What stem cells are?
In the beginning there is the stem cell: the origin of an organism's life. Therefore the paper will analyze in detail what these stem cells are, their properties, different types, the controversy over embryonic stem cells and the potential uses of stem cells
It is a single cell that can give rise to progeny that differentiate into any of the specialized cells of embryonic or adult tissues; That is, it is totipotency. The ultimate stem cell, the fertilized egg, divides five or six times to give rise to branches of cells that form various differentiated organs. During these early divisions, each daughter cell retains totipotency. Then, through a series of divisions and differentiations, the embryonic stem cells lose potential and gain differentiated function (a process known as determination). During normal tissue renewal in adult organs, tissue stem cells give rise to progeny that differentiate into mature functioning cells of that tissue. Stem cells with less than totipotentiality are called "progenitor cells." Except for germinal cells, which retain totipotency, most stem cells in adult tissues have reduced potential to produce cells of different types" (Baharvand, p. 14) (i.e., are determined). However, there is increasing evidence for retention of some toti/multi-potent cells in the tissues adults, especially in the bone marrow.
Properties of stem cells
The major properties thought to characterize stem cells have been inferred from investigations of classic stem cell-fed lineage renewal systems, including bone marrow, intestinal epithelium, and epidermis. Essential properties expected of stem cells include the capacity to (1) proliferate repeatedly, (2) renew the stem cell population, and (3) generate sufficient differentiated progeny to maintain or regenerate the functional capacity of a tissue. Classic stem cells are thought to exhibit undifferentiated cellular phenotypes, to express variable differentiation potentials, and to be able to proliferate continuously (actual stem cells) or to be proliferationally quiescent until needed (potential or facultative stem cells). Although classic stem cell-fed lineage systems have been used to infer the properties of stem cells, evidence now suggests the existence of stem cells in many tissues that do not contain active stem cell-fed lineages, such as the central nervous system and liver (Benson, p. 3). These newly discovered stem cells appear to have properties that differ from those proposed for classic stem cells.
The different types
Embryonic stem cells are the most widely discussed type of stem cell. They have the ability to replicate themselves indefinitely in the laboratory and the ability to generate any type of cell in the human body. The mystery lies in how scientists can coax stem cells into forming various types of cells. Embryonic stem cells are taken from an early-age embryo, four to five days old, a process which results in the destruction of the embryo. Adult stem cells are sometimes called post-natal ("after birth") stem cells, because they are found throughout the bodies of children and adults. These cells have as their natural function the creation of other cells that the body needs to replenish. For example, stem cells in the bone marrow replenish the body's supply of blood cells. Other adult stem cells are found in the nervous system and various organs. Stem cells may also be found in fetuses and the umbilical cord that connects mother to baby, which is cut at birth. Although adult stem cells generally produce a single type, or a limited number of types, of cell in the human body, research indicate that, like embryonic stem cells, it is possible to manipulate adult stem cells into developing various types of cells.
The controversy over embryonic stem cells
Despite the perceived advantages of embryonic stem cells over adult stem cells, research with embryonic stem cells is highly controversial. Creating a stem cell line - though the cells replicate themselves indefinitely - must begin with step of destroying an embryo during the early days of its existence. For some people, this act poses no moral problem. The collection of stem cells takes place at a time well before the embryo takes on a human form and well before the stage at which legal abortions take place. However, many people believe that human life begins at the moment the egg is fertilized, and because the destruction of the embryo to harvest the stem cells takes place research as the moral equivalent of murder.
What are the potential uses of stem cells?
The medical profession has used adult stem cells in treatment for many years. Bone marrow transplantation is an effective technique to treat various forms of cancer. Additionally, autologous bone marrow transplantation (in which a person's own bone marrow is removed and then later transplanted) is used after cancer chemotherapy or radiation treatment that might destroy person's bone marrow (Marshak, p. 11). However, with conditions such as Parkinson's disease, spinal cord injuries, diabetes, heart disease, and many others, the problem is that cells are damaged or missing and are not replenished by the adult stem cells of the human body.
For example, an injury spinal cord does not heal itself by regrowing tissue. Therefore, scientists have begun experimenting with ways of manipulating adult stem cells to replace missing cells. Many, though not all, researchers believe that embryonic stem cells have greater potential to form the types of cells that could be useful pin treating diseases and injuries. In nature, embryonic stem cells are much more versatile in the types of cells that they form than are adult cells. Also, isolating adult stem cells can be difficult.
In conclusion, a detailed understanding of stem cells in inflammatory and immune melieu is required for exploring it as an ideal candidate for regenerative therapies. Development of TSFs, based on self-assembling of amphiphiles by biomimetric approaches has immense potential in controlling both the inflammatory and immune interactions. A combination of stem cells with thin film modified surfaces may effectively modulate the inflammatory and immune responses.
