Single-cell RNA sequencing reveals classical monocytes are the major precursors of rat osteoclasts

Jirui Wen,Xueling He,Wenchao Wu,Liang Li,Xinghong Yao,Mingyue Bao,Min Tang

doi:10.32604/biocell.2022.016915

Abstract

To dissect which subset of bone marrow monocyte is the major precursor of osteoclast, 3-month-old rat bone marrow was obtained for single-cell RNA sequencing. A total of 6091 cells were acquired for detailed analysis, with a median number of 1206 genes detected per cell and 17,959 genes detected in total. A total of 19 cell clusters were recognized, with the main lineages identified as B cells, Granulocytes, Monocytes, T cells, Erythrocytes and Macrophages. Monocytes were further divided into classical monocytes and non-classical monocytes. Compared with non-classical monocytes, classical monocytes highly expressed osteoclast differentiation related genes Mitf, Spi1, Fos and Csf1r. Additionally, biological processes of classical monocytes were related to osteoclast differentiation. qPCR revealed differentially expressed genes of classical monocytes played a role in osteoclast differentiation. In conclusion, classical monocytes were identified as the main precursors of osteoclasts in rats, and may contribute to osteoclast differentiation by regulating S100a4, S100a6, S100a10, Fn1, Vcan and Bcl2a1. The results of this study contribute to the understanding of the origin of osteoclasts and may provide potential biomarkers for early diagnosis of bone metabolic diseases, as well as molecular and cellular targets for clinical intervention in bone metabolic diseases.

Highlights

Osteoclasts are the main functional cells in bone resorption, which play an important role in bone development, growth, repair and reconstruction (Kurotaki et al, 2020)
Main lineages in rat bone marrow Following the procedure for tissue separation, single cell isolation and high-throughput single cell RNA sequencing (Fig. 1A), a total of 6091 cells were obtained with a median read of 44876 per cell and a median number of 1206 genes detected per cell
Identification of subsets of monocytes The newly developed method for monocyte subsets categorization in rats was based on the differential expression of CD43, and low CD43 expression was found in classical monocytes (Dijkstra et al, 1994)

Summary

Introduction

Osteoclasts are the main functional cells in bone resorption, which play an important role in bone development, growth, repair and reconstruction (Kurotaki et al, 2020). Understanding the origin of osteoclasts is the key to study the etiology and prevention of bone resorption-related clinical bone metabolic diseases. Monocytes are cells of the mononuclear phagocyte system which originate from hematopoietic precursor cells (Udagawa et al, 2020). Monocytes can perform multiple functions including supporting tissue homeostasis, mediating host defense, initiating inflammation and differentiating into osteoclasts (Shi and Pamer, 2011). Through CD14 and CD16, human monocytes can be divided into three subsets: the CD14++CD16– classical monocytes, CD14++ CD16+ intermediate monocytes and CD14+CD16++ nonclassical monocytes (Ziegler-Heitbrock et al, 2010).

Objectives

Methods

Results

Conclusion