Tag Archives: cells

Exosomes and Stem Cells Are the Future of Anti-Aging – NewBeauty Magazine

Posted: March 28, 2024 at 2:39 am

Exosomes and Stem Cells Are the Future of Anti-Aging NewBeauty Magazine

Read this article:
Exosomes and Stem Cells Are the Future of Anti-Aging - NewBeauty Magazine

Posted in Stem Cells | Comments Off

Biology of stem cells: an overview – PMC – National Center for …

Posted: March 19, 2024 at 2:38 am

Kidney Int Suppl (2011). 2011 Sep; 1(3): 6367.

1Department of Genetics, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil

2Postgraduation Program in Genetic and Molecular Diagnosis, Universidade Luterana do Brasil, Canoas, Brazil

1Department of Genetics, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil

2Postgraduation Program in Genetic and Molecular Diagnosis, Universidade Luterana do Brasil, Canoas, Brazil

Stem cells are defined as precursor cells that have the capacity to self-renew and to generate multiple mature cell types. Only after collecting and culturing tissues is it possible to classify cells according to this operational concept. This difficulty in identifying stem cells in situ, without any manipulation, limits the understanding of their true nature. This review aims at presenting, to health professionals interested in this area, an overview on the biology of embryonic and adult stem cells, and their therapeutic potential.

Keywords: adult stem cells, biological characteristics, cell therapy, embryonic stem cells, human diseases

Although the initial concept of stem cells is more than 100 years old,1 and much of its biology and therapeutic potential has been explored in the past three decades, we still know little about their true nature. This review is intended to provide an overview on the biology of stem cells and their therapeutic potential to those interested in this field.

Stem cells are operationally defined as cells that have the potential for unlimited or prolonged self-renewal, as well as the ability to give rise to at least one type of mature, differentiated cells.2, 3 Although this basic definition of stemness' applies generally to stem cells, it is necessary to individually consider embryonic and adult stem cells as they do not share much more than the name and the basic definition above.

In humans, the embryo is defined as the organism from the time of implantation in the uterus until the end of the second month of gestation. Embryonic stem cells (ESCs), however, refer to a much more restricted period, resulting from the isolation and cultivation of cells from the blastocyst, which forms at approximately 5 days after fertilization.4

The zygote, which is the cell resulting from the fertilization of an oocyte by a spermatozoon, is totipotent. Several successive cell divisions generate the morula, with 3264 totipotent cells. After that stage, it develops into the blastocyst, which consists of a hollow ball of cells. Peripheral cells (the trophoblast) of the blastocyst generate the embryonic membranes and placenta, whereas the inner cell mass develops into the fetus. These are the cells that are used to establish stem cell cultures (). They are not totipotent, as they do not have the ability to support the formation of another embryo, and are considered to be pluripotent as they can produce all the cell types of the adult organism. Further development of the embryo leads to the formation of the gastrula, composed of the three germ layers (ectoderm, mesoderm, and endoderm), from which the complete organism develops.

Embryonic stem cell cultivation. The zygote undergoes successive mitotic divisions until a sphere of cellsthe blastocystis formed. In the blastocyst, the trophoblast at its periphery generates the embryonic membranes and placenta, whereas the inner cell mass develops into the fetus. Embryonic stem cells are immortal in culture, having been established from one pluripotent cell collected from the inner cell mass. These are capable of differentiating into any of the mature cell types present in the adult organism.

In 1981, two groups established the first ESC lines from mouse blastocysts, and in 1998 the first human ESC line was generated.5 Although seemingly simple, the procedure is technically demanding because of the need for strictly controlled conditions necessary for the maintenance of the cells in the undifferentiated state. This is particularly important for human ESCs.6 Once established, ESC lines may be maintained in permanent culture, frozen and thawed, and transported between laboratories. It is estimated that there are currently around 250 human ESC lines in the world, widely shared among different groups. The process of establishing an ESC line requires, however, the destruction of the blastocyst, raising ethical issues as scientific investigation alone is not capable of determining whether blastocysts constitute human beings. An alternative method involves the production of ESCs by collection of only one cell from the inner cell mass, allowing implantation of the remaining cells in the womb. However, ethical considerations still remain as it has to be tested whether the remaining cells can develop into a normal human being.

Cultured ESCs show defined characteristics: they are pluripotent, capable of differentiating into cells derived from all three germ layers; they are immortal in culture and may be maintained for several hundred passages in the undifferentiated state; and they maintain a normal chromosomal composition.

Molecular characterization of ESCs is well developed, and they are known to express surface markers such as CD9, CD24, and alkaline phosphatase, and several genes involved with pluripotency, including Oct-4, Rex-1, SOX-2, Nanog, LIN28, Thy-1, and SSEA-3 and -4.7 Expression of high levels of telomerase explains their immortality in culture.

ESC research focuses mainly on two issues, both of which have shown significant progress in the past few years.6 The first point explores how to better maintain the cells in long-term culture, without significant modifications of their genetic composition and, in the case of human ESCs, avoiding the need for animal products in the culture. Generally, the cells are maintained in culture on feeder cells such as mouse fibroblasts. The second point focuses on how to differentiate the cells into the many mature cell types that are necessary for the potential treatment of different diseases. ESCs can be induced to differentiate into various cell types in suspension culture, resulting in three-dimensional cell aggregates called embryoid bodies. This tendency of ESCs to differentiate spontaneously may not always be desirable. A technical challenge is to control the differentiation process: although the addition of growth factors directs the differentiation process, usually the cultures spontaneously differentiate into various cell types. It is thus necessary to use methods that allow removal of undifferentiated ESCs from cultures in which the differentiated cell types are the desired product.

Recently, methods for direct reprogramming of adult cells to induced pluripotent stem cells have been developed.8 In the process, mature cells from the patient are treated in vitro with genes that dedifferentiate' them to a pluripotent stage, similar to an ESC (). Induced pluripotent stem cells are believed to be identical to natural pluripotent ESCs in many respects, including the expression of specific genes and proteins, chromatin methylation patterns, culture kinetics, in vitro differentiation patterns, and teratoma formation. Besides avoiding the ethical issues associated with the destruction of human embryos, this approach allows the generation of patient-specific cells of any lineage. Problems related to the genetic modification of target cells, however, must still be resolved before induced pluripotent stem cells may be clinically tested.

Production of induced pluripotent stem (iPS) cells. iPS cells are produced by treating mature cells, such as fibroblasts, with genes that dedifferentiate' them to a pluripotent stage, similar to an embryonic stem cell. Viral vectors, such as retroviruses, are generally used for gene transfer. The transformed cells become morphologically and biochemically similar to pluripotent stem cells, with the advantage of representing autologous cells in therapeutic applications.

The principal advantage of ESCs over adult stem cells is related to their pluripotency and limitless expansion in culture, as they have the potential to give rise to all cell types composing the adult organism. This potential is exploited in vitro to develop specialized cells that are then used in therapy.

Owing mainly to safety issues, the clinical use of hESCs is much more restricted than that of adult stem cells. As proof of pluripotency, ESC lineages injected into immunodeficient mice must lead to teratoma formation, with derivatives of all three germ layers. Only differentiated cells derived from ESCs may be administered to patients, as any contaminating undifferentiated cells could give rise to cancer. The first clinical trial using human ESC-derived cells, which in this case are oligodendrocyte progenitor cells, was started in October 2010. Care must be taken, however, to not call this procedure human ESC therapy', as the cells to be used are no longer ESCs.

See the original post here:
Biology of stem cells: an overview - PMC - National Center for ...

Posted in Stem Cells | Comments Off

What are Stem Cells? – Types, Applications and Sources – BYJU’S

Posted: March 19, 2024 at 2:38 am

Stem cells are special human cells that can develop into many different types of cells, from muscle cells to brain cells.

Stem cells also have the ability to repair damaged cells. These cells have strong healing power. They can evolve into any type of cell.

Research on stem cells is going on, and it is believed that stem cell therapies can cure ailments like paralysis and Alzheimers as well. Let us have a detailed look at stem cells, their types and their functions.

Stem Cell – The Definitive Guide | Biology Dictionary

Posted: March 19, 2024 at 2:38 am

Definition

A stem cell, found in embryos (embryonic stem cell) and adults (somatic stem cell), is an immature, non-specialized cell that can differentiate into one or more specific functioning or regenerating cell types. This makes them of use in the treatment of degenerating diseases. A totipotent stem cell can become any cell type within the organism in which it is found; a pluripotent cell can become any of a wide range of cell types; a unipotent cell is restricted to one cell type.

A stem cell is an early form of cell that has the power to become a specialized cell. The first totipotent stem cell in mammals is the zygote formed after the sperm has fertilized the egg. Every cell in the body is produced from this one cell.

While some textbooks say that cancer cells can be totipotent, this is not the case. A totipotent cell must be capable of developing into a complete organism and its supporting tissues through division. Some cancer cells can differentiate into other tissues, but they are not totipotent. Once a stem cell (SC) differentiates into a cell that is unable to become every cell type both in the organism and in the mother (as a placenta-forming cell), it is no longer totipotent but pluripotent.

SCs can be totipotent (the zygote and the zygotes first stages of division into blastomeres), pluripotent, multipotent, oligopotent, or unipotent. It does not have any function except to produce cell forms that differ from its own structure. Its sole role is to differentiate. How many cell types a stem cell can differentiate into is decided according to its potency level. The controlling mechanism of where and when this cell divides to become another cell type is found in the DNA.

Stem cell types are categorized according to potency level. The higher the stem cell potency level, the higher the range of differentiation. Somatic (adult) SCs are found in all adult and fetal tissues; they replace damaged cells within that tissue and are not totipotent.

The totipotent embryonic stem cell can differentiate into all cell types and also form placental tissue inside the mother. The first eight cells of a single fertilized egg (zygote) are totipotent. After the first round of cell division, the zygote becomes two identical blastomeres; in the second round, the two blastomeres become four blastomeres; in the third cycle of division, eight blastomeres are produced. Only up to this point is the SC totipotent. Should a single blastomere become separated from the group at this very early stage, identical twins are the result. If two blastomeres separate from the main group, identical triplets can develop.

As each totipotent cell division called cleavage at this early stage takes between twelve to twenty-four hours, totipotent embryonic stem cells can only be extracted between one and a half and three days after fertilization.

A pluripotent stem cell can differentiate into any adult cell type but not into placental tissue. Once eight blastomeres have formed, the first round of differentiation occurs to form an outer trophoblast and inner embryoblast. If an entire group of early differentiated pluripotent cells become separated at this point, it is unlikely an embryo will develop. The trophoblast layer becomes the placenta and the embryoblast the embryo.

Embryoblast cells differentiate into any of the cells of the ectoderm, mesoderm, and endoderm of an embryo.

Most of the SCs used in research today are pluripotent embryonic cells. Ethical issues exist as, for large groups of the population, life begins at conception.

Induced pluripotent stem cells (iPSCs) are produced in the laboratory. These are somatic cells engineered to behave like embryonic ones. At present, their use is limited to research but they do mean fewer ethical issues. An adult can opt to donate his or her stem cells to international banks that may or may not match recipients from all over the globe.

A multipotent stem cell is an adult cell. This does not mean it is only found in adults a fetus of approximately ten weeks is composed of multipotent adult SCs. Division produces one specialized daughter cell and one undifferentiated (stem) daughter cell. Examples of multipotent cells are:

It is possible to extract SCs from the umbilical cord during birth. Cord blood stem cells produce blood and mesenchymal cells. As umbilical stem cells have a higher level of potency than other multipotent SCs with fewer specific features, they produce a lower immune response when inserted into another organism of the same species.

The oligopotent stem cell only differentiates into a small group of related cell types. Lymphoid and myeloid stem cells, and corneal squamous epithelium SCs continuously renew the short-lived cells of their specific tissues.

The unipotent SC produces a single cell type to regenerate populations. Nearly all of the bodys cells are unipotent; the difference between a normal cell and a stem cell is this renewing ability. Unipotent progenitor cells allow the regeneration of cells with a short lifespan; examples of unipotent progenitors are muscle stem cells and epidermal stem cells.

When an SC is damaged and cannot differentiate, or when a differentiated stem cell does not divide (as with red blood cells), it becomes a nullipotent stem cell.

A good example is the process of skin burn repair. When skin is sunburned, the top (dead) layers of skin are damaged; new cells produced by unipotent basal skin stem cells eventually replace them. When a burn is deep and the basal cells are damaged, they can no longer divide or differentiate; they have been damaged to the extent that they are nullipotent.

Instead, the SCs of the underlying connective tissue differentiate and form a scar that is not skin. Skin grafts from healthy tissue placed onto a deep burn reduce scarring because they introduce undamaged basal SCs to unhealthy tissue.

Stem cell structure depends on the potency level. A totipotent cell has the structure of a zygote or a blastomere. A unipotent cell will more closely resemble the cell it differentiates into.

Most SCs are round with prominent nucleoli and a high nucleus to cytoplasm ratio (a large nucleus). They contain the same organelles as other cells rough and smooth endoplasmic reticulum, Golgi apparatus, mitochondria, lysosomes, centrosomes, and centrioles.

In laboratories, embryonic SCs reproduce for indefinite periods and are referred to as immortal cells. The word immortal has led many people to believe that these treatments can halt the aging process. This is not at least not yet true.

Propagated cells can theoretically be engineered to differentiate in vivo (in a living organism) or in vitro (outside a living organism) to form any of the two hundred and twenty adult human cell types.

Cells produced in the laboratory are much less likely to be rejected by the bodies of non-related subjects. Stem cell treatment, therefore, is considered to be the future of organ transplant and tissue renewal therapies.

Stem cell research does not only concern the replacement or repair of damaged or aging tissue. It also includes looking into the signals that influence differentiation. External or environmental factors, cell signaling, and genetic control of stem cell specialization processes help us to understand how the body heals itself and regulates tissue renewal.

Even so, stem cell technologies are still in very early stages. We must first understand the exact processes that turn a totipotent cell into a liver cell, for example, before a stem cell therapy can be developed for liver damage. If this process is not exactly understood, any one of thousands of variables could cause SC injections to differentiate into undesired tissue types. Even the nutritional gel of a laboratory culture could affect which daughter cells are produced.

Low immunity in combination with human embryonic SC transplant has been known to lead to teratoma formation. One study showed how the human stem cell injected into immune-compromised mice caused human tissue teratoma growth. Naturally-formed teratomas first gave scientists the idea of the existence of pluripotent cells in the 1950s.

Stem cell therapy is still undergoing clinical trials in a small selection of diseases, not always with the best results. The treatment of blindness caused by macular degeneration with stem cell injection seems to help some visually-impaired patients but certainly not all. Ones own SCs are increasingly being used to grow tissue that, once large enough, can be transplanted without rejection risk. Tracheal transplants, for example, have been performed using SC-generated implants.

In 2020, the Food and Drug Administration reported: Currently, the only stem cell products that are FDA-approved for use in the United States consist of blood-forming stem cells.

Since then, this list has grown as more clinical research achieves results. Approved treatments now include:

Unfortunately, many clinics offer approved stem cell treatments that are yet to be either proven or approved. Certainly, our lack of knowledge regarding when, how, and into what an SC differentiates should make us wait until more clinical studies and research have been performed.

Stem cell hair transplants are offered all over the world and often advertised as FDA-approved therapies this is very far from the case. The risk of teratoma and even neoplasm (benign or malignant tumor) development when internal or external environments change the course of SC differentiation is a possibility that should not be ignored.

We still have decades of research before SC therapy gets anywhere near the initial, hopeful reports that filled newspapers at the beginning of this century. While studies must deal with a huge number of variables, it is expected that stem cell therapy will become a future first-line treatment for degenerative and immune disorders.

Show/Hide

See the rest here:
Stem Cell - The Definitive Guide | Biology Dictionary

Posted in Stem Cells | Comments Off

Cell Therapy Basics

Posted: February 21, 2024 at 2:35 am

Getting to Know Cells

Cells make up every living thing. Inside of each cell are genetic instructions which determine what cell type it will be, and how the cell will behave. All individuals begin with a pool of cells that are the foundation cells for every organ and tissue in the body. These cells are called stem cells which are immature cells that will divide into many different types of mature, specialized cells depending on what the body needs this is called differentiation. During this process, a set of genes in the DNA of each cell are turned on or off to determine what type of cell it will turn into and what type of proteins it will create to help the body function. For example, a stem cell may be instructed, directly or indirectly, by the genes to travel to an area of the body for muscle contraction. These will become muscle cells and continue to divide and play a role in contracting ones muscles for movement. Once a stem cell becomes a mature cell, it will stay that cell type. Throughout one's life, stem cells turn into mature cells, but certain parts of the body will keep their own supply of stem cells, such as in our bone marrow.

The processes of cell growth, division, and differentiation can be complex. When cells grow old or become damaged, they usually die, and new cells get created to divide and to take their place. However, there are times when the body is not able to recognize a cell change, and a damaged cell continues to replicate with changed DNA. A change in the DNA changes how our cells function because it affects how the proteins in our body are built. These changes can be inherited, can happen as we age, or can be caused by environmental factors.

Many human diseases are caused by our cells not functioning properly. For example, in some types of cancer, specific cells in the body get stuck somewhere along the long path of differentiation, creating a shortage of the cell type they had intended to make. The body then tries to compensate for this shortage by having these potentially damaged cells divide many times to fill the gap. This adds to the problem by filling up the tissue with non-functional cells that will take over the normal healthy cells to survive.

Cell therapy is the transfer of a specific cell type, or types, into a person to treat or prevent a disease. Many cell types have the potential to be modified and used as a therapy. Common disorders treated with cellular therapies include cancers of the blood and bone marrow, cancers of the lymphatic system, plasma cell disorders, and other conditions that affect the bodys ability to make healthy cells.

The source of the cells used for cell therapy come from one of two places:

Autologous cell therapy means the cells are collected from the individual's own body. The cells are removed, modified outside the body, then the processed cells are returned to the body. Using the person's own cells makes it less likely to cause immune responses compared to the use of donor cells but will not always be a viable option. A helpful tip to remember is that auto means self.

Allogeneic cell therapy means the cells used are from someone other than the patient, such as a healthy and compatible (or matched) donor. A helpful tip to remember this is that allo means other.

Prior to receiving a cell therapy, an individual may need to follow a pretreatment called conditioning to decrease the immune system's activity for better odds of a successful treatment. Conditioning is often a chemotherapy, which can be extremely hard on the body. It is important that all aspects of the treatment process be thoroughly explained by a healthcare professional to ensure it is well understood by the patient.

Gene modified cell therapy (or ex vivo gene therapy) is a combination of both gene and cell therapy. It first removes a persons own cells from the body. Certain cell types are then treated by either adding a working copy of the gene or modifying/editing the affected nonfunctional gene. Ideally, the body will continue to produce mature cells with the modification when administered back to the individual. CART-cell therapy is just one example of this, but other approved treatments include cells that are modified with lentivirus for disorders such as server combined immunodeficiency (SCID), and metachromatic leukodystrophy (MLD).

Learn more about gene therapy basics and various gene and cell therapy approaches.

The type of cells used for cell therapy depends on the disease being treated and the intended effect on the individual receiving treatment. Here are few commonly used types:

Hematopoietic (blood forming) stem cells also known as HSCs are versatile cells that can turn into any type of blood cell the body needs and can be retrieved from the peripheral blood, from the bone marrow or from umbilical cord blood. Treatments using these cells aim to establish healthy blood cell production in individuals whose blood cells or immune cells are not working properly. A hematopoietic stem cell transplantation (HSCT), sometimes known as a bone marrow transplant (BMT), is used to treat various blood cancers and other blood disorders. HSCs are usually from a donor (allogeneic), but in some cases may use cells collected from the persons own body (autologous).

Cells of the immune system are used because they can recognize and kill cancer cells. One type of cell therapy, called CAR T-cell therapy, modifies the individual's immune cells called T-cells by adding receptors to them. When these modified cells are delivered back to the patient, they recognize, and kill cancer cells. CAR-T typically uses a persons own cells (autologous) but in some cases, may utilize cells collected from a donor (allogenic).

Learn more about blood disorders and this treatment process in CAR T Basics.

Mesenchymal stem cells, most commonly found in bone marrow and fat, are the most versatile and can help the body heal in different ways depending on what is being targeted. They can act like stem cells and become the same type of cell as those in the surrounding area or act like a delivery system to bring medicine to the area in need.

Hope for life-limiting disease.Cell and gene therapy can help treat diseases that have limited treatment options. Without treatment many of these inherited disorders would end in severe disability or premature death. In early studies cell and gene therapy have been shown to help slow or completely stop these disorders. Cell and gene therapies make it possible to design treatments that can target any of the thousands of genes in the body.

Matched donors. Similar to human organ transplants, immune barriers exist that require the person donating the HSC and person receiving the HSC to be carefully matched to avoid life-threatening complications arising from immune system not matching. Many individuals may never find someone who is a match due to lack of recruitment, diversity, and availability.

Accuracy required.Cell and genetherapies need to ensure modified cells go to the right tissue, at the right level, for the right amount of time. This means that a lot of research goes intothe best waytodeliver the cellular material.

Immune suppression. Chemotherapy and other conditioning regimens are often administered prior to cell therapy to prevent an immune response. The medications used to suppress an individuals immune system can increase their risk for infections and can be quite hard on the body.

Informed consent. Before participating in a clinical trial or receiving a cell therapy treatment, a member of the research team should review any potential risks and benefits with the individual and/or caregiver. It is important that individuals participating in a clinical trial understand their rights during the research process and know what to expect.

Immune responses. Graft-versus-host disease (GVHD), a syndrome that arises when immune cells present in the, transplanted HSC (the graft) recognize the recipient/hosts cells/tissues as foreign and mount an immune response that leads to the destruction of multiple host tissues.

Organ toxicities. During CAR-T therapy, immune system cells become stimulated and release chemical messengers called cytokines. Too many cytokines can result in fever, trouble breathing and can be life-threatening. In the case of cytokine release syndrome, individuals may require anti-cytokine therapy.

Next, visit CAR T Basics to learn more about approved cell therapies, and cell therapy use in disease treatments for blood disorders.

Was this information helpful?If so, please share! All ASGCT Patient Education resources are free touse bysharingon social media,embeddingthevideo, orsimply linking tothis page!Please credit the American Society of Gene and Cell Therapyor tag@ASGCTherapy.

Read the rest here:
Cell Therapy Basics

Posted in Cell Therapy | Comments Off