Introduction:
Stem cells are the foundation for every organ and tissue in your body. There are many different types of stem cells that come from different places in the body or are formed at different times in our lives.
Stem cells are a class of undifferentiated cells that are able to differentiate into specialized cell types. Stem cells are distinguished from other cell types by two important characteristics:
- First: they are unspecialized cells capable of renewing themselves through cell division.
- Second: They can differentiate into more specialized cells, like: skin, muscle and blood.
Yet, stem cells vary widely in what they can and cannot do. This is one of the reasons researchers use all types of stem cells in their investigations.
Types of Stems Cells:
- Embryonic stem cells.
- Adult stem cells.
- Mesenchymal Stem Cells.
- Induced pluripotent stem cells.
1- Embryonic stem cells.
Embryonic stem cells are obtained from the inner cell mass of the blastocyst, a mainly hollow ball of cells that, in the human, forms nearly three days after an egg cell is fertilized. These cells are incredibly valuable because they provide a renewable resource for studying normal development and disease, and for testing drugs and other therapies. They are also used to check up blastocysts created by in vitro fertilization (IVF), to have a healthy baby in case parents carry certain genetic illnesses.
However, when scientists extract the inner cell mass and grow these cells in special laboratory conditions, they retain the properties of embryonic stem cells.
2- Adult stem cells (tissue-specific stem cells, somatic stem cell, or non-embryonic stem cells):
They are more specialized than embryonic stem cells (no embryo can develop from these cells). They have the potential to replace lost cells from any tissue. Typically, these stem cells can generate different cell types for the specific tissue or organ in which they live.
For example, blood-forming (or hematopoietic) stem cells in the bone marrow can give rise to red blood cells, white blood cells and platelets. However, blood-forming stem cells don’t generate liver or lung or brain cells, and stem cells in other tissues and organs don’t generate red or white blood cells or platelets.
Some tissues and organs within your body contain small caches of tissue-specific stem cells whose job it is to replace cells from that tissue that are lost in normal day-to-day living or in injury, such as those in your blood.
Tissue-specific stem cells can be difficult to find in the human body, and they don’t seem to self-renew in culture as easily as embryonic stem cells do. However, study of these cells has increased our general knowledge about normal development, what changes in aging, and what happens with disease.
Adult stem cells.
| Embryonic stem cells.
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They can generate different types of specialized cells.
| They can differentiate into various specialized cells.
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Tissue-specific stem cells can be difficult to find and extract. So, no way to grow large quantities of adult stem cells in cell culture so far.
| They Can be grown in cell culture.
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3- Mesenchymal Stem Cells:They are adult stem cells found in bone marrow, which can be isolated from other tissue, including: fallopian tube, umbilical cord, liver...etc. They can treat many other tissues. Scientists are still working on their use to treat bone, cartilage and other diseases.
4- Induced pluripotent stem cells:
While iPS cells share many of the same characteristics of embryonic stem cells, they aren’t exactly the same. They have been engineered in the lab, then re-injected into the same person to avoid rejection by his immune system.
How stem cells are collected?
- Stem cells are collected from the following sources:
- Bone marrow.
- Peripheral stem cells.
- Umbilical cord blood.
1- Bone Marrow Stem Cells:
Collecting bone marrow stem cells:
- It’s done in an operating room, while the donor is under general anesthesia. he marrow cells are taken from the back of the pelvic (hip) bone.
- The amount taken depends on the donor’s weight.
- Often, about 10% of the donor’s marrow are collected. This takes about 1 to 2 hours.
- In most cases, the donor is able to leave the hospital within a few hours or by the next morning. The body will replace these cells within 4 to 6 weeks.
- The donor may have some symptoms for a few days.
- Nonsteroidal anti-inflammatory drugs (such as: aspirin, ibuprofen, or naproxen).
- The donor is back to his usual schedule in 2 to 3 days. But it could take 2 or 3 weeks before he/she feels completely back to normal.
- There are not any risks for donors and serious complications are rare.
What happens to the cells after donation?
Once the cells are collected, they are filtered through fine mesh screens. This prevents bone or fat particles from being given to the recipient. The cells may be given to the recipient through a vein soon after they are harvested. Sometimes they’re frozen for future use.
2- Peripheral stem cells:
Collecting peripheral stem cells:
For several days before starting the donation process, the donor is given a daily injection of filgrastim. This is a growth-factor drug that causes the bone marrow to make and release a lot of stem cells into the blood.
Filgrastim can cause some side effects, the most common being bone pain and headaches. These may be helped by nonsteroidal anti-inflammatory drugs (such as: aspirin, ibuprofen, or naproxen).
Nausea, sleeping problems, mild fevers, and tiredness are other possible effects. These go away once the injections are finished and collection is completed.
The donation procedure takes about 2 to 4 hours and is done as an outpatient procedure. Often the process needs to be repeated daily for a few days, until enough stem cells have been collected.
During the apheresis procedure, the donor may feel lightheaded or tingly, and having chills or muscle cramps. These go away after donation is complete.
Sometimes, a second drug called plerixafor is used along with filgrastim in special cases. The patient should tell the doctor right away if they have any pain in their left shoulder or under their left rib cage.
3- Umbilical cord blood:
Cord blood is the blood that’s left in the placenta and umbilical cord after a baby is born. Collecting it does not pose any health risk to the infant. The cord blood is put into a sterile container, mixed with a preservative, and frozen until needed.
Parents may want to bank their child’s cord blood if the family has a history of diseases that may benefit from stem cell transplant. Other parents choose to donate their infant’s cord blood.
Patient and donor matching:
It is very important that the donor and recipient are a close tissue match to avoid graft rejection. Graft rejection happens when the recipient’s immune system recognizes the donor cells as foreign and tries to destroy them as it would a bacteria or virus, leading to graft failure.
Finding a match:
The search for a donor usually starts with the patient’s parents, then blood brothers and sisters, then half-brothers and sisters, and extended family. Spouses are less likely to be good matches.
If no relatives are found to be a close match, the transplant team will widen the search to the general public.
Stem cells and diseases:
Stem cells: Immunity and blood cancer:
Stem cells are transplanted to replace unproductive or cancerous bone marrow.
Stem cells and metabolic diseases:
Stem cell transplants are used to early treat and repair enzymes deficiencies, or reduce the serious health damages caused thereby.
Stem cells and diabetes:
Efforts still continue to find a way to replace the pancreatic Beta insulin cells, so there is no proven way to treat diabetics. Current research is seeking to replaces damaged cells.
Stem cells and multiple sclerosis (lateral):
There are many interesting studies to find the types of stem cells that inhibits multiple sclerosis and treat nervous system disorders.
Stem cells therapy is not yet proved. Yet, Research is under way to inhibit the immune system from rejecting the myelin and brain tissue.
Stem cells and Cardiac diseases:
Cardiac research seeks to understand heart diseases and their causes, and to find a way to cure and replace heart damaged tissues.
Stem cells and macular degeneration:
While eyes have independent cells, and make a good target for stem cells therapy, research is still in progress to treat macular degeneration.
Frequently asked questions:
Does stem cells therapy ensure a secure permanent or temporary solution?
This question does not have a definite answer so far. Stem cells are transplanted with very low disease recurrence rates. It's proven the best available treatment for certain cases.