Acute loading has minor influence on human articular cartilage gene expression and glycosaminoglycan composition in late-stage knee osteoarthritis: a randomised controlled trial.

OBJECTIVE: Osteoarthritis (OA) remains clinically challenging. Regular physical exercise improves symptoms though it is unclear whether exercise influences cartilage at the molecular level. Thus, we aimed to determine the effect of acute loading on gene expression and glycosaminoglycan (GAG) content in human OA cartilage. DESIGN: Patients with primary knee OA participated in this single-blind randomised controlled trial initiated 3.5 h prior to scheduled joint replacement surgery with or without loading by performing one bout of resistance exercise (one-legged leg press). Cartilage from the medial tibia condyle was sampled centrally, under the meniscus, and from peripheral osteophytes. Samples were analysed for gene expression by real-time reverse transcriptase polymerase chain reaction, and hyaluronidase-extracted matrix was analysed for GAG composition by immuno- and dimethyl-methylene blue assays. RESULTS: Of 32 patients randomised, 31 completed the intervention: mean age 69 ± 7.5 years (SD), 58% female, BMI 29.4 ± 4.4 kg/m2. Exercise increased chondroitin sulphate extractability [95% CI: 1.01 to 2.46; P = 0.0486] but cartilage relevant gene expression was unchanged. Regionally, the submeniscal area showed higher MMP-3, MMP-13, IGF-1Ea, and CTGF, together with lower lubricin and COMP expression compared to the central condylar region. Further, osteophyte expression of MMP-1, MMP-13, IGF-1Ea, and TGF-ß3 was higher than articular cartilage and lower for aggrecan, COMP, and FGF-2. Hyaluronidase-extracted matrix from central condylar cartilage contained more GAGs but less chondroitin sulphate compared to submeniscal cartilage. CONCLUSION: Acute exercise had minor influence on cartilage GAG dynamics, indicating that osteoarthritic cartilage is not significantly affected by acute exercise. However, the regional differences suggest a chronic mechanical influence on human cartilage. GOV REGISTRATION NUMBER: NCT03410745.

Implementation of minimally invasive and objective humane endpoints in the study of murine Plasmodium infections.

SUMMARY Defining appropriate and objective endpoints for animal research can be difficult. Previously we evaluated and implemented a body temperature (BT) of <32 °C as an endpoint for experimental cerebral malaria (ECM) and were interested in a similar endpoint for a model of severe malarial anaemia (SMA). Furthermore, we investigate the potential of a minimally invasive, non-contact infrared thermometer for repeated BT measurement. ECM was induced with Plasmodium berghei ANKA infection in C57Bl/6 mice. SMA was induced with Plasmodium chabaudi AS infection in A/J mice. Our previous published endpoint was applied in ECM and 30 °C was pre-determined as the lowest permitted limit for termination in SMA according to consultation with the Danish Animal Inspectorate. Infrared thermometer was compared with the rectal probe after cervical dislocation, ECM and SMA. Linear regression analysis of rectal versus infrared thermometry: cervical dislocation: Pearson R = 0·99, R 2 = 0·98, slope = 1·01, y-intercept = 0·55; ECM: 0·99, 0·98, 1·06, -2·4; and SMA: 0·98, 0·97, 1·14, -5·6. Implementation of the 30 °C endpoint captured all lethal infections. However, some animals with BT below 30 °C were not deemed clinically moribund. This study supports repeated measurement infrared thermometry. A humane endpoint of 30 °C was sensitive in capturing terminal animals but might overestimate lethality in this SMA model.