Abstract
Osteoporosis is the most common and complex skeletal disorder worldwide. Exosomes secreted by bone marrow-derived mesenchymal stromal cells (BMSCs) are considered as an ideal seed source for bone tissue regeneration. However, the role of exosomes secreted by BMSCs (BMSCs-Exos) in osteoporosis and its underlying mechanisms remain unclear. In the present study, the expression of microRNA (miRNA)-146a and circular RNA (circRNA) Rtn4 (circ-Rtn4) was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR), and their protein expression was determined by Western blotting. Enzyme-linked immunosorbent assay was performed to detect caspase-3 activity. Cell viability and apoptosis were assessed using 3-(4,5-Dimethylthiazol-2yl-)-2,5-diphenyl tetrazolium bromide (MTT) assay and flow cytometry analysis, respectively. Luciferase reporter assay was exploited for target validation. Results showed that tumor necrosis factor-α (TNF-α) dose-dependently increased miR-146a expression, inhibited cell viability, and promoted cell apoptosis, as indicated by increased caspase-3, cleaved caspase-3, and Bcl-2-associated X protein (Bax) expression as well as caspase-3 activity. However, miR-146a silencing or co-culture with BMSCs-Exos blocked these effects. Moreover, co-culture with exosomes-derived from circ-Rtn4-modified BMSCs (Rtn4-Exos) attenuated TNF-α-induced cytotoxicity and apoptosis in MC3T3-E1 cells, as evidenced by the decrease in caspase-3, cleaved caspase-3, and Bax protein expression and caspase-3 activity. In addition, miR-146a was identified as a target of circ-Rtn4, and Rtn4-Exos exerted their function in TNF-α-treated MC3T3-E1 cells by sponging miR-146a. Hence, our findings suggested that Rtn4-Exos attenuated TNF-α-induced cytotoxicity and apoptosis in murine MC3T3-E1 cells by sponging miR-146a, suggesting that Rtn4-Exos may serve as novel candidates for treating osteoporosis.
Highlights
Osteoporosis is the most common and complex skeletal disorder worldwide [1]
Our results showed that exosomes derived from circ-Reticulon 4 (Rtn4)-modified bone marrow-derived mesenchymal stromal cell (BMSC) (Rtn4-Exos) inhibited tumor necrosis factor-α (TNF-α)-induced cytotoxicity and apoptosis in murine MC3T3-E1 cells via regulating miR-146a expression, indicating that Rtn4-Exos may serve as novel agents for the treatment of osteoporosis
TNF-α dose-dependently increased the expression of miR-146a, decreased the viability an,d promoted the apoptosis of MC3T3-E1 cells
Summary
Osteoporosis is the most common and complex skeletal disorder worldwide [1]. Osteoporosis results from altered normal bone remodeling, including increased osteoclast activity and reduced osteoblast generation [2]. Promotion of osteoblast proliferation and inhibition of osteoblast apoptosis appear to be promising strategies for the prevention and clinical treatment of osteoporosis. Research on bone marrow-derived mesenchymal stromal cell (BMSC)-based therapies for bone disorders, including osteoporosis, has been promising [3]. A membrane vesicle (40–150 nm in diameter) secreted by various cell types, acts as an intercellular messenger to regulate cellular function by enabling. Exosomes derived from BMSCs (BMSCs-Exos) have been reported to regulate the proliferation and apoptosis of osteoblasts, thereby indirectly promoting bone repair and improving osteoporosis [6]. The effects of BMSCs-Exos on tumor necrosis factor-α (TNF-α)-induced cytotoxicity and apoptosis, and the underlying mechanisms remain unknown
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