Free Radical Oxidation and Metabolic Processes of Cartilage and Bone Tissues in Animals with Surgical Model of Posttraumatic Osteoarthrosis

Abstract

INTRODUCTION: Posttraumatic osteoarthrosis (PTOA) resulting from injuries of connective-tissue components of the joint, is accompanied by formation of free radicals activating chondro- and osteoresorption, which leads to fragmentation of biopolymers of the extracellular matrix of the joint tissues.
 AIM: To study the peculiarities of free radical oxidation and metabolic processes of cartilage and bone tissues in animals with a surgical model of PTOA of the knee joint.
 MATERIALS AND METHODS: The study was conducted on 31 rats (11 intact animals and 20 animals with PTOA model). The metabolic processes of the connective tissue were evaluated by the changes in the content of biomarkers of the cartilage (hyaluronan, aggrecan) and bone (fibroblast growth factor-23, osteprotegerin, sclerostin, osteocalcin) tissues. The condition of the free radical oxidation processes was evaluated by the level of lipid hydroperoxides, and the activity of antioxidant system by the parameters of the total antioxidant and thiol statuses.
 RESULTS: In rats with the PTOA model, an increase in cartilage tissue biopolymers aggrecan and hyaluronan (p 0.001) was noted with a negative change in the marker of bone formation (a tendency to increase in the content of osteocalcin) and markers of regulation of bone homeostasis (increased fibroblast growth factor-23, p 0.001), with a tendency to decrease in the content of osteoprotegerin and sclerostin, in comparison with intact animals of the control group. In parallel with this, an increase in lipid hydroperoxides (p 0.01) in the systemic bloodstream was detected with a decrease in the thiol status index (p 0.01) with preserved normal total antioxidant activity (p 0.05).
 CONCLUSION: The data of the conducted study evidences intensification of free radical oxidation and derangement of metabolic processes in the bone and cartilage tissues in animals with a surgical model of PTOA of the knee joint. A negative change in the metabolism of the bone tissue was manifested by the loss of balance of remodeling processes, and metabolic disorders in the cartilage tissue consisted in the destruction of its biopolymers in conditions of intensification of free radical oxidation processes and relative tension of the thiol system with the total antioxidant activity remaining within the physiological norm. The established facts are promising from the point of view of using the studied biomarkers both for the identification of pathogenetic triggers of PTOA of the knee joint, and for the determination of the direction of therapeutic measures.