Abstract: BACKGROUND: Currently, there have been studies on the regulatory mechanism of lncRNA\miRNA\mRNA co-expression network on the occurrence and development of osteoarthritis. Our research group has screened qualified NONHSAT248596.1 and miR-146a-5p through the database in the previous stage, but the corresponding in vivo experiments to verify the above regulatory mechanisms are still lacking. 
OBJECTIVE: To explore the role of NONHSAT248596.1 in regulating competitive endogenous RNA of miR-146a-5p in cartilage degeneration mediated by stromal cell derived factor type 1/chemokine receptor 4 axis in vivo.
METHODS: The models of osteoarthritis were established in 36 New Zealand rabbits by injecting stromal cell derived factor 1 solution into the knee joint of the right hind limb. According to the random number table method, they were divided into four groups. lncRNA group, miRNA group, ceRNA group and control group were injected with lentivirus vector overexpressing NONHSAT248596.1, lentivirus vector overexpressing miR-146a-5p, lentivirus vector overexpressing miR-146a-5p+NONHSAT248596.1 and empty lentivirus vector into the molded knee joint, respectively. At 4, 8 and 12 weeks of modeling, cartilage tissues and subchondral bone tissues of the knee joint were taken for relevant detection.
RESULTS AND CONCLUSION: Hematoxylin-eosin staining and safranin fast green staining showed different degrees of degeneration in the four groups. At 4 weeks, the cartilage tissue of the lncRNA group showed swelling of chondrocytes, loss of cell polarity, destruction of extracellular matrix, surface erosion, fracture formation and partial or full layer loss of cartilage tissue. The degree of cartilage injury was gradually aggravated with time. The progression of articular cartilage inflammation in the miRNA group was the slowest among the four groups. qRT-PCR showed that at the same time point, mRNA expression levels of NONHSAT248596.1, chemokine receptor 4, matrix metalloproteinase 3, matrix metalloproteinase 9 and matrix metalloproteinase 13 in cartilage tissue of the lncRNA group were higher than those of the other three groups (P < 0.05). The mRNA expression levels of miR-146a-5p, aggrecan and type II collagen were lower than those of the other three groups (P < 0.05). The mRNA expression levels of NONHSAT248596.1, chemokine receptor 4, matrix metalloproteinase 3, matrix metalloproteinase 9 and matrix metalloproteinase 13 in the miRNA group were lower than those in the ceRNA group and control group at 8 and 12 weeks after the model construction (P < 0.05). The mRNA expressions of miR-146a-5p, aggrecan and type II collagen were higher than those of the ceRNA group and control group (P < 0.05). Western blot assay showed that at the same time point, the expression levels of aggrecan and type II collagen in cartilage tissue of the lncRNA group were always lower than those of the other three groups (P < 0.05). The expression levels of aggrecan and type II collagen in cartilage tissue of the miRNA group at 8 and 12 weeks after modeling were higher than those of the ceRNA group and control group (P < 0.05). The results showed that miR-146a-5p, as the target of NONHSAT248596.1, could be inhibited by the effect of its ceRNA. After acting on miR-146a-5p, NONHSAT248596.1 regulates the stromal cell derived factor type 1/chemokine receptor 4 axis to affect the expression of matrix metalloprotein, type II collagen, and aggrecan in osteoarthritis chondrocytes, resulting in the degradation of extracellular matrix and the loss of proteoglycan.

Key words: osteoarthritis, lncRNA(NONHSAT248596.1), miR-146a-5p, stromal cell derived factor 1, C-X-C chemokine receptor type 4, cartilage degeneration