESCs) • Embryonic stem cells (ESCs) are derived from the inner cell mass of the blastocyst, a structure that appears during early phase of embryonic development at day 6 in humans. • The main properties of these cells include a robust capacity for self-renewal and the potential to differentiate into specific cell lineages. • A human embryonic stem cell is also defined by the expression of several transcription factors and cell surface proteins. • The transcription factors Oct-4, Nanog, and  Sox2 form the core regulatory network that ensures the suppression of genes that lead to differentiation and the maintenance of pluripotency

  13. Adult Stem Cells (ASCs) • Adult stem cells are undifferentiated cells present in all organs of the developed organism with the ability to divide and gave another cell like itself and also a cell more differentiated than itself. • Pluripotent adult stem cells are rare and generally small in number but can be found in a number of tissues including umbilical cord blood. • Bone marrow has been found to be one of the rich sources of adult stem cells which have been used in treating several conditions including Spinal cord injury, Liver Cirrhosis, Chronic Limb Ischemia and Endstage heart failure. • A great deal of adult stem cell research to date has had the aim of characterizing the capacity of the cells to divide or self-renew indefinitely and their differentiation potential

  14. Hematopoietic Stem Cells (HSCs) • The hematopoietic stem cells are cells that give rise to all red and white blood cells and platelets. • These cells are negative for lineages markers and express the markers CD45, CD34, CD133 and CD117. • HSCs are multipotent stem cells • Mesenchymal Stem Cells (MSCs) • MSCs can be defined by a combination of phenotypic markers and functional properties. • MSCs express Stro-1, CD105 (SH2), CD72 and CD73 (SH3/4) as well as some cell adhesion molecules. • MSCs lack the expression of typical hematopoietic antigens CD45, CD34 and CD14. • Tissue Committed Stem Cells (TCSCs) • TCSCs represent cells that are committed to a particular organ or tissue (e.g. skeletal muscles, liver, neural tissue, myocardium, endocrine pancreas). • TCSCs are CXCR4+, CD34+, AC133+, CD45− and Sca-1+, lin−, CD45− .

  15. MESENCHYMAL STEM CELLS • Morphology • Small cell body with a few cell processes • Large and round nucleus with a prominent nucleolus • Detection • Surface antigens • Differentiation capacity • Multipotent- Can differentiate into • Osteoblasts • Adipocytes • chondrocytes • myocytes • neuron-like cells.

  16. MESENCHYMAL STEM CELLS • SOURCES • Bone Marrow • Peripheral Blood • Cord Blood • Adipose • Limbus • Many adult tissues

  17. How do MSCs Attach to Vessels?

  18. Induced Pluripotent Stem (iPS) CellsGenetically engineering new stem cells Skin cells iPS cells There is another type of stem cell. One way to obtain pluripotent stem cells without destroying an embryo would be to just make them, simply engineer them…. This is like turning back the clock in a subset of cells to create pluripotency, rather than directly harvesting or cloning embryonic stem cells. In induced Pluripotent Stem Cell technology, you FIRST isolate and culture skin (mature) cells from a patient. SECOND, you introduce three or four pluripotency genes into the skin cells by using an engineered virus carrier. THE EXPRESSION OF THESE GENES REGENERATES THE STEM CELL PHENOTYPE. Here, the red cells indicate the cells actively expressing the four essential, stem cell or pluripotency, genes. In the THIRD image, you harvest and culture the cells according to the method for embryonic stem cell culture. FINALLY, through this process, a subset of the cells generates embryonic-stem-cell-like colonies called induced Pluripotent Stem cells.

  19. Induced Pluripotent Stem (iPS) Cells • Adult cells can be reprogrammed back to an embryonic state by over-expressing powerful stem cell genes. These cells known as induced pluripotent stem (iPS). • iPS cells are not derived from live embryos and can be generated from any patient thus removing both the ethical and immunological issues at the same time. • These are not adult stem cells, but rather adult cells (e.g. epithelial cells) reprogrammed to give rise to pluripotent capabilities. Using genetic reprogramming with protein transcription factors, iPS cells equivalent to ESCs have been derived from human adult skin tissue.  • Shinya Yamanaka and his colleagues at Kyoto University used the transcription factors Oct3/4, Sox2, c-Myc, and Klf4 in their experiments on cells from human faces. 

  20. Stem Cells: A Brief History 1896 /1909 Term “Stem Cell” used 1960s Stem Cell discoveries BM contains HSCs & MSCs 1981 ESCs derived from ICM in Mice 1990s Nerve cells differentiated in vitro 1992 ESCs derived from non human Primate 1998 ESCs derived from Human

  21. Stem Cell History 1998 - Researchers first extract stem cells from human embryos 1999 - First Successful human transplant of insulin-making cells from cadavers 2001 - President Bush restricts federal funding for embryonic stem-cell research 2002 - Juvenile Diabetes Research Foundation International creates $20 million fund-raising effort to support stem-cell research 2002 - California ok stem cell research 2004 - Harvard researchers grow stem cells from embryos using private funding 2004 - Ballot measure for $3 Billion bond for stem cells 2007 iPS discovered

  22. Importance of Stem Cell Research

  23. “It is an ocean full of pearls and we need to search these pearls only for our benefit”.

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