Abstract
Even before tissue engineering and regenerative medicine took shape, scientists have known about the fact that animals like the star fish were capable of regenerating missing body parts.
Although, humans share this ability, humans cannot regenerate a missing finger or toe. Instead, the human body constantly regenerates skin cells, blood cells, and tissues.
In the 1950s, experiments were conducted by scientists to identify the source of tissue and cell regeneration in humans. Experiments conducted with the bone marrow revealed the existence of certain powerful cells called stem cells that aided in tissue regeneration.
In 1998, James Thompson of the University of Wisconsin-Madison became the first scientist to isolate and use human embryonic stem cells.

Types of Stem Cells

Stems cells, also called mother cells, have the ability to renew, multiply, maintain, and potentially develop into other cell types such as brain, blood, skin, bones, muscles, and heart cells. There are three known types of stem cells namely: Pluripotent Stem Cells (PS Cells), Fetal Stem Cells, and Adult Stem Cells.
Pluripotent stem cells divide for longer periods all the while making cell types within the organism. Embryonic stem cell (ES Cell) is the best known pluripotent stem cell type and is derived from the embryos.
Fetal stem cells are derived from a developing human fetal tissue. These cells retain certain characteristics of the tissue they were derived from.
Adult stem cells or non-embryonic somatic cells are derived from adult body tissues. The best example is the bone marrow that is rich in stem cells and is used in treating blood related diseases.


Stem Cells and Animals
Predominantly, scientists conduct various medical experiments on animals before human application. For years, human cells were implanted into mice to test the efficiency of new drugs, medical devices, and other medical procedures. Stem cells were implanted into animals to ensure the successful incorporation of stem cells into tissues with no harmful consequences and malfunctions to the body. For example, stem cells are introduced into a mouse for various purposes including: to test for insulin-producing cells in the treatment of type 1 diabetes, to trace the progression of certain tissue related diseases in humans, and to test new drugs. An organism containing tissues or cells from another organism of the same or different species is called a chimera. For example, a chimera mouse that is injected with human cells is used in the study of various human diseases and drug testing.

Stem Cells over the Past 40 Years

The top developments in stem cell biology over the last 40 years include:
Flow cytometry is a well-established technique used in the enrichment of adult stem cell types. This technique is considered a major advancement in stem cell biology because it also differentiates progeny of pluripotent cells.
In 1964, the first embryonic stem cells were isolated from mice. This is another major breakthrough because it showed that inner cell mass isolated from a mouse embryo survives and develops into cell colonies that are cultured as cell lines we well.
The development of mammalian cloning as demonstrated by Briggs and King that somatic cell nuclear transfer could possibly be used in cloning frogs. The isolation and use of human embryonic stem cells in 1998 is a unique breakthrough in identifying characteristics for human development. The other major breakthroughs include research on cancer stem cells, induced pluripotent stem cells, tissue engineering with stem cells, genetic manipulation improvement, and mesenchymal stem cells.

Key Therapeutics of Stem Cells
The important therapeutics of stem cell research include: Nerve cells that could potentially treat Parkinson's disease, Alzheimer's condition, stroke, multiple sclerosis, congenital brain damage, and spinal cord damage; as blood cells that treat leukemia, immune deficiencies, inherited blood disorders, and in the treatment of cancer; as heart muscle cells in treating congestive heart failures and cardiac arrests; as pancreatic cells (insulin-producing cells) in treating diabetes; as retinal cells in treating different blindness forms; as liver cells in treating hepatitis; as bone matrix cells in treating osteoporosis; and in animal research for the regrowth of missing teeth.

Stem Cells Today

Stem cells transplants are used in the treatment of several cancer types. Another successful development is the use of donor stem cells in the treatment of serious inherited blood disorders such as sickle cell disease and Fanconi anemia. Stem cells are used to address various clinic challenges today.

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By Meena