Plasmacytoid dendritic cells (pDCs) competent to make type I interferon were rigorously defined as a Ly-6C ؉ and CD11c Lo subset of the B220 ؉ CD19 ؊ CD43 ؉ CD24 Lo bone marrow (BM) Fraction A. Otherwise similar Ly6C ؊ cells expressed the natural killer (NK) markers DX5 and NK1.1. pDCs represented a stable, discrete, and long-lived population. Stem cells and early lymphoid progenitors (ELPs), but not prolymphocytes, were effective precursors of pDCs, and their differentiation was blocked by ligation of Notch receptors. Furthermore, pDCs were present in the BM of RAG1 ؊/؊ , CD127/IL-7Ra ؊/؊ , and Pax5 ؊/؊ mice. pDCs in RAG1/GFP knock-in mice could be subdivided, and immunoglobulin D H -J H rearrangements, as well as transcripts for the B-lineagerelated genes Pax5, mb1/CD79a, ebf, and Bcl11a, were identified only in the green fluorescent protein-positive (GFP ؉ ) pDC1 subset. All pDCs expressed terminal deoxynucleotidyl transferase (TdT), the ETS transcription factor Spi-B, the nuclear factor-B transcription factor RelB, toll-like receptor 9 (TLR9), and interferon consensus sequence binding protein (ICSBP)/interferon regulatory factor 8 (IRF-8) transcripts; lacked CD16 and granulocyte colony-stimulating factor receptor (G-CSFR); and were uniformly interleukin-7 receptor ␣ (IL-7R␣ ؊ ) AA4.1 Lo , CD27 ؊ , Flk-2 Lo , c-Kit ؊ , DX-5 ؊ , and CD11b ؊ , while CD4 and CD8␣ were variable. GFP ؉ pDC1 subset was less potent than GFP ؊ pDC2s in T allostimulation and production of tumor necrosis factor ␣ (TNF␣), interferon ␣ (IFN␣), and interleukin-6 (IL-6), while only pDC2s made IFN␥ and IL-12 p70. Thus, 2 functionally specialized subsets of pDCs arise in bone marrow from progenitors that diverge from B, T, and NK lineages at an early stage. IntroductionPlasmacytoid dendritic cells (pDCs) are believed to play central roles in defense of viral infection and maintenance of T-cell tolerance. They represent a principal source of type I interferon and can produce inflammatory cytokines such as interleukin-12 (IL-12) p70, IL-6, and tumor necrosis factor ␣ (TNF␣). 1,2 Furthermore, pDCs have been implicated in the pathogenesis of lupus in humans. [3][4][5] While information is rapidly accumulating about pDCs, important questions remain about their origin, heterogeneity, and lifespan. The focus of our study was on pDCs that reside within bone marrow (BM).CD11c Ϫ CD123 Hi HLA class II Hi BDCA (blood dendritic cell antigen) ϩ pDCs were originally defined in human blood and distinguished from conventional CD11c ϩ CD123 Ϫ dendritic cells (DCs). [6][7][8][9] The murine counterparts of human pDCs express CD11c and CD45R/B220, but not CD19, 10,11 while murine DCs as a whole can be divided into CD8 Ϫ and CD8 ϩ subpopulations. 12 Although distinct from classical murine CD8 ϩ DCs, pDCs express variable levels of CD8. 1,13,14 They were formerly defined as CD11c Lo B220 ϩ Gr1 ϩ in spleen and as CD11c ϩ B220 ϩ CD11b Ϫ cells when derived from BM cultured with FMS-like tyrosine kinase 3 ligand (Flt3-L). 15 Expression of Ly6G/Gr1 on pDCs is controve...

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Purpose: To determine the relationship between changes in the extracellular matrix (ECM) and T 1r and T 2 values in vivo. The ECM is composed of proteoglycan (PG), collagen, and water. It has been unclear which of the ECM constituents affects T 1r and T 2 mapping in living human cartilage.Materials and Methods: Sagittal T 1r and T 2 maps were preoperatively obtained from 20 knee osteoarthritis patients. Osteochondral samples harvested from the resected tibial plateaus during total knee arthroplasty were consistent with the MRIs of the patients' knees. Parameters that included histological grading of cartilage degeneration, glycosaminoglycan (GAG) content (which constitutes PG), presence of collagen anisotropy and water content were evaluated along with T 1r and T 2 values, and statistical analysis was performed using multiple regression analysis.Results: T 1r and T 2 values were significantly correlated with the degree of cartilage degeneration (b ¼ 0.397 and 0.357, respectively) and the GAG content (b ¼ À0.340 and À0.244, respectively). Conclusion:The present study demonstrated that T 1r and T 2 values reflect the GAG content of the cartilage and can indicate cartilage degeneration in vivo. Use of these parameters can facilitate the noninvasive diagnosis and evaluation of cartilage degeneration. OSTEOARTHRITIS (OA) IS a degenerative disease that affects the hyaline cartilage at the articular surface.Cartilage matrix breakdown is characterized by changes in the content of glycosaminoglycan (GAG), type II collagen, and water (1). It is difficult to detect these changes in the cartilage matrix using plain radiography or conventional magnetic resonance imaging (MRI) techniques (2,3). However, new MRI techniques that can detect changes in the extracellular matrix (ECM) have recently been developed. In particular, T 1r and T 2 mapping can quantify the ECM of the articular cartilage.The T 1r parameter describes the spin-lattice relaxation in the rotating frame (4). A ''spin-lock'' (SL) pulse is applied to the magnetization in the transverse plane at extremely low fields, and this spin-locked magnetization reflects the changes in the magnetic fields caused by water spin dynamics, such as the chemical exchange of protons. T 1r mapping is most sensitive to changes in the GAG content in the ECM (5-7). A previous in vitro study using a model with selective degradation of GAG by trypsinization revealed that increases in T 1r values correlated with decreases in the GAG content (6,7). The chemical exchanges between bulk water and the hydroxyl and amine groups of proteoglycan (PG) are considered important for the T 1r parameter's relaxation mechanism in articular cartilage (8). In addition, the chemical exchanges between the hydroxyl and amino groups of collagen and the water protons may affect the T 1r parameter; a previous study demonstrated that T 1r shows approximately exponential dependencies on molecular concentration using collagen solutions (9).The T 2 parameter is a spin-spin relaxation method related to the energy ch...

Gene expression is controlled by epigenetic mechanisms such as histone acetylation and methylation, and recent studies have revealed that key developmental steps are regulated by the trimethylation of histone H3 lysine 4 (H3K4me3) and lysine 27 (H3K27me3). Using ChIP sequencing technology combined with real-time PCR, we here demonstrate that the H3K27me3 observed in the Nfatc1 gene in bone marrow-derived macrophages (BMMs) was markedly reduced in mature osteoclasts. Jumonji domain-containing 3 (Jmjd3), a H3K27 demethylase, was induced in bone marrow-derived macrophages and in the vicinity of the transcription start site (TSS) of nuclear factor-activated T cells (NFAT) c1 in response to receptor activator of nuclear factor-kB ligand (RANKL) stimulation. Gene silencing of the Jmjd3 gene by short hairpin RNA reduced demethylation of H3K27me3 at the TSS of Nfatc1 and suppressed RANKL-induced osteoclastogenesis. These results suggest that the demethylation of H3K27me3 in the Nfatc1 gene locus by Jmjd3 plays a critical role in RANKL-induced osteoclast differentiation. ß