Humans are composed of 30 trillion cells in constant flux.
Cells regenerate; nearly 330 million new cells replace old ones daily.
Intestinal lining renewed every 3-5 days; red blood cells live 120 days.
Regeneration involves stem cells, vital for maintaining body functions.
What are Stem Cells?
Stem cells have two unique abilities:
Self-renewal: Can create more stem cells.
Differentiation: Can become different types of cells.
Different from somatic cells (e.g., skin, muscle, brain), which cannot divide and are 'terminally differentiated'.
Differentiation and Potency
Differentiation was once thought irreversible, but modern science challenges this.
Types of Stem Cells by Potency:
Totipotent: Can become any cell of an organism (e.g., zygote).
Pluripotent: Can form almost all cell types (e.g., embryonic stem cells).
Multipotent: Can become various cells of a specific type (e.g., hematopoietic stem cells).
Unipotent: Can only become one type of cell (e.g., muscle stem cells).
Gene Expression and Cell Identity
All cells have the same DNA but differ in gene expression.
Stem cells haven't undergone changes in gene expression yet.
Gene expression influences cell identity; can potentially be altered to change a cell’s type.
Breakthrough in Stem Cell Research
2006 Discovery: Shinya Yamanaka and Kazutoshi Takahashi reverted skin cells to pluripotent stem cells using 4 genes, leading to induced pluripotent stem cells (iPSCs).
Known as Yamanaka factors.
Awarded Nobel Prize in 2012 for this groundbreaking work.
Applications of Stem Cells
Therapies:
Bone marrow transplants for blood diseases.
iPSCs research for understanding organ/tissue development and congenital diseases.
Stem cells are key to critical and protective bodily functions.