Stem Cells L23_F2024v2 - PDF

Stem cells Learning objectives: Reading: ECB6 739-745, DevBio11 167-1 Understand that stem cells are capable of self renewal, creating more stem cells and differentiated progeny Understand the differences between embryonic stem cells and adult stem cells...

Stem cells Learning objectives: Reading: ECB6 739-745, DevBio11 167-1 Understand that stem cells are capable of self renewal, creating more stem cells and differentiated progeny Understand the differences between embryonic stem cells and adult stem cells Understand the concept of the stem cell niche Understand the challenges of using adult stem cells or embryonic stem cells in therapy Understand how induced pluripotent stem cells (iPS cells) can be generated Recognize the potential utility of organoids in biomedical  BIOMG1350 PRELIM 4: December 9th, 2024 (L19-24; S10-11) check your room/seat assignment by Saturday practice prelim will be uploaded today review sessions with TAs 1-4PM this Sat/Sun in G01 Biotech BIOMG 1350 FINAL EXAM: Saturday 12/14/2024 9:00 AM BTN100CENT, BTN100EAST Location Barton Hall. BTN100CENT, BTN100EAST We are trying to make previous prelims available for practice Review sessions with TAs 1-3PM December 12th Thursday – Racker room G01 December 13th - Friday – Room TBD (Warren Hall 101, tentative) Watch for instructions announcement next week It is your responsibility to read and know the rules, including academic integrity issues BIOMG 1350 MAKE-UP FINAL EXAM REQUEST: DEADLINE Wednesday Dec 4 th send request to [email protected] with a reason for wanting a make-up exam  a list of ALL your final exams with their course number, date, and time  conflicts will be scheduled between Dec 16 th - 20th, date and location TBD “We are drawn to the subject of stem cells as we are to stories of perpetual motion machines or the fountain of youth; understanding the inner workings of stem cells might help to realize their mythic promise.” Alan Spradling (2001), Nature 414:98 What makes stem cell biology so exciting? Basic science promise: tissue homeostasis, control embryonic development, tissue regeneration, aging! Clinical applications promise: Diabetes, cardiovascular diseases, Parkinsons, Alzheimer, severe burns, spinal cord injuries, etc A stem cell is a cell that is capable of extensive self renewal, creating more stem cells AND more differentiated progeny. (progenitors)  Types of A pyramidal hierarchy of cell potency Cells TOTIPOTENT Totipotent Cells Not Stem Cells Make all embryo cells + placenta Pluripotent Stem Cells: PLURIPOTENT iPSC= Induced Pluripotent Stem C ESC= Embryonic Stem Cells Adult/Tissue Stem Cell MULTIPOTENT HSC= Hematopoietic Stem Ce EpSC= Epidermal Stem Cel NSC= Neural Stem Cells OLIGOPOTENT Committed Progenito Not Stem Cells Terminally differentiated  Adult stem cells Embryonic stem cells Today’s topics Reprogrammin g Applications  Types of stem cells 1) Adult stem cells: committed stem cells that give rise to a limited set of cells and tissue types (multipotent). Examples: hematopoietic, epidermal, neural, hair, melanocyte, muscle, tooth, gut, Present throughout germline stem cells the life of the individual; but they are rare and difficult to isolate, ~1/1000  Adult stem cells reside in a special regulatory environment called niche Stem cell niche: environment producing signals that regulate stem cell proliferation and differentiation The stem cell niche in the mammalian intestine Challenges for using adult stem cells in therapy Adult stem cells can be used in therapy eg: bone marrow Difficult to find and transplantation isolate because of scarcity Need different types of adult stem cells for different therapies Need to identify the niche conditions to maintain and differentiate They generally grow poorly in culture and are difficult to expand  Adult Stem cells Embryonic stem cells Today’s topics Reprogrammin g Applications  Types of stem cells 2) Embryonic stem (ES) cells: derived from cells transiently present in embryogenesis; when cultured, can remain undifferentiated, but can give rise to any cell in the body under appropriate conditions (pluripotent). Inner cell mass (ICM) trophoblast A blastocyst stage mammalian embryo: Inner cell mass (ICM): gives rise to all cells in the embryo body becomes Trophoblast: (pluripotent) the extra- embryonic tissue (part of the placenta) ES cells have tremendous therapeutic potential DevBio11 5-21  Problems associated with the use of ES cells in therapy Technical problems: Histo-incompatibility (ES cells are not patient-derived and can be rejected by the patient’s immune system) The differentiation pathways are not well known and are difficult to identify Ethical problems: Is it ethical/moral to create human blastocysts just for the purpose of generating stem cells for therapies? Is a blastocyst a human individual with on: createrights? personalized pluripotent cells from patients’ own adu  Adult Stem cells Embryonic stem cells Today’s topics Reprogrammin g NTSCs iPSCs Applications Nuclear Transfer Stem Cells = NTSCs e.g. “therapeutic cloning” Problems associated with therapeutic cloning Technical problem: success rate is very low (Dolly: 1/434 nuclei transplanted), a lot of eggs need to be donated Ethical problem: Is it ethical/moral to create human blastocysts just for the purpose of generating stem cells? Is a blastocyst a human individual with rights? Induced pluripotent stem cells (iPS cells) Nobel Prize in Physiology or Medicine 2012 for the discovery that mature cells can be reprogrammed to become pluripotent Shinya Yamanaka OSK transcription regulators are necessary and sufficient for pluripotency Inner Cell Mass (ICM) OSK = Oct4, Sox2, Klf4 Transcription regulators: Expressed in ICM and in cultured ESCs Essential for pluripotency (mutant studies) = necessary Are they also sufficient for pluripotency? = sufficient (screening ~22 of them) Differentiated somatic cell Shinya Yamanaka & Helen M. Blau NATURE|Vol 465|10 June  The master regulators of pluripotency participate in a self- sustained positive feedback loop Klf 4 Figure 22-41 MBC6 Overall, ~1500 genes are differentially expressed in response Problems associated with the use of iPS cells in therapy Technical problems: The pluripotency factors must be turned off in order to allow iPS cells to differentiate and to avoid tumorigenesis iPS cells are not identical to ES cells (eg. differences in some epigenetic marks) Somatic cells used to make iPS cells may carry damaging mutations Safety of reprogramming is not completely known Although straightforward it is still very  Adult Stem cells Embryonic stem cells Today’s topics Reprogrammin g Applications iPS cells can be used to study and treat genetic disease Cultured ES (or iPS) cells can give rise to a three- dimensional organoid.  Organoids can also be obtained from tissue SCs o and Clevers (2013) Science 340: 1190 Adult hematopoietic stem cells are frequently used in clinics Find immune- Inject the cells into Use strong compatible donor and the chemotherapy or collect stem cells to bloodstream of the radiation to kill the transplant. (In some patient; stem cells cancer cells, but this cases, patient can will find their way treatment also kills donate marrow prior to the marrow and hemopoietic stem to treatment.) repopulate the cells. blood.  Basic Science Applications of ESCs: The Nobel Prize in Physiology/Medicine 2007 for introducing specific gene modifications in mice via embryonic stem cells Gene targeting to introduce mutations (e.g. CRISPR/Cas9) Mutant ES cells Breeding to transmit mutati to next generation of mice Blastocyst develops in Clump of mutant foster mother into a ES cells injected in chimeric mouse; the blastocyst ES cells contribute to all igure 22-40 MBC6e tissues Example of gene knockout experiment: leptin knockout mice are obese * KO experiment helped show that leptin is a hormone which regulates body fat as well as the sensation of hunger, and its loss results in obesity, susceptibility to diabetes, and other complications.  Stem cells and cancer 1) Stem cells are likely to be important targets of cancer long-lived ->accumulate mutations proliferative -> more prone to transformation evidence of ‘cancer stem cells’ – rare tumor cells can rebuild a tumor 2) Stem cells regulatory signals are often perturbed in cancer Quiescence signals -> inactivated Activation signals -> super-activated Differentiation signals -> inactivated or abberrant Stem cell renewal and pro-cancer pathways are linked Reya et al. (2001) Nature 414:10