Integrative transcriptomic and proteomic analysis show circulating osteoprogenitors to have a mixed immune and mesenchymal progenitor function in humans

Circulating osteoprogenitor (COP) are a population of cell in the peripheral circulation that possess functional and phenotypical characteristics of multipotent stromal cells (MSCs). While there is functional overlap, it is not known how COP cells are related to bone marrow (BM)-derived MSCs (BM-MSCs) and other better characterized stromal progenitor populations such as adipose-derived stromal cells (ASCs). This study compares COP cells to BM-MSCs and ASCs through detailed transcriptomic and proteomic analyses. COP cells have a distinct gene and protein expression pattern to BM-MSCs and ASCs, with a significantly stronger immune footprint, likely owing to their hematopoietic lineage. However, they also have a similar pattern of expression BM-MSCs and ASCs, in genes and proteins in progenitor cell differentiation and proliferation pathways. This study shows COP cells to be a unique but functionally similar population to BM-MSCs and ASCs, sharing their proliferation and differentiation capacity, but with a strong immune phenotype, with potential for translational regenerative medicine strategies.