Ohio State Scientists Map Gut Microbes After Spinal Cord Injury in Mice

Phillip Popovich, a professor and chair of neuroscience in Ohio State's College of Medicine, said the spinal cord should not be viewed in isolation. "We tend to think of spinal cord injury as a problem that begins and ends in the spinal cord, but our work suggests that we need to think much more broadly," Popovich said. He noted the cord connects the brain to the gut, where microbes interact with the body's largest collection of immune cells.

In a study of mice, researchers restored a bacterial strain that disappeared after spinal cord injury and reported lower inflammation and steadier body weight. A companion study published in Communications Biology identified 19 microbial species in the mouse gut tied to nitrogen loss following injury, a process associated with muscle wasting in people. The work appears in NPJ Biofilms and Microbiomes and Communications Biology.

Kristina Kigerl, a research scientist in Popovich's lab, co-led the work with Ahmed Zayed, a research scientist in microbiology, and Mohamed Mohssen, a recent Ohio State biophysics PhD graduate. Their teams built a catalog of microbial species present in mouse guts at points before and after injury. The analysis of 333 fecal samples produced 6,635 draft genomes, covering about 80% of the gut microbiome in one mouse strain commonly used in nervous system research.

Researchers compared microbiomes in three groups of male and female mice over six months: animals with a lesion in the low thoracic spinal cord, animals with a lesion in the high thoracic cord, and mice with an undamaged cord. Changes in gut bacteria varied by injury level, sex, and time since injury. One species, Lactobacillus johnsonii, dropped in every injured animal. Feeding that species back to injured mice eased some symptoms, though the researchers said a combination therapy may be needed to sustain it.

The nitrogen imbalance appeared only in injured male mice. Depleted bacteria that convert a compound into usable nitrogen disrupted chemical signaling tied to muscle function, and the analysis narrowed the populations linked to most of those nitrogen changes to 19 species. Kigerl said the smaller list "makes things a lot more clear about how we should progress." The work was supported by the National Institute of Neurological Disorders and Stroke, the Belford Center for Spinal Cord Injury, and the Ray W. Poppleton Research designated endowment.