* em p /em ? ?0.05 compared to DMSO condition. A decrease in the expression of CCR5, which is usually highly abundant in iDC and involved in their recruitment to the site of inflammation, is accompanied by an increase in the expression of CCR7 that is required for mature DC (mDC) migration toward its ligands CCL19 and CCL21 expressed by lymphatic vessels (2, 8C13). mDC also upregulate protein surface expression of antigen-presenting and co-stimulatory molecules for a proper activation of the T cell responses. Regarding the mechanisms of mDC migration, data from approaches and 3D collagen models showed that this so-called amoeboid migration mode, which refers to crawling amoeba, are used in porous environments. The amoeboid mode is usually integrin and protease impartial, it involves cell contractility induced by activation of RhoA, the Rho-associated protein kinase ROCK and myosin II, and it is characterized by a round cell shape (1, 14C21). Podosomes are adhesion cell structures, which are formed constitutively by macrophages, DC, and osteoclasts (22). The known podosome functions are cell adhesion, substrate rigidity sensing, and matrix degradation (22C28). In addition, podosomes and their cancer cell counterpart, invadopodia, are involved in the protease-dependent cell migration that takes place in dense 3D-environments. This mode is usually integrin-dependent and ROCK-independent. It is usually characterized by an elongated and protrusive cell shape, and it involves proteolytic degradation of the extracellular matrix (ECM) mediated by podosomes in macrophages and osteoclasts precursors (29C31). This migration mode is called mesenchymal migration. Interestingly, while TLR4-mediated human DC maturation by LPS induces the loss of podosomes (32C34), the TLR2-mediated maturation by Pam3CSK4 maintains podosome formation and stability (34), suggesting that DC migration capacity may be differentially regulated by TLR activation. Therefore, in the present study, we hypothesized that this migration capacity of DC in 3D environments could be influenced by the architecture of the PDGFRA matrix, the cell maturation status, and the presence/absence of podosomes. We report that human monocyte-derived DC display amoeboid 3D migration THZ531 in porous matrices of fibrillar collagen I, impartial of their maturation status. We demonstrate that both iDC and mDC can adopt the mesenchymal migration mode to infiltrate 3D dense environments, a process that relies on their capacity to form podosomes. Materials and Methods Dendritic Cell Differentiation and Activation Human monocytes were obtained from blood donors (Etablissement Fran?ais de Sang, EFS, Toulouse). For this report, written informed consents were obtained from all the donors under EFS contract n21/PLER/TOU/IPBS01/2013-0042. According to articles L1243-4 and R1243-61 of the French Public Health Code, the contract was approved by the French Ministry of Science and Technology (agreement number AC 2009-921). All subjects gave written informed consent in accordance with the Declaration of Helsinki. Monocyte-derived macrophages and DC were differentiated as previously described (29, 35). Briefly, purified CD14+ monocytes were seeded in 24-well plates (5??105 cells/well) with RPMI 1640 supplemented THZ531 with 10% FCS, human IL-4 (Miltenyi Biotec) at 20?ng/mL, and human GM-CSF (Miltenyi Biotec) at 10?ng/mL. Cells were allowed to differentiate for 5C7?days. Fresh culture medium was added at day 3 of differentiation. For DC activation, cells were stimulated overnight with either LPS (from O111:B4, Sigma-Aldrich) at 10?ng/mL, Pam3CSK4 (Synthetic triacylated lipoprotein, Invivogen) at 100?ng/mL, or PGE2 (Prostaglandin E2, kindly provided by Agns Coste (PharmaDev, Toulouse)) at 5?M, then harvested and used for the following assays. We also used ultra-pure LPS (from O111:B4, Invivogen) and obtained similar results as those obtained with LPS from Sigma. Flow Cytometry Immature DC, mDC-LPS, mDC-Pam3CSK4 and, iDC treated with PGE2 were harvested by gentle flushing with 1?mL of culture medium, centrifuged for 5?min at 340?g, incubated in staining buffer (PBS, 2?mM EDTA, 0.5% FBS) with a 1:100 dilution of Human TruStain FcX (Biolegend) for 5?min THZ531 at room temperature. Cells were then stained in cold staining buffer for 25?min with fluorophore-conjugated antibodies (APC-Cy7 labeled anti-HLA-DR (clone: L243, 1/400), PE labeled anti-CD80 (clone: 2D10, 1/200), PerCP-Cy5.5 labeled anti-CD86 (clone: IT2.2, 1/400), Pacific Blue labeled anti-PD-L1 (clone: 29E.2A3, 1/400), PerCP-Cy5.5 labeled anti-CCR5 (clone: J418J1, 1/400), and PE labeled anti-CCR7 (clone: G043H7, 1/400)) from Biolegend. After staining, the cells were washed with cold staining buffer, centrifuged twice for 5?min at 340?g at 4C, and analyzed by flow cytometry using LSR-II flow cytometer (BD Biosciences) and the associated BD FACSDiva software. Data were then analyzed using the FlowJo 7.6.5 software (TreeStar). 3D Migration Assay Fibrillar (2.15 or 4?mg/mL) and gelled (5.15?mg/mL) collagen I, and Matrigel were prepared as previously described (29). Matrices (100?L) were polymerized for 1?h and 30?min, respectively, in Transwell Invasion Chambers (BD Falcon) within 24-well companion plates. The.