Table 1.
Overview of control and experimental groups.
Table 2.
Welfare assessment.
Table 3.
Model specific parameters.
Fig 1.
Welfare assessment (WA) scores.
The figure shows pooled mean WA scores collected daily with the score sheet shown in Table 2. Statistics are calculated on ranks (Kruskal-Wallis test, followed by Dunn’s multiple comparisons test), but values are displayed as means ± SEM for ease of viewing. The hash sign (#) represents a statistically significant difference between CFA + BUP and CFA + CAR at #p < 0.05 and ##p < 0.01. For all graphs: base = baseline values, D = day, the line represents the day of analgesic treatment initiation (D0) and the grey area represents the treatment period (15 days). All groups, n = 8, male Sprague Dawley rats.
Fig 2.
Mean body weight per group on day 1–22 and baseline values. Data were analysed by a two-way RM ANOVA followed by Tukey’s multiple comparisons tests. The line represents the day of analgesic treatment initiation (D0) and the grey area represents the days with treatment administrated. Values are expressed as mean ± SEM. For all graphs: base = baseline values, D = day, the line represents the day of analgesic treatment initiation (D0) and the grey area represents the treatment period (15 days). All groups: n = 8, male Sprague Dawley rats.
Fig 3.
(A) Mobility scores. (B) Stance scores. (C) Lameness scores. (D) The joint stiffness score of the ipsilateral TTJ. Statistics are calculated on medians (Kruskal-Wallis test, followed by Dunn’s multiple comparisons test), but values are displayed as mean ± SEM for a better graphical view. The asterisk (*) represents statistically significant difference between CFA + BUP and CFA at *p < 0.05 and **p < 0.01. The hash sign (#) represents a statistically significant difference between CFA + CAR and CFA at #p < 0.05. For all graphs: base = baseline values, D = day, the line represents the day of analgesic treatment initiation (D0) and the grey area represents the treatment period (15 days). All groups, n = 8, male Sprague Dawley rats.
Fig 4.
Circumference measurements of the ipsilateral ankle.
The plus (+) represents a statistically significant difference between CFA + CAR and CFA at +p < 0.05, ++p < 0.01 and ++++p < 0.0001. The hash (#) represents statistically significant difference between CFA + BUP and CFA + CAR at #p < 0.05, ###p < 0.001 and ####p < 0.0001. For all graphs: base = baseline values, D = day, the line represents the day of analgesic treatment initiation (D0) and the grey area represents the treatment period (15 days). For all data: presented as mean ± SEM. All groups, n = 8, male Sprague Dawley rats.
Fig 5.
Assessment of mechanical threshold.
Effects of buprenorphine and carprofen on paw withdrawal thresholds (g) as an expression of mechanical hyperalgesia. (A) Ipsilateral (left, CFA-injected paw) paw withdrawal thresholds. (B) Contralateral (right, non-injected paw) paw withdrawal thresholds. Data are analysed by a two-way RM ANOVA followed by a Tukey’s multiple comparisons test D1, D3, D6, D9, D13, D20 and presented as mean ± SEM. For all graphs: base = baseline values, D = day, the line represents the day of analgesic treatment initiation (D0) and the grey area represents the treatment period (15 days). All groups: n = 8, male Sprague Dawley rats.
Fig 6.
Assessment of the rat grimace scale (RGS).
Facial expressions as a measure of non-evoked pain. Scoring was performed every 24 hours for 21 days with six baseline scorings before induction (D-6 to D0). (A) RGS scores at baseline (D-1) to D21. The line represents the day of analgesic treatment initiation (D0) and the grey area represents the treatment period (15 days). (B) Area under the curve (AUC) for baseline (pre-treatment) RGS scores, presented as a scatter plot. (C) AUC for D1-15 (treatment period), presented as a scatter plot. (D) AUC for D16-21 (post-treatment), presented as a scatter plot. The asterisk (*) represents statistically significant difference from the CFA group at **p < 0.001 and ***p < 0.0001. The hash sign (#) represents statistically significant difference between CFA + BUP and CFA + CAR at #p < 0.05. For all graphs: base = baseline values, D = day, the line represents the day of analgesic treatment initiation (D0) and the grey area represents the treatment period (15 days). For all data: presented as mean ± SEM. For all groups: n = 8, male Sprague Dawley rats.
Fig 7.
Faecal corticosterone measurements.
(A) Faecal corticosterone metabolites (FCM) measurements are displayed as μg/24 h at baseline and D2, D9, D16 and D21. (B) Pre (baseline measurements) -and post-CFA-injection (D2 measurements) are compared. The asterisk represents statistical significant difference at *p < 0.05, **p < 0.01 and ***p < 0.001. For all data: presented as mean ± SEM. For all graphs: base = baseline values, D = day, the line represents the day of analgesic treatment initiation (D0) and the grey area represents the treatment period (15 days). For all groups: n = 8, male Sprague Dawley rats.
Fig 8.
Hematoxylin-eosin (HE) sections.
A. Normal articular spacing between tibia and the tarsal bone with smooth articular surface and a normal synovial lining (magnification 4x). B. Normal chondrocytes in columnar orientation and intact subchondral bone (magnification 4x). C. Normal synovial lining structures (Intima and subintima). Intima made up by 1–3 cells (synoviocytes) and a relatively loose connective tissue layer below with blood vessels and adipose cells (magnification 10x). D. Heavily cell-infiltrated tissue invading cranially and caudally into the tibio-tarsal joint causing local ulcerations in the articular cartilage and subchondral bone tissue (magnification 4x). E. Massive inflamed granulation tissue in the subintimal region together with synovial membrane hyperplasia (magnification 10x). F. Cells in the granulation tissue (macrophages, lymphocytes and plasma cells) surrounding lipid droplets of CFA in varying sizes (magnification 20x). In the pictures: b, bone; c, cartilage; s, synovial tissue; t, tibia; tb, tarsal bone.