Stem Cells

Stem cells are one of the most fascinating and promising areas of scientific research today. These remarkable cells have the unique ability to develop into many different types of cells in the body, making them essential for growth, repair, and regeneration.

Get started Sign up for free
Stem Cells Stem Cells

Create learning materials about Stem Cells with our free learning app!

  • Instand access to millions of learning materials
  • Flashcards, notes, mock-exams and more
  • Everything you need to ace your exams
Create a free account

Millions of flashcards designed to help you ace your studies

Sign up for free

Convert documents into flashcards for free with AI!

Table of contents

    From treating a wide range of diseases and injuries to unlocking the secrets of human development, stem cells have the potential to revolutionize modern medicine and transform our understanding of life itself. Join us on a journey to explore the incredible world of stem cells and discover the groundbreaking research that is unlocking their full potential.

    What are stem cells?

    Stem cells are cells that have the potential to express any one of their genes in their genome. This means that they have the potential to differentiate into any type of cell in the body.

    Stem cells are undifferentiated cells capable of proliferating (increasing in number rapidly) and turning into specialised cells.

    Differentiation of stem cells

    Stem cells are, as we have seen, undifferentiated cells that are able to proliferate or turn into specialised cells. The transformation of a stem cell into a differentiated cell is called differentiation.

    Single-celled organisms carry out all their essential functions themselves. Although the functions they perform may be adequate, they cannot be efficient in performing all of them. This is because each function requires a different type of cellular structure and machinery.

    No one cell can provide the best conditions for all functions. In multicellular organisms, each cell becomes specialised in a variety of ways to perform a particular function, and the adaptations they acquire ensure that they are maximally efficient in their functions.

    The specialised cells are the outcome of stem cells’ differentiation. In most multicellular organisms, including humans, all cells are derived from a fertilized egg called the zygote. In the early stage of development, the zygote undergoes multiple mitotic divisions forming a ball of identical cells (morula). As the organism develops and the cells mature, they change the pattern of the genes they express and hence become different from each other.

    It is important to note that all cells within an organism contain the same genome, but they express different parts of it.

    There are certain genes that are expressed in almost all cells (housekeeping genes). These are genes that encode essential molecules such as enzymes of respiration and enzymes involved in transcription and translation. Other genes are expressed only in specific cells and are turned off in the other cells.

    For example, the gene for insulin is only expressed in beta cells of the islets of Langerhans in the pancreas. Another example would be mesophyll cells in plants that become specialised for photosynthesis. For their differentiation, the genes needed for photosynthesis are expressed while other genes that are not needed are turned off since their expression would be wasteful and would lower the mesophyll cells’ efficiency.

    Let’s have a look at the specialised red blood cells and how the process of their differentiation from stem cells increases the amount of oxygen they can carry to other tissues and organs.

    Erythrocytes specialisation

    Erythrocytes (red blood cells) have specific adaptations to carry out a specific function (as specialised cells), unlike stem cells, which only possess the basic machine work of a cell.

    During the process of erythropoiesis, the haematopoietic stem cells differentiate and adopt different shapes and features as they become erythrocytes.

    Erythropoiesis (‘erythro’ meaning ‘red’ + ‘poiesis’ meaning ‘to make’) is the process that produces mature red blood cells from haemopoietic stem cells in the bone marrow.

    Haematopoietic stem cells are cells that can differentiate and develop into all types of blood cells, such as white blood cells, red blood cells, and platelets.

    These changes include:

    • Loss of their nucleus and mitochondria to create more space for haemoglobin, which is the main oxygen-carrying protein in erythrocytes.

    • An increase in the concentration of haemoglobin in the cell increases to ensure maximum oxygen-carrying capacity.

    • Adoption of a specific cytoskeleton that gives the erythrocytes a biconcave structure granting them a larger surface area for gas exchange and increased flexibility to travel through narrow blood vessels.

    These adaptations improve the ability of the specialised cells to carry out their function. In this particular example, the adaptations in erythrocytes allow them to efficiently pick up oxygen in the lungs, travel through narrow blood vessels and give off their oxygen to tissues and organs in need.

    stem cell diagram, erythropoiesis in the bone marrow, haemoglobin, reticulocyte erythroblast studysmarter

    Fig. 1 - A diagram illustrating the process of erythropoiesis in the bone marrow

    Properties of stem cells

    In mature mammals, only a few cells retain the ability to divide and differentiate into specialised cells. After differentiation, most specialised cells lose the ability to proliferate. This leads to an increased risk of permanent damage after an injury, especially in tissues such as the brain and heart.

    Neurons and cardiomyocytes are permanent cells with no proliferative properties and hence cannot regenerate new cells to replace the damaged cells. As result, damages caused by a stroke or a myocardial infarction are irreversible and hence can be life-threatening.

    Cardiomyocytes are the cells in the cardiac wall muscle that contract in a healthy heart.

    Stem cells have two main properties:

    1. They have a high capacity to differentiate into more specialised cells. This property is referred to as potency. Each stem cell type has a different potency depending on the number of cell lineages it can give way to.

    2. They have the ability to self-renew, so they keep producing stem cells.

    Types of stem cells

    In order to differentiate into a particular cell type, the stem cell needs to transcribe and translate only some specific parts of its DNA and keep the remaining parts turned off.

    When becoming specialised, stem cells take on specific features and adaptations. These may include changing the cell structure, membrane proteins, as well as the type or number of the organelles within them. The process of stem cells becoming specialised cells is called cell differentiation.

    Terminally differentiated cells cannot proliferate and replace themselves as they have irreversibly lost the ability to undergo mitosis while acquiring specialised adaptations.

    Stem cells originate from a variety of sources in mammals. These include:

    • Embryonic stem cells: obtained from embryos in their early stages of development.

    • Umbilical cord blood stem cells: obtained from umbilical cord blood. They are similar to adult stem cells.

    • Placental stem cells: found in the placenta. They have the potential to develop into specific types of cells.

    • Adult stem cells: found in tissues of the fetus and throughout adulthood. These cells are specific to a tissue or organ and their roles are maintenance and repair.

    Potency is the ability of a stem cell to become differentiated into various types of specialised cells.

    stem cell diagram, types of stem cells, hierarchy of stem cell potency, studysmarter

    Fig. 2 - This stem cell diagram shows the hierarchy of potency between stem cells

    There are several types of stem cells, each possessing a different level of potency. These are:

    • Totipotent Stem Cells – these have the ability to become any cell in the body. This means they have the capability to form a complete organism. They are only found in the early stage of embryonic development. An example of a totipotent stem cell is the zygote itself.

    • Pluripotent Stem Cells – these cells are found in the embryo and can differentiate into almost any cell type. However, they lack the ability to form cells that make up the placenta. Examples of pluripotent stem cells are embryonic stem cells and fetal stem cells.

    • Multipotent Stem Cells – these stem cells are found in adults and can differentiate into various cells but are limited in their capacity. They usually develop into cells of a particular type. For instance, red and white blood cells can be formed from multipotent stem cells called haemopoietic stem cells found in the bone marrow

    • Unipotent Stem Cells – these cells can only differentiate into one type of cell, hence uni. They are derived from multipotent stem cells and are present in some adult tissues for regenerative purposes.

    This image shows the types of stem cells and the potential parts of the body in which they may prove useful.

    stem cell diagram, application of human stem cells, studysmarter

    Fig. 3 - Potential application of human stem cells for producing differentiated cells that can be used for therapeutic purposes

    Uses of stem cells

    Stem cells have a wide range of uses in medicine and scientific research. One of the most promising applications of stem cells is in the development of new treatments for diseases and injuries. By replacing or repairing damaged tissues and organs with healthy, functional cells, stem cell therapies have the potential to revolutionize the treatment of conditions such as heart disease, diabetes, and spinal cord injuries.

    Stem cells are also used extensively in scientific research to study human development, genetic disorders, and the effects of drugs and other substances on the body. By providing a window into the earliest stages of life, stem cells are helping scientists to better understand how the human body develops and functions, and to develop new treatments for a wide range of diseases and conditions.

    Stem cells in research

    Stem cells are widely used in research. They can be used to study cellular processes specific to certain types of cells that would be hard to obtain if it weren't for induced pluripotent stem cells (see below).

    Stem cells are also useful to research developmental processes, which would be impossible without them due to ethical concerns. For example, research would not be able to fully understand the signalling processes during embryonic development if not for stem cell research, as using human embryos for this purpose would be absolutely unethical and is banned.

    Stem cells in medicine

    Stem cell therapies have the potential to save lives and improve the quality of life for many people. This is because stem cells can divide into a large variety of differentiated cell types and so can be used to replace those cells which are damaged by injuries or diseases.

    The stem cells in the bone marrow, called haematopoietic stem cells, can divide to produce other blood cells (both white and red blood cells). These stem cells are used to treat immune system diseases and illnesses affecting the blood, such as leukaemia.

    In leukaemia patients, some blood cells divide uncontrollably in their bone marrow. This limits the ability of the haematopoietic stem cells to produce enough blood cells. Treatment for patients with leukaemia includes chemotherapy and radiation, both of which target leukaemia cells. After this, more haematopoietic stem cells can be placed (implanted) into the bone marrow to produce a normal, healthy amount of blood.

    Severe combined immunodeficiency (SCID) is a genetic disorder that affects both B and T lymphocyte-mediated immune responses. As a result, patients suffering from SCID have a very weak immune system. Their lymphocytes are unable to create enough antibodies or lack the correct ones to fight and defend against the threat of a pathogen. Therefore, those who suffer from SCID are very vulnerable to infections.

    Even those infections which are not usually considered to be severe are liable to be life-threatening in SCID patients. SCID can be treated with a bone marrow transplant. This transplant replaces the faulty bone marrow with donor bone marrow that contains stem cells without the defective genes that cause SCID. The healthy bone marrow stem cells then differentiate to produce functional lymphocytes that can then produce the necessary antibodies to fight and defend against pathogens, so the immune system functions normally.

    Treatment of other diseases using stem cells

    Stem cells can be used to create specialised cells which can treat a range of human diseases and injuries. Some of the uses of stem cell-derived specialised cells are:

    • Skeletal muscle cells can be used to treat illnesses such as muscular dystrophy.

    • Beta cells of the pancreas can be used to treat Type 1 diabetes.

    • Neurons may be used to treat neurodegenerative diseases such as Parkinson’s and Alzheimer’s diseases.

    • Epidermal skin cells can be used in the treatment of burns and wounds as they form the outer layer of skin which is damaged in these injuries.

    • Retina cells of the eye can be transplanted into the eyes of patients with macular degeneration.

    Induced pluripotent stem cells (iPS cells)

    Induced pluripotent stem cells (iPS cells) are artificially produced from unipotent stem cells in a laboratory.

    The process of making iPS cells involves adding specific transcription factors into already specialised cells, which are then ‘reprogrammed’ into pluripotent stem cells. It is in a way the reverse process of the differentiation a stem cell goes through when transforming into a specialised cell.

    The specific transcription factors used in this process cause the specialised cells to express genes that are associated with pluripotency. As a result, the iPS cells will have similar characteristics to embryonic stem cells and hence are capable of self-renewal and differentiation into almost any cell in the whole body.

    IPS cells play a major role in regenerative medicine. The iPS cells derived from a patient’s own cells can be used to replace damaged cells or create new tissues or possibly even organs. For example, iPS cells can be used to regrown skin grafts for treating burn injuries or replacing damaged neurons in neurodegenerative diseases such as Parkinson’s disease. Since the cells are derived from the patient’s own cells, there will be no concern about the rejection of the cells by the patient’s immune system. Therefore, using IPS cells involves fewer complications and is surrounded by fewer ethical issues than the use of embryonic stem cells.

    Embryonic stem cell research raises some ethical issues because it involves obtaining stem cells from embryos created by in vitro fertilisation (IVF). This procedure results in the destruction of an embryo that has the potential to become a fetus if placed in a womb.

    stem cell diagram, induced pluripotent stem cells iPS, studysmarter

    Fig. 4 - The overall process of generating induced pluripotent stem cells from differentiated cells

    Advantages and disadvantages of stem cells

    Stem cells have a number of advantages over previous treatment options. However, generating or obtaining stem cells for medical purposes can be costly and even ethically questionable. Research is still ongoing to improve the current stem cell systems and help future patients.

    • Disease modelling and drug discovery: stem cells can be developed into systems to study diseases with fewer ethical concerns than animal research and more biological relevance than purely computerised or in vitro research methods.
    • Reduced risk of rejection: using a patient's own stem cells or iPS for therapy and transplants can reduce the risk of rejection, as the cells are genetically identical to the patient's own cells.
    • Potential for personalized medicine: the future of medicine is personalized. Although as humans our bodies work in similar ways, each of us has slight differences that can make drugs or certain therapies more or less effective. Using the patient's genetic information and stem cells, we will be able to tailor treatment to the specific necessities of a patient, improving their outcome.
    • Research into developmental biology: studying stem cells can help researchers understand how cells differentiate and develop into different types of tissue, which can lead to new insights into human development and disease.
    • iPS cells have fewer ethical concerns compared to embryonic stem cells, as the latter are obtained through the destruction of human embryos. Stem cell research can also reduce ethical concerns surrounding animal research, although this depends on how and which types of stem cells are used.

    Stem cells also have disadvantages, though: the ethical concerns surrounding embryonic stem cells can be solved by using iPCs, but the high cost and complexity of stem cell production and maintenance still make this research and therapeutic technique complicated to use and scale.

    Stem Cells - Key takeaways

    • Stem cells are cells that can differentiate into different types of cells.
    • They have several sources: Embryonic stem cells, placenta stem cells, umbilical cord blood stem cells, and adult stem cells.
    • There are four types of stem cells:
      • Totipotent stem cells
      • Pluripotent stem cells
      • Multipotent stem cells
      • Unipotent stem cells
    • Induced Pluripotent Stem Cells (iPS cells) are produced from unipotent stem cells to which specific transcription factors are introduced to give them the ability to gain pluripotency. iPS cells can replace embryonic stem cell research and can be used to regenerate damaged tissues.
    • Stem cells can be used in regenerative medicine and can treat many illnesses and diseases e.g. SCID, leukaemia, and Parkinson’s disease.
    Frequently Asked Questions about Stem Cells

    What diseases can be cured with stem cells?

    Stem cell therapies can be used to treat a number of diseases for example leukaemia, SCID and muscular dystrophy.

    What causes damage to stem cells?

    Mutations in DNA sequences can cause genes that code for stem cells to not be expressed. 

    What are stem cells used for?

    Stem cells can be used to replace cells damaged by illness or injury. They can also be used to create new tissues to replace damaged ones. This is carried out during stem cell therapies.

    What is stem cell therapy?

    Stem cell therapies are treatments of diseases or injuries involving the use of stem cells e.g. hematopoietic stem cell transplantation.

    Where are stem cells found? 

    The potential sources of stem cells are: adult stem cells, embryonic stem cells, umbilical cord stem cells, and induced pluripotent stem cells.

    What are stem cells?

    Stem cells are unspecialised cells that can develop into other types of cells.

    What part of a human bone contains stem cells?

    The part of a human bone that contains stem cells is called the bone marrow. This is a sponge-like tissue found in the middle of bones

    Can stem cells cause diseases?

    When damage to DNA occurs via mutations, genes that control stem cell differentiation and other genes such as tumour suppressors and oncogenes, may not be expressed or their activity is deregulated. These changes can cause the development of tumours and cancers as a division of stem cells is not controlled. 



    Test your knowledge with multiple choice flashcards

    What type of stem cell is an embryonic stem cell?

    What type of stem cell is a haemopoietic stem cell?

    Which cells are affected in severe combined immunodeficiency (SCID)?

    Next

    Discover learning materials with the free StudySmarter app

    Sign up for free
    1
    About StudySmarter

    StudySmarter is a globally recognized educational technology company, offering a holistic learning platform designed for students of all ages and educational levels. Our platform provides learning support for a wide range of subjects, including STEM, Social Sciences, and Languages and also helps students to successfully master various tests and exams worldwide, such as GCSE, A Level, SAT, ACT, Abitur, and more. We offer an extensive library of learning materials, including interactive flashcards, comprehensive textbook solutions, and detailed explanations. The cutting-edge technology and tools we provide help students create their own learning materials. StudySmarter’s content is not only expert-verified but also regularly updated to ensure accuracy and relevance.

    Learn more
    StudySmarter Editorial Team

    Team Biology Teachers

    • 15 minutes reading time
    • Checked by StudySmarter Editorial Team
    Save Explanation Save Explanation

    Study anywhere. Anytime.Across all devices.

    Sign-up for free

    Sign up to highlight and take notes. It’s 100% free.

    Join over 22 million students in learning with our StudySmarter App

    The first learning app that truly has everything you need to ace your exams in one place

    • Flashcards & Quizzes
    • AI Study Assistant
    • Study Planner
    • Mock-Exams
    • Smart Note-Taking
    Join over 22 million students in learning with our StudySmarter App
    Sign up with Email

    Get unlimited access with a free StudySmarter account.

    • Instant access to millions of learning materials.
    • Flashcards, notes, mock-exams, AI tools and more.
    • Everything you need to ace your exams.
    Second Popup Banner