Stem cells---what are they?
- Stem cell is the origin of life.
- Stem cell has ability to reproduce itself for long period or, in the case of adult stem cell, throughout the life of the organism (Division and Renewal).
- Stem cell give rise to progeny that differentiate into mature functioning cells of that tissue (Differentiation).
- Ability of the stem cell to be attracted to site of injury (Homing).
- Ability to unite with the new tissue (Engraftment).
Stem cells classification
Stem cells are present both in the embryo and adult.
Embryonic stem cells (ESCs) derived from blastocysts (early embryonic stages) which are a group of undifferentiated cells. They can develop into any types of more than 200 cells in the body. Development and application of embryonic stem cells, however, gave rise to some controversy on moral issues, such as illegal abortion, or replication of human beings and these would give rise to the concerns of the community.
Adult stem cells (ASCs) is an undifferentiated (unspecialized) cells that occurs in a differentiated specialized tissue, renews itself and divide to replenish dying cells and regenerate damaged tissues.
ASCs can be classified into different types:
Hematopoietic stem cells (HSCs) are cells isolated from the umbilical cord blood, peripheral blood or bone marrow that can renew itself, can differentiate to all types of blood cells, for example, white blood cells, red blood cells and platelets.
Mesenchymal stem cells (MSCs) can be isolated from different tissues including cord blood, bone marrow, peripheral blood, fallopian tube, and fetal liver and lung. MSCs may prove useful for repair and regeneration of a variety of tissues and/or organs. MSCs also have ability to modify immune responses and engraft in allogeneic recipients.