Simulated microgravity environment inhibits matrix mineralization during the osteoblast to osteocyte differentiation

• Published in: Biochemical and biophysical research communications 2024-12, Vol.739, p.150963, Article 150963
• Main Authors: Nakagaki, Ryutaro, Mukaibo, Taro, Monir, Ahmed, Gao, Xin, Munemasa, Takashi, Nodai, Tomotaka, Tamura, Akiko, Obikane, Yui Hirata, Kondo, Yusuke, Masaki, Chihiro, Hosokawa, Ryuji
• Format: Article
• Language: English
• Subjects: Bone mineralization; Microgravity; Osteocyte differentiation; Spaceflight bone loss
• ISSN: 0006-291X; 1090-2104; 1090-2104
• DOI: 10.1016/j.bbrc.2024.150963

This study investigates the effects of microgravity on the differentiation and mineralization of IDG-SW3 osteocyte-like cells to understand the response of bone cells to microgravity and develop strategies to mitigate bone loss in astronauts. IDG-SW3 cells were cultured in collagen-coated dishes and subjected to a 3D clinostat to simulate microgravity 14 days after initiating differentiation. The static group remained under normal gravity. Cells were analyzed on days 14, 18, 22, and 26. Alizarin red staining demonstrated a substantial and time-dependent increase in mineralization in the static group, whereas the microgravity group exhibited little detectable mineralization throughout the experimental period. Quantitative RT-PCR revealed significant upregulation of Rankl, Alpl, Dmp1, and Fgf23 and downregulation of Sost and Phex in the microgravity group. RNA sequencing on day 26 showed distinct gene expression profiles between conditions. Heatmaps highlighted upregulated genes (Ptgs2, Alpl, Comp, Atf4, Lox) and downregulated genes (Rspo2, Ank, Ptn, Mmp13, Aspn, Spp1) under microgravity. Gene ontology (GO) enrichment analysis indicated that upregulated genes were associated with cytoskeletal organization and receptor activities, while downregulated genes were linked to extracellular matrix components and immune response. These findings provide insights into the molecular mechanisms of bone loss in space and emphasize the importance of gravity in bone remodeling. Future studies should validate these genes' functions in osteocyte biology under microgravity. •Microgravity inhibits mineralization in osteocyte-like IDG-SW3 cells.•Microgravity enhances Rankl, Dmp1, and Fgf23; suppresses Phex, Sost in osteocytes.•RNA-seq reveals 174 up-regulated and 181 down-regulated genes under microgravity.•Microgravity alters gene expression related to cytoskeletal cytoskeletal, extracellular matrix, and metabolism.•Novel insights into molecular mechanisms contributing to bone loss during space flight.