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Time-course Investigation of Bone and Disc Degeneration in a Rat Model of Pyogenic Spondylodiscitis

YO MORISHITA, YUJI KASUKAWA, MICHIO HONGO, KOJI NOZAKA, HIROYUKI TSUCHIE, YUICHI ONO, MANABU AKAGAWA, KENTA TOMINAGA, YASUHITO ASAKA, AKARI HISADA, GENKI TOJO, TAKASHI EBIHARA and NAOHISA MIYAKOSHI
In Vivo May 2026, 40 (3) 1375-1387; DOI: https://doi.org/10.21873/invivo.14290

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Figures

  • Figure 1.
    Figure 1.
    Figure 1.

    Experimental protocol and measurement methods of the rat discitis model. (A) Twelve-week-old male Sprague-Dawley rats (N=16) are allocated into 2-, 4-, and 6-week groups (n=5, 5, and 6, respectively). Rats are sacrificed at the assigned time points. (B) Staphylococcus aureus (S. aureus) (107 CFU/ml, 100 μl) is injected into the C6/7 disc space to create the Discitis segment, and PBS (100 μl) is injected into the C9/10 disc space as the Control segment. (C) (1) Regions of interest (ROIs) (A1-A3, B1-B3 for vertebral bone; C1-C3 for disc) were defined for quantitative evaluation. The bone destruction rate (%) was calculated as the proportional reduction of vertebral bone height from baseline. (2) The disc height ratio (%) was calculated as the ratio of disc height at sacrifice relative to baseline. (3) ROI for Hounsfield Unit measurement. The ROI for Hounsfield Unit measurement was defined as an inscribed circle at the level of the largest vertebral body diameter.

  • Figure 2.
    Figure 2.

    Radiological evaluation of bone destruction, disc height, and Hounsfield Units. (A) Typical images of μCT at the Discitis segment and the Control segment at 2, 4, and 6 weeks. (B) (1) Bone destruction rate (%), (2) disc height ratio, and (3) Hounsfield Unit values. *p<0.05 vs. Control segment; #p<0.05 among time points. Seg: Segment; w: week.

  • Figure 3.
    Figure 3.
    Figure 3.

    Micro-computed tomography (μCT) morphometry and histomorphometric analysis of vertebral changes. (A) Typical 3-dimensional images of μCT of Discitis and Control segments at 2, 4, and 6 weeks. (B) (1) BV/TV (%), (2) Tb.Th (μm), (3) Tb.N (1/mm), and (4) Tb.Sp (mm). *p<0.05 vs. Control segment, #p<0.05 among time points. BV/TV: bone volume fraction; Tb.Th: trabecular thickness; Tb.N: trabecular number; Tb.Sp: trabecular separation; Seg: segment; w: week.

  • Figure 4.
    Figure 4.
    Figure 4.

    Histological images and bone histomorphometry. (A) Typical images of TRAP-stained sections of Discitis and Control segments at 2, 4, and 6 weeks. (B) Typical images of osteocalcin-stained sections of Discitis and Control segments at 2, 4, and 6 weeks. (C) (1) Oc.S/BS, (2) Oc.N/BS, and (3) Ob.S/BS. *p < 0.05 vs. Control segment, #p<0.05 among time points. Scale bar=100 μm. Seg: Segment; w: week; Oc.S/BS: osteoclast surface per bone surface; Oc.N/BS: osteoclast number per bone surface; Ob.S/BS: osteoblast surface per bone surface.

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Time-course Investigation of Bone and Disc Degeneration in a Rat Model of Pyogenic Spondylodiscitis
YO MORISHITA, YUJI KASUKAWA, MICHIO HONGO, KOJI NOZAKA, HIROYUKI TSUCHIE, YUICHI ONO, MANABU AKAGAWA, KENTA TOMINAGA, YASUHITO ASAKA, AKARI HISADA, GENKI TOJO, TAKASHI EBIHARA, NAOHISA MIYAKOSHI
In Vivo May 2026, 40 (3) 1375-1387; DOI: 10.21873/invivo.14290
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