Plasma RANKL level is not a reliable marker to monitor the bone destruction in mice model of osteomyelitis

Abstract

Bone destruction is the hallmark pathological feature of osteomyelitis. [1] Despite advanced antimicrobial treatments, osteomyelitis often leads to severe morbidity, mortality and healthcare expenditure as a consequence of difficult to treat, long-standing infections and frequent relapses. Early initiation of antibiotics has been shown to limit the progression of infection and lower the amount of bone destruction. [1,2] However, debridement of necrotic and/or infected tissue is almost always required in subjects with chronic osteomyelitis.The diagnosis of osteomyelitis is generally based on clinical signs, imaging studies and also blood tests measuring markers of inflammation, including erythrocyte sedimentation rate (ESR), leukocyte count, C-reactive protein (CRP), and procalcitonin levels. [3] However, these blood tests are neither sensitive nor specific for osteomyelitis, since they can be elevated in any kind of infectious or non-infectious activation of inflammation. Moreover, these blood tests reflect Objectives: In this experimental study, we aimed to investigate the specific value of receptor activator of nuclear factor kappa-Β ligand (RANKL) plasma level in osteomyelitis to show the bone destruction and to determine its correlation with classical markers of infection in mice model of osteomyelitis. Materials and methods:Sixty Balb/c female mice (30 to 40 g weight, 3.5 to 4 month-old) were divided into two groups: Controls (n=15) and study group (n=45). All mice underwent tibial decortication and received an injection of sclerosing agent into the intramedullary cavity. The next process was proceeded in two steps to observe the detectability of osteomyelitis-induced bone destruction (step 1) and treatment response (step 2) using the variables examined in our study. In step 1, the study group received 1 mL solution containing Staphylococcus aureus (S. aureus) bacteria (2¥108 per mL) into the intramedullary cavity. Five mice from each group were sacrificed every seven days for three weeks and tibia and blood samples were obtained. In step 2, the remaining 30 infected mice were further divided into two groups to investigate the possible value of RANKL plasma level as a marker of treatment response. Fifteen of these mice received teicoplanin 20 mg/kg for four weeks, while the rest did not receive antibiotics. Eight mice from each group were sacrificed at the end of the second week and the remaining 14 mice were sacrificed at the end of four weeks. Complete blood count, procalcitonin level, C-reactive protein (CRP), and RANKL concentrations were measured from blood samples of each sacrificed mouse.Results: Median RANKL concentration of the control subjects was significantly higher than recipients of intervention at the first and third weeks in step 1 where bone destruction of osteomyelitis was examined. No significant changes occurred in groups receiving and not receiving antimicrobial treatment in terms of RANKL, CRP, and procalcitonin levels throughout four weeks in step 2. The RANKL concentration was signifi...