Osteocyte-derived exosomes inhibit osteoblast activity and induce osteoclast formation

Abstract

Osteocytes, which are the most abundant cell type in bone, regulate osteoblasts and osteoclasts via both cell–cell interactions and paracrine signaling, and osteocyte-derived exosomes might contribute to this paracrine action. In this study, we investigated the effects of osteocyte-derived exosomes on regulating osteoblasts and osteoclasts and studied the potential mechanism. Materials and Methods: Osteocyte-derived exosomes were extracted and identified. PKH67-labeled exosomes were incubated with MC3T3-E1 cells and RAW264.7 cells, and fluorescence confocal microscopy was used to analyze the uptake of exosomes. ALP stain- ing and TRAP staining were used to analyze osteoblast activity and osteoclast formation. The level of miR-214-3p in exosomes was analyzed by qPCR and the incorporation of FAM-labeled miR-214-3p from exosomes into MC3T3-E1 cells was evaluated. The expressions of ephrinA2 and RANKL in exosomes were studied. Results: Our results demonstrated that osteocyte-derived exosomes might recognize osteoblasts through the ephrinA2 protein; thus, miR-214-3p in exosomes was transferred into osteoblasts to inhibit osteoblast activity. Meanwhile, we found that osteocyte-derived exosomes could be transferred into osteoclasts to induce osteoclast formation by releasing RANKL. Conclusion: These findings suggest that osteocyte-derived exosomes play an important role in the regulation of osteoblast and osteoclast activity, which might occur via miR-214-3p and RANKL.

Mesenchymal Stem Cell-Derived Exosomes Enhance 3D-Printed Scaffold Functions and Promote Alveolar Bone Defect Repair by Enhancing Angiogenesis

“…The method used for exosome isolation was performed as previously reported [ 20 ]. Briefly, 10% FBS α-MEM was replaced with 10% exosome-free FBS when the hUCMSCs were 80–90% confluent.…”

“…Exosomes are extracellular vesicles that are released from all cells, prokaryotes, and eukaryotes and have a size range of 40–160 nm in diameter [ 19 , 20 ]. Exosomes derived from stem cells contain many functional proteins, miRNAs, and other bioactive contents that exhibit therapeutic potential similar to that of the original cells [ 21 , 22 , 23 ].…”

Bone Cell Exosomes and Emerging Strategies in Bone Engineering

“…Bone tissue remodeling involves a balance between bone formation and bone resorption process mediated by several signaling mechanisms [1] including direct cell-cell contact [2], cell-matrix interaction [3], autocrine, endocrine (hormones) [4], and paracrine factors (soluble molecules, vesicles, and growth factors) between bone cells [5][6][7] and their microenvironment. There is growing evidence now that the cells involved in bone remodeling also secrete extracellular vesicles (EVs), which influence bone cell crosstalk by regulating bone cell proliferation, differentiation, migration, apoptosis, and metabolism through various signaling pathways [8][9][10]. Extracellular vesicles are a heterogeneous population of phospholipid bilayer membrane-bound vesicles classified into exosomes (40-120 nm), microvesicles (50-1000 nm), and apoptotic bodies (500-2000 nm) depending on their origin, size, and function [11,12].…”