Therapeutic Treatment of Superoxide Dismutase 1 (G93A) Amyotrophic Lateral Sclerosis Model Mice with Medical Ozone Decelerates Trigeminal Motor Neuron Degeneration, Attenuates Microglial Proliferation, and Preserves Monocyte Levels

Background

Amyotrophic lateral sclerosis (ALS) is a progressive and currently incurable neurodegenerative disease that destroys the nerve cells controlling voluntary muscle movement. The two ALS drugs currently approved for patients, riluzole and edaravone, offer only modest benefit, so researchers have been searching for additional treatment options that might slow the disease's progression or ease its associated inflammation. Medical ozone - a reactive gas mixture of ozone (O3) and oxygen (O2) - has previously shown immune-modulating and nerve-protective properties in other disease models, prompting a research team to test whether it could help in a well-established mouse model of ALS.

Study design

Researchers based in Germany studied 42 SOD1G93A transgenic mice, a widely used genetic mouse model that develops ALS-like motor neuron degeneration, alongside 43 non-transgenic C57BL/6J mice as controls, with equal numbers of males and females across groups. Once the ALS model mice reached the age at which symptoms typically begin (between 85 and 110 days old), they received daily intraperitoneal (into the abdominal cavity) injections of a medical ozone/oxygen gas mixture for five consecutive days, at a dose of around 1 mg of ozone per kilogram of body weight. The researchers then assessed the mice using a range of methods: motor function tests (tail suspension and paw grip endurance), survival tracking, magnetic resonance imaging (MRI) of the brainstem, immunohistochemical staining of nerve and immune cell markers, and flow cytometry to count and characterise immune cells in the blood, spleen and lymph nodes.

Findings

Ozone treatment did not improve the mice's overall clinical symptoms, motor performance on the behavioural tests, or survival time compared with untreated ALS model mice - the disease still progressed regardless. However, at a cellular level the researchers found several more selective effects. In the trigeminal motor nucleus (a brainstem region controlling jaw and face muscles), ozone-treated mice showed slower motor neuron degeneration and less of the tissue vacuolisation associated with the mutant SOD1 protein, as seen on MRI and tissue staining. Ozone treatment was also associated with reduced proliferation of microglia (the immune cells of the brain and spinal cord that become overactive during ALS-related inflammation) in this region. Separately, in the mesenteric lymph nodes (immune tissue near the intestines), ozone treatment prevented the decline in monocyte numbers that was otherwise seen in untreated ALS model mice.

What the authors concluded

The authors concluded that although a short course of medical ozone did not produce an overall clinical or survival benefit in this ALS mouse model, it did produce selective, measurable neuroprotective and anti-inflammatory effects in specific tissues - slowing motor neuron loss and vacuolisation in the trigeminal nucleus, dampening microglial proliferation, and preserving monocyte populations in lymph nodes. They suggested these findings support further investigation of medical ozone as a potential low-cost adjunct approach in ALS alongside existing treatments, and proposed that future studies test different treatment durations, ozone concentrations and delivery routes to see whether the localised benefits observed here could be extended into broader clinical improvement.

Limitations of this study

This is a preclinical study conducted entirely in a genetically modified mouse model of ALS, not in humans, so its findings cannot be assumed to translate directly to people living with the disease. The five-day ozone treatment course was short and began only once symptoms had already appeared, and the study did not test alternative doses, durations or delivery routes that might produce different results. Importantly, the treatment did not improve overall motor function, clinical progression or survival in these mice - the benefits observed were restricted to specific tissues and cell populations rather than the disease as a whole. The authors themselves note that adjustments to treatment duration, administration route and ozone concentration should be explored in future research before any conclusions can be drawn about clinical relevance. This study should be regarded as early-stage preclinical animal evidence of a biological mechanism, not proof that medical ozone treats or slows ALS in humans.