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2006 yamanakas group in japan determines a method to

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2006- Yamanaka’s group in Japan determines a method to push differentiated fibroblasts backwards in time to make ESC-like cells termed induced pluripotent stem cells -original transcription factors used included Oct4, Sox2, Klf4, and c-Myc Advantages of iPS over ESC Generate disease-specific iPS to study the etiology of disease Generate patient-specific iPS cells as potential therapy (immune matched) Potentially circumvents ethical issues of human ESC research 15
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6 Tissue-specific Stem Cells Resident in tissue Maintain tissue throughout life of an organism Extensive self-renewal Differentiation restricted to the tissue of origin? Germ layer of origin? Generate all cell types in the tissue of origin Slow cycling or quiescent at steady-state Rapidly activated in response to tissue damage 16 Hematopoietic Stem Cells Hematopoietic- blood forming- stem cells Best characterized adult stem cell population Studied since 1960s Utilized clinically to replace blood system of patients with bone marrow disorders Resides in bone marrow Hierarchy of differentiation Prospectively identify by cell surface marker expression Isolate cells by FACS 17 Differentiated cells have high turnover Neutrophils ~12 hours, Red blood cell ~120 days Assays to study tissue stem cells: in vivo transplantation Questions: Is a isolated cell population a multipotent stem cell? Does treatment of a stem cell population enhance or diminish its “stemness” Isolate cell population Label cells to distinguish donor from recipient Transplant labeled cell population into a non- labeled irradiated recipient animal irradiation is used to clear the recipient’s immune system to avoid tissue rejection and to clear the stem cell niche At various time points, isolate peripheral blood from recipient Look for labeled donor cells by flow cytometry Donor Recipient Wait 3 wks to 12 months Donor GFP+ cells 18
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7 19 Scenario 1: Scenario 2: Possible Outcomes: Which Donor Population is an HSC? T cel s B cel s Erythroid Myeloid NK cel s Donor Populations Donor contribution in recipient peripheral blood T cel s B cel s Erythroid Myeloid NK cel s HSC CMP CLP T cel s B cel s Erythroid Myeloid NK cel s 20 Scenario 1: HSC CMP CLP T cel s B cel s Erythroid Myeloid NK cel s Scenario 2: Donor contribution in the entire blood lineage hierarchy 21 Stem Cells reside in specialized niche Niche -supportive environment made up of cells and extracellular material that regulates the fate decisions of a stem cell -cellular signals can be through direct
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2006 Yamanakas group in Japan determines a method to push...

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