Detection and properties of the human proliferative monocyte subpopulation

Abstract

Peripheral blood monocyte subpopulations have been reported and can give rise to diverse, differentiated phenotypes. A subpopulation(s) of human monocytes can proliferate in vitro in response to macrophage-colony stimulating factor (M-CSF; or CSF-1). This population, termed the proliferative monocyte (PM), is presumably less mature than other monocytes; however, it has not been defined further. Previous studies monitoring the frequency of the slowly cycling PM from different donors indicated that the assay for their reproducible measurement required improvement. We demonstrate that for optimal PM detection, high 5-bromo-2'-deoxyuridine concentrations are required over a delayed and wide time-frame. Surface marker phenotyping by flow cytometry showed that freshly isolated PM are CD14+ and could be distinguished from two other human monocyte subpopulations, namely, the CD14lo CD16+ and CD14lo CD64- subsets. PM express relatively high levels of CD64 and CD33 but have relatively low CD13 expression; they are also c-Fms+ and human leukocyte antigen-DR+. Labeling with carboxyfluorescein diacetate succinimidyl ester (CFSE) enabled the estimation of the number of PM divisions over time. Following CFSE labeling and culture, PM were sorted from the nonproliferating population and shown to have a distinctive, spindle-shaped morphology and higher capacity to form multinucleated, tartrate-resistant acid phosphatase+ cells in the presence of M-CSF and receptor activator of nuclear factor-kappaB ligand. The phenotype and properties of the PM subpopulation were examined as a prelude to determining its role in disease using methods that can be applied to clarify human monocyte heterogeneity.

Comparative Analysis of Monocyte Subsets in the Pig

“…We recently described the ability of CSF1 to generate a pure population of macrophages from pig bone marrow (2). Clanchy et al (31) carried out a detailed study of the proliferative response of human blood monocytes to CSF1 and demonstrated that around 30% of cells within the CD14 hi population could go through at least one cell division over 6-8 d. Although we have not quantitated the proliferative pool, the data in Fig. 2 suggest that cultivation in CSF1 leads to a very large increase in monocyte numbers in pig PBMC cultures, detected most effectively by expression of CD172a and the appearance of cells with increased size and granularity.…”

The dynamics of macrophage lineage populations in inflammatory and autoimmune diseases

“…It has been suggested that this proliferative subpopulation has a proinflammatory phenotype, since it could be the subpopulation that has most recently emigrated from bone marrow and that could also give rise to any proliferative macrophages in inflamed tissue (142). It has been reported that this relatively immature subpopulation is distinct from the CD14 low CD16ϩ population and contains osteoclast precursors (143). More information on human blood monocyte maturation and the possible trafficking of different populations during chronic inflammation is needed.…”

“…A subpopulation of human blood monocytes has been observed to proliferate in vitro in response to M-CSF and GM-CSF (141)(142)(143). It has been suggested that this proliferative subpopulation has a proinflammatory phenotype, since it could be the subpopulation that has most recently emigrated from bone marrow and that could also give rise to any proliferative macrophages in inflamed tissue (142).…”

The effect of bisphosphonate treatment on osteoclast precursor cells in postmenopausal osteoporosis: The TRIO study

“…In-vitro studies have demonstrated that M-CSF binds to the M-CSF (c-fms) receptor and induces the expression of genes in the osteoclast lineage leading to the differentiation and development of mature osteoclasts and cell survival (3,9). TNF-is an inflammatory cytokine that binds to the TNF receptors-1 and -2, stimulates osteoclastogenesis and regulates cell apoptosis (10). In addition osteoclast precursor cells express 2 integrins such as CD11b/Cd18) adhesion molecules that are necessary for cell trafficking and differentiation (11).…”