Bcl6 is a subset-defining transcription factor of lymphoid tissue inducer-like ILC3.

Innate lymphoid cells (ILCs) are tissue-resident effector cells with roles in tissue homeostasis, protective immunity, and inflammatory disease. Group 3 ILCs (ILC3s) are classically defined by the master transcription factor RORγt. However, ILC3 can be further subdivided into subsets that share type 3 effector modules that exhibit significant ontological, transcriptional, phenotypic, and functional heterogeneity. Notably lymphoid tissue inducer (LTi)-like ILC3s mediate effector functions not typically associated with other RORγt-expressing lymphocytes, suggesting that additional transcription factors contribute to dictate ILC3 subset phenotypes. Here, we identify Bcl6 as a subset-defining transcription factor of LTi-like ILC3s in mice and humans. Deletion of Bcl6 results in dysregulation of the LTi-like ILC3 transcriptional program and markedly enhances expression of interleukin-17A (IL-17A) and IL-17F in LTi-like ILC3s in a manner in part dependent upon the commensal microbiota-and associated with worsened inflammation in a model of colitis. Together, these findings redefine our understanding of ILC3 subset biology.

Trainee autonomy and surgical outcomes after emergency gastrointestinal surgery.

BACKGROUND: Operative meaningful trainee autonomy is an essential component of surgical training. Reduced trainee autonomy is frequently attributed to patient safety concerns, but this has not been examined within Kenya. We aimed to assess whether meaningful trainee autonomy was associated with a change in patient outcomes. METHODS: We investigated whether meaningful trainee autonomy was associated with a change in severe postoperative complications and all-cause in-hospital mortality in a previously described cohort undergoing emergency gastrointestinal operations. Each operation was reviewed to determine the presence of meaningful autonomy, defined as "supervision only" from faculty. Comparisons were made between faculty-led cases and cases with meaningful trainee autonomy. Multilevel logistic regression models were created for the outcomes of mortality and complications with the exposure of meaningful trainee autonomy, accounting for fixed effects of the Africa Surgical Outcomes Study Risk Score and random effects of discharge diagnoses. RESULTS: After excluding laparoscopy (N = 28) and missing data (N = 3), 451 operations were studied, and 343 (76.1%) had meaningful trainee autonomy. Faculty were more involved in operations with older age, cancer, prior complications, and higher risk scores. On unadjusted analysis, meaningful trainee autonomy was associated with mortality odds of 0.32 (95% confidence interval: 0.17-0.58) compared with faculty-led operations. Similarly, the odds of developing complications were 0.52 (95% confidence interval: 0.32-0.84) with meaningful trainee autonomy compared with faculty-led operations. When adjusting for Africa Surgical Outcomes Study Score and clustering discharge diagnoses, the odds of mortality (odds ratio 0.58; 95% confidence interval: 0.27-1.2) and complication (odds ratio 0.83; 95% confidence interval: 0.47-1.5) were not significant. CONCLUSION: Our findings support that increasing trainee autonomy does not change patient outcomes in selected emergency gastrointestinal operations. Further, trainees and faculty appropriately discern patients at higher risk of complications and mortality, and the selective granting of trainee autonomy does not affect patient safety.

Epithelial coxsackievirus adenovirus receptor promotes house dust mite-induced lung inflammation.

Airway inflammation and remodelling are important pathophysiologic features in asthma and other respiratory conditions. An intact epithelial cell layer is crucial to maintain lung homoeostasis, and this depends on intercellular adhesion, whilst damaged respiratory epithelium is the primary instigator of airway inflammation. The Coxsackievirus Adenovirus Receptor (CAR) is highly expressed in the epithelium where it modulates cell-cell adhesion stability and facilitates immune cell transepithelial migration. However, the contribution of CAR to lung inflammation remains unclear. Here we investigate the mechanistic contribution of CAR in mediating responses to the common aeroallergen, House Dust Mite (HDM). We demonstrate that administration of HDM in mice lacking CAR in the respiratory epithelium leads to loss of peri-bronchial inflammatory cell infiltration, fewer goblet-cells and decreased pro-inflammatory cytokine release. In vitro analysis in human lung epithelial cells confirms that loss of CAR leads to reduced HDM-dependent inflammatory cytokine release and neutrophil migration. Epithelial CAR depletion also promoted smooth muscle cell proliferation mediated by GSK3ß and TGF-ß, basal matrix production and airway hyperresponsiveness. Our data demonstrate that CAR coordinates lung inflammation through a dual function in leucocyte recruitment and tissue remodelling and may represent an important target for future therapeutic development in inflammatory lung diseases.

Cyclin-dependent Kinase 9 as a Potential Target for Anti-TNF-resistant Inflammatory Bowel Disease.

BACKGROUND & AIMS: Resistance to single cytokine blockade, namely anti-tumor necrosis factor (TNF) therapy, is a growing concern for patients with inflammatory bowel disease (IBD). The transcription factor T-bet is a critical regulator of intestinal homeostasis, is genetically linked to mucosal inflammation and controls the expression of multiples genes such as the pro-inflammatory cytokines interferon (IFN)-γ and TNF. Inhibiting T-bet may therefore offer a more attractive prospect for treating IBD but remains challenging to target therapeutically. In this study, we evaluate the effect of targeting the transactivation function of T-bet using inhibitors of P-TEFb (CDK9-cyclin T), a transcriptional elongation factor downstream of T-bet. METHODS: Using an adaptive immune-mediated colitis model, human colonic lymphocytes from patients with IBD and multiple large clinical datasets, we investigate the effect of cyclin-dependent kinase 9 (CDK9) inhibitors on cytokine production and gene expression in colonic CD4+ T cells and link these genetic modules to clinical response in patients with IBD. RESULTS: Systemic CDK9 inhibition led to histological improvement of immune-mediated colitis and was associated with targeted suppression of colonic CD4+ T cell-derived IFN-γ and IL-17A. In colonic lymphocytes from patients with IBD, CDK9 inhibition potently repressed genes responsible for pro-inflammatory signalling, and in particular genes regulated by T-bet. Remarkably, CDK9 inhibition targeted genes that were highly expressed in anti-TNF resistant IBD and that predicted non-response to anti-TNF therapy. CONCLUSION: Collectively, our findings reveal CDK9 as a potential target for anti-TNF-resistant IBD, which has the potential for rapid translation to the clinic.

Effects of canagliflozin versus finerenone on cardiorenal outcomes: exploratory post hoc analyses from FIDELIO-DKD compared to reported CREDENCE results.

BACKGROUND: The nonsteroidal mineralocorticoid receptor antagonist finerenone and the sodium-glucose cotransporter-2 inhibitor (SGLT-2i) canagliflozin reduce cardiorenal risk in albuminuric patients with chronic kidney disease (CKD) and type 2 diabetes (T2D). At first glance, the results of Finerenone in Reducing Kidney Failure and Disease Progression in Diabetic Kidney Disease (FIDELIO-DKD) (ClinicalTrials.gov, NCT02540993) and Canagliflozin and Renal Events in Diabetes with Established Nephropathy Clinical Evaluation (CREDENCE) appear disparate. In FIDELIO-DKD, the primary endpoint had an 18% [95% confidence interval (CI) 7-27] relative risk reduction; in CREDENCE, the primary endpoint had a 30% (95% CI 18-41) relative risk reduction. Unlike CREDENCE, the FIDELIO-DKD trial included patients with high albuminuria but excluded patients with symptomatic heart failure with reduced ejection fraction. The primary endpoint in the FIDELIO-DKD trial was kidney specific and included a sustained decline in the estimated glomerular filtration rate (eGFR) of ≥40% from baseline. In contrast, the primary endpoint in the CREDENCE trial included a sustained decline in eGFR of ≥57% from baseline and cardiovascular (CV) death. This post hoc exploratory analysis investigated how differences in trial design-inclusion/exclusion criteria and definition of primary outcomes-influenced observed treatment effects. METHODS: Patients from FIDELIO-DKD who met the CKD inclusion criteria of the CREDENCE study (urine albumin: creatinine ratio >300-5000 mg/g and an eGFR of 30-<90 mL/min/1.73 m2 at screening) were included in this analysis. The primary endpoint was a cardiorenal composite (CV death, kidney failure, eGFR decrease of ≥57% sustained for ≥4 weeks or renal death). Patients with symptomatic heart failure with reduced ejection fraction were excluded from FIDELIO-DKD. Therefore, in a sensitivity analysis, we further adjusted for the baseline prevalence of heart failure. RESULTS: Of 4619/5674 (81.4%) patients who met the subgroup inclusion criteria, 49.6% were treated with finerenone and 50.4% received placebo. The rate of the cardiorenal composite endpoint was 43.9/1000 patient-years with finerenone compared with 59.5/1000 patient-years with placebo. The relative risk was significantly reduced by 26% with finerenone versus placebo [hazard ratio (HR) 0.74 (95% CI 0.63-0.87)]. In CREDENCE, the rate of the cardiorenal composite endpoint was 43.2/1000 patient-years with canagliflozin compared with 61.2/1000 patient-years with placebo; a 30% risk reduction was observed with canagliflozin [HR 0.70 (95% CI 0.59-0.82)]. CONCLUSIONS: This analysis highlights the pitfalls of direct comparisons between trials. When key differences in trial design are considered, FIDELIO-DKD and CREDENCE demonstrate cardiorenal benefits of a similar magnitude.

A Crohn's Disease-associated IL2RA Enhancer Variant Determines the Balance of T Cell Immunity by Regulating Responsiveness to IL-2 Signalling.

BACKGROUND AND AIMS: Differential responsiveness to interleukin [IL]-2 between effector CD4+ T cells [Teff] and regulatory T cells [Treg] is a fundamental mechanism of immunoregulation. The single nucleotide polymorphism [SNP] rs61839660, located within IL2RA [CD25], has been associated with the development of Crohn's disease [CD]. We sought to identify the T cell immune phenotype of IBD patients who carry this SNP. METHODS: Teff and Treg were isolated from individuals homozygous [TT], heterozygous [CT], or wild-type [CC] for the minor allele at rs61839660, and used for phenotyping [flow cytometry, Cytometry Time Of Flight] functional assays or T cell receptor [TCR] sequencing. Phosphorylation of signal transducer and activator of transcription 5 [STAT5] was assessed in response to IL-2, IL-7, and in the presence of basiliximab, a monoclonal antibody directed against CD25. Teff pro-inflammatory cytokine expression levels were assessed by reverse transcription quantitative polymerase chain reaction after IL-2 and/or TCR stimulation. RESULTS: Presence of the minor T allele enhances CD25 expression, leading to increased STAT5 phosphorylation and pro-inflammatory cytokine transcript expression by Teff in response to IL-2 stimulation in vitro. Teff from TT individuals demonstrate a more activated gut homing phenotype. TCR sequencing analysis suggests that TT patients may have a reduced clonal capacity to mount an optimal regulatory T cell response. CONCLUSIONS: rs61839660 regulates the responsiveness of T cells to IL-2 signalling by modulating CD25 expression. As low-dose IL-2 is being trialled as a selective Treg modulator in CD, these findings highlight the potential for adverse effects in patients with this genotype.

Finerenone Reduces New-Onset Atrial Fibrillation in Patients With Chronic Kidney Disease and Type 2 Diabetes.

BACKGROUND: Patients with chronic kidney disease (CKD) and type 2 diabetes (T2D) are at risk of atrial fibrillation or flutter (AFF) due to cardiac remodeling and kidney complications. Finerenone, a novel, selective, nonsteroidal mineralocorticoid receptor antagonist, inhibited cardiac remodeling in preclinical models. OBJECTIVES: This work aims to examine the effect of finerenone on new-onset AFF and cardiorenal effects by history of AFF in the Finerenone in Reducing Kidney Failure and Disease Progression in Diabetic Kidney Disease (FIDELIO-DKD) study. METHODS: Patients with CKD and T2D were randomized (1:1) to finerenone or placebo. Eligible patients had a urine albumin-to-creatinine ratio ≥30 to ≤5,000 mg/g, an estimated glomerular filtration rate (eGFR) ≥25 to <75 ml/min/1.73 m2 and received optimized doses of renin-angiotensin system blockade. Effect on new-onset AFF was evaluated as a pre-specified outcome adjudicated by an independent cardiologist committee. The primary composite outcome (time to first onset of kidney failure, a sustained decrease of ≥40% in eGFR from baseline, or death from renal causes) and key secondary outcome (time to first onset of cardiovascular death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for heart failure) were analyzed by history of AFF. RESULTS: Of 5,674 patients, 461 (8.1%) had a history of AFF. New-onset AFF occurred in 82 (3.2%) patients on finerenone and 117 (4.5%) patients on placebo (hazard ratio: 0.71; 95% confidence interval: 0.53-0.94; p = 0.016). The effect of finerenone on primary and key secondary kidney and cardiovascular outcomes was not significantly impacted by baseline AFF (interaction p value: 0.16 and 0.85, respectively). CONCLUSIONS: In patients with CKD and T2D, finerenone reduced the risk of new-onset AFF. The risk of kidney or cardiovascular events was reduced irrespective of history of AFF at baseline. (EudraCT 2015-000990-11 [A randomized, double-blind, placebo-controlled, parallel-group, multicenter, event-driven Phase III study to investigate the efficacy and safety of finerenone, in addition to standard of care, on the progression of kidney disease in subjects with type 2 diabetes mellitus and the clinical diagnosis of diabetic kidney disease]; Efficacy and Safety of Finerenone in Subjects With Type 2 Diabetes Mellitus and Diabetic Kidney Disease [FIDELIO-DKD]; NCT02540993).

Outcomes and costs analysis of Externalized PyeloUreteral versus internal Double-J ureteral stents after paediatric laparoscopic Anderson-Hynes pyeloplasty.

BACKGROUND: The gold standard treatment for Uretero-Pelvic Junction Obstruction (UPJO) is laparoscopic dismembered pyeloplasty according to the Anderson-Hynes technique. The internal Double-J ureteral (DJ) and the Externalized PyeloUreteral (EPU) stents are usually the drainage of choice. Only a few articles have compared the clinical impact of the different drainage techniques on the perioperative morbidity and none presented a cost analysis of the incurred hospital stay. OBJECTIVE: To present the clinical outcome and financial analysis of a cohort of children who underwent a laparoscopic pyeloplasty comparing the use of the DJ versus EPU stent. STUDY DESIGN: Retrospective study of consecutives children who underwent laparoscopic Anderson-Hynes pyeloplasty in a single tertiary paediatric referral centre from January 2017 to March 2020. Patients were grouped according to the type of stent used: DJ stent vs EPU stent. RESULTS: Fifty-three laparoscopic pyeloplasties were performed on 51 patients: 27 (50.9%) had an EPU stent and 26 (49.1%) a DJ stent. There was no statistically significant difference between the two patient groups with regards to surgical time, hospital stay, stent-related complications or the need for re-do surgery. All the EPU stents were removed with an outpatient admission 8.1 days ± 3.1 after surgery while the DJ stents were removed with a cystoscopy 61.6 days ± 30.2 after surgery (p value < 0.001). On a financial analysis (Figure), the hospital costs for stent removal were significantly lower for the EPU stent group (£ 686.7 ± 263.4 vs £ 1425 ± 299.5, p value < 0.01). DISCUSSION: Both drainage methods have some disadvantages. Possible complications associated with DJ stents include migration and artificial vesicoureteral reflux which may lead to higher incidence of Urinary Tract Infections. Possible disadvantages of the EPU stent insertion are related to the damage of the renal parenchyma and to the risk of developing skin site infections and urinary leaks. However, in our series the EPU stent has not been associated with a higher incidence of bleeding, leakage or discomfort. In addition to clinical considerations, there is a financial implication to be considered. With this regard, the EPU stent was associated with a significant reduction in the incurred hospital costs. CONCLUSIONS: The use of DJ and EPU stents is equivalent in regards of overall complications and success rates. DJ and EPU stents provided comparable success and complication rates, however the latter avoids the need of an additional general anaesthesia and reduces the overall incurred hospital costs.

An update on the roles of immune system-derived microRNAs in cardiovascular diseases.

Cardiovascular diseases (CVD) are a leading cause of human death worldwide. Over the past two decades, the emerging field of cardioimmunology has demonstrated how cells of the immune system play vital roles in the pathogenesis of CVD. MicroRNAs (miRNAs) are critical regulators of cellular identity and function. Cell-intrinsic, as well as cell-extrinsic, roles of immune and inflammatory cell-derived miRNAs have been, and continue to be, extensively studied. Several 'immuno-miRNAs' appear to be specifically expressed or demonstrate greatly enriched expression within leucocytes. Identification of miRNAs as critical regulators of immune system signalling pathways has posed the question of whether and how targeting these molecules therapeutically, may afford opportunities for disease treatment and/or management. As the field of cardioimmunology rapidly continues to advance, this review discusses findings from recent human and murine studies which contribute to our understanding of how leucocytes of innate and adaptive immunity are regulated-and may also regulate other cell types, via the actions of the miRNAs they express, in the context of CVD. Finally, we focus on available information regarding miRNA regulation of regulatory T cells and argue that targeted manipulation of miRNA regulated pathways in these cells may hold therapeutic promise for the treatment of CVD and associated risk factors.

microRNA-142-mediated repression of phosphodiesterase 3B critically regulates peripheral immune tolerance.

Tregs play a fundamental role in immune tolerance via control of self-reactive effector T cells (Teffs). This function is dependent on maintenance of a high intracellular cAMP concentration. A number of microRNAs are implicated in the maintenance of Tregs. In this study, we demonstrate that peripheral immune tolerance is critically dependent on posttranscriptional repression of the cAMP-hydrolyzing enzyme phosphodiesterase-3b (Pde3b) by microRNA-142-5p (miR-142-5p). In this manner, miR-142-5p acts as an immunometabolic regulator of intracellular cAMP, controlling Treg suppressive function. Mir142 was associated with a super enhancer bound by the Treg lineage-determining transcription factor forkhead box P3 (FOXP3), and Treg-specific deletion of miR-142 in mice (TregΔ142) resulted in spontaneous, lethal, multisystem autoimmunity, despite preserved numbers of phenotypically normal Tregs. Pharmacological inhibition and genetic ablation of PDE3B prevented autoimmune disease and reversed the impaired suppressive function of Tregs in TregΔ142 animals. These findings reveal a critical molecular switch, specifying Treg function through the modulation of a highly conserved, cell-intrinsic metabolic pathway. Modulation of this pathway has direct relevance to the pathogenesis and treatment of autoimmunity and cancer.

The Helminth-Derived Immunomodulator AvCystatin Reduces Virus Enhanced Inflammation by Induction of Regulatory IL-10+ T Cells.

Respiratory Syncytial Virus (RSV) is a major pathogen causing low respiratory tract disease (bronchiolitis), primarily in infants. Helminthic infections may alter host immune responses to both helminths and to unrelated immune triggers. For example, we have previously shown that filarial cystatin (AvCystatin/Av17) ameliorates allergic airway inflammation. However, helminthic immunomodulators have so far not been tested in virus-induced disease. We now report that AvCystatin prevents Th2-based immunopathology in vaccine-enhanced RSV lung inflammation, a murine model for bronchiolitis. AvCystatin ablated eosinophil influx, reducing both weight loss and neutrophil recruitment without impairing anti-viral immune responses. AvCystatin also protected mice from excessive inflammation following primary RSV infection, significantly reducing neutrophil influx and cytokine production in the airways. Interestingly, we found that AvCystatin induced an influx of CD4+ FoxP3+ interleukin-10-producing T cells in the airway and lungs, correlating with immunoprotection, and the corresponding cells could also be induced by adoptive transfer of AvCystatin-primed F4/80+ macrophages. Thus, AvCystatin ameliorates enhanced RSV pathology without increasing susceptibility to, or persistence of, viral infection and warrants further investigation as a possible therapy for virus-induced airway disease.

Surfactant Protein-D Is Essential for Immunity to Helminth Infection.

Pulmonary epithelial cell responses can enhance type 2 immunity and contribute to control of nematode infections. An important epithelial product is the collectin Surfactant Protein D (SP-D). We found that SP-D concentrations increased in the lung following Nippostrongylus brasiliensis infection; this increase was dependent on key components of the type 2 immune response. We carried out loss and gain of function studies of SP-D to establish if SP-D was required for optimal immunity to the parasite. N. brasiliensis infection of SP-D-/- mice resulted in profound impairment of host innate immunity and ability to resolve infection. Raising pulmonary SP-D levels prior to infection enhanced parasite expulsion and type 2 immune responses, including increased numbers of IL-13 producing type 2 innate lymphoid cells (ILC2), elevated expression of markers of alternative activation by alveolar macrophages (alvM) and increased production of the type 2 cytokines IL-4 and IL-13. Adoptive transfer of alvM from SP-D-treated parasite infected mice into naïve recipients enhanced immunity to N. brasiliensis. Protection was associated with selective binding by the SP-D carbohydrate recognition domain (CRD) to L4 parasites to enhance their killing by alvM. These findings are the first demonstration that the collectin SP-D is an essential component of host innate immunity to helminths.

IgG4 subclass antibodies impair antitumor immunity in melanoma.

Host-induced antibodies and their contributions to cancer inflammation are largely unexplored. IgG4 subclass antibodies are present in IL-10-driven Th2 immune responses in some inflammatory conditions. Since Th2-biased inflammation is a hallmark of tumor microenvironments, we investigated the presence and functional implications of IgG4 in malignant melanoma. Consistent with Th2 inflammation, CD22+ B cells and IgG4(+)-infiltrating cells accumulated in tumors, and IL-10, IL-4, and tumor-reactive IgG4 were expressed in situ. When compared with B cells from patient lymph nodes and blood, tumor-associated B cells were polarized to produce IgG4. Secreted B cells increased VEGF and IgG4, and tumor cells enhanced IL-10 secretion in cocultures. Unlike IgG1, an engineered tumor antigen-specific IgG4 was ineffective in triggering effector cell-mediated tumor killing in vitro. Antigen-specific and nonspecific IgG4 inhibited IgG1-mediated tumoricidal functions. IgG4 blockade was mediated through reduction of FcγRI activation. Additionally, IgG4 significantly impaired the potency of tumoricidal IgG1 in a human melanoma xenograft mouse model. Furthermore, serum IgG4 was inversely correlated with patient survival. These findings suggest that IgG4 promoted by tumor-induced Th2-biased inflammation may restrict effector cell functions against tumors, providing a previously unexplored aspect of tumor-induced immune escape and a basis for biomarker development and patient-specific therapeutic approaches.

A novel role of the lumican core protein in bacterial lipopolysaccharide-induced innate immune response.

Lumican is an extracellular matrix protein modified as a proteoglycan in some tissues. The core protein with leucine-rich repeats, characteristic of the leucine-rich-repeat superfamily, binds collagen fibrils and regulates its structure. In addition, we believe that lumican sequestered in the pericellular matrix interacts with cell surface proteins for specific cellular functions. Here we show that bacterial lipopolysaccharide sensing by the Toll-like receptor 4 signaling pathway and innate immune response is regulated by lumican. Primary cultures of lumican-deficient (Lum(-/-)) macrophages show impaired innate immune response to lipopolysaccharides with lower induction of tumor necrosis factor alpha (TNFalpha) and interleukin-6. Macrophage response to other pathogen-associated molecular patterns is not adversely affected by lumican deficiency, suggesting a specific role for the lumican core protein in the Toll-like receptor 4 pathway. An exogenous recombinant lumican core protein increases lipopolysaccharide-mediated TNFalpha induction and partially rescues innate immune response in Lum(-/-) macrophages. We further show that the core protein binds lipopolysaccharide. Immunoprecipitation of lumican from peritoneal lavage co-precipitates CD14, a cell surface lipopolysaccharide-binding protein that is involved in its presentation to Toll-like receptor 4. The Lum(-/-) mice are hypo-responsive to lipopolysaccharide-induced septic shock, with poor induction of pro-inflammatory cytokines, TNFalpha, and interleukins 1beta and 6 in the serum. Taken together, the data indicates a novel role for lumican in the presentation of bacterial lipopolysaccharide to CD14 and host response to this bacterial endotoxin.

Lumican regulates corneal inflammatory responses by modulating Fas-Fas ligand signaling.

PURPOSE: The authors have previously shown that apoptosis of stromal cells is downregulated in the lumican-null mouse and that this may be due to disruption of Fas-Fas ligand (FasL) signaling. The present study was undertaken to investigate the role of lumican in regulating Fas and its impact on inflammation and healing of corneal injuries. METHODS: Apoptosis was determined by measuring caspase-3/7 activity in corneal extracts. Protein and RNA levels of Fas were estimated by immunoblot analysis and RT-PCR, respectively. Circular and incisional stromal wounds were exposed to Pseudomonas aeruginosa LPS, and healing was assessed by (1) observing wound closure with fluorescence and bright-field microscopy, (2) histology to quantify inflammatory infiltrates by immunostaining for macrophages (F4/80) and neutrophils (NIMP-R14), (3) measuring myeloperoxidase (MPO) levels by ELISA to quantify neutrophils, and (4) measuring proinflammatory cytokines by ELISA. RESULTS: Lum-/- -injured corneas showed significantly lower caspase-3/7 activity (apoptosis). Lum-/- -wounded corneas showed delayed healing, reduced recruitment of macrophages and neutrophils, lower MPO levels, and no induction of the proinflammatory cytokines TNFalpha and IL1beta. The Fas protein level, before and after wounding, was dramatically lower in Lum-/- - compared with Lum+/+-injured cornea. However, Fas mRNA levels were comparable in both genotypes, suggesting regulation of Fas at the protein level. Moreover, a solid-state binding assay and coimmunoprecipitation of FasL and lumican suggested binding of FasL to lumican. CONCLUSIONS: The data suggest that lumican binds FasL and facilitates induction of Fas. Poor signaling through Fas-FasL in lumican deficiency leads to impaired induction of inflammatory cytokines and corneal healing.

Microarray studies reveal macrophage-like function of stromal keratocytes in the cornea.

PURPOSE: To elucidate biological processes underlying the keratocyte, fibroblast, and myofibroblast phenotypes of corneal stromal cells, the gene expression patterns of these primary cultures from mouse cornea were compared with those of the adult and 10-day postnatal mouse cornea. METHODS: Murine Genome_U74Av2 arrays (Affymetrix Inc., Santa Clara, CA) were used to elucidate gene expression patterns of adult and postnatal day-10 corneal stroma, keratocytes, fibroblasts, and myofibroblasts. RESULTS: Mobilization of stromal cells by culturing led to a wound-healing cascade in which specific extracellular matrix and cornea-transparency-related genes were turned off, and a repertoire of macrophage genes were switched on. Thus, novel transparency-related crystallins detected in the corneal gene expression patterns were downregulated in culture, whereas macrophage genes, mannose receptor type-1, Cd68, serum amyloid-A3, chemokine ligands (Ccl2, Ccl7, Ccl9), lipocalin-2, and matrix metalloproteinase-3 and -12 of innate immunity were induced in primary keratocyte cultures. Fibroblasts expressed the growth-related genes lymphocyte antigen 6 complex locus-A and preprokephalin-1, and myofibroblasts expressed annexin-A8, WNT1-inducible signaling pathway protein-1, arginosuccinate synthetase-1, and procollagen XI of late-stage wound healing. CONCLUSIONS: The emergent biological process suggests a dual role for resident stromal keratocytes in the avascular cornea: one of cornea maintenance, which involves synthesis of proteins related to the extracellular matrix and corneal transparency, and a second of barrier protection macrophage functions, which are switched on during corneal infection and injury.

Lumican suppresses cell proliferation and aids Fas-Fas ligand mediated apoptosis: implications in the cornea.

Lumican, an extracellular matrix (ECM) keratan sulfate proteoglycan, binds fibrillar collagen and limits collagen fibril diameter in the cornea, skin and tendon. Lumican-deficient mice (Lum(-/-)) develop abnormally thick collagen fibrils, translucent corneas and fragilities of the skin and the tendon. In addition to modulating interstitial ECM structure, here we hypothesized that lumican regulates proliferation and apoptosis of cells residing in the interstitium. Corneal and embryonic fibroblasts from the Lum(-/-) mouse show increased growth in culture. Lum(-/-) mouse embryonic fibroblasts (MEF), compared to their wild type counterparts, display increased rates of proliferation and decreased apoptosis. Ectopic expression of lumican in Lum(-/-) MEF or exogenous recombinant lumican in the culture medium reduces proliferation to rates seen in the Lum(+/+) MEF. We further investigated the implications of lumican's proliferation and apoptosis regulatory role in the cornea where lumican is a major component of the stromal matrix. Stromal keratocytes undergo proliferation and apoptosis during corneal maturation and in the healing of injured cornea. The Lum(-/-) mouse shows increased proliferation and decreased apoptosis of stromal keratocytes during postnatal corneal maturation at the 10-day age. Apoptosis is also significantly down regulated in Lum(-/-) vis-à-vis Lum(+/+) mice during stromal wound healing in the adult 6-week age. Lumican appears to regulate these cellular functions by modulating specific cell growth and apoptosis mediators. Thus, Lum(-/-) MEF have decreased p21(WAF1/CIP1), a universal inhibitor of cyclin-dependent kinases and a consequent increase in cyclins A, D1 and E. Furthermore, the tumor suppressor p53, an upstream regulator of p21 is down regulated in the MEF and the cornea of Lum(-/-) mice. The evidence suggests regulation of p21 by lumican in a p53-dependent way. The MEF and the cornea of Lum(-/-) mice also show a dramatic decrease in Fas (CD95). The Lum(-/-) MEF fail to induce Fas upon treatment with Fas ligand. Fas-Fas ligand interaction is an initiating event in apoptosis and its disruption in lumican-deficiency may partly explain the observed decrease in apoptosis. Fas-Fas ligand mediated apoptosis is critical for maintaining the immune privileged status of the cornea, which implies a new and exciting role for lumican in the cornea.