KOA is a chronic injury of knee joint cartilage caused by factors such as long-term load bearing and mechanical damage [7]. With the increase of age, the degradation of fibrous tissue, osteoporosis and changes of synovial fluid composition become more serious, resulting in the deficiency of joint cartilage nutrition, the reduction of cartilage lubrication, and the increase of pressure on the bone and articular surface for chronic strain and progressive damage [8]. Meanwhile, osteoproliferation causes osteophytes at the edge of the joint, leading to increased bone pressure, which in turn affects blood circulation, aggravates the degree of injury of articular cartilage, and finally causes symptoms such as swelling, pain and even dysfunction. Deformation and loss of articular cartilage, regeneration of subchondral bone and marginal bone are important features of KOA, and articular cartilage is the initial site of the disease. Therefore, in the course of treatment, it is necessary to promote the repair of cartilage tissue while ensuring pain relief and disease progression under control [9]. Glucosamine in human articular cartilage is a basic substance needed in the synthesis of aminoglycans. Oral glucosamine sulfate can directly supplement the cartilage matrix, slow down cartilage degradation, facilitate the synthesis of cartilage protein and the recovery of chondrocyte matrix secretion, and in turn improve the articular cartilage structure [10]. Etoricoxib can selectively inhibit the synthesis of cyclooxygenase and prostaglandin, and play an anti-inflammatory role, so as to effectively alleviate joint swelling and pain [11]. The results of this study showed that compared with before treatment, pain, joint stiffness, joint function scores, and total scores of the WOMAC scale were significantly reduced in the two groups after treatment (P<0.05), indicating that both glucosamine sulfate combined with etoricoxib and etoricoxib alone had significant effects. After treatment, the scores of the experimental group and the total score of WOMAC were lower than those of the control group (P<0.05), suggesting that the efficacy of glucosamine sulfate combined with etoricoxib was better than that of etoricoxib alone. The total effective rate of the experimental group was significantly higher than that of the control group (P<0.05), which was consistent with the above results.
BGP, which is secreted by osteoblasts and mainly deposited in bone matrix, is a kind of non-specific collagen that promotes bone mineralization. It is released in large quantities when bone matrix is degraded, which can reflect the activity of osteoblasts [12]. OPG/RANKL/RANK plays a regulatory role in the process of bone formation and absorption [13]. OPG can inhibit the differentiation and maturation of osteoclasts. The maturation and proliferation of RANK and its ligand osteoclasts promote the maturation and proliferation of osteoclasts. The increase in the RANKL/OPG ratio indicates that the imbalance and abnormality of bone reconstruction can also lead to bone loss and bone density reduction [14]. CTX-II, a small polypeptide mainly distributed in cartilage, can be used to reflect the degradation of collagen type II by protease in cartilage. With rising level of CTX-II, the joint damage was aggravated [15]. As a sensitive marker of articular cartilage injury, COMP, which is mainly expressed in cartilage, has a high tissue specificity, and its level is positively correlated with the degree of joint injury [16]. Herein, compared with before treatment, BGP and OPG were increased significantly after treatment, and those of the experimental group was significantly higher than those of the control group (P<0.05). CTX-II, COMP, and RANKL were significantly reduced, and those of the experimental group was significantly lower than those of the control group (P<0.05). Thus, glucosamine sulfate combined with etoricoxib in the treatment of KOA can better regulate the bone metabolism indexes of patients, delay or hinder joint degeneration, and improve joint function.
TGF-β is a crucial cartilage repair factor, which can maintain the normal structure and function of articular cartilage. The higher the level of TGF-β is, the more favorable the repair of knee osteoarticular injury will be [17]. IGF-1 can accelerate the proliferation of chondrocytes and the formation of chondrocyte colonies by stimulating chondrocytes to synthesize protein polysaccharides and collagen type II. The expression level of IGF-1 is positively correlated with the response of cartilage repair [18]. FGF-2, an effective angiogenic factor in vivo, can promote the generation of new blood vessels by inducing vascular endothelial cells. In addition, as a mitogen and morphogenetic factor of chondrocytes, FGF-2 can promote the repair of cartilage and bone tissue [19]. This study found that compared with before treatment, the levels of TGF-β, IGF-1, and FGF-2 in the two groups were significantly higher than those in the control group after treatment, and those of the experimental group were significantly higher than those of the control group (P<0.05). Accordingly, glucosamine sulfate and etoricoxib can repair the cartilage tissue of KOA patients, and the combination of the two drugs has a better repair effect.
Inflammatory response is the main pathological feature of KOA, inflammatory factors are important factors that damage joint cartilage and cause swelling and pain, and inflammatory factors mainly play a role through a series of cascade amplification reactions [20]. IL-1β can promote the secretion of MMPs, which leads to the degradation of cartilage matrix and chondrocyte apoptosis. IL-17 exerts a strong induction effect on the catabolism of chondrocytes, thus promoting cartilage degradation, and in addition, it can stimulate the production of IL-6 and indirectly promote the secretion of MMPs [21]. IL-18 can induce the production of nitric oxide and prostaglandin E2, and then participate in the process of KOA inflammation and joint injury [22]. TNF-α can activate and aggregate leukocytes, inhibit the synthesis of type II collagen and proteoglycan, inhibit the self repair of cartilage, and promote cartilage degradation. MMPs can degrade extracellular matrix of articular cartilage [23,24]. MMP-3 secreted by synovial cells and chondrocytes can not only degrade matrix protein substrates in a variety of extracellular matrix, but also activate enzymes such as MMP-9 and MMP-13 to produce a cascade amplification reaction. MMP-9 can degrade collagen by destroying the reticular structure formed by cartilage matrix and collagen. The synergistic effect of MMP-3 and MMP-9 can accelerate the destruction process and make the changes of collagen and cartilage irreversible. At present, MMP-13, the most effective type II collagen degrading enzyme, can degrade all kinds of collagen and directly damage the integrity of articular cartilage. This study showed that after treatment, the levels of IL-1β, IL-17, IL-18, TNF-α, MMP-3, MMP-9 and MMP-13 in the two groups were significantly lower than those before treatment (P<0.05). After treatment, the levels in the experimental group were lower than those in the control group (P<0.05). Hence, glucosamine sulfate and etoricoxib can inhibit the secretion of inflammatory factors and then reduce the levels of MMPs, so as to slow down the degradation of cartilage matrix and facilitating the repair of damaged chondrocytes. In the process of arthritis cartilage destruction, IL-1β can up-regulate the expression of Wnt5a which can up-regulate the expression of matrix metalloproteinase through the mediation of JNK signaling pathway [25]. The mRNA levels of JNK and Wnt5a were detected in this study, which were lower after treatment than those before treatment, and those of the experimental group was lower than those of the control group (P<0.05). The results indicated that JNK and Wnt5a were involved in the process of decreasing IL-1β and inhibiting matrix metalloproteinase in the treatment of KOA with glucosamine sulfate and etoricoxib.
As an important pathway leading to chondrocyte apoptosis, NO-induced apoptosis is closely related to NO, LPO and SOD [26]. A large number of free radicals produced by the body during the onset of KOA can promote apoptosis [27]. NO, a key member of free radicals, can aggravate chondrocyte injury by inducing chondrocyte apoptosis. LPO, the metabolite of free radical lipid peroxidation, can damage the structure of cells and cell membranes. This indicator is often used to indirectly reflect the damage degree of free radicals to tissue cells. SOD can remove oxygen free radicals through disproportionation, and block the cytochrome C-dependent mitochondrial apoptosis pathway, thereby playing a protective role in the synovium and chondrocytes. In this study, compared with before treatment, NO and LPO levels were decreased after treatment, and those of the experimental group were lower than those of the control group. Moreover, the SOD level was increased, and that of the experimental group was higher than that of the control group (P<0.05). We postulated that glucosamine sulfate combined with etoricoxib dominated in the repair of KOA cartilage by increasing SOD level, inhibiting lipid peroxidation, reducing free radicals, inhibiting apoptosis of chondrocytes, and ultimately protecting and repairing cartilage.