A Stem cell may be defined as an unspecialized cell that gives rise to a specific specialized cell, such as sperm cells, blood cells, epithelial cells present in the skin, retinal cells present in the eye and so on. These cells eventually make up specialized tissues and organs.
Scientists and Researchers have been interested in cell biology since the time the microscopes were first used in the early 1800s. The phenomena of cell propagation and differentiation were observed for the first time and cells were recognized as the building blocks of life, capable of giving rise to other cells and key to understanding human development.
The first human stem cell line was created in 1998, using cells harvested from embryos produced through in vitro fertilization. The use of human embryonic stem cells is allowed in some countries and prohibited or restricted in others.
Types of Stem Cells
There are two major types of stem cells:
•Embryonic Stem Cells
•Adult Stem Cells
Embryonic Stem Cells – These are located in the inner mass of a blastocyst (an embryo at a very early stage of development), and they eventually give rise to every cell type of the adult organism.
Adult Stem Cells – These are found in some tissues in the adult body, such as the epidermis of the skin, the lining of the small intestine, and the bone marrow, where they serve in the regeneration of old or worn tissue.
Stem Cells – A Boon
Since the time they were first discovered, stem cells have consistently found their use in medical science. In cancer treatment, blood-forming adult stem cells are routinely harvested from bone marrow, stored, and then re-infused into patients to replace blood cells destroyed by chemotherapy or radiation therapy. This potential for replacing damaged tissues has aroused great interest in using embryonic stem cells to treat a number of other conditions, such as Parkinson disease, severe burns, and damage to the spinal cord. Mouse embryonic stem cells are widely used to create genetically modified mice that serve as models for investigating human disease.
Stem Cells –Their Share of Controversy
The use of human embryonic stem cells, which requires destroying the blastocysts from which they are obtained, has raised objections by those who feel blastocyst-stage embryos are human beings. The controversy surrounding the use of stem cells is primarily concerned with the creation, treatment, and destruction of human embryos incident to research involving embryonic stem cells. However, not all stem cell research involves the creation, use, or destruction of human embryos. For example, adult stem cells, amniotic stem cells and induced pluripotent stem cells do not involve human embryos.