Stem cells can regenerate tissues, replace damaged cells, and model diseases. They could even be used to grow whole organs for transplant. However, each type of stem cell brings its own ethical, technical, and biological implications.

Embryonic Stem Cells (ESCs)

Advantages

• Pluripotent: Can differentiate into any body cell - ideal for repairing a wide range of tissues.
• Large supply from embryos (e.g. in IVF clinics).
• Can be grown and maintained relatively easily in culture.

Disadvantages / Issues

• Ethical concerns: Requires destruction of human embryos - some view this as destroying potential life.
• Risk of immune rejection: Cells are genetically different from the recipient.
• Risk of tumour formation: Due to their high rate of cell division.
• Legal and funding restrictions in some countries due to ethical debate.

Example Uses

• Retinal repair in macular degeneration.
• Generation of insulin-producing beta cells for diabetes.

Adult Stem Cells

Advantages

• Fewer ethical concerns: No embryos are used.
• Can be obtained from the patient’s own body (e.g. bone marrow), so no risk of rejection.
• The adult can give consent to use their stem cells.
• Already in use - e.g. bone marrow transplants are standard treatments for blood cancers.

Disadvantages / Issues

• Multipotent, not pluripotent: Limited to forming specific cell types (e.g. blood, skin).
• May accumulate mutations with age or be less effective in older patients.
• Scarcity: Some tissues have very few accessible stem cells.

Example Uses

• Bone marrow transplants.
• Experimental treatments for heart disease using cardiac stem cells.

Induced Pluripotent Stem Cells (iPS Cells)

Advantages

• Pluripotent: Like embryonic stem cells, can differentiate into most body cell types.
• Created from adult somatic cells - no embryo destruction required.
• Body cells can be taken from the patient themselves, reducing risk of immune rejection and they can provide consent.

Disadvantages / Issues

• The reprogramming process is complex and often does not work.
• Uses viral vectors that may randomly integrate into the genome, causing mutations or disrupting genes that regulate the cell cycle (such as tumour suppressor genes).
• Increases cancer risk.
• Cells may lose stability over time or differentiate unpredictably.

Example Uses

• Potential for treating Parkinson’s, type 1 diabetes, and spinal cord injuries.
• In vitro disease modelling and drug testing.