Discovering Myeloid Cell Heterogeneity in Mandibular Bone – Cell by Cell Analysis

Abstract

The myeloid-derived bone marrow progenitor populations from different anatomical locations are known to have diverse osteoclastogenesis potential. Specifically, myeloid progenitors from the tibia and femur have increased osteoclast differentiation potential compared to myeloid progenitors from the alveolar process. In this study, we explored the differences in the myeloid lineage progenitor cell populations in alveolar (mandibular) bone versus long (femur) bone using flow cytometry and high-throughput single cell RNA sequencing (scRNA-seq) to provide a comprehensive transcriptional landscape. Results indicate that mandibular bone marrow-derived cells exhibit consistent deficits in myeloid differentiation, including significantly fewer myeloid-derived suppressor cell (MDSC)-like populations (CD11b+Ly6C+, CD11b+Ly6G+), as well as macrophages (CD11b+F4/80+). Although significantly fewer in number, MDSCs from mandibular bone exhibited increased immunosuppressive activity compared to MDSCs isolated from long bone. Using flow cytometry panels specific for bone marrow progenitors, analysis of hematopoietic stem cells showed no defects in mandibular bone marrow in LSK (Lin–Sca1+cKit+) cell and LK (Lin–Sca1–cKit+) cell populations. While there was no significant difference in granulocyte progenitors, the granulocyte-monocyte progenitors and monocyte progenitor population were significantly decreased in the mandibular bone marrow. T-lymphocyte subsets were not significantly different between mandibular and femoral bone, except for CD4+CD25+Foxp3+ regulatory T lymphocytes, which were significantly increased in the mandible. In addition, B lymphocytes were significantly increased in mandible. Single cell RNA sequencing from mandible and femur BM revealed distinct differences in transcriptomic profiles in myeloid populations establishing previously unappreciated aspects of mandibular bone marrow populations. These analyses reveal site-specific differences in the myeloid progenitor cellular composition and transcriptional programs providing a deeper appreciation of the complex differences in myeloid cell heterogeneity from different anatomical bone marrow sites.

Tristetraprolin limits age-related expansion of myeloid-derived suppressor cells

“…For detailed identification with a focus on M-MDSCs, we first classified monocyte clusters from UMAP, as previously described ( 25 ). The monocyte population was then further divided into 10 distinct sub-clusters, and the distributions of the monocyte sub-clusters also differed from one another ( Figure 5D ).…”

“…To compare TTP expression in young and aged mouse models, reference scRNA-seq data was processed from the Tabula Muris Senis (TMS) dataset ( 24 , 25 ). Droplet scRNA-seq data objects were downloaded and loaded into R studio V 4.…”

“…Mapping rates to the reference genome were greater than 95% for all samples. Approximately 16,140 cells from the femurs of WT [previously sequenced in ( 25 )], 15,996 cells from the femurs of cTTPKO, and 15,730 cells from the femurs of TTPKO mice were sequenced. Cells with abnormal gene detection rates (< 200 and > 6000) and high mitochondrial transcriptional load (> 15%), an indicator of cellular stress, were reported as outliers and filtered out of the analysis.…”

Single‐cell RNA sequencing in oral science: Current awareness and perspectives

“…Differences in myeloid progenitor cell populations in alveolar bone and long bone were compared. There were significantly fewer myeloid‐derived suppressor cells (MDSCs) in alveolar bone but they exhibited higher immunosuppressive activity 43 . The immune cell atlas of alveolar bone revealed by scRNA‐seq laid a solid foundation for in‐depth research on how alveolar bone plays an essential role in orthodontic tooth movement, and reacts to inflammatory diseases, occlusal stress stimulation etc.…”

“…There were significantly fewer myeloid‐derived suppressor cells (MDSCs) in alveolar bone but they exhibited higher immunosuppressive activity. 43 The immune cell atlas of alveolar bone revealed by scRNA‐seq laid a solid foundation for in‐depth research on how alveolar bone plays an essential role in orthodontic tooth movement, and reacts to inflammatory diseases, occlusal stress stimulation etc. For example, it is believed that the overreaction of the innate and acquired immune systems induced by dental plaque deteriorates periodontal tissues in periodontal lesions.…”