Porto-sinusoidal vascular disorder and nephrotic-range proteinuria due to venous vasculitis in Behçet's disease

Behçet's disease (BD) is an autoinflammatory disease of multifactorial and polygenic etiology, potentially involving arteries and veins of any size resulting in variable vessel vasculitis. We report a case of an Iranian male that presented with porto-sinusoidal vascular disorder due to venous vasculitis as initial manifestation of BD. Despite immunosuppression and anticoagulation, he subsequently developed severe nephrotic-range proteinuria that mimicked a primary renal disease but was completely and immediately ameliorated by stenting of the vena cava. This demonstrates that the proteinuria was caused by increased intraglomerular pressure due to venous outflow obstruction as a consequence of venous vasculitis. To our knowledge, this is the first report of massive proteinuria caused by venous obstruction of the caval vein in the context of Behçet's disease. Altogether, this case demonstrates the extensive spectrum of vascular disease in BD.

Airway smooth muscle and long-term clinical efficacy following bronchial thermoplasty in severe asthma

The mechanism of action of bronchial thermoplasty (BT) treatment for patients with severe asthma is incompletely understood. This study investigated the 2.5-year impact of BT on airway smooth muscle (ASM) mass and clinical parameters by paired data analysis in 22 patients. Our findings demonstrate the persistence of ASM mass reduction of >50% after 2.5 years. Furthermore, sustained improvement in asthma control, quality of life and exacerbation rates was found, which is in line with previous reports. An association was found between the remaining ASM and both the exacerbation rate (r=0.61, p=0.04 for desmin, r=0.85, p<0.01 for alpha smooth muscle actin (SMA)) and post-bronchodilator forced expiratory volume in 1 s predicted percentage (r=-0.69, p=0.03 for desmin, r=-0.58, p=0.08 for alpha SMA). This study provides new insight into the long-term impact of BT.

Transfusion of female blood in a rat model is associated with red blood cells entrapment in organs

Transfusion of red blood cells (RBCs) has been associated with adverse outcomes. Mechanisms may be related to donor sex and biological age of RBC. This study hypothesized that receipt of female blood is associated with decreased post-transfusion recovery (PTR) and a concomitant increased organ entrapment in rats, related to young age of donor RBCs. Donor rats underwent bloodletting to stimulate production of new, young RBCs, followed by Percoll fractionation for further enrichment of young RBCs based on their low density. Control donors did not undergo these procedures. Male rats received either a (biotinylated) standard RBC product or a product enriched for young RBCs, derived from either male or female donors. Controls received saline. Organs and blood samples were harvested after 24 hours. This study found no difference in PTR between groups, although only the group receiving young RBCs from females failed to reach a PTR of 75%. Receipt of both standard RBCs and young RBCs from females was associated with increased entrapment of donor RBCs in the lung, liver, and spleen compared to receiving blood from male donors. Soluble ICAM-1 and markers of hemolysis were higher in recipients of female blood compared to control. In conclusion, transfusing RBCs from female donors, but not from male donors, is associated with trapping of donor RBCs in organs, accompanied by endothelial activation and hemolysis.

Female sex protects against renal edema, but not lung edema, in mice with partial deletion of the endothelial barrier regulator Tie2 compared to male sex

BACKGROUND

The endothelial angiopoietin/Tie2 system is an important regulator of endothelial permeability and targeting Tie2 reduces hemorrhagic shock-induced organ edema in males. However, sexual dimorphism of the endothelium has not been taken into account. This study investigated whether there are sex-related differences in the endothelial angiopoietin/Tie2 system and edema formation.

METHODS

Adult male and female heterozygous Tie2 knockout mice (Tie2+/-) and wild-type controls (Tie2+/+) were included (n = 9 per group). Renal and pulmonary injury were determined by wet/dry weight ratio and H&E staining of tissue sections. Protein levels were studied in plasma by ELISA and pulmonary and renal mRNA expression levels by RT-qPCR.

RESULTS

In Tie2+/+ mice, females had higher circulating angiopoietin-2 (138%, p<0.05) compared to males. Gene expression of angiopoietin-1 (204%, p<0.01), angiopoietin-2 (542%, p<0.001) were higher in females compared to males in kidneys, but not in lungs. Gene expression of Tie2, Tie1 and VE-PTP were similar between males and females in both organs. Renal and pulmonary wet/dry weight ratio did not differ between Tie2+/+ females and males. Tie2+/+ females had lower circulating NGAL (41%, p<0.01) compared to males, whereas renal NGAL and KIM1 gene expression was unaffected. Interestingly, male Tie2+/- mice had 28% higher renal wet/dry weight ratio (p<0.05) compared to Tie2+/+ males, which was not observed in females nor in lungs. Partial deletion of Tie2 did not affect circulating angiopoietin-1 or angiopoietin-2, but soluble Tie2 was 44% and 53% lower in males and females, respectively, compared to Tie2+/+ mice of the same sex. Renal and pulmonary gene expression of angiopoietin-1, angiopoietin-2, estrogen receptors and other endothelial barrier regulators was comparable between Tie2+/- and Tie2+/+ mice in both sexes.

CONCLUSION

Female sex seems to protect against renal, but not pulmonary edema in heterozygous Tie2 knock-out mice. This could not be explained by sex dimorphism in the endothelial angiopoietin/Tie2 system.

Diagnosing Hirschsprung Disease in Children Younger than 6 Months of Age: Insights in Incidence of Complications of Rectal Suction Biopsy and Other Final Diagnoses

BACKGROUND

 The gold standard for diagnosing Hirschsprung disease (HD) in patients younger than 6 months is pathological examination of rectal suction biopsy (RSB). The aim of this study was to gain insight into the following: (1) complications following RSB, (2) final diagnosis of patients referred for RSB, and (3) factors associated with HD.

METHODS

 Patients suspected of HD referred for RSB at our center were analyzed retrospectively. Severity of complications of RSB was assessed using Clavien-Dindo (CD) grading. Factors associated with HD were tested using multivariate logistic regression analysis.

RESULTS

 From 2000 to 2021, 371 patients underwent RSB because of infrequent defecation, at a median age of 44 days. Three patients developed ongoing rectal bleeding (0.8%) graded CD1. Most frequent final diagnoses were: HD (n = 151, 40.7%), functional constipation (n = 113, 31%), idiopathic meconium ileus (n = 11, 3%), and food intolerance (n = 11, 3%). Associated factors for HD were male sex (odds ratio [OR], 3.19; confidence interval [CI], 1.56-6.53), presence of syndrome (OR, 7.18; CI, 1.63-31.69), younger age at time of RSB (OR, 0.98; CI, 0.85-0.98), meconium passage for more than 48 hours (OR, 3.15; CI, 1.51-6.56), distended abdomen (OR, 2.09; CI, 1.07-4.07), bilious vomiting (OR, 6.39; CI, 3.28-12.47), and failure to thrive (OR, 8.46; CI, 2.11-34.02) (model R 2 = 0.566).

CONCLUSION

 RSB is a safe procedure with few and only minor complications. In the majority of patients referred for RSB under the age of 6 months, HD was found followed by a functional cause for the defecation problems. RSB should be obtained on a low threshold in all patients under the age of 6 months with the suspicion of HD.

The effects of resuscitation with different plasma products on endothelial permeability and organ injury in a rat pneumosepsis model

BACKGROUND

Endothelial injury and permeability are a hallmark of sepsis. Initial resuscitation of septic patients with crystalloids is associated with aggravation of endothelial permeability, which may be related either to low protein content or to volume. We investigated whether initial resuscitation with different types of plasma or albumin decreases endothelial dysfunction and organ injury in a pneumosepsis rat model compared to the same volume of crystalloids.

STUDY DESIGN AND METHODS

Sprague-Dawley rats were intratracheally inoculated with Streptococcus pneumoniae. Twenty-four hours after inoculation, animals were randomized to 2 control groups and 5 intervention groups (n = 11 per group) to receive resuscitation with a fixed volume (8 mL/kg for 1 h) of either Ringer's Lactate, 5% human albumin, fresh frozen plasma derived from syngeneic donor rats (rFFP), human-derived plasma (hFFP) or human-derived solvent detergent plasma (SDP). Controls were non-resuscitated (n = 11) and healthy animals. Animals were sacrificed 5 h after start of resuscitation (T = 5). Pulmonary FITC-dextran leakage as a reflection of endothelial permeability was used as the primary outcome.

RESULTS

Inoculation with S. Pneumoniae resulted in sepsis, increased median lactate levels (1.6-2.8 mM, p < 0.01), pulmonary FITC-dextran leakage (52-134 µg mL-1, p < 0.05) and lung injury scores (0.7-6.9, p < 0.001) compared to healthy controls. Compared to animals receiving no resuscitation, animals resuscitated with rFFP had reduced pulmonary FITC leakage (134 vs 58 µg/mL, p = 0.011). However, there were no differences in any other markers of organ or endothelial injury. Resuscitation using different human plasma products or 5% albumin showed no differences in any outcome.

CONCLUSIONS

Resuscitation with plasma did not reduce endothelial and organ injury when compared to an equal resuscitation volume of crystalloids. Rat-derived FFP may decrease pulmonary leakage induced by shock.

A Graphical Overview of the Histopathology of Human Melioidosis: A Case Series

Background

Melioidosis, caused by the Gram-negative bacterium Burkholderia pseudomallei, has a major global health impact and a wide range of different disease manifestations. Histopathological descriptions of melioidosis remain limited. Granulomatous inflammation with multinucleated giant cells are considered classic features. We aim to present a graphical overview of histopathological manifestations of melioidosis, serving as an aid in diagnosing this disease.

Methods

We performed a retrospective international multicenter laboratory-based analysis of formalin-fixed paraffin-embedded (FFPE) tissue from culture-confirmed melioidosis autopsy and biopsy cases. Available FFPE tissue was stained with hematoxylin and eosin and immunostainings including a monoclonal antibody targeting the capsular polysaccharide (CPS) of B pseudomallei. Tissue with site-specific cultures and/or positive CPS staining were included in the graphical histopathological overview.

Results

We identified tissue of 8 autopsy and 5 biopsy cases. Pneumonia and soft tissue abscesses were the leading foci of disease displaying mainly necrosis and suppuration. Infrequent disease manifestations included involvement of bone marrow and adrenal glands in an autopsy case and biopsied mediastinal tissue, the latter being the only case in which we identified multinucleated giant cells. Using the CPS staining, we demonstrated granulomata as part of rare gastric tissue involvement.

Conclusions

We found fatal melioidosis to be a necrotizing and suppurative inflammation, usually without multinucleated giant cell formation. Gastric and mediastinal involvement points to ingestion and inhalation as possible routes of infection. The CPS staining proved beneficial as an aid to establish a histopathological diagnosis. Our graphical overview can be used by infectious diseases specialists, microbiologists, and pathologists.

Anti-high-mobility group box-1 treatment strategies improve trauma-induced coagulopathy in a mouse model of trauma and shock

BACKGROUND

Trauma-induced coagulopathy is associated with platelet dysfunction and contributes to early mortality after traumatic injury. Plasma concentrations of the damage molecule high-mobility group box-1 (HMGB-1) increase after trauma, which may contribute to platelet dysfunction. We hypothesised that inhibition of HMGB-1 with a monoclonal antibody (mAb) or with recombinant thrombomodulin (rTM) improves trauma-induced coagulopathy in a murine model of trauma and shock.

METHODS

Male 129S2/SvPasOrlRJ mice were anaesthetised, mechanically ventilated, and randomised into five groups: (i) ventilation control (VENT), (ii) trauma/shock (TS), (iii) TS+anti-HMGB-1 mAb (TS+AB), (iv) TS+rTM (TS+TM), and (v) TS+anti-HMGB-1 mAb+rTM (TS+COMBI). Primary outcome was rotational thromboelastometry EXTEM. Secondary outcomes included tail bleeding time, platelet count, plasma HMGB-1 concentration, and platelet activation.

RESULTS

Trauma and shock resulted in a hypocoagulable thromboelastometry profile, increased plasma HMGB-1, and increased platelet activation markers. TS+AB was associated with improved clot firmness after 5 min compared with TS (34 [33-37] vs 32 [29-34] mm; P=0.043). TS+COMBI was associated with decreased clot formation time (98 [92-125] vs 122 [111-148] s; P=0.018) and increased alpha angle (77 [72-78] vs 69 [64-71] degrees; P=0.003) compared with TS. TS+COMBI also reduced tail bleeding time compared with TS (P=0.007). The TS+TM and TS+COMBI groups had higher platelet counts compared with TS (P=0.044 and P=0.041, respectively).

CONCLUSIONS

Inhibition of HMGB-1 early after trauma in a mouse model improves clot formation and strength, preserves platelet count, and decreases bleeding time.

Can volume-reduced plasma products prevent transfusion-associated circulatory overload in a two-hit animal model?

BACKGROUND AND OBJECTIVES

Transfusion-associated circulatory overload (TACO) is a pulmonary transfusion complication and a leading cause of transfusion-related morbidity and mortality. Volume overload and rising hydrostatic pressure as a consequence of transfusion are seen as the central pathway leading to TACO. A possible preventative measure for TACO could be the use of low-volume blood products like volume-reduced lyophilized plasma. We hypothesize that volume-reduced lyophilized plasma decreases circulatory overload leading to a reduced pulmonary capillary pressure and can therefore be an effective strategy to prevent TACO.

MATERIALS AND METHODS

A validated two-hit animal model in rats with heart failure was used. Animals were randomized to receive 4 units of either solvent-detergent pooled plasma (SDP) as control, standard volume lyophilized plasma (LP-S) or hyperoncotic volume-reduced lyophilized plasma (LP-VR). The primary outcome was the difference between pre-transfusion and post-transfusion left ventricular end-diastolic pressure (ΔLVEDP). Secondary outcomes included markers for acute lung injury.

RESULTS

LVEDP increased in all randomization groups following transfusion. The greatest elevation was seen in the group receiving LP-VR (+11.9 mmHg [5.9-15.6]), but there were no significant differences when compared to groups receiving either LP-S (+6.3 mmHg [2.9-13.4], p = 0.29) or SDP (+7.7 mmHg [4.5-10.5], p = 0.55). There were no significant differences in markers for acute lung injury, such as pulmonary wet/dry weight ratios, lung histopathology scores or PaO₂ /FiO₂ ratio between the three groups.

CONCLUSION

Transfusion with hyperoncotic volume-reduced plasma did not attenuate circulatory overload compared to standard volume plasma and was therefore not an effective preventative strategy for TACO in this rat model.

Myeloid miR-155 plays a limited role in antibacterial defense during Klebsiella-derived pneumosepsis and is dispensable for lipopolysaccharide- or Klebsiella-induced inflammation in mice

MicroRNA-155 (miR-155) plays a crucial role in regulating host inflammatory responses during bacterial infection. Previous studies have shown that constitutive miR-155 deficiency alleviates inflammation while having varying effects in different bacterial infection models. However, whether miR-155 in myeloid cells is involved in the regulation of inflammatory and antibacterial responses is largely elusive. Mice with myeloid cell specific miR-155 deficiency were generated to study the in vitro response of bone marrow-derived macrophages (BMDMs), alveolar macrophages (AMs) and peritoneal macrophages (PMs) to lipopolysaccharide (LPS), and the in vivo response after intranasal or intraperitoneal challenge with LPS or infection with Klebsiella (K.) pneumoniae via the airways. MiR-155-deficient macrophages released less inflammatory cytokines than control macrophages upon stimulation with LPS in vitro. However, the in vivo inflammatory cytokine response to LPS or K. pneumoniae was not affected by myeloid miR-155 deficiency. Moreover, bacterial outgrowth in the lungs was not altered in myeloid miR-155-deficient mice, but Klebsiella loads in the liver of these mice were significantly higher than in control mice. These data argue against a major role for myeloid miR-155 in host inflammatory responses during LPS-induced inflammation and K. pneumoniae-induced pneumosepsis but suggest that myeloid miR-155 contributes to host defense against Klebsiella infection in the liver.

Role of Hypoxia-inducible factor 1α in host defense during pneumococcal pneumonia

Hypoxia-inducible factor (HIF)1α is a transcription factor involved in cellular metabolism and regulation of immune cell effector functions. Here, we studied the role of HIF1α in myeloid cells during pneumonia caused by the major causative pathogen, Streptococcus pneumoniae (Spneu). Mice deficient for HIF1α in myeloid cells (LysMcreHif1αfl/fl) were generated to study the in vitro responsiveness of bone marrow-derived macrophages (BMDMs) and alveolar macrophages (AMs) to the Gram-positive bacterial wall component lipoteichoic acid (LTA) and heat-killed Spneu, and the in vivo host response after infection with Spneu via the airways. Both BMDMs and AMs released more lactate upon stimulation with LTA or Spneu, indicative of enhanced glycolysis; HIF1α-deficiency in these cells was associated with diminished lactate release. In BMDMs, HIF1α-deficiency resulted in reduced secretion of tumor necrosis factor (TNF)α and interleukin (IL)-6 upon activation with Spneu but not LTA, while HIF1α-deficient AMs secreted less TNFα and IL-6 in response to LTA, and TNFα after Spneu stimulation. However, no difference was found in the host response of LysMcreHif1αfl/fl mice after Spneu infection as compared to controls. Similar in vivo findings were obtained in neutrophil (Mrp8creHif1αfl/fl) HIF1α-deficient mice. These data suggest that myeloid HIF1α is dispensable for the host defense during pneumococcal pneumonia.

C/EBP-Family Redundancy Determines Patient Survival and Lymph Node Involvement in PDAC

Pancreatic ductal adenocarcinoma (PDAC) is a dismal disease with a poor clinical prognosis and unsatisfactory treatment options. We previously found that the transcription factor CCAAT/Enhancer-Binding Protein Delta (C/EBPδ) is lowly expressed in PDAC compared to healthy pancreas duct cells, and that patient survival and lymph node involvement in PDAC is correlated with the expression of C/EBPδ in primary tumor cells. C/EBPδ shares a homologous DNA-binding sequence with other C/EBP-proteins, leading to the presumption that other C/EBP-family members might act redundantly and compensate for the loss of C/EBPδ. This implies that patient stratification could be improved when expression levels of multiple C/EBP-family members are considered simultaneously. In this study, we assessed whether the quantification of C/EBPβ or C/EBPγ in addition to that of C/EBPδ might improve the prediction of patient survival and lymph node involvement using a cohort of 68 resectable PDAC patients. Using Kaplan-Meier analyses of patient groups with different C/EBP-expression levels, we found that both C/EBPβ and C/EBPγ can partially compensate for low C/EBPδ and improve patient survival. Further, we uncovered C/EBPβ as a novel predictor of a decreased likelihood of lymph node involvement in PDAC, and found that C/EBPβ and C/EBPδ can compensate for the lack of each other in order to reduce the risk of lymph node involvement. C/EBPγ, on the other hand, appears to promote lymph node involvement in the absence of C/EBPδ. Altogether, our results show that the redundancy of C/EBP-family members might have a profound influence on clinical prognoses and that the expression of both C/EPBβ and C/EBPγ should be taken into account when dichotomizing patients according to C/EBPδ expression.

Endothelial transmigration hotspots limit vascular leakage through heterogeneous expression of ICAM-1

Upon inflammation, leukocytes leave the circulation by crossing the endothelial monolayer at specific transmigration "hotspot" regions. Although these regions support leukocyte transmigration, their functionality is not clear. We found that endothelial hotspots function to limit vascular leakage during transmigration events. Using the photoconvertible probe mEos4b, we traced back and identified original endothelial transmigration hotspots. Using this method, we show that the heterogeneous distribution of ICAM-1 determines the location of the transmigration hotspot. Interestingly, the loss of ICAM-1 heterogeneity either by CRISPR/Cas9-induced knockout of ICAM-1 or equalizing the distribution of ICAM-1 in all endothelial cells results in the loss of TEM hotspots but not necessarily in reduced TEM events. Functionally, the loss of endothelial hotspots results in increased vascular leakage during TEM. Mechanistically, we demonstrate that the 3 extracellular Ig-like domains of ICAM-1 are crucial for hotspot recognition. However, the intracellular tail of ICAM-1 and the 4th Ig-like dimerization domain are not involved, indicating that intracellular signaling or ICAM-1 dimerization is not required for hotspot recognition. Together, we discovered that hotspots function to limit vascular leakage during inflammation-induced extravasation.

Myeloid liver kinase B1 contributes to lung inflammation induced by lipoteichoic acid but not by viable Streptococcus pneumoniae

Background

Liver kinase B1 (Lkb1, gene name Stk11) functions as a tumor suppressor in cancer. Myeloid cell Lkb1 potentiates lung inflammation induced by the Gram-negative bacterial cell wall component lipopolysaccharide and in host defense during Gram-negative pneumonia. Here, we sought to investigate the role of myeloid Lkb1 in lung inflammation elicited by the Gram-positive bacterial cell wall component lipoteichoic acid (LTA) and during pneumonia caused by the Gram-positive respiratory pathogen Streptococcus pneumoniae (Spneu).

Methods

Alveolar and bone marrow derived macrophages (AMs, BMDMs) harvested from myeloid-specific Lkb1 deficient (Stk11-ΔM) and littermate control mice were stimulated with LTA or Spneu in vitro. Stk11-ΔM and control mice were challenged via the airways with LTA or infected with Spneu in vivo.

Results

Lkb1 deficient AMs and BMDMs produced less tumor necrosis factor (TNF)α upon activation by LTA or Spneu. During LTA-induced lung inflammation, Stk11-ΔM mice had reduced numbers of AMs in the lungs, as well as diminished cytokine release and neutrophil recruitment into the airways. During pneumonia induced by either encapsulated or non-encapsulated Spneu, Stk11-ΔM and control mice had comparable bacterial loads and inflammatory responses in the lung, with the exception of lower TNFα levels in Stk11-ΔM mice after infection with the non-encapsulated strain.

Conclusion

Myeloid Lkb1 contributes to LTA-induced lung inflammation, but is not important for host defense during pneumococcal pneumonia.

Prophylactic furosemide to prevent transfusion-associated circulatory overload: a randomized controlled study in rats

Transfusion-associated circulatory overload (TACO) is the leading cause of transfusion related morbidity and mortality. The only treatment is empirical use of furosemide. Our aim was to investigate if furosemide can prevent TACO. A randomized controlled trial was performed using a previously validated two-hit rat model for TACO. Volume incompliance was induced (first hit) in anemic, anesthetized Lewis rats. Rats were randomized to placebo, low-dose (5 mg kg-1) or high-dose (15 mg kg-1) furosemide-administered prior to transfusion (second-hit) and divided over two doses. Primary outcome was change in left-ventricular end-diastolic pressure (∆LVEDP) pre- compared to post-transfusion. Secondary outcomes included changes in preload, afterload, contractility and systemic vascular resistance, as well as pulmonary outcomes. Furosemide treated animals had a significantly lower ∆LVEDP compared to placebo (p = 0.041), a dose-response effect was observed. ∆LVEDP in placebo was median + 8.7 mmHg (IQR 5.9-11), + 3.9 (2.8-5.6) in the low-dose and 1.9 (- 0.6 to 5.6) in the high-dose group. The effect of furosemide became apparent after 15 min. While urine output was significantly higher in furosemide treated animals (p = 0.03), there were no significant changes in preload, afterload, contractility or systemic vascular resistance. Furosemide rapidly and dose-dependently decreases the rise in hydrostatic pulmonary pressure following transfusion, essential for preventing TACO.

Diagnostic accuracy of calretinin and acetylcholinesterase staining of rectal suction biopsies in Hirschsprung disease examined by unexperienced pathologists

Rectal suction biopsy (RSB) is a gold standard for diagnosing Hirschsprung disease (HD). Calretinin staining of RSB is increasingly used by experienced pathologists due to non-complex examination and comparable diagnostic accuracy with acetylcholinesterase (AChE). However, the diagnostic accuracy of calretinin examined by unexperienced pathologists remains to be elucidated. Therefore, we aim to compare diagnostic accuracy of calretinin with AChE on RSB for diagnosing HD when examined by unexperienced pathologists. We prospectively analyzed sections from RSB stained with AChE + HE and calretinin. Blinded examination was done by five unexperienced pathologists (pathology residents) and three experienced pathologists (senior pediatric gastro-enterology pathologists) assessing for the presence of HD. Cases for the study included ones proven to be HD on resection specimens and cases without HD. Diagnostic accuracy was determined calculating area under the curve (AUC), sensitivity, specificity, likelihood ratio, and posttest probability. Fleiss’ kappa analysis was performed to assess interobserver agreement between reviewers. Eleven of 18 included patients (61%) were diagnosed with HD. Comparing the diagnostic accuracy of unexperienced pathologists, calretinin versus AChE + HE showed sensitivity of 80.0% versus 74.5% and specificity of 100% versus 65.4%, AUC of 0.87 (0.78–0.96) versus 0.59 (0.45–0.72). Unexperienced pathologists showed substantial agreement with calretinin (kappa 0.72 [0.61–0.84]) and fair agreement with AChE + HE (kappa 0.34 [0.23–0.44]). We found calretinin having higher diagnostic accuracy in diagnosing HD compared to AChE + HE when examined by unexperienced pathologists. Therefore, we recommend to use calretinin as the standard technique for staining RSB in diagnosing HD.

Differential effects of speed and volume on transfusion-associated circulatory overload: A randomized study in rats

BACKGROUND AND OBJECTIVES

Transfusion-associated circulatory overload (TACO) is the primary cause of transfusion-related mortality. Speed and volume of transfusion are major risk factors. The aim of this study was to investigate the interaction of red blood cell (RBC) transfusion speed and volume on the development of TACO.

MATERIALS AND METHODS

A validated model for TACO in anaemic Lewis rats with an acute myocardial infarction was used. The effect on pulmonary hydrostatic pressure of one, two or four units of packed RBCs transfused in either 30 or 60 min was evaluated (3.3-26.6 ml·kg-1 ·hr-1 ). Pulmonary capillary pressure was measured as left ventricular end-diastolic pressure (LVEDP). Cardiac stress biomarkers atrial natriuretic-peptide (ANP) and N-terminal pro-brain natriuretic peptide (NT-proBNP) were measured 1-h post-transfusion.

RESULTS

Thirty animals were included (n = 5 per group). Transfusion of RBCs increased LVEDP in a volume-dependent manner (ΔLVEDP [mmHg]: -0.95, +0.50, +6.26, p < 0.001). Fast transfusion increased overall ΔLVEDP by +3.5 mmHg and up to +11.8 mmHg in the four units' group (p = 0.016). Doubling transfusion speed increased ΔLVEDP more than doubling volume in the larger volume groups. No difference in ANP or NT-proBNP were seen in high transfusion volume or groups.

CONCLUSION

Transfusion volume dose-dependently increased LVEDP, with speed of transfusion rapidly elevating LVEDP at higher transfusion volumes. ANP and NT-proBNP were not impacted by transfusion volume or speed in this model. TACO is seen as purely volume overload, however, this study emphasizes that limiting transfusion speed, as a modifiable risk factor, might aid in preventing TACO.

Deep learning-based classification of kidney transplant pathology: a retrospective, multicentre, proof-of-concept study

BACKGROUND

Histopathological assessment of transplant biopsies is currently the standard method to diagnose allograft rejection and can help guide patient management, but it is one of the most challenging areas of pathology, requiring considerable expertise, time, and effort. We aimed to analyse the utility of deep learning to preclassify histology of kidney allograft biopsies into three main broad categories (ie, normal, rejection, and other diseases) as a potential biopsy triage system focusing on transplant rejection.

METHODS

We performed a retrospective, multicentre, proof-of-concept study using 5844 digital whole slide images of kidney allograft biopsies from 1948 patients. Kidney allograft biopsy samples were identified by a database search in the Departments of Pathology of the Amsterdam UMC, Amsterdam, Netherlands (1130 patients) and the University Medical Center Utrecht, Utrecht, Netherlands (717 patients). 101 consecutive kidney transplant biopsies were identified in the archive of the Institute of Pathology, RWTH Aachen University Hospital, Aachen, Germany. Convolutional neural networks (CNNs) were trained to classify allograft biopsies as normal, rejection, or other diseases. Three times cross-validation (1847 patients) and deployment on an external real-world cohort (101 patients) were used for validation. Area under the receiver operating characteristic curve (AUROC) was used as the main performance metric (the primary endpoint to assess CNN performance).

FINDINGS

Serial CNNs, first classifying kidney allograft biopsies as normal (AUROC 0·87 [ten times bootstrapped CI 0·85-0·88]) and disease (0·87 [0·86-0·88]), followed by a second CNN classifying biopsies classified as disease into rejection (0·75 [0·73-0·76]) and other diseases (0·75 [0·72-0·77]), showed similar AUROC in cross-validation and deployment on independent real-world data (first CNN normal AUROC 0·83 [0·80-0·85], disease 0·83 [0·73-0·91]; second CNN rejection 0·61 [0·51-0·70], other diseases 0·61 [0·50-0·74]). A single CNN classifying biopsies as normal, rejection, or other diseases showed similar performance in cross-validation (normal AUROC 0·80 [0·73-0·84], rejection 0·76 [0·66-0·80], other diseases 0·50 [0·36-0·57]) and generalised well for normal and rejection classes in the real-world data. Visualisation techniques highlighted rejection-relevant areas of biopsies in the tubulointerstitium.

INTERPRETATION

This study showed that deep learning-based classification of transplant biopsies could support pathological diagnostics of kidney allograft rejection.

FUNDING

European Research Council; German Research Foundation; German Federal Ministries of Education and Research, Health, and Economic Affairs and Energy; Dutch Kidney Foundation; Human(e) AI Research Priority Area of the University of Amsterdam; and Max-Eder Programme of German Cancer Aid.

Renal involvement in a patient with the chronic visceral subtype of acid sphingomyelinase deficiency resembles Fabry disease

Acid sphingomyelinase deficiency (ASMD) is a lysosomal storage disease (LSD) in which sphingomyelin accumulates due to deficient acid sphingomyelinase. In the chronic visceral subtype, organ manifestations are generally limited to the spleen, liver, and lungs. We report a male patient with the chronic visceral subtype who developed proteinuria and renal insufficiency at the age of 49. In renal tissue, foam cells were observed in the glomeruli as well as sphingomyelin accumulation within podocytes, mesangial cells, endothelial cells, and tubular epithelial cells. Although macrophages are the primary storage cells in both ASMD and Gaucher disease, comparison to the histopathological findings in Gaucher and Fabry disease revealed a diffuse storage pattern in multiple renal cell types, closer resembling the pattern found in Fabry disease.

Bruton's Tyrosine Kinase-Mediated Signaling in Myeloid Cells Is Required for Protective Innate Immunity During Pneumococcal Pneumonia

Bruton’s tyrosine kinase (Btk) is a cytoplasmic kinase expressed in B cells and myeloid cells. It is essential for B cell development and natural antibody-mediated host defense against bacteria in humans and mice, but little is known about the role of Btk in innate host defense in vivo. Previous studies have indicated that lack of (natural) antibodies is paramount for impaired host defense against Streptococcus (S.) pneumoniae in patients and mice with a deficiency in functional Btk. In the present study, we re-examined the role of Btk in B cells and myeloid cells during pneumococcal pneumonia and sepsis in mice. The antibacterial defense of Btk^-/- mice was severely impaired during pneumococcal pneumosepsis and restoration of natural antibody production in Btk^-/- mice by transgenic expression of Btk specifically in B cells did not suffice to protect against infection. Btk^-/- mice with reinforced Btk expression in MhcII⁺ cells, including B cells, dendritic cells and macrophages, showed improved antibacterial defense as compared to Btk^-/- mice. Bacterial outgrowth in Lysmcre-Btk^fl/Y mice was unaltered despite a reduced capacity of Btk-deficient alveolar macrophages to respond to pneumococci. Mrp8cre-Btk^fl/Y mice with a neutrophil specific paucity in Btk expression, however, demonstrated impaired antibacterial defense. Neutrophils of Mrp8cre-Btk^fl/Y mice displayed reduced release of granule content after pulmonary installation of lipoteichoic acid, a gram-positive bacterial cell wall component relevant for pneumococci. Moreover, Btk deficient neutrophils showed impaired degranulation and phagocytosis upon incubation with pneumococci ex vivo. Taken together, the results of our study indicate that besides regulating B cell-mediated immunity, Btk is critical for regulation of myeloid cell-mediated, and particularly neutrophil-mediated, innate host defense against S. pneumoniae in vivo.

The effect of targeting Tie2 on hemorrhagic shock-induced renal perfusion disturbances in rats

BACKGROUND

Hemorrhagic shock is associated with acute kidney injury and increased mortality. Targeting the endothelial angiopoietin/Tie2 system, which regulates endothelial permeability, previously reduced hemorrhagic shock-induced vascular leakage. We hypothesized that as a consequence of vascular leakage, renal perfusion and function is impaired and that activating Tie2 restores renal perfusion and function.

METHODS

Rats underwent 1 h of hemorrhagic shock and were treated with either vasculotide or PBS as control, followed by fluid resuscitation for 4 h. Microcirculatory perfusion was measured in the renal cortex and cremaster muscle using contrast echography and intravital microscopy, respectively. Changes in the angiopoietin/Tie2 system and renal injury markers were measured in plasma and on protein and mRNA level in renal tissue. Renal edema formation was determined by wet/dry weight ratios and renal structure by histological analysis.

RESULTS

Hemorrhagic shock significantly decreased renal perfusion (240 ± 138 to 51 ± 40, p < 0.0001) and cremaster perfusion (12 ± 2 to 5 ± 2 perfused vessels, p < 0.0001) compared to baseline values. Fluid resuscitation partially restored both perfusion parameters, but both remained below baseline values (renal perfusion 120 ± 58, p = 0.08, cremaster perfusion 7 ± 2 perfused vessels, p < 0.0001 compared to baseline). Hemorrhagic shock increased circulating angiopoietin-1 (p < 0.0001), angiopoietin-2 (p < 0.0001) and soluble Tie2 (p = 0.05), of which angiopoietin-2 elevation was associated with renal edema formation (r = 0.81, p < 0.0001). Hemorrhagic shock induced renal injury, as assessed by increased levels of plasma neutrophil gelatinase-associated lipocalin (NGAL: p < 0.05), kidney injury marker-1 (KIM-1; p < 0.01) and creatinine (p < 0.05). Vasculotide did not improve renal perfusion (p > 0.9 at all time points) or reduce renal injury (NGAL p = 0.26, KIM-1 p = 0.78, creatinine p > 0.9, renal edema p = 0.08), but temporarily improved cremaster perfusion at 3 h following start of fluid resuscitation compared to untreated rats (resuscitation + 3 h: 11 ± 3 vs 8 ± 3 perfused vessels, p < 0.05).

CONCLUSION

Hemorrhagic shock-induced renal impairment cannot be restored by standard fluid resuscitation, nor by activation of Tie2. Future treatment strategies should focus on reducing angiopoietin-2 levels or on activating Tie2 via an alternative strategy.

Bronchial epithelial DNA methyltransferase 3b dampens pulmonary immune responses during Pseudomonas aeruginosa infection

DNA methyltransferase (Dnmt)3b mediates de novo DNA methylation and modulation of Dnmt3b in respiratory epithelial cells has been shown to affect the expression of multiple genes. Respiratory epithelial cells provide a first line of defense against pulmonary pathogens and play a crucial role in the immune response during pneumonia caused by Pseudomonas (P.) aeruginosa, a gram-negative bacterium that expresses flagellin as an important virulence factor. We here sought to determine the role of Dntm3b in respiratory epithelial cells in immune responses elicited by P. aeruginosa. DNMT3B expression was reduced in human bronchial epithelial (BEAS-2B) cells as well as in primary human and mouse bronchial epithelial cells grown in air liquid interface upon exposure to P. aeruginosa (PAK). Dnmt3b deficient human bronchial epithelial (BEAS-2B) cells produced more CXCL1, CXCL8 and CCL20 than control cells when stimulated with PAK, flagellin-deficient PAK (PAKflic) or flagellin. Dnmt3b deficiency reduced DNA methylation at exon 1 of CXCL1 and enhanced NF-ĸB p65 binding to the CXCL1 promoter. Mice with bronchial epithelial Dntm3b deficiency showed increased Cxcl1 mRNA expression in bronchial epithelium and CXCL1 protein release in the airways during pneumonia caused by PAK, which was associated with enhanced neutrophil recruitment and accelerated bacterial clearance; bronchial epithelial Dnmt3b deficiency did not modify responses during pneumonia caused by PAKflic or Klebsiella pneumoniae (an un-flagellated gram-negative bacterium). Dnmt3b deficiency in type II alveolar epithelial cells did not affect mouse pulmonary defense against PAK infection. These results suggest that bronchial epithelial Dnmt3b impairs host defense during Pseudomonas induced pneumonia, at least in part, by dampening mucosal responses to flagellin.

Bronchial Thermoplasty Induced Airway Smooth Muscle Reduction and Clinical Response in Severe Asthma. The TASMA Randomized Trial

Rationale: Bronchial thermoplasty (BT) is a bronchoscopic treatment for severe asthma targeting airway smooth muscle (ASM). Observational studies have shown ASM mass reduction after BT, but appropriate control groups are lacking. Furthermore, as treatment response is variable, identifying optimal candidates for BT treatment is important.Objectives: First, to assess the effect of BT on ASM mass, and second, to identify patient characteristics that correlate with BT response.Methods: Patients with severe asthma (n = 40) were randomized to immediate (n = 20) or delayed (n = 20) BT treatment. Before randomization, clinical, functional, blood, and airway biopsy data were collected. In the delayed control group, reassessment, including biopsies, was performed after 6 months of standard clinical care, followed by BT. In both groups, post-BT data including biopsies were obtained after 6 months. ASM mass (% positive desmin or α-smooth muscle actin area in the total biopsy) was calculated with automated digital analysis software. Associations between baseline characteristics and Asthma Control Questionnaire and Asthma Quality of Life Questionnaire (AQLQ) improvement were explored.Measurements and Main Results: Median ASM mass decreased by >50% in the immediate BT group (n = 17) versus no change in the delayed control group (n = 19) (P = 0.0004). In the immediate group, Asthma Control Questionnaire scores improved with -0.79 (interquartile range [IQR], -1.61 to 0.02) compared with 0.09 (IQR, -0.25 to 1.17) in the delayed group (P = 0.006). AQLQ scores improved with 0.83 (IQR, -0.15 to 1.69) versus -0.02 (IQR, -0.77 to 0.75) (P = 0.04). Treatment response in the total group (n = 35) was positively associated with serum IgE and eosinophils but not with baseline ASM mass.Conclusions: ASM mass significantly decreases after BT when compared with a randomized non-BT-treated control group. Treatment response was associated with serum IgE and eosinophil levels but not with ASM mass.

Cellular origin and microRNA profiles of circulating extracellular vesicles in different stages of diabetic nephropathy

BACKGROUND

Diabetic nephropathy (DN) is a major complication of diabetes and the main cause of end-stage renal disease. Extracellular vesicles (EVs) are small cell-derived vesicles that can alter disease progression by microRNA (miRNA) transfer.

METHODS

In this study, we aimed to characterize the cellular origin and miRNA content of EVs in plasma samples of type 2 diabetes patients at various stages of DN. Type 2 diabetes patients were classified in three groups: normoalbuminuria, microalbuminuria and macroalbuminuria. The concentration and cellular origin of plasma EVs were measured by flow cytometry. A total of 752 EV miRNAs were profiled in 18 subjects and differentially expressed miRNAs were validated.

RESULTS

Diabetic patients with microalbuminuria and/or macroalbuminuria showed elevated concentrations of total EVs and EVs from endothelial cells, platelets, leucocytes and erythrocytes compared with diabetic controls. miR-99a-5p was upregulated in macroalbuminuric patients compared with normoalbuminuric and microalbuminuric patients. Transfection of miR-99a-5p in cultured human podocytes downregulated mammalian target of rapamycin (mTOR) protein expression and downregulated the podocyte injury marker vimentin.

CONCLUSIONS

Type 2 diabetes patients with microalbuminuria and macroalbuminuria display differential EV profiles. miR-99a-5p expression is elevated in EVs from macroalbuminuria and mTOR is its validated mRNA target.

Therapeutic application of recombinant human ADAMTS-13 improves shock reversal and coagulation status in a trauma hemorrhage and transfusion rat model

INTRODUCTION

In hemorrhaging trauma patients, the endothelium is activated, resulting in excessive endothelial synthesis of von Willebrand Factor (vWF), which may enhance micro-thrombi formation, resulting in obstruction of the microcirculation and endothelial injury, aggravating bleeding, as well as contributing to organ failure. Under normal conditions, vWF is cleaved by the metalloprotease ADAMTS-13. After trauma, ADAMTS-13 levels are reduced.

OBJECTIVES

To assess whether recombinant human ADAMTS-13 inhibits endothelial injury and organ failure in a rat trauma-transfusion model.

METHODS

Blood products were prepared from syngeneic rat blood according to blood bank standards. Polytrauma was induced in rats by crush injury to the intestines and liver and by fracture of the femur. The rats were hemorrhaged until a mean arterial pressure (MAP) of 40 mmHg was reached. Rats were randomized to receive transfusion of RBCs, FFPs, and platelets in a 1:1:1 ratio to achieve a MAP of 70 mmHg, with or without the addition of ADAMTS-13 (50 μg/kg). Blood samples were assessed for biochemistry and rotational thromboelastometry (ROTEM). Syndecan-1 and VE-cadherin levels were measured as a reflection of endothelial integrity. The amount of leakage of dextran-FITC from the vascular system to the parenchyma in lungs was quantified. To assess inflammation, IL-6 and IL-8 levels were determined. Organ damage was assessed by histopathology.

RESULTS

All rats were severely shocked, with no significant differences in shock parameters between groups. Rats treated with ADAMTS-13 showed signs of a more effective shock reversal (higher blood pressure, lower lactate levels) compared to controls. Also, ROTEM parameters of clot formation in rats receiving ADAMTS-13 improved compared to controls, which was mainly platelet-dependent. Syndecan-1 levels relative to baseline trended to be lower in ADAMTS-13 treated rats compared to controls (107 vs 149%, p = 0.08). ADAMTS-13 reduced albuminuria (1.7 vs 4.4 g/L, p < 0.01) and organ-specific inflammation (pulmonary IL-6 243 vs 369 pg/mL, p = 0.08; splenic IL-6 253 vs 307, p = 0.03) compared to controls, but did not improve histopathological scores.

CONCLUSIONS

The use of ADAMTS-13 in a rat trauma-transfusion model improves parameters of shock, platelet-driven coagulation, endothelial damage, and organ inflammation. These results suggest that ADAMTS-13 is important in mediating outcome of trauma. Whether ADAMTS-13 can be used as a therapeutic adjunct to treat bleeding trauma patients remains to be determined.

Urinary mitochondrial DNA associates with delayed graft function following renal transplantation

BACKGROUND

Ischaemia-reperfusion (IR) injury is an important determinant of delayed graft function (DGF) affecting allograft function. Mitochondrial DNA (mtDNA) is released upon cell death and platelet activation into the extracellular environment and has been suggested to be a biomarker in several diseases. Whether extracellular mtDNA accumulates in plasma and/or urine upon renal IR and predisposes DGF is unknown.

METHODS

C57BL/6J wild-type mice were subjected to renal IR. In addition, an observational case-control study was set up enrolling 43 patients who underwent kidney transplantation. One day post-IR in mice and a few days following renal transplantation in human, blood and urine were collected. Patients were stratified into DGF and non-DGF groups.

RESULTS

mtDNA-encoded genes accumulate in urine and plasma in both mice subjected to renal IR injury and in humans following renal transplantation. In human renal transplant recipients, cold ischaemia time and renal function correlate with urinary mtDNA levels. Urinary mtDNA levels but not urinary nuclear DNA levels were significantly higher in the DGF group compared with the non-DGF group. Multiple receiver operating characteristic curves revealed significant diagnostic performance for mtDNA-encoded genes cytochrome c oxidase III (COXIII); nicotinamide adenine dinucleotide hydrogen subunit 1 (NADH-deh); mitochondrially encoded, mitochondrially encoded nicotinamide adenine dinucleotide dehydrogenase 2 (MT-ND2) with an area under the curve of, respectively, 0.71 [P = 0.03; 95% confidence interval (CI) 0.54-0.89], 0.75 (P = 0.01; 95% CI 0.58-0.91) and 0.74 (P = 0.02; 95% CI 0.58-0.89).

CONCLUSIONS

These data suggest that renal ischaemia time determines the level of mtDNA accumulation in urine, which associates with renal allograft function and the diagnosis of DGF following renal transplantation.

Viral presence and immunopathology in patients with lethal COVID-19: a prospective autopsy cohort study

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) targets multiple organs and causes severe coagulopathy. Histopathological organ changes might not only be attributable to a direct virus-induced effect, but also the immune response. The aims of this study were to assess the duration of viral presence, identify the extent of inflammatory response, and investigate the underlying cause of coagulopathy.

METHODS

This prospective autopsy cohort study was done at Amsterdam University Medical Centers (UMC), the Netherlands. With informed consent from relatives, full body autopsy was done on 21 patients with COVID-19 for whom autopsy was requested between March 9 and May 18, 2020. In addition to histopathological evaluation of organ damage, the presence of SARS-CoV-2 nucleocapsid protein and the composition of the immune infiltrate and thrombi were assessed, and all were linked to disease course.

FINDINGS

Our cohort (n=21) included 16 (76%) men, and median age was 68 years (range 41-78). Median disease course (time from onset of symptoms to death) was 22 days (range 5-44 days). In 11 patients tested for SARS-CoV-2 tropism, SARS-CoV-2 infected cells were present in multiple organs, most abundantly in the lungs, but presence in the lungs became sporadic with increased disease course. Other SARS-CoV-2-positive organs included the upper respiratory tract, heart, kidneys, and gastrointestinal tract. In histological analyses of organs (sampled from nine to 21 patients per organ), an extensive inflammatory response was present in the lungs, heart, liver, kidneys, and brain. In the brain, extensive inflammation was seen in the olfactory bulbs and medulla oblongata. Thrombi and neutrophilic plugs were present in the lungs, heart, kidneys, liver, spleen, and brain and were most frequently observed late in the disease course (15 patients with thrombi, median disease course 22 days [5-44]; ten patients with neutrophilic plugs, 21 days [5-44]). Neutrophilic plugs were observed in two forms: solely composed of neutrophils with neutrophil extracellular traps (NETs), or as aggregates of NETs and platelets..

INTERPRETATION

In patients with lethal COVID-19, an extensive systemic inflammatory response was present, with a continued presence of neutrophils and NETs. However, SARS-CoV-2-infected cells were only sporadically present at late stages of COVID-19. This suggests a maladaptive immune response and substantiates the evidence for immunomodulation as a target in the treatment of severe COVID-19.

FUNDING

Amsterdam UMC Corona Research Fund.

Platelet inhibition by ticagrelor is protective against diabetic nephropathy in mice

Diabetic nephropathy (DN) is a major complication of diabetes and is associated with high risk for cardiovascular mortality, which is partially related to elevated platelet activity. Platelets are also active players in inflammation and fibrosis. In this study, we examine the effect of ticagrelor-induced platelet inhibition on the development of DN. DN was induced by unilateral nephrectomy followed by streptozotocin injections for 5 days. Mice received ticagrelor (300 mg/kg) or vehicle every other day, for 16 weeks. Experimental groups: non-diabetic control, diabetic control, non-diabetic ticagrelor, and diabetic ticagrelor. Ticagrelor treatment in diabetic mice lowered urinary albumin excretion, it prevented diabetes-induced mesangial matrix expansion, podocyte effacement, and glomerular endothelial cell injury, which includes loss of endothelial fenestrations, ICAM-1 expression, and PECAM expression. In addition, ticagrelor treatment prevented collagen IV deposition and macrophage infiltration in the tubulointerstitium and these diabetic mice showed lower systemic and tubular inflammation and tubular apoptosis. This tubular protection is likely to be a result of protection to the glomerular endothelium by ticagrelor, which reduces albuminuria and albumin toxicity to the tubules and reduced tubular and interstitial inflammation and fibrosis. In conclusion, ticagrelor-induced platelet inhibition protects against renal injury in diabetic mice, likely by protecting the glomerular endothelial cells.

Vendor effects on murine gut microbiota and its influence on lipopolysaccharide-induced lung inflammation and Gram-negative pneumonia

Background

The microbiome has emerged as an important player in the pathophysiology of a whole spectrum of diseases that affect the critically ill. We hypothesized that differences in microbiota composition across vendors can influence murine models of pulmonary lipopolysaccharide (LPS) inflammation and Gram-negative pneumonia.

Methods

A multi-vendor approach was used with genetically similar mice derived from three different vendors (Janvier, Envigo, Charles River). This model was employed to study the effect on the host response to a pulmonary LPS challenge (1 μg Klebsiella pneumoniae LPS, intranasal), as well as experimental K. pneumoniae infection (ATCC43816, 1 × 10⁴ CFU, intranasal).

Results

Gut microbiota analysis revealed profound intervendor differences in bacterial composition as shown by beta diversity and at various taxonomic levels. Tumor necrosis factor (TNF)-α and interleukin (IL)-6 release in lung and bronchoalveolar lavage fluid (BALF) were determined 6 and 24 h after intranasal treatment with LPS. No differences were found between the groups, with the exception for Envigo, showing a higher level of TNFα in lung and BALF at 6 h compared to Janvier and Charles River. In another set of experiments, mice from different vendors were subjected to a clinically relevant model of Gram-negative pneumonia (K. pneumoniae). At 12 and 36 h post-infection, no intervendor differences were found in bacterial dissemination, or TNFα and IL-6 levels in the lungs. In line, markers for organ failure did not differ between groups.

Conclusions

Although there was a marked variation in the gut microbiota composition of mice from different vendors, the hypothesized impact on our models of pulmonary inflammation and severe pneumonia was limited. This is of significance for experimental settings, showing that differences in gut microbiota do not have to lead to differences in outcome.

Allogeneic hematopoietic cell transplantation in the management of GATA2 deficiency and pulmonary alveolar proteinosis

Human hematopoiesis is critically dependent on the transcription factor GATA2. Patients with GATA2 deficiency typically present with myelodysplastic syndrome, reduced numbers of monocytes, NK cells and B cells, and/or opportunistic infections. Here, we present two families that harbor distinct GATA2 mutations with highly variable onset and course of disease. We discuss the use of allogeneic hematopoietic cell transplantation in these patients, especially as treatment for pulmonary alveolar proteinosis.

Myeloid Liver Kinase B1 depletion is associated with a reduction in alveolar macrophage numbers and an impaired host defense during gram-negative pneumonia

BACKGROUND

Liver kinase B1 (LKB1) has been studied extensively as a tumor suppressor gene (Stk11) in the context of cancer. We hypothesized that myeloid LKB1 plays a role in innate immunity during pneumonia.

METHODS

Mice deficient for LKB1 in myeloid cells (LysM-cre x Stk11fl/fl ) or neutrophils (Mrp8-cre x Stk11fl/fl) were infected with Klebsiellapneumoniae via the airways. LysM-cre x Stk11fl/fl mice were also intranasally challenged with lipopolysaccharide (LPS).

RESULTS

Myeloid, but not neutrophil LKB1 deficient mice had increased bacterial loads in lungs from 6 to 40 hours after infection as compared to control mice, pointing at a role for LKB1 in macrophages. Myeloid LKB1 deficiency was associated with reduced cytokine release into the airways upon local LPS instillation. The number of classical (SiglecFhighCD11bneg) alveolar macrophages (AMs) was reduced by approximately 50% in the lungs of myeloid LKB1 deficient mice, which was not caused by increased cell death or reduced proliferation. Instead, myeloid LKB1 deficient mice had AMs with a 'non-classical' (SiglecFlowCD11bpos) phenotype. AMs did not upregulate glycolysis in response to LPS, irrespective of LKB1 presence.

CONCLUSION

Myeloid LKB1 is important for local host defense during Klebsiella pneumonia by maintaining adequate AM numbers in the lung.

Clinical consequences of primary CMV infection after renal transplantation: a case-control study

The impact of primary cytomegalovirus infection (pCMV) on renal allograft function and histology is controversial. We evaluated the influence on incidence of acute rejection, allograft loss, allograft function and interstitial fibrosis/tubular atrophy (IF/TA). Retrospective case-control study, recipients transplanted between 2000 and 2014. Risk of acute rejection and allograft loss for those who experienced pCMV infection compared with those who did not, within an exposure period of two months after transplantation. Besides, its influence on allograft function and histology at one to three years after transplantation. Of 113 recipients experienced pCMV infection, 306 remained CMV seronegative. pCMV infection in the exposure period could not be proven as increasing the risk for acute rejection [HR = 2.18 (95% CI 0.80-5.97) P = 0.13] or allograft loss [HR = 1.11 (95%CI 0.33-3.72) P = 0.87]. Combination of pCMV infection and acute rejection posed higher hazard for allograft loss than acute rejection alone [HR = 3.69 (95% CI 1.21-11.29) P = 0.02]. eGFR(MDRD) values did not significantly differ at years one [46 vs. 50], two [46 vs. 51] and three [46 vs. 52]. No association between pCMV infection and IF/TA could be demonstrated [OR = 2.15 (95%CI 0.73-6.29) P = 0.16]. pCMV infection was not proven to increase the risk for acute rejection or allograft loss. However, it increased the risk for rejection-associated allograft loss. In remaining functioning allografts, it was not significantly associated with decline in function nor with presence of IF/TA.

Renal amyloidosis: validation of a proposed histological scoring system in an independent cohort

Background

In systemic amyloidosis, the kidney is frequently affected and renal involvement has a major impact on survival. Renal involvement is clinically characterized by decreased estimated glomerular filtration rate (eGFR) and proteinuria. The two most common renal amyloidosis types are light chain-related amyloidosis (AL) and serum amyloid A (AA) amyloidosis. Standardized histopathological scoring of amyloid deposits is crucial to assess disease progression. Therefore, we aimed to validate the proposed scoring system from Rubinstein et al. (Novel pathologic scoring tools predict end-stage kidney disease in light chain (AL) amyloidosis. Amyloid 2017; 24: 205–211) in an independent patient cohort.

Methods

We attempt to reproduce the scoring system, consisting of an amyloid score (AS) and a composite scarring injury score (CSIS), in a multicentre AL and AA case series. Additionally, we analysed all renal amyloidosis kidney biopsies performed in the Netherlands between 1993 and 2012.

Results

Similar to the original study, AS and CSIS correlated to eGFR (r = −0.45, P = 0.0061 and r = −0.60, P < 0.0001, respectively) but not to proteinuria at diagnosis. Furthermore, AS, but not CSIS, was associated with renal outcome. The scoring system was not reproducible in AA patients. The median incidence rate for renal amyloidosis in the Netherlands was 2.3 per million population per year, and increased during the study period.

Conclusions

In our AL case series and the original study, AS and CSIS were correlated to eGFR but not to proteinuria, and AS correlated with renal outcome. Overall, we regard this scoring system as competent for standardized histopathological assessment of amyloid deposits burden and thereby disease advancement in renal biopsies.

Thrombocytopenia Impairs Host Defense Against Burkholderia pseudomallei (Melioidosis)

Background

Infection with the gram-negative bacillus Burkholderia pseudomallei (melioidosis) is an important cause of pneumosepsis in Southeast Asia and has a mortality of up to 40%. We aimed to assess the role of platelets in the host response against B. pseudomallei infection.

Methods

Association between platelet counts and mortality was determined in 1160 patients with culture-proven melioidosis. Mice treated with (low- or high-dose) platelet-depleting antibody were inoculated intranasally with B. pseudomallei and killed. Additional studies using functional glycoprotein Ibα-deficient mice were conducted.

Results

Thrombocytopenia was present in 31% of patients at admission and predicted mortality in melioidosis patients even after adjustment for confounders. In our murine-melioidosis model, platelet counts decreased, and mice treated with a platelet-depleting antibody showed enhanced mortality and higher bacterial loads compared to mice with normal platelet counts. Low platelet counts had a modest impact on early-pulmonary neutrophil influx. Reminiscent of their role in hemostasis, platelet depletion impaired vascular integrity, resulting in early lung bleeding. Glycoprotein Ibα-deficient mice had reduced platelet counts during B. pseudomallei infection together with an impaired local host defense in the lung.

Conclusions

Thrombocytopenia predicts mortality in melioidosis patients and, during experimental melioidosis, platelets play a protective role in both innate immunity and vascular integrity.

Volume incompliance and transfusion are essential for transfusion-associated circulatory overload: a novel animal model

BACKGROUND

Transfusion‐associated circulatory overload (TACO) is the predominant complication of transfusion resulting in death. The pathophysiology is poorly understood, but inability to manage volume is associated with TACO, and observational data suggest it is different from simple cardiac overload due to fluids. We developed a two‐hit TACO animal model to assess the role of volume incompliance (“first‐hit”) and studied whether volume overload (“second‐hit”) by red blood cell (RBC) transfusion is different compared to fluids (Ringer's lactate [RL]).

MATERIALS AND METHODS

Male adult Lewis rats were stratified into a control group (no intervention) or a first hit: either myocardial infarction (MI) or acute kidney injury (AKI). Animals were randomized to a second hit of either RBC transfusion or an equal volume of RL. A clinically relevant difference was defined as an increase in left ventricular end‐diastolic pressure (ΔLVEDP) of +4.0 mm Hg between the RBC and RL groups.

RESULTS

In control animals (without first hit) LVEDP was not different between infusion groups (Δ + 1.6 mm Hg). LVEDP increased significantly more after RBCs compared to RL in animals with MI (Δ7.4 mm Hg) and AKI (Δ + 5.4 mm Hg), respectively. Volume‐incompliant rats matched clinical TACO criteria in 92% of transfused versus 25% of RL‐infused animals, with a greater increase in heart rate and significantly higher blood pressure.

CONCLUSION

To our knowledge, this is the first animal model for TACO, showing that a combination of volume incompliance and transfusion is essential for development of circulatory overload. This model allows for further testing of mechanistic factors as well as therapeutic approaches.

Deep Learning-Based Histopathologic Assessment of Kidney Tissue

BACKGROUND

The development of deep neural networks is facilitating more advanced digital analysis of histopathologic images. We trained a convolutional neural network for multiclass segmentation of digitized kidney tissue sections stained with periodic acid-Schiff (PAS).

METHODS

We trained the network using multiclass annotations from 40 whole-slide images of stained kidney transplant biopsies and applied it to four independent data sets. We assessed multiclass segmentation performance by calculating Dice coefficients for ten tissue classes on ten transplant biopsies from the Radboud University Medical Center in Nijmegen, The Netherlands, and on ten transplant biopsies from an external center for validation. We also fully segmented 15 nephrectomy samples and calculated the network's glomerular detection rates and compared network-based measures with visually scored histologic components (Banff classification) in 82 kidney transplant biopsies.

RESULTS

The weighted mean Dice coefficients of all classes were 0.80 and 0.84 in ten kidney transplant biopsies from the Radboud center and the external center, respectively. The best segmented class was "glomeruli" in both data sets (Dice coefficients, 0.95 and 0.94, respectively), followed by "tubuli combined" and "interstitium." The network detected 92.7% of all glomeruli in nephrectomy samples, with 10.4% false positives. In whole transplant biopsies, the mean intraclass correlation coefficient for glomerular counting performed by pathologists versus the network was 0.94. We found significant correlations between visually scored histologic components and network-based measures.

CONCLUSIONS

This study presents the first convolutional neural network for multiclass segmentation of PAS-stained nephrectomy samples and transplant biopsies. Our network may have utility for quantitative studies involving kidney histopathology across centers and provide opportunities for deep learning applications in routine diagnostics.

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.

Experimental thrombocytopenia does not affect acute kidney injury 24 hours after renal ischemia reperfusion in mice

The pathophysiology of renal ischemia/reperfusion (I/R) injury is characterized by excessive activation of inflammation and coagulation processes followed by abnormal renal tissue repair, resulting in renal injury and function loss. Platelets are important actors in these processes, however to what extent platelets contribute to the pathophysiology of renal I/R injury still needs to be elucidated. In the current study, we treated wild-type mice with a platelet depleting antibody, which caused thrombocytopenia. We then investigated the role of platelets during the pathophysiology of renal I/R by subjecting control wild-type mice with normal platelet counts and thrombocytopenic wild-type mice to renal I/R injury. Our results showed that in the early phase of renal I/R injury, thrombocytopenia 24 hours after ischemia reperfusion does not influence renal injury, neutrophil infiltration and accumulation of inflammatory chemokines (e.g. keratinocyte chemoattractant, monocyte chemoattractant protein 1, tumor necrosis factor alpha). In the recovery and regeneration phase of I/R injury, respectively 5 and 10 days post-ischemia, thrombocytopenia did also not affect the accumulation of intra-renal neutrophils and macrophages, renal injury, and renal fibrosis. Together, these results imply that lowering platelet counts do not impact the pathogenesis of I/R injury in mice.

Melioidosis in travelers: An analysis of Dutch melioidosis registry data 1985-2018

BACKGROUND

Melioidosis, caused by the Gram-negative bacterium Burkholderia pseudomallei, is an opportunistic infection across the tropics. Here, we provide a systematic overview of imported human cases in a non-endemic country over a 25-year period.

METHODS

All 55 Dutch microbiology laboratories were contacted in order to identify all B. pseudomallei positive cultures from 1990 to 2018. A response rate of 100% was achieved. Additionally, a systematic literature search was performed, medical-charts reviewed, and tissue/autopsy specimens were re-assessed.

RESULTS

Thirty-three travelers with melioidosis were identified: 70% male with a median-age of 54 years. Risk factors were present in most patients (n = 23, 70%), most notably diabetes (n = 8, 24%) and cystic fibrosis (n = 3, 9%). Countries of acquisition included Thailand, Brazil, Indonesia, Panama, and The Gambia. Disease manifestations included pneumonia, intra-abdominal abscesses, otitis externa, genitourinary, skin-, CNS-, and thyroid gland infections. Twelve (36%) patients developed sepsis and/or septic shock. Repeat episodes of active infection were observed in five (15%) and mortality in four (12%) patients. Post-mortem analysis showed extensive metastatic (micro)abscesses amongst other sites in the adrenal gland and bone marrow.

CONCLUSIONS

The number of imported melioidosis is likely to increase, given rising numbers of (immunocompromised) travelers, and increased vigilance of the condition. This first systematic retrospective surveillance study in a non-endemic melioidosis country shows that imported cases can serve as sentinels to provide information about disease activity in areas visited and inform pre-travel advice and post-travel clinical management.

Pulmonary complement depositions in autopsy of critically ill patients have no relation with ARDS

Background

The complement system has frequently been suggested to play a role in the pathophysiology of acute respiratory distress syndrome (ARDS). The current study explored the association between pulmonary depositions of a complement activation product and the clinical diagnosis of ARDS.

Methods

Lung tissue material from autopsied critically ill patients who died whilst on invasively mechanical ventilation was collected and stained for complement C3d. The diagnosis of ARDS was by the Berlin Definition. Lung injury scores (LIS) and driving pressures were calculated, 48 and 24 h prior to death. A pathologist who remained blinded for the clinical data scored the extent of C3d depositions, using a C3d deposition score (a minimum and maximum score of 0 and 24), and of diffuse alveolar damage (DAD). The primary analysis focused on the association between the C3d deposition score and the clinical diagnosis of ARDS. Secondary analyses focused on associations between the C3d deposition score and the presence of diffuse alveolar damage (DAD) in histopathology, and LIS and driving pressures in the last 2 days before death.

Results

Of 36 patients of whom autopsy material was available, 12 were diagnosed as having had ARDS. In all patients, C3d depositions were found in various parts of the lungs, and to a different extent. Notably, C3d deposition scores were similar for patients with ARDS and those without ARDS (4.5 [3.3–6.8] vs. 5.0 [4.0–6.0]; not significant). C3d deposition scores were also independent from the presence or absence of DAD, and correlations between C3d scores and LIS and driving pressures prior to death were poor.

Conclusion

Pulmonary C3d depositions are found in the lungs of all deceased ICU patients, independent of the diagnosis of ARDS. The presence of complement C3d was not associated with the presence of DAD on histopathology and had a poor correlation with ventilation characteristics prior to death.

Use of a high platelet-to-RBC ratio of 2:1 is more effective in correcting trauma-induced coagulopathy than a ratio of 1:1 in a rat multiple trauma transfusion model

Background

Platelet dysfunction importantly contributes to trauma-induced coagulopathy (TIC). Our aim was to examine the impact of transfusing platelets (PLTs) in a 2:1 PLT-to-red blood cell (RBC) ratio versus the standard 1:1 ratio on transfusion requirements, correction of TIC, and organ damage in a rat multiple trauma transfusion model.

Methods

Mechanically ventilated male Sprague Dawley rats were traumatized by crush injury to the small intestine and liver and a fracture of the femur, followed by exsanguination until a mean arterial pressure (MAP) of 40 mmHg. Animals were randomly assigned to receive resuscitation in a high PLT dose (PLT to plasma to RBC in a ratio of 2:1:1) or a standard PLT dose (ratio of 1:1:1) until a MAP of 60 mmHg was reached (n = 8 per group). Blood samples were taken for biochemical and thromboelastometry (ROTEM) assessment. Organs were harvested for histopathology.Outcome measures were transfusion requirements needed to reach a pretargeted MAP, as well as ROTEM correction and organ failure.

Results

Trauma resulted in coagulopathy as assessed by deranged ROTEM results. Mortality rate was 19%, with all deaths occurring in the standard dose group. The severity of hypovolemic shock as assessed by lactate and base excess was not different in both groups. The volume of transfusion needed to reach the MAP target was lower in the high PLT dose group compared to the standard dose, albeit not statistically significant (p = 0.054). Transfusion with a high PLT dose resulted in significant stronger clot firmness compared to the standard dose at all time points following trauma, while platelet counts were similar. Organ failure as assessed by biochemical analysis and histopathology was not different between groups, nor were there any thromboembolic events recorded.

Conclusions

Resuscitation with a high (2:1) PLT-to-RBC ratio was more effective compared to standard (1:1) PLT-to-RBC ratio in treating TIC, with a trend towards reduced transfusion volumes. Also, high PLT dose did not aggravate organ damage. Transfusion strategies using higher PLT dose regiments might be a feasible treatment option in hemorrhaging trauma patients for the correction of TIC.

Complement factor C5 inhibition reduces type 2 responses without affecting group 2 innate lymphoid cells in a house dust mite induced murine asthma model

Background

Complement factor C5 can either aggravate or attenuate the T-helper type 2 (T_H2) immune response and airway hyperresponsiveness (AHR) in murine models of allergic asthma. The effect of C5 during the effector phase of allergen-induced asthma is ill-defined.

Objectives

We aimed to determine the effect of C5 blockade during the effector phase on the pulmonary T_H2 response and AHR in a house dust mite (HDM) driven murine asthma model.

Methods

BALB/c mice were sensitized and challenged repeatedly with HDM via the airways to induce allergic lung inflammation. Sensitized mice received twice weekly injections with a blocking anti-C5 or control antibody 24 h before the first challenge.

Results

HDM challenge in sensitized mice resulted in elevated C5a levels in bronchoalveolar lavage fluid. Anti-C5 administered to sensitized mice prior to the first HDM challenge prevented this rise in C5a, but did not influence the influx of eosinophils or neutrophils. While anti-C5 did not impact the recruitment of CD4 T cells upon HDM challenge, it reduced the proportion of T_H2 cells recruited to the airways, attenuated IL-4 release by regional lymph nodes restimulated with HDM ex vivo and mitigated the plasma IgE response. Anti-C5 did not affect innate lymphoid cell (ILC) proliferation or group 2 ILC (ILC2) differentiation. Anti-C5 attenuated HDM induced AHR in the absence of an effect on lung histopathology, mucus production or vascular leak.

Conclusions

Generation of C5a during the effector phase of HDM induced allergic lung inflammation contributes to T_H2 cell differentiation and AHR without impacting ILC2 cells.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-1136-5) contains supplementary material, which is available to authorized users.

Protease-Activated Receptor 2 Facilitates Bacterial Dissemination in Pneumococcal Pneumonia

Streptococcus pneumoniae is the most common causative pathogen in community-acquired pneumonia. Protease-activated receptor 2 (PAR2) is expressed by different cell types in the lungs and can mediate inflammatory responses. We sought to determine the role of PAR2 during pneumococcal pneumonia. Pneumococcal pneumonia or sepsis was induced in wild-type and PAR2 knock-out (Par2-/-) mice by infection with viable S. pneumoniae. Par2-/- mice demonstrated improved host defense, a largely preserved lung barrier integrity, and reduced mortality during pneumococcal pneumonia. PAR2 deficiency did not influence bacterial growth after intravenous infection. Inhibition of the endogenous PAR2 activating proteases tissue factor/factor VIIa or tryptase did not impact on bacterial burdens during pneumonia. In a PAR2 reporter cell line it was demonstrated that S. pneumoniae-derived proteases are able to cleave PAR2. These results show that S. pneumoniae is able to cleave and exploit PAR2 to disseminate systemically from the airways.

NLRX1 does not play a role in diabetes nor the development of diabetic nephropathy induced by multiple low doses of streptozotocin

Diabetic nephropathy (DN) is a microvascular complication of diabetes mellitus that results in both tubular and glomerular injury. Low-grade inflammation and oxidative stress are two mechanisms known to drive the progression of DN. Nucleotide-binding leucine-rich repeat containing family member X1 (NLRX1) is an innate immune receptor, uniquely located in mitochondria, that has been found to regulate inflammatory responses and to dampen renal oxidative stress by regulating oxidative phosphorylation. For this reason, we investigated the role of NLRX1 in the development of DN in a Type 1 Diabetes mouse model. We analyzed the effect of NLRX1 deficiency on diabetes development and the accompanied renal damage, inflammation, and fibrosis. We found that multiple low doses of streptozotocin induced body weight loss, polydipsia, hyperglycemia, glycosuria, and a mild DN phenotype in wildtype and NLRX1-deficient mice, without significant differences between these mouse strains. Despite increased NLRX1 expression in diabetic wildtype mice, NLRX1 deficiency did not affect the diabetic phenotype induced by streptozotocin treatment, as reflected by similar levels of polyuria, microalbuminuria, and increased renal markers of oxidative stress and inflammation in wildtype and NLRX1-deficient mice. The present findings show that NLRX1 does not mediate the development of streptozotocin-induced diabetes and diabetic-induced nephropathy in mice after multiple low doses of streptozotocin. This data implies that, while NLRX1 can be triggered by cellular stress, its regulatory and functional effects may be dependent on the specific physiological conditions. In the case of DN, NLRX1 may be neither helpful nor harmful, but rather a marker of metabolic stress.

Platelet Btk is Required for Maintaining Lung Vascular Integrity during Murine Pneumococcal Pneumosepsis

Platelet Bruton's tyrosine kinase (Btk) is an essential signalling protein for the collagen receptor glycoprotein VI (GPVI) and podoplanin receptor C-type-lectin-like receptor-2, which are platelet receptors implicated in the maintenance of vascular integrity during inflammation. Moreover, platelets, platelet GPVI and Btk are important for host defence during murine bacterial pneumosepsis. The aim of this study was to determine the role of platelet Btk in vascular integrity and host defence during murine pneumosepsis caused by the common human pathogens Streptococcus pneumoniae and Klebsiella pneumoniae. Using the Cre-loxP system, male platelet-specific Btk-deficient mice (PF4creBtk^fl/Y) were created. Similar to platelets from total Btk-deficient mice, platelets from PF4creBtk^fl/Y mice showed abrogated aggregation and P-selectin expression when stimulated with the GPVI ligand cross-linked collagen-related peptide. Upon infection with S. pneumoniae, PF4creBtk^fl/Y mice showed increased lung bleeding, but unimpaired anti-bacterial defence. During pneumosepsis evoked by K. pneumoniae, platelet Btk deficiency was not associated with lung bleeding and did not impact on host defence, even when platelet function was further compromised by blocking secondary platelet activation by the P2Y₁₂ receptor antagonist clopidogrel. Together, these data indicate that, while platelet Btk is not important for anti-bacterial defence in pneumosepsis, its role in maintaining vascular integrity in the lung depends on the causative pathogen.