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Propionibacterium acnes Incubation in the Discs Can Result in Time-Dependent Modic Changes: A Long-Term Rabbit Model
Zhi Shan1, Xuyang Zhang, Shengyun Li
1Department of Orthopaedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, PR China.
Study Design:
A case-control study of animal model of Modic changes (MCs) on rabbits.
Objective:
To evaluate the feasibility of inducing of MCs by injection of Propionibacterium acne (P. acnes) into the lumbar intervertebral discs of rabbits.
Summary Of Background Data:
MCs have been widely observed, and assume to be closely associated with low back pain and P. acnes, but there are few animal models showing the progression of MCs.
Methods:
Ten rabbits were used for the study. The L3-4 and L4-5 discs of all rabbits were injected with 100 μL P. acnes (1.6 × 10 CFU/mL) as P. acnes group, L2-3 disc were injected with 100 μL normal saline as vehicle, and L5-6 disc was untreated (blank). MCs were investigated by magnetic resonance imaging before operation and at 2 weeks, 1, 3, 4.5, 6, and 9 months postoperatively. Following sacrifice, histological analysis, blood test and micro-computed tomography were performed. Cytokine expression in nucleus and endplate tissues was quantified using real-time polymerase chain reaction.
Results:
From 3 months postoperatively, the P. acnes group showed significantly decreased T1-weighted signal intensity, whereas the T2-weighted signal was significantly higher at 3 and 4.5 months, and then decreased remarkably at 6 and 9 months. Eleven of 20 inferior endplates were identified as type I MCs at 4.5 months, and 9 of 20 were identified as type II MCs at 9 months. Real-time polymerase chain reaction showed that expression of interleukin-1β, tumor necrosis factor α, interferon-γ, matrix metalloproteinase-9, and thrombospondin motifs-5 in the nucleus pulposus, and interleukin-1β, tumor necrosis factor α, and thrombospondin motifs-5 in the endplates, were significantly upregulated after injection of P. acnes. Histological slices of discs injected with P. acnes showed disc degeneration, endplate abnormalities, and inflammatory response, with micro-computed tomography confirming bone resorption.
Conclusion:
P. acnes infection of the disc can induce degeneration of the disc and an inflammatory response in the endplate region, presenting as MCs type I and II time dependently.
Level Of Evidence:
N/A.