Key Takeaways

  • Current stroke treatment, which includes a combination of clot-busting drugs and surgical clot removal, is only effective for a small number of patients
  • In lab models of stroke, a Mass General research team showed that laser therapy improved blood flow in the brain and decreased stroke injury by stimulating the production of nitric oxide
  • /Since the safety profile of laser treatments for other conditions has already been established, the researchers are optimistic that the approach can be tested in humans soon

People who experience stroke have limited therapeutic options, but new research by investigators from Massachusetts General Hospital, a founding member of the Mass General Brigham healthcare system, reveals the potential for non-invasive light treatment using lasers. The results are published in Stroke.

“Unlike other approaches using chemicals, which can be toxic to our bodies, laser light is a physical parameter. It does not stay in the body after the therapy and will have little chance of causing side effects,” said co–senior author Satoshi Kashiwagi, MD, PhD, an investigator in the Department of Radiology at Massachusetts General Hospital and an assistant professor of Radiology at Harvard Medical School.

Kashiwagi and his colleagues have been searching for new stroke therapies because the currently used combination treatment of intravenous thrombolysis and endovascular thrombectomy (the injection of clot-busting drugs plus surgical removal of a blood clot) is effective only when it is performed within a certain timeframe and is only appropriate for a fraction of patients.

Targeting the endothelial cells that line blood vessels represents a promising therapeutic strategy because dysfunction of these cells is implicated in the development of stroke. Endothelial dysfunction is characterized by insufficient production of nitric oxide (NO), a gas that helps keep blood vessels open to allow blood to flow freely. Noting that previous research has shown that laser therapy increases NO production in endothelial cells, the Mass General research team tested the effects of laser therapy in a mouse model of stroke.

They found that treating the head with low-power invisible laser light improved brain blood flow and decreased stroke injury. Experiments showed that mechanistically, laser treatment improved the function of blood vessels in the brain by stimulating the production of NO.

“We discovered a new way to effectively treat stroke using laser light, a modality that is already widely used in the clinic for procedures such as Lasik eye surgery and tattoo removal, and has a well-known safety profile,” said Kashiwagi. “Thus, we expect that we could advance this technology to clinical trials relatively soon. Such technology has the potential to replace the current standard therapy using chemicals, which may cause side effects.”

Laser therapy may also be effective for a wide array of other cardiovascular diseases that are characterized by NO deficiency.

Authorship: Shinya Yokomizo , PhD; Timo Kopp , MSc; Malte Roessing, MSc; Atsuyo Morita, MD; Seeun Lee , PhD; Suin Cho , MD, PhD; Emiyu Ogawa, PhD; Eri Komai , MD; Kazumasa Inoue , PhD; Masahiro Fukushi, PhD; Susanne Feil , PhD;
Hyung-Hwan Kim , PhD; Denis E. Bragin , PhD; Dmitry Gerashchenko , MD, PhD; Paul L. Huang , MD, PhD; Satoshi Kashiwagi , MD, PhD; and Dmitriy N. Atochin , MD, PhD.

Disclosures: Disclosure forms provided by the authors are available with the full text of this article at

This study was supported by the US National Institutes of Health grants National Institute of Aging (NIA) R01AG081809 (Dr Gerashchenko), National Institute of Allergy and Infectious Diseases (NIAID) R21AI144103 (Dr Kashiwagi), National Institute of Neurological Disorders and Stroke (NINDS) R01NS096237 (Dr Atochin), NINDS R01NS112808 (Dr Bragin), a study abroad scholarship of CMI, Inc, Tokyo, Japan (Dr Yokomizo), the Overseas research fellowship, Japan Society for the Promotion of Science (Dr Yokomizo), the Deutsche Forschungsgemeinschaft (German Research Foundation, [GRK]) – Projektnummer 335549539 – GRK 2381 and the Reinhard Frank-Stiftung (T. Kopp, M. Roessing, and Dr Feil), the Ministry of Health and Welfare, the Republic of Korea HI20C0314 (Dr Lee), and Jeongseon-gun, Republic of Korea (Dr Kim).

Paper cited: Yokomizo S et al.  “Near-Infrared II Photobiomodulation Preconditioning Ameliorates Stroke Injury via Phosphorylation of eNOS.” Stroke DOI: 10.1161/STROKEAHA.123.045358