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Background <p>This study evaluated the correlation between the degree of osteoarthritis (OA), represented by the Mankin scale score, and pain levels measured by the head withdrawal threshold (HWT) in a chemically-induced rat model of temporomandibular joint osteoarthritis (TMJOA). It aimed to validate the Mankin scale as a reliable tool for assessing OA severity in this model.</p> Methods <p>Ninety-nine male Wistar rats underwent TMJOA induction through intra-articular chemical injections of monosodium iodoacetate (<i>n</i> = 85) or collagenase type-2 (<i>n</i> = 14). Over a 30-day period, pain levels were evaluated using the HWT test (at day 0, 2, 7, 14, 21 and 30), alongside fluorodeoxyglucose positron emission tomography (FDG PET) imaging (day 30). Subsequently, the rats were sacrificed for histological assessment of OA severity via the Mankin scale, which is based on the histological analysis of the cartilage structure, tidemark integrity, proteoglycan staining, and cellularity.</p> Results <p>HWT values were significantly lower in the left TMJ compared to the right (<i>p</i> = 0.0001), while Mankin scores were significantly higher in the left TMJ (<i>p</i> = 0.0001). A weak yet significant correlation was identified between the left HWT and the left Mankin score (<i>p</i> = 0.007). Nonparametric regression analysis using kernel smoothing (npreg) showed a modest explanatory power (pseudo-R² = 0.37), supporting a weak but consistent inverse association between HWT and Mankin score in left TMJ.</p> <p>Additionally, standard uptake value (SUV) values from FDG PET scans were significantly higher in the left TMJ than the right (<i>p</i> = 0.006), with a moderate correlation between left SUV and left HWT (<i>p</i> = 0.05).</p> Conclusions <p>This study demonstrated a relationship wherein lower pain thresholds correspond with higher Mankin scores, suggesting that pain levels may serve as an indicator of histological severity in TMJOA. FDG PET imaging also proved effective in assessing inflammatory aspects of OA.</p>

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Pain levels and histological severity in a rat model of chemically-induced temporomandibular joint osteoarthritis

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月1日

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  • Florent Barry,
  • Feng Chai,
  • Romain Nicot

摘要

Background

This study evaluated the correlation between the degree of osteoarthritis (OA), represented by the Mankin scale score, and pain levels measured by the head withdrawal threshold (HWT) in a chemically-induced rat model of temporomandibular joint osteoarthritis (TMJOA). It aimed to validate the Mankin scale as a reliable tool for assessing OA severity in this model.

Methods

Ninety-nine male Wistar rats underwent TMJOA induction through intra-articular chemical injections of monosodium iodoacetate (n = 85) or collagenase type-2 (n = 14). Over a 30-day period, pain levels were evaluated using the HWT test (at day 0, 2, 7, 14, 21 and 30), alongside fluorodeoxyglucose positron emission tomography (FDG PET) imaging (day 30). Subsequently, the rats were sacrificed for histological assessment of OA severity via the Mankin scale, which is based on the histological analysis of the cartilage structure, tidemark integrity, proteoglycan staining, and cellularity.

Results

HWT values were significantly lower in the left TMJ compared to the right (p = 0.0001), while Mankin scores were significantly higher in the left TMJ (p = 0.0001). A weak yet significant correlation was identified between the left HWT and the left Mankin score (p = 0.007). Nonparametric regression analysis using kernel smoothing (npreg) showed a modest explanatory power (pseudo-R² = 0.37), supporting a weak but consistent inverse association between HWT and Mankin score in left TMJ.

Additionally, standard uptake value (SUV) values from FDG PET scans were significantly higher in the left TMJ than the right (p = 0.006), with a moderate correlation between left SUV and left HWT (p = 0.05).

Conclusions

This study demonstrated a relationship wherein lower pain thresholds correspond with higher Mankin scores, suggesting that pain levels may serve as an indicator of histological severity in TMJOA. FDG PET imaging also proved effective in assessing inflammatory aspects of OA.