Medical Uses and Therapeutic Cloning

From stem cells to replacement tissue

A stem cell is unspecialised. It can divide to produce more cells and some of its descendants can differentiate into specialised cells. This creates the possibility of replacing cells that have been damaged, destroyed or lost through disease.

The intended sequence is:

1. suitable stem cells are obtained;
2. they divide to increase their number;
3. they are encouraged to differentiate into the required specialised cell type;
4. the cells are transplanted into the patient, where they may replace damaged or missing cells.

The important idea is not simply that stem cells divide. The cells produced must become the right specialised cells and perform the function that the patient has lost. Detailed knowledge of the laboratory techniques used to obtain, grow or control the cells is not required for this course.

How treatment might help diabetes

In type 1 diabetes, the pancreas does not produce enough insulin. Insulin is needed to control blood glucose concentration. Stem cells could be made to differentiate into insulin-producing pancreatic cells and then transplanted into the patient.

If the transplanted cells survived and functioned correctly, they could produce insulin and improve control of blood glucose concentration. This is why stem-cell treatment may help diabetes. It should not be described as a certain or universally available cure.

How treatment might help paralysis

Paralysis can result when nerve cells in the brain or spinal cord are damaged, so nerve impulses cannot travel normally from the brain to muscles. Stem cells could be made to differentiate into nerve cells and transplanted into the damaged area.

The hope is that replacement nerve cells could repair some of the damaged nervous tissue and help restore communication with muscles. Nervous tissue is complex, however, so the potential to help does not mean that every injury can already be repaired.

Stem cells may therefore help different conditions by the same broad principle—replacing cells—but the specialised cell required depends on the problem. Diabetes would require functioning insulin-producing cells, whereas paralysis would require nerve cells capable of contributing to working nervous pathways.

Why ordinary transplants can be rejected

Cells carry molecules determined by their genes. If transplanted cells come from another person, the patient’s immune system may recognise them as foreign and attack them. This is rejection, and it can prevent the transplanted cells from surviving and working.

Doctors may try to reduce rejection by finding a closely matched donor or by using medicines that suppress the immune system. Suppressing immunity has a disadvantage: it can reduce the patient’s ability to fight infection.

Therapeutic cloning produces a genetic match

In therapeutic cloning, an embryo is produced with the same genes as the patient. Stem cells are taken from this embryo and can be made to differentiate into specialised cells for treatment.

Because these stem cells have the same genes as the patient, the patient’s body does not recognise them in the same way as genetically different donor cells. They are therefore not rejected by the patient’s body. This could allow replacement cells to be used without relying on a separate matching donor and could avoid the need for immune-suppressing medicines.

The essential GCSE link is:

same genes as the patient → cells are genetically matched → no rejection by the patient’s body → possible use in medical treatment

You need to understand this purpose and benefit, rather than memorise the detailed laboratory technique used to produce and culture the embryo.

Therapeutic cloning is called therapeutic because its purpose is to obtain cells for treating the patient. The intended product is replacement tissue, not the birth of a cloned individual.

Medical use

Stem cells can divide and differentiate into specialised cells. The proposed treatment pathway is:

stem cells → required specialised cells → transplantation → replacement of damaged or missing cells

• Type 1 diabetes: produce insulin-producing pancreatic cells to improve control of blood glucose.
• Paralysis: produce nerve cells that may help repair damaged nervous tissue and restore signalling to muscles.

These treatments may help; they are not guaranteed cures. Detailed stem-cell techniques are not required.

Therapeutic cloning

• An embryo is produced with the same genes as the patient.
• Embryonic stem cells are obtained and used to produce cells for treatment.
• The cells are genetically matched to the patient.
• Therefore, the patient’s body does not reject them.

Recall chain: same genes → genetic match → no rejection → possible medical treatment.

Do not confuse therapeutic cloning with producing a cloned individual: its purpose here is to obtain stem cells for treatment.