A leukemia patient receives bone marrow from a donor. The new cells travel through the bloodstream, settle in the bones, and start making blood. These cells—stem cells—divide, replace, and repair tissue. They act without detailed instructions and respond to changes around them. Scientists can isolate them and influence what they become.
This study guide explains what stem cells are, how they divide, and how pluripotent and adult stem cells differ. You’ll learn how to grow stem cells in a dish, reprogram regular cells into induced pluripotent cells, guide them into specific types, and test whether a culture truly contains stem cells.
Stem cells: Quick Summary
Do you just need the basics? Here’s a simple explanation of what stem cells are and how scientists work with them:
🟠 Stem cells are special cells that can divide to renew themselves or produce specialized cells.
🟠 Pluripotent stem cells come from embryos or reprogrammed adult cells and can form all adult cell types.
🟠 Adult stem cells are tissue-specific and support repair in the organ where they are found.
🟠 In the lab, scientists culture stem cells using nutrient media, surface coatings, and repeated passaging.
🟠 Researchers make iPSCs by activating certain genes in mature cells, reversing them to a pluripotent state.
🟠 Differentiation is controlled by adjusting the environment, surface, or gene activity to guide cell development.
🟠 Scientists confirm stem cell identity by checking markers, growth behavior, and ability to specialize.
What are stem cells and how do they divide?
Stem cells are cells that copy themselves and make specialized cells your body needs. You can find them in early embryos and in many adult tissues. They stay active over time, especially when your body repairs damage or grows new tissue. Every time they divide, they can either stay stem cells or become cells with specific jobs.
Stem cells divide in two main ways—symmetrically and asymmetrically. Symmetric division makes two identical stem cells or two specialized cells. Asymmetric division makes one stem cell and one cell that starts to specialize. This way, your body keeps a supply of stem cells while also producing cells that perform specific functions.
Types of cell division:
- Two stem cells
- One stem cell and one specialized cell
- Two specialized cells
Cells respond to signals around them to decide which type of division to perform. These decisions affect how your tissues grow, heal, and stay balanced.
Compare Pluripotent and Adult Stem Cells
You can group stem cells into two types—pluripotent stem cells and adult stem cells. Pluripotent stem cells include embryonic stem cells and induced pluripotent stem cells (iPSCs). They come from early embryos or are reprogrammed from mature cells. These cells can turn into any cell type found in the adult body.
Adult stem cells (also called somatic stem cells) exist in organs like bone marrow or skin. They usually replace cells in the tissue where they are found, so they form fewer types of cells.
In the lab, pluripotent stem cells grow well and can divide for a long time without changing. Adult stem cells don’t divide as often and lose their ability to renew over time. These differences affect how both types are used in research.
Pluripotent vs. Adult Stem Cells
| Property | Pluripotent Stem Cells | Adult Stem Cells |
| Origin | Embryos or reprogrammed cells | Specific tissues (e.g. skin) |
| Potency | Any adult cell type | Limited to tissue lineage |
| Culturing in lab | Long-term renewal | Limited growth in culture |
Where Stem Cells Are Found in the Body
You can find stem cells in several tissues, but their location and behavior vary. In embryos, stem cells are located in the inner cell mass of the blastocyst. These cells can form all adult cell types and are the source of embryonic stem cell lines.
In adults, stem cells exist in specific tissues. Bone marrow contains hematopoietic stem cells, which form red and white blood cells. The skin holds epidermal stem cells that produce new layers. You’ll also find them in the gut lining, which renews rapidly. Even in the brain, some regions maintain neural stem cells that can form neurons and support cells.
These tissues are known as “niches.” Each niche controls how stem cells behave. For example, bone marrow niches regulate how many blood cells your body makes. Outside these niches, stem cells behave differently or stop dividing.
Scientists isolate stem cells from these tissues using careful extraction techniques. In research, they often use bone marrow, umbilical cord blood, and dental pulp as sources. Embryonic stem cells come from early embryos, while iPSCs are made from adult cells.
What Makes a Stem Cell “Potent”
Stem cells don’t all have the same flexibility. Potency describes how many different cell types a stem cell can become. The more potent the cell, the more types it can generate.
Pluripotent stem cells are very flexible. They can form all adult tissue types, from skin to neurons. Embryonic stem cells and iPSCs are examples. These cells are used when researchers need to model complex tissue development or grow many types of cells in the lab.
Multipotent stem cells are more limited. Adult stem cells fall into this group. For example, hematopoietic stem cells in bone marrow can become several blood cell types but won’t turn into skin or liver cells.
Oligopotent stem cells form even fewer cell types. A stem cell in the immune system might form only B cells or T cells. Unipotent cells can form just one cell type, though they still count as stem cells if they self-renew.
Potency depends on gene activity. Highly potent cells keep genes active that support many fates. As potency drops, more genes turn off, and the cell becomes more specialized.
By choosing cells based on potency, scientists decide which ones to use for different lab tasks. High-potency cells give flexibility, while lower-potency ones are useful when specific results are needed.
How Stem Cells Are Cultured in Laboratories
Scientists grow stem cells under controlled conditions called cell culture. They begin by placing cells into dishes filled with a nutrient-rich solution called culture medium. This solution provides sugars, amino acids, salts, and growth factors that support cell survival and division.
Stem cells usually attach to the dish surface. As they multiply, the space becomes crowded. At this point, researchers transfer a portion of the cells into a new dish with fresh medium. This step is called subculturing or making a new passage. Tracking the passage number helps monitor cell behavior over time.
To store stem cells long-term, scientists freeze them in liquid nitrogen. These frozen samples can be thawed later and grown again in fresh medium.
- Plate stem cells in a dish with culture medium
- Let cells divide until the surface is crowded
- Transfer cells into a new dish (subculturing) for continued growth
How Scientists Reprogram Cells into iPSCs
To make induced pluripotent stem cells (iPSCs), scientists start with mature cells, like skin cells. These cells have fixed functions. To reverse this, researchers insert specific genes that act as switches. These genes restart a program that resets the cell’s identity.
The cell stops acting like a skin cell and begins to divide and behave like a pluripotent stem cell. Its shape changes, and it reactivates genes found in early embryonic cells. This process takes time—often a few weeks—and must be done under controlled lab conditions.
How Scientists Test Stem Cell Identity
Once reprogrammed, iPSCs can divide many times and develop into different types of specialized cells. Scientists use these cells to study development or produce tissues in the lab.
How Scientists Trigger Stem Cell Differentiation
Stem cells can remain undifferentiated if they grow under specific lab conditions. To make them specialize, scientists change those conditions. They may use new growth media, coat the surface with certain molecules, or activate genes that guide development.
One method is spontaneous differentiation, where cells develop randomly once growth signals are removed. Another method is directed differentiation, where researchers guide cells to form specific types using exact steps and known signals.
These methods help researchers study how cells develop and produce specific tissues in the lab.
To confirm a cell line contains stem cells, scientists run a set of checks. They start with gene expression. Stem cells express certain genes that other cells don’t. If these markers are missing, the cells are likely not stem cells.
Next, they look at how fast the cells divide. True stem cells can replicate many times without changing. They also check the chromosomes under a microscope to make sure the genome stays stable.
Finally, they induce differentiation. They remove the signals that keep the cells undifferentiated and wait. Real stem cells will start forming specialized cell types.
How Stem Cells Are Used in Cell-Based Procedures
In lab-grown tissues, stem cells must meet a series of conditions. First, they need to multiply. You can’t build tissues from just a few cells, so researchers expand the cell population in culture.
Next, the cells must survive once moved. They need to stick to other cells, function, and avoid breaking apart. The lab also tests whether they can connect with nearby tissue and behave like part of the system.
Immune rejection is another issue. To reduce it, researchers often match the stem cells to the recipient or adjust them. Only well-tested, stable cells are used to build new tissue models.
Tutoring Help: Get Clear on Stem Cells with a Real Person
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Stem cells: Frequently Asked Questions
1. What are pluripotent stem cells?
Pluripotent stem cells can become any adult cell type in the body.
2. What is the difference between adult stem cells and pluripotent ones?
Adult stem cells form only specific tissue types, while pluripotent ones form all adult tissues.
3. How do stem cells divide?
They divide symmetrically or asymmetrically to renew themselves or create specialized cells.
4. What is a stem cell passage?
A passage is when cells are transferred to a new dish after they grow too crowded.
5. How do scientists grow stem cells in culture?
They use nutrient-rich media and special surfaces to help the cells attach and divide.
6. What are induced pluripotent stem cells (iPSCs)?
iPSCs are mature cells reprogrammed to behave like pluripotent stem cells.
7. How do scientists trigger stem cell differentiation?
They change the media, surface, or add specific signals to guide cell development.
8. How do you test if a cell is a true stem cell?
You check its gene markers, division rate, chromosomes, and ability to differentiate.
Sources:
1. Britannica
2. NIH
3. Wikipedia
