Compiled Review of Dr Wang's Section on Stem Cells

20 Pages

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Ilona Skerjanc

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BIOMACROMOLECULES REVIEWMIDTERMINTRODUCTION TO STEM CELLSWHAT ARE STEM CELLS1 Renew themselves for long periods through cell division selfrenewal2 Give rise to specialized cell types differentiationTYPES OF STEM CELLS Defined by their origin and potentials1 Adult or somatic stem cells tissue specific adult stem cells mesenchymal stem cells2 Pluripotent stem cells embryonic stem cells ES embryonic germ cells EG embryonic carcinoma cells epiblastderived stem cells induced pluripotent stem cells iPSDIFFERENCES BETWEEN ADULT AND EMBRYONIC STEM CELLSEMBRYONIC STEM CELLSSOMATIC STEM CELLS Source of origin derived from blastocyst or primordialSource of origin derived from developing or adult germ cells PGCorganism Proliferation dividing without limit Proliferation restricted replicative potential in vitro Pluripotencydifferentiation pluripotent capacity toPluripotencydifferentiation multipotent make all 3 germ layersdifferentiation not as good in vitro possibility of teratomano fear of in vitro teratoma DEVELOPMENTAL POTENTIALS multipotent cell that can give rise to several types of mature cellsEx blood stem cells pluripotent cell that can give rise to almost all types of adult cellsEx embryonic stem cells totipotent a cell that can give rise to a new individual given appropriate maternal supportEx morula after fertilization of oocyte by sperm the embryo develops into a totipotent cell called a morula The morula then becomes a blastocyst creating two separate layers 1 the inner cell mass which are the cells that will become the embryo and 2 the trophoblast which are the cells that will become the placentaThe inner cell mass is the source of pluripotent embryonic stem cells These pluripotent stem cells can give rise to three germ layers and any kind of tissueNote that cells that can only become one type of tissue are unipotent ADULT STEM CELLS 1 Emerge later in the foetus development2 Serve as a reservoir of continuous replenishment for the tissues in which they reside homeostasis and repair and with tissue heterogeneityDifferent Types of Regeneration PotentialHIGH CELL TURNOVER HIGH REGENERATIVE POTENTIALBlood cellsgut epitheliumepidermismammary epithelium epithelium from mammary glandsvascular epithelium blood vessel liningLOW CELL TURNOVER HIGH REGENERATIVE POTENTIALLiverskeletal musclesmall vasculature blood vesselsadrenal cortexpancreasLOW CELL TURNOVER LOW REGENERATIVE POTENTIALLungsBrainHeartretinakidneyspinal cordMESENCHYMAL STEM CELLS OR STROMAL STEM CELLS Originally MSCs a heterogenous population represent the cells of nonhematopoietic blood forming stromal origin residing in the bone marrow as blood stem cell nicheCurrently MSCs have been isolated from almost all other types Examples of sources peripheralblood amniotic fluid deciduous teeth baby teeth synovial membrane knee umbilical cord blood defined according to three criteria according to the International Society for Cellular Therapy ISCT proposal1 its property of adherence to plastic2 its phenotype CD73 CD105 and more3 its capacity to differentiate into three lineages chondrocytes osteoblasts and adipocyte possibly moreIMPORTANT QUESTIONS ABOUT ADULT STEM CELLS1 how many kinds of adult stem cells exist and in which tissues do they exist2 what are the sources of adult stem cells in the bodyleftover embryonic stem cells or do they arise in another way3 why do they remain in an undifferentiated state when all the cells around them have differentiated4 do adult stem cells normally exhibit transdifferentiation plasticity5 is it possible to expand sufficient adult stem cells in vitro for transplants6 which factors stimulate stem cells to relocate to the sites of injury or damage7 how to reduce immune rejection allograftPLURIPOTENT STEM CELLS1 Embryonic stem cellscome from the inner cell mass of a blastocyst For research uses are often derived from mouse embryo2 Embryonic germ cellsderived from primordial germ cells mouse embryo 105 days3 Embryonic carcinoma cellsderived from testicular teratocarcinoma of mouse 4 Epiblast derived stem cells EpiSCs mouse not orange slidefrom epiblast at 575 days postcoitum or postimplantation from mouse embryoHas pluripotency and distinct gene expression patterns while still consistent with characteristics of hESCsHUMAN EMBRYONIC STEM CELLS1 An immortal embryonic stem cell line is derived from a 56 day blastocyst2 In vitro develop into three germ layers and give rise to almost any type of cellsimilar to in vivo inner cell mass development If injected into immune deficient mouse will form teratomas teratoma is a tumour that demonstrates all 3 germ layers if you do not allow for embryonic stem cells in vivo to attach to plate they will aggregate and form embryoid bodies with give rise to three germ layers
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