Stem Cells & Regeneration 2

  • Overview of Stem Cells in Adult Tissue

    • Investigating the role of stem cells in maintaining adult tissues, specifically the ocular surface.
    • Eye anatomy:
    • Composed of cornea, lens, retina, iris.
    • Mouse eyes have larger lenses relative to their body size compared to human eyes, affecting their refractive power.

  • Ocular Surface Maintenance

    • Importance of a transparent and smooth ocular surface.
    • Stem cells are crucial for maintaining the epithelium of the eye; dysfunction can lead to cloudiness and infections.

  • Corneal Anatomy

    • Cornea composed primarily of collagen; the epithelial layer must be maintained to prevent damage.
    • Limbal zone:
    • Junction between the cornea and conjunctiva, with distinct epithelial cell types.
    • Expression of keratin 12 unique to corneal epithelial cells, indicating specialized function.

  • Stem Cells in the Cornea

    • Comparison with skin stem cells, which are present in hair follicles.
    • Using transgenic mice expressing the Lux gene to visualize patterns of corneal epithelial cells and their migration.
    • Blue patches represent different genetic expression linked to specific cell migration patterns.

  • Cell Migration in the Eye

    • The centripetal migration of cells from the limbus to the corneal center is essential for normal function.
    • Time-lapse microscopy shows the reformation of striped patterns after abrasion injury.

  • Physics of Cell Migration

    • Active soft matter physics used to model cell behavior and migration patterns.
    • Comparisons drawn between cell migration in corneal epithelium and flocking behavior in birds.

  • Identifying Stem Cells

    • The concept of immortality of stem cells tested through cloning strategies.
    • Stem cells characterized by their ability to form large, lasting colonies in vitro.

  • Location of Stem Cells

    • Experiments established the limbal region around the cornea as the home for stem cells.
    • Labeling studies using bromodeoxyuridine (BrdU) to identify proliferating cells and assess stem cell activity.

  • Label Retaining Assays

    • Design to identify slow-cycling stem cells by using long-term labeling followed by a chase period.
    • Slow-dividing populations retain labels longer, providing insights into local stem cell populations.

  • Response to Injury

    • Experiments show that limbal stem cells rapidly divide in response to corneal injury.
    • Age-related decline in functional capacity of stem cells confirmed through comparative studies.

  • Therapeutic Applications

    • Limbal stem cell deficiency can lead to irreversible vision problems.
    • Potential treatments include stem cell transplants from donor eyes to repair injured corneal surfaces.

  • Conclusion and Importance of Study

    • The study emphasizes the importance of localized stem cell maintenance within the ocular surface.
    • Experiments provide validation of hypotheses concerning stem cell function and response to injury in a controlled, observable environment.

  • Key Regulatory Genes

    • Expression of genes like ABCG2 and P63 delineates stem cell populations and offers insights into their functional roles in ocular health.