US scientists have found a way to grow new bone using fresh, purified stem cells from fat tissue that produces better quality bone faster than conventional methods. They suggest this may one day eliminate the need for painful bone grafts that use material taken from patients with invasive surgery.

They write about their work in the 11 June online first issue of a paper published in the new peer-reviewed journal Stem Cells Translational Medicine, which aims to span stem cell research and clinical trials.

The two co-senior authors of the study are Chia Soo, vice chair for research at University of California - Lost Angeles (UCLA) Plastic and Reconstructive Surgery, and Bruno Péault, professor of Orthopedic Surgery at UCLA. Both are members of the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA.

Soo told the press that fat tissue is considered a good source of mesenchymal stem cells, the sort that can be coaxed to form various tissue types such as bone, cartilage and muscle, because there is plenty of it and it is easy to get hold of with procedures like liposuction.

One conventional method of growing these stem cells from fat tissue relies on culturing the fat cells for weeks to isolate the stem cells that form bone. These processes can increase the risk of infection and lead to genetic instability.

Another traditional method, called stromal vascular fraction (SVF), uses fresh, non-cultured cells, but it is not easy to extract SVF cells from fat tissue because there are many kinds of them, not all capabale of forming bone.

For this study, the researchers isolated and purified human perivascular stem cells (hPSC) from fat tissue, and using lab animals, showed these cells are a better option for making bone than SVF cells.

They also showed that a growth factor called NELL-1, speeded up bone formation.

Soo told the press:

"People have shown that culture-derived cells could grow bone, but these are a fresh cell population and we didn't have to go through the culture process, which can take weeks."

"The best bone graft is still your own bone, but that is in limited supply and sometimes not of good quality. What we show here is a faster and better way to create bone that could have clinical applications," she added.

To show that their new approach can grow new bone, the researchers put the hPSCs with NELL-1 in a muscle pouch, where bone does not normally grow.

Using X-rays they were then able to show the cells did make bone.

Soo explained:

"The purified human hPSCs formed significantly more bone in comparison to the SVF by all parameters."

"And these cells are plentiful enough that patients with not much excess body fat can donate their own fat tissue," she added.

If further tests prove successful, then one day doctors may be able to quickly get high quality bone graft material from patients' fat tissue, purify it to get the hPSCs, and put them, with NELL-1, in the place where new bone is needed.

The new bone would then grow in situ inside the patient, eliminating the need for painful surgery to harvest the bone graft.

Soo said they envisage it may one day be possible to isolate the hPSCs, add the NELL-1, with a matrix or scaffold to help the new bone tissue adhere, and for it to take less than an hour.

Péault said recent studies have shown similar advances in using perivascular stem cells to regenerate various different kinds of tissue, including skeletal muscle, lung tissue, and even heart tissue.

"Further studies will extend our findings and apply the robust osteogenic potential of hPSCs to the healing of bone defects," he added.

Funds from the California Institute of Regenerative Medicine Early Translational Research Award and Training Grant Research Fellowship, a University of California Discovery Grant and the National Institute of Dental and Craniofacial Research Center at the National Institutes of Health, helped pay for the study.

Written by Catharine Paddock PhD