Decreased muscle strength in adjuvant-induced rheumatoid arthritis animal model: A relationship to behavioural assessments

Abstract

Rheumatoid arthritis (RA) is an autoimmune disorder with unknown aetiology. Patients suffering from RA face persistent pain due to joint inflammation, and tissue destruction. Behavioural phenotyping is an approach to target the role of different behavioural traits associated with disease progression. The study aimed to assess behavioural patterns associated with decreased muscle strength in the adjuvant-induced rheumatoid arthritis animal model. The study was conducted on male Albino Wister rats (n = 30) [Control, Vehicle, and Disease groups]. After taking ethical approvals RA was induced by complete Freund's adjuvant (CFA) intradermally base of tail. The weight of animals, macroscopic analysis of inflammatory signs, and arthritic scores were measured weekly. Grip strength, ganglia-based movement, cataleptic activity, and motor-coordination-related behaviours were assessed among the groups. Radiographs and spleen index assay were performed followed by data analysis using one-way and two-way ANOVA (Analysis of Variance). A significant decrease in weight and an increase in arthritic scores among the diseased group was observed. Behavioural analyses confirmed that diseased animals had significantly decreased grip strength and increased cataleptic activity with less motor coordination. Radiographic images and spleen index assay confirmed the pattern of RA. Therefore, it can be suggested that the development of the disease animal model is an effective approach to identifying the disease progression and associated behavioural changes. Moreover, this prepared laboratory animal model may be utilised for pathway analyses to understand the key role of immune regulators and genetic insight into molecular pathways associated with acute and chronic phases of RA.

Keywords: Behavioural phenotyping; Disease animal model; Grip strength; Rheumatoid arthritis; Splenomegaly.

Graphical abstract

Fig. 1

The experimental timeline of rheumatoid arthritis induced animal model, where CFA is complete Freund's adjuvant and IFA is incomplete Freund's adjuvant.

Fig. 2

Representation of the comparative change in body weight of rats among three targeted groups, where n.s. represented non-significant and *** represented statistically significant probability score (p < 0.001) taken from one-way ANOVA followed by post hoc analysis (Tukey's test).

Fig. 3

(A) Diameter of forelimbs (mm) among the targeted groups (B) Change in hindlimb diameter among the targeted groups throughout the eight weeks. (C) Representation of arthritic index among the experimental groups. (D) The images of swelling in paws with the score 0 to 4. Results are represented in the form of repetitive means (n = 10) analysed by the one-way analysis of variance (ANOVA) followed by Tukey's test, where *** indicates p < 0.001, * indicates p < 0.05 and n.s is non-significant.

Fig. 4

(A) The representation of the Kondziela inverted screen test (KIST) showing the time of fall in seconds for grip strength of limbs (B) The representation of the Pole test showing a time of fall in seconds, where the cutoff time is 60 s (C) Representation of Inclined plane test (IPT) where cataleptic activity was noted (D) The representation of beam walking test (BWT) showing latency time in seconds and (E) number of slips in each group. All the Results are represented in the form of repetitive means (n = 10) analysed by the one-way and two-way analysis of variance (ANOVA) followed by Tukey's test, where *** indicates p < 0.001 and n.s is non-significant.

Fig. 5

Representation of rat limbs from the control group (A) and vehicle group (B) showing no destruction in bone. (C) Representation of rat limbs from the control group, where the yellow circle indicated the presence of oedema, the arrow indicates loss of joint space or narrowing of the joint, the red circle showed the presence of hyperostosis, and the white circle pointed to ulnar deviation or digits deformation. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 6

Representation of weight of spleen (mg) (A) and spleen index assay (B) among the targeted groups including blue = control group, green = vehicle group, and red = disease group. Results were analysed by the analysis of variance (ANOVA) followed by Tukey's test, where *** indicates p < 0.001 and n.s is non-significant. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)