Regulation of Glycoprotein VI-Dependent Platelet Activation and Thrombus Formation by Heparan Sulfate Proteoglycan Perlecan

Proteoglycans form a heterogeneous family of proteins with covalently bound sulfated glycosaminoglycans. The extracellular matrix proteoglycan perlecan has been proposed to bind to the platelet- and megakaryocyte-specific receptor G6bB, co-regulating platelet glycoprotein VI (GPVI) signaling. The derived non-sulfate proteoglycan endorepellin was previously shown to enhance platelet adhesion via the collagen receptor, integrin α2β1. Here, we compared the roles of perlecan and other matrix proteoglycans in platelet responses and thrombus formation. We used multi-color flow cytometry to measure the degranulation and integrin αIIbβ3 activation of washed platelets in response to various proteoglycans and collagen-related peptide (CRP), the GPVI agonist. Perlecan, but not endorepellin, enhanced the CRP-induced activation of platelets in a time- and concentration-dependent manner. Similar to collagen, immobilized perlecan, but not other proteoglycans, supported static platelet adhesion and spreading. In-flowed whole-blood perlecan diminished shear-dependent platelet adhesion, while it enforced GPVI-dependent thrombus formation-to a larger extent than endorepellin-to induce more contracted aggregates of activated platelets. We concluded that the sulfated proteoglycan perlecan enhances GPVI-dependent platelet responses extending to thrombus formation, but it does so at the expense of reduced adhesion of platelets under flow.

Evaluation of Semen Self-Sampling Yield Predictors and CTC Isolation by Multi-Color Flow Cytometry for Liquid Biopsy of Localized Prostate Cancer

Liquid biopsy (LB) for prostate cancer (PCa) detection could represent an alternative to biopsy. Seminal fluid (SF) is a source of PCa-specific biomarkers, as 40% of ejaculate derives from the prostate. We tested the feasibility of an SF-based LB by evaluating the yield of semen self-sampling in a cohort of >750 patients with clinically localized PCa. The overall SF collection yield was 18.2% (39% when considering only compliant patients), with about a half of the patients (53.15%) not consenting to SF donation. Independent favorable predictors for SF collection were younger age and lower prostate volume. We implemented a protocol to enrich prostate-derived cells by multi-color flow cytometry and applied it on SF and urine samples from 100 patients. The number of prostate-enriched cells (SYTO-16+ PSMA+ CD45-) was variable, with higher numbers of cells isolated from SF than urine (p value < 0.001). Putative cancer cells (EpCAM^high) were 2% of isolated cells in both specimens. The fraction of EpCAM^high cells over prostate-enriched cells (PSMA+) significantly correlated with patient age in both semen and urine, but not with other clinical parameters, such as Gleason Score, ISUP, or TNM stage. Hence, enumeration of prostate-derived cells is not sufficient to guide PCa diagnosis; additional molecular analyses to detect patient-specific cancer lesions will be needed.

The rate of platelet activation determines thrombus size and structure at arterial shear

BACKGROUND

The response of platelets to activating stimuli and pharmaceutical agents varies greatly within the normal population. Current platelet function tests measure endpoint levels of platelet activation without taking the speed at which platelets activate into account, potentially missing vital metrics to characterise platelet reactivity.

OBJECTIVES

To identify variability, to agonist and between individuals, in platelet activation kinetics and assess the impact of this on thrombus formation.

METHODS

We have developed a bespoke real-time flow cytometry assay and analysis package that measures the rate of platelet activation over time using two parameters of platelet activation, fibrinogen binding and P-selectin exposure.

RESULTS

The rate of platelet activation varied considerably within the normal population but did not correlate with maximal platelet activation, demonstrating that platelet activation rate is a separate and novel metric to describe platelet reactivity. The relative rate of platelet response between agonists was strongly correlated, suggesting a central control mechanism regulates the rate of platelet response to all agonists.

CONCLUSIONS

For the first time, we have shown that platelet response rate corresponds to thrombus size and structure, where faster responders form larger, more densely packed thrombi at arterial, but crucially not venous shear. We have demonstrated that the rate of platelet activation is an important metric in stratifying individual platelet responses and will provide a novel focus for the design and development of anti-platelet therapy, targeting high shear thrombosis without exacerbating bleeding at low shear.

Blood coagulation and beyond: Position paper from the Fourth Maastricht Consensus Conference on Thrombosis

The 4th Maastricht Consensus Conference on Thrombosis (MCCT), included the following themes: Theme 1: The "coagulome" as a critical driver of cardiovascular disease Blood coagulation proteins also play divergent roles in biology and pathophysiology, related to specific organs, including brain, heart, bone marrow and kidney. Four investigators shared their views on these organ-specific topics. Theme 2: Novel mechanisms of thrombosis Mechanisms linking factor XII to fibrin, including their structural and physical properties, contribute to thrombosis, which is also affected by variation in microbiome status. Virus infections associated-coagulopathies perturb the hemostatic balance resulting in thrombosis and/or bleeding. Theme 3: How to limit bleeding risks: insights from translational studies This theme included state of the art methodology for exploring the contribution of genetic determinants of a bleeding diathesis; determination of polymorphisms in genes that control the rate of metabolism by the liver of P2Y12 inhibitors, to improve safety of antithrombotic therapy. Novel reversal agents for direct oral anticoagulants are discussed. Theme 4: Hemostasis in extracorporeal systems: how to utilize ex vivo models? Perfusion flow chamber and nanotechnology developments are developed for studying bleeding and thrombosis tendencies. Vascularised organoids are utilized for disease modeling and drug development studies. Strategies for tackling extracorporeal membrane oxygenation (ECMO) associated coagulopathy are discussed. Theme 5: Clinical dilemmas in thrombosis and antithrombotic management Plenary presentations addressed controversial areas, ie thrombophilia testing, thrombosis risk assessment in hemophilia, novel antiplatelet strategies and clinically tested factor XI(a) inhibitors,both possibly with reduced bleeding risk. Finally, Covid-19 associated coagulopathy is revisited.

Repeated platelet activation and the potential of previously activated platelets to contribute to thrombus formation

BACKGROUND

Especially in disease conditions, platelets can encounter activating agents in circulation.

OBJECTIVES

To investigate the extent to which previously activated platelets can be reactivated and whether in-and reactivation applies to different aspects of platelet activation and thrombus formation.

METHODS

Short-and long-term effects of glycoprotein VI (GPVI) and G protein-coupled receptor (GPCR) stimulation on platelet activation and aggregation potential were compared via flow cytometry and plate-based aggregation. Using fluorescence and electron microscopy, we assessed platelet morphology and content, as well as thrombus formation.

RESULTS

After 30 minutes of stimulation with thrombin receptor activator peptide 6 (TRAP6) or adenosine diphosphate (ADP), platelets secondarily decreased in PAC-1 binding and were less able to aggregate. The reversibility of platelets after thrombin stimulation was concentration dependent. Reactivation was possible via another receptor. In contrast, cross-linked collagen-related peptide (CRP-XL) or high thrombin stimulation evoked persistent effects in α_IIbβ₃ activation and platelet aggregation. However, after 60 minutes of CRP-XL or high thrombin stimulation, when α_IIbβ₃ activation slightly decreased, restimulation with ADP or CRP-XL, respectively, increased integrin activation again. Compatible with decreased integrin activation, platelet morphology was reversed. Interestingly, reactivation of reversed platelets again resulted in shape change and if not fully degranulated, additional secretion. Moreover, platelets that were previously activated with TRAP6 or ADP regained their potential to contribute to thrombus formation under flow. On the contrary, prior platelet triggering with CRP-XL was accompanied by prolonged platelet activity, leading to a decreased secondary platelet adhesion under flow.

CONCLUSION

This work emphasizes that prior platelet activation can be reversed, whereafter platelets can be reactivated through a different receptor. Reversed, previously activated platelets can contribute to thrombus formation.

Prospective evaluation of the role of imaging techniques and TMPRSS2:ERG mutation for the diagnosis of clinically significant prostate cancer

Objectives

To test the hypothesis of a relationship between a specific genetic lesion (T2:ERG) and imaging scores, such as PI-RADS and PRI-MUS, and to test the effectiveness of these parameters for the diagnosis of prostate cancer (PCa) and clinically significant PCa (csPCa).

Materials and methods

This is a prospective study of men with suspected PCa enrolled between 2016 and 2019 at a high-volume tertiary hospital. Patients underwent systematic US-guided biopsy, plus targeted biopsy if they were presenting with >=1 suspicious lesion (PI-RADS>2) at mpMRI or PR-IMUS >2 at micro-ultrasound assessment. For each patient, one core from the highest PI-RADS or PRI-MUS lesion was collected for T2:ERG analysis. Multivariable logistic regression models (LRMs) were fitted for csPCa with a clinical model (age, total PSA, previous biopsy, family history for PCa), a clinical plus PI-RADS, clinical plus T2:ERG, clinical plus PI-RADS plus T2:ERG, and T2:ERG plus PI-RADS alone.

Results

The cohort consists of 158 patients: 83.5% and 66.2% had respectively a diagnosis of PCa and csPCa after biopsy. A T2:ERG fusion was found in 37 men and 97.3% of these patients harbored PCa, while 81.1% were diagnosed with csPCa. SE of T2:ERG assay for csPCa was 28.8%, SP 87.0%, NPV 38.8%, and PPV 81.1%. Of 105 patients who performed mpMRI 93.% had PIRADS ≥3. SE of mpMRI for csPCa was 98.5%, SP was 12.8%, NPV was 83.3%, and PPV was 65.7%. Among 67 patients who were subjected to micro-US, 90% had a PRI-MUS ≥3. SE of micro-US for csPCa was 89.1%, SP was 9.52%, NPV was 28.6%, and PPV was 68.3%. At univariable LRM T2:ERG was confirmed as independent of mpMRI and micro-US result (OR 1.49, p=0.133 and OR 1.82, p=0.592, respectively). At multivariable LRM the clinical model alone had an AUC for csPCa of 0.74 while the clinical model including PI-RADS and T2:ERG achieved an AUC of 0.83.

Conclusions

T2:ERG translocation and imaging results are independent of each other, but both are related csPCa. To evaluate the best diagnostic work-up for PCa and csPCa detection, all available tools (T2:ERG detection and imaging techniques) should be employed together as they appear to have a complementary role.

Coagulation Factor XIIIa and Activated Protein C Activate Platelets via GPVI and PAR1

Platelet and coagulation activation are highly reciprocal processes driven by multi-molecular interactions. Activated platelets secrete several coagulation factors and expose phosphatidylserine, which supports the activation of coagulation factor proteins. On the other hand, the coagulation cascade generates known ligands for platelet receptors, such as thrombin and fibrin. Coagulation factor (F)Xa, (F)XIIIa and activated protein C (APC) can also bind to platelets, but the functional consequences are unclear. Here, we investigated the effects of the activated (anti)coagulation factors on platelets, other than thrombin. Multicolor flow cytometry and aggregation experiments revealed that the ‘supernatant of (hirudin-treated) coagulated plasma’ (SCP) enhanced CRP-XL-induced platelet responses, i.e., integrin α_IIbβ₃ activation, P-selectin exposure and aggregate formation. We demonstrated that FXIIIa in combination with APC enhanced platelet activation in solution, and separately immobilized FXIIIa and APC resulted in platelet spreading. Platelet activation by FXIIIa was inhibited by molecular blockade of glycoprotein VI (GPVI) or Syk kinase. In contrast, platelet spreading on immobilized APC was inhibited by PAR1 blockade. Immobilized, but not soluble, FXIIIa and APC also enhanced in vitro adhesion and aggregation under flow. In conclusion, in coagulation, factors other than thrombin or fibrin can induce platelet activation via GPVI and PAR receptors.

Effects of Platelet Agonists and Priming on the Formation of Platelet Populations

Platelets from healthy donors display heterogeneity in responsiveness to agonists. The response thresholds of platelets are controlled by multiple bioactive molecules, acting as negatively or positively priming substances. Higher circulating levels of priming substances adenosine and succinate, as well as the occurrence of hypercoagulability, have been described for patients with ischaemic heart disease. Here, we present an improved methodology of flow cytometric analyses of platelet activation and the characterisation of platelet populations following activation and priming by automated clustering analysis.Platelets were treated with adenosine, succinate, or coagulated plasma before stimulation with CRP-XL, 2-MeSADP, or TRAP6 and labelled for activated integrin α_IIbβ₃ (PAC1), CD62P, TLT1, CD63, and GPIX. The Super-Enhanced Dmax subtraction algorithm and 2% marker (quadrant) setting were applied to identify populations, which were further defined by state-of-the-art clustering techniques (tSNE, FlowSOM).Following activation, five platelet populations were identified: resting, aggregating (PAC1 + ), secreting (α- and dense-granules; CD62P + , TLT1 + , CD63 + ), aggregating plus α-granule secreting (PAC1 + , CD62P + , TLT1 + ), and fully active platelet populations. The type of agonist determined the distribution of platelet populations. Adenosine in a dose-dependent way suppressed the fraction of fully activated platelets (TRAP6 > 2-MeSADP > CRP-XL), whereas succinate and coagulated plasma increased this fraction (CRP-XL > TRAP6 > 2-MeSADP). Interestingly, a subset of platelets showed a constant response (aggregating, secreting, or aggregating plus α-granule secreting), which was hardly affected by the stimulus strength or priming substances.

Post-Biopsy Cell-Free DNA From Blood: An Open Window on Primary Prostate Cancer Genetics and Biology

Circulating cell-free DNA (ccfDNA), released from normal and cancerous cells, is a promising biomarker for cancer detection as in neoplastic patients it is enriched in tumor-derived DNA (ctDNA). ctDNA contains cancer-specific mutations and epigenetic modifications, which can have diagnostic/prognostic value. However, in primary tumors, and in particular in localized prostate cancer (PCa), the fraction of ctDNA is very low and conventional strategies to study ccfDNA are unsuccessful. Here we demonstrate that prostate biopsy, by causing multiple injuries to the organ, leads to a significant increase in plasma concentration of ccfDNA (P<0.0024) in primary PCa patients. By calculating the minor allele fraction at patient-specific somatic mutations pre- and post-biopsy, we show that ctDNA is significantly enriched (from 3.9 to 164 fold) after biopsy, representing a transient “molecular window” to access and analyze ctDNA. Moreover, we show that newly released ccfDNA contains a larger fraction of di-, tri- and multi-nucleosome associated DNA fragments. This feature could be exploited to further enrich prostate-derived ccfDNA and to analyze epigenetic markers. Our data represent a proof-of-concept that liquid tumor profiling from peripheral blood performed just after the biopsy procedure can open a “valuable molecular metastatic window” giving access to the tumor genetic asset, thus providing an opportunity for early cancer detection and individual genomic profiling in the view of PCa precision medicine.

Clonal hematopoietic mutations linked to platelet traits and the risk of thrombosis or bleeding

Platelets are key elements in thrombosis, particularly in atherosclerosis-associated arterial thrombosis (atherothrombosis), and hemostasis. Megakaryocytes in the bone marrow, differentiated from hematopoietic stem cells are generally considered as a uniform source of platelets. However, recent insights into the causes of malignancies, including essential thrombocytosis, indicate that not only inherited but also somatic mutations in hematopoietic cells are linked to quantitative or qualitative platelet abnormalities. In particular cases, these form the basis of thrombo-hemorrhagic complications regularly observed in patient groups. This has led to the concept of clonal hematopoiesis of indeterminate potential (CHIP), defined as somatic mutations caused by clonal expansion of mutant hematopoietic cells without evident disease. This concept also provides clues regarding the importance of platelet function in relation to cardiovascular disease. In this summative review, we present an overview of genes associated with clonal hematopoiesis and altered platelet production and/or functionality, like mutations in JAK2 We consider how reported CHIP genes can influence the risk of cardiovascular disease, by exploring the consequences for platelet function related to (athero)thrombosis, or the risk of bleeding. More insight into the functional consequences of the CHIP mutations may favor personalized risk assessment, not only with regard to malignancies but also in relation to thrombotic vascular disease.

The low-protein diet for chronic kidney disease: 8 years of clinical experience in a nephrology ward

BACKGROUND

Guidelines indicate that a low-protein diet (LPD) delays dialysis in severe chronic kidney disease (CKD). We assessed the value of these guidelines by performing a retrospective analysis in our renal clinical practice.

METHODS

The analysis was performed from 1 January 2010 to 31 March 2018 in 299 CKD Stage 4 patients followed for 70 months in collaboration with a skilled nutritionist. The patients included 43 patients on a controlled protein diet (CPD) of 0.8 g/kg/day [estimated glomerular filtration rate (eGFR) 20-30 mL/min/1.73 m2 body surface (b.s.)], 171 patients on an LPD of 0.6 g/kg/day and 85 patients on an unrestricted protein diet (UPD) who were not followed by our nutritionist (LPD and UPD, eGFR <20 mL/min/1.73 m2 b.s.).

RESULTS

eGFR was higher in CPD patients than in UPD and LPD patients (21.9 ± 7.4 mL/min/1.73 m2 versus 17.6 ± 8.00 mL/min/1.73 m2 and 17.1 ± 7.5 mL/min/1.73 m2; P = 0.008). The real daily protein intake was higher in UPD patients than in LPD and CDP patients (0.80 ± 0.1 g/kg/day versus 0.6 ± 0.2 and 0.63 ± 0.2 g/kg/day; P = 0.01). Body mass index (BMI) was stable in the LPD and CPD groups but decreased from 28.5 ± 4.52 to 25.4 ± 3.94 kg/m2 in the UPD group (P < 0.001). The renal survival of UPD, LPD and CPD patients was 47.1, 84.3 and 90.7%, respectively, at 30 months (P < 0.001), 42.4, 72.0 and 79.1%, respectively, at 50 months (P < 0.001) and 42.4, 64.1 and 74.4%, respectively, at 70 months (P < 0.001). The LPD patients started dialysis nearly 24 months later than the UPD patients. Diet was an independent predictor of dialysis [-67% of RR reduction (hazard ratio = 0.33; confidence interval 0.22-0.48)] together with a reduction in BMI.

CONCLUSIONS

An LPD recommended by nephrologists in conjunction with skilled dietitians delays dialysis and preserves nutritional status in severe CKD.

Corticosteroid Treatment Influences TA-Proteinuria and Renal Survival in IgA Nephropathy

The clinical course of IgA nephropathy (IgAN) and its outcome are extremely variable. Proteinuria at baseline has been considered one of the most important risk factors. More recently, mean proteinuria of follow-up (time-average proteinuria: TAp) was described as a stronger marker of renal survival, suggesting to consider it as a marker of disease activity and response to treatment. We evaluated predictors of renal survival in IgAN patients with different degrees of renal dysfunction and histological lesions, focusing on the role of the therapy in influencing TAp. We performed a retrospective analysis of three prospective, randomized, clinical trials enrolling 325 IgAN patients from 1989 to 2005. Patients were divided into 5 categories according to TAp. The primary endpoint of the 100% increase of serum creatinine occurred in 54 patients (16.6%) and renal survival was much better in groups having lower TAp. The median follow up was 66.6 months (range 12 to 144). The primary endpoint of the 100% increase of serum creatinine occurred in 54 patients (16,6%) and renal survival was much better in groups having lower TA proteinuria. At univariate analysis plasma creatinine and 24h proteinuria, systolic (SBP) and diastolic (DBP) blood pressure during follow-up and treatment with either steroid (CS) or steroid plus azathioprine (CS+A) were the main factors associated with lower TAp and renal survival. At multivariate analysis, female gender, treatment with S or S+A, lower baseline proteinuria and SBP during follow-up remained as the only variables independently influencing TAp. In conclusion, TA-proteinuria is confirmed as one of the best outcome indicators, also in patients with a severe renal insufficiency. A 6-month course of corticosteroids seems the most effective therapy to reduce TAp.

[Assisted peritoneal dialysis]

Peritoneal dialysis (PD) has a prevalence in Italy that does not exceed 10% of patients in substitution treatment. Among the barriers, which hinder access to DP, the lack of patient autonomy or family support has great importance. In 2012 in Lombardy, the lack of support has prevented 155 new patients to use DP and has forced 17 to stop it. According to the Italian Census of 2012, made by the Peritoneal Dialysis Study Group, Assisted DP involved the 24.5% of patients in 2010. In these cases, the caregiver was a family member in 80.8% of cases, a carer in 12.4%, a homecare nurse in 2.5% and the retirement home staff in 3.9%. In Italy, several regional Governments have sought to encourage home dialysis with economic contributions to the patient or the family. However, so far, none of these interventions has managed to increase the use of DP. In January 2004, we started a program of Assisted PD, using health worker as caregiver, in agreement with ASL Milano and ICP Milano Hospital. In the first 6 months of activity we treated 4 patients, 3 of them had been treated with hemodialysis. We had no critical cases and patients have welcomed this solution. In addition, the costs related to the Assisted PD are lower in comparison with the costs of the hospital hemodialysis. Considering the reliability of the first results, ASL has decided to raise the economic contribution for this activity, allowing us to increase the number of patients to include in Assisted PD.

One-year glargine treatment can improve the course of lung disease in children and adolescents with cystic fibrosis and early glucose derangements

BACKGROUND

Diabetes increases morbidity and mortality in cystic fibrosis (CF) patients, but several studies indicate that also prediabetic status may have a potential impact on both nutrition and lung function.

OBJECTIVE

To evaluate the effect of glargine on the clinical course in CF patients with early glucose derangements.

METHODS

CF population was screened for glucose tolerance. CF patients with age >10 yr were screened with fasting hyperglycemia (FH). CF patients with age >10 yr without FH and those with age <10 yr with occasional FH were evaluated for glucose abnormalities on the basis of oral glucose tolerance test and/or continuous glucose monitoring system. All CF patients with glucose derangements were enrolled in an open clinical trial with glargine. Body mass index (BMI) z-score, forced expiratory volume in the first second (FEV(1)), number of acute pulmonary exacerbations and hemoglobin A1c, were as outcome measures at baseline and after 1 yr of treatment.

RESULTS

After 12 months of therapy, BMI z-score improved only in patients with baseline BMI z-score less than -1 (p = 0.017). An 8.8% increase in FEV(1) (p = 0.01) and 42% decrease in the number of pulmonary exacerbations (p = 0.003) were found in the whole group compared with previous 12 months of therapy.

CONCLUSION

Glargine could represent an innovative strategy to prevent lung disease progression in CF patients with early glucose derangements. Larger controlled trials are needed to better clarify the effects of insulin on clinical status in CF patients with early glucose derangements.

Continuous glucose monitoring system in the screening of early glucose derangements in children and adolescents with cystic fibrosis

BACKGROUND

In cystic fibrosis (CF), diabetes mellitus (DM) is associated with progression of pulmonary disease and nutritional impairment.

AIM

To compare oral glucose tolerance test (OGTT) and continuous glucose monitoring system (CGMS) in patients with CF with early glucose derangements.

PATIENTS AND METHODS

Thirty-two patients with CF (5-20 years) with intermediate glucose values > 7.7 mmol/l during OGTT received a CGMS registration. Patients were classified into those with normal glucose tolerance (NGT), impaired glucose tolerance (IGT) and DM, according to glucose values at 120 min of OGTT and during CGMS. Furthermore BMI z-scores, forced expiratory volume in 1 second (FEV1%), number of respiratory infections/year, enzyme supplementation, and HbA1c were evaluated.

RESULTS

OGTT and CGMS derangements were in agreement in 43.7% of the patients. BMI z-scores, FEV1%, number of respiratory infections/ year, enzyme supplementation, and HbA1c did not differ among the three groups. HbA1c, correlated positively with 120 min OGTT (r = 0.34; p = 0.059), CGMS area (r = 0.35; p = 0.048) and the number of respiratory infections, and negatively with FEV1%.

CONCLUSIONS

Intermediate glucose values during OGTT should be considered as a screening test in patients with CF. CGMS can be useful in studying the early occurrence of glucose derangements in selected patients.