Exosomes Regulate Interclonal Communication on Osteogenic Differentiation Among Heterogeneous Osteogenic Single-Cell Clones Through PINK1/Parkin-Mediated Mitophagy.

Dongdong Fei,Qiming Zhai,Feng Zhou,Yan Jin,Bei Li,Xiaoning He,Yanmin Xia,Wanmin Zhao,Yazheng Wang,Qintao Wang

doi:10.3389/fcell.2021.687258

Dongdong Fei, Qiming Zhai + Show 8 more

Open Access

https://doi.org/10.3389/fcell.2021.687258

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Abstract

Mesenchymal stem cells (MSCs) are intrinsically heterogeneous and are comprised of distinct subpopulations that differ in their differentiation potential. A deeper understanding of the heterogeneity and intercellular communication within these heterogeneous subpopulations has significant implications for the potential of MSC-based therapy from the bench to the clinic. Here, we focused on the clonal osteogenic heterogeneity of periodontal ligament stem cells (PDLSCs) and explored how interclonal communication affects the osteogenic differentiation among these heterogeneous single-cell colonies (SCCs), and sought to determine the underlying mechanisms. Alkaline phosphatase (ALP) and Alizarin red staining identified the presence of SCCs with high (H-SCCs) and low osteogenic ability (L-SCCs). Conditioned medium derived from H-SCCs (H-CM) promoted mineralized nodule formation to a greater extent than that derived from L-SCCs (L-CM), which served as the target cells (TCs). However, treatment with the exosome biogenesis/release inhibitor GW4869 reduced the H-CM- and L-CM-related osteogenic differentiation-promoting potential. We further found that exosomes secreted by H-SCCs (H-Exo) were superior to those secreted by L-SCCs (L-Exo) in promoting the osteogenic differentiation of TCs. Mechanistically, TCs stimulated with H-CM and H-Exo exhibited higher levels of PINK1/Parkin-mediated mitophagy, while gain- and loss-of-function experiments showed that PINK1/Parkin-mediated mitophagy was positively associated with SCC osteogenic differentiation. Furthermore, PINK1 knock-down in H-Exo- and L-Exo-stimulated TCs inhibited their osteogenic differentiation through inhibiting PINK1/Parkin-mediated mitophagy. Our study uncovers a previously unrecognized mechanism that an exosome-mediated PINK1/Parkin-dependent mitophagy regulates interclonal communication among SCCs with osteogenic heterogeneity.

Highlights

Periodontal ligament stem cells (PDLSCs), a type of mesenchymal stem cell (MSC), play an important role in the restoration and regeneration of alveolar bone (Huang et al, 2009)
We investigated the effect of L-CM on the osteogenic differentiation of H-single-cell colonies (SCCs), with RT-qPCR and Alizarin red staining analysis indicating that L-CM treatment did not significantly promote the expression of the osteogenic-related genes RUNX2 and OCN in H-SCCs (Supplementary Figure 1A) and increase the formation of mineralized nodules in H-SCCs (Supplementary Figure 1B)
We focused on the clonal osteogenic heterogeneity of PDLSCs and explored interclonal communication on the osteogenic differentiation among these heterogeneous osteogenic

Summary

Introduction

Periodontal ligament stem cells (PDLSCs), a type of mesenchymal stem cell (MSC), play an important role in the restoration and regeneration of alveolar bone (Huang et al, 2009). These cells have been used to treat alveolar bone loss in periodontitis patients, their therapeutic effect remains controversial (Chen et al, 2016). Several recent studies have provided novel insights into the regulation of PINK1/Parkin-dependent mitophagy on the osteogenic differentiation of MSCs (Marycz et al, 2016; Pei et al, 2018). No study has shed light on the role of PINK1/Parkinmediated mitophagy in interclonal osteogenic heterogeneity and osteogenic differentiation-related communication

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