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Macrophage Polarization and Bone Formation: A review.
The contribution of inflammation to bone loss is well documented in arthritis and other diseases with an emphasis on how inflammatory cytokines promote osteoclastogenesis. Macrophages are the major producers of cytokines in inflammation, and the factors they produce depend upon their activation state or polarization. In recent years, it has become apparent that macrophages are also capable of interacting with osteoblasts and their mesenchymal precursors. This interaction provides growth and differentiation factors from one cell that act on the other and visa versa-a concept akin to the requirement for a feeder layer to grow hemopoietic cells or the coupling that occurs between osteoblasts and osteoclasts to maintain bone homeostasis. Alternatively, activated macrophages are the most likely candidates to promote bone formation and have also been implicated in the tissue repair process in other tissues. In bone, a number of factors, including oncostatin M, have been shown to promote osteoblast formation both in vitro and in vivo. This review discusses the different cell types involved, cellular mediators, and how this can be used to direct new bone anabolic approaches.
Abrogation of collagen-induced arthritis by a peptidyl arginine deiminase inhibitor is associated with modulation of T cell-mediated immune responses.
Proteins containing citrulline, a post-translational modification of arginine, are generated by peptidyl arginine deiminases (PAD). Citrullinated proteins have pro-inflammatory effects in both innate and adaptive immune responses. Here, we examine the therapeutic effects in collagen-induced arthritis of the second generation PAD inhibitor, BB-Cl-amidine. Treatment after disease onset resulted in the reversal of clinical and histological changes of arthritis, associated with a marked reduction in citrullinated proteins in lymph nodes. There was little overall change in antibodies to collagen or antibodies to citrullinated peptides, but a shift from pro-inflammatory Th1 and Th17-type responses to pro-resolution Th2-type responses was demonstrated by serum cytokines and antibody subtypes. In lymph node cells from the arthritic mice treated with BB-Cl-amidine, there was a decrease in total cell numbers but an increase in the proportion of Th2 cells. BB-Cl-amidine had a pro-apoptotic effect on all Th subsets in vitro with Th17 cells appearing to be the most sensitive. We suggest that these immunoregulatory effects of PAD inhibition in CIA are complex, but primarily mediated by transcriptional regulation. We suggest that targeting PADs is a promising strategy for the treatment of chronic inflammatory disease.
Strain dependent differences in glucocorticoid-induced bone loss between C57BL/6J and CD-1 mice.
We have investigated the effect of long-term glucocorticoid (GC) administration on bone turnover in two frequently used mouse strains; C57BL/6J and CD1, in order to assess the influence of their genetic background on GC-induced osteoporosis (GIO). GIO was induced in 12 weeks old female C57BL/6J and CD1 mice by subcutaneous insertion of long-term release prednisolone or placebo pellets. Biomechanical properties as assessed by three point bent testing revealed that femoral elasticity and strength significantly decreased in CD1 mice receiving GC, whereas C57BL/6J mice showed no differences between placebo and prednisolone treatment. Bone turnover assessed by microcomputer tomography revealed that contrary to C57BL/6J mice, prednisolone treated CD1 mice developed osteoporosis. In vitro experiments have underlined that, at a cellular level, C57BL/6J mice osteoclasts and osteoblasts were less responsive to GC treatment and tolerated higher doses than CD1 cells. Whilst administration of long-term release prednisolone pellets provided a robust GIO animal model in 12 weeks old CD1 mice, age matched C57BL/6J mice were not susceptible to the bone changes associated with GIO. This study indicates that for the induction of experimental GIO, the mouse strain choice together with other factors such as age should be carefully evaluated.
Increase in circulating Th17 cells during anti-TNF therapy is associated with ultrasonographic improvement of synovitis in rheumatoid arthritis.
BACKGROUND: Anti-TNF agents have revolutionised rheumatoid arthritis (RA) treatment; however, a third of patients fail to achieve therapeutic responses. Unexpectedly, studies in murine and human arthritis have indicated that anti-TNF treatment can increase circulating T helper 17 (Th17) cells, but the relationship to treatment response is unclear. To identify immune correlates of anti-TNF treatment response, we conducted a longitudinal study using clinical, ultrasound and T cell assessments. METHODS: Patients with RA (n = 25) were studied at protocol visits during the initial 12 weeks of anti-TNF treatment. Improvement in the disease activity score of 28 joints (DAS28) >1.2 defined treatment responders (n = 16) and non-responders (n = 9). Changes in synovial thickening and vascularity of 10 metacarpophalangeal joints were quantitatively assessed by grey scale and power Doppler ultrasound. The frequency of circulating Th17 cells was determined by IL17 enzyme-linked immunospot assay (Elispot) and flow cytometry (fluorescence-activated cell sorting (FACS)). RESULTS: The frequency of circulating IL17-producing cells increased significantly 12 weeks after anti-TNF initiation (Elispot median (range) specific spot forming cells (spSFC)/106 360 (280-645) vs 632 (367 - 1167), p = 0.003). The increase in CD4 + IL17+ cells at 12 weeks was confirmed by FACS (median (range) %, 0.7 (0.5-0.9) vs 1.05 (0.6-1.3); p = 0.01). The increase in circulating Th17 cells inversely correlated with reduction in synovial vascularity (r = -0.68, p = 0.007) and thickening (r = -0.39; p = 0.04). Higher frequencies of circulating Th17 cells at baseline were associated with poorer anti-TNF treatment response defined by ultrasonographic measures. CONCLUSIONS: These results demonstrate a link between changes in circulating Th17 cells with resolution of ultrasonographic features of synovial inflammation and vascularity during anti-TNF treatment. The findings may reflect redistribution of Th17 cells from inflamed joints or TNF-driven regulation of Th17 cell production. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01060098 . Registered 29 January 2010.
Context-specific regulation of surface and soluble IL7R expression by an autoimmune risk allele.
IL-7 is a key factor in T cell immunity and common variants at IL7R, encoding its receptor, are associated with autoimmune disease susceptibility. IL7R mRNA is induced in stimulated monocytes, yet a function for IL7R in monocyte biology remains unexplored. Here we characterize genetic regulation of IL7R at the protein level in healthy individuals, and find that monocyte surface and soluble IL7R (sIL7R) are markedly induced by lipopolysaccharide. In monocytes, both surface IL7R and sIL7R expression strongly associate with allelic carriage of rs6897932, a disease-associated IL7R polymorphism. Monocytes produce more sIL7R than CD4 + T cells, and the amount is additionally correlated with the expression of DDX39A, encoding a splicing factor. Synovial fluid-derived monocytes from patients with spondyloarthritis are enriched for IL7R+ cells with a unique transcriptional profile that overlaps with IL-7-induced gene sets. Our data thus suggest a previously unappreciated function for monocytes in IL-7 biology and IL7R-associated diseases.
Signal Integration in Immune Regulatory Networks
Regulatory T-cells are crucial for maintaining immune homeostasis and preventing the development of autoimmune and inflammatory diseases. However, they are also responsible for hindering the immune response against malignancies. Despite years of research, many questions remain unanswered regarding the function of human T-regs. Specifically, what are the biophysical factors that make certain responses susceptible to regulation while others circumvent them. To address those questions, we have established a 3D collagen-based culture that supports the migration of human immune cells. We confer specificity to T-cells using mRNA electroporation to express specific T-cell receptors. Next, using a library of altered peptide ligands with different affinities, we perform time-lapse microscopy and functional analysis in the 3D system. Using this system, we are currently investigating the role of antigen stimulation in T-reg suppressive function. Furthermore, we aim at delineating which inhibitory mechanisms are dominant under different homeostatic and inflammatory conditions where we hypothesise that the dynamics of the T-cell/DC interactions and the strength of the integrated signals will require different suppressive capacity of T-regs. We aim to use our data to construct a mathematical model to describe the mechanism of action of T-regs.
Telomerecat: A ploidy-agnostic method for estimating telomere length from whole genome sequencing data.
Telomere length is a risk factor in disease and the dynamics of telomere length are crucial to our understanding of cell replication and vitality. The proliferation of whole genome sequencing represents an unprecedented opportunity to glean new insights into telomere biology on a previously unimaginable scale. To this end, a number of approaches for estimating telomere length from whole-genome sequencing data have been proposed. Here we present Telomerecat, a novel approach to the estimation of telomere length. Previous methods have been dependent on the number of telomeres present in a cell being known, which may be problematic when analysing aneuploid cancer data and non-human samples. Telomerecat is designed to be agnostic to the number of telomeres present, making it suited for the purpose of estimating telomere length in cancer studies. Telomerecat also accounts for interstitial telomeric reads and presents a novel approach to dealing with sequencing errors. We show that Telomerecat performs well at telomere length estimation when compared to leading experimental and computational methods. Furthermore, we show that it detects expected patterns in longitudinal data, repeated measurements, and cross-species comparisons. We also apply the method to a cancer cell data, uncovering an interesting relationship with the underlying telomerase genotype.
Combination therapy with DMARDs and biological agents in collagen- induced arthritis
There is increasing interest in the use of combination therapy for rheumatoid arthritis and in the possibility of combining the conventional drug approach with newer biological therapies. Animal models of arthritis provide important tools for evaluating novel forms of therapy and for eludicating mechanisms of drug action. In this paper, we review the results of our own research into combination therapy in collagen-induced arthritis using biological therapies such as antitumor necrosis factor α, anti-CD4, and anti-interleukin 12 monoclonal antibodies, and small molecular weight compounds such as cyclosporin and the phosphodiesterase IV (PDE IV) inhibitor rolipram.
TNF-α in rheumatoid arthritis and prospects of anti-TNF therapy
Our work has shown that TNFα is produced by cultured mononuclear cells from rheumatoid arthritis joints and appears to regulate the production of IL-1. Immunohistochemical examination has shown the presence of TNFα in the synovium, e.g. in the lining layer, some endothelial cells and most importantly, in the cells in the cartilage pannus junction. TNF receptors (both p55 and p75) have a similar distribution, thereby suggesting that TNF has the potential for autocrine and paracrine activity in the joint. The concept that TNFα is pathogenic in inflammatory arthritis has been validated by showing that neutralizing monoclonal anti-TNF antibodies significantly attenuate collagen-induced arthritis in mice. In preliminary trials in rheumatoid patients anti-TNF appears to have an impressive effect on indices of disease activity including C-reactive production and serum amyloid-A production. TNFα appears to be a relevant therapeutic target in rheumatoid disease.
α-synuclein locus duplication as a cause of familial Parkinson's disease
Genomic triplication of the α-synuclein gene (SNCA) has been reported to cause hereditary early-onset parkinsonism with dementia. These findings prompted us to screen for multiplication of the SNCA locus in nine families in whom parkinsonism segregates as an autosomal dominant trait. One kindred was identified with SNCA duplication by semiquantitative PCR and confirmed by fluorescent in-situ hybridisation analysis in peripheral leucocytes. By contrast with SNCA triplication families, the clinical phenotype of SNCA duplication closely resembles idiopathic Parkinson's disease, which has a late age-of-onset, progresses slowly, and in which neither cognitive decline nor dementia are prominent. These findings suggest a direct relation between SNCA gene dosage and disease progression.