Understanding Stem Cells part 2

Once they had recognized the medical potential of regeneration through the success of bone marrow transplants, scientists sought to identify similar cells within the embryo. Early studies of human development had demonstrated that the cells of the embryo were capable of producing every cell type in the human body. Scientists were able to extract embryonic strem cells from mice in 1980s, but it wasn't until 1998 that a team of scientists from the University of Wisconsin-Madison became the first group to isolate human embryonic stem cells and keep them alive in the laboratory. The team knew that they had in fact isolated stem cells because the cells could remain unspecialized for long periods of time, yet maintained the ability to transform into a variety of specialized cell types, including nerve, gut, muscle, bone, and cartilage cells.

Understanding Stem Cells part 1

For centuries, scientists have known that certain animals can regenerate missing parts of their bodies. Humans actually share this ability with animals like the starfish and the newt. Although we can't replace a missing leg or a finger, our bodies are constantly regenerating blood, skin, and other tissues. The identity of the powerful cells that allow us to regenerate some tissues was first revealed when experiments with bone marrow 1950s established the existence of stem cells in our bodies and led to the development of bone marrow transplantation, a therapy now widely used in medicine. This discovery raised hope in the medical potential of regeneration. For the first time in history, it became  possible for physicians to regenerate a damaged tissue with a new supply of helathy cells by drawing on the unique ability of stem cells to create many of the body's specialized cell types.

STEM CELL part 62

The following is a list of steps in successful cell-based treatments that scientists will have to learn to control to bring such treatments to the clinic, To be useful for transplant purposes, stem cells must be reproducibly made to:

• Proliferate extensively and generate sufficient quantities of cells for making tissue
• Differentiate into the desire cell type
• Survive in the recipient after transplant
• Integrate into the surrounding tissue after transplant
• Function appropriately for the duration of the recipient's life
• Avoid harming the recipient in any way

STEM CELL part 61

To realize the promise of novel cell-based therapies for such pervasive and debilitating diseases, scientists must be able to manipulate stem cells so that they possess the necessary characteristics for successful differentiation, transplantation, and engraftment.

STEM CELL part 60

In people who suffer from type I diabetes, the cells of the pancreas that normally produce insulin are destroyed by the patient's own immune system. New studies indicate that it may be possible to direct the differentiation of human embryonic stem cells in cell culture to form insulin-producing cells that eventually could be used in transplantation therapy for persons with diabetes.

STEM CELL part 59

A few small studies have also been carried out in humans, usually in patients who are undergoing open heart-surgery. Several of these have demonstrated that stem cells that are injected into the circulations or directly into the injured heart tissue appear to improve cardiac functions and/or induce the formation of new capillaries. The mechanism of these repair remains controversial, and the stem cells likely regenerate heart tissue through several pathways. However, the stem cell populations that have been tested in these experiments vary widely, as do the conditions of their purification and application. Although much more research is needed to assess the safety and improve the efficacy of this approach, these preliminary clinical experiments show how stem cells may one day be used to repair damaged heart tissue, thereby reducing the burden of cardiovascular disease.

STEM CELL part 58

The use of embryonic and adult-derived stem cells for cardiac repair is an active area of research. A number of stem cell types, including embryonic stem cells, cardiac stem cells that naturally reside within the heart, myoblast (muscle stem cells), adult bone marrow-derived cells including mesenchymal cells (bone marrow-derived cells that give rise to tissues such as muscle, bone, tendons, ligaments, and adipose tissue), endothelial progenitor cells (cells that give rise to the endothelium, the interior lining of blood vessels), and umbilical cord blood cells, have been investigated as possible  sources for regenerating damaged heart tissue. All have been explored in mouse or rat models, and some have been tested in larger animal models, such as pigs.