Scientists in Singapore have developed an injectable hydrogel that could be used to regenerate cartilage in injured patients.

When the modified gellan gel is loaded with cells it promotes cartilage growth faster than agarose gels

Dong-an Wang and colleagues at Nanyang Technological University modified gellan gum, a widely used polysaccharide food additive, to transform it into a cell-carrying hydrogel. Cell-containing hydrogel solutions can be injected into target sites in the body, where they are cooled to form cell-laden gels that encourage tissue regeneration. But gellan forms a hydrogel at temperatures higher than body temperature and so until now, has been unsuitable for tissue engineering because it can't be injected as a solution.

Wang chemically cut gellan molecules to reduce their size. He found that the shorter molecules formed a hydrogel when below body temperature. Wang loaded the gel with cells and monitored its ability to promote tissue regeneration in vitro. The gellan-based gels were faster at promoting cartilage growth than agarose gels, which are widely used in tissue regeneration.

So far, Wang has only tested the gels in vitro but he predicts that the technology will transfer to patients. 'We believe our scaffolding system promises to bridge the gap between bench and bedside,' he says. 'One could envisage a cell-carrying gellan solution being injected into any randomly shaped venues, forming gels in situ that encapsulate therapeutic cells working on tissue regeneration.' Wang says he also plans to investigate the degradation properties of modified gellan.

'Many approaches to regenerate cartilage tissue in the clinic have failed in the past,' comments Matthias Lutolf, who investigates the interface between biomolecular engineering and adult stem cell biology at the Swiss Federal Institute of Technology, Lausanne. 'It will be interesting to see how this technology performs in a more relevant in vivo scenario, for example in a rabbit model.'

Vikki Chapman

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