PPARß/δ directs the therapeutic potential of mesenchymal stem cells in arthritis.

OBJECTIVES: To define how peroxisome proliferator-activated receptor (PPAR) ß/δ expression level in mesenchymal stem cells (MSCs) could predict and direct both their immunosuppressive and therapeutic properties. PPARß/δ interacts with factors such as nuclear factor-kappa B (NF-κB) and regulates the expression of molecules including vascular cell adhesion molecule (VCAM)-1 and intercellular adhesion molecule (ICAM)-1. Since these molecules are critical for MSC function, we investigated the role of PPARß/δ on MSC immunosuppressive properties. METHODS: We either treated human MSCs (hMSCs) with the irreversible PPARß/δ antagonist (GSK3787) or derived MSCs from mice deficient for PPARß/δ (PPARß/δ-/- MSCs). We used the collagen-induced arthritis (CIA) as model of immune-mediated disorder and the MSC-immune cell coculture assays. RESULTS: Modulation of PPARß/δ expression in hMSCs either using GSK3787 or hMSCs from different origin reveals that MSC immunosuppressive potential is inversely correlated with Ppard expression. This was consistent with the higher capacity of PPARß/δ-/- MSCs to inhibit both the proliferation of T lymphocytes, in vitro, and arthritic development and progression in CIA compared with PPARß/δ+/+ MSCs. When primed with proinflammatory cytokines to exhibit an immunoregulatory phenotype, PPARß/δ-/- MSCs expressed a higher level of mediators of MSC immunosuppression including VCAM-1, ICAM-1 and nitric oxide (NO) than PPARß/δ+/+ MSCs. The enhanced NO2 production by PPARß/δ-/- MSCs was due to the increased retention of NF-κB p65 subunit on the κB elements of the inducible nitric oxide synthase promoter resulting from PPARß/δ silencing. CONCLUSIONS: Our study is the first to show that the inhibition or knockdown of PPARß/δ in MSCs primes their immunoregulatory functions. Thus, the regulation of PPARß/δ expression provides a new strategy to generate therapeutic MSCs with a stable regulatory phenotype.

Fc-gamma receptors are not involved in cartilage damage during experimental osteoarthritis.

OBJECTIVE: Fc-gamma receptors (FcγRs) have been shown to play a crucial role in cartilage degradation during experimental arthritis. Although most of their effect on cartilage degradation has been attributed to their potential to promote inflammation in the presence of immunoglobulins, activating FcγRs promote cartilage degeneration in antigen-induced arthritis (AIA) independently of the level of inflammation. This prompted us to investigate, whether FcγRs may also play a role in osteoarthritis (OA)-related cartilage degradation. METHODS: FcγR expression was measured by RT-PCR and FACS in murine cartilage tissue and chondrocytes. Experimental OA was induced by destabilisation of the medial meniscus (DMM) in WT mice and animals lacking either activating (Fc receptor γ-chain-deficient) or inhibitory (FcγRIIB-deficient) FcγRs. Cartilage damage was investigated histologically 8 weeks post-surgery by assessing proteoglycan loss and structural damage according to OARSI recommendations. Osteophyte size was measured to investigate alterations in bone turnover. RESULTS: Expression analyses revealed significant levels for all four types of murine FcγRs in mouse chondrocytes and cartilage tissue from newborn and 8-week-old mice. Surprisingly, yet, ablation of either activating or inhibitory FcγRs did not affect cartilage damage or bone turnover during DMM-induced OA in mice. CONCLUSION: While FcγRs appear to have a crucial role in cartilage degradation during inflammatory arthritis our data indicate that FcγRs do not influence cartilage destruction in experimental OA. This indicates that a certain threshold of inflammation is a prerequisite for FcγR-induced cartilage destruction in arthritis.

Successful Generation of CD19 Chimeric Antigen Receptor T Cells from Patients with Advanced Systemic Lupus Erythematosus.

Although it has been shown that the production of functional chimeric antigen receptor T cells is feasible in patients with B-cell malignancies, it is currently unclear whether sufficient amounts of functional autologous CAR T cells can be generated from patients with autoimmune diseases. Intrinsic T-cell abnormalities and T-cell-targeted immune suppression in patients with autoimmunity may hamper the retrieval of sufficient T cells and their transduction and expansion into CAR T cells. Patients with active systemic lupus erythematosus (SLE) underwent leukapheresis after tapering glucocorticoids and stopping T-cell-suppressive drugs. This material was used as source for manufacturing anti-CD19 CAR T-cell products (CAR) in clinical scale. Cells were transduced with a lentiviral anti-CD19 CAR vector and expanded under good manufacturing practice (GMP) conditions using a closed, semi-automatic system. Functionality of these CAR T cells derived from autoimmune patient cells was tested in vitro. Six SLE patients were analyzed. Leukapheresis could be successfully performed in all patients yielding sufficient T-cell numbers for clinical scale CAR T-cell production. In addition, CAR T cells showed high expansion rates and viability, leading to CAR T cells in sufficient doses and quality for clinical use. CAR T cells from all patients showed specific cytotoxicity against CD19+ cell lines in vitro. GMP grade generation of CD19 CAR T-cell products suitable for clinical use is feasible in patients with autoimmune disease.

Blockade of Dickkopf (DKK)-1 induces fusion of sacroiliac joints.

OBJECTIVE: To study whether Dickkopf (DKK)-1, an inhibitor of wingless (Wnt) signalling, is involved in the fusion of sacroiliac joints. METHODS: Mice transgenic for tumour necrosis factor (TNFtg mice), which develop bilateral sacroiliitis, were treated with vehicle, anti-TNF antibody or anti-DKK1 antibody. Sacroiliac joints were analysed for histological signs of inflammation, bone erosion, osteoclast formation and ankylosis. Moreover, expression of collagen type X, beta-catenin and DKK-1 was assessed by immunohistochemistry. RESULTS: There were no signs of spontaneous ankylosis of the sacroiliac joints in TNFtg mice. TNF blockade effectively reduced inflammation, bone erosion and osteoclast numbers in the sacroiliac joints, but did not lead to ankylosis. Blockade of DKK1 had no effect on inflammatory signs of sacroiliitis, but significantly reduced bone erosions and osteoclast counts. Moreover, DKK1 blockade promoted expression of collagen type X, the formation of hypertrophic chondrocytes and ankylosis of sacroiliac joints. CONCLUSION: DKK1 influences inflammatory remodelling of sacroiliac joints by prevention of joint ankylosis. This may indicate an important role of the Wnt signalling pathway in the structural bone changes of axial joint disease. Although this model does not reflect the entire spectrum of ankylosing spondylitis in humans, it helps to explain the pathophysiological processes of sacroiliac joint ankylosis, which is a hallmark of the spondyloarthritides.

PPARß/δ-dependent MSC metabolism determines their immunoregulatory properties.

Mesenchymal stem cell (MSC)-based therapy is being increasingly considered a powerful opportunity for several disorders based on MSC immunoregulatory properties. Nonetheless, MSC are versatile and plastic cells that require an efficient control of their features and functions for their optimal use in clinic. Recently, we have shown that PPARß/δ is pivotal for MSC immunoregulatory and therapeutic functions. However, the role of PPARß/δ on MSC metabolic activity and the relevance of PPARß/δ metabolic control on MSC immunosuppressive properties have never been addressed. Here, we demonstrate that PPARß/δ deficiency forces MSC metabolic adaptation increasing their glycolytic activity required for their immunoregulatory functions on Th1 and Th17 cells. Additionally, we show that the inhibition of the mitochondrial production of ATP in MSC expressing PPARß/δ, promotes their metabolic switch towards aerobic glycolysis to stably enhance their immunosuppressive capacities significantly. Altogether, these data demonstrate that PPARß/δ governs the immunoregulatory potential of MSC by dictating their metabolic reprogramming and pave the way for enhancing MSC immunoregulatory properties and counteracting their versatility.

Selective p38MAPK isoform expression and activation in antineutrophil cytoplasmatic antibody-associated crescentic glomerulonephritis: role of p38MAPKalpha.

OBJECTIVE: Crescentic glomerulonephritis (crGN) is a frequent and life-threatening manifestation of antineutrophil cytoplasmatic antibody-associated vasculitis. Up-regulation of proinflammatory cytokines contributes to renal damage by activation of p38 mitogen-activated protein kinases (MAPKs). However, it is unclear which of the four p38MAPK isoforms are expressed, activated and hence of major importance in crGN. METHODS: Kidney biopsies of patients with antineutrophil cytoplasmatic antibody-positive crGN and control samples were investigated for the expression and phosphorylation of p38MAPK isoforms and downstream target kinase MAPKAP2 by immunohistochemistry. Expression and functional activation of p38MAPK isoforms by TNF was also assessed in a human podocyte cell line by reverse transcription-polymerase chain reaction, immunoblotting and kinase array. RESULTS: Strong expression of p38MAPKalpha, beta and gamma isoforms was found in glomerular podocytes and crescents. Infiltrating leucocytes showed predominant p38MAPKalpha expression. Activation of p38MAPK and its downstream mediator MAPKAP2 was found in crGN confined to glomerular podocytes, crescents and inflammatory infiltrates. Interestingly, corticosteroid treatment before kidney biopsy diminished p38MAPK activation in crGN. Activated p38MAPK co-localised with alpha, beta and gamma isoforms in podocytes and crescents, while leucocytes showed mainly p38MAPKalpha activation. In a human podocyte cell line mRNA and protein of all four p38MAPK isoforms was expressed but only p38MAPKalpha was activated upon challenge with TNF. CONCLUSIONS: This study shows selective p38MAPK isoform expression and activation in crGN. Podocytes and podocyte-induce crescent formation is the main source of p38MAPK activation in crGN. TNF is a potent and selective activator of the alpha-isoform in podocytes, which therefore appears as a main contributor to proinflammatory signalling in the glomerulum of crGN.

Disruption of the protein C inhibitor gene results in impaired spermatogenesis and male infertility.

Protein C inhibitor (PCI) is a nonspecific, heparin-binding serpin (serine protease inhibitor) that inactivates many plasmatic and extravascular serine proteases by forming stable 1:1 complexes. Proteases inhibited by PCI include the anticoagulant activated protein C, the plasminogen activator urokinase, and the sperm protease acrosin. In humans PCI circulates as a plasma protein but is also present at high concentrations in organs of the male reproductive tract. The biological role of PCI has not been defined so far. However, the colocalization of high concentrations of PCI together with several of its target proteases in the male reproductive tract suggests a role of PCI in reproduction. We generated mice lacking PCI by homologous recombination. Here we show that PCI(-/-) mice are apparently healthy but that males of this genotype are infertile. Infertility was apparently caused by abnormal spermatogenesis due to destruction of the Sertoli cell barrier, perhaps due to unopposed proteolytic activity. The resulting sperm are malformed and are morphologically similar to abnormal sperm seen in some cases of human male infertility. This animal model might therefore be useful for analyzing the molecular bases of these human conditions.

Milk fat globule-EGF factor 8 mediates the enhancement of apoptotic cell clearance by glucocorticoids.

The phagocytic clearance of apoptotic cells is essential to prevent chronic inflammation and autoimmunity. The phosphatidylserine-binding protein milk fat globule-EGF factor 8 (MFG-E8) is a major opsonin for apoptotic cells, and MFG-E8(-/-) mice spontaneously develop a lupus-like disease. Similar to human systemic lupus erythematosus (SLE), the murine disease is associated with an impaired clearance of apoptotic cells. SLE is routinely treated with glucocorticoids (GCs), whose anti-inflammatory effects are consentaneously attributed to the transrepression of pro-inflammatory cytokines. Here, we show that the GC-mediated transactivation of MFG-E8 expression and the concomitantly enhanced elimination of apoptotic cells constitute a novel aspect in this context. Patients with chronic inflammation receiving high-dose prednisone therapy displayed substantially increased MFG-E8 mRNA levels in circulating monocytes. MFG-E8 induction was dependent on the GC receptor and several GC response elements within the MFG-E8 promoter. Most intriguingly, the inhibition of MFG-E8 induction by RNA interference or genetic knockout strongly reduced or completely abolished the phagocytosis-enhancing effect of GCs in vitro and in vivo. Thus, MFG-E8-dependent promotion of apoptotic cell clearance is a novel anti-inflammatory facet of GC treatment and renders MFG-E8 a prospective target for future therapeutic interventions in SLE.