Stem cell research: Turning sugar into bone

University of Queensland scientist Assoc Prof Victor Nurcombe has moved to Singapore to continue his work on repairing bone fractures using sugars from the surface of cells.

Along with colleague Dr Simon Cool, Nurcombe has accepted a well-funded position at the Institute of Molecular and Cell Biology in Singapore's new Biopolis precinct where he hopes to take his novel ideas into the clinic.

Nurcombe is using the complex mix of heparin sulphate sugars (HS) to trigger bone regeneration. The project is a collaboration with UQ Institute of Bioengineering and Nanotechnology's Prof Matt Trau.

"Every lineage of cells has a characteristic sugar population on its surface, which performs very specific jobs, such as controlling growth factors and adhesive factors," he said. "The sugars bring together clusters of different molecules on the surface of the cell."

And by mixing these sugars with a synthetic scaffold, Nurcombe believes he can encourage new bone to grow, without resorting to the barbaric and infection-prone 'bicycle spoke' techniques currently used by orthopaedic surgeons to repair severe compound fractures. The use of sugars also circumvents the problems of using growth factors, which can be oncogenic.

Nurcombe has demonstrated that the HS from bone cells called osteoblasts can direct the differentiation of mesenchymal stem cells through the osteoblastic lineage. In rat experiments he showed that by combining HS with surgical gel and applying it to damaged bones, an 18 per cent increase in bone formed at the site of damage was observed compared to controls.

The researcher has been experimenting with a novel biomaterial known as PHBV (marketed as BioPol), which when mixed with hydroxyapatite forms a bone-like structure that gradually breaks down. But while the PHBV scaffold can be used to deliver HS, it has the unwanted side-effect of activating macrophages, which can cause an unwanted inflammatory response. Ultimately the technology could also be used to deliver cells to the site of repair as well.

Nurcombe plans to test a range of novel biomaterials for delivery of HS, using larger animals models with load-bearing bones to really prove the utility of the method. "The rat model doesn't have long load-bearing bones -- we need a larger model like sheep, goats or rabbits," he said.

Nurcombe said the technology could eventually be used to repair and regenerate more complex tissues, such as heart and kidney.