Could stem cells one day end hip replacement?

A new stem cell technique could make hip replacements “a thing of the past” for some patients, says The Independent.

Traditionally, people whose hip joint becomes worn or damaged over time need a mechanical implant fitted in place of their damaged joint. However, scientists are currently working on ways to repair the bone using stem cells. Stem cells are remarkable cells that can transform into virtually any other cell type found in the body. It’s hoped that developing new ways to cultivate stem cells into bone tissue could remove the need for hip replacements and complicated bone grafts.

Today’s news is based on the work of a group of researchers based in Southampton who have been looking at ways to improve the technique used in revision hip surgery (surgery after a first-time hip replacement). The possible techniques they are exploring include the use of biodegradable plastic scaffolds to grow stem cells into bone tissue, and the use of sterilised, crushed bone as a potential bone-building material. While their research is at an early stage, it does provide an example of what may be possible in the future.

Where did the story come from?

Today’s news is based on ongoing research and development into a way to repair hip joints, potentially reducing the need to perform conventional implant-based hip replacement surgery. The work has been discussed in a press release put out this week by University Hospital Southampton, although portions of the research have already been reported in peer-reviewed scientific journals.

This Behind the Headlines appraisal looks at recent research conducted by some of the team involved in this hip research, who are based at the University of Southampton Medical School and the University of Nottingham. It was funded by the Medical Research Council and published in the peer-reviewed journal Acta Biomaterialia.

What kind of research was this?

This was a laboratory-based study looking at whether the use of a plastic scaffold could allow stem cells to repair bones, thereby reducing the need for a technique called impaction bone grafting where grafted bone sections have to be forced into place. Impaction bone grafting is a technique that uses transplanted bone from another person (for example, another person who has had a hip replacement) to replace lost bone during revision hip surgery (surgery after a first-time hip replacement).

The authors state that, although this technique has been successful in some studies, it is associated with some problems, including cross-infection and rejection of the transplant. Availability is another problem, associated with the fact that the population is ageing and more and more people are likely to require this sort of treatment.

The aim of this study was to create a plastic scaffold that could be used in combination with a patient’s own skeletal stem cells to replace lost bone, in the area of the implant. A laboratory-based study is required for this sort of initial investigation. Once a suitable plastic scaffold is created, it will have to undergo further testing.

What did the research involve?

The researchers produced two biodegradable plastics, and moulded each plastic into two microscopic scaffolds using two techniques. One was a traditional technique and the other a new technique called 'supercritical CO2 fluid-foaming'. They produced four different scaffolds in total. These synthetic scaffolds were compared to human bone. Supercritical CO2 fluid-foaming is a technique that produces porous plastic structures.

The researchers looked at the scaffolds by scanning them with electron microscopes and performing computer tomography (X-rays). The mechanical properties of the scaffolds were then tested, for example to see if they could withstand the force applied during the impaction procedure. Finally, the researchers tested whether human skeletal stem cells could grow and develop into bone cells when grown in the laboratory with the scaffolds.

What were the basic results?

The researchers found that using the supercritical CO2 fluid-foaming technique produced a porous scaffold, whereas the traditional technique produced a rough and non-porous scaffold. All four synthetic scaffolds withstood the impaction procedure better than human bone, and the porous synthetic scaffolds maintained their shape well after impaction. Skeletal stem cells could grow on all four scaffolds, but they grew better on the porous scaffolds. Skeletal stem cells could develop into bone cells when they were grown on the porous scaffold made of one of the types of plastic.

How did the researchers interpret the results?

The researchers conclude that the plastic scaffolds were stronger than human bone, and that porous scaffolds made using the new method of supercritical CO2 fluid-foaming were better than the scaffolds formed using traditional methods.

Conclusion

This study has compared the properties of scaffolds made from biodegradable plastics, for their potential use in combination with skeletal stem cells to replace lost bone during hip surgery. This is currently performed using bone from a donor, for example someone else who has had part of their bone removed while undergoing hip replacement surgery.

However, traditional bone grafting carries the potential for the transmission of diseases and the risk of the transplanted material being rejected. These problems, and the possible lack of available donors, has prompted the search for alternatives. This laboratory-based study has investigated the mechanical characteristics and cellular compatibility of scaffolds made from two different plastics using two different techniques. The plastics had been found to have promising characteristics for this application in previous studies.

The study found that scaffolds made using a technique called supercritical CO2 fluid-foaming were porous, and had better characteristics for potential clinical applications than scaffolds made using more traditional methods. However, this work is continuing, and further studies are required before these plastics will be available.