4.1 Types of stem cells and their ethical status

Stem cells, the building blocks of life, come in various types with unique properties and ethical considerations. From embryonic to adult and induced pluripotent stem cells, each offers distinct potential for medical breakthroughs while raising important moral questions.

The use of stem cells in regenerative medicine promises groundbreaking treatments for previously incurable conditions. However, it also presents challenges like tumorigenicity, genetic instability, and complex ethical dilemmas that must be carefully navigated.

Types of Stem Cells

Types of stem cells

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• Embryonic stem cells (ESCs)
  • Derived from the inner cell mass of a blastocyst, an early-stage embryo (3-5 days post-fertilization)
  • Pluripotent, capable of differentiating into any cell type in the body (over 200 cell types)
  • Ethical concerns: destruction of human embryos, potential for commodification of human life
• Adult stem cells (ASCs)
  • Found in various tissues throughout the body (bone marrow, fat, skin)
  • Multipotent, capable of differentiating into a limited number of cell types within their tissue of origin
  • Ethical considerations: less controversial than ESCs as they do not involve the destruction of embryos
• Induced pluripotent stem cells (iPSCs)
  • Created by reprogramming adult somatic cells to a pluripotent state using specific transcription factors (Oct4, Sox2, Klf4, c-Myc)
  • Possess similar properties to ESCs, including pluripotency
  • Ethical advantages: avoid the destruction of embryos, can be derived from a patient's own cells (autologous) reducing the risk of immune rejection

Ethics of stem cell use

• Embryonic stem cells
  • Arguments for:
    • Potential for significant medical advances in regenerative medicine and disease modeling
    • May lead to the development of life-saving treatments for currently incurable conditions (Parkinson's disease, spinal cord injuries)
  • Arguments against:
    • Destruction of human embryos is morally objectionable to some as it is seen as the taking of human life
    • Concerns about the commodification and instrumentalization of human life
• Adult stem cells
  • Arguments for:
    • Less ethically controversial than ESCs as they do not involve the destruction of embryos
    • Can be obtained from a patient's own tissues reducing the risk of immune rejection
  • Arguments against:
    • Limited differentiation potential compared to ESCs which may restrict their therapeutic applications
    • Obtaining sufficient quantities of ASCs can be challenging
• Induced pluripotent stem cells
  • Arguments for:
    • Avoid the ethical issues associated with the destruction of human embryos
    • Can be derived from a patient's own cells minimizing the risk of immune rejection
    • Provide a potentially unlimited source of patient-specific pluripotent cells
  • Arguments against:
    • Reprogramming process may introduce genetic abnormalities raising safety concerns
    • Long-term stability and differentiation potential of iPSCs are not yet fully understood

Stem cells in regenerative medicine

• Potential benefits
  • Regeneration of damaged or diseased tissues (spinal cord injuries, neurodegenerative disorders, heart disease)
  • Development of patient-specific cell therapies reducing the risk of immune rejection
  • Improved understanding of disease mechanisms through the creation of disease-specific cell models
• Risks and challenges
  • Tumorigenicity: pluripotent stem cells (ESCs and iPSCs) may form teratomas if not properly differentiated before transplantation
  • Genetic instability: reprogramming process in iPSCs may introduce genetic abnormalities raising safety concerns
  • Immunogenicity: allogeneic stem cell transplants may trigger an immune response requiring immunosuppression
  • Ethical concerns: destruction of human embryos (ESCs) and the potential for commodification of human life
  • Regulatory hurdles: ensuring the safety and efficacy of stem cell-based therapies requires rigorous testing and regulatory oversight