Introduction to Stem Cells

Study Notes

Stem cells are undifferentiated cells capable of becoming various cell types.
They can proliferate endlessly to produce more stem cells.
Stem cells are crucial for tissue and organ development, serving as building blocks for the human body.

Unspecialized: They lack tissue-specific structures for specialized functions.
Self-renewal: They can divide and renew themselves for extended periods.
Potency: Stem cells can give rise to various differentiated cells.
Plasticity: They can change into different cell types.
Uncommitted: Stem cells remain uncommitted until receiving signals to develop into specialized cells.

Source: Embryonic, Adult
Potency:
- Totipotent: Can differentiate into all cell types, including placental tissue. Example: Morula
- Pluripotent: Can differentiate into almost all cell types, excluding placental tissue. Example: Cells from the inner cell mass of a blastocyst
- Multipotent: Can differentiate into multiple specialized cells within a specific germ layer. Example: Blood stem cells can create all blood cells but not neural cells (ectoderm) or liver cells (endoderm).
- Unipotent: Can only produce one cell type but possess self-renewal properties. Example: Muscle stem cells, Cardiac stem cells

Derived from the inner cell mass of a blastocyst (early pre-implantation embryo).
Isolation of the inner cell mass results in destruction of the blastocyst, raising ethical concerns.
Pluripotent, capable of differentiating into all cell types derived from the three primary germ layers (ectoderm, endoderm, and mesoderm).

Undifferentiated cells found among differentiated cells within a tissue or organ.
Can renew themselves and differentiate into specialized cell types of the tissue or organ.
Primarily responsible for maintaining and repairing tissues.
Functions:
- Replace physiologically lost cells, e.g., blood (hematopoietic stem cells), GIT epithelial cells, skin, & hair.
- Divide in response to tissue injury or infection, e.g., skeletal muscle regeneration.

Excess embryos: From assisted reproductive technologies, like in vitro fertilization.
Umbilical cord blood: Rich source of stem cells compared to adult stem cells, readily expandable.
Bone marrow: Source of hematopoietic stem cells (blood-forming cells).
Fetal blood and tissue: Neural stem cells, hematopoietic stem cells, and mesenchymal stem cells can be harvested.