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The reduced lncRNA NKILA inhibited proliferation and promoted apoptosis of chondrocytes via miR-145/SP1/NF-κB signaling in human osteoarthritis.

OBJECTIVE
Growing evidence has shown that long non-coding RNAs (lncRNAs) play some roles in the progression of osteoarthritis. In this study, we investigated the functions and mechanisms of lncRNA NKILA (NKILA) of chondrocytes in human osteoarthritis (OA).


PATIENTS AND METHODS
RT-PCR was used to detect the expressions of NKILA and miR-145 in OA tissues. After transfection of NKILA overexpression lentivirus (LV-NKILA) and NKILA downregulation lentivirus (LV-shNKILA) into primary chondrocytes, MTT assay was carried out to measure the cell proliferation of chondrocytes. The expressions of SP1, Bcl-2, Bax, cleaved caspase-3 and NF-κB signaling factors were detected by Western blot. Moreover, luciferase assay was performed to explore the binding site of NKILA and miR-145, miR-145 and SP1. Finally, JSH, a NF-κB signaling inhibitor, was added into chondrocytes transfected with LV-shNKILA or miR-145 mimic to detect that NKILA functions via miR-145/SP1/NF-κB signaling pathway.


RESULTS
We found that NKILA and SP1 were significantly reduced, miR-145 was increased in cartilage tissues of OA patients. After LV-NKILA transfection, the proliferation ability of chondrocytes was improved and cell apoptosis was inhibited; however, the proliferation ability of chondrocytes was repressed, and cell apoptosis was increased in LV-sh NKILA group. MiR-145 was predicted to be a potential target of NKILA and luciferase gene reporter assay confirmed that NKILA could directly bind with miR-145. Furthermore, SP1 was predicted to be a target gene of miR-145 and luciferase gene reporter assay proved that miR-145 could directly bind with SP1. Finally, we added JSH, a NF-κB signaling inhibitor, into chondrocytes with LV-shNKILA or miR-145 mimic. Results showed that the repressed SP1 was reversed after the addition of JSH in both LV-shNKILA and miR-145 mimic group. Further, the repressed proliferation capacities and promoted cell apoptosis were also reversed after the addition of JSH.


CONCLUSIONS
According to the results, this study uncovers NKILA is reduced in human osteoarthritic cartilage tissues. Furthermore, we firstly uncover that the reduced NKILA could function as a ceRNA to improve miR-145, which inhibited SP1 expression and regulated NF-κB signaling pathway, thereby promoting tissue inflammation, and inhibiting proliferation and promoting apoptosis of chondrocytes. Thus, it may be used as a promising prognostic marker and a potential target for osteoarthritis.