Clinical uses of mesenchymal stem cells
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Adult mesenchymal stem cells are being used by researchers in the fields of regenerative medicine and tissue engineering to artificially reconstruct human tissue which has been previously damaged. Mesenchymal stem cells are able to differentiate, or mature from a less specialized cell to a more specialized cell type, to replace damaged tissues in various organs.[1][2][3]
Obtaining mesenchymal stem cells from the bone marrow
In the research process of expanding the therapeutic uses of mesenchymal stem cells, they are grown in laboratories or grown using medication to stimulate new cell growth within the human body. In mesenchymal stem cell therapy, most of the cells are extracted from the adult patient's bone marrow [2][3] Mesenchymal stem cells can be obtained via a procedure called bone marrow aspiration. A needle is inserted into the back of the patients hip bone and cells are removed to be grown under controlled in vitro conditions in a lab. Over a course of two or three weeks, the cells will multiply and differentiate into specialized cells. The number of fully differentiated cells and their phenotype can be influenced in three ways. The first one is by varying the initial seed density in the culture medium. The second is by changing the conditions of the medium. The third is by the addition of additives such as proteins or growth hormones to the culture medium to promote growth. The mature cells are then harvested and injected back into the patient through local delivery or systemic infusion.
Isolation efficiency
Isolation of mesenchymal stem cells from the bone marrow requires an invasive procedure. Mesenchymal stem cells can also be isolated from birth-associated tissues such as the umbilical cord without the need for an invasive surgical procedure. Differences in isolation efficiency are attributed to the availability, condition, and age of the donor tissue. An issue related to culturing mesenchymal stem cells is the insufficient number of cells that can be produced.[1][3] During long-term culture, mesenchymal stem cells age, lose their ability to differentiate, and have a higher chance to undergo malignant transformation.[4][5]
Therapeutic properties
Mesenchymal stem cells possess many properties that are ideal for the treatment of inflammatory and degenerative diseases.[6][7] They can differentiate into many cell types including bone, fat, and muscle which allow them to treat a large range of disorders.[8][9] They possess natural abilities to detect changes in their environment, such as inflammation. They can then induce the release of bioactive agents and the formation of progenitor cells in response to these changes.[9] Mesenchymal stem cells have also been shown to travel to sites of inflammation far from the injection site.[7][10][11]
Mesenchymal stem cells can be easily extracted through well-established procedures such as bone marrow aspiration.[7] Also, transplanted mesenchymal stem cells pose little risk for rejection as they are derived from the patients own tissue, so are genetically identical, however graft versus host disease is a possibility, where the cells change enough while outside the patient's body that the immune system recognizes them as foreign and can attempt to reject them. This can lead to symptoms such as itchiness, sensitive/raw skin and shedding or dry skin. .[6]
Advantages over embryonic stem cells
Several different forms of stem cells have been identified and studied in the field of regenerative medicine. One of the most extensively studied stem cell types are embryonic stem cells, which possess many of the same therapeutic properties as mesenchymal stem cells, including the ability to self-regenerate and differentiate into a number of cell lineages.[8] Their therapeutic abilities have been demonstrated in a number of studies of autoimmunity and neurodegeneration in animal models.[8][7][10][12]
However, their therapeutic potential has been largely limited by several key factors.[7] Injected embryonic stem cells have been shown to increase the risk for tumor formation in the host patient.[8][7][12] Also, the host's immune system may reject injected embryonic stem cells and thus eliminate their therapeutic effects.[7] Finally, research has been largely limited due to the ethical issues that surround their controversial procurement from fertilized embryos.[8][12]