THE SCIENCE OF STEM CELLS
A fertilised embryo that nestles into the uterine wall holds mammoth amounts of potential. The cells destined to become a foetus at that moment all look alike and number in the mere hundreds. Yet the organism that will arise from this small enclave will one day boast trillions of cells and be composed of a plethora of specialist cell types. How can the multitude of different cell types that make up our eyes, brain, lungs and skin come from such a small number of similar cells? The answer to this exponential increase in complexity and specialisation comes from stem cells.
Every cell in the human body contains all the genetic information needed to perform any role. But for our bodies to develop and function efficiently, we need skin cells to behave like skin, and for muscles to behave like muscles. For this to happen our cells become specialised, or differentiated, into particular cell types, meaning they only use a part of the genetic information available in their DNA.
However, all cell types begin their existence as stem cells, undifferentiated cells that have the potential to become many different cell types. Embryonic stem cells are there at the origin of our developmental journey. As the embryo grows and develops into a foetus, chemical signals received by the stem cells begin their journey of differentiation, sealing their fate to become certain cells by silencing and unlocking specific parts of their DNA.
The malleable power of stem cells also represents remarkable opportunities for those who can harness them. As well as being able to recover embryonic stem cells from early embryos, recent advances have discovered the cellular signals needed to convert differentiated cells back into their unspecialised states. This provides multiple means for scientists to take a cell and transform it into any cell type of their choosing. Research is underway to grow entire transplant organs for a patient from their own cells, and we can even utilise stem cells to generate egg and sperm cells that give rise to new life.