Stem Cells

Stem cell

An unspecialized cell with the ability to self-renew and differentiate into specialized cell types.

Self-renewal

The process by which stem cells divide to produce more stem cells, maintaining the stem cell pool.

Differentiation

The process by which a stem cell becomes a more specialized cell type.

Embryonic stem cell

A pluripotent stem cell derived from the inner cell mass of a blastocyst, capable of forming many tissue types.

Inner cell mass

The group of cells inside the blastocyst that gives rise to embryonic stem cells.

Blastocyst

A 5 to 6 day stage embryo with an outer layer and inner cell mass; source of embryonic stem cells.

Trophectoderm

The outer layer of the blastocyst that contributes to placental structures.

Pluripotent

Able to differentiate into many tissue types, potentially all cell types of the body, but not extraembryonic tissues.

Multipotent

Able to differentiate into multiple, but limited, cell types within a tissue lineage.

Progenitor cell

A lineage-committed cell derived from a stem cell that will differentiate into a specific cell type.

Asymmetric cell division

A division that yields one stem cell and one progenitor cell, enabling simultaneous self renewal and differentiation.

Adult stem cell

An undifferentiated cell in a tissue that can self-renew and differentiate into cell types of that tissue.

Tissue stem cell

A stem cell located in a specific tissue that maintains and regenerates that tissue.

Stem cell niche

The specialised microenvironment within a tissue that supports stem cell maintenance and regulates activation.

Hematopoietic stem cell

A tissue stem cell that gives rise to all blood cell types, including myeloid and lymphoid lineages.

Myeloid lineage

Blood cells derived from hematopoietic stem cells such as monocytes, macrophages, neutrophils, eosinophils, basophils, erythrocytes and platelets.

Lymphoid lineage

Blood cells derived from hematopoietic stem cells such as T cells, B cells and NK cells.

Mesenchymal stem cell

A tissue stem cell that differentiates into cartilage, muscle, fat and connective tissues.

Neural stem cell

A tissue stem cell that gives rise to neurons, astrocytes and oligodendrocytes in the brain.

Epithelial stem cell

A tissue stem cell that generates epithelial cells for skin and organ linings, including hair follicles.

Induced pluripotent stem cell (iPS)

A somatic cell reprogrammed by genes to become pluripotent, like ES cells, avoiding embryos.

Reprogramming

The process of converting a differentiated body cell into an induced pluripotent stem cell.

Umbilical cord blood

A source of hematopoietic stem cells found in cord blood.

Placental tissue

A source of hematopoietic stem cells and other stem cells from the placenta.

In vitro culture

Growing stem cells in laboratory conditions outside the body.

Regeneration

Replacement of damaged or dead tissue by stem cell activity.

Homeostasis

Maintenance of stable internal conditions, in part through stem cell–mediated regeneration.