Stem cells are special human cells from which functional cells are generated. Stem cells are called “masters cells” from which “daughter cells” are derived. These daughter cells can become either new stem cells or specialized cells. Specialized cells perform functions like bone cells, muscle cells, body muscle cells, brain cells or blood cells.
These are the various sources of stem cells:
1) Adult Stem Cells – these come from human bone marrows or body fat. 2) Embryonic Stem Cells – these come from embryos that are 3-5 days old.
3) Induced Pluripotent Stem Cells – these are adult stems cells that are altered to possess the properties of embryonic stem cells.
Adult Stem Cells:
Throughout a person’s life, stem cells exist in their body. These stem cells can be used by the body at any time. Adult stem cells, also known as tissue-specific or somatic stem cells, exist throughout the body from the time an embryo develops Although the cells are unspecialized, they are more specialized than embryonic stem cells. They stay in this state until they are required by the body for a specific function, such as skin or muscle cells. The body is continually rebuilding its tissues as we go about our daily lives. Stem cells divide on a regular basis in various regions of the body, such as the gut and bone marrow, to develop new body tissues for the purpose of maintenance and repair.
Stem cells can be found in a variety of tissues. Stem cells have been discovered in a variety of tissues, including:
- the brain
- bone marrow
- blood and blood vessels
- skeletal muscles
- skin
- the liver
Stem cells, however, can be tough to come by. For years, they can remain non-dividing and non-specific until the body calls them to repair or build new tissue. Adult stem cells have an infinite ability to divide or self-renew. This means they can develop a variety of cell types from the original organ or perhaps completely rebuild it.
This division and regeneration is how a skin wound heals, or how a damaged organ, such as the liver, can restore itself. Adult stem cells were previously thought to only be able to differentiate based on their tissue of origin. However, new research reveals that they can also differentiate into distinct cell types.
What’s great about stem cells is that they may be used for a good number of applications. That number continues to grow as medical studies return with promising results. Even now, many of the applications of stem cells are getting more efficient as doctors discover new ways to maximize their benefits.
Embryonic Stem cells:
An embryo is formed from the very beginning of pregnancy, when the sperm fertilizes the egg. The embryo takes the form of a blastocyst, or ball of cells, 3–5 days after a sperm fertilizes an egg. The blastocyst is made up of stem cells that will be implanted in the womb later. Embryonic stem cells are extracted from a 4–5-day-old blastocyst.
Scientists commonly collect stem cells from excess embryos that result from in vitro fertilization (IVF). Doctors at IVF facilities fertilize numerous eggs in a test tube to ensure that at least one of them survives. They’ll then start a pregnancy with a limited quantity of eggs implanted. When a sperm fertilizes an egg, the two cells merge to produce a zygote, which is a single cell.
After then, the single-celled zygote begins to split, generating 2, 4, 8, 16, and so on. It is now an embryo. The blastocyst is a mass of 150–200 cells that forms shortly before the embryo implants in the uterus. The blastocyst is divided into two parts:
- an outer cell mass that becomes part of the placenta
- an inner cell mass that will develop into the human body
Embryonic stem cells are present in the inner cell mass. These cells are known as totipotent cells by scientists. The term totipotent refers to a cell’s entire ability to develop into any other cell in the body.
The cells can be stimulated to produce blood cells, skin cells, and all of the other cell types that the body requires. The blastocyst stage lasts around 5 days in early pregnancy before the embryo implants in the uterus, or womb. Stem cells start to differentiate at this point. Adult stem cells can only differentiate into a few cell types, whereas embryonic stem cells can differentiate into a variety of cell types.
Induced Pluripotent Stem Cells:
Skin cells and other tissue-specific cells are used to make these in the lab. Because these cells act similarly to embryonic stem cells, they may be valuable in the development of a variety of therapies. More research and development are, however, required.
Scientists start by extracting samples from adult tissue or an embryo to produce stem cells. The cells are then placed in a controlled culture where they will divide and proliferate but not specialize further. A stem-cell line is a collection of stem cells that are dividing and replicating in a controlled environment.
For various purposes, researchers manage and disseminate stem-cell lines. They have the ability to induce stem cells to specialize in a specific way. Direct differentiation is the name for this technique. Until today, growing huge numbers of embryonic stem cells was easier than growing big numbers of adult stem cells. Scientists are, however, making progress with both cell types.
The most common application of stem cells is tissue regeneration. Previously, someone in need of a new kidney had to wait for a donor and then undergo a transplant. There is a scarcity of donor organs, but scientists could employ stem cells to generate a certain tissue type or organ by guiding them to develop in a precise way. For example, surgeons have already created new skin tissue using stem cells from just beneath the skin’s surface. They can then graft this tissue onto damaged skin to treat a serious burn or other lesion, and new skin will grow back.
Doctors may one day be able to cure brain illnesses like Parkinson’s and Alzheimer’s using replacement cells and tissues. Damage to brain cells, for example, causes uncontrollable muscle movements in Parkinson’s disease. Scientists may be able to employ stem cells to repair damaged brain tissue. This may help to restore the specialized brain cells that inhibit uncontrollable muscle movements. Treatments are hopeful since researchers have already tried differentiating embryonic stem cells into these sorts of cells.
A team of researchers from Massachusetts General Hospital published a paper in PNAS Early Edition describing how they used human stem cells to build blood arteries in laboratory animals. Within two weeks of the stem cells being implanted, networks of blood arteries had grown. These generated blood arteries were of the same high quality as the native ones in the area. The scientists believed that this technology will one day aid in the treatment of persons suffering from cardiovascular and vascular illnesses.
Adult hematopoietic stem cells are now commonly used to treat disorders including leukemia, sickle cell anemia, and other immunodeficiency issues. Hematopoietic stem cells are found in the blood and bone marrow and can create all blood cell types, including oxygen-carrying red blood cells and disease-fighting white blood cells.
Scientists hope to be able to generate healthy heart cells in the lab and transplant them into people with heart disease one day. By repopulating the heart with healthy tissue, these new cells may be able to mend cardiac damage. People with type I diabetes, meantime, may get pancreatic cells to replace insulin-producing cells that their immune systems have lost or destroyed. The sole current treatment option is a pancreatic transplant, however only a few pancreases are available.
