L4 stem cells
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Intended Learning Outcomes
Identify essential characteristics of stem cells.
Understand stem cell potencies and their relevance to research applications.
Explain the use of stem cells in research.
Consider ethical implications of stem cell research.
Understand therapeutic potential of stem cell-derived products.
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What are Stem Cells?
Definition: Unspecialised cells capable of indefinite reproduction and differentiation into specialized cell types.
Types: Embryonic and Adult stem cells.
Functional Capabilities: Generate tissues, organs, or complete organisms.
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Stem Cell Potencies
Totipotent: Can generate all tissues of the embryo and extra-embryonic tissues (e.g., zygote/Fertilized ovum).
Pluripotent: Can generate cells from all three germ layers but not extra-embryonic tissues (e.g., embryonic stem cells).
Multipotent: Differentiate into multiple lineages, but not all germ layers (e.g., hemopoietic stem cells).
Unipotent: Differentiate along only one lineage (e.g., most adult stem cells in normal conditions).
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Hierarchy of Stem Cell Potency
Totipotent: Fertilized egg, forms embryo and placenta. EMBRYONIC
Pluripotent: Isolated from the blastocyst's inner cell mass. EMBRYONIC
Multipotent: Includes types like hematopoietic, neural, and mesenchymal stem cells. ADULT
Unipotent: Examples include fully differentiated tissue-specific cells. ADULT
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Isolation of Stem Cells
Adult stem cells can be isolated from:
Bone marrow
Adult tissues via biopsy
Embryonic stem cells can be isolated from:
Fetal tissues post-pregnancy termination.
Umbilical cord blood at birth
Autologous vs. Allogeneic Stem Cells
Autologous: Cells taken from an individual and returned to the same individual.
Allogeneic: Cells taken from one individual and used for another.
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Reproductive Cloning Introduction
Focus on reproductive cloning and its applications.
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Somatic Cell Nuclear Transfer (SCNT)
Process of reproductive cloning through SCNT:
Use of differentiated animal cells.
Removal of nucleus from an enucleated egg.
Replacement with the nucleus of a differentiated cell.
Potential to develop into all tissues/organs of an organism if the donor nucleus retains genetic potential.
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Nuclear Transplantation in Xenopus Laevis
Historical context from 1970s research by John Gurdon.
Demonstrated a differentiated frog cell's nucleus can guide development into a tadpole.
Nucleus from a differentiated frogcell can direct development oftadpole
Efficiency decreases with donor cell differentiation.
Significantly influenced stem cell technology development.
in principle; you can use a differenciated cell, put into denucleated egg and grow a ‘clone’
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Mammalian Cloning - Dolly the Sheep
Achieved in 1997 at the Roslin Institute:
Cloned lamb from adult sheep using nuclear transplantation.
Of hundreds of embryos, only one (Dolly) developed normally.
Confirmed that chromosomal DNA was identical to the nucleus donor, showcasing potential for cloning in mammals.
Range of mammals were cloned after this - rats, cats, cows, horses, pigs, dogs, monkeys
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Challenges in Mammalian Cloning
Cloned embryos developed normally to birth at a low percentage.
Cloned animals show variations in appearance and behaviour and don’t always behave identically
Health issues observed in Dolly, e.g., premature ageing signs leading to euthanasia - died at 6.
Cloned mice prone to obesity, pneumonia, liver failure and premature death
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Ethical Considerations in Human Cloning
Human reproductive cloning is banned:
Maximum culture time of 14 days for embryos.
Prohibition on implantation into humans linked to ethical concerns.
Interest remains in generating stem cells for therapeutic cloning.
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Human Embryonic Stem Cells (hESC)
Derived from the inner cell mass of blastocysts post-IVF.
Capable of indefinite self-renewal.
Pluripotent - able to derive all cells from all 3 dermal layers.
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Therapeutic Cloning
Description of therapeutic cloning as application of SCNT:
Producing patient-specific cell lines from embryos intended to replace damaged tissues.
Not intended for in utero transfer; used to solve specific medical or tissue-related issues.
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Stem Cells in Therapy
Role of stem cells in regenerative medicine:
Functions to repair, replace, restore, and regenerate tissues.
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Applications of Embryonic Stem Cells
Areas of application in research and industry:
Basic research tools.
Drug testing and disease modelling patient specific cells
Toxicology assessments.
Drug discovery and therapeutic developments.
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The Cloning Scandal of Hwang Woo-Suk
Overview of the ethical and scientific challenges:
Hwang Woo-Suk's fraudulent practices and the fallout.
unethically sourced oocytes
Shifts in public perception and research ethics post-scandal.
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Advances in hESC Derivation
Achievements in deriving human embryonic stem cells via somatic cell nuclear transfer.
Research led to breakthroughs in generating patient-specific ESCs for therapeutic applications.
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Ethical Objections to hESC
Controversies surrounding hESC derivation:
Definitions of life concerning embryos.
Global variability in ethical policies, often influenced by religious beliefs.
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Teratoma Formation Risks
benign tumours arising from totipotent cells containing tissues of more than one germ layer, often occurring in ovary or testes
Potential risks associated with pluripotent cells remaining in differentiated cell therapies.
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Clinical Concerns with hESC
Challenges in scaling up for clinical use:
Differentiation issues and the potential for teratoma formation.
Risks associated with animal products in culture.
Off-the-shelf therapy would still require huge bank to tissue match, otherwise immune rejection issues
Animal products used in culture, infection and immune risks
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Harvesting Mouse Embryonic Stem Cells
mouse embryonic stem cell harvesting techniques:
From blastocyst stage, utilizing LIF and feeder cells for expansion.
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Transgenic Mice
Contributions of murine ES cells in developing transgenic animals.
Historical context and Nobel Prize recognition for foundational research in the field.
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Genetically Modified Animals
Use of ES cells to introduce fluorescent marker genes and monitor gene expression changes.
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Advances in Genetic Research
Significance of knock-out mouse technologies and transgenic mice (over expressed genes) in basic and medical research.
models can be used to test for things like Alzheimer's
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Comparative Overview of Stem Cells
Distinction between embryonic and adult stem cells, highlighting sources and capabilities.
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Applications of Adult Stem Cells
Potential uses of adult stem cells across various tissues:
Bone, cartilage, CNS, heart, skin, etc.
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Hematopoietic Stem Cell Hierarchies
Detailed view of the hierarchical differentiation of hematopoietic stem cells and their precursors.
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Uses of Hematopoietic Stem Cells
Applications in transplantations for blood system restoration in conditions like leukemia and sickle cell anemia, among others.
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Adult vs. Embryonic Stem Cells in Regenerative Medicine
Comparison of ethical implications and inherent limitations in differentiation potential.
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Mapping Stem Cell Origins
Overview of the origins and differentiation capabilities of various stem cells.
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Induced Pluripotent Stem Cells (iPS)
Introduction and reprogramming of somatic cells into iPS cells using four master regulatory genes.
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Dual Potential of iPS Cells
Two primary uses of iPS cells:
Cell therapy for tissue replacement.
Research and drug discovery to understand diseases.
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Nobel Prize Recognition
Achievements of John B Gurdon and Shinya Yamanaka in stem cell reprogramming recognized by the Nobel Prize in Physiology or Medicine.
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Research Potential of iPS Cells
Understand diseases using models from iPS cells to identify treatments and potential cures.
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Therapeutic Outcomes with iPS Cells
Examples of successful stem cell-mediated treatments for conditions like type 1 diabetes.
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Advantages and Challenges of iPS Cells
Ethical considerations in using iPS cells as alternatives to hESCs along with potential issues like oncogenesis.
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Key Questions in Stem Cell Therapy
Overview of critical considerations for effective stem cell therapy applications:
Is cell replacement practical?
Mechanisms of cell repair (direct and indirect effects).
Recovery mechanisms.
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Methods of Obtaining Stem Cells (January 2014)
Overview of various methods to obtain stem cells:
Donated embryos, cloning, etc.
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Exciting Developments in Stem Cell Research
Reports of Stimulus-Triggered Acquisition of Pluripotency (STAP) as a promising but controversial approach to stem cell research.
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Investigations into Misconduct
Findings related to scientific misconduct in the 2014 STAP paper scandal, leading to retractions and loss of credibility.
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Cautionary Tales in Research
Importance of safety and adherence to ethical practices in stem cell research and trials.
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Conclusion on Stem Cell Research
Overview of the potential, promises, and responsibilities tied to stem cell research, emphasizing ethical considerations in future projects.
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Reputable Information Sources
References to accredited sources for stem cell research, clinical trials, and regulatory bodies associated with the field.