What are stem cells?
Stem cells are often referred to as the 'building blocks of life' as they build, repair and regenerate the tissues of the human body. An adult human has about 100 trillion individual body cells, which can be divided into 200 different cell types. They all come from a single stem cell - the fertilized egg. It is a miracle of nature that a new living being develops from it in just 40 weeks of pregnancy.
Stem cells have 2 main characteristics(1)
- Self-renewal (creation of new identical cells) and
- Differentiation (creation of new more specialized cells)
The main classification of stem cells according to their age potential is in three categories(2)
- Early embryonic stem cells (totipotent: differentiate into cells of all tissues)
- Embryonic stem cells (pluripotent: differentiate into cells of almost all tissues) and
- Neonatal - adult stem cells (multipotent: they differentiate into cells of some specific tissues)
Neonatal stem cells comprising both of hematopoietic and umbilical cord mesenchymal stem cells retain the aforementioned self-renewal and differentiation characteristics. However, their most important advantage compared to adult stem cells is that they are not burdened by environmental effects, diseases, chemicals mutagenic substances that act cumulatively and negatively over time and multiply rapidly. Their ability to produce cells that can form other types of tissues is significantly limited compared to embryonic cells.(1)
Citations
1. Zakrzewski, W., Dobrzyński, M., Szymonowicz, M. et al. Stem cells: past, present, and future. Stem Cell Res Ther 10, 68 (2019).
2. cellpedia.org/en/stem-cells/
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Hematopoietic Stem Cells (HSC)
What is umbilical cord blood?
Umbilical cord blood is the blood that circulates between the mother and the fetus through the placenta and umbilical cord. At birth, the blood that remains in the umbilical cord and placenta is rich in stem cells.
What are hematopoietic stem cells?
More specifically, cord blood is rich in neonatal hematopoietic stem cells, which are the source of production of all types of cells of our hematopoietic and immune systems.
During adult life, hematopoietic stem cells are mainly found in the peripheral blood and bone marrow. However, the hematopoietic stem cells of the umbilical cord are superior to the adult stem cells of the bone marrow because:
- They are isolated risk free.
- They are of better quality as they have not been subjected to environmental and aging effects.
- They are a perfectly compatible graft for the child itself while they have a higher probability of successful transplantation in siblings and relatives because they have a lower risk of developing graft-versus-host disease (GVHD) than bone marrow cells.
This significant difference is due to the fact that they have fewer histocompatibility antigens on their surface(3).
Citations
3. Optimal stem cell source for allogeneic stem cell transplantation for hematological malignancies, D. Cheuk, Published 24 December 2013. World journal of transplantation
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Mesenchymal Stem Cells (MSC)
What are mesenchymal cells?
Mesenchymal stem cells have the ability to give rise to the precursors of differentiated / specialized cells. These cells have gathered the intense interest of the scientific world due to multiple successful applications in pre-clinical and clinical studies and are the new hope in the field of regenerative medicine & tissue engineering. Clinical studies and tests have shown that these cells have several applications in regenerative medicine and in the future even more, such as for example:
- Restoration and regeneration of skin, bones, cartilage and ligaments
- Repair and regeneration of nerve tissue, heart tissue and blood vessels
- Assist in Cases of inflammation and autoimmune diseases
The number of clinical trials with mesenchymal cells has grown exponentially in recent years(4). By 2012 there were 220 registered clinical trials involving mesenchymal stem cells at clinicaltrials.gov while by June 2020 they had increased to 1138 based on publication(5). Coming to today one can find that the number of clinical trials has reached 1430(6).
In what tissues are mesenchymal stem cells found in the human body?
Bone marrow, liver, dental pulp, hair follicles, adipose tissue, umbilical cord, amniotic fluid, placenta and lung are reported in the literature.
The most suitable tissue for the isolation of mesenchymal stem cells of neonatal origin is the mucous connective tissue that surrounds / protects the blood vessels of the umbilical cord. This part of the umbilical cord is called Wharton's jelly and its' cells are superior to mesenchymal cells of adult origin (e.g. bone marrow) as the first show minimal genetic and age-related deterioration and significantly greater regenerative capacity.
Citations
4. David E Rodríguez-Fuentes 1, Luis E Fernández-Garza 2, John A Samia-Meza 1, Silvia A Barrera-Barrera 3, Arnold I Caplan 4, Hugo A Barrera-Saldaña 5, Mesenchymal Stem Cells Current Clinical Applications: A Systematic Review, Arch Med Res. 2021 Jan;52(1):93-101. doi: 10.1016/j.arcmed.2020.08.006. Epub 2020 Sep 22
5. Mesenchymal Stem Cells Current Clinical Applications: A Systematic Review, David E Rodríguez-Fuentes 1, Luis E Fernández-Garza 2, John A Samia-Meza 1, Silvia A Barrera-Barrera 3, Arnold I Caplan 4, Hugo A Barrera-Saldaña 5, Arch Med Res. 2021 Jan;52(1):93-101. doi: 10.1016/j.arcmed.2020.08.006. Epub 2020 Sep 22
6. Search of: mesenchymal Stem cells - Results on Map - ClinicalTrials.gov
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Types of Cord Blood Banks
SIMILARITIES
The operating criteria of public and private banks are common regarding
the organization, management, personnel, infrastructure and equipment used in the preparation, processing and storage of tissues and cells, and laboratory testing.
Also, when comparing the most significant operation points , one finds that both private and public banks are obliged to have a Hematologist, with a minimum of 5 years of experience in transplants, as Medical Director.
The minimum volume of each unit of umbilical cord blood before processing is common in private and public banks.
Finally, cord blood processing in both types of banks must be limited in reducing the volume of the original sample by removing plasma and red blood cells.
DIFFERENCES
In public cord blood banks, parents donate hematopoietic cells from their child's umbilical cord blood free of charge. In this case, there is no claim or right over the sample from the donor after the donation. These cells, if they meet certain quantitative and qualitative criteria, can be transplanted into a histocompatible fellow human (heterologous transplantation).
Donation is therefore a noteworthy an altruistic act. In case a patient needs a transplant- even someone who has donated cord blood stem cells in a public bank - he or she will have to wait to find a compatible donor from a global pool. Also, the storage service of mesenchymal stem cells from umbilical cord tissue offered by some public banks has a fee.
In private stem cell banks, parents store their child's blood (hematopoietic cells) and umbilical cord tissue (mesenchymal cells) for possible use by the child (autologous transplant) or by a family member. The sample belongs to the parents (until the child reaches adulthood). Also, the sample itself is fully histocompatible with the child. These two services are offered either separately or in combination, increasing the chances of a successful transplant if one is needed.
(Fig. 1. Differences – Similarities of Cord Blood Banks, published with permission from Dr Francis Verter, PhD)
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