The noninvasive use of ultrasound to modulate nerve activity and treat inflammatory arthritis and hyperglycaemia in rodent models is demonstrated in two studies this week. The papers, published in Nature Communications, suggest that this non-pharmacological approach could be used to treat inflammatory and metabolic disorders in the future.

Nerve stimulation can be used to treat a range of diseases, including inflammation, diabetes, and gastrointestinal disorders. However, current approaches require the use of implanted electrodes and are limited to stimulating large nerves or those close to the surface of the skin.

Daniel Zachs and colleagues show that daily application of noninvasive ultrasound to the spleen of mice reduced the severity of inflammatory arthritis. They also show that the treatment resulted in changes in B and T white blood cell populations, and that the efficacy of the treatment was reduced in animals lacking these cells.

In a separate study using rat and mouse models, Chris Puleo, Vicky Cotero and colleagues applied ultrasound noninvasively to the spleen and reduced the inflammatory response to bacterial endotoxins. The reduction in inflammation was found to be similar to levels that result from using implant-based vagus nerve stimulation (VNS). When targeting the liver with ultrasound, they found this modulated pathways involved in regulating blood glucose levels and was as effective as VNS in supressing hyperglycaemia (when blood glucose levels are too high) in response to endotoxin exposure. They also found that the response in the liver only occurred when specific locations in the organ known to contain glucose-sensory neurons were targeted.

These papers suggest that ultrasound stimulation has the potential to replace implantable devices for conditions that are amenable to treatment via neuromodulation. However, further studies are required, and a clinical trial is under way to explore the use of noninvasive ultrasound for patients with rheumatoid arthritis.