Fat Cells Tapped for Spinal Fusion

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Researchers at Johns Hopkins Medicine have come up with a method that uses adipose cells, better known as fat, as a practical and plentiful source of stem cells for use in spinal fusion surgeries.

Spinal fusion ‘welds’ two or more vertebrae together so that they heal into a single, solid bone. Unfortunately, the surgery — using bone taken from other parts of the patient’s body — fails in up to a fifth of procedures. Stem cells, harvested from a patient’s marrow and allowed to mature into bone cells, can improve the outcome of spinal fusions. However, the aspiration method for getting stem cells out of the marrow carries an infection risk and often is painful.

In a study published in the journal Spine, researchers sought to try out adipose cells rather than bone marrow as a source for the stem cells.

Performing spinal fusion procedures in rats, the researchers found that freshly isolated stem cells from fat worked just as well as the more commonly used bone marrow stem cells. The researchers say this suggests the technique could be a candidate for human clinical trials.

“Bone marrow stem cells are isolated in human patients from the hip,” said Christina Holmes, PhD, a former Johns Hopkins Medicine postdoctoral fellow now at Florida State University. “But using a huge needle to take out bone marrow is a painful procedure, and we can only get a limited number of cells, so we’ve found an alternative source by using stem cells from fat.”

Alexander Perdomo-Pantoja, MD, a postdoctoral fellow at the Johns Hopkins University School of Medicine, said spinal fusion procedures are used to treat many different conditions.

“Spinal fusions are used for anything that causes spinal instability, which usually produces significant mechanical pain,” he says. “You see it frequently when we get older as the intervertebral discs, ligaments and muscles in the spine deteriorate. But these procedures can also be used to treat instability when it is caused by tumors, fractures, deformities or trauma.”

The researchers isolated stem cells from fat and bone marrow, and implanted them into rat spines. For the adipose-derived stem cells, the researchers used freshly isolated cells to see if they could speed up and simplify the procedure.

Stem cells are currently sourced either from bone marrow or fat and are often grown in a lab culture to mature them enough for spinal fusion. During culturing, there is a risk of contamination or transformation into unusable bone. Holmes said that freshly isolating cells avoids these problems, along with reducing labour and material costs.

While stem cells from fat are commonly used in cosmetic procedures, they are not often used in spinal fusions, she adds.

“We feel that fat cells are a logical alternative to bone marrow cells because most patients have an adequate supply of fat cells,” Tsaid imothy Witham, MD, director of the Johns Hopkins Neurosurgery Spinal Fusion Laboratory. ”Fat also is much more accessible during surgery and can be harvested with less stem cell death than bone marrow. Spinal fusion is a very common procedure, and we feel this approach could be applied across a wide cohort of spinal fusion patients.”

The researchers found significantly more bone formation and blood supply in the fresh adipose-derived stem cells compared with what they saw in previous studies with cultured cells from both fat and bone marrow.

The next step for Witham and his team is identifying which cells are the most advantageous for spinal fusions and then characterising them.

Source: John Hopkins University

Journal information: Alexander Perdomo-Pantoja et al. Comparison of Freshly Isolated Adipose Tissue-derived Stromal Vascular Fraction and Bone Marrow Cells in a Posterolateral Lumbar Spinal Fusion Model, Spine (2020). DOI: 10.1097/BRS.0000000000003709

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