IntroductionThe microdialysis method was applied to the human knee joint with osteoarthritis (OA) in order to reveal changes in biochemical markers of cartilage and inflammation, intraarticularly and in the synovium, in response to a single bout of mechanical joint loading.MethodsThirty-one female subjects with OA of the knee were randomized to non-exercise (NEx) or exercise (Ex) groups. Following acute resistance exercise (25 sets of 10 repetitions at 60% of 1 Repetition Maximum) or none (NEx), peripheral nerve blocks just below the inguinal ligament were applied and two microdialysis catheters were positioned in two different compartments, intraarticularly and peri-synovially. The microdialysis catheters were perfused at a slow rate (2 μl/minute) with a solution of Ringer-acetate and radioactively labelled glucose allowing for determination of relative recovery (RR) and calculation of interstitial concentrations of inflammatory and cartilage biomarkers over a three-hour period.ResultsA significant increase of Interleukin (IL) -10 was discovered in both positions of the knee in the Ex group over the three hours post exercise, whereas IL-10 remained stationary over time in the NEx group. IL-6 and IL-8 displayed significant increases over time regardless of group and position of the catheter. Cartilage oligomeric matrix protein (COMP) decreased intraarticularly in the post exercise period in the Ex group compared to the NEx group.ConclusionsExercise caused an increase in both intraarticular and peri-synovial concentrations of IL-10 in a group of human females with knee OA. This suggests a positive effect of exercise on a chondroprotective anti-inflammatory cytokine response in patients with knee OA and might contribute to explaining the beneficial effect that exercise has on OA.Trial registrationNCT01090375.

Brown adipose tissue is a promising therapeutic target for opposing obesity, glucose intolerance and insulin resistance. The ability to modulate gene expression in mature brown adipocytes is important to understand brown adipocyte function and delineate novel regulatory mechanisms of non-shivering thermogenesis. The aim of this study was to optimize a lipofection-based small interfering RNA (siRNA) transfection protocol for efficient silencing of gene expression in mature brown adipocytes. We determined that a critical parameter was to deliver the siRNA to mature adipocytes by reverse transfection, i.e. transfection of non-adherent cells. Using this protocol, we effectively knocked down both high- and low-abundance transcripts in a model of mature brown adipocytes (WT-1) as well as in primary mature mouse brown adipocytes. A functional consequence of the knockdown was confirmed by an attenuated increase in uncoupled respiration (thermogenesis) in response to β-adrenergic stimulation of mature WT-1 brown adipocytes transfected with uncoupling protein 1 siRNA. Efficient gene silencing was also obtained in various mouse and human white adipocyte models (3T3-L1, primary mouse white adipocytes, hMADS) with the ability to undergo “browning.” In summary, we report an easy and versatile reverse siRNA transfection protocol to achieve specific silencing of gene expression in various models of mature brown and browning-competent white adipocytes, including primary cells.

The non-pharmacological treatment of osteoarthritis (OA) includes exercise therapy; however, little is known about the specific effect of exercise on the joint per se. The purpose of the present study was to investigate the direct effects of a load-bearing exercise upon cartilage in a single, human osteoarthritic joint determined by biochemical markers of cartilage turnover and inflammation in the synovial fluid (SF), serum and urine. Eleven subjects with OA of the knee(s), but with no other joint- or inflammatory disorders, volunteered for the study and had samples of blood, urine and synovial fluid drawn both at baseline and following 30-min one-legged knee-extension exercise. Workload: 60% of 1 RM (Repetition Maximum). Determination of cartilage oligomeric matrix protein (COMP), aggrecan, C-terminal collagen II peptide (CTX-II) and interleukin (IL)-6 were performed in synovial fluid (SF), serum and urine. A significant decrease was found in SF concentration of COMP following exercise, whereas aggrecan, CTX-II and IL-6 remained unchanged. No differences in any of the tested markers were found in serum and urine between baseline and post-exercise. Thirty minutes of mechanical loading of a single knee joint in human subjects with knee OA resulted in a reduced COMP concentration in SF.