In recent years, significant discoveries have unveiled the profound impact of our gut microbiome – the trillions of bacteria residing in our gastrointestinal tract. Surprisingly, a new study led by Phillip G. Popovich from Ohio State University, published in The Journal of Experimental Medicine, reveals an unexpected advantage of maintaining a healthy gut: enhanced recovery from spinal cord injuries.
The researchers emphasize that our gut microbiota engages in communication with the central nervous system (CNS) through interactions with immune cells and the secretion of metabolites crossing the blood-brain barrier.
They highlight, “Most (~70-80 percent) immune cells in the body are located within gut-associated lymphoid tissues. There, an ongoing dialogue between immune cells and gut bacteria produces cytokines that affect CNS function.”
The impact of gut bacteria extends far beyond, influencing everything from chemotherapy effectiveness to youth obesity risk, making the gut microbiome crucial for overall bodily health.
In addition to the evident effects of traumatic spinal cord injuries, the researchers identify secondary effects, such as the loss of bowel control, which can disrupt the gut microbiome. Termed “dysbiosis,” this disruption occurs when “good” bacteria are depleted or overwhelmed by “bad” bacteria in the gut. Dysbiosis has been linked to autoimmune diseases like multiple sclerosis and type 1 diabetes, playing a role in the progression of neurological disorders.
The researchers, considering their extensive knowledge of the gut microbiome, hypothesized that alterations in the gut microbiome could impact recovery from spinal cord injuries. To test their hypothesis, they conducted experiments on mice.
Mice pretreated with antibiotics to modify their gut microbiomes before spinal cord injury exhibited higher levels of spinal inflammation and poorer recovery. Conversely, injured mice receiving daily probiotic doses showed reduced spinal damage and improved hindlimb movement. The probiotics contained abundant lactic acid-producing bacteria, activating a gut-associated immune cell that inhibits inflammation.
The researchers suggest that these immune cells, known as regulatory T cells, may prevent additional spinal cord damage after injury. Furthermore, the probiotic bacteria, by releasing molecules promoting neuronal growth, could enhance spinal cord recovery.
Popovich explains that one or both of these functions “could explain how post-injury disruption of the gut microbiome contributes to the pathology of spinal cord injuries and how probiotics block or reverse these effects.”
While the mouse study implies that countering gut changes with probiotics could aid spinal cord injury recovery in humans, confirmation of these results in human subjects is still pending.
