back pain
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An injection could finally bring relief to millions of people with chronic lower back pain. If it works, the stem cell treatment could be a crucial tool for fighting the opioid epidemic killing thousands in the US.

Opioids accounted for 33,000 deaths in the US in 2015 alone. Many of those deaths occur as a result of people becoming addicted to opioids prescribed for lower back pain, which affects around 28 million people in the US and accounts for around half of all opioid painkiller prescriptions there.

Stem cells might change that. Injected into damaged discs between the vertebrae of the spine, each dose contains around 6 million cells. Called mesenchymal precursor cells, they dampen down inflammation and secrete factors that help rebuild damaged tissue.

In experiments in sheep, these cells completely rebuilt damaged vertebral discs, prompting Silviu Itescu of the firm Mesoblast in Melbourne, Australia, and his team to try the technique in people. "In 100 patients, we've shown substantial improvements in function and pain relief that last two years or more," he says.

Reinflated discs

MRI scans found that the cells do seem to rebuild damaged discs in people. "If we're successful in [our] larger trial currently under way, we can hopefully keep people away from opioids," says Itescu.

The cells are being tested specifically for treating degenerative disc disease, which accounts for around 22 per cent of cases of chronic lower back pain. The discs between our vertebrae act as shock absorbers, but they can dry out through wear and tear or ageing. This causes them to shrink, reducing their cushioning power, and potentially leading to trapped nerves. Disc injury can also trigger inflammation that further aggravates the condition.

One injection of the cells was enough to help stop back pain for two years in around half of those treated. Some participants have now been free of pain for three years.

Almost half of those treated became more mobile, dropping 15 points on a 100-point "disability" scale. Fewer than 13 per cent of the control group, who received a salt-water injection, showed the same improvement. The company presented these preliminary results at a meeting of the US Spine Intervention Society in New Orleans in August, and will give more detail in November at the Piper Jaffray Healthcare Conference in New York.

The stem cells are extracted from donor bone marrow, and then grown in the lab to create large amounts for treating many people. Itescu says donated mesenchymal precursor cells aren't recognised by a recipient's immune system, meaning that someone who receives the treatment does not need to take immunosuppressant drugs.

The injected cells then reinflate vertebral discs that have dried out and cracked, losing their strength, says Itescu. They do this by causing water to be trapped in the discs, "almost like pumping up a tyre," he says.

The rationale makes sense, says David Thomas of the opioid and pain working group at the US National Institute on Drug Abuse in Maryland. He says other teams are developing promising treatments for lowering inflammation in painful discs.

In August, President Trump said he will declare the US opioid crisis a national emergency. As New Scientist went to press, a further announcement was expected imminently. But the problem isn't restricted to the US, and there are fears that a similar painkiller addiction epidemic is under way in the UK. Codeine-related deaths have more than doubled in Australia since 2000.

Caleb Alexander of the Johns Hopkins Bloomberg School of Public Health in Maryland says existing alternatives to opioids - such as non-steroidal anti-inflammatory drugs and physical therapy - have more immediate potential for alleviating the epidemic than new treatments. "Any practical application of these types of treatments is a long way off, and there are countless reasons why these promising early results may not translate into tomorrow's cures," he warns.

But Thomas says existing back pain treatments often fail or are only minimally effective. "We really do need better treatments for lower back pain, so this is encouraging," he says. "But we need to see how it works out."