Knockdown of MACF1 inhibits the migration and cytoskeletal arrangement of pre-osteoclasts induced by simulated microgravity

Abstract

Bone loss remains a major health concern for astronauts during space flight. Increased osteoclast activity is one of the main causes of bone loss in astronauts subjected to microgravity conditions. However, the underlying molecular mechanisms remain unclear. Microtubule actin crosslinking factor 1 (MACF1) has been implicated in the regulation of cytoskeletal distribution, cell migration, and cell differentiation. Our previous studies have shown that MACF1 promotes the differentiation of pre-osteoclasts. However, whether MACF1 regulates the migration and cytoskeletal arrangement of pre-osteoclasts under microgravity conditions has not yet been elucidated. In this study, we used a hind-limb unloading (HLU) mouse model and a random positioning machine (RPM) to simulate the effects of microgravity on pre-osteoclasts. In the HLU mouse model, the expression of MACF1 was upregulated in primary pre-osteoclasts of mice, accompanied by enhanced migration in vivo. Moreover, simulated microgravity using the RPM also promoted MACF1 expression and migration of pre-osteoclasts in vitro. Additionally, knockdown of MACF1 disrupted cytoskeletal arrangement (F-actin and microtubules) and further inhibited the migration of pre-osteoclasts via the RhoA/ROCK1 signaling pathway. We further demonstrated that knockdown of MACF1 disrupted the enhanced migration and cytoskeleton arrangement of pre-osteoclasts induced by simulated microgravity. These data demonstrate that MACF1 positively regulates the migration and cytoskeletal organization of pre-osteoclasts under simulated microgravity, suggesting that MACF1 may be a therapeutic target for the treatment of bone loss induced by microgravity.