A randomised phase II trial of temozolomide with or without cannabinoids in patients with recurrent glioblastoma (ARISTOCRAT): protocol for a multi-centre, double-blind, placebo-controlled trial.

BACKGROUND: Glioblastoma (GBM) is the most common adult malignant brain tumour, with an incidence of 5 per 100,000 per year in England. Patients with tumours showing O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation represent around 40% of newly diagnosed GBM. Relapse/tumour recurrence is inevitable. There is no agreed standard treatment for patients with GBM, therefore, it is aimed at delaying further tumour progression and maintaining health-related quality of life (HRQoL). Limited clinical trial data exist using cannabinoids in combination with temozolomide (TMZ) in this setting, but early phase data demonstrate prolonged overall survival compared to TMZ alone, with few additional side effects. Jazz Pharmaceuticals (previously GW Pharma Ltd.) have developed nabiximols (trade name Sativex®), an oromucosal spray containing a blend of cannabis plant extracts, that we aim to assess for preliminary efficacy in patients with recurrent GBM. METHODS: ARISTOCRAT is a phase II, multi-centre, double-blind, placebo-controlled, randomised trial to assess cannabinoids in patients with recurrent MGMT methylated GBM who are suitable for treatment with TMZ. Patients who have relapsed ≥ 3 months after completion of initial first-line treatment will be randomised 2:1 to receive either nabiximols or placebo in combination with TMZ. The primary outcome is overall survival time defined as the time in whole days from the date of randomisation to the date of death from any cause. Secondary outcomes include overall survival at 12 months, progression-free survival time, HRQoL (using patient reported outcomes from QLQ-C30, QLQ-BN20 and EQ-5D-5L questionnaires), and adverse events. DISCUSSION: Patients with recurrent MGMT promoter methylated GBM represent a relatively good prognosis sub-group of patients with GBM. However, their median survival remains poor and, therefore, more effective treatments are needed. The phase II design of this trial was chosen, rather than phase III, due to the lack of data currently available on cannabinoid efficacy in this setting. A randomised, double-blind, placebo-controlled trial will ensure an unbiased robust evaluation of the treatment and will allow potential expansion of recruitment into a phase III trial should the emerging phase II results warrant this development. TRIAL REGISTRATION: ISRCTN: 11460478. CLINICALTRIALS: Gov: NCT05629702.

Investigator choice of standard therapy versus sequential novel therapy arms in the treatment of relapsed follicular lymphoma (REFRACT): study protocol for a multi-centre, open-label, randomised, phase II platform trial.

BACKGROUND: Relapsed or refractory follicular lymphoma (rrFL) is an incurable disease associated with shorter remissions and survival after each line of standard therapy. Many promising novel, chemotherapy-free therapies are in development, but few are licensed as their role in current treatment pathways is poorly defined. METHODS: The REFRACT trial is an investigator-initiated, UK National Cancer Research Institute, open-label, multi-centre, randomised phase II platform trial aimed at accelerating clinical development of novel therapies by addressing evidence gaps. The first of the three sequential novel therapy arms is epcoritamab plus lenalidomide, to be compared with investigator choice standard therapy (ICT). Patients aged 18 years or older with biopsy proven relapsed or refractory CD20 positive, grade 1-3a follicular lymphoma and assessable disease by PET-CT are eligible. The primary outcome is complete metabolic response by PET-CT at 24 weeks using the Deauville 5-point scale and Lugano 2014 criteria. Secondary outcomes include overall metabolic response, progression-free survival, overall survival, duration of response, and quality of life assessed by EQ-5D-5 L and FACT-Lym. The trial employs an innovative Bayesian design with a target sample size of 284 patients: 95 in the ICT arm and 189 in the novel therapy arms. DISCUSSION: Whilst there are many promising novel drugs in early clinical development for rrFL, understanding the relative efficacy and safety of these agents, and their place in modern treatment pathways, is limited by a lack of randomised trials and dearth of published outcomes for standard regimens to act as historic controls. Therefore, the aim of REFRACT is to provide an efficient platform to evaluate novel agents against standard therapies for rrFL. The adaptive Bayesian power prior methodology design will minimise patient numbers and accelerate trial delivery. TRIAL REGISTRATION: ClinicalTrials.gov: NCT05848765; 08-May-2023. EUDRACT: 2022-000677-75; 10-Feb-2022.

Lymphatic blood filling in CLEC-2-deficient mouse models.

C-type lectin-like receptor 2 (CLEC-2) is considered as a potential drug target in settings of wound healing, inflammation, and infection. A potential barrier to this is evidence that CLEC-2 and its ligand podoplanin play a critical role in preventing lymphatic vessel blood filling in mice throughout life. In this study, this aspect of CLEC-2/podoplanin function is investigated in more detail using new and established mouse models of CLEC-2 and podoplanin deficiency, and models of acute and chronic vascular remodeling. We report that CLEC-2 expression on platelets is not required to maintain a barrier between the blood and lymphatic systems in unchallenged mice, post-development. However, under certain conditions of chronic vascular remodeling, such as during tumorigenesis, deficiency in CLEC-2 can lead to lymphatic vessel blood filling. These data provide a new understanding of the function of CLEC-2 in adult mice and confirm the essential nature of CLEC-2-driven platelet activation in vascular developmental programs. This work expands our understanding of how lymphatic blood filling is prevented by CLEC-2-dependent platelet function and provides a context for the development of safe targeting strategies for CLEC-2 and podoplanin.

Appropriation of GPIbα from platelet-derived extracellular vesicles supports monocyte recruitment in systemic inflammation.

Interactions between platelets, leukocytes and the vessel wall provide alternative pathological routes of thrombo-inflammatory leukocyte recruitment. We found that when platelets were activated by a range of agonists in whole blood, they shed platelet-derived extracellular vesicles which rapidly and preferentially bound to blood monocytes compared to other leukocytes. Platelet-derived extracellular vesicle binding to monocytes was initiated by P-selectin-dependent adhesion and was stabilised by binding of phosphatidylserine. These interactions resulted in the progressive transfer of the platelet adhesion receptor GPIbα to monocytes. GPIbα+-monocytes tethered and rolled on immobilised von Willebrand Factor or were recruited and activated on endothelial cells treated with TGF-ß1 to induce the expression of von Willebrand Factor. In both models monocyte adhesion was ablated by a function-blocking antibody against GPIbα. Monocytes could also bind platelet-derived extracellular vesicle in mouse blood in vitro and in vivo Intratracheal instillations of diesel nanoparticles, to model chronic pulmonary inflammation, induced accumulation of GPIbα on circulating monocytes. In intravital experiments, GPIbα+-monocytes adhered to the microcirculation of the TGF-ß1-stimulated cremaster muscle, while in the ApoE-/- model of atherosclerosis, GPIbα+-monocytes adhered to the carotid arteries. In trauma patients, monocytes bore platelet markers within 1 hour of injury, the levels of which correlated with severity of trauma and resulted in monocyte clearance from the circulation. Thus, we have defined a novel thrombo-inflammatory pathway in which platelet-derived extracellular vesicles transfer a platelet adhesion receptor to monocytes, allowing their recruitment in large and small blood vessels, and which is likely to be pathogenic.

Platelet glycoprotein VI and C-type lectin-like receptor 2 deficiency accelerates wound healing by impairing vascular integrity in mice.

Platelets promote wound healing by forming a vascular plug and by secreting growth factors and cytokines. Glycoprotein (GP)VI and C-type lectin-like receptor (CLEC)-2 signal through a (hem)-immunoreceptor tyrosine-based activation motif, which induces platelet activation. GPVI and CLEC-2 support vascular integrity during inflammation in the skin through regulation of leukocyte migration and function, and by sealing sites of vascular damage. In this study, we investigated the role of impaired vascular integrity due to GPVI and/or CLEC-2 deficiency in wound repair using a full-thickness excisional skin wound model in mice. Transgenic mice deficient in both GPVI and CLEC-2 exhibited accelerated skin wound healing, despite a marked impairment in vascular integrity. The local and temporal bleeding in the skin led to greater plasma protein entry, including fibrinogen and clotting factors, was associated with increased fibrin generation, reduction in wound neutrophils and M1 macrophages, decreased level of tumor necrosis factor (TNF)-α, and enhanced angiogenesis at day 3 after injury. Accelerated wound healing was not due to developmental defects in CLEC-2 and GPVI double-deficient mice as similar results were observed in GPVI-deficient mice treated with a podoplanin-blocking antibody. The rate of wound healing was not altered in mice deficient in either GPVI or CLEC-2. Our results show that, contrary to defects in coagulation, bleeding following a loss of vascular integrity caused by platelet CLEC-2 and GPVI deficiency facilitates wound repair by increasing fibrin(ogen) deposition, reducing inflammation, and promoting angiogenesis.

Platelet CLEC-2 protects against lung injury via effects of its ligand podoplanin on inflammatory alveolar macrophages in the mouse.

There is no therapeutic intervention proven to prevent acute respiratory distress syndrome (ARDS). Novel mechanistic insights into the pathophysiology of ARDS are therefore required. Platelets are implicated in regulating many of the pathogenic processes that occur during ARDS; however, the mechanisms remain elusive. The platelet receptor CLEC-2 has been shown to regulate vascular integrity at sites of acute inflammation. Therefore the purpose of this study was to establish the role of CLEC-2 and its ligand podoplanin in a mouse model of ARDS. Platelet-specific CLEC-2-deficient, as well as alveolar epithelial type I cell (AECI)-specific or hematopoietic-specific podoplanin deficient, mice were established using cre-loxP strategies. Combining these with intratracheal (IT) instillations of lipopolysaccharide (LPS), we demonstrate that arterial oxygen saturation decline in response to IT-LPS in platelet-specific CLEC-2-deficient mice is significantly augmented. An increase in bronchoalveolar lavage (BAL) neutrophils and protein was also observed 48 h post-IT-LPS, with significant increases in pro-inflammatory chemokines detected in BAL of platelet-specific CLEC-2-deficient animals. Deletion of podoplanin from hematopoietic cells but not AECIs also reduces lung function and increases pro-inflammatory chemokine expression following IT-LPS. Furthermore, we demonstrate that following IT-LPS, platelets are present in BAL in aggregates with neutrophils, which allows for CLEC-2 interaction with podoplanin expressed on BAL inflammatory alveolar macrophages. Taken together, these data suggest that the platelet CLEC-2-podoplanin signaling axis regulates the severity of lung inflammation in mice and is a possible novel target for therapeutic intervention in patients at risk of developing ARDS.

Vitamin D Deficiency in Human and Murine Sepsis.

OBJECTIVES: Vitamin D deficiency has been implicated as a pathogenic factor in sepsis and ICU mortality but causality of these associations has not been demonstrated. To determine whether sepsis and severe sepsis are associated with vitamin D deficiency and to determine whether vitamin D deficiency influences the severity of sepsis. DESIGN, SETTING, AND PATIENTS: Sixty-one patients with sepsis and severe sepsis from two large U.K. hospitals and 20 healthy controls were recruited. Murine models of cecal ligation and puncture and intratracheal lipopolysaccharide were undertaken in normal and vitamin D deficient mice to address the issue of causality. MEASUREMENTS AND MAIN RESULTS: Patients with severe sepsis had significantly lower concentrations of 25-hydroxyvitamin D3 than patients with either mild sepsis or age-matched healthy controls (15.7 vs 49.5 vs 66.5 nmol/L; p = 0.0001). 25-hydroxyvitamin D3 concentrations were significantly lower in patients who had positive microbiologic culture than those who were culture negative (p = 0.0023) as well as those who died within 30 days of hospital admission (p = 0.025). Vitamin D deficiency in murine sepsis was associated with increased peritoneal (p = 0.037), systemic (p = 0.019), and bronchoalveolar lavage (p = 0.011) quantitative bacterial culture. This was associated with reduced local expression of the cathelicidin-related antimicrobial peptide as well as evidence of defective macrophage phagocytosis (p = 0.029). In the intratracheal lipopolysaccharide model, 1,500 IU of intraperitoneal cholecalciferol treatment 6 hours postinjury reduced alveolar inflammation, cellular damage, and hypoxia. CONCLUSIONS: Vitamin D deficiency is common in severe sepsis. This appears to contribute to the development of the condition in clinically relevant murine models and approaches to correct vitamin D deficiency in patients with sepsis should be developed.

Vitamin D deficiency contributes directly to the acute respiratory distress syndrome (ARDS).

RATIONALE: Vitamin D deficiency has been implicated as a pathogenic factor in sepsis and intensive therapy unit mortality but has not been assessed as a risk factor for acute respiratory distress syndrome (ARDS). Causality of these associations has never been demonstrated. OBJECTIVES: To determine if ARDS is associated with vitamin D deficiency in a clinical setting and to determine if vitamin D deficiency in experimental models of ARDS influences its severity. METHODS: Human, murine and in vitro primary alveolar epithelial cell work were included in this study. FINDINGS: Vitamin D deficiency (plasma 25(OH)D levels <50 nmol/L) was ubiquitous in patients with ARDS and present in the vast majority of patients at risk of developing ARDS following oesophagectomy. In a murine model of intratracheal lipopolysaccharide challenge, dietary-induced vitamin D deficiency resulted in exaggerated alveolar inflammation, epithelial damage and hypoxia. In vitro, vitamin D has trophic effects on primary human alveolar epithelial cells affecting >600 genes. In a clinical setting, pharmacological repletion of vitamin D prior to oesophagectomy reduced the observed changes of in vivo measurements of alveolar capillary damage seen in deficient patients. CONCLUSIONS: Vitamin D deficiency is common in people who develop ARDS. This deficiency of vitamin D appears to contribute to the development of the condition, and approaches to correct vitamin D deficiency in patients at risk of ARDS should be developed. TRIAL REGISTRATION: UKCRN ID 11994.

Pericytes promote selective vessel regression to regulate vascular patterning.

Blood vessel networks form in a 2-step process of sprouting angiogenesis followed by selective branch regression and stabilization of remaining vessels. Pericytes are known to function in stabilizing blood vessels, but their role in vascular sprouting and selective vessel regression is poorly understood. The endosialin (CD248) receptor is expressed by pericytes associated with newly forming but not stable quiescent vessels. In the present study, we used the Endosialin(-/-) mouse as a means to uncover novel roles for pericytes during the process of vascular network formation. We demonstrate in a postnatal retina model that Endosialin(-/-) mice have normal vascular sprouting but are defective in selective vessel regression, leading to increased vessel density. Examination of the Endosialin(-/-) mouse tumor vasculature revealed an equivalent phenotype, indicating that pericytes perform a hitherto unidentified function to promote vessel destabilization and regression in vivo in both physiologic and pathologic angiogenesis. Mechanistically, Endosialin(-/-) mice have no defect in pericyte recruitment. Rather, endosialin binding to an endothelial associated, but not a pericyte associated, basement membrane component induces endothelial cell apoptosis and detachment. The results of the present study advance our understanding of pericyte biology and pericyte/endothelial cell cooperation during vascular patterning and have implications for the design of both pro- and antiangiogenic therapies.

Thymic function is maintained during Salmonella-induced atrophy and recovery.

Thymic atrophy is a frequent consequence of infection with bacteria, viruses, and parasites and is considered a common virulence trait between pathogens. Multiple reasons have been proposed to explain this atrophy, including premature egress of immature thymocytes, increased apoptosis, or thymic shutdown to prevent tolerance to the pathogen from developing. The severe loss in thymic cell number can reflect an equally dramatic reduction in thymic output, potentially reducing peripheral T cell numbers. In this study, we examine the relationship between systemic Salmonella infection and thymic function. During infection, naive T cell numbers in peripheral lymphoid organs increase. Nevertheless, this occurs despite a pronounced thymic atrophy caused by viable bacteria, with a peak 50-fold reduction in thymocyte numbers. Thymic atrophy is not dependent upon homeostatic feedback from peripheral T cells or on regulation of endogenous glucocorticoids, as demonstrated by infection of genetically altered mice. Once bacterial numbers fall, thymocyte numbers recover, and this is associated with increases in the proportion and proliferation of early thymic progenitors. During atrophy, thymic T cell maturation is maintained, and single-joint TCR rearrangement excision circle analysis reveals there is only a modest fall in recent CD4(+) thymic emigrants in secondary lymphoid tissues. Thus, thymic atrophy does not necessarily result in a matching dysfunctional T cell output, and thymic homeostasis can constantly adjust to systemic infection to ensure that naive T cell output is maintained.

Vascular adhesion protein-1 blockade in primary sclerosing cholangitis: Open-label, multicenter, single-arm, phase II trial.

BACKGROUND: Primary sclerosing cholangitis is a progressive inflammatory liver disease characterized by biliary and liver fibrosis. Vascular adhesion protein-1 (VAP-1) is important in the inflammatory process driving liver fibrosis. We evaluated the safety and efficacy of VAP-1 blockade with a monoclonal antibody (timolumab, BTT1023) in patients with primary sclerosing cholangitis. METHODS: BUTEO was a prospective, single-arm, open-label, multicenter, phase II trial, conducted in 6 centers in the United Kingdom. Patients with primary sclerosing cholangitis aged 18-75 years had an alkaline phosphatase value of >1.5 times the upper limit of normal. The dose-confirmatory stage aimed to confirm the safety of timolumab through the incidence of dose-limiting toxicity and sufficient trough levels of circulating antibody to block VAP-1 function. The primary outcome of the dose-expansion portion of the trial was patient's response to timolumab at day 99, as measured by a reduction in serum alkaline phosphatase by 25% or more from baseline to day 99. RESULTS: Twenty-three patients were recruited: 7 into the initial dose-confirmatory stage and a further 16 into an expansion stage. Timolumab (8 mg/kg) was confirmed to be safe for the duration of administration with sufficient circulating levels. Only 2 of the 18 evaluable patients (11.1%) achieved a reduction in alkaline phosphatase levels of 25% or more, and both the proportion of circulating inflammatory cell populations and biomarkers of fibrosis remained unchanged from baseline. CONCLUSIONS: The BUTEO trial confirmed 8 mg/kg timolumab had no short-term safety signals and resulted in sufficient circulating levels of VAP-1 blocking timolumab. However, the trial was stopped after an interim assessment due to a lack of efficacy as determined by no significant change in serum liver tests.

Impaired alveolar macrophage 11ß-hydroxysteroid dehydrogenase type 1 reductase activity contributes to increased pulmonary inflammation and mortality in sepsis-related ARDS.

Background: Acute Respiratory Distress Syndrome (ARDS) is a devastating pulmonary inflammatory disorder, commonly precipitated by sepsis. Glucocorticoids are immunomodulatory steroids that can suppress inflammation. Their anti-inflammatory properties within tissues are influenced by their pre-receptor metabolism and amplification from inactive precursors by 11ß-hydroxysteroid dehydrogenase type-1 (HSD-1). We hypothesised that in sepsis-related ARDS, alveolar macrophage (AM) HSD-1 activity and glucocorticoid activation are impaired, and associated with greater inflammatory injury and worse outcomes. Methods: We analysed broncho-alveolar lavage (BAL) and circulating glucocorticoid levels, AM HSD-1 reductase activity and Receptor for Advanced Glycation End-products (RAGE) levels in two cohorts of critically ill sepsis patients, with and without ARDS. AM HSD-1 reductase activity was also measured in lobectomy patients. We assessed inflammatory injury parameters in models of lung injury and sepsis in HSD-1 knockout (KO) and wild type (WT) mice. Results: No difference in serum and BAL cortisol: cortisone ratios are shown between sepsis patients with and without ARDS. Across all sepsis patients, there is no association between BAL cortisol: cortisone ratio and 30-day mortality. However, AM HSD-1 reductase activity is impaired in patients with sepsis-related ARDS, compared to sepsis patients without ARDS and lobectomy patients (0.075 v 0.882 v 0.967 pM/hr/106 AMs, p=0.004). Across all sepsis patients (with and without ARDS), impaired AM HSD-1 reductase activity is associated with defective efferocytosis (r=0.804, p=0.008) and increased 30-day mortality. AM HSD-1 reductase activity negatively correlates with BAL RAGE in sepsis patients with ARDS (r=-0.427, p=0.017). Following intra-tracheal lipopolysaccharide (IT-LPS) injury, HSD-1 KO mice demonstrate increased alveolar neutrophil infiltration, apoptotic neutrophil accumulation, alveolar protein permeability and BAL RAGE concentrations compared to WT mice. Caecal Ligation and Puncture (CLP) injury in HSD-1 KO mice results in greater peritoneal apoptotic neutrophil accumulation compared to WT mice. Conclusions: AM HSD-1 reductase activity does not shape total BAL and serum cortisol: cortisone ratios, however impaired HSD-1 autocrine signalling renders AMs insensitive to the anti-inflammatory effects of local glucocorticoids. This contributes to the decreased efferocytosis, increased BAL RAGE concentrations and mortality seen in sepsis-related ARDS. Upregulation of alveolar HSD-1 activity could restore AM function and improve clinical outcomes in these patients.

The stromal cell antigen CD248 (endosialin) is expressed on naive CD8+ human T cells and regulates proliferation.

CD248 (endosialin) is a transmembrane glycoprotein that is dynamically expressed on pericytes and fibroblasts during tissue development, tumour neovascularization and inflammation. Its role in tissue remodelling is associated with increased stromal cell proliferation and migration. We show that CD248 is also uniquely expressed by human, but not mouse (C57BL/6), CD8(+) naive T cells. CD248 is found only on CD8(+) CCR7(+) CD11a(low) naive T cells and on CD8 single-positive T cells in the thymus. Transfection of the CD248 negative T-cell line MOLT-4 with CD248 cDNA surprisingly reduced cell proliferation. Knock-down of CD248 on naive CD8 T cells increased cell proliferation. These data demonstrate opposing functions for CD248 on haematopoietic (CD8(+)) versus stromal cells and suggests that CD248 helps to maintain naive CD8(+) human T cells in a quiescent state.

The pericyte and stromal cell marker CD248 (endosialin) is required for efficient lymph node expansion.

CD248 is a cell surface receptor that specifically identifies fibroblasts and pericytes during development and in association with cancer and inflammation. However, its function is poorly defined and its role in lymphoid organs not studied. Here, we used (4-hydroxy-3-nitrophenyl)acetyl chicken gamma-globulin immunisation and mice lacking CD248 to study whether CD248 modulates popliteal LN (pLN) expansion and subsequent immune responses. We have found that CD248 is required for complete pLN expansion but not for co-ordination of B and T cell compartmentalisation or antibody production following (4-hydroxy-3-nitrophenyl)acetyl chicken gamma-globulin immunisation. In vitro, we show that CD248 expression in human MG63 stromal cells and mouse embryonic fibroblasts leads to a pro-proliferative and pro-migratory phenotype. This correlates with a proliferating CD248(+) population observed in vivo during pLN expansion. Taken together, these data highlight a role for CD248 in secondary lymphoid organ remodelling during adaptive immune responses.

Heterozygous mutation SLFN14 K208N in mice mediates species-specific differences in platelet and erythroid lineage commitment.

Schlafen 14 (SLFN14) has recently been identified as an endoribonuclease responsible for cleaving RNA to regulate and inhibit protein synthesis. Early studies revealed that members of the SLFN family are capable of altering lineage commitment during T-cell differentiation by using cell-cycle arrest as a means of translational control by RNase activity. SLFN14 has been reported as a novel gene causing an inherited macrothrombocytopenia and bleeding in human patients; however, the role of this endoribonuclease in megakaryopoiesis and thrombopoiesis remains unknown. To investigate this, we report a CRISPR knock-in mouse model of SLFN14 K208N homologous to the K219N mutation observed in our previous patient studies. We used hematological analysis, in vitro and in vivo studies of platelet and erythrocyte function, and analysis of spleen and bone marrow progenitors. Mice homozygous for this mutation do not survive to weaning age, whereas heterozygotes exhibit microcytic erythrocytosis, hemolytic anemia, splenomegaly, and abnormal thrombus formation, as revealed by intravital microscopy, although platelet function and morphology remain unchanged. We also show that there are differences in erythroid progenitors in the spleens and bone marrow of these mice, indicative of an upregulation of erythropoiesis. This SLFN14 mutation presents distinct species-specific phenotypes, with a platelet defect reported in humans and a severe microcytic erythrocytosis in mice. Thus, we conclude that SLFN14 is a key regulator in mammalian hematopoiesis and a species-specific mediator of platelet and erythroid lineage commitment.

Keratinocyte differentiation is regulated by the Rho and ROCK signaling pathway.

The epidermis comprises multiple layers of specialized epithelial cells called keratinocytes. As cells are lost from the outermost epidermal layers, they are replaced through terminal differentiation, in which keratinocytes of the basal layer cease proliferating, migrate upwards, and eventually reach the outermost cornified layers. Normal homeostasis of the epidermis requires that the balance between proliferation and differentiation be tightly regulated. The GTP binding protein RhoA plays a fundamental role in the regulation of the actin cytoskeleton and in the adhesion events that are critically important to normal tissue homeostasis. Two central mediators of the signals from RhoA are the ROCK serine/threonine kinases ROCK-I and ROCK-II. We have analyzed ROCK's role in the regulation of epidermal keratinocyte function by using a pharmacological inhibitor and expressing conditionally active or inactive forms of ROCK-II in primary human keratinocytes. We report that blocking ROCK function results in inhibition of keratinocyte terminal differentiation and an increase in cell proliferation. In contrast, activation of ROCK-II in keratinocytes results in cell cycle arrest and an increase in the expression of a number of genes associated with terminal differentiation. Thus, these results indicate that ROCK plays a critical role in regulating the balance between proliferation and differentiation in human keratinocytes.

CD248/Endosialin is dynamically expressed on a subset of stromal cells during lymphoid tissue development, splenic remodeling and repair.

Studies of stromal cell populations in lymphoid tissue (LT) have been hampered by a lack of selective markers. Here, we show that CD248 (Endosialin/TEM1) is a stromal marker that is differentially expressed on fibroblasts and pericytes in the thymus, lymph node and spleen. Expression is high during LT development but largely disappears in the adult. CD248 is re-expressed in a Salmonella-induced model of splenic enlargement; peak expression corresponding to the peak of splenic enlargement. These results suggest that CD248 expression helps define a subset of LT stromal cells which play a role in remodelling during tissue development, infection and repair.

Effect of anti-podoplanin antibody administration during lipopolysaccharide-induced lung injury in mice.

INTRODUCTION: Acute respiratory distress syndrome (ARDS) is a devastating pulmonary condition in the critically ill patient. A therapeutic intervention is yet to be found that can prevent progression to ARDS. We recently demonstrated that the interaction between podoplanin expressed on inflammatory alveolar macrophages (iAMs) and its endogenous ligand, platelet C-type lectin-like 2 (CLEC-2), protects against exaggerated lung inflammation during a mouse model of ARDS. In this study, we aim to investigate the therapeutic use of a crosslinking/activating anti-podoplanin antibody (α-PDPN, clone 8.1.1) during lipopolysaccharide (LPS)-induced lung inflammation in mice. METHODS: Intravenous administration of α-PDPN was performed 6 hours after intratracheal LPS in wildtype, C57Bl/6 mice. Lung function decline was measured by pulse oximetry as well as markers of local inflammation including bronchoalveolar lavage neutrophilia and cytokine/chemokine expression. In parallel, alveolar macrophages were isolated and cultured in vitro from haematopoietic-specific podoplanin-deficient mice (Pdpnfl/flVAV1cre+) and floxed-only controls treated with or without LPS in the presence or absence of α-PDPN. RESULTS: Lung function decline as well as alveolar neutrophil recruitment was significantly decreased in mice treated with the crosslinking/activating α-PDPN in vivo. Furthermore, we demonstrate that, in vitro, activation of podoplanin on iAMs regulates their secretion of proinflammatory cytokines and chemokines. CONCLUSIONS: These data confirm the importance of the CLEC-2-podoplanin pathway during intratracheal (IT)-LPS and demonstrate the beneficial effect of targeting podoplanin during IT-LPS in mice possibly via modulation of local cytokine/chemokine expression. Moreover, these data suggest that podoplanin-targeted therapies may have a beneficial effect in patients at risk of developing ARDS.

The podoplanin-CLEC-2 axis inhibits inflammation in sepsis.

Platelets play a critical role in vascular inflammation through the podoplanin and collagen/fibrin receptors, C-type-lectin-like-2 (CLEC-2) and glycoprotein VI (GPVI), respectively. Both receptors regulate endothelial permeability and prevent peri-vascular bleeding in inflammation. Here we show that platelet-specific deletion of CLEC-2 but not GPVI leads to enhanced systemic inflammation and accelerated organ injury in two mouse models of sepsis-intra-peritoneal lipopolysaccharide and cecal ligation and puncture. CLEC-2 deficiency is associated with reduced numbers of podoplanin-expressing macrophages despite increased cytokine and chemokine levels in the infected peritoneum. Pharmacological inhibition of the interaction between CLEC-2 and podoplanin regulates immune cell infiltration and the inflammatory reaction during sepsis, suggesting that activation of podoplanin underlies the anti-inflammatory action of platelet CLEC-2. We suggest podoplanin-CLEC-2 as a novel anti-inflammatory axis regulating immune cell recruitment and activation in sepsis.