Intradiscal <i>Cutibacterium acnes</i> Sustains Modic Type 1‐Like Lesions Over Time in a Rat Lumbar Endplate Injury Model

Background: )-mediated) and non-bacterial etiologies are both suggested to induce MC1, but it remains unclear whether MC conversion is etiology-specific. This has important implications for patient management and the development of MC therapies. Aims: To assess MC-subtype lesion prevalence and pain-like behavior over time in an etiology-specific MC rat model. Methods: = 18) to mimic aspects of bacterial versus non-bacterial MC etiologies. MC-subtype prevalence was evaluated by magnetic resonance imaging at 1, 8, and 14 weeks post-injury. Disc degeneration, bone marrow lesion neutrophil elastase and CD19 immunoreactivity, spinal cord sensitization, and pain-like behavior (von Frey) were assessed, and contributors to pain-like behavior were identified (random forest). Results: injection resulted in bone marrow lesions with higher neutrophil elastase- and CD19 immunoreactivity. MC1-like lesions contributed strongest to pain-like behavior, although von Frey did not differ between groups. Conclusion: injection sustained MC1-like lesions in an etiology-specific lumbar MC rat model, suggesting that patients with bacterial MC etiology may be more likely to persist in painful MC1.