Macrophage type modulates osteogenic differentiation of adipose tissue MSCs

Abstract

Since the reconstruction of large bone defects remains a challenge, knowledge about the biology of bone healing is desirable to develop novel strategies for improving the treatment of bone defects. In osteoimmunology, macrophages are the central component in the early stage of physiological response after bone injury and bone remodeling in the late stage. During this process, a switch of macrophage phenotype from pro-inflammatory (M1) to anti-inflammatory (M2) is observed. An appealing option for bone regeneration would be to exploit this regulatory role for the benefit of osteogenic differentiation of osteoprogenitor cells (e.g., mesenchymal stem cells; MSCs) and to eventually utilize this knowledge to improve the therapeutic outcome of bone regenerative treatment. In view of this, we focused on the in vitro interaction of different macrophage subtypes with adipose tissue MSCs to monitor the behavior (i.e. proliferation, differentiation and mineralization) of the latter in dedicated co-culture models. Our data show that co-culture of MSCs with M2 macrophages, but not with M1 macrophages or M0 macrophages, results in significantly increased MSC mineralization caused by soluble factors. Specifically, M2 macrophages promoted the proliferation and osteogenic differentiation of MSCs, while M0 and M1 macrophages solely stimulated the osteogenic differentiation of MSCs in the early and middle stages during co-culture. Secretion of the soluble factors oncostatin M (OSM) and bone morphogenetic protein 2 (BMP-2) by macrophages showed correlation with MSC gene expression levels for OSM-receptor and BMP-2, suggesting the involvement of both signaling pathways in the osteogenic differentiation of MSCs.Electronic supplementary materialThe online version of this article (doi:10.1007/s00441-017-2598-8) contains supplementary material, which is available to authorized users.

Coculture with monocytes/macrophages modulates osteogenic differentiation of adipose‐derived mesenchymal stromal cells on poly(lactic‐co‐glycolic) acid/polycaprolactone scaffolds

“…However, given the cell behavioural difference in 3D and 2D culture systems and the fact that 3D scaffolds are a crucial part of cell‐based bone constructs, we here established a direct 3D coculture system by using human primary ADMSCs, THP‐1 cells and electrospun scaffolds. In contrast to the previously observed stimulatory effects of macrophages on the osteogenic differentiation of ADMSCs (Zhang et al, ), monocytes, M1 macrophages, and M2 macrophages significantly inhibited the osteogenic differentiation of cocultured ADMSCs. This is evidenced by decreased ALP activity, mineralization content, and expression of several osteogenic markers.…”

“…Immunofluorescence images were acquired with a fluorescence microscope (Zeiss AxioCam MRc5, Carl Zeiss Microimaging GmbH, Germany), and the relative intensity of fluorescence was analysed using ImageJ (U.S. National Institutes of Health, Bethesda, USA). The value of red (Alexa 568) and green (Alexa 488) fluorescence of each sample was further normalized for the value of blue fluorescence (DAPI), as described previously (Zhang et al, ).…”

1,25-Dihydroxyvitamin D suppresses M1 macrophages and promotes M2 differentiation at bone injury sites

“…In contrast to the scarce reports available on the role of macrophages in MSC recruitment, the role of macrophages in osteogenic differentiation of MSCs was intensively studied. Although the importance of M1 macrophage-associated molecules (i.e., OSM, TNF-α, and IL-6) for bone repair was convincingly demonstrated using animals deficient in these molecules (11,(31)(32)(33); data from other in vitro studies concerning the relative role of M1 and M2 macrophages in MSC osteogenic differentiation were not consistent (11)(12)(13)34). We reasoned that this inconsistency of the data obtained from in vitro osteogenic differentiation assays might be caused by the experimental setup in which most designs added either M1 or M2 macrophages into a coculture system that lasted 3-4 weeks.…”

Interactions between monocytes, mesenchymal stem cells, and implants evaluated using flow cytometry and gene expression

“…Implant surface properties, including roughness, chemistry, wettability, and surface charge, have been shown to influence the gene expression and/or secretion of several proinflammatory and anti‐inflammatory cytokines in monocultures of human monocytes or murine macrophages (Brodbeck et al, ; Hotchkiss et al, ). Besides, a recent study showed that direct co‐cultures of human macrophage cell line (THP‐1) with human MSC on tissue culture polystyrene resulted in significant changes in the number of adherent MSC and their mineralization capacity depending on the polarization (M1/M2) of the co‐cultured THP‐1 macrophages (Zhang et al, ). Therefore, it is crucial to explore if the coexistence of monocytes with MSC on implants with different surfaces will influence the cell–material and cell–cell interactions for both cell types in the co‐culture.…”

“…Besides, a recent study showed that direct co-cultures of human macrophage cell line (THP-1) with human MSC on tissue culture polystyrene resulted in significant changes in the number of adherent MSC and their mineralization capacity depending on the polarization (M1/M2) of the co-cultured THP-1 macrophages (Zhang et al, 2017). Therefore, it is crucial to explore if the coexistence of monocytes with MSC on implants with different surfaces will influence the cell-material and cell-cell interactions for both cell types in the co-culture.…”