The Microbiome after Spinal Cord Injury
We all know that spinal cord injury (SCI) affects numerous body systems after injury. Loss of walking function is not the only consequence of SCI. Also affected are bladder function, bowel function, sexual function, immune system function, autonomic nervous system function, spasticity and pain after injury, and now we’re learning that changes in the body’s microbiome may cause issues as well.
Did you also know that SCI is characterized by chronic inflammation? It’s well-known that inflammation occurs within the spinal cord immediately after injury, but more and more evidence is showing that common secondary complications after SCI, for example, urinary tract infections and pressure ulcers, can lead to a state of chronic inflammation. This chronic inflammation can negatively affect health outcomes after injury. Chronic inflammation in people without SCI is an established risk factor for cardiometabolic disorders, such as cardiovascular disease. In the SCI population, the risk of heart disease is significantly higher than in the general population, and it is thought that chronic inflammation is one reason for this prevalence. Miami Project scientist Dr. Mark Nash, Professor of Neurological Surgery and Rehabilitation Medicine, has focused much of his research career evaluating targeted interventions to address cardiometabolic disease after SCI, such as diet and exercise, and recently published an authoritative guideline to inform clinicians who treat persons living with SCI.
If chronic inflammation can negatively affect the health of persons living with SCI, what causes it and what can be done about it? Miami Project scientists have identified numerous processes which contribute to persistent inflammatory stress after SCI. From pain and depression to urinary tract infections and obesity, the potential causes of inflammation are everywhere. A relatively new, and somewhat overlooked, source of inflammation involves the gut microbiome. The word “microbiome” refers to the bacteria that live in and on our bodies. These microbes, albeit small, are mighty and have great potential to impact our health. They communicate with our brain, contribute to metabolic function, modulate our immune system, and interact with most systems of our bodies.
Within the human body, the most diverse population of microbes is found within the gastrointestinal tract or “gut”. Dr. Crystal Noller, a postdoctoral fellow, and Dr. Nash, recently published a review that implicates the gut microbiome as a potential source of inflammation after SCI. In addition, they are conducting a study to learn more about the gut microbiome. By characterizing the composition of the gut microbiome in people with SCI and comparing it to uninjured people, they hope to better understand how changes in the gut microbiome may relate to gastrointestinal dysfunction and how these changes may be contributing to chronic inflammation after injury.
In addition, scientists in the lab of Dr. W. Dalton Dietrich are investigating changes in the gut microbiome in a pre-clinical animal model of SCI. They compared the genetic information of different types of gut bacteria in rats with and without SCI. They found a few different types of bacteria which were significantly more prevalent after SCI (Lactobacullis intestinalis, Clostridium disporicum, and Bifidobacterium choerinum) and one that was significantly depleted (Clostridium saccharogumia). They also found significantly elevated inflammatory markers in tissues of the intestinal tract, which were correlated with diversity in bacteria types. By identifying specific types of bacteria that are different after SCI and understanding how these bacteria may be related to inflammatory markers, this study gives scientists a better idea of where to focus their efforts in the future. This will aid in the design and development of therapeutic interventions aimed at improving gastrointestinal dysfunction and reducing chronic inflammation, with the goal of improving health in people living with SCI.
Noller CM, Groah SL, Nash MS. Inflammatory Stress Effects on Health and Function After Spinal Cord Injury. Top Spinal Cord Inj Rehabil. 2017 Summer;23(3):207-217.
O’Connor G, Jeffrey E, Madorma D, Marcillo A, Abreu MT, Deo SK, Dietrich WD, Daunert S. Investigation of Microbiota Alterations and Intestinal Inflammation Post-Spinal Cord Injury in Rat Model. J Neurotrauma. 2018 Jun 7 (epub ahead of print).