BMC - Arthritis Research and Therapy

IntroductionThe biological basis for the avascular state of the intervertebral disc is not well understood. Previous work has suggested that the presence of thrombospondin-1 (TSP-1), a matricellular protein, in the outer annulus reflects a role for this protein in conferring an avascular status to the disc. In the present study we have examined TSP-2, a matricellular protein with recognized anti-angiogenic activity in vivo and in vitro. Methods: We examined both the location and expression of TSP-2 in the human disc, and its location in the disc and bordering soft tissues of five month-old normal wild type (WT) mice, and mice with a targeted disruption of the TSP-2 gene. Immunohistochemistry and quantitative histology were utilized in this study. Results: TSP-2 was found to be present in some, but not all, annulus cells of the human and mouse annulus. Although there was no difference in the number of disc cells in the annulus of TSP-2-null compared to that of WT animals, polarized light microscopy revealed a more irregular lamellar collagen structure in null compared to WT discs. Additionally, vascular beds at the margins of discs of TSP-2-null mice were substantially more irregular than those of WT animals. Counts of platelet endothelial cell adhesion molecule-1 (PECAM-1) -positive blood vessels in the tissue margin bordering the ventral annulus showed a significantly larger vascular bed in the tissue bordering the disc of TSP-2-null mice compared to that of WT mice (p = 0.0002). However, there was no vascular ingrowth into discs of the TSP-2-null mice. Conclusions: These data confirm a role for TSP-2 in the morphology of the disc and suggest the presence of other inhibitors of angiogenesis in the disc. We have shown that although an increase in vasculature was present in the TSP-2-null tissue in the margin of the disc, vascular ingrowth into the body of the disc did not occur. Our results point to the need for future research to understand the transition from the well-vascularized status of the fetal and young discs to the avascular state of the adult human or small mammalian disc.

IntroductionHealth care utilization ("claims") databases contain information for millions of patients and provide important sources of information for a variety of study types. However, they typically do not contain information about disease severity. The goal of our study was to develop a health care claims index for rheumatoid arthritis (RA) severity using a previously developed medical records-based index for RA severity (RARBIS). Methods: The study population consisted of 120 patients from the Veteran's Administration (VA) Health System. We previously demonstrated the construct validity of the RARBIS and established its convergent validity with the Disease Activity Score (DAS-28). Potential claims-based indicators were entered into a linear regression model as independent variables and RARBIS as the dependent variable. The claims-based index for RA severity (CIRAS) was created using the coefficients from models with the highest R2 values selected by automated modeling procedures. To compare our claims-based index with our medical records-based index, we examined the correlation between the CIRAS and RARBIS using Spearman nonparametric tests. Results: The forward selection models yielded the highest model R2 for both the RARBIS with medications (R2=0.31) and the RARBIS without medications (R2=0.26). Components of the CIRAS included tests for inflammatory markers, number of chemistry panels and platelet counts ordered, rheumatoid factor, rehabilitation and rheumatology visits, and Felty's syndrome diagnosis. The CIRAS demonstrated moderate correlations with the RARBIS with medication and the RARBIS without medication subscales. Conclusions: We developed a health care claims-based index of RA severity (CIRAS) that showed moderate correlations with a previously validated records based index of severity. The CIRAS may serve as a potentially important tool in adjusting for RA severity in pharmacoepidemiology studies of RA treatment and complications using health care utilization data.

NF-kB is an inducible transcription factor controlled by two principal signaling cascades each activated by a set of signal ligands, the classical/canonical NF-kB activation pathway and the alternative/non-canonical pathway. The former pathway proceeds via phosphorylation and degradation of the IkB inhibitor protein and leads most commonly to activation of the heterodimer RelA/NF-kB1(p50) (Figs.1,2). The latter pathway proceeds via phosphorylation and proteolytic processing of NF-kB2(p100) and leads to activation, most commonly, of the heterodimer, RelB/NF-kB2(p52) (Figs. 1,3). Both pathways play critical roles at multiple levels of the immune system in health and in disease, including the autoimmune inflammatory response. These roles include cell-cycle progression, cell survival, adhesion and inhibition of apoptosis. NF-kB is constitutively activated in many autoimmune diseases including diabetes type 1, systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). In this review we survey recent developments in the involvement of the classical and alternative pathways of NF-kB activation in autoimmunity, focusing particularly on RA. We discuss the involvement of NF-kB in self-reactive T and B lymphocyte development, survival and proliferation, also the maintenance of chronic inflammation due to cytokines such as TNF-alpha and IL-1. We emphasize the roles of IL-17 and Th17 cells in the inflammatory process and in the activation, maturation and proliferation of RA fibroblast-like synovial cells and differentiation and activation of bone resorbing activity of osteoclasts. The prospects of therapeutic intervention to block activation of the NF-kB signaling pathways in RA are also discussed.

IntroductionThere is increasing evidence that autoantibodies and immune complexes (ICs) contribute to synovitis in rheumatoid arthritis (RA), yet the autoantigens incorporated in ICs in RA remain incompletely characterized. Methods: We utilized C1q to capture ICs from plasma derived from human RA and control patients, followed by detection with antibodies specific for: (i) immunoglobulin to detect ICs, and (ii) fibrinogen to detect fibrinogen-containing ICs. RA and control plasma were separated by liquid chromatography, and fractions characterized by ELISA, immunoblotting and mass spectrometry. Immunohistochemical staining was performed on rheumatoid synovial tissue. Results: C1q-immunoassays demonstrated increased levels of IgG (P = 0.01) and IgM (P = 0.0002) ICs in plasma derived from RA patients possessing anti-cyclic citrullinated peptide autoantibodies (CCP+) as compared to healthy controls. About one-half of the CCP+ RA possessed circulating ICs containing fibrinogen (P = 0.0004). Fractionation of whole RA plasma revealed citrullinated fibrinogen in the high molecular weight fractions that contained immune complexes. Positive correlations were observed between fibrinogen containing immune complex and anti-citrullinated fibrinogen autoantibodies, anti-CCP antibody, rheumatoid factor and certain clinical characteristics. Immunohistochemical staining demonstrated co-localization of fibrinogen, immunoglobulin and complement component C3 in RA pannus tissue. Mass spectrometry analysis of immune complexes immunoprecipitated from RA pannus tissue lysates demonstrated the presence of citrullinated fibrinogen. Conclusions: Circulating ICs containing citrullinated fibrinogen are present in one-half of CCP+ RA patients, and these immune complexes co-localize with C3 in the rheumatoid synovium suggesting that they contribute to synovitis in a subset of RA patients.

IntroductionThis study was conducted to quantify the number of TH-17 cells present in rheumatoid arthritis (RA) synovial fluid (SF) and the to determine the level of IL-17 cytokine in RA, osteoarthritis (OA) and normal synovial tissue, as well as to examine SF macrophages for the presence of IL-23, IL-27 and interferon (IFN)-g. Methods: Peripheral blood (PB) mononuclear cells from normal and RA donors and mononuclear cells from RA SF were examined either without stimulation, or after pretreatment with IL-23 followed by stimulation with PMA plus ionomycin (P/I). The abundance of TH-17 cells in RA SF was determined by flow cytometry. IL-17 levels were quantified in synovial tissue from RA, OA and normal individuals by ELISA. IL-23 was identified in SFs by ELISA. RA SF and control in vitro differentiated macrophages were either untreated or treated with the Toll like receptor (TLR)2 ligand peptidoglycan, and then IL-23, IL-27 and IFN-g mRNA levels were quantified by real-time RT-PCR. Results: Treatment with P/I alone or combined with IL-23 significantly increased the number of TH-17 cells in normal and RA PB and in RA SF. With or without P/I plus IL-23, the percentage of TH-17 cells was higher in RA SF compared to normal and RA PB. IL-17 levels were comparable in OA and normal synovial tissues, and these values were significantly increased in RA synovial tissue. Although IL-17 was readily detected in RA SFs, IL-23 was rarely identified in RA SF. However, IL-23 mRNA was significantly increased in RA SF macrophages compared to control macrophages, with or without TLR2 ligation. IL-27 mRNA was also significantly higher in RA SF compared to control macrophages, but there was no difference in IL-27 levels between RA and control macrophages following TLR2 ligation. IFN-g mRNA was also detectable in RA SF macrophages but not control macrophages and the increase of IFN-g mRNA following TLR2 ligation was greater in RA SF macrophages compared to control macrophages. Conclusions: These observations support a role for TH-17 cells in RA. Our observations do not strongly support a role or IL-23 in the generation to TH-17 cells in the RA joint, however, they suggest that strategies which enhance IL-27 or IFN-g might modulate the presence of TH-17 cells in RA.

IntroductionThe in vitro invasive properties of rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS) have been shown to correlate with disease severity and radiographic damage. We have recently determined that FLS obtained from pristane-induced arthritis (PIA)-susceptible DA rats are also highly invasive in the same in vitro assay through Matrigel. The transfer of alleles derived from the arthritis-resistant F344 strain at the arthritis severity locus Cia5d (RNO10), as in DA.F344(Cia5d) congenics, was enough to significantly and specifically reduce the invasive properties FLS. This genetically controlled difference in FLS invasion involves increased production of soluble membrane-type 1 matrix metalloproteinase (MT1-MMP) by DA, and is dependent on increased activation of matrix metalloproteinase-2 (MMP-2). In the present study we aimed at characterizing the pattern of gene expression that correlates with differences in invasion in order to identify pathways regulated by the Cia5d locus. Methods: Synovial tissues were collected from DA and DA.F344(Cia5d) rats 21 days after the induction of PIA. Tissues were digested and FLS isolated. After a minimum of four passages FLS were plated on Matrigel-covered dishes at similar densities for 24h, followed by RNA extraction. Illumina RatRef-12 expression BeadChip arrays were used. Expression data were normalized, followed by t-test, logistic regression and cluster analysis. Real-time quantitative polymerase chain reaction (QPCR) was used for validation of the microarray data. Results: 7,665 genes out of the 22,523 RefSeq gene probes present in the array were expressed by the FLS. The expression of 66 genes was significantly different between the DA and DA.F344(Cia5d) FLS (P

IntroductionA multitude of interferon (IFN)-inducible genes (IFIGs) was found highly expressed in the peripheral blood mononuclear cells (PBMC) of most patients with systemic lupus erythematosus (SLE) via oligonucleotide microarray. Among these IFIGs, interferon-induced protein with tetratricopeptide repeats 4 (IFIT4) is a novel gene with function unknown. Methods: In this study, we studied the role of IFIT4 in monocyte differentiation and the correlation between IFIT4 expression and the clinical manifestation of SLE using plasmid transfection, flow cytometry, mixed leukocyte responses (MLRs), ELISA, quantitative RT-PCR and Western blotting. Results: We found that both IFIT4 mRNA and protein expression levels were significantly higher in PBMCs and monocytes from SLE patients than those from healthy controls. IFIT4 expression was positively correlated with ANA, anti-dsDNA, and anti-Sm auto-immune antibodies in SLE. SLE patients with higher expression of IFIT4 had a higher prevalence of leucopenia, thrombocytopenia, and C3/C4 decrease. IFIT4 protein was localized exclusively in the cytoplasm, and significantly up-regulated by IFN-alpha in normal PBMCs. To determine the role of IFIT4 in monocyte differentiation, the monocytic cell line THP-1 was transfected with pEGFP-IFIT4 expression plasmid and stimulated with GM-CSF/IL-4 to generate IFIT4-primed DC-like cells (DCLCs). IFIT4-primed DCLCs acquired morphological characteristics of DCs more quickly with a greater resemblance to DCs and had higher expression of CD40, CD86, CD80, HLA-DR, and CD83, along with lower expression of CD14; increased IL-12 secretion; and an increased ability to stimulate T cell proliferation than DCLCs primed with a pEGFP-C1 control plasmid trasfection. Besides, IFIT4-primed DCLCs enhanced the IFN-gamma secretion (about 2.4 fold) by T cells compared with controls. Conclusions: Our findings suggested that IFIT4 might play a role in promoting monocyte differentiation into DCLCs and directing DCLCs to modulate Th1 cells differentiation, all of which might contribute to the autoimmunity and pathogenesis of SLE.

IntroductionFibroblast growth factor-8 (FGF8) is isolated as an androgen-induced growth factor and recently has shown to contribute to limb morphogenesis. The aim of this study was to clarify the role of FGF8 in animal models of osteoarthritis (OA). Methods: The expression of FGF8 in the partial meniscectomy model of OA in the rabbit knee was examined by immunohistochemistry. The effect of intraperitoneal administration of anti-FGF8 antibody was tested in a model of OA that employed injection of monoiodoacetic acid (MIA) or FGF8 into the knee joint of rats. Effect of FGF8 was also tested using cultured chondrocytes. Rabbit articular chondrocytes were treated with FGF8 for 48 hours, and the production of matrix metalloproteinase and the degradation of sulfated glycosaminoglycan in the extracellular matrix (ECM) were measured. Results: The expression of FGF8 in hyperplastic synovial cells and fibroblasts was induced in the meniscectomized OA model, whereas little or no expression was detected in normal synovium. Injection of FGF8 into rat knee joints induced the degradation of ECM, which was suppressed by anti-FGF8 antibody. In the MIA-induced arthritis model, anti-FGF8 antibody reduced ECM release into the synovial cavity. In cultured chondrocytes, FGF8 induced the release of matrix metalloproteinase 3 and prostaglandin E2 and caused degradation of ECM. The combination of FGF8 and interleukin-1alpha accelerated the degradation of ECM. Anti-FGF8 antibody suppressed the effects of FGF8 on the cells. Conclusions: FGF8 is produced by injured synovium and it enhances the production of protease and PGE2 from inflamed synoviocytes. Degradation of ECM is enhanced by FGF8. Therefore, FGF8 may participate in the degradation of cartilage and exacerbation of osteoarthritis.

Bone morphogenetic proteins (BMPs) are expressed during osteogenesis and their action is regulated by corresponding BMP inhibitors. Chordin (a well recognized BMP inhibitor) and BMP-2 are expressed during osteogenic differentiation of human mesenchymal stem cells. Chordin inhibition induces human mesenchymal stem cell differentiation and reduces their proliferation by increasing BMP-2 bioavailability. The potential of suppressing BMP inhibitors is emerging as a biological therapeutic target in bone tissue engineering, because it results in an unopposed synergy between the various growth factors that are involved in osteogenesis, within their physiological milieu.

IntroductionAdult mesenchymal stem cell therapy has potential application in the biologic treatment of disc degeneration. Our objectives were: 1) To direct adipose-derived mesenchymal stem cells (AD-MSC) from the sand rat to produce a proteoglycan and collagen type I extracellular matrix (ECM) rich in known ECM components of the annulus fibrosis of disc and 2) To stimulate proteoglycan production by co-culture of human annulus cells with AD-MSC. Methods: AD-MSC were isolated and characterized by adherence to plastic, appropriate expression of CD markers, and differentiation to osteoblasts and chondrocytes in vitro. AD-MSC were grown in three dimensional (3D) culture and treated with or without transforming growth factor beta (TGFbeta) to direct them to produce annulus-like ECM as determined by proteoglycan content and collagen expression. AD-MSC were cocultured with human annulus cells and grown in 3D culture. Results: AD-MSC produced a proteoglycan and collagen type I rich matrix following treatment with TGFbeta in 3D culture as confirmed by a 48% increase in proteoglycan content as assayed by 1,9-dimethylmethylene blue (DMB), and by immunohistochemical identification of extracellular matrix components. Coculture of human annulus and sand rat AD-MSC in 3D resulted in a 20% increase in proteoglycan production compared to the predicted value of the sum of the individual cultures. Conclusions: Results support the hypothesis that AD-MSC have potential in cell-based therapy for disc degeneration.

No abstract available

Researchers studying fibromyalgia (FM) strive to identify objective, measurable biomarkers that may identify susceptible individuals, facilitate diagnosis, or that parallel activity of the disease. Candidate objective measures range from sophisticated functional neuroimaging, to office-ready measures of pressure pain threshold. A systematic literature review was completed to assess highly investigated, objective measures used in FM studies. To date, only experimental pain testing has been shown to coincide with improvements in clinical status in a longitudinal study. Concerted efforts to systematically evaluate additional objective measures in research trials will be vital for ongoing progress in outcome research and translation into clinical practice.

IntroductionCollagen-induced arthritis (CIA) in mice is a commonly used experimental model for rheumatoid arthritis (RA). We have previously identified a significant quantitative trait locus denoted Cia40 on chromosome 11 that affects CIA in older female mice. This locus co-localizes with another locus, denoted Pregq2, known to affect reproductive success. The present study was performed to evaluate the role of the Cia40 locus in congenic B10.Q mice, and identify possible polymorphic candidate genes, which may also be relevant in the context of RA. Methods: Congenic B10.Q mice carrying a NFR/N fragment surrounding the Cia40/Pregq2 loci were created by 10 generations of backcrossing (N10). The congenic mice were investigated in the CIA model, and the incidence and severity of arthritis were recorded as well as the serum levels of anti-collagen II (CII) antibodies. Results: Significant effects on onset, incidence, severity and anti-CII antibody titres were observed in female mice carrying a heterozygous congenic Cia40/Pregq2 fragment of NFR/N origin, containing one or more polymorphic genes. Congenic male mice did not show increased incidence of CIA, but males carrying a heterozygous fragment showed a significant increase in severity in comparison to wildtype B10.Q males (littermates). Conclusions: The Cia40/Pregq2 locus at chromosome 11 contains one or more polymorphic genes of NFR/N origin that significantly influence both incidence and severity of CIA in heterozygous congenic mice of the B10.Q strain. The major polymorphic candidate genes for the effects on CIA are Cd79b, Abca8a and Map2k6. The congenic fragment also contains polymorphic genes that affect reproductive behavior and reproductive success. The Sox9 gene, known to influence sex reversal, is a candidate gene for the reproductive phenotype.

IntroductionChronic and debilitating low back pain is a common condition and a huge economic burden. Many cases are attributed to age-related degeneration of the intervertebral disc (IVD), however, age-related degeneration appears to occur at an accelerated rate in some individuals. We have previously demonstrated biomarkers of cellular senescence within the human IVD and suggested a role for senescence in IVD degeneration. Senescence occurs with ageing, but can also occur prematurely in response to stress. We hypothesised that stress-induced premature senescence (SIPS) occurs within the IVD and here we have investigated the expression and production of caveolin-1, a protein that has been shown previously to be upregulated in SIPS. Methods: Caveolin-1 gene expression in human nucleus pulposus (NP) cells was assessed by conventional and quantitative real-time PCR and caveolin-1 protein expression examined within human IVDs using immunohistochemistry. Correlation between caveolin-1 and p16INK4a (biomarker of cellular senescence) gene expression was investigated using quantitative real-time PCR. Results: Caveolin-1 gene and protein expression were demonstrated within the human IVD for the first time. NP cells from degenerate discs exhibited elevated levels of caveolin-1 that did not relate to increasing chronological age. A negative correlation was observed between gene expression for caveolin-1 and donor age and no correlation was found between caveolin-1 protein expression and age. A positive correlation was identified between gene expression of caveolin-1 and p16INK4a. Conclusions: Our findings are consistent with a role for caveolin-1 in degenerative rather than age-induced changes in the NP. Its expression in IVD tissue and its association with the senescent phenotype suggests that caveolin-1 and SIPS may play a prominent role in the pathogenesis of IVD degeneration.

IntroductionApoptosis has been reported to occur in the intervertebral disc. Elsewhere in the body apoptotic cells are cleared from the system via phagocytosis by committed phagocytes such as macrophages, reducing the chance of subsequent inflammation. These cells, however, are not normally present in the disc. We investigated whether disc cells themselves can be induced to become phagocytic and so have the ability to ingest and remove apoptotic disc cells, minimising the damage to their environment. Methods: Bovine nucleus pulposus cells from caudal intervertebral discs were grown in culture and exposed to both latex particles (which are ingested by committed phagocytes) and apoptotic cells. Their response was monitored via microscopy, including both fluorescent- and video-microscopy, and compared to that seen by cell lines of monocytes/macrophages (THP-1 and J774 cells), considered to be committed phagocytes, in addition to a non-macrophage cell line L929 fibroblasts. Immunostaining for the monocyte/macrophage marker, CD68, was also carried out. Results: Disc cells were able to ingest latex beads at least as efficiently, if not more so, than phagocytic THP-1 and J774 cells. Disc cells ingested a greater number of beads per cell than the committed phagocytes in a similar time scale. In addition, disc cells were able to ingest apoptotic cells when co-cultured in monolayer with a UV-treated population of HeLa cells. Apoptotic disc cells in turn were able to stimulate phagocytosis by the committed macrophages. CD68 immunostaining was strong for THP-1 cells but negligible for disc cells, even those that had ingested beads. Conclusions: In this study we have shown that intervertebral disc cells are capable of behaving as competent phagocytes i.e. ingesting latex beads, and apoptotic cells. In terms of number of particles, they ingest more than the monocyte/macrophage cells, possibly due to their greater size. The fact that disc cells can clearly undergo phagocytosis has implications for the intervertebral disc in vivo. Here, where cell death is reported to be common, yet there is normally no easy access to a macrophage population, the endogenous disc cells may be encouraged to undergo phagocytosis, for example of neighbouring cells within cell clusters.

Sjögren's syndrome is a rheumatic disease in which the salivary and lacrimal glands are the principal targets of a pathological autoimmune reaction. Previous studies in mice indicated that delayed organogenesis and aberrant cell physiology followed by an increase in acinar cell apoptosis precede chronic focal inflammation in the salivary glands and the manifestation of impaired exocrine gland secretion. In a recent study by Wildenberg and colleagues, the authors report aberrant proteolytic activity in the salivary glands of non-obese diabetic mice and the generation of a unique organ-specific 17 kDa fragment of the chemokine and adhesion molecule fractalkine.

Introduction5-Loxin® is a novel Boswellia serrata extract enriched with 30% 3-O-acetyl-11-keto-beta-boswellic acid (AKBA), which exhibits potential anti-inflammatory properties by inhibiting the 5-lipoxygenase enzyme. A 90-day, double-blind, randomized, placebo-controlled study was conducted to evaluate the efficacy and safety of 5-Loxin® in the treatment of osteoarthritis (OA) of the knee. Methods: Seventy-five OA patients were included in the study. The patients received either 100 mg (n = 25) or 250 mg (n = 25) of 5-Loxin® daily or a placebo (n = 25) for 90 days. Each patient was evaluated for pain and physical functions by using the standard tools (visual analog scale, Lequesne's Functional Index, and Western Ontario and McMaster Universities Osteoarthritis Index) at the baseline (day 0), and at days 7, 30, 60 and 90. Additionally, the cartilage degrading enzyme matrix metalloproteinase-3 was also evaluated in synovial fluid from OA patients. Measurement of a battery of biochemical parameters in serum and haematological parameters, and urine analysis were performed to evaluate the safety of 5-Loxin® in OA patients. Results: Seventy patients completed the study. At the end of the study, both doses of 5-Loxin® conferred clinically and statistically significant improvements in pain scores and physical function scores in OA patients. Interestingly, significant improvements in pain score and functional ability were recorded in the treatment group supplemented with 250 mg 5-Loxin® as early as 7 days after the start of treatment. Corroborating the improvements in pain scores in treatment groups, we also noted significant reduction in synovial fluid matrix metalloproteinase-3. In comparison with placebo, the safety parameters were almost unchanged in the treatment groups. Conclusion: 5-Loxin® reduces pain and improves physical functioning significantly in OA patients; and it is safe for human consumption. 5-Loxin® may exert its beneficial effects by controlling inflammatory responses through reducing proinflammatory modulators, and it may improve joint health by reducing the enzymatic degradation of cartilage in OA patients.Trail Registration(Clinical trial registration number: ISRCTN05212803.)

IntroductionCurrent cell therapy for cartilage regeneration requires invasive procedures, periosteal coverage and scaffold use. We have developed a novel transplantation method with synovial mesenchymal stem cells (MSCs) to adhere to the cartilage defect. Methods: For ex vivo analysis in rabbits, the cartilage defect was faced upward, filled with synovial MSC suspension, and held stationary for 2.5 - 15 minutes. The number of attached cells was examined. For in vivo analysis in rabbits, autologous synovial MSC suspension was placed on the cartilage defect, and the position was maintained for 10 minutes to adhere the cells to the defect. For the control, either the same cell suspension was injected intra-articularly, or the defects were left empty. Three groups were compared macroscopically and histologically. For ex vivo analysis in humans, in addition to the similar experiment in rabbits, the expression and effects of neutralizing antibodies for adhesion molecules were examined. Results: Ex vivo analysis in rabbits demonstrated that the number of attached cells increased in a time-dependent manner, and more than 60% of cells attached within ten minutes. The in vivo study showed that a large number of transplanted synovial MSCs attached to the defect at 1 day, and the cartilage defect improved at 24 weeks. The histological score was consistently better than the scores of the other two control groups at 4, 12, and 24 weeks. Ex vivo analysis in humans provided similar results to those in rabbits. ICAM-1 positive cells increased between 1 and 10 minutes, and neutralizing antibodies for ICAM-1, VCAM-1 and ALCAM inhibited the attachment. Conclusions: Placing MSC suspension on the cartilage defect for 10 minutes resulted in adherence of more than 60% of synovial MSCs to the defect, and promoted cartilage regeneration. This adherent method makes it possible to adhere MSCs with low invasion, without periosteal coverage, and without a scaffold.

IntroductionMesenchymal progenitor cells (MPCs) are multipotent progenitor cells in adult tissues, e.g., bone marrow (BM). Current challenges of clinical application of BM-derived MSCs include donor-site morbidity and pain, and low cell yields associated with age-related decrease in cell number and differentiation potential, underscoring the need to identify alternative sources of MSCs. Recently, MSC sources have diversified; examples include adipose, placenta, umbilicus, trabecular bone, cartilage, and synovial tissue. In the present work, we report the presence of MSCs in human tonsillar tissue. Methods: We performed comparative and quantitative analyses of BM-MPCs with a subpopulation of adherent cells isolated from this lymphoid tissue, termed tonsil-derived MPCs (T-MPCs). The expression of surface markers was assessed by fluorescent-activated cell sorting analysis. Differentiation potential of T-MPCs was analyzed histochemically and by quantitative RT-PCR for the expression of lineage related marker genes. The immunosuppressive properties of MPCs were determined in vitro in mixed lymphocyte reactions. Results: Surface epitope analysis revealed that T-MPCs were negative for CD14, CD34 and CD45 expression and positive for CD29, CD44, CD90 and CD105 expression, a characteristic phenotype of BM-MPCs. Similar to BM-MPCs, T-MPCs could be induced to undergo adipogenic differentiation and, to a lesser extent, osteogenic and chondrogenic differentiation. T-MPCs did not express class II major histocompatibility (MHC) antigens, and in a similar but less pronounced manner compared to BM-MPCs, T-MPCs were immunosuppressive, inhibiting the proliferation of T cells stimulated by allogeneic T cells or by non-specific mitogenic stimuli, via an indoleamine 2,3-dioxygenase-dependent mechanism. Conclusions: Human palatine tonsil-derived MPCs represent a new source of progenitor cells, potentially applicable for cell-based therapies.

Self-reactive T cells with low signalling capacity through the T-cell receptor were recently observed in the SKG mouse model of rheumatoid arthritis (RA) and have been linked to a spontaneous mutation in the ZAP-70 signal transduction molecule. Here we hypothesize that similar mechanisms also drive RA, associated with an abnormal innate and adaptive immune response driven by nuclear factor-?B activation and tumour necrosis factor secretion. Similar to the essential role played by pathogens in SKG mice, we propose that HLA-associated immunity to chronic viral infection is a key factor in the immune dysregulation and joint inflammation that characterize RA.