■骨细胞是骨骼中主要的应力感应细胞。骨细胞在机械负荷下分泌的物质在维持体内稳态中起着至关重要的作用。最近发现骨细胞释放外泌体进入循环,但它们是否受机械负荷的影响或参与调节系统稳态仍不清楚。
■我们使用尾部悬吊模型实现了对骨细胞的机械卸载。骨细胞特异性CD63报告小鼠用于骨细胞外泌体追踪。进行外泌体检测和抑制剂处理以确认机械负载对骨细胞外泌体分泌的影响。共同文化,GW4869和外泌体处理用于研究骨细胞来源的外泌体在棕色脂肪组织(BAT)和原代棕色脂肪细胞上的生物学功能。使用骨细胞特异性DicerKO小鼠筛选负载敏感的miRNA。进行双荧光素酶测定以验证所选择的靶基因。
■首先,我们发现受尾悬小鼠的BAT中的产热活性增加,这是由于未加载的骨对循环外泌体的影响。Further,我们发现骨细胞外泌体的分泌受机械负荷的调节,骨细胞来源的外泌体可以达到BAT并影响产热活性。更重要的是,我们在体内和体外证实了骨细胞外泌体对BAT的影响。最后,我们发现,外泌体中所含的let-7e-5p受到机械负荷的调节,并通过靶向Ppargc1a调节BAT的产热活性。
■来自骨细胞的外泌体对负载敏感,在调节BAT方面发挥着至关重要的作用,表明外泌体分泌的调节可以恢复稳态。
■这项研究为使用骨细胞外泌体作为调节BAT甚至全身稳态的潜在药物提供了生物学原理。也为航天等机械卸载条件提供了新的病理基础和新的治疗途径。
UNASSIGNED: Osteocytes are the main stress-sensing cells in bone. The substances secreted by osteocytes under mechanical loading play a crucial role in maintaining body homeostasis. Osteocytes have recently been found to release exosomes into the circulation, but whether they are affected by mechanical loading or participate in the regulation of systemic homeostasis remains unclear.
UNASSIGNED: We used a tail-suspension model to achieve mechanical unloading on osteocytes. Osteocyte-specific CD63 reporter mice were used for osteocyte exosome tracing. Exosome detection and inhibitor treatment were performed to confirm the effect of mechanical loading on exosome secretion by osteocytes. Co-culture, GW4869 and exosome treatment were used to investigate the biological functions of osteocyte-derived exosomes on brown adipose tissue (
BAT) and primary brown adipocytes. Osteocyte-specific Dicer KO mice were used to screen for loading-sensitive miRNAs. Dual luciferase assay was performed to validate the selected target gene.
UNASSIGNED: Firstly, we found the thermogenic activity was increased in
BAT of mice subjected to tail suspension, which is due to the effect of unloaded bone on circulating exosomes. Further, we showed that the secretion of exosomes from osteocytes is regulated by mechanical loading, and osteocyte-derived exosomes can reach BAT and affect thermogenic activity. More importantly, we confirmed the effect of osteocyte exosomes on
BAT both in vivo and in vitro. Finally, we discovered that let-7e-5p contained in exosomes is under regulation of mechanical loading and regulates thermogenic activity of BAT by targeting Ppargc1a.
UNASSIGNED: Exosomes derived from osteocytes are loading-sensitive, and play a vital role in regulation on
BAT, suggesting that regulation of exosomes secretion can restore homeostasis.
UNASSIGNED: This study provides a biological rationale for using osteocyte exosomes as potential agents to modulate
BAT and even whole-body homeostasis. It also provides a new pathological basis and a new treatment approach for mechanical unloading conditions such as spaceflight.