Intradiscal Cutibacterium acnes Sustains Modic Type 1-Like Lesions Over Time in a Rat Lumbar Endplate Injury Model

Area of Science:

• Spinal pathology and pain research.
• Bacterial and non-bacterial etiologies of bone lesions.
• Animal models for human disease study.

Background:

• Modic changes (MC) are vertebral bone marrow lesions associated with pain.
• MC1 is the most painful subtype, MC2 less painful, and MC3 asymptomatic.
• Both bacterial (C. acnes) and non-bacterial factors are implicated in MC1, but etiology-specific progression is unclear.

Purpose of the Study:

• To investigate MC subtype prevalence and pain-like behavior in an etiology-specific rat model.
• To compare the effects of C. acnes versus TNF-α on Modic changes.
• To understand the long-term implications of different MC etiologies.

Main Methods:

• Rats received sham surgery or endplate injury followed by intradiscal injection of C. acnes or TNF-α.
• MC subtypes were assessed via MRI at 1, 8, and 14 weeks.
• Disc degeneration, inflammation markers, spinal cord sensitization, and pain behavior were evaluated.

Main Results:

• C. acnes induced higher MC1 prevalence and spinal cord substance P expression compared to TNF-α.
• TNF-α led to increased MC2 lesions over time, while C. acnes showed higher inflammatory markers.
• MC1 lesions were the primary contributor to pain-like behavior.

Conclusions:

• Intradiscal C. acnes sustained MC1-like lesions in the rat model.
• Bacterial etiologies may lead to more persistent painful Modic changes (MC1).
• Findings have implications for understanding MC progression and developing targeted therapies.