AccScience Publishing / IJB / Online First / DOI: 10.36922/ijb.3959
RESEARCH ARTICLE
Early Access

Osteocytic PGE2 receptors EP2/4 signaling create a physiological osteogenic microenvironment in polycaprolactone 3D module

Jingjing Chen1 Qiuling Guo1 Jinling Zhang1 Ying Zhang1 Yangxi Liu1 Pengtao Wang1 Chengzhu Zhao1 Linda F Bonewald2, * Xiaolin Tu1,3, *
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1 Laboratory of Skeletal Development and Regeneration, Key Laboratory of Clinical Laboratory Diagnostics (Ministry of Education), College of Laboratory Medicine, Chongqing Medical University, Chongqing, China.
2 Indiana Center for Musculoskel Health, Indiana University School of Medicine, Indianapolis, IN, USA
3 Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN, USA
Submitted: 17 June 2024 | Accepted: 6 August 2024 | Published: 8 August 2024
(This article belongs to the Special Issue Made-to-order Organ)
© 2024 by the Author(s). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International License ( https://creativecommons.org/licenses/by/4.0/ )
Abstract

3D bioprinting is a focused field in orthopedics, and its application with physiological osteogenic microenvironments (POME) is a prerequisite for authentic bone reconstruction. Mechanical stimulation produces PGE2 in mechanosensory osteocytes, but it is still unclear whether osteocytic PGE2 is a POME. PGE2 is an inducer of osteogenesis by acting on bone marrow stromal cells through its receptors EP2/EP4 to initiate osteogenic differentiation and mineralization. Unfortunately, clinical trials of PGE2 have shown side effects, including fever and drowsiness, so targeting the PGE2 receptor on specific tissues can avoid side effects. Here, we show that MLO-Y4 osteocytes treated with EP2/EP4 agonists for 24 h develop the functions of promoting osteogenic differentiation and mineralization while inhibiting adipogenesis of the stromal cell line ST2 and inducing tubule formation and angiogenic marker expression in HUVEC cells. Mechanistically, activation of the PGE2 signaling pathway in osteocytes appears to have autocrine effects by inducing the expression of the EP2 and EP4 receptors and COX-2 (Ptgs2), further auto-amplifying PGE2 signaling. PGE2 produced by the treated MLO-Y4 cells appears responsible for osteogenesis in addition to other unknown factors. MLO-Y4 and ST2 cells were incorporated into POME 3D constructs with greater than 95% viability within 7 days. Treatment of osteocytes with a PGE2 receptor agonist lineally proliferates ST2 cells, enhances the expression of osteoblast markers and mineralization. Due to 3D bioprinting being the closest model to in vivo research, these data showed that osteocytic PGE2 receptor signaling is a safe and mild POME with great potential for translational applications.

Keywords
PGE2
Physiological osteogenic microenvironment
3D bioprinting
Osteogenic differentiation
Angiogenesis
Adipogenesis
Funding
This research was funded by the National Natural Science Foundation of China 82072450 (XL.T.), Chongqing Natural Science Foundation-Innovation and Development Joint Fund CSTB2022NSCQ-LZX0048 (XL.T.) and Young Scientists Fund of the National Natural Science Foundation of China 82202655 (C.Z.).
Conflict of interest
The authors declare they have no competing interests.
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International Journal of Bioprinting, Electronic ISSN: 2424-8002 Print ISSN: 2424-7723, Published by AccScience Publishing