Platelets are relevant mediators of renal injury induced by primary endothelial lesions

Prognostic significance of mean platelet volume to platelet count ratio in pediatric patients with acute kidney injury

BACKGROUND

Mean platelet volume (MPV), which is regarded as a marker of thrombocyte function and activation, is related to increased morbidity and mortality. In critically ill patients, the ratio of MPV to platelets can independently predict adverse outcomes. This study aimed to investigate the prognostic value of the mean platelet volume/platelet count ratio (MPR) for mortality in children with acute kidney injury (AKI).

METHODS

In this retrospective study, patients hospitalized in the pediatric intensive care unit (PICU) between March 2020 and June 2022 were evaluated. Patients between 1 month and 18 years of age with AKI were enrolled. Clinical and laboratory data were compared between survivors and non-survivors. The MPR ratio was calculated on the first and third days of admission to the intensive care unit. A multiple logistic regression analysis was used to determine the association between MPR and mortality. ROC curves were used for the prediction performance of the logistic regression models and cut-off values of the thrombocyte indices.

RESULTS

Sixty-three children with AKI were included in the study. The total mortality rate was 34.9% (n=22). MPR ratios were significantly higher in the non-survivors at admission (p=0.042) and at the 72nd hour (p=0.003). In the multiple logistic regression analysis, thrombocyte counts and MPR72h ratio were found to be independent risk parameters for adverse outcomes in children with AKI.

CONCLUSIONS

MPR is an inexpensive and practical marker that may predict the outcome of children with AKI.

Pediatric Mesangial Proliferative Glomerulonephritis Has Increased the Platelet Thrombus Formation Potentials under High-Shear Flow Condition

INTRODUCTION

Blood coagulation is associated with glomerulonephritis (GN) pathophysiology. Using whole-blood-based rotational thromboelastometry, we recently reported that the degree of hypercoagulability in pediatric patients with immunoglobulin A nephropathy (IgAN), a GN, might be associated with pathological severity. To further clarify the coagulation status of mesangial proliferative GN (MesPGN), we assessed the platelet thrombus formation (PTF) under high-shear flow using a microchip-based flow chamber system (T-TAS®).

METHODS

Thirty-four pediatric patients definitively diagnosed with MesPGN by renal biopsy at Nara Medical University Hospital between 2015 and 2022 were enrolled, and 29 patients (case group; median age, 8.0 years) were assessed. Microchips coated with collagen (PL-chip) were used to assess PTF at high-shear in whole blood. The times to increase by 10 and 30 kPa (T10 and T30) from baseline were calculated and compared with those of the pediatric controls. Changes in the parameters during the treatment course and the relationship between pathological severity and the parameters were evaluated.

RESULTS

T10 and T30 parameters in the PL-chip were significantly shorter, and the area under the curves were greater in the case group than those in the control group (both p < 0.05). Each parameter was enhanced during the 3-week treatment but improved after the end of treatment. No significant relationship was observed between pathological severity and these parameters. Little PTF difference was observed between IgAN and Henoch-Schönlein purpura nephritis.

CONCLUSIONS

Pediatric MesPGN increased the potential for PTF under high-shear flow conditions.

Implication of platelets and complement C3 as link between innate immunity and tubulointerstitial injury in renal vasculitis with MPO-ANCA seropositivity

Introduction

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a potentially life-threatening systemic small-vessel vasculitis that is characterized by pauci-immune glomerulonephritis, depicting in turn a major denominator of AAV mortality. It is well established that AAV patients feature an increased risk of developing thrombotic events, and platelets are activated in AAV patients being triggered by the alternative complement pathway. Platelets guard vessels integrity and initiate thrombus formation in response to endothelial damage, further constituting a triangular interconnection with the activation of neutrophils and the complement system. We here aimed to systematically assess the relevance of platelet counts and systemic complement system activation regarding distinct histopathological lesions in ANCA-associated renal vasculitis.

Methods

A cohort of 53 biopsy-proven cases of ANCA-associated renal vasculitis were retrospectively enrolled in a single-center observational study. Univariate and multivariate regression analysis was performed to identify parameters associated with platelet counts in ANCA-associated renal vasculitis compared to disease controls. Finally, the relevance of platelets for disease course and recovery was assessed by survival analysis.

Results

Lower platelet counts correlated with markers of kidney injury including eGFR loss (p=0.0004) and lower complement C3 levels (p=0.0037). Multivariate and subgroup analysis revealed that this association was only present in the subgroup with MPO-ANCA seropositivity (eGFR loss: p=0.0009, lower C3: p=0.0032). While lower platelet counts correlated with kidney injury in the PR3-ANCA subgroup (eGFR loss: p=0.0272), we did not observe an independent association with complement C3 levels (p=0.4497). Independent of any glomerular lesion, lower platelet counts correlated with interstitial fibrosis (p=0.0313), tubular atrophy (p=0.0073), and tubulitis in areas of interstitial fibrosis and tubular atrophy (p=0.0033). Finally, we observed significant differences with increased requirement of kidney replacement therapy (KRT) or death in the subgroup below median platelet counts (HR: 4.1, 95% CI: 1.6-10, p=0.0047), associated with a lower probability of discharge and prolonged hospitalization in this subgroup (HR: 0.5, 95% CI: 0.3-0.9, p=0.0113).

Conclusion

Based on our observation that an association between platelets and complement system activation is only observed in the MPO-ANCA subgroup, this could implicate that platelets and complement C3 link innate immunity to tubulointerstitial injury in the presence of MPO-ANCA autoantibodies.

Improved placental vascular repair in a rat preeclampsia model by implantation of endothelial progenitor cells treated with platelet microparticles

Objective: To detect the role of endothelial progenitor cells (EPCs) treated with platelet microparticles (PMPs) in preeclampsia. Methods: EPCs treated with/without PMPs were labeled and injected to PE rats. The differentiation of EPCs, the change of endothelial nitric oxide synthase (eNOS), blood pressure and proteinuria were measured. The blood pressure and proteinuria increased in each of PE groups, and were improved by EPCs which was strengthened by PMPs. Transplantation of EPCs increased placental angiogenesis. The trend of change of NO was the same as blood pressure. Conclusion: Transplantation of EPCs treated with PMPs improved blood pressure and proteinuria more effectively.

Misunderstandings Between Platelets and Neutrophils Build in Chronic Inflammation

Regulated hemostasis, inflammation and innate immunity entail extensive interactions between platelets and neutrophils. Under physiological conditions, vascular inflammation offers a template for the establishment of effective intravascular immunity, with platelets providing neutrophils with an array of signals that increase their activation threshold, thus limiting collateral damage to tissues and promoting termination of the inflammatory response. By contrast, persistent systemic inflammation as observed in immune-mediated diseases, such as systemic vasculitides, systemic sclerosis, systemic lupus erythematosus or rheumatoid arthritis is characterized by platelet and neutrophil reciprocal activation, which ultimately culminates in the generation of thrombo-inflammatory lesions, fostering vascular injury and organ damage. Here, we discuss recent evidence regarding the multifaceted aspects of platelet-neutrophil interactions from bone marrow precursors to shed microparticles. Moreover, we analyse shared and disease-specific events due to an aberrant deployment of these interactions in human diseases. To restore communications between the pillars of the immune-hemostatic continuum constitutes a fascinating challenge for the near future.

Cell-derived microparticles and von Willebrand factor in Brazilian renal transplant recipients

AIM

This study was aimed at investigating platelet-derived microparticles (PMP), endothelium cell-derived microparticles (EMP) and von Willebrand factor (VWF) according to renal function and time post-transplant. We found this study relevant because unusual biomarkers seem to be a promising tool to evaluate chronic renal disease and post-transplant monitoring.

METHODS

Ninety-one renal transplant recipients (RTx) were allocated into groups according to creatinine plasma levels (C1 < 1.4 and C2 ≥ 1.4 mg/dL), estimated glomerular filtration rates (R1 < 60 and R2 ≥ 60 mL/min per 1.73 m² ) and time post-transplant (T1: 3-24; T2: 25-60; T3: 61-120; and T4 > 120 months). EMP and PMP levels were assessed by flow cytometry and VWF levels were evaluated by enzyme-linked immunosorbent assay.

RESULTS

Platelet-derived microparticle levels were higher in C1 group compared with C2 (P = 0.00). According to diameter, small PMP and EMP (≤0.7 μm) were also higher in C1 group, all values of P less than 0.05. T1 and T2 groups have shown high EMP levels and a predominance of big microparticle (>0.7 μm) compared with T4 group, all values of P less than 0.05. Higher VWF levels were observed among RTx with creatinine ≥1.4 mg/dL compared with other RTx, P = 0.01.

CONCLUSION

The results showed that PMP, EMP and VWF are promising markers to evaluate endothelial function in RTx. These biomarkers could play a major role in monitoring patients after renal transplant.

The role of platelets in acute kidney injury

Acute kidney injury (AKI), a major public health problem associated with high mortality and increased risk of progression towards end-stage renal disease, is characterized by the activation of intra-renal haemostatic and inflammatory processes. Platelets, which are present in high numbers in the circulation and can rapidly release a broad spectrum of bioactive mediators, are important acute modulators of inflammation and haemostasis, as they are the first cells to arrive at sites of acute injury, where they interact with endothelial cells and leukocytes. Diminished control of platelet reactivity by endothelial cells and/or an increased release of platelet-activating mediators can lead to uncontrolled platelet activation in AKI. As increased platelet sequestration and increased expression levels of the markers P-selectin, thromboxane A₂, CC-chemokine ligand 5 and platelet factor 4 on platelets have been reported in kidneys following AKI, platelet activation likely plays a part in AKI pathology. Results from animal models and some clinical studies highlight the potential of antiplatelet therapies in the preservation of renal function in the context of AKI, but as current strategies also affect other cell types and non-platelet-derived mediators, additional studies are required to further elucidate the extent of platelet contribution to the pathology of AKI and to determine the best therapeutic approach by which to specifically target related pathogenic pathways.

Impact of KDIGO-Defined Acute Kidney Injury on Mortality after Percutaneous Coronary Intervention for Acute Myocardial Infarction

BACKGROUND

There are limited data regarding the incidence and long-term impact of acute kidney injury (AKI) according to the KDIGO guidelines on the outcome in patients with myocardial infarction (MI) treated with percutaneous coronary intervention (PCI). The aim of the study was to evaluate the prevalence of AKI, as classified by the KDIGO criteria, and its association with long-term mortality.

METHODS

Data from 5,859 MI patients undergoing PCI at our institution were analyzed. We compared the group without and with AKI according to the KDIGO criteria in relation to long-term mortality.

RESULTS

AKI was documented in 499 (8.5%) patients. AKI stage 1 occurred in 6.2% of patients, AKI stage 2 in 0.9% of patients, and AKI stage 3 in 1.5% of patients. Patients with AKI had a higher long-term mortality (57.3 vs. 20.6%; p < 0.0001). The mortality was 50.3% in AKI stage 1, 56.9% in AKI stage 2, and 87.2% in AKI stage 3. The hazard ratios for all-cause mortality for AKI stages 1-3 were 1.77, 1.85, and 6.30 compared to patients with no AKI. Cardiogenic shock, bleeding, heart failure, age, renal dysfunction, diabetes, hyperlipidemia, ST-elevation MI, contrast volume/glomerular filtration ratio, P2Y12 receptor antagonists, and radial access were associated with the development of AKI.

CONCLUSION

A slight increase in serum creatinine was associated with a progressive increase in long-term mortality in patients with AKI according to the KDIGO definition.

Extracellular vesicles and microvascular pathology: Decoding the active dialogue

Extracellular vesicles (EV) are a heterogeneous collection of membrane-surrounded structures released from all studied cells, under both physiological and pathological conditions. These nano-size vesicles carry complex cargoes including different classes of proteins, lipids and nucleic acids and are known to act as a communication and signalling vesicles in various cellular process. In addition to their role in development and progression of pathological disorders which make them potentially great biomarkers, EV have beneficial effects, as they take part in homeostasis. In this review we have analysed the evidence for the role of microvesicles and exosomes secreted from other cells on microvascular endothelium (EV uptake) as well as the role of endothelial-derived vesicles on their neighbouring and distant cells (EV release).

Progenitor Renin Lineage Cells are not involved in the regeneration of glomerular endothelial cells during experimental renal thrombotic microangiopathy

Endothelial cells (EC) frequently undergo primary or secondary injury during kidney disease such as thrombotic microangiopathy or glomerulonephritis. Renin Lineage Cells (RLCs) serve as a progenitor cell niche after glomerular damage in the adult kidney. However, it is not clear whether RLCs also contribute to endothelial replenishment in the glomerulus following endothelial injury. Therefore, we investigated the role of RLCs as a potential progenitor niche for glomerular endothelial regeneration. We used an inducible tet-on triple-transgenic reporter strain mRen-rtTAm2/LC1/LacZ to pulse-label the renin-producing RLCs in adult mice. Unilateral kidney EC damage (EC model) was induced by renal artery perfusion with concanavalin/anti-concanavalin. In this model glomerular EC injury and depletion developed within 1 day while regeneration occurred after 7 days. LacZ-labelled RLCs were restricted to the juxtaglomerular compartment of the afferent arterioles at baseline conditions. In contrast, during the regenerative phase of the EC model (day 7) a subset of LacZ-tagged RLCs migrated to the glomerular tuft. Intraglomerular RLCs did not express renin anymore and did not stain for glomerular endothelial or podocyte cell markers, but for the mesangial cell markers α8-integrin and PDGFRβ. Accordingly, we found pronounced mesangial cell damage parallel to the endothelial injury induced by the EC model. These results demonstrated that in our EC model RLCs are not involved in endothelial regeneration. Rather, recruitment of RLCs seems to be specific for the repair of the concomitantly damaged mesangium.

Effect of Platelet-derived P-selectin on Neutrophil Recruitment in a Mouse Model of Sepsis-induced Acute Kidney Injury

Background:

Acute kidney injury (AKI) is a severe disease in critically ill patients. Neutrophil infiltration into kidney was associated with the development of AKI, and P-selectin may be involved in the process of neutrophil recruitment in kidney. This study aimed to explore the potential effect of platelet-derived P-selectin on neutrophil recruitment in a mouse model of sepsis-induced AKI.

Methods:

A total of 30 C57BL/6 male mice were divided into five groups (n = 6 in each): sham group, sepsis group, anti-Ly6G group, anti-P-selectin group, and platelet depletion group. Sepsis was induced by cecal ligation and puncture. Serum creatinine concentration and platelet activity were measured by biochemical detector and flow cytometry, respectively. Histological and pathological features were analyzed using hematoxylin-eosin (H&E) and immunohistochemistry (IHC) staining, respectively. Myeloperoxidase (MPO) activity was detected with MPO assay. Unpaired t-test was used for data analysis.

Results:

Serum creatinine increased significantly in septic group compared to sham group (2.68 ± 0.27 mg/dl vs. 0.82 ± 0.19 mg/dl, t = 12.06, P = 0.0000) but attenuated in antibodies-treated animals compared to septic group (anti-Ly6G: 1.62 ± 0.30 mg/dl vs. 2.68 ± 0.27 mg/dl, t = 5.76, P = 0.0004; anti-P-selectin: 1.76 ± 0.31 mg/dl vs. 2.68 ± 0.27 mg/dl, t = 4.92, P = 0.0012; and platelet depletion: 1.93 ± 0.29 mg/dl vs. 2.68 ± 0.27 mg/dl, t = 4.14, P = 0.0032). Platelet amount significantly decreased compared to sham group (658.20 ± 60.64 × 10⁹/L vs. 822.00 ± 48.60 × 10⁹/L, t = 4.71, P = 0.0015) in septic mice, especially in platelet depletion group (240.80 ± 44.98 × 10⁹/L vs. 822.00 ± 48.60 × 10⁹/L, t = 19.63, P = 0.0000). P-selectin activity was significantly increased in septic group compared to sham group (16.54 ± 1.60% vs. 1.90 ± 0.29%, t = 15.64, P = 0.0000) but decreased significantly in platelet depletion group compared to septic group (3.62 ± 0.68% vs. 16.54 ± 1.60%, t = 12.89, P = 0.0002). IHC analysis shown that neutrophil infiltration increased in septic mice compared to sham group (36.67 ± 3.79% vs. 9.17 ± 1.61%, t = 11.58, P = 0.0003) and function-blocked groups (anti-Ly6G: 36.67 ± 3.79% vs. 15.33 ± 1.53%, t = 9.05, P = 0.0008; anti-P-selectin: 36.67 ± 3.79% vs. 21.33 ± 1.53%, t = 6.51, P = 0.0029; and platelet depletion: 36.67 ± 3.79% vs. 23.33 ± 3.06%, t = 4.75, P = 0.0090). MPO increased significantly in septic group compared to control (49.73 ± 1.83 ng/mg prot vs. 13.04 ± 2.16 ng/mg prot, t = 19.03, P = 0.0000) but decreased in function-blocked groups compared to septic group (anti-Ly6G: 26.52 ± 3.86 ng/mg prot vs. 49.73 ± 1.83 ng/mg prot, t = 9.59, P = 0.0000; anti-P-selectin: 33.06 ± 6.75 ng/mg prot vs. 49.73 ± 1.83 ng/mg prot, t = 4.85, P = 0.0013; and platelet depletion: 33.37 ± 2.25 ng/mg prot vs. 49.73 ± 1.83 ng/mg prot, t = 5.33, P = 0.0007).

Conclusion:

Platelets-derived P-selectin may be involved in the development of septic AKI through inducing neutrophil infiltration into kidney.

Combination of Mean Platelet Volume/Platelet Count Ratio and the APACHE II Score Better Predicts the Short-Term Outcome in Patients with Acute Kidney Injury Receiving Continuous Renal Replacement Therapy

BACKGROUND/AIMS

Both the Acute physiology and Chronic Health Evaluation (APACHE II) score and mean platelet volume/platelet count Ratio (MPR) can independently predict adverse outcomes in critically ill patients. This study was aimed to investigate whether the combination of them could have a better performance in predicting prognosis of patients with acute kidney injury (AKI) who received continuous renal replacement therapy (CRRT).

METHODS

Two hundred twenty-three patients with AKI who underwent CRRT between January 2009 and December 2014 in a Chinese university hospital were enrolled. They were divided into survivals group and non-survivals group based on the situation at discharge. Receiver Operating Characteristic (ROC) curve was used for MPR and APACHE II score, and to determine the optimal cut-off value of MPR for in-hospital mortality. Factors associated with mortality were identified by univariate and multivariate logistic regression analysis.

RESULTS

The mean age of the patients was 61.4 years, and the overall in-hospital mortality was 48.4%. Acute cardiorenal syndrome (ACRS) was the most common cause of AKI. The optimal cut-off value of MPR for mortality was 0.099 with an area under the ROC curve (AUC) of 0.636. The AUC increased to 0.851 with the addition of the APACHE II score. The mortality of patients with of MPR > 0.099 was 56.4%, which was significantly higher than that of the control group with of ≤ 0.099 (39.6%, P= 0.012). Logistic regression analysis showed that average number of organ failure (OR = 2.372), APACHE II score (OR = 1.187), age (OR = 1.028) and vasopressors administration (OR = 38.130) were significantly associated with poor prognosis.

CONCLUSION

Severity of illness was significantly associated with prognosis of patients with AKI. The combination of MPR and APACHE II score may be helpful in predicting the short-term outcome of AKI.

The protective effect of ticagrelor on renal function in a mouse model of sepsis-induced acute kidney injury

Platelets are traditionally considered to be essential components of primary hemostasis. Recent investigations have revealed that platelets can be activated in patients with sepsis and are implicated in the development of sepsis and sepsis-induced-acute kidney injury (SAKI). In the present study, ticagrelor was used to induce a mouse model of SAKI by cecal ligation and puncture. It was found that ticagrelor could inhibit platelet activity, decrease the levels of interleukin-1β and serum creatinine, reduce infiltration of neutrophils in renal tissue, and attenuate cell apoptosis in the kidney. The results suggested that ticagrelor could protect renal function by inhibiting inflammation, recruitment of neutrophils into the kidney, and cell apoptosis in renal tissue. Thus, the findings might provide new strategies for preventing SAKI.

Engineered Sialylation of Pathogenic Antibodies In Vivo Attenuates Autoimmune Disease

Self-reactive IgGs contribute to the pathology of autoimmune diseases, including systemic lupus erythematosus and rheumatoid arthritis. Paradoxically, IgGs are used to treat inflammatory diseases in the form of high-dose intravenous immunoglobulin (IVIG). Distinct glycoforms on the IgG crystallizable fragment (Fc) dictate these divergent functions. IgG anti-inflammatory activity is attributed to sialylation of the Fc glycan. We therefore sought to convert endogenous IgG to anti-inflammatory mediators in vivo by engineering solubilized glycosyltransferases that attach galactose or sialic acid. When both enzymes were administered in a prophylactic or therapeutic fashion, autoimmune inflammation was markedly attenuated in vivo. The enzymes worked through a similar pathway to IVIG, requiring DC-SIGN, STAT6 signaling, and FcγRIIB. Importantly, sialylation was highly specific to pathogenic IgG at the site of inflammation, driven by local platelet release of nucleotide-sugar donors. These results underscore the therapeutic potential of glycoengineering in vivo.

Blood platelets and sepsis pathophysiology: A new therapeutic prospect in critically [corrected] ill patients?

Beyond haemostasis, platelets have emerged as versatile effectors of the immune response. The contribution of platelets in inflammation, tissue integrity and defence against infections has considerably widened the spectrum of their role in health and disease. Here, we propose a narrative review that first describes these new platelet attributes. We then examine their relevance to microcirculatory alterations in multi-organ dysfunction, a major sepsis complication. Rapid progresses that are made on the knowledge of novel platelet functions should improve the understanding of thrombocytopenia, a common condition and a predictor of adverse outcome in sepsis, and may provide potential avenues for management and therapy.

Post Hoc Analyses of Randomized Clinical Trial for the Effect of Clopidogrel Added to Aspirin on Kidney Function

BACKGROUND AND OBJECTIVES

Despite the high burden of CKD, few specific therapies are available that can halt disease progression. In animal models, clopidogrel has emerged as a potential therapy to preserve kidney function. The effect of clopidogrel on kidney function in humans has not been established.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The Secondary Prevention of Small Subcortical Strokes Study randomized participants with prior lacunar stroke to treatment with aspirin or aspirin plus clopidogrel. We compared annual eGFR decline and incidence of rapid eGFR decline (≥30% from baseline) using generalized estimating equations and interval-censored proportional hazards regression, respectively. We also stratified our analyses by baseline eGFR, systolic BP target, and time after randomization.

RESULTS

At randomization, median age was 62 (interquartile range, 55-71) years old; 36% had a history of diabetes, 90% had hypertension, and the median eGFR was 81 (interquartile range, 65-94) ml/min per 1 m2. Persons receiving aspirin plus clopidogrel had an average annual change in kidney function of -1.39 (95% confidence interval, -1.15 to -1.62) ml/min per 1.73 m2 per year compared with -1.52 (95% confidence interval, -1.30 to -1.74) ml/min per 1.73 m2 per year among persons receiving aspirin only (P=0.42). Rapid kidney function decline occurred in 21% of participants receiving clopidogrel plus aspirin compared with 22% of participants receiving aspirin plus placebo (hazard ratio, 0.94; 95% confidence interval, 0.79 to 1.10; P=0.42). Findings did not vary by baseline eGFR, time after randomization, or systolic BP target (all P values for interaction were >0.3).

CONCLUSIONS

We found no effect of clopidogrel added to aspirin compared with aspirin alone on kidney function decline among persons with prior lacunar stroke.

Platelet-derived sphingosine-1-phosphate and inflammation: from basic mechanisms to clinical implications

Beyond key functions in hemostasis and thrombosis, platelets are recognized as key players of inflammation, an underlying feature of a variety of diseases. In this regard, platelets act as a circulating source of several pro- and anti-inflammatory molecules, which are secreted from their intracellular stores upon activation. Among them, mounting evidence highlights a crucial role of sphingosine-1-phosphate (S1P), a multifunctional sphingoid mediator. S1P-induced pleiotropic effects include those crucial in inflammatory processes, such as the maintenance of the endothelial barrier integrity, and leukocyte activation and recruitment at the injured site. This review outlines the peculiar features and molecular mechanisms that allow platelets for acting as a unique factory that produces and stores S1P in large quantities. A particular emphasis is placed on the autocrine and paracrine roles of S1P derived from the "inflamed" platelets, highlighting the role of its cross-talk with endothelial and blood cells involved in inflammation, and the mechanisms of its contribution to the development and progression of inflammatory diseases. Finally, potential clinical implications of platelet-derived S1P as diagnostic tool of inflammatory severity, and as therapeutic target in inflammation are discussed.