S104: Stem Cells and Disease!Main Ideas - Stem cells likely to be imp. component of future of regenerative medicine, even more likely due to dev. of iPSCs!- Some cancers be largely be due to dev. of a pool of cancer stem cells from normal adult stem cells!- Understanding CSCs key to dev. therapeutic strategies that prevent cancer recurrence!!Learning Objectives!1) Discuss the current and potential roles of stem cells therapy in regenerative medicine. 2) Describe the generation of induced pluripotent stem cells (iPSCs), incl. advantages/disadvantages 3) Discuss cancer stem cells (CSCs), incl. the implications for effective chemotherapy 1) Discuss the current and potential roles of stem cells therapy in regenerative medicine. - Stem cell therapy has great potential for improving human health - ability to gen. all cell types in body --> possibility for cell-based therapy for many conditions!- repair of degenerating or lost tissues (ex. Parkinson's, spinal injuries, MI's)!- gene therapy for diseases (ex. muscular dystrophy)!- Hematopoietic Stem Cell (HSC) Therapies have become standard clinical care - BMT has been used to treat leukemias since 1960, rich pop'n of hematopoietic stem cells!- allogenic transplant= between 2 people who aren't identical twins!- Autologous (patient's own cells) hematopoetic stem cell transplantation has significantly reduced immune reactivity and mortality!- Umbilical cord has a high # of multipotent stem cells, less prone to rejection and graft vs. host!- Peripheral blood SC use becoming more common than BMT because less invasive for donor!- Successfull because: easy to obtain and deliver HSCs, intrinsic potential to migrate to their native stem cell niches, inherent potential to differentiate into specific cells and migrate into circulation, no need to restore integrity/function of a more complex organ!- HSC transplantation is being used experimentally for other diseases!- Ex. epidermolysis bullosa!- curing sickle cell disease, 90% cure rate, but 5% mortality rate!- new gentler method: lower radiation, immune suppression, antibody that kills off WBCs in donor and recipient!- Selling of Stem Cells!- National Organ Transplant Act (1984): illegal to sell body parts incl. bone marrow!- doesn't apply to blood stem cells obtained by apheresis because this tech. wasn't used till after 1984!- Why not allow sale? Humans --> commodities, poor would be pressured..etc!- People and patients can buy and sell peripheral stem blood cells derived from apheresis, which is used in 2/3 of bone marrow transplants! 2) Describe the generation of induced pluripotent stem cells (iPSCs), incl. advantages/disadvantages - 3 difficult problems assoc. w/stem cell therapy!- ethical concerns!- rejection of transplanted cells or regenerated organs!- generation of enough cells or tissue in a reasonable time frame !- Reprogramming of cells to circumvent the major restrictions on the use of ESCs and multipotent stem cells!- SCNT: somatic cell nuclear transfer (therapeutic and reproductive cloning)!- iPSCs: induced pluripotent stem cells. De-diff of a somatic cell to a pluripotent state followed by induction into a different differentiated cell!- Transdifferentiation: convesion of 1 terminally differentiated cell type into another w/o de-diff. to an immature phenotype. Must rule out cell fusion/other explanations.!- Goals of reprogamming!- models of human disease!- isogenic cells for replacement therapy!- Induced pluripotent stem cells = most promising new type of stem cell therapy!- Pluripotent stem cells (iPSCs=iPSs= PSCs) can be made from differentiated cells by forcing expression of certain txn factors!- 1st done in mammals in 2006, 4 txn factors + mouse fibroblast --> cell identical to ES cell!- Txn factors= Oct4, Sox2, Myc, Klf4 (gene addition to fibroblasts) !- reprogrammed a differentiated cell into a pluripotent cell!- iPSCs can be induced by inserting the correct genes, all of the above txn factors were doinng diff things that allowed the cell to have a high txn rate, w/o differentiating, and survive apoptosis!- Testing for pluripotency!- when aggregated together, the cells formed a teratoma= a tumor like structure w/all 3 germ layers!- when injected into blastocyst of normal mice --> cells contributed to all 3 germ layers!- when the ICM of mouse embryos were made only of iPSCs, normal mice were gen.!- txn and DNA methylation pattern almost identical to that of normal mouse ESCs!- Uses of IPSC's!- Huge potential: cell/organ therapies, disease modeling, drug development!- Issues w/using iPSCs in regenerative medicine - Pros: can gen. early stem cells that exact genotype of patient, can correct genetic diseases, minimal ethical issues!- Cons: propensity to be tumorigenic, more likely to be tumorigenic the ESCs because of use of viral tech's for DNA insertion, throughput is low--only a few cells are induced!- Oncogenic Risk Factors Resulting from Induction of Pluripotency!- Integration of gene delivery vectors and transgenes into host cells!- Chromosomal damage during the reprogramming process!- Clonal selection for oncogenic or transformed colonies during cell expansion!- Failure to silence pluripotency networks in differentiated cells!- DNA damage accumulated in cell culture due to somatic mutations!- Aberrect reg of imprinting process!- Reprogramming Cells Through Transdifferentiation!- Transdifferentiation: conversion from one differentiated cell type to another w/o evident de-diff. and re-differentiation!- induced by expression of txn factors and microRNAs!- Ex. of successful transdifferentiation!- Trying to cure diabetes in mice--> treat w/drug that destroys pancreas --> viral delivery of txn factors --> reprogram adult pancreatic exocrine cells to B cells using txn factors --> generated insulin secreting exocrine cells!- Found: their exocrine pancreas produces insulin (mice)!- the new B-cells fixed hyperglycemia --> were able to appropriately respond to glucose3) Discuss cancer stem cells (CSCs), incl. the implications for effective chemotherapy - Cancer Stem Cells (Tumor Stem Cells)!- Hypothesis: some cancers are caused by cancerous stem cells or progenitor cells!- somehow a stem cell may undergo oncogenic transformationn and lose imp. homeostatic control mechanisms!- Support for this hypothesis!- Not all tumors are clonal (derived from a single cell), they're a mix of cell types!- normal stem clels have a hierarchy of slowly dividing cells producing
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