Recent Advances in Single-Cell View of Mesenchymal Stem Cell in Osteogenesis

Abstract

Osteoblasts continuously replenished by osteoblast progenitor cells form the basis of bone development, maintenance, and regeneration. Mesenchymal stem cells (MSCs) from various tissues can differentiate into the progenitor cell of osteogenic lineage and serve as the main source of osteoblasts. They also respond flexibly to regenerative and anabolic signals emitted by the surrounding microenvironment, thereby maintaining bone homeostasis and participating in bone remodeling. However, MSCs exhibit heterogeneity at multiple levels including different tissue sources and subpopulations which exhibit diversified gene expression and differentiation capacity, and surface markers used to predict cell differentiation potential remain to be further elucidated. The rapid advancement of lineage tracing methods and single-cell technology has made substantial progress in the characterization of osteogenic stem/progenitor cell populations in MSCs. Here, we reviewed the research progress of scRNA-seq technology in the identification of osteogenic markers and differentiation pathways, MSC-related new insights drawn from single-cell technology combined with experimental technology, and recent findings regarding the interaction between stem cell fate and niche in homeostasis and pathological process.

3D Spheroid Cultivation Alters the Extent and Progression of Osteogenic Differentiation of Mesenchymal Stem/Stromal Cells Compared to 2D Cultivation

“…Many aspects influence the variability of the results. For example, the respective MSC type (even subpopulations and cell donor-dependent differences can lead to differences [ 15 , 59 ]), the seeded cell numbers and thus the spheroid size, the composition of the cell culture medium and additives, the growth area or scaffold (if available), and the culture periods can have a significant influence on the final result [ 37 ]. In addition, long-term cultures of MSC tend to spontaneously form spheroids [ 60 , 61 ], which either continue to adhere to the culture dish bottom and coexist with the 2D culture or detach and are inadvertently removed with the following change of culture medium.…”

“…MSC of various tissue origins can differentiate into progenitor cells of the osteogenic lineage and serve as a major source of osteoblasts. MSC respond flexibly to regenerative signals emanating from the surrounding microenvironment, contributing to bone homeostasis and remodeling [ 15 ]. MSC retain many of their stem cell capacities in vitro and are thus a valuable tool for molecular studies of biological factors as well as for testing pharmaceutical compounds.…”

The emerging studies on mesenchymal progenitors in the long bone

“…2 ), mostly associated with arterioles or sinusoidal blood vessels and located in the perivascular space [ 53 ]. Although, reporter genes have been extensively studied to purify osteo-lineage stem/progenitor cell populations, bone marrow stromal cells are being more comprehensively analyzed following the advent of single-cell sequencing [ 54 ]. In order to clarify the cellular taxonomy in mouse bone marrow, Scadden’s lab had performed comprehensive single-cell sequencing for overall stroma cell from bone marrow and demonstrated that the bone marrow comprising Lepr-MSCs, pericytes, 2 subtypes of osteogenic lineage cells, 4 subtypes of chondrocytes, 3 subtypes of endothelial cells and 5 subtypes of fibroblasts.…”

Characterization of the cellular heterogeneity and bone regenerative potential of cultured human periosteal cells

“…Instead of conventional methods for heterogeneity analysis, single-cell RNA-sequencing (scRNA-seq) methods have recently revolutionized transcriptome research and significantly contributed to the identification and classification of distinct cell types and states within a heterogeneous population [ 16 , 17 ]. Significant progress has been made in characterizing MSCs using scRNA-seq techniques, thus increasing our knowledge about the heterogeneity and plasticity of these cells in tissue regeneration [ 18 ]. However, despite these advancements in MSC research, a comprehensive understanding of the heterogeneity of cultured human PCs remains elusive.…”