1 University College London Institute of Child Health, London, UK.
2 Centre for Stem Cells and Regenerative Medicine at King's College London, London, UK.
3 Department of Dermatology, Medical University of Vienna, Skin and Endothelium Research Division, Vienna, Austria.
4 Hubrecht Institute-Royal Netherlands Academy of Arts and Sciences (KNAW) and University Medical Centre (UMC) Utrecht, The Netherlands.
5 Unit for Cellular and Molecular (Patho)physiology, Inflammation Research Center, VIB, Ghent, Belgium and Department of Biomedical Molecular Biology, Ghent University, Ghent, Belgium.
6 Centre for Stem Cells and Regenerative Medicine at King's College London, London, UK. Electronic address: fiona.watt@kcl.ac.uk.