Honeycomb to mend a broken heart

2017-07-08 05:00:17

By David Robson A biodegradable honeycomb laced with stem cells could help broken hearts mend themselves. The polymer patch could one day lay down a pathway in areas damaged by heart disease for cells to regenerate and regrow, while the mesh itself slowly disintegrates within the body. Such “tissue scaffolds” already exist to regenerate cartilage tissue. Heart tissue is more difficult to grow artificially, however, because the cells must be aligned in the same direction as existing fibres for the heart to beat properly. Previous attempts had left the cells growing in a more haphazard fashion. A team from the Harvard-MIT Division of Health Sciences and Technology and the Draper Laboratory in Cambridge, Massachusetts, attempted to solve this by building a honeycomb scaffold that mimics the structural properties of heart tissue. The scaffold is made from a polymer sheet and zapped with a laser to form a honeycomb structure of individual pores, each shaped like a concertina roughly 500 micrometres long. The team seeded the walls of the honeycomb with heart cells from 2-day-old rats and incubated the patch in an oxygen- and nutrient-rich solution for a week. Microscope images showed that the cells had begun to proliferate. “They had oriented themselves along the long axis,” says Lisa Freed, who led the team. The team think this is because the cells build up layers starting from the walls and growing towards the centre. With the honeycomb shape, this eventually led to an oval ring of cells within the pore – with the majority aligned along the long axis. A similar honeycomb, made from squares rather than tiny “concertinas”, had no such preferred direction. The cells had also formed electrical connections with one another, allowing them to contract in coordination – and when an electric field was applied along the long axis of the honeycomb, the cells indeed contracted. “You could see the cells ‘beating’ on the scaffold,” says George Engelmayr, who also worked on the scaffolds. When an electric current was applied along the perpendicular axis, the cells did not contract so readily. This replicates the way healthy heart tissue will contract in only one direction. For the moment, the team believe the technology could be used to grow artificial heart tissue for screening new drugs to regulate heart activity. But in the future, the scaffold could be inserted into the body to repair damaged tissue. Since the honeycomb is flexible and stretches like heart tissue, the patch should be able to be integrated without causing additional damage. Julia Polak from Imperial College London in the UK believes this is a big step towards creating a scaffold for damaged heart tissue. However, she points out that it could be tricky to ensure the patch exactly matches the alignment of fibres within the recipient’s heart. Journal reference: Nature Materials (DOI: