Cell Biology Lecture: Stem Cells

Overview of Final Exam

  • Date: Next Thursday, 01:30

  • Location: Same as previous exams

  • Format:

    • 40 Multiple Choice Questions

    • Covers last four lectures (10 questions per lecture)

  • Duration: 2 hours

  • Advice: Take the exam once and avoid changing answers.

Office Hours and Communication

  • Instructor available on campus Tuesday morning for last-minute questions.

  • Students encouraged to email for questions.

Introduction to Stem Cells

  • Discussion focuses on a broad overview of stem cells.

  • Definition of a Stem Cell:

    • Characterized by two main features:

    1. Self-Renewal: When a stem cell undergoes division, it produces another stem cell.

    2. Differentiation: The other daughter cell differentiates into a specific cell type.

    • Example: Skin stem cells in the basal layer of the epidermis – one maintains the layer while the other differentiates into a mature epithelial cell.

Historical Context of Stem Cell Research

  • 1981: First stem cells isolated from mice.

  • 1996: Dickey-Wicker Amendment passed; prohibits federal funding for research that harms human embryos.

  • 1998: Human embryonic stem cells isolated for the first time from embryos in in vitro fertilization.

  • 2000: NIH publishes guidelines for research using pluripotent stem cells.

  • 2001: Executive order by President George W. Bush halts federal funding for human embryonic stem cell research.

  • 2005-2007: Attempts to pass the Stem Cell Research Enhancement Act, vetoed twice by Bush.

  • 2009: President Obama reverses Bush's ban, opens up funding for embryonic stem cell research.

  • Court Case: Shirley v. Sebelius: Confirmed research on existing embryonic stem cells is allowed, but not the creation of new embryonic lines.

  • 2016: Introduction of the 21st Century Cures Act, which avoids the term "stem cells" but refers to regenerative medicine.

  • 2019: President Trump halts research using human fetal tissue; Biden reverses this ban.

Terminology

  • Potency of Stem Cells: A cell's ability to differentiate into different cell types.

    • Totipotent: Can become any cell type, including placental cells (e.g., zygote).

    • Pluripotent: Can differentiate into any cell type derived from the three germ layers (endoderm, mesoderm, ectoderm); embryonic stem cells are pluripotent.

    • Multipotent: Can differentiate into a limited range of cells; examples include adult stem cells.

    • Oligopotent: Can become only a few different types of cells (e.g., certain immune cells).

    • Unipotent: Can develop into a single cell type (e.g., skin basal cells).

Development and Sources of Stem Cells

  • Embryonic Stem Cells: Isolated from the inner cell mass of a blastocyst.

  • Adult Stem Cells: Isolated from various tissues; somatic stem cells have a more limited differentiation potential compared to embryonic stem cells.

  • Induced Pluripotent Stem Cells (iPS Cells): Adult cells reverse-engineered back to pluripotent state through specific transcription factors.

  • Harvesting: Adult stem cells can be isolated from organs like the liver or blood.

Stem Cells in Research and Treatment

  • Potential Uses of Stem Cells:

    • Tissue replacement for diseases and injuries

    • Examples include regenerative medicine: knee surgeries, diabetes treatment, and restoring sight.

  • Famous Individuals:

    • Athletes like Peyton Manning and Kobe Bryant used stem cell therapy for injuries.

Mechanisms of Stem Cell Differentiation

  • Internal Signals:

    • Transcription factors (Oct4, Sox2, Nanog) maintain stem cell status by balancing their levels.

  • External Signals:

    • By binding to specific receptors (e.g., LIF receptor), pathways like JAK-STAT can prevent differentiation.

Differences Between Embryonic and Adult Stem Cells

  • Embryonic:

    • Pluripotent, capable of becoming any cell type.

    • More abundant and easier to culture.

    • Ethical issues surround their use.

  • Adult:

    • Multipotent, limited in differentiation potential.

    • Harder to isolate and culture; however, carry lower rejection issues when transplanted into the same individual.

    • The presence of existing epigenetic modifications.

Ethical Considerations of Stem Cell Research

  • Pro and con stances; religious and moral arguments often influence public opinion.

  • Important to make informed decisions in future medical practice.

Applications of Stem Cell Therapy

  • Burn Treatment:

    • Use of the 'skin gun' to spray stem cell solutions on burn wounds, improving healing times.

  • Heart Disease: Research indicates that stem cells can regenerate damaged heart tissue after heart attacks.

  • Organ Growth: Efforts to grow organs using stem cells present revolutionary possibilities for transplants in the future.

Wrapping Up

  • Importance of ongoing research and ethical considerations in treatments with stem cells.

  • Instructor's closing thoughts: encouragement to further explore the field of stem cell research.