Chapter 1. Chapter 13: Stem Cells and Cell Differentiation

1.1 Introduction

Interactive Study Guide
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Polaris Trail

Welcome to the Interactive Study Guide for Chapter 13: Stem Cells and Cell Differentiation! This Study Guide will help you master your understanding of the chapter's Driving Questions, using interactive Infographics and activities, as well as targeted assessment questions. Click "Next" to get started, or select a Driving Question from the drop-down menu to the right.

Grow Your Own:

Stem cells could be the key to engineering organs

DRIVING QUESTIONS

  • What is the structure of tissues and organs and how can organs be repaired or replaced?
  • What are the properties of specialized cells in tissues and how do stem cells differentiate into these specialized cells?
  • How do stem cells contribute to regenerative medicine and how can we obtain or produce stem cells for this purpose?

1.2 Driving Question 1

Driving Question 1

What is the structure of tissues and organs, and how can organs be repaired or replaced?

Why should you care?

If we could engineer tissues and organs from an individual’s own cells, we could routinely perform tissue grafts and organ transplants without the problems that arise from tissue rejection and lack of donors. Reaching that goal will be difficult because of the complex hierarchical structure of tissues and organs. Engineering a single, simple tissue is challenging; engineering an entire organ, composed of multiple tissues organized in very specific ways, is even more so.

The idea of using engineered tissues to treat disease and to generate organs for transplantation depends upon the unique ability of stem cells to regenerate cells and tissues worn out with age or damaged by disease and injury.

Cell therapy and the use of therapeutic drugs to stimulate specific stem cells in the bodyare two types of regenerative medicine which researchers hope will lead to new treatments for degenerative diseases (Parkinson’s, for example) and autoimmune diseases (such as diabetes) that effect countless individuals around the world.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Describe the importance of stem cells for maintaining healthy tissues.
  2. Describe the hierarchical organization of cells, tissues, organs, and organ systems.
  3. Explain the goal of regenerative medicine and the role of stem cells in meeting this goal.
  4. Compare and contrast the use of stem cells, drugs and biodegradable scaffolding for regenerative therapies.

Infographic Focus

The infographics most pertinent to the Driving Question are 13.1, 13.2, 13.3, 13.5, 13.6 and Table 13.1.

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
7xY4wr/P/9tDpPuuq/QehKNE1EgzFdVuKEC1lcvgqkoflhcyROVr9vRgDB6EfaK89FJLOQ== An organized group of different cell types that work together to carry out a particular function.
tF8wGWQuX7uduIpkQtQLFy4g0XTSuKS15BymLW9LFneCeVzQtaEKdFMC4kJOWDsM3Ud4Wg== Stem cells located in tissues that help maintain and regenerate those tissues.
oo1PqP3DhyEWQ+XS4IuigHmU/3Fikitq9czIARbP+GabNK0Zr4OHP62vSqZl6AB+q5nQcg== An organized group of different cell types that work together to carry out a particular function.
Table
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Describe the importance of stem cells for maintaining healthy tissues.

Question 1.1

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Stem cells are found in many, likely all, tissues of the body.

Question 1.2

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Embryonic stem cells have the potential to become any cell type in the body. Adult stem cells typically become the cell type of the tissue that they are in (e.g., bone marrow stem cells can divide and produce various kinds of blood cells).

Question 1.3

ernbz6vr3XFxOJ6tcf7Ih/LUIVudIY3UGcdIq/GJ0wI5EWepGvFzud4aBvH6WtX2PehkfQ==
Stem cells are important for tissue health because as a tissue gets older, it has to have a mechanism to replace its dead and damaged cells. If there were no stem cells, our organs and tissues would grow old and cease to function, sometimes in a matter of weeks (like our skin). Stem cells keeps the tissues fresh and functioning.

Describe the hierarchy of cells, tissues, organs, and organ systems.

Question 1.4

WSFQzRAHeIM1hwGv5tBIqDwWtVZTnI9DDRcjmVconm7ztyZyNho8M4gQW8oXaLIRnSZ6dfXWqoh6E+ZP2Aq4CFrf/ydQL/uWugW2Lpg2WIU=
Tissues are made up of various cell types that work together to perform a function (cardiac muscle). Organs are made up of various tissue types that work together to perform a function (heart). Organ systems are made up of organs that all work together to perform a function (circulatory system).

Explain the goal of regenerative medicine and the role of stem cells in meeting this goal.

Question 1.5

TXERlrBMIbuo2AetwjWlI4AnSOQ4IyOzmefsVIe2v6Yz1MuAohG0WjjItCXtgO1i
To use stem cells to repair diseased or damaged tissue.

Question 1.6

vXFYYqqgko13cu94iWFJWzR3lITIAgSFPfA620D18jCxbsbY5SJ2olOAsxuNIi3D
The stem cells are the starting material of the regenerative process.

Compare and contrast the use of stem cells, drugs, and biodegradable scaffolding for regenerative therapies.

Question 1.7

++5Y087uQWo3cjrL7LMV5eeWHGD6uSSz85GSTZcCS5ba53CsOq5puUmcxpZYJNiu++Nq8r2U3aEvrTYIjvwFQwrN6oWu4T5McGi8mUC94RIsKt2KdMahQ1cnWBS90+5r0nBtDkRdwxfDy4mFMV9lQ9Tb4INn/bgXkjmYQimCg5r5umoGg+HGy3NtdufVK4VAIQAGDI1lGOfoBJa56mkMywuHU6KL99tZqI8szrbxpt0=
Specific chemicals (therapeutic drugs) are administered to the patient. The chemicals stimulate the patient’s own stem cells to divide and differentiate into the tissues that the patient has lost to disease or trauma. The activated stem cells are specific to the tissue that needs to be repaired.

Question 1.8

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This approach to regenerative medicine is similar to the one described previously except that the stem cells are stimulated by specific chemicals outside of the body. First, the stem cells are isolated from the patient’s diseased or damaged tissue. Second, specific chemicals are added to stimulate the stem cells. Once activated, the stem cells are injected into the patient’s diseased or damaged tissue to start the repair.

Question 1.9

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Biodegradable scaffolding has successfully regenerated healthy tissue. Like the two approaches described previously, scaffolding can be used both inside and outside of the body to grow tissue. When used inside the body, the diseased or damaged tissue is removed and replaced with a biodegradable scaffold. (Collagen is an example of a scaffold.) Stem cells from the healthy tissue surrounding the scaffold migrate to it and start to divide, in effect replacing the diseased tissue. Over time, the scaffold will degrade and leave a functioning healthy tissue. The same idea is used when a biodegradable scaffold is used ex vivo (outside the body). Stem cells are removed from the patient and stimulated by specific chemicals to start dividing and differentiating into the diseased or damaged tissue. Once stimulated, the stem cells are layered on the scaffold and allowed to grow and differentiate, producing the new tissue. Once the tissue is fully formed, the new, healthy tissue is transplanted into the patient.

Review Questions

Question 1.10

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Question 1.11

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Question 1.12

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1.3 Driving Question 2

Driving Question 2

What are the properties of specialized cells in tissues, and how do stem cells differentiate into these specialized cells?

Why should you care?

Our bodies are made of many different types of highly specialized cells with unique functions corresponding to the tissues and organs they belong to. Although all cells share the same genome, a specialized cell cannot “change” to become a different type of specialized cell. This limitation is why stem cells, rather than somatic cells, are the key to both tissue engineering and regenerative medicine.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Explain how two stem cells with identical genomes can become specialized cells with very different functions.

Infographic Focus

The infographic most pertinent to the Driving Question is 13.4.

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
WFV0a/tN+GLXuoykbLdtZbfz6a3FsyJKrUDQqVSANF/g2lB8cDaq2pF5fiTIWlGRGYgcJ+KHrpHAtwCr The process by which genes are “turned on”, or expressed, in different cell types.
NhwCvgFTZQfzjm+Sb2WrSX+xtDToAvm5UUzAKsjfzt18Nlw/pVjuIBTnSb9RK+nz7t7jDK8+T0L/CQJV The process by which a cell specializes to carry out a specific role.
Table
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Explain how two stem cells with identical genomes can become specialized cells with very different functions.

Question 1.13

Two bone marrow stem cells in your body divide to produce two white blood cells and two red blood cells respectively. These cells differ in structure and in function.

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Yes, the two cells have the same genome. Almost every cell in the body has a full, identical genome.

Question 1.14

5R02d+BuDH4yGEqfblRjKBAzkgvKyMW5G7diuytpwsVOP+fIel2dlTzdZSInhg3Co1gZgktHBC5nD0JG5AvgAkPsTl7WZD9R
No, the two cells produce a different set of proteins. Although the two cells have the same genome, different genes specific to their respective function are expressed.

Question 1.15

ABrhYMaCGuStOtxvLcwKPhIdoorcb0OsTU7IsIPouahOv1ZBcm4GOHLmNfOP4Vq1QzsSlMJfsGb6BkFp/RoYdGVHkV9Qphm1+GhfJKLn1YO3cUkTWhLAkFEkP7xKmnkBqKdDs6at8lxeoGrQx4i9h34eubFa7RXTpsd9driBn3Yk/1dl
Most of biology can be described as the production of a signal or a response to a signal. In the case of stem cells, it is typically chemical or protein signals from the cellular environment that tell the stem cell when to divide and what to differentiate into.

Thought Question: What would happen if every cell in your body expressed its entire genome instead of selectively expressing only the genes needed for its function?

Review Questions

Question 1.16

ajiZWafpCGPp2ISdwL3+XS7sgcUET5cUkANr5/xbXQCPM9firkaegmiwrlzrQBXIDT1eBkklMcLKtP4z4d7joL5YDtjfQM4HT1UHcMo6VN5zC4t9vaOLlcauLYFbJ1w2x7nsK+6rMGUkxBmBoOfi4AJD+YbWzf+kjLdx2uKUwX3vr1opbyPiMJ/f4WillMw3UhNTzw==
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Question 1.17

U4H7cahjoQc6x7jDxgn1A0Z4IbKJX70WSwYKjxV8zFc0vR6oxOMzYnXzl3VeAypU4q+p9VxkKEhm0TdjSOUNmTR7+rlRe5X91pXLJ36pZtnOfsnrfh/B7TmHZDL2U/QSb6ACN8cJNrqCUDsqJ9k7h7UgavGbS+iWfk6rjG9aCKMNGGH5KZDIwR8dpiHi2hJXCOz4rFyRcnxrNDmWCRDzRS4X/9Q4t6UbuPlvdBmVZRs422LJDnnp2Uv+VNAAZYhXKe5b9gS9yGSvZHqsabkwhAccSbz+nR1GGArue6dMSuEKDpr21r+RArLAnXq/9Np/Cp6Q2yt316EoMQlL1yWszpJaRs8Cd5GWEcJoqqG8kkImeaZPM1REjU4QgzkUzqb1
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1.4 Driving Question 3

Driving Question 3

How do stem cells contribute to regenerative medicine, and how can we obtain or produce stem cells for this purpose?

Why should you care?

The most significant controversy surrounding the use of stem cells in research and medicine is whether or not embryonic stem cells should be used or if, instead, we should limit research and medicine to the use of adult (somatic) stem cells. A clear understanding of the similarities and differences between these two types of stem cells is critical if we are each to make informed judgments about this issue.

A second point of contention is how the embryonic stem cells are obtained. One extremely controversial method is obtaining the cells from the human embryos discarded by fertility clinics. Another slightly less controversial method is called Somatic Cell Nuclear Transfer (SCNT), or more commonly termed, cell cloning. The problem with this method lies in the prospect of it being used for things other than therapeutic treatments, namely, reproductive cloning.

To avoid controversy and regulations surrounding the use of embryonic stem cells in research, scientists have been working on ways to generate cells with the pluripotency of embryonic stem cells without having to destroy embryos in the process. Induced pluripotent stem cells are a recent and potential solution to this very complex and delicate issue.

What should you know?

To fully answer this Driving Question, you should be able to:

  1. Describe where embryonic and adult (somatic) stem cells are found.
  2. Compare and contrast the differentiation potential of adult and embryonic stem cells.
  3. Explain why embryonic stem cells may have greater therapeutic potential than adult stem cells.
  4. Explain why the use of embryonic stem cells is controversial.
  5. Outline the process of somatic cell nuclear transplantation and describe the two potential outcomes of the process.
  6. Describe the process of creating induced stem cells.
  7. Discuss the significance of induced pluripotent stem cells from both scientific and ethical standpoints.

Infographic Focus

The infographics most pertinent to the Driving Question are 13.3, 13.5, 13.6, 13.7 and 13.8.

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
aQ3iPaAF631HzoSZNBVS3UIT4qvjdZl9GOya6sqa9TLlpi1ark0aUs+9LXd2kMULZN5LRW15nO02hgbzziNjcA4RBPwHHcKK7/9AaV8+4WZz3+wcSbg58LSe9wIr4s5Di/oA7GkZTi2Ap5z8xsZdNVR2g1UQqEGyV+1mnJTHGLqfM1i7 Stem cells located in tissues that help maintain and regenerate those tissues.
p9hx7yIojl6S4RE9XkUImCbtvzUjTVt/u0P1dYonHIzTfllt83W7B9OvZ4igVyENU7Wi+juoNCG1mGXNWlrEXKWJk/24dLkaDZThrKg36xVSw3AhkpDHMAtGxBxy0bDtbYfiMRWYkWBctMqT1MfK72T+GGTyHtwO/3gBdNffygDvISeZ The stage of embryonic development in which the embryo is a hollow ball of cells. Researchers can derive embryonic stem cell lines during the blastocyst stage.
5Y1zF0Agd/TowmtVGCWH1bXGOcL/pbap6BvjEleuFP/ibl8vqHO5liTUN+1zkLOnH/EwP07Ve7uoKj6w5Kim0Y7iHoAMhGpBj6Fz1FAkovlWuovTx/j4BV9Mt9VXzyzpaUE4tihIC8+3+selZQ+M5bAaQYm64UD1Kb83bdlwmIjsu1Ny Stem cells that make up an early embryo and which can differentiate into nearly every cell type in the body.
4wYfL2ZvUeNdhALiGt8qK5FV3eVgRtvSUuLIkyJrWWpefDHNjt8kQQb6B1WuUaRr0ayMLKRlWH1Q/RD+l3A6rKCFRuRKpiM4hK33rsWp1JMsvh7N7OyCJY+A6UQ4R2RgRjvgURZXpIoXJD34tobCT7iJHrGd1sr88/boF6VEp1496GCc Describes a cell with the ability to differentiate into any cell type in the body.
WefebN9bKqQ3OvuOI8heuZHkoBTNXyhoKCPZY95RyunpjcvNbDw2rMILqSQGcL7mg0N2zM/fG0ZXcz8uci8L+XNhSg/HWrsrfjA3lxf60ZQfJ41Lc8xF94L3L58q8Ctpc+qL8eow6JDgk3/SquLo8PdEtfQupo7meeMK+qxo+lGKgHEU Describes a cell with the ability to differentiate into a limited number of cell types in the body.
Zkyuv8F20TjsHdRYHFiPYNc//GPqmN+DkKMNA6kwnqm4pVBl4cNo/WMGAe9fxM6bVkXZJX9DQTws6KLmfH1NzGnAIcy/e2tPsm8Ea+EviKPT3u1RB/mv1IIZlb1zO8M1/RLjhs6ldBwJ38hweq7ATF4KcnL96XwIJNw4FnrDangutVZf A pluripotent stem cell that was generated by manipulation of a differentiated somatic cell.
Z5xRTRw3cCEcc2lWK9CNLdIVyhntcUOIsxnttjSpYxB+ENYZgBIsuxksLSGixRsB1O/mOfWL7msF/vH9s6ouDViqa8Mtz35WPAkcuf20tHz6WBYrxAigqtiDq4BTxq5xkuybF0gpt1mp/AcQ6HVTgyOrUgrF3MnfZjUTrNMRHkAyR0DR Describes a cell with the ability to differentiate into nearly any cell type in the body.
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Describe where embryonic and adult (somatic) stem cells are found.

Question 1.18

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Embryonic cells originate from the blastocyst stage of embryonic development. Adult stem cells originate from embryonic stem cells.

Compare and contrast the differentiation potential of adult and embryonic stem cells.

Question 1.19

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Adult stem cells are multipotent, meaning that they can differentiate into a limited number of cell types in the body.

Question 1.20

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Embryonic stem cells are pluripotent; which means that they can differentiate into almost any cell type in the body.

Question 1.21

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As stem cells become more specialized, they lose their potency.

Explain why embryonic stem cells may have greater therapeutic potential than adult stem cells.

Question 1.22

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Embryonic stem cells may have greater therapeutic value because they have the potential to differentiate into almost any cell type in the body, as opposed to adult stem cells, which can only differentiate into a limited number of cell types.

Explain why the use of embryonic stem cells is controversial.

Question 1.23

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Embryonic stem cell use is controversial because harvesting the cells destroys an embryo, a potential human life.

Outline somatic cell nuclear transplantation (SCNT) and describe the two possible outcomes of the process.

Question 1.24

fvAXYHN10AopP6V3TjYGUnY73u85z3R3/1XTvVT/iWtSDzWaJQf5RUxbiQsWl3Sdonaz7VZx6Is97MjnfhmDi8w1uvB56/9KJHlRXKt+utYkOlqQ2NCfLA==

1. Remove the nucleus from an egg cell.
2. Insert the nucleus of a somatic cell from a different individual.
3. The egg cell, with donor nucleus, divides and becomes an early embryo.
4. The embryo develops into the blastocyst stage.

a. The inner cell mass of the blastocyst can be removed for stem cell culture.
b. The blastocyst can be implanted in a surrogate mother to develop into a fetus.

Question 1.25

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the egg cell

Question 1.26

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the tissue donor

Question 1.27

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They can either be used either to culture stem cells or to produce genetic clones of the tissue donor organism.

Thought Question: What would happen if the tissue donor nucleus came from a sperm cell?

Describe induction of stem cells.

Question 1.28

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Adult somatic cells (completely differentiated cells like skin cells) are injected with four genes whose expression causes the cell to act like a pluripotent stem cell with the ability to differentiate into almost any cell type.

Question 1.29

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The resulting cells are like embryonic stem cells because they can differentiate into just about any cell type.

Discuss the significance of induced pluripotent stem cells from both scientific and ethical standpoints.

Question 1.30

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The researchers were able to show that a completely differentiated cell, like a muscle cell, could be dedifferentiated to an embryonic stem cell–like state.

Question 1.31

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There is less of a controversy surrounding induced pluripotent stem cells because it is not necessary to destroy an embryo to harvest cells capable of differentiating into just about any cell type.

Review Questions

Question 1.32

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2
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Question 1.33

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2
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Question 1.34

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2
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