Medical uses and applications of stem cells Revision Notes | GCSE AQA Higher Biology

1. The Promise of Stem Cell Medicine

Imagine a treatment that could help paralysed patients walk again or cure diabetes without daily injections. This isn't science fiction — it's the potential of stem cell therapy. These remarkable cells hold the key to treating conditions that currently have no cure.

Think of stem cells as biological 'blank slates'. Unlike your muscle cells or nerve cells, which have fixed jobs, stem cells haven't decided what they want to be when they grow up. This flexibility makes them incredibly valuable for medicine.

The key property that makes stem cells so useful is their ability to differentiate — transform into any specialised cell type your body needs. Need new heart muscle after a heart attack? Stem cells can become cardiac muscle cells. Spinal cord damaged? They can become nerve cells.

2. Medical Conditions That Could Benefit

Stem cell treatments target conditions where the body's own cells are damaged, diseased, or destroyed. Two major examples show the potential:

Diabetes (Type 1): The immune system destroys insulin-producing cells in the pancreas. Patients need daily insulin injections to survive. Stem cells could be differentiated into new insulin-producing cells, potentially providing a permanent cure rather than lifelong management.

Paralysis from spinal cord injury: Damaged nerve cells in the spinal cord cannot regenerate naturally. This breaks the communication between brain and muscles below the injury. Stem cells could differentiate into new nerve cells, potentially restoring this vital connection.

Other conditions that could benefit include Parkinson's disease (replacing damaged brain cells), heart disease (replacing dead heart muscle), and blood disorders (replacing faulty blood-forming cells in bone marrow).

3. The Rejection Problem and Therapeutic Cloning

Here's the catch with stem cell treatments: your immune system is designed to attack foreign cells. If we transplant stem cells from another person, your body will likely reject them, just like it would reject an organ transplant.

Worked example: How Therapeutic Cloning Works

A patient needs stem cells that won't be rejected by their immune system. Explain the therapeutic cloning process.

1. Remove the nucleus (containing DNA) from one of the patient's body cells — This nucleus contains all the patient's genetic information
2. Take an egg cell from a donor and remove its nucleus — The empty egg cell provides the cellular machinery needed for development
3. Insert the patient's nucleus into the empty egg cell — The egg now has the patient's DNA and can develop into an embryo
4. Stimulate the egg to divide and develop into an early embryo — The embryo is genetically identical to the patient
5. Extract stem cells from the embryo after a few days — These stem cells have the patient's DNA so won't be rejected

Answer: The cloned stem cells are genetically identical to the patient, so the immune system recognises them as 'self' and doesn't attack them.

Trap: Many students think therapeutic cloning creates a whole cloned person. Actually, the embryo is only allowed to develop for a few days — just long enough to harvest stem cells. No cloned baby is produced.

4. Potential Risks of Stem Cell Treatments

Like any medical treatment, stem cell therapy carries risks that must be carefully weighed against potential benefits.

Transfer of viral infections: Stem cells might carry viruses that could infect the patient. This is particularly concerning because stem cells divide rapidly, potentially spreading any infection quickly throughout the body. Rigorous testing is essential but cannot eliminate all risks.

Uncontrolled cell growth: If stem cells don't differentiate properly or continue dividing when they should stop, they could form tumours. The same property that makes stem cells useful — their ability to divide indefinitely — also makes them potentially dangerous.

Immune reactions: Even with therapeutic cloning, there's still a small risk that the immune system might react to the stem cells, especially if they don't differentiate exactly as expected.

5. Ethical and Religious Concerns

The use of stem cells, particularly embryonic stem cells, raises significant ethical and religious questions that society continues to debate.

The status of embryos: Many people believe that human life begins at conception, making the destruction of embryos to harvest stem cells morally equivalent to taking a human life. Others argue that early embryos (especially those created specifically for research) don't have the same moral status as developed humans.

Religious perspectives: Different religions have varying views. Some see the potential to heal suffering as a moral imperative, while others believe that creating and destroying embryos violates the sanctity of life. These aren't just abstract debates — they influence government funding and legal regulations.

Alternative approaches: Scientists continue to explore ways of reducing ethical concerns around stem cell treatment.

6. Exam Technique and Common Mistakes

Stem cell questions often appear in 6-mark extended response questions. Here's how to structure your answer for maximum marks:

Common mistake: Students often confuse therapeutic cloning with reproductive cloning. Remember: therapeutic cloning produces stem cells for treatment, reproductive cloning would produce a whole organism (which isn't the goal here).

Mark-winning phrases: 'Genetically identical to the patient', 'won't be rejected by the immune system', 'differentiate into specialised cells', 'replace damaged or diseased cells'.