Impact of leptin or melatonin on Sema4D overexpression-related bone metabolism.

PURPOSE: The current study aims to investigate the regulatory impact of leptin or melatonin on bone metabolism as well as the underlying mechanism in conjunction with Sema4D (monoclonal antibody to semaphorin 4D). METHODS: Rats were used to create the osteoporosis model utilizing the OVX (OVariectomize) technique. Rat tibial specimens from each side were collected for three-dimensional reconstruction and Micro-CT scanning examination. The Hematoxylin-osinstaining (HE) staining technique was used to determine the pathological condition of bone tissues. The ELISA (Enzyme-Linked Immunosorbent Assay) assay was used to measure the amount of estradiol present in the serum. In the current study, there were six groups: control, OVX, OVX + NL (no load group), OVX + Sema4D, OVX + Sema4D + leptin, and OVX + Sema4D + MT (melatonin). Rats were given injections of the Sema4D or leptin overexpressing vectors via the tail vein in accordance with the aforementioned classification. By using a high-resolution micro-CT technology, 3D bone structure was discovered. The activity of tartrate-resistant acid phosphatase-5b (TRAP-5b) and bone-derived alkaline phosphatase (BALP) in serum was assessed using an ELISA. The number of osteoclasts in the metaphysis of the upper tibia was determined using TRAP (tartrate-resistant acid phosphatase) staining. Immunohistochemistry was used to find leptin and bone morphogenetic protein-2 (BMP-2) expressions in bone tissue. RESULTS: The BV/TV (Bone volume/Tissue volume), Tb.N (Trabecular number), BMD (Bone Mineral Density), and BMC (Bone Mineral Content) levels were significantly higher in the OVX + Sema4D + leptin and OVX + Sema4D + MT groups compared to OVX + NL, while Tb.Sp (Trabecular separation) levels were significantly lower. In contrast to the OVX group, the bone trabeculae in the OVX + Sema4D + leptin and OVX + Sema4D + MT groups had a relatively complete structure and tended to be organized closely. The amount of bone trabeculae grew drastically, whereas the proportion of TRAP-positive osteoclasts declined dramatically. BMP-2 and leptin were also elevated, while BALP and TRAP-5b activity was reduced. CONCLUSION: Leptin or melatonin improved Sema4d's role in trabecular bone microstructure, bone production, and repairment of trabecular bone loss in osteoporosis rats.

Specificity protein 1-mediated ACSL4 transcription promoted the osteoarthritis progression through suppressing the ferroptosis of chondrocytes.

BACKGROUND: Chondrocytes are the main cell damage type involved in the occurrence and development of osteoarthritis (OA). Ferroptosis has been confirmed to be related to many degenerative diseases. This research aimed to explore the role of Sp1 and ACSL4 in ferroptosis in the IL-1ß-treated human chondrocyte cells line (HCCs). METHODS: The cell viability was detected with CCK8 assay. The ROS, MDA, GSH, and Fe2+ levels were assessed with corresponding detecting kits. The Col2a1, Acan, Mmp13, Gpx4 and Tfr1 levels were determined by RT-qPCR assay. Western blot was conducted to evaluate the Acsl4 and Sp1 levels. PI staining was carried out to analyze the cell death. The double luciferase report was conducted to verify the interaction between Acsl4 and Sp1. RESULTS: The results showed that IL-1ß stimulation elevated the LDH release, cell viability, ROS, MDA and Fe2+ levels and declined the GSH levels in the HCCs. Additionally, the mRNA levels of Col2a1, Acan, and Gpx4 were prominently decreased, while Mmp13 and Tfr1 were prominently elevated in the IL-1ß stimulated HCCs. Furthermore, Acsl4 protein levels were upregulated in the IL-1ß-stimulated HCCs. Both Acsl4 knockdown and ferrostatin-1 treatment neutralized the role of IL-1ß in the HCCs. What's more, Acsl4 was transcriptionally regulated by Specificity protein 1 (Sp1). Sp1 overexpression enhanced the Acsl4 levels and Sp1 knockdown declined it. CONCLUSION: Upregulation of Sp1 activates Ascl4 transcription and thus mediates the occurrence of ferroptosis. Hence, Acsl4 may be a therapeutic target for intervention of OA.

LINC00313 promotes the proliferation and inhibits the apoptosis of chondrocytes via regulating miR-525-5p/GDF5 axis.

BACKGROUND: The present study aimed to explore the potentials of lncRNA LINC00313 in osteoarthritis (OA). METHODS: qRT-PCR was performed to detect the expression of LINC00313 in OA tissues and cells. CCK-8 and EDU were used to detect cell proliferation. The ELISA test kit was conducted to detect the expression of inflammatory factors. Flow cytometry was used to detect the apoptosis rates. Western blot was applied to measure the protein expression. The luciferase reporter gene test was carried out to verify the relationship between miR-525-5p and LINC00313 or GDF5. RESULTS: The data showed that the expression of LINC00313 was significantly down-regulated in OA tissues and cells. Functionally, LINC00313 promoted the proliferation of chondrocytes and suppressed the secretion of inflammatory factors and cell apoptosis. Moreover, LINC00313 functioned as a ceRNA to up-regulate the expression of GDF5 via sponging miR-525-5p. Luciferase and RNA pull-down assays further verified the interaction between miR-525-5p and LINC00313 (or GDF5). Moreover, overexpression of miR-525-5p or down-regulated GDF5 degraded the cellular functions of chondrocyte. Rescue experiments showed that the overexpression of miR-525-5p reversed the increase in cell viability and the decrease in pro-inflammatory factors and apoptosis rate mediated by LINC00313. The knockdown of GDF5 reversed the promotion of miR-525-5p knockdown on cell viability and the inhibition of pro-inflammatory factors and apoptosis rate. CONCLUSIONS: LINC00313 inhibited the development of OA through regulating miR-525-5p/GDF5 axis. LncRNA LINC00313 can be used as a potential target for the treatment of OA.