Induced Pluripotent Stem Cells (iPS)
Laura Armstrong
Teacher
Contents
Recall Questions
This topic requires prior knowledge of stem cells from A-level Biology. You can test your knowledge below.
What are pluripotent stem cells?
Stem cells that can differentiate into any body cell type, but not extraembryonic cells like the placenta.
What is the main difference between embryonic and adult stem cells?
Embryonic stem cells are pluripotent, while most adult stem cells are multipotent or unipotent.
What is meant by cell differentiation?
The process by which stem cells become specialised by expressing certain genes and silencing others.
Topic Explainer Video
Check out this @JoeDoesBiology video that explains induced pluripotent stem cells (iPS) or read the full notes below. Once you've gone through the whole note, try out the practice questions!
What Are Induced Pluripotent Stem Cells (iPS Cells)?
iPS cells are adult somatic (body) cells (e.g. skin or blood cells) that have been genetically reprogrammed to behave like pluripotent embryonic stem cells.
They have the ability to differentiate into most types of body cells and offer an ethical alternative to using embryonic stem cells.
How Are iPS Cells Made?
- Adult body cells (e.g. skin cells) are extracted.
- Scientists insert genes into the cells that code for key pluripotency-inducing proteins.
- These proteins are called transcription factors and can bind to DNA (at a region known as the promoter region) to initiate transcription of genes that were previously not expressed in the body cell.
- The inserted genes reprogram the adult cell, causing transcription of genes that are active in embryonic stem cells, switching on gene expression.
- The cell returns to a pluripotent state, forming an iPS cell.
The reprogramming is often achieved using viral vectors to deliver the genes for transcription factors into the body cells.
What Are iPS Cells Used For?
| Application | How iPS Cells Help |
| Disease modelling | iPS cells can be used to grow human tissues with genetic diseases in vitro. |
| Drug testing | Safer, more accurate testing on patient-specific cells instead of animal models. |
| Regenerative medicine | Can generate patient-matched cells for tissue repair (e.g. heart, nerve, retina). |
| Regenerative medicine | Cells from a patient can be used to develop treatments without immune rejection. |
Pros and Cons of iPS Cells
| Pros | Cons |
| Avoids ethical issues of using embryos, no embryos will be destroyed. | Risk of cancer/tumours due to genetic manipulation |
| Can be made from the patient’s own cells with their own DNA → no immune rejection. | Some iPS cells exhibit poor differentiation quality indicating incomplete reprogramming |
| Can be used for disease modelling and drug development. | Use of viral vectors may cause infections |
| IPs cells are pluripotent so can differentiate into all body cell types. |
Genetic Instability During Reprogramming
- The reprogramming process can disrupt the cell’s genome.
- Viral vectors may insert DNA randomly into the genome.
- This can:
- Disrupt tumour suppressor genes
- Activate oncogenes
- Cause mutations
These genetic changes may alter cell cycle regulation, leading to uncontrolled division, a hallmark of cancer.
Stem Cells Are Highly Proliferative
Even without mutations, stem cells, including iPS cells, naturally have a high rate of cell division. If regulation fails, this rapid growth can contribute to tumour formation.
Key Terms
- iPS Cells: Induced pluripotent stem cells reprogrammed from adult cells.
- Transcription Factor: A protein that switches gene expression on during cell programming.
- Pluripotency: The ability of a cell to differentiate into any body cell.
- Regenerative Medicine: The use of stem cells to repair or replace damaged tissues.
- Reprogramming: The process of converting a specialised cell back to an undifferentiated state.
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Exam Tip
Ethical comparisons come up regularly - make sure to highlight advantages over embryonic stem cells in extended responses, but stick to the facts! For example, using this method, no embryos are destroyed and there is less chance of rejection/immune response.
No answer provided.
Describe how induced pluripotent stem cells are produced and give one advantage and one disadvantage of their use in medicine. (5 marks)
- Adult somatic cells (e.g. skin cells) are extracted.
- Genes coding for transcription factors are introduced using a viral vector.
- These transcription factors initiate transcription of genes/ switch on gene expression.
- Advantage: iPS cells avoid ethical issues as no embryos are destroyed.
- Disadvantage: Risk of forming tumours due to genetic modification.
Practice Question
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!