Uptake of osteoblast-derived extracellular vesicles promotes the differentiation of osteoclasts in the zebrafish scale

Jingjing Kobayashi-Sun,Mika Ikegame,Kei-Ichiro Kitamura,Junpei Kuroda,Shiori Yamamori,Mao Kondo,Nobuo Suzuki,Isao Kobayashi,Masaaki Yamaguchi,Atsuhiko Hattori

doi:10.1038/s42003-020-0925-1

Jingjing Kobayashi-Sun, Mika Ikegame + Show 8 more

Open Access

https://doi.org/10.1038/s42003-020-0925-1

Copy DOI

Abstract

Differentiation of osteoclasts (OCs) from hematopoietic cells requires cellular interaction with osteoblasts (OBs). Due to the difficulty of live-imaging in the bone, however, the cellular and molecular mechanisms underlying intercellular communication involved in OC differentiation are still elusive. Here, we develop a fracture healing model using the scale of trap:GFP; osterix:mCherry transgenic zebrafish to visualize the interaction between OCs and OBs. Transplantation assays followed by flow cytometric analysis reveal that most trap:GFPhigh OCs in the fractured scale are detected in the osterix:mCherry+ fraction because of uptake of OB-derived extracellular vesicles (EVs). In vivo live-imaging shows that immature OCs actively interact with osterix:mCherry+ OBs and engulf EVs prior to convergence at the fracture site. In vitro cell culture assays show that OB-derived EVs promote OC differentiation via Rankl signaling. Collectively, these data suggest that EV-mediated intercellular communication with OBs plays an important role in the differentiation of OCs in bone tissue.

Highlights

Differentiation of osteoclasts (OCs) from hematopoietic cells requires cellular interaction with osteoblasts (OBs)
Confocal imaging of extracted scales revealed that osterix: mCherry+ cells were distributed throughout the scale including the epidermis and dermis area under physiological conditions, while osterix:mCherrybright cells were limited at the edge region of the scale
We found that the number of mCh+ Hoelow particles was approximately three times higher in the fractured scale than the intact scale, suggesting that OB-derived extracellular vesicles (EVs) are released in response to fracture stress (Fig. 5e)

Summary

Introduction

Differentiation of osteoclasts (OCs) from hematopoietic cells requires cellular interaction with osteoblasts (OBs). To isolate and characterize OCs and OBs in the fractured scale, cells were collected from scales in trap:GFP; osterix:mCherry doubletransgenic animals and analyzed by flow cytometry (FCM).

Results

Conclusion