Introduction:
Stem cells are cells that can proliferate and differentiate into numerous types of cells in the body. These are the foundation cells that give rise to all of the body’s cells, tissues, and organs. Stem cells are remarkable in that they can self-renew and produce more stem cells as well as specialized cells like muscle cells, brain cells, and blood cells.
Properties:
Stem cells have several unique properties that distinguish them from other types of cells in the body:
Self-renewal: Self-renewal is the process through which stem cells divide and produce new stem cells. They can keep their population stable for the duration of an organism because to this characteristic.
Differentiation: Stem cells can differentiate into a wide range of cells, including those found in the heart, liver, blood, and brain. Because of their potential to develop into diverse cell types, stem cells are a significant tool for tissue engineering and regenerative medicine.
Potency: Stem cells are classed according to their potency, or capacity to develop into various cell types. Totipotent stem cells have the ability to give rise to all cell types in an organism, including placental cells. Pluripotent stem cells have the ability to differentiate into all cell types in the body except placental cells. Multipotent stem cells can only differentiate into a few distinct cell types.
Plasticity: Some stem cells can develop into cell types that are not normally found in the tissue from which they originated. This characteristic, known as plasticity or trans differentiation, has been discovered in some adult stem cells and is now being studied.
Low immunogenicity: Stem cells have low immunogenicity, which implies they are less likely to stimulate an immunological response or be rejected by the immune system of the recipient. This is due to the fact that stem cells express lower levels of MHC antigens, which are molecules that can trigger an immune response, and they have the ability to regulate and modulate the immune response, producing anti-inflammatory cytokines and growth factors that can reduce inflammation and prevent immune-mediated damage.
History:
The first-time cells were recognized as the fundamental units of all living things was in the middle of the 19th century, which is when stem cell research began. But it wasn’t until the latter half of the 20th century that scientists started to realize how useful stem cells may be for tissue engineering and regenerative medicine.
The earliest proof of stem cells in mouse bone marrow came from Canadian researchers Ernest McCulloch and James till in the 1960s. They demonstrated that these cells could self-renew and specialize into distinct kinds of blood cells.
Researchers made the discovery of embryonic stem cells in the 1980s. These cells can differentiate into any type of cell in the body and are present in early-stage embryos. This finding created new opportunities for regenerative medicine but also brought up moral questions regarding the usage of embryos.
Adult stem cells were found by scientists in the 1990s in a variety of bodily organs, including the skin, liver, and brain. Although having less differentiation capacity than embryonic stem cells, these cells can nevertheless repair damaged tissue.
Since then, scientists have continued to investigate the potential of stem cells to cure a range of illnesses and ailments, including as diabetes, Parkinson’s disease, and heart disease. Before stem cell therapy may be utilized frequently in medical care, however, there is still a great deal of research to be done.
Sources:
Each source of stem cells has its advantages and disadvantages, and the choice of source will depend on the specific application and the availability of cells.
Embryonic stem cells: The inner cell mass of early-stage embryos is where embryonic stem cells are formed. They can differentiate into any type of cell in the body and are hence termed pluripotent.
Fig: Human Embryonic stem cell
Fetal stem cells: Fetal stem cells are found in the tissues of fetuses, including the liver, bone marrow, and blood. They are multipotent and can differentiate into a limited number of cell types.
Umbilical cord blood stem cells: Umbilical cord blood stem cells are a type of stem cell that are found in the blood of the umbilical cord and placenta after a baby is born. These stem cells are considered to be a rich source of hematopoietic stem cells, which can differentiate into various types of blood cells.
Adult stem cells: Adult stem cells, also known as somatic stem cells, are undifferentiated cells present in a variety of tissues and organs throughout the body, including bone marrow, brain, liver, and skin. Adult stem cells are more specialized and have a more limited differentiation potential than embryonic stem cells, which can differentiate into any type of cell in the body.
Adult stem cells are vital in the body’s natural regenerative processes because they can develop into specialized cells that can replace damaged or dying cells in the tissue or organ where they are found. Hematopoietic stem cells in bone marrow, for example, can differentiate into different types of blood cells, whereas neural stem cells in the brain can differentiate into neurons and other types of brain cells.
Fig: Stem cells
Induced pluripotent stem cells (iPSCs): Induced pluripotent stem cells (iPSCs) are a type of stem cell that is created by reprogramming adult cells, such as skin cells or blood cells, to a pluripotent state. This means that, like embryonic stem cells, they can develop into any type of cell in the body.
The discovery of iPSCs has transformed the area of regenerative medicine since they provide a non-embryonic source of pluripotent stem cells. This also indicates that iPSCs can be created from the patient’s own cells, lowering the danger of immunological rejection in therapeutic applications.
Stem Cells Vary in their Developmental capacity:
Stem cells vary in their developmental capacity or potency, which refers to their ability to differentiate into different cell types. There are three main types of potency:
Totipotent stem cells: Totipotent stem cells are the first type of stem cell that develop after a sperm fertilizes an egg. These cells have the extraordinary potential to develop into any type of cell in the body, including embryonic and extra-embryonic organs like the placenta. Totipotent stem cells can give rise to all of the cell types required to make a complete organism, including germ cells required for reproduction. The totipotent stem cells differentiate into pluripotent stem cells as the embryo develops, which can give rise to all cell types in the body except extra-embryonic tissues.
Pluripotent stem cells: Pluripotent stem cells are stem cells that can differentiate into basically any form of cell in the body. They can generate cells from the embryo’s three germ layers: endoderm, mesoderm, and ectoderm. These germ layers eventually give rise to all of the body’s specialized cell types, including blood cells, brain cells, and muscle cells.
Fig: Pluripotent stem cells
Multipotent stem cells: Multipotent stem cells are a type of stem cell that can differentiate into a variety of cell types, but only a few of them. In contrast to pluripotent stem cells, which can differentiate into practically every cell type in the body, multipotent stem cells have a more limited differentiation potential and can only differentiate into certain types of cells within a given tissue or organ.
Hematopoietic stem cells, which are found in bone marrow and give rise to all blood cell types, and mesenchymal stem cells, which are found in various tissues such as bone marrow, adipose tissue, and umbilical cord tissue and can differentiate into bone, cartilage, and fat cells, are examples of multipotent stem cells.
Biology of Stem cells:
After sperm and ovum fertilization, a blastocyst is produced. Its inner wall is lined with embryonic stem cells, which are short-lived stem cells. Blastocysts are made up of two types of cells: the inner cell mass (ICM), which develops into epiblasts and induces fetal development, and the trophectoderm (TE). Blastocysts are in the position to control the ICM microenvironment. The TE continues to develop and develops the extraembryonic support structures required for embryonic development, such as the placenta.
The ICM cells remain undifferentiated, fully pluripotent, and proliferative as the TE begins to create a specialized support structure. Because stem cells are pluripotent, they can become any cell in the organism. The ICM gives rise to human embryonic stem cells (hESCs). During the embryogenesis process, cells form aggregations known as germ layers, which eventually give rise to differentiated cells and tissues of the fetus and, later, the adult organism.
Source: https://doi.org/10.1186/s13287-019-1165-5
As hESCs develop into one of the germ layers, they become multipotent stem cells whose potency is restricted to the germ layer cells exclusively. This stage of human development is brief. Following that, pluripotent stem cells appear as undifferentiated cells throughout the organism, and their major capacities are proliferation by the production of the next generation of stem cells and differentiation into specialized cells under certain physiological conditions.
Stem cells culture:
The process of producing and maintaining stem cells in the laboratory using particular techniques and media that promote their growth and proliferation is referred to as stem cell culture. Stem cells of several sorts can be grown, including embryonic stem cells, induced pluripotent stem cells, and adult stem cells.
Isolating stem cells from their source tissue, such as bone marrow or umbilical cord blood, and then transferring them into a culture dish containing nutrient-rich media that mimics the environment of the stem cell’s natural niche in the body, is the normal technique of stem cell culture.
To support the growth and survival of the stem cells, the culture dish is normally kept in a controlled environment with optimal temperature, humidity, and oxygen levels. Researchers can then trace the stem cells’ proliferation and differentiation over time using various markers and assays to confirm their purity and identity.
Stem cell culture has numerous uses in research, drug development, and regenerative medicine. Researchers can study stem cells’ features, test possible cures, and develop cell-based therapeutics for a variety of diseases and disorders by cultivating and manipulating them in the lab.
Regenerative Medicine:
Regenerative medicine is a branch of medicine concerned with the development of new treatments to repair, replace, or regenerate damaged or diseased tissues and organs. It entails using stem cells, biomaterials, and other cutting-edge therapies to stimulate the body’s own healing mechanisms and restore normal function.
Regenerative medicine has the potential to completely transform the treatment of many diseases and conditions, including cardiovascular disease, neurological disorders, diabetes, and cancer. While the discipline is still in its early stages, major discoveries in stem cell research and tissue engineering have already been made, and clinical trials to evaluate the safety and effectiveness of numerous regenerative medicine therapies are currently underway.
Stem cell Therapy:
Stem cell therapy is a type of regenerative medicine that uses inflammation and immune modulation to repair damaged cells within the body. Because of this phenomenon, stem cell therapy has become a feasible treatment option for a variety of medical diseases. Stem cell therapies have been utilized to treat autoimmune, inflammatory, neurological, orthopedic, and traumatic injuries, with research being undertaken on the usage for Crohn’s disease, Multiple Sclerosis, Lupus, COPD, leukemia, lymphoma, sickle cell anemia, cystic fibrosis, Parkinson’s, ALS (Amyotrophic lateral sclerosis), stroke recovery, and other illnesses.
Amniotic fluid stem cell treatment and umbilical cord-derived stem cell treatment are two forms of stem cell treatments available. Hematopoietic stem cell transplantation, which cures blood malignancies such as leukemia, is the most common FDA-approved stem cell-based therapy. Stem cells can also be used to treat severe skin burns and severely damaged corneas.
Fig: ESC-based Cell Therapy
Applications:
Fig: Applications of Stem cells
Stem cells banks:
Stem cell banks, also known as cord blood banks, collect and store umbilical cord blood and tissue for future medicinal use. Cord blood includes stem cells, which can be utilized to treat a wide range of medical diseases, including cancer, blood disorders, and immune system issues.
Cord blood is the blood that remains inside your baby’s umbilical cord after birth. It contains red and white blood cells, platelets, and plasma, much like regular blood. It also contains a type of stem cell found in bone marrow that can aid in immune system strengthening. These cells are distinct in that they can develop or grow into several types of blood cells. They are valuable because of their potential to transform into different cells.
Ethics and moral values:
Because it includes the use of human embryos and fetuses, stem cell research and therapy raise ethical and moral difficulties. The debate over the use of stem cells stems from the possible destruction of a human life, as some individuals regard the embryo or fetus as a human being with the right to life. Some, on the other hand, claim that embryonic stem cell research has the potential to produce life-saving cures for critical medical illnesses, and thus the potential advantages outweigh the moral issues.
Stem cell research and therapy raise complicated ethical and moral concerns that must be carefully considered and debated. While it has the potential to produce life-saving therapies for major medical illnesses, it is critical to ensure that the research is carried out in an ethical and transparent manner, and that the benefits are distributed equally to all.
References:
- Kimbrel, E.A., Lanza, R. Next-generation stem cells — ushering in a new era of cell-based therapies. Nat Rev Drug Discov 19, 463–479 (2020).
- Zakrzewski, W., Dobrzyński, M., Szymonowicz, M. et al. Stem cells: past, present, and future. Stem Cell Res Ther 10, 68 (2019).
- Harris DT. Stem Cell Banking for Regenerative and Personalized Medicine. Biomedicines. 2014 Feb 26;2(1):50-79.