CircTMBIM6 promotes osteoarthritis-induced chondrocyte extracellular matrix degradation via miR-27a/MMP13 axis.

OBJECTIVE: Osteoarthritis is a degenerative disease characterized by degeneration of articular cartilage, but the current mechanism is unclear. Circular RNA (circRNA) plays a significant role in a series of biological processes related to osteoarthritis, but its mechanism remains unclear. The purpose of this study was to investigate the role of the circTMBIM6/miR-27a/MMP13 axis in osteoarthritis. PATIENTS AND METHODS: The expression levels of circTMBIM6, miR-27a and MMP13 in cartilage of osteoarthritis patients and normal human cartilage were detected by reverse transcription polymerase chain reaction (RT-PCR). Osteoarthritis cell model was induced by IL-1ß and TNF-α, and the expression changes of circTMBIM6, miR-27a and MMP13 in the in vitro model were detected. In addition, the in vitro regulation of circTMBIM6 and miR-27a in osteoarthritis was verified by transfection of circTMBIM6 and miR-27a plasmids, and the regulation of miR-27a on MMP13 was also verified. The dimethylmethylene blue (DMMB) method was used to analyze the secretion and formation of soluble glycosaminoglycan sulfate (sGAG), and the effects of circTMBIM6 and miR-27a chondrocytes were evaluated. RESULTS: The expression levels of circTMBIM6 and MMP13 in cartilage tissue of patients with osteoarthritis were higher than that of normal group, while the expression level of miR-195 in cartilage tissue of patients with osteoarthritis was lower. After IL-1ß and TNF-α treatment, the expression of circTMBIM6 and MMP13 in chondrocytes increased, while the expression of miR-27a decreased. CircTMBIM6 overexpression reduced miR-27a expression but increased MMP13 expression. The circTMBIM6 gene knockout showed the opposite effect. CONCLUSIONS: CircTMBIM6 promotes osteoarthritis-induced chondrocyte extracellular matrix degradation via miR-27a/MMP13 axis.

Tissue-specific expression of a suicide gene for selective killing of neuroblastoma cells using a promoter region of the NCX gene.

The human NCX gene, a homologue of the murine neural crest homeobox (Ncx/Hox11L.1) gene whose expression is restricted to a subset of neural crest-derived tissues, was expressed in human neuroblastoma cells but not in other tumors or fibroblasts. A 4.5-kb genomic fragment in the 5'-flanking region of the NCX gene efficiently transcribed the fused luciferase reporter gene in human neuroblastoma cells but not in non-neuroblastoma cells. Sequential deletion of this regulatory region from the 5' side demonstrated that a 1.7-kb fragment upstream from the start codon retained the preferential promoter activity in neuroblastoma cells. The transcriptional activation by the NCX promoter was stronger than that by the SV40 T antigen promoter in human neuroblastoma cells. Transfection of neuroblastoma cells with the NCX promoter-linked herpes simplex virus-thymidine kinase (HSV-TK) gene increased their sensitivity to ganciclovir. The regulatory region of the NCX gene is thus useful for neuroblastoma-specific suicide gene therapy.

An enhancer element for expression of the Ncx (Enx, Hox11L1) gene in neural crest-derived cells.

The murine Ncx (Enx, Hox11L1) gene is specifically expressed in a neuronal subset of neural crest-derived tissues. In attempts to elucidate the regulatory DNA element of the tissue-specific expression, we sequenced the 5'-flanking region of the Ncx gene. The transcriptional initiation site was determined at 297 nucleotides (-297) upstream from the ATG start codon (+1). A retinoic acid response element was located on the region between -1163 and -1150. Transient transfection assays with the 5'-flanking sequences fused to the luciferase gene showed that the region between -1387 and -1368 was crucial for the tissue-specific enhancer activity. Furthermore, nuclear proteins extracted from neural crest-derived cells such as murine and human neuroblastoma cells bind to the DNA region between -1387 and -1368. This DNA element was also conserved in the 5'-flanking region of the human NCX gene. Our observations strongly suggest that the DNA element (between -1387 and -1368) contributes to tissue-specific expression of the Ncx gene in murine and human species.