Skin forms ‘suspension bridges’ for wound healing

A new study on skin tissue mechanics published in Nature Materials today demonstrates how layers of human keratinocytes (outer skin cells) form structures not unlike suspension bridges over wounds to help the healing process.

Scientists at Barcelona’s Institute for Bioengineering of Catalonia (IBEC) and their colleagues at the Mechanobiology Institute of the National University of Singapore used microfabricated technology – miniature structures at micrometer scales – to look at how skin cells migrate to fix gaps or wounds. They showed that these regions, which have no extracellular matrix support and thus are not conducive for cell adhesion, which is essential for cell movement, are spanned by suspended multicellular “bridges” formed by layers of keratinocytes. Migrating skin cells are then able to continue to march forward as a united and homogenous group to form a protective barrier over the wound.

“These bridges are a brand new discovery. It was previously thought that this process of re-epithelialization – the restoration of skin on a wound or burn – required a ‘foothold’ for the cell sheets to successively migrate,” explains Xavier Trepat, group leader at IBEC. “Instead, it appears that the cells do something akin to slinging a rope or a bridge over the gap to then move across it.”

The study, which was led by Lim Chwee Teck and Benoit Ladoux in Singapore, found that this suspended cell sheet is made possible through the build-up of large-scale tension activated by acto-myosin, a kind of motor protein that can cause contraction in cells. They found the sheet to be elastic in behaviour, rather than fluid like other cell types, which partly explains its ability to form multicellular suspension bridges.

“Our study will hopefully pave the way for designing better tissue repair and regeneration alternatives that can overcome current limitations in skin tissue engineering and promote satisfactory skin regeneration,” adds Benoit Ladoux. “Potential applications include treating burns, certain skin diseases and ageing problems such as ulcers, as well as helping us characterize the mechanical properties of cell sheets.”

Reference article: Sri Ram Krishna Vedula, Hiroaki Hirata, Mui Hoon Nai, Agustí Brugés, Yusuke Toyama, Xavier Trepat, Chwee Teck Lim, Benoit Ladoux (2013).
Epithelial bridges maintain tissue integrity during collective cell migration. Nature Materials, in press