Research ArticleExperimental Studies
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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

Abstract

Background/Aim: Pyogenic spondylodiscitis causes rapid endplate destruction followed by bone remodeling; however, the time-course of bone loss and recovery remains incompletely defined. This study aimed to characterize longitudinal changes in vertebral bone and intervertebral disc pathology in a rat tail pyogenic spondylodiscitis model.

Materials and Methods: Male Sprague-Dawley rats (n=16) were allocated to 2-, 4-, or 6-week observation groups. Staphylococcus aureus ATCC 29213 (107 CFU/ml, 100 μl) was injected into the C6/7 disc space (Discitis segment), and phosphate-buffered saline (100 μl) was injected into C9/10 as an internal Control segment. Micro-computed tomography was performed at baseline and at sacrifice to quantify the bone destruction rate, disc height ratio, cancellous Hounsfield units (HU), and trabecular microarchitecture (bone volume fraction, trabecular thickness, trabecular number, and trabecular separation). Histology (TRAP and osteocalcin staining) and bone histomorphometry [osteoclast surface per bone surface (Oc.S/BS), osteoclast number per bone surface (Oc.N/BS), and osteoblast surface per bone surface (Ob.S/BS)] were evaluated.

Results: The bone destruction rate was significantly higher in the Discitis segment than in the Control segment at all time points, indicating persistent endplate damage. The disc height ratio decreased at 2 weeks but did not differ from controls at 4-6 weeks. Cancellous HU and trabecular parameters showed a biphasic pattern: decreased bone mass at 2 weeks, followed by recovery/reconstruction at 4-6 weeks. Histomorphometry demonstrated increased osteoclast activity (Oc.S/BS, Oc.N/BS) and osteoblast surface (Ob.S/BS) in the acute phase, with osteoclast indices decreasing over time, whereas osteoblast surface remained relatively elevated.

Conclusion: This model demonstrated a biphasic bone metabolic response characterized by increased osteoclast-mediated bone resorption followed by bone formation and trabecular remodeling. Moreover, this model may serve as an experimental platform to investigate the optimal timing and strategies of therapeutic interventions.

Keywords:

Introduction

In recent years, the incidence of pyogenic spondylodiscitis has been increasing, likely due to population aging and the growing number of immunocompromised hosts (1-3). Once infection is established, rapid narrowing of the intervertebral disc space and progressive destruction of the vertebral endplates can occur, leading to local kyphotic deformity, refractory pain, and even neurological deficits (4, 5). Consequently, many patients require prolonged hospitalization and extended antibiotic therapy, and chronic pain, functional impairment, and reduced quality of life may persist even after infection control (2, 6, 7). Therefore, the management of pyogenic spondylodiscitis should aim to suppress bone destruction as much as possible and to achieve early bone healing, namely bony union (bony bridging) and bone regeneration (bone formation), to prevent spinal deformity.

To promote earlier bony union, osteoporosis medications and, more recently, spinal fixation surgery have been considered; however, a clear therapeutic protocol has not yet been established. Regarding the efficacy of osteoporosis medications for bone loss associated with pyogenic spondylodiscitis, Ohnishi et al. reviewed previous reports including those on romosozumab, teriparatide, denosumab, and bisphosphonates, and discussed the potential usefulness of anabolic agents. Nevertheless, further investigation is needed to establish clinical effectiveness and to identify optimal indications and timing of administration (8). Because evaluating these pharmacological effects in clinical settings is difficult, validation using animal models of pyogenic spondylodiscitis is important. To elucidate the mechanisms of bone destruction and bone remodeling in pyogenic discitis, an animal model that allows time-course analyses of structural and cellular changes in bone and the intervertebral disc from infection onset to healing is useful (9).

A rat tail spondylodiscitis model created by injecting Staphylococcus aureus into the coccygeal intervertebral disc enables reproducible establishment of infection in a specific disc and allows another disc level within the same animal to be used as an internal control, making it a suitable experimental platform for investigating bone and disc lesions in pyogenic spondylodiscitis (10, 11). However, in this model, the temporal trajectories of inflammatory findings, bone destruction, and bone regeneration after infection onset remain unclear. Bostian et al. used an in vivo imaging system (IVIS) with bioluminescence and showed that radiance peaked on day 3 and returned to baseline by day 21; by 2 weeks, radiance was no longer significantly different from baseline, suggesting attenuation of the infectious/inflammatory signal over time (10). In contrast, the duration of bone destruction, the onset of bone regeneration, and whether–and, if so, when–bony union (bony bridging), the ultimate therapeutic goal, is achieved remain unknown. Furthermore, the time-course dynamics of increased bone resorption driven by infection-induced inflammatory cytokines and the subsequent bone formation have not been fully clarified.

Thus, the purpose of this study was to use this rat model to clarify the time-course changes in bone destruction and bone repair in pyogenic spondylodiscitis and to elucidate the underlying mechanisms.

Materials and Methods

Animals and experimental protocol. Ten-week-old, male, Sprague-Dawley rats (n=16; Charles River Laboratories Japan, Inc., Tokyo, Japan) were housed in a controlled environment (temperature 23±2 °C, humidity 40%±20%) with a 12-h light/dark cycle and had free access to standard chow and water. After a 2-week acclimatization period, all animals underwent micro-computed tomography (μCT) of the tail vertebrae as a baseline and were then randomly allocated to one of three groups according to the observation period: 2-week group (n=5), 4-week group (n=5), and 6-week group (n=6). Rats were sacrificed at the assigned time point, and imaging and histological analyses were performed. The overall experimental protocol is shown in Figure 1A.

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.

All experimental procedures were approved by the Institutional Animal Care and Use Committee of our institution (approval number: a-1-0520) and were conducted in accordance with the institutional Guidelines for Animal Experimentation.

Induction of discitis and control segments. Pyogenic spondylodiscitis was induced using a previously described tail-disc infection model with minor modifications (10).

Staphylococcus aureus ATCC 29213 is a well-characterized methicillin-susceptible reference strain that has been widely used in experimental osteomyelitis models in rats and was therefore selected as the inoculum in this study (12, 13). Briefly, under general anesthesia, a suspension of S. aureus ATCC 29213 (KWIK-STIK, Microbiologics, St. Cloud, MN, USA; 107 Colony Forming Unit (CFU)/ml, 100 μl) was injected percutaneously into the intervertebral disc space of the 6th and 7th coccygeal vertebrae (C6/7), which was defined as the spondylodiscitis (infected) segment (Discitis segment). As an internal control, an equal volume (100 μl) of sterile phosphate-buffered saline (PBS) was injected into the disc space of the 9th and 10th coccygeal vertebrae (C9/10) of the same animal, defined as the control segment (Control segment). Accurate needle placement into the disc space was confirmed fluoroscopically. The injection levels and approach are illustrated in Figure 1B. After recovery from anesthesia, the rats were returned to their cages and monitored daily for general condition.

Body weight and serum CRP measurements. Body weight was measured in all animals at baseline (0 week) and 2, 4, and 6 weeks after induction of infection. At the time of sacrifice (2, 4, or 6 weeks), blood samples were collected from the abdominal aorta under deep anesthesia. Serum was separated by centrifugation and stored at −80 °C until analysis. Serum C-reactive protein (CRP) levels were measured using an automated analyzer (Fuji Dri-Chem 3000, Fujifilm, Tokyo, Japan) with the vc-CRP-P reagent, according to the manufacturer’s protocol.

Micro-computed tomography (μ-CT) examination. μ-CT was performed using a Cosmo Scan GX II system (Rigaku Corporation, Tokyo, Japan) according to the manufacturer’s instructions, with an isotropic voxel size (edge length) of 25 μm (i.e., 25×25×25 μm3), tube voltage of 90 kVp, and tube current of 88 μA. All rats underwent baseline μCT of the tail vertebrae before bacterial/PBS injection, followed by a second μCT at the time of sacrifice (2, 4, or 6 weeks). During each scan, the tail was fixed in a custom-made holder to maintain a reproducible position. Image reconstruction and analysis were performed using TRI/3D BON software (Ratoc System Engineering Co., Ltd., Tokyo, Japan).

For planar measurements, mid-sagittal images of the C6/7 (Discitis segment) and C9/10 (Control segment) motion segments were used, and the measurement protocol was developed with reference to a previously reported method for vertebral and disc height assessment (14). For each vertebral body, vertebral body height was measured at three predefined points (anterior, middle, and posterior) along the cranio-caudal axis, and the mean of these three values was used for analysis. The bone destruction rate (%) was calculated as the proportional reduction in vertebral body height at sacrifice relative to the corresponding baseline value for each segment (Figure 1C (1)). Intervertebral disc height was similarly measured at three points between the adjacent endplates, and the mean value was used to calculate the disc height ratio (%), defined as disc height at sacrifice divided by baseline disc height (Figure 1C (2)).

For cancellous bone density, Hounsfield unit (HU) values were measured within a circular region of interest (ROI) placed in the central cancellous compartment of the vertebral body on an axial slice showing the largest vertebral body diameter, avoiding the cortical shell and endplates. HU values were recorded for both Discitis and Control segments at each time point. The ROI definition for HU is shown in Figure 1C (3).

For trabecular microarchitecture, three-dimensional volumes of interest (VOIs) were placed in the cancellous region of the vertebral body at the Discitis segment and the corresponding Control segment, excluding the cortical shell and endplates. After segmentation with a fixed global threshold, standard trabecular parameters were calculated in accordance with established μCT morphometric guidelines: bone volume fraction (BV/TV, %), trabecular thickness (Tb.Th, μm), trabecular number (Tb.N, 1/mm), and trabecular separation (Tb.Sp, mm).

Histological preparation and bone histomorphometry. After the terminal μCT, the C6/7 and C9/10 motion segments were harvested en bloc, fixed in 10% neutral-buffered formalin, and decalcified in 10% ethylenediaminetetraacetic acid (EDTA, pH 7.4) at room temperature. Following decalcification, specimens were embedded in paraffin and sectioned sagittally at a thickness of 3 μm. Sections were stained with hematoxylin and eosin for general morphology, tartrate-resistant acid phosphatase (TRAP) (substrate: naphthol AS-BI phosphate, Sigma-Aldrich, St. Louis, MO, USA; cat. no. N2125-1G; CAS 1919-91-1) for osteoclasts, and osteocalcin immunohistochemistry for osteoblasts (primary antibody: anti-osteocalcin, Proteintech Group, Inc., Rosemont, IL, USA; cat. no. 23418-1-AP; supplied by Cosmo Bio Co., Ltd., Tokyo, Japan).

Bone histomorphometric analysis was performed on the cancellous compartment of the vertebral body adjacent to the endplate using a semiautomated image-analysis system. ROIs were defined to include secondary trabecular bone while excluding cortical bone and the growth plate. The following parameters were quantified according to standard nomenclature: osteoclast surface per bone surface (Oc.S/BS, %), osteoclast number per bone surface (Oc.N/BS, 1/mm), and osteoblast surface per bone surface (Ob.S/BS, %). Measurements were obtained separately for the Discitis and Control segments at each time point.

Statistical analysis. All data are expressed as mean±standard deviation (SD) values. A Kolmogorov-Smirnov test was used to confirm that all variables followed a normal distribution. For each time point, comparisons between the Discitis segment and Control segment were performed using Student’s t-test. Comparisons among the 2-, 4-, and 6-week groups within each segment (Discitis segment and Control segment) were performed using one-way analysis of variance (ANOVA) followed by Tukey’s post hoc test. Body weight and serum CRP levels among the 2-, 4-, and 6-week groups were also analyzed using one-way ANOVA with Tukey’s post hoc test. All statistical analyses were performed with EZR, which is a modified version of R Commander designed to add statistical functions frequently used in biostatistics (15). Values of p<0.05 were considered significant.

Results

Body weight and systemic inflammation. Body weight did not differ significantly among the 2W, 4W, and 6W groups at any time point. In all groups, body weight was significantly higher at 2, 4, and 6 weeks than at baseline (p<0.01 for all; Table I). Serum CRP levels exceeded the upper normal limit (0.3 mg/dl) in some animals at 2W and 4W, whereas all values remained within the normal range at 6W. No significant differences in CRP levels were observed among groups.

View this table:
Table I.

Body weight and serum CRP levels at each time point.

μ-CT findings. Reactive bone formation extending laterally from the vertebral cortex was observed at the Discitis segment in all animals, confirming successful induction of infection (Figure 2A). The bone destruction rate was consistently higher in the Discitis segment than in the Control segment at all time points (p<0.05), indicating sustained endplate destruction due to infection (Figure 2B (1)).

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.

The disc height ratio was significantly lower in the Discitis segment of the 2W group (p<0.05), but no differences were detected in the 4W or 6W groups (Figure 2B (2)). Similarly, cancellous bone HU was significantly lower in the Discitis segment of the 2W group (p<0.05) but increased in the 4W and 6W groups to levels comparable to those in the Control segment (Figure 2B (3)).

Trabecular microarchitectural analysis showed a biphasic response in the Discitis segment, characterized by acute bone loss followed by reconstruction (Figure 3A). BV/TV was significantly lower in the 2W group (p<0.05) but became significantly higher than that in the Control segment in the 4W and 6W groups (p<0.01) (Figure 3B (1)). Tb.Th increased progressively over time in the Discitis segment and was significantly higher than that in the Control segment of the 6W group (p<0.05) (Figure 3B (2)). Tb.N was decreased in the 2W group (p<0.05), increased in the 4W group (p<0.01), and was comparable between segments in the 6W group (Figure 3B (3)). Tb.Sp was significantly increased in the 2W group (p<0.05) but was significantly decreased in the 4W and 6W groups compared with the Control segment (p<0.01) (Figure 3B (4)).

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.

Histological and histomorphometric analysis. At two weeks, the Discitis segment showed marked increases in TRAP-positive osteoclasts (Figure 4A, upper left) and osteocalcin-positive osteoblasts (Figure 4B, upper left), which decreased over time at four weeks and six weeks (Figure 4A and B, upper middle, and upper right, respectively). No apparent temporal changes were observed in the Control segment (Figure 4A and 4B, lower panels).

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.

Quantitative histomorphometry demonstrated significantly higher Oc.S/BS and Oc.N/BS in the Discitis segment at two weeks and 4 weeks compared with the Control segment (p<0.05-0.01; Figure 4C (1), (2)). Ob.S/BS was consistently higher in the Discitis segment at all time points, peaking at two weeks (Figure 4C (3)). Within the Discitis segment, osteoclast parameters decreased significantly from two weeks to four weeks and six weeks, whereas Ob.S/BS remained relatively elevated despite a gradual decrease. In the Control segment, Oc.S/BS and Oc.N/BS showed no clear temporal changes, whereas Ob.S/BS was significantly lower at six weeks than at two weeks (p<0.05).

Collectively, these findings indicate that acute discitis induces intense osteoclast-mediated bone resorption in the early phase, followed by a transition toward sustained osteoblast-dominant bone formation during the recovery phase.

Discussion

In this study, the temporal changes in bone and intervertebral disc lesions at 2, 4, and 6 weeks after infection were investigated using a rat caudal vertebra pyogenic discitis model. Longitudinal evaluation by μCT and bone histomorphometry demonstrated that the bone destruction rate in the Discitis segment was consistently higher than that in the Control segment at all time points. In contrast, disc height and cancellous bone HU values were significantly decreased at two weeks, but recovered to levels comparable to those of the Control segment by 4-6 weeks. Bone volume showed a transient decrease at two weeks, followed by a shift toward reconstruction at 4-6 weeks. Histologically, both osteoclasts and osteoblasts increased markedly at two weeks. Quantitative analysis further showed that bone resorption parameters were elevated at two weeks (and partially at four weeks), but gradually decreased thereafter, whereas bone formation parameters remained higher in the Discitis segment than in the Control segment at all time points, peaking in the acute phase and subsequently decreasing while maintaining relatively elevated levels. Collectively, these findings indicate a biphasic bone metabolic response in this model, characterized by enhanced bone resorption in the acute phase of infection, followed by a transition toward bone formation and reconstruction.

Previous studies using bioluminescence IVIS in rat pyogenic discitis models established with the same protocol have demonstrated that bacterial signals at the infected site peak in the early phase after infection (day 3-7) and subsequently decrease to baseline within 2-3 weeks (10). In contrast, positron emission tomography (PET) imaging using the bacterial metabolism-targeting tracer 11C-Para-aminobenzoic acid ([11C]PABA) has shown increasing signals from day two to day 10 in the same model (16). Although these discrepancies likely reflect differences in the biological targets being assessed (bacterial burden versus metabolic activity), both findings suggest that inflammatory activity associated with infection reaches a peak shortly after infection and subsequently subsides.

During the acute phase of infection, proinflammatory cytokines such as tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 are known to upregulate receptor activator of nuclear factor κB ligand (RANKL) expression and promote osteoclast differentiation through activation of the NF-κB/mitogen-activated protein kinase pathways and downstream transcription factors, nuclear factor of activated T-cells c1 and c-Fos, resulting in enhanced bone resorption (17-19). Accordingly, in the present model, increased production of inflammatory cytokines during the acute phase (approximately 1-2 weeks) likely leads to RANKL-mediated osteoclast activation and predominant bone resorption, followed by a shift toward bone formation and remodeling as bacterial burden and inflammation decrease. This sequence is consistent with the biphasic bone metabolic changes observed in this study.

From a clinical perspective, the treatment of pyogenic spondylodiscitis requires not only infection control, but also restoration of spinal stability, ideally achieved through bone stabilization, such as intervertebral bony bridging or fusion (20-22). However, previous studies using rat caudal discitis models have reported obscuration of the disc space and osteophyte formation at infected levels, representing progressive yet incomplete bony bridging (10). Consistent with these findings, complete bony bridging was not observed within the 6-week observation period in the present study. Gamada et al. demonstrated that surgical stabilization of infected segments reduced RANKL expression and osteoclast activity (cathepsin K), thereby suppressing bone destruction and potentially contributing to infection control (11). Based on these observations, the absence of complete bony bridging in the present model may be attributable to local mechanical factors, particularly persistent micro-instability at the infected segment, which could prolong bone resorption and hinder the formation of solid bony bridges. In clinical practice, bone-modifying agents have also been considered to modulate the balance between bone resorption and formation during infection (8, 23). Whether the combination of surgical stabilization and pharmacological intervention can further promote bony stabilization and bridging remains an important subject for future investigation.

Overall, this model demonstrated a clear biphasic temporal pattern, with enhanced bone resorption in the acute phase of infection, followed by a transition toward bone formation and remodeling. Nevertheless, complete bony bridging was not achieved within the 6-week observation period. Future studies should therefore aim to (i) extend the observation period to clarify the timing of bony bridge formation, (ii) incorporate stabilization procedures to evaluate their effects on suppressing bone destruction and promoting bony bridging, and (iii) investigate whether appropriately timed administration of bone anabolic agents, such as teriparatide (TPTD), during the transition from resorption-dominant to formation-dominant phases can accelerate the acquisition of bony bridging. In addition, direct measurement of bacterial burden, inflammatory cytokines, and molecular regulators of bone metabolism, including the RANKL/osteoprotegerin system, would provide mechanistic validation of the bone metabolic dynamics observed in this study.

Study limitations. First, infection was induced by direct injection into the intervertebral disc, and the potential effects of injection-related leakage into surrounding soft tissues or local injury caused by needle puncture cannot be completely excluded. Moreover, this model may differ in part from clinical pyogenic spondylitis, which most commonly arises via hematogenous spread (20). Second, the impact of needle puncture injury itself on the disc structure was not directly evaluated, and minor changes observed even in the Control segment suggest that procedural effects cannot be entirely ruled out. Third, this study did not directly assess infection activity, such as bacterial colony-forming units, viable bacterial signals, or inflammatory cytokine levels, limiting the ability to directly correlate bone destruction and reconstruction with infection dynamics. Future studies incorporating extended observation periods, quantitative infection markers, and therapeutic interventions, including antibiotics, stabilization procedures, and bone-modifying agents, are warranted to further clarify the clinical relevance of this model.

Conclusion

This experimental model provides a useful platform for characterizing the temporal progression from bone destruction to repair and remodeling in pyogenic spondylodiscitis and for investigating associated bone metabolic dynamics. The biphasic response observed in this study, marked by enhanced bone resorption in the acute phase followed by a shift toward bone formation and remodeling, offers important insights into the optimal timing of therapeutic interventions. Future strategies combining antimicrobial therapy, mechanical stabilization, and bone-modifying agents may help achieve both infection control and bony stabilization, thereby optimizing treatment approaches aimed at promoting intervertebral bony bridging.

Acknowledgements

The Authors would like to thank Ms. Kato and Ms. Midorikawa for their support of our experiments.

Footnotes

  • Authors’ Contributions

    Conceptualization, Yuji Kasukawa, Michio Hongo, Takashi Ebihara, and Naohisa Miyakoshi; Funding acquisition, Naohisa Miyakoshi; Data curation, Yo Morishita; Formal analysis, Koji Nozaka, Hiroyuki Tsuchie and Yuji Kasukawa; Investigation, Yo Morishita, Koji Nozaka, Hiroyuki Tsuchie, Yuji Kasukawa, Yuichi Ono, Manabu Akagawa, Kenta Tominaga, Yasuhito Asaka, Akari Hisada and Genki Tojo; Methodology, Yuji Kasukawa, Takashi Ebihara, and Naohisa Miyakoshi; Project administration, Naohisa Miyakoshi; Supervision, Naohisa Miyakoshi; Validation, Yo Morishita; Visualization, Yo Morishita; Writing – original draft, Yo Morishita; Writing – review and editing, Yuji Kasukawa and Naohisa Miyakoshi.

  • Conflicts of Interest

    The Authors declare no conflicts of interest in relation to this study.

  • Artificial Intelligence (AI) Disclosure

    No artificial intelligence (AI) tools, including large language models or machine learning software, were used in the preparation, analysis, or presentation of this manuscript.

  • Received February 6, 2026.
  • Revision received February 28, 2026.
  • Accepted March 4, 2026.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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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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