Re-analysis of single-cell RNA-seq data reveals the origin and roles of cycling myeloid cells.

Cycling myeloid cells (CMCs) are often detected from various tissues using single-cell RNA sequencing (scRNA-seq) datasets, however, their research value was not noticed before. For the first time, our study preliminarily revealed the origin, differentiation, and roles of CMCs in physiological processes. Particularly, subgroup a of cycling myeloid cells (aCMCs) were conclusively identified as belonging to a specific cell type. In an active state, aCMCs rapidly proliferate during the early stages of an embryonic development. With an individual maturing, most aCMCs differentiate into specialized cells, while a small portion of them enter an inactive or dormant state. Under pathological conditions, aCMCs restore their proliferative and differentiation capacities via activation or revival. The present study has set the stage for future research on CMCs by linking them with progenitors of immune cells, and provided a crucial starting point to understand the origin, differentiation, and roles of CMCs in various physiological and pathological processes, particularly those related to traumatic injury, cancer, and pathogen infection, leading to develop targeted therapies or interventions.