Beyond Local Pathology: Exploring the Role of Gut Microbiota in Chronic Low Back Pain Using an Integrated Behavioral and Microbiological Approach

Authors

• Adan L. Redwine, University of Nebraska-LincolnFollow

First Advisor

Hyun-Seob Song

Committee Members

Rebecca Wachs, Amanda Ramer-Tait

Date of this Version

5-2026

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Agricultural and Biological Systems Engineering

Under the supervision of Professor Hyun-Seob Song

Lincoln, Nebraska, May 2026

Comments

Copyright 2026, Adan L. Redwine. Used by permission

Abstract

Chronic low back pain (LBP) affects millions worldwide, often originating from intervertebral disc (IVD) degeneration. While the gut microbiome modulates musculoskeletal pain, prior studies of the gut-disc axis have focused entirely on structural changes. This leaves a critical gap: does the microbiome influence the experience of discogenic pain? To answer this, an integrated approach using longitudinal gut microbiome profiling, machine learning-based behavioral phenotyping, and structural disc assessments in a rat model of discogenic LBP was utilized.

Female Sprague Dawley rats underwent one of four conditions: sham surgery, IVD injury, antibiotic-mediated microbiome depletion + IVD injury, or IVD injury + treatment with an injectable extracellular matrix hydrogel (dNP+). The microbiome was analyzed via 16S rRNA sequencing. To objectively assess pain, grip strength testing with deep-learning pose estimation and unsupervised behavioral classification were used. The IVD was evaluated using micro-CT, histology, and neuronal markers (PGP9.5 and CGRP).

The results revealed a complex relationship. While disc injury did not cause community-wide changes, it drove selective taxonomic shifts tightly coupling specific bacterial taxa to pain severity in the degenerate state. Furthermore, microbiome depletion worsened disc degeneration and drastically increased innervation, increasing nociceptive nerve fibers in the normally aneural inner disc. This did not result in an increased pain phenotype presentation, suggesting microbiome depletion uncouples structural innervation and degeneration from the pain experience. Conversely, treating the injury with dNP+ restored both disc volume and grip strength. The bacterial taxa most closely tied to grip strength during injury distinguished the injured group from the injured + treated group.

These findings demonstrate a bidirectional gut-disc-pain axis: disc injury selectively alters the microbiome, the microbiome contributes to the pain phenotype in a degenerative state, and successful treatment drives a convergent restructuring of the gut flora. Because these microbiome shifts are dynamic and injury-specific, this work suggests that targeted microbial therapies offer a more effective approach to treating discogenic LBP than broad-spectrum interventions.

Advisor: Hyun-Seob Song