TO TURN stem cells into specialised cells, such as neurons, researchers usually face the daunting task of teasing out which one of a vast range of growth agents drives each step of the process. But it may be possible to drive the process without knowing which growth factors are involved.
The surfaces of cells are dotted with complex sugars, including heparan sulphate (HS) glycosaminoglycan sugars, which help form 鈥渟ignalosomes鈥� that trap growth factors and line them up with receptors. The structure of the HS sugars changes according to a cell鈥檚 need for different growth agents. 鈥淲e don鈥檛 know the full combination of growth factors needed at each step of differentiation, but the cells do,鈥� says Victor Nurcombe of the University of Queensland in Brisbane.
Identifying the sugars is simpler than identifying the soup of growth factors that cells secrete to stimulate their own development, and that of cells nearby, Nurcombe says. Then the sugars can be used to amplify the effects of known or unknown factors.
Advertisement
Working with Apollo Life Sciences of Sydney, Nurcombe鈥檚 team has developed a way of using HS sugars to convert stem cells into bone. First they purify HS sugars from the surface of the cells involved in each step of bone production: bone stem cells, preosteoblasts and osteoblasts. When these HS sugars are added to a flask of stem cells or preosteoblasts, bone is produced in a matter of days rather than weeks. And when the sugars are added to a gel and applied to broken bones in rats, they speed up bone regeneration by 18 per cent, Nurcombe told a stem cell conference in Melbourne earlier this month.
鈥淎nd if we can do it for bone, we should be able to do it for other tissues,鈥� he says. Nurcombe hopes to develop an intelligent material that would release different HS sugars in sequence to drive differentiation of, say, brain tissue or heart tissue.