Differentiation and Stem Cells Higher Human Biology Unit 1 – Sub-Topic 1 (a)

Learning Intention To discuss what differentiation of cells is and to gain knowledge of the types of stem cells

Why have specialised cells?

Introduction The human body is made up of many specialised cells that perform specific functions. Specialised cells arise from the differentiation of unspecialised cells during embryological development. Differentiation also occurs in later developmental stages tissue repair etc in mature adults Link is to an animation on differentiation Differentiation is when an unspecialised cell becomes specialised in structure and biochemical properties, making them perfectly adapted for carrying out a particular function. http://www.educationscotland.gov.uk/highersciences/humanbiology/animations/stemcell.asp

Examples of Differentiation The original pluripotent embryonic stem cells gradually differentiate into specialised cells which form tissues. Tissue types include:- Epithelial Connective Muscle Nervous

Epithelial – Cover the body surface and line body cavities Types of tissue Epithelial – Cover the body surface and line body cavities Ciliated cells of windpipe Flat cells of cheek

Types of tissue Connective – Includes blood, bone and cartilage

Muscle cells – Form muscle tissue Types of tissue Muscle cells – Form muscle tissue Muscles that move your skeleton Muscles of the heart Muscles in the intestine and blood vessels

Types of tissue Nervous cells– Form nerve tissue Nerve carry messages from sense organs to the brain and then return signals to muscles. DON’T LEARN

What are stem cells? Stem cells are unspecialised somatic cells that have the ability to reproduce and differentiate into a diverse range of specialised cells. Why relatively? It is either unspecialised or not

Stem cell definitions Potency……….. A measure of how many types of specialized cell a stem cell can make Stem cell type Description Examples Totipotent Each cell can develop into a new individual Cells from early (1-3 days) embryos (zygote) Pluripotent Cells can form any (over 200) cell types Some cells of blastocyst (5 to 14 days) Multipotent Cells differentiated, but can form a number of other tissues Fetal tissue, cord blood, and adult stem cells Unipotent Can give rise to only 1 cell type Spermatogonial cells in testicles only make sperm Stem cell jargon Scientists use the words pluripotent and multipotent to help them describe stem cells. ALL stem cells can both self-renew and differentiate, BUT some stem cells can make more kinds of specialized cells than others. The terms on the slide are the key ones to remember. There are also stem cells that are: TOTIPOTENT: can differentiate into all types of specialized cells in the body PLUS cells that are needed during development of the embryo only: placenta, yolk sac, umbilical cord. UNIPOTENT: can only differentiate into one type of specialized cell. For example, spermatogonial stem cells (found in the testicles) are unipotent because they can only form sperm cells. A useful place to look up other words and phrases to do with stem cells is the EuroStemCell online glossary: www.eurostemcell.org/glossary 12

Types of stem cells Adult – also known as tissue Embryonic Found in blastocyst Pluripotent ( can make all cell types) Called embryonic when they self re-new in the lab Found in specific areas of the body e.g. Bone marrow Multipotent ( can only make cell types in a particular tissue

Embryonic stem cells Embryonic stem cells are derived from an embryo about 4–5 days old (bastocyst). These cells have the ability to differentiate into all of the cell types that make up an organism. They are said to be pluripotent

Adult (tissue) stem cells Adult or tissue stem cells are found in small numbers in the tissues and organs of adults and children, including the brain, bone marrow, skeletal muscle and skin. These cells give rise to a much more limited range of cell types and will tend to develop into cell types that are closely related to the tissue in which they are found. They are said to be mutipotent These cells replenish differentiated cells that need replaced in the tissues in which they are found.

Other types of stem cells Stem cells can also be taken from the umbilical cord of new babies. Like adult stem cells, these cells can differentiate into a limited range of specialised cells.

Induced pluripotent stem cells Induced pluripotent stem cells are adult cells that have been genetically reprogrammed to an embryonic stem cell-like state. First video is method used by Gurdon and Yamanaka Second Video is an interview with Gurdon http://www.bbc.co.uk/news/science-environment-19878542 http://www.bbc.co.uk/news/science-environment-19872346

System Cell Organism Tissue Questions and Answers What process is responsible for unspecialised cells becoming different? 2. Name the 3 other different types of tissue and give an example of each Epithelial e.g. Cheek cells 3. What are stem cells and name the two types of stem cells? 4. In the very early embryo, embryonic stem cells differentiate into all the cell types that make up the organism. What term is used for cells that can do this? 5. Tissue (adult) stem cells are involved in growth, repair and renewal of the cells found in that tissue. What term is used for cells that can do this? 6. Put the following in the correct order of complexity System Cell Organism Tissue

System Cell Organism Tissue Questions and Answers What process is responsible for unspecialised cells becoming different Differentiation 2. Name the 3 other different types of tissue and give an example of each Epithelial e.g. Cheek cells Connective e.g. Blood, bone or cartilage Muscle e.g. Skeletal, cardiac or smooth Nerve e.g. Sensory or motor nerves 3. What are stem cells and name the two types of stem cells Stem cells are unspecialised somatic cells that have the ability to reproduce and differentiate into a diverse range of specialised cells Embryonic and Adult ( tissue ) 4. In the very early embryo, embryonic stem cells differentiate into all the cell types that make up the organism. What term is used for cells that can do this? Pluripotent 5. Tissue (adult) stem cells are involved in growth, repair and renewal of the cells found in that tissue. What term is used for cells that can do this? Multipotent 6. Put the following in the correct order of complexity System Cell Organism Tissue

Learning Outcomes Differentiation: During embryological development the unspecialised stem cells of the early embryo differentiate into cells with specialised functions. Stem cells: Stem cells are unspecialised somatic cells that can divide to make copies of themselves ( self renew ) and can differentiate into specialised cells of one or more types. In the very early embryo, embryonic stem cells differentiate into all the cell types that make up the organism. Tissue (adult) stem cells are involved in growth, repair and renewal of the cells found in that tissue. They are said to be multipotent The main body tissue types are epithelial, connective, muscle and nerve Multipotent haematopoietic stem cells in the red bone marrow give rise to all the cell types in the blood e.g. red blood cells, platelets and the various forms of phagocytes and lymphocytes.( see previous lesson ) Tissues work together to form more complex organs, systems and organisms such as humans