Biologists at the University of Sheffield’s Centre for Stem Cell Biology led by Professor Peter Andrews and engineers in the Complex Systems and Signal Processing Group led by Professor Daniel Coca have completed a landmark study of human pluripotent stem cells.

The cells are candidates for a new generation of regenerative medicine because they have the ability to produce any cell type in the body.

Use of these stem cells in therapies is currently limited because they can acquire disadvantageous genetic changes during prolonged culture and in some cases develop the characteristics of mutations in cancer cells.

Researchers at Sheffield used time-lapse imaging of single human embryonic stem cells to observe their behaviour and identify factors that restrict growth as well as factor that enable cells to grow more efficiently.

Dr Ivana Barbaric, from the University of Sheffield’s Department of Biomedical Science, said: “So-called pluripotent stem cells have huge potential for use in regenerative medicine due to their ability to become any cell in the human body. What we need to understand are the subtle influences and processes that cause stem cells to behave in very different ways. Through closer observation we have discovered that cells have individual traits. Our understanding is analogous to moving from a high altitude view of society to one that looks at the characteristics of close family units.”

Currently cells tend to die extensively during culturing and they can mutate spontaneously.

Some of these genetic mutations are known to provide stem cells with superior growth capabilities, enabling them to overtake the culture – a phenomenon termed culture adaptation, which mimics the behaviour of cancer cells.

Cell proximity may be a factor in development, the research found.

Professor Peter Andrews said: “In a sense we appear to be seeing cells make ‘vocational choices’ depending on their immediate environment. These choices appear to be influenced by near neighbours, leading us to believe that there is something akin to ‘teaching’ that can occur between neighbouring cells as they develop. The focus of our research now will be to examine the molecular mechanisms that control these choices. Instead of taking a herd view in our research, we are focusing our efforts on what happens at individual cellular level.”

The team’s research combined the use of time-lapse microscopy, single-cell tracking and mathematical modelling to identify development stages that affect the survival of normal human embryonic stem cells and compared them with adapted cells.

They identified three major bottlenecks affecting colony formation: survival after plating, failure to re-enter into cell cycle and continued cell death after division.

In the same culture condition, they found adapted cells performed better in all of these points leading to more colonies.

Bottlenecks were also alleviated through cell to cell contact and pro-survival compounds.

Dr Veronica Biga, from the University’s Automatic Control and Systems Engineering Department, said: “To extract information about cell death, mitosis and movement, we developed new methods for analysing images and measuring numerous parameters from time-lapse videos.”

She added: “We plan to further develop the methods from this study into an image processing and analysis software solution to be used for monitoring cell behaviour in applications such as screening culture conditions, drug discovery, monitoring and minimising the occurrence of genetic abnormalities directly through time-lapse.”

Source: University of Sheffield