Stem cells Basics

Stem Cell Technology: 

Stem Cell Technology Mr. Jyoti Prakash Rath Asst. Professor, Medical Biotechnology Chettinad University, Kelambakkam Tamil Nadu

Why stem cells?: 

Why stem cells? Advancing knowledge about how an organism develops from a single cell How healthy cells replace damaged cells in adult organisms To develop possibilities of cell base therapy

What are stem cells and why are they important?: 

What are stem cells and why are they important? Two important characteristics First, they are unspecialized cells that renew themselves for long periods through cell division The second is that under certain physiologic or experimental conditions, they can be induced to become cells with special functions

Tissues regenerate new functional cells by: 

Tissues regenerate new functional cells by either dividing the existing functional cells or by activating an adult stem cell population A stem cell must make more copies of itself (self-renew) and give rise to more capable offspring (differentiate)

Unique properties of stem cells: 

All stem cells—regardless of their source have three general properties: They are capable of dividing and renewing themselves for long periods They are unspecialized They can give rise to specialized cell types Unique properties of stem cells

Stem cells are unspecialized: 

Does not have any tissue-specific structures that allow it to perform specialized functions Cannot work with its neighbors to pump blood through the body (like a heart muscle cell) Cannot carry molecules of oxygen through the bloodstream (like a red blood cell) Cannot fire electrochemical signals to other cells that allow the body to move or speak (like a nerve cell) However, unspecialized stem cells can give rise to specialized cells, including heart muscle cells, blood cells, or nerve cells Stem cells are unspecialized

Stem cells are capable of dividing and renewing themselves for long periods: 

Some signals in a mature organism that cause a stem cell population to proliferate and remain unspecialized until the cells are needed for repair of a specific tissue Unlike muscle cells, blood cells, or nerve cells—stem cells may replicate many times & it is called Proliferation - in the laboratory can yield millions of cells If the resulting cells continue to be unspecialized, like the parent stem cells, the cells are said to be capable of long-term self-renewal Stem cells are capable of dividing and renewing themselves for long periods

Stem cells can give rise to specialized cells: 

Unspecialized stem cells - specialized cells, the process is called Differentiation The internal signals are controlled by a cell's genes The external signals - chemicals secreted by other cells, physical contact with neighboring cells, and certain molecules in the microenvironment Not Known: Are the internal and external signals for cell differentiation similar for all kinds of stem cells? Can specific sets of signals be identified that promote differentiation into specific cell types? Stem cells can give rise to specialized cells

Two kinds of stem cells from animals and humans:: 

Embryonic stem cells Adult stem cells Two kinds of stem cells from animals and humans:

What are embryonic stem cells? : 

What are embryonic stem cells? Embryonic stem cells, as their name suggests, are derived from embryos. Most embryonic stem cells are derived from embryos that develop from eggs that have been fertilized in vitro —in an in vitro fertilization clinic—and then donated for research purposes with informed consent of the donors. They are not derived from eggs fertilized in a woman's body.

What are adult stem cells? : 

What are adult stem cells? An adult stem cell is thought to be an undifferentiated cell, found among differentiated cells in a tissue or organ that can renew itself and can differentiate to yield some or all of the major specialized cell types of the tissue or organ. The primary roles of adult stem cells in a living organism are to maintain and repair the tissue in which they are found. Scientists also use the term somatic stem cell instead of adult stem cell, where somatic refers to cells of the body (not the germ cells, sperm or eggs). Unlike embryonic stem cells, which are defined by their origin (cells from the preimplantation-stage embryo), the origin of adult stem cells in some mature tissues is still under investigation.

What are the similarities and differences between embryonic and adult stem cells? : 

What are the similarities and differences between embryonic and adult stem cells? One major difference between adult and embryonic stem cells is their different abilities in the number and type of differentiated cell types they can become. Embryonic stem cells can become all cell types of the body because they are pluripotent . Adult stem cells are thought to be limited to differentiating into different cell types of their tissue of origin. Embryonic stem cells can be grown relatively easily in culture. Adult stem cells are rare in mature tissues, so isolating these cells from an adult tissue is challenging, and methods to expand their numbers i n cell culture have not yet been worked out . This is an important distinction, as large numbers of cells are needed for stem cell replacement therapies.

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Scientists believe that tissues derived from embryonic and adult stem cells may differ in the likelihood of being rejected after transplantation. The use of adult stem cells and tissues derived from the patient's own adult stem cells would mean that the cells are less likely to be rejected by the immune system. This represents a significant advantage, as immune rejection can be circumvented only by continuous administration of immunosuppressive drugs, and the drugs themselves may cause deleterious side effects

Day 5 Human Embryo Blastocyst Stage, ~ 100 cells: 

Day 5 Human Embryo Blastocyst Stage, ~ 100 cells Trophoectoderm (placenta and amnion) Inner cell mass (all tissues in the body) 1/100 inch

The inner cell mass gives rise to all the cells in the body.: 

Ectoderm Outer surface Skin CNS Neuron Neural Crest Melanocyte Mesoderm Endoderm Dorsal Notochord Paraxial Bone tissue Intermediate Tubule cell of the kidney Lateral Red Blood Cell Blood vessels Heart Head Facial Muscle Digestive Tube Pancreatic Cell Pharynx Thyriod Cell Respiratory Tube Alveolar Cell Germ Cells Germ Cells Sperm and Egg The inner cell mass gives rise to all the cells in the body.

During development, the daughters of the inner cell mass differentiate into the cell types of the body.: 

During development, the daughters of the inner cell mass differentiate into the cell types of the body . Time of Gestation After Birth Endoderm Mesoderm Ectoderm Germ Sperm Or Eggs Skin Brain Heart Blood Gut Inner Cell Mass

Stem Cell – Definition: 

Stem Cell – Definition A cell that has the ability to continuously divide and differentiate (develop) into various other kind of cells/tissues

Stem Cell – are Dynamic: 

Stem Cell – are Dynamic Are undifferentiated “master” cell that do not yet have a specific function Can change to one or several different cell types (differentiate) under proper conditions Can undergo unlimited cell division, self-renewal ) Stem cell Stem cell Self-renewa l Specialized cell (e.g., white blood cell) Differentiate

How Does Cell Therapy Work?: 

How Does Cell Therapy Work? Stem cells can be used to generate healthy and functioning specialized cells, which can then replace diseased or dysfunctional cells. It is similar to the process of organ transplantation only the treatment consists of transplanting cells instead of organs .

What Diseases Can be Cured by Stem Cell Therapies: 

What Diseases Can be Cured by Stem Cell Therapies Any disease in which there is tissue degeneration can be a potential candidate for stem cell therapies

Major Progress in Several Important Health problems: 

Major Progress in Several Important Health problems Alzheimer’s disease Parkinson’s disease Spinal cord injury Heart disease Severe burns Diabetes

Drug Testing: 

Drug Testing Stem cells could allow scientists to test new drugs using human cell line which could speed up new drug development. Only drugs that were safe and had beneficial effects in cell line testing would graduate to whole animal or human testing. It would allow quicker and safer development of new drugs.

Stem cells act as Progenitor cells: 

Stem cells act as Progenitor cells In adult organisms, stem cells and progenitor cells act as a repair system for the body, replenishing specialized cells, but also maintain the normal turnover of regenerative organs, such as blood, skin or intestinal tissues.

Adult Mutipotent Stem Cells : 

Adult Mutipotent Stem Cells

Treatments becomes Specific: 

Treatments becomes Specific

Terminologies Associated with Stem Cell Technology: 

Terminologies Associated with Stem Cell Technology Long-term self-renewal —The ability of stem cells to replicate themselves by dividing into the same non-specialized cell type over long periods (many months to years) depending on the specific type of stem cell. Differentiation —The process whereby an unspecialized embryonic cell acquires the features of a specialized cell such as a heart, liver, or muscle cell. Differentiation is controlled by the interaction of a cell's genes with the physical and chemical conditions outside the cell, usually through signaling pathways involving proteins embedded in the cell surface. A stem cell must make more copies of itself (self-renew) and give rise to more capable offspring (differentiate)

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Embryonic stem cells —Primitive ( undifferentiated ) cells that are derived from preimplantation -stage embryos, are capable of dividing without differentiating for a prolonged period in culture, and are known to develop into cells and tissues of the three primary germ layers . Embryonic stem cell line —Embryonic stem cells, which have been cultured under in vitro conditions that allow proliferation without differentiation for months to years.

Day 5 Human Embryo Blastocyst Stage, ~ 100 cells: 

Day 5 Human Embryo Blastocyst Stage, ~ 100 cells Trophoectoderm (placenta and amnion) Inner cell mass (all tissues in the body) Blastocyst —A preimplantation embryo of about 150 cells produced by cell division following fertilization. The blastocyst is a sphere made up of an outer layer of cells (the trophoblast ), a fluid-filled cavity (the blastocoel ), and a cluster of cells on the interior (the inner cell mass ). Inner cell mass (ICM) —The cluster of cells inside the blastocyst . These cells give rise to the embryo and ultimately the fetus . The ICM may be used to generate embryonic stem cells . Trophoblast —The outer cell layer of the blastocyst . It is responsible for implantation and develops into the extraembryonic tissues, including the placenta, and controls the exchange of oxygen and metabolites between mother and embryo .

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Somatic (adult) stem cells —A relatively rare undifferentiated cell found in many organs and differentiated tissues with a limited capacity for both self renewal (in the laboratory) and differentiation. Such cells vary in their differentiation capacity, but it is usually limited to cell types in the organ of origin. This is an active area of investigation.

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Hematopoietic stem cell —A stem cell that gives rise to all red and white blood cells and platelets. Bone marrow stromal stem cells (skeletal stem cells) —A multipotent subset of bone marrow stromal cells able to form bone, cartilage, stromal cells that support blood formation, fat, and fibrous tissue. Neural stem cell —A stem cell found in adult neural tissue that can give rise to neurons and glial (supporting) cells. Examples of glial cells include astrocytes and oligodendrocytes . Astrocyte —A type of supporting (glial) cell found in the nervous system. Umbilical cord blood stem cells —Stem cells collected from the umbilical cord at birth that can produce all of the blood cells in the body (hematopoietic). Cord blood is currently used to treat patients who have undergone chemotherapy to destroy their bone marrow due to cancer or other blood-related disorders. Human embryonic stem cell (hESC) —A type of pluripotent stem cells derived from early stage human embryos, up to and including the blastocyst stage, that are capable of dividing without differentiating for a prolonged period in culture, and are known to develop into cells and tissues of the three primary germ layers . Mesenchymal stem cells —A term that is currently used to define non-blood adult stem cells from a variety of tissues, although it is not clear that mesenchymal stem cells from different tissues are the same.

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Induced pluripotent stem cell (iPSC) —are adult cells that have been genetically reprogrammed to an embryonic stem cell–like state by being forced to express genes and factors important for maintaining the defining properties of embryonic stem cells. Although these cells meet the defining criteria for pluripotent stem cells, it is not known if iPSCs and embryonic stem cells differ in clinically significant ways. Mouse iPSCs demonstrate important characteristics of pluripotent stem cells, including expressing stem cell markers, forming tumors containing cells from all three germ layers, and being able to contribute to many different tissues when injected into mouse embryos at a very early stage in development.

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Cell-based therapies —Treatment in which stem cells are induced to differentiate into the specific cell type required to repair damaged or destroyed cells or tissues.

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Regenerative medicine —A field of medicine devoted to treatments in which stem cells are induced to differentiate into the specific cell type required to repair damaged or destroyed cell populations or tissues.

Regenerative Medicine: An Analogy: 

Regenerative Medicine: An Analogy The Greek Titan, Prometheus , is a fitting symbol for regenerative medicine . As punishment for giving fire to Humankind, Zeus ordered Prometheus chained to a rock and sent an eagle to eat his liver each day. However, Prometheus' liver was able to regenerate itself daily , enabling him to survive . The scientific researchers and medical doctors of today hope to make the legendary concept of regeneration into reality by developing therapies to restore lost, damaged, or aging cells and tissues in the human body.

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Embryo —In humans, the developing organism from the time of fertilization until the end of the eighth week of gestation, when it is called a fetus . At left is an embryo 4 weeks after fertilization. At right is a fetus 8 weeks after fertilization Fetus —In humans, the developing human from approximately eight weeks after conception until the time of its birth.

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Epigenetic — Having to do with the process by which regulatory proteins can turn genes on or off in a way that can be passed on during cell division. Epigenetics refers to modifications that modulate gene expression and dictate changes in the phenotype that are not directly controlled by DNA sequence. Among the induced genes during ES neurogenesis, Hox genes are of particular interest. Hox genes encode for master regulators of embryonic neurogenesis and ES cell differentiation, which are controlled by chromatin remodelling and epigenetics. Researchers investigate the link between epigenetics and neurogenesis using specific null ES cells.

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Feeder layer —Cells used in co-culture to maintain pluripotent stem cells. For human embryonic stem cell culture, typical feeder layers include mouse embryonic fibroblasts (MEFs) or human embryonic fibroblasts that have been treated to prevent them from dividing.

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Gastrulation —The process in which cells proliferate and migrate within the embryo to transform the inner cell mass of the blastocyst stage into an embryo containing all three primary germ layers .

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Germ layers —After the blastocyst stage of embryonic development, the inner cell mass of the blastocyst goes through gastrulation , a period when the inner cell mass becomes organized into three distinct cell layers, called germ layers. The three layers are the ectoderm , the mesoderm , and the endoderm . Embryoid bodies —Rounded collections of cells that arise when embryonic stem cells are cultured in suspension. Embryoid bodies contain cell types derived from all 3 germ layers .

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In vitro —Latin for "in glass"; in a laboratory dish or test tube; an artificial environment. In vitro fertilization —A technique that unites the egg and sperm in a laboratory instead of inside the female body.

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Totipotent —Having the ability to give rise to all the cell types of the body plus all of the cell types that make up the extraembryonic tissues such as the placenta. Pluripotent —The state of a single cell that is capable of differentiating into all tissues of an organism, but not alone capable of sustaining full organismal development. Multipotent —Having the ability to develop into more than one cell type of the body.

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Therapeutic cloning —The process of using somatic cell nuclear transfer (SCNT) to produce cells that exactly match a patient. By combining a patient's somatic cell nucleus and an enucleated egg, a scientist may harvest embryonic stem cells from the resulting embryo that can be used to generate tissues that match a patient's body. This means the tissues created are unlikely to be rejected by the patient's immune system. See also Somatic cell nuclear transfer (SCNT) .

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Teratoma —A multi-layered benign tumor that grows from pluripotent cells injected into mice with a dysfunctional immune system. Scientists test whether they have established a human embryonic stem cell (hESC) line by injecting putative stem cells into such mice and verifying that the resulting teratomas contain cells derived from all three embryonic germ layers . Embryoid bodies —Rounded collections of cells that arise when embryonic stem cells are cultured in suspension. Embryoid bodies contain cell types derived from all 3 germ layers . Markable features to observe to verify establishment of Stem cells growth in artificial condition

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Embryonic germ cells — Pluripotent stem cells that are derived from early germ cells (those that would become sperm and eggs). Embryonic germ cells (EG cells) are thought to have properties similar to embryonic stem cells. Embryonic stem cells are established from the inner cell mass of the blastocyst, whereas embryonic germ cells are established from primordial germ cells of the fetus. Neonatal testis cells can give rise to both multipotent and unipotent germline stem cells. Embryonic stem cells, embryonic germ cells and multipotent germline stem cells can produce germline chimeras after injection into the blastocyst and teratomas in the testis, but cannot produce sperm. In contrast, germline stem cells can produce sperm after injection into the testis, but do not produce germline chimeras or teratomas. SSCs of adult testis possess both potentials, producing germline chimeras in the embryo as well as sperm in the testis. Adult SSCs can also produce multipotent adult germline stem cells, which can differentiate into various cell types in vivo and in vitro . The spermatogeneic potential of maGSCs is unknown.

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Differentiation —The process whereby an unspecialized embryonic cell acquires the features of a specialized cell such as a heart, liver, or muscle cell. Differentiation is controlled by the interaction of a cell's genes with the physical and chemical conditions outside the cell, usually through signaling pathways involving proteins embedded in the cell surface.