title: Effect of monocytes/macrophages on the early osteogenic differentiation of hBMSCs.
abstract: Heterotypic cell interactions are essential for the homeostasis of bone tissue, in particular the widely studied interaction between osteoblasts and osteoclasts. Closely related with osteoclasts are monocytes/macrophages. These have been shown to produce osteogenic factors, e.g. BMP-2, which plays a key role in bone metabolism. However, the mechanisms through which monocytes/macrophages interact with osteoblasts are still elusive. The aim of this work was to assess the influence of human peripheral blood monocytes/macrophages over the early osteogenic differentiation of human bone marrow stromal cells (hBMSCs) in the presence of dexamethasone-supplemented medium. The co-cultures were performed using porous transwells that allowed the interaction between both cell types through the production of paracrine factors. The potential effect of BMP-2 produced by monocytes/macrophages was addressed by adding an anti-BMP-2 antibody to the co-cultures. hBMSCs cultured in the presence of monocytes/macrophages had a higher proliferation rate than hBMSCs monocultures. The quantification of early osteogenic marker alkaline phosphatase (ALP) revealed higher activity of this enzyme in cells in the co-culture throughout the time of culture. Both of these effects were inhibited by adding an anti-BMP-2 antibody to the cultures. Moreover, qRT-PCR for osteocalcin and osteopontin transcripts showed overexpression of both markers. Once again, the effect of monocytes/macrophages over hBMSC osteogenic differentiation was completely inhibited in the co-cultures by blocking BMP-2. The present report confirmed that monocytes/macrophages produce BMP-2, which promotes osteogenic differentiation and proliferation of hBMSCs cumulatively to dexamethasone-supplemented medium. This potentially implies that monocyte/macrophages play a stronger role in bone homeostasis than so far supposed.
authors.affiliation: 3B's Research Group-Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark, 4806-909 Taipas, Guimarães, Portugal.
authors.forename: R P
authors.initials: RP
authors.lastname: Pirraco
authors.forename: R L
authors.initials: RL
authors.lastname: Reis
authors.forename: A P
authors.initials: AP
authors.lastname: Marques
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D002452:Cell Count; D002454:Cell Differentiation / Q000235:genetics; D049109:Cell Proliferation; D004247:DNA / Q000378:metabolism; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006801:Humans; D006868:Hydrolysis; D008264:Macrophages / Q000166:cytology* / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000201:enzymology; D009000:Monocytes / Q000166:cytology* / Q000378:metabolism; D009596:Nitrophenols / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000378:metabolism; D015675:Osteocalcin / Q000235:genetics / Q000378:metabolism; D010012:Osteogenesis / Q000235:genetics; D053495:Osteopontin / Q000235:genetics / Q000378:metabolism
chemical_list: D009596:Nitrophenols; D009943:Organophosphorus Compounds; D015675:Osteocalcin; D053495:Osteopontin; C008644:nitrophenylphosphate; D004247:DNA; D000469:Alkaline Phosphatase