Research on stem cells has increased significantly in the last decade. With their ability to treat so many different conditions and the promise of treating even more, stem cells are growing in popularity. People want to know what they do, where they come from, and how might they be used in the future.
To gain an understanding of stem cells, we should first understand how they come about. Stem cells actually come from a variety of sources. To date, they are classified under two main types of stem cells, which are adult stem cells and embryonic. However, there are several subcategories as well.
Embryonic Stem Cells
The most controversial stem cells are embryonic stem cells. These cells are derived from human embryos that have been destroyed or harvested following fertilization. The cells from embryos are very useful because they can be used to create pluripotent stem cell lines. This means that cell cultures can be grown indefinitely in a scientific laboratory.
Pluripotent stem cells are able to become practically all the cell types within the human body, which is why they’re often used to create healthy cells for disease patients. Embryonic stem cells are being extensively researched. Scientists are trying to determine if these stem cells can be used to treat or cure Parkinson’s disease, blindness, various cancers, and more.
Umbilical Cord Stem Cells
In the past, umbilical cord stem cells were considered waste and disposed of, but today, they serve a more useful purpose. It turns out that umbilical cords are a useful source of blood stem cells, also known as hematopoietic stem cells. These stem cells can be used to create other types of cells found in the blood, which makes them a great option for treating leukemia or lymphoma.
Cord blood also contains small quantities of another cell type called mesenchymal stem cells. These types of cells come from skeletal tissues, which include bone, fat, and cartilage. Scientists are trying to determine how these stem cells can best be used, but it is particularly difficult to isolate them. It’s challenging to pick them out and identify which ones can self-renew and form into different cell types.
In addition, hematopoietic stem cells seem to have fewer instances of graft-versus-host disease. The latter is a very common condition when doing allogeneic stem cell transplants. To date, they’ve been used to treat a number of blood diseases in children and research is exploring their usefulness in adults as well.
The great thing about cord blood is once it’s collected, it can be stored and frozen to be used later. The blood stem cells can also be found in the placenta. The downside is that adults require two volumes of cord blood for treatment because it contains less hematopoietic stem cells. Scientists are trying to determine how they can create more hematopoietic stem cells from cord blood in labs so that a single cord is enough for multiple transplants.
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Adult (Somatic) Stem Cells
Adult stem cells, also known as somatic stem cells, are taken from a human donor. These cells can be found in tissue throughout the body and are typically harvested via blood draw, tissue fat extraction, and bone marrow extraction. In the past, only bone marrow extraction was done, but research soon discovered that these cells circulate throughout the bloodstream. Once scientists learned how to harvest these cells, peripheral blood stem cell transplants became more common than bone marrow extractions. The procedure is much less invasive and doesn’t require removal of marrow from the hipbone.
Currently, adult stem cells aren’t really used for therapeutic purposes, but research is being done to figure out how they can best be utilized. For one, they’re quite rare. We have to remember that their sole purpose in the body is to replace those cells that die from injury or disease and only so many are made. Secondly, the stem cells have to be used for their organ of origin. For instance neural stem cells can only be made into brain cells. Adult stem cells are considered multi-potent, which means they only make a limited amount of specialized cell types. Because of their rarity, blood stem cells (hematopoietic) are the only type of adult cell used regularly for treatment.
You should also know that adult stem cells could be taken from children. Their name just best differentiates them from embryonic stem cells.
How Can Adult Stem Cells Be Successful At Treatment?
In order for an adult stem cell to be successful, it must have the ability to be reproduced in large enough quantities. There is actually a drug available that can multiply the number of blood stem cells. The drug, PEG, is currently being tested by the Children’s Hospital in patients with lymphoma and leukemia to see if it rebuilds their blood systems.
As previously mentioned, adult stem cells can only be used for an organ or origin. Therefore, the desired cell type must be created either in the laboratory or after they’ve been transplanted.
Lastly, it must be safe. Patients who get adult stem cells are at an increased risk of developing graft-versus-host disease. The donor should have an identical tissue type or the transplanted cells will be rejected. Unfortunately, if they’re manipulated incorrectly, a patient is also at risk of cancer.
Induced Pluripotent Stem Cells
As previously mentioned, adult stem cells are limited in use when it comes to treating and curing disease. As a result, induced pluripotent stem cells were created. Scientists have created a way to completely reprogram adult stem cells so that they can form into other cell types like embryonic stem cells. This process is a lot less controversial and more widely accepted because it doesn’t involve embryos. In addition, they are easier to harvest and more plentiful.
Induced pluripotent stem cells usually begin as skin cells or blood cells before they are reprogrammed. It’s amazing because these cells can create cell lines from an individual’s own cells or tissues, which means fewer complications with donors.
The Future of Stem Cells
As you’ve probably gathered, the future of stem cells is promising. While we certainly still have a ways to go, there is hope that stem cells will be used for much more in the future. Because of advancements in research, notably induced pluripotent stem cells, controversy surrounding the subject is decreasing. In the future, do you think one type of stem cell will be used more than another? Time will certainly tell!