Astronauts suffer from 1–2% bone loss per month during space missions. Targeting osteoclast differentiation has been regarded as a promising strategy to prevent osteoporosis in microgravity (μXg). 4-acetylantroquinonol B (4-AAQB), a ubiquinone from Antrodia cinnamomea, has shown anti-inflammatory and anti-hepatoma activities. However, the effect of 4-AAQB on μXg-induced osteoclastogenesis remains unclear. In this study, we aimed to explore the mechanistic impact of 4-AAQB on osteoclast formation under μXg conditions. The monocyte/macrophage-like cell line RAW264.7 was exposed to simulated μXg (Rotary Cell Culture System; Synthecon, Houston, TX, USA) for 24 h and then treated with 4-AAQB or alendronate (ALN) and osteoclast differentiation factor receptor activator of nuclear factor kappa-B ligand (RANKL). Osteoclastogenesis, bone resorption activity, and osteoclast differentiation-related signaling pathways were analyzed using tartrate-resistant acid phosphatase (TRAP) staining, actin ring fluorescent staining, bone resorption, and western blotting assays. Based on the results of TRAP staining, actin ring staining, and bone resorption assays, we found that 4-AAQB significantly inhibited μXg-induced osteoclast differentiation. The critical regulators of osteoclast differentiation, including nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), c-Fos, and dendritic cell-specific transmembrane protein (DC-STAMP), were consistently decreased. Meanwhile, osteoclast apoptosis and cell cycle arrest were also observed along with autophagy suppression. Interestingly, the autophagy inhibitors 3-methyladenine (3-MA) and chloroquine (CQ) showed similar effects to 4-AAQB. In conclusion, we suggest that 4-AAQB may serve as a potential agent against μXg-induced osteoclast formation.

Oligodendrocytes are glial cells located in the central nervous system (CNS) that play essential roles in the transmission of nerve signals and in the neuroprotection of myelinated neurons. The dysfunction or loss of oligodendrocytes leads to demyelinating diseases such as multiple sclerosis (MS). To treat demyelinating diseases, the development of a therapy that promotes remyelination is required. In the present study, we established an in vitro method to convert human fibroblasts into induced oligodendrocyte-like cells (iOLCs) in 3 days. The induced cells displayed morphologies and molecular signatures similar to oligodendrocytes after treatment with valproic acid and exposure to the small molecules Y27632, SU9516, and forskolin (FSK). To pursue the development of a cell-free remyelination therapy in vivo, we used a cuprizone-induced demyelinated mouse model. The small molecules (Y27632, SU9516, and FSK) were directly injected into the demyelinated corpus callosum of the mouse brain. This combination of small molecules rescued the demyelination phenotype within two weeks as observed by light and electron microscopy. These results provide a foundation for exploring the development of a treatment for demyelinating diseases via regenerative medicine.