Expanded Haemodialysis Therapy of Chronic Haemodialysis Patients Prevents Calcification and Apoptosis of Vascular Smooth Muscle Cells in vitro

Circulating miR-129-3p in combination with clinical factors predicts vascular calcification in hemodialysis patients

Background

Vascular calcification (VC) commonly occurs and seriously increases the risk of cardiovascular events and mortality in patients with hemodialysis. For optimizing individual management, we will develop a diagnostic multivariable prediction model for evaluating the probability of VC.

Methods

The study was conducted in four steps. First, identification of miRNAs regulating osteogenic differentiation of vascular smooth muscle cells (VSMCs) in calcified condition. Second, observing the role of miR-129-3p on VC in vitro and the association between circulating miR-129-3p and VC in hemodialysis patients. Third, collecting all indicators related to VC as candidate variables, screening predictors from the candidate variables by Lasso regression, developing the prediction model by logistic regression and showing it as a nomogram in training cohort. Last, verifying predictive performance of the model in validation cohort.

Results

In cell experiments, miR-129-3p was found to attenuate vascular calcification, and in human, serum miR-129-3p exhibited a negative correlation with vascular calcification, suggesting that miR-129-3p could be one of the candidate predictor variables. Regression analysis demonstrated that miR-129-3p, age, dialysis duration and smoking were valid factors to establish the prediction model and nomogram for VC. The area under receiver operating characteristic curve of the model was 0.8698. The calibration curve showed that predicted probability of the model was in good agreement with actual probability and decision curve analysis indicated better net benefit of the model. Furthermore, internal validation through bootstrap process and external validation by another independent cohort confirmed the stability of the model.

Conclusion

We build a diagnostic prediction model and present it as an intuitive tool based on miR-129-3p and clinical indicators to evaluate the probability of VC in hemodialysis patients, facilitating risk stratification and effective decision, which may be of great importance for reducing the risk of serious cardiovascular events.

Trial design of the MOTheR HDx study: a multicenter, open-label, prospective, randomized study to explore the morbidity and mortality in patients dialyzed with the Theranova HDx in comparison with online hemodiafiltration

Background

Dialysis patients have been maintaining a high rate of cardiovascular morbidity and mortality. For this reason, it is to introduce necessary new technical advances in clinical practice. There is a relation between toxins retention and inflammation, mortality and morbidity. Medium cut-off (MCO) membranes are a new generation of membranes that allow the removal of a greater number of medium-sized molecules compared with high-flux hemodialysis (HF-HD), but retaining albumin. MCO membranes have an increased permeability and the presence of internal filtration. Because of these special properties, MCO generated a new concept of therapy called expanded HD (HDx). Until now, online hemodiafiltration (OL-HDF) has demonstrated its superiority, in terms of survival, compared with HF-HD. However, the comparison between OL-HDF and HDx remains an unsolved question.

Methods

The MOTheR HDx study trial (NCT03714386) is an open-label, multicenter, prospective, 1:1 randomized, parallel-group trial designed to evaluate the efficacy and safety of HDx compared with OL-HDF in patients treated for dialysis in Spain for up to 36 months. The main endpoint is to determinate whether HDx is non inferior to OL-HDF at reducing the combined outcome of all-cause death and stroke (ischemic or hemorrhagic), acute coronary syndrome (angina and myocardial infarction), peripheral arterial disease (amputation or revascularization) and ischemic colitis (mesenteric thrombosis).

Results

The trial has already started.

Expanded hemodialysis: what's up, Doc?

In recent years there has been an increasing interest in expanded hemodialysis (HDx), an emerging renal replacement therapy based on the use of medium cut-off membranes (MCO). Thanks to the internal architecture of these types of membranes, with a higher pore size and smaller fiber inner diameter to favor internal filtration rate, they can increase the removal of larger middle molecules in conventional hemodialysis. Secondarily, several reports suggest that this therapy potentially improve the outcomes for end-stage renal disease patients. However, HDx has not been defined yet and the characteristics of MCO membranes are not well stablished. The aim of this narrative review is to define HDx and summarize the dialyzers that have been used so far to perform this therapy, collect the evidence available on its efficacy and clinical outcomes compared with other hemodialysis techniques and settle the bases for its optimal prescription.

Systematic review to compare the outcomes associated with the modalities of expanded hemodialysis (HDx) versus high-flux hemodialysis and/or hemodiafiltration (HDF) in patients with end-stage kidney disease (ESKD)

BACKGROUND

This systematic review was performed to identify recent published comparative evidence on the efficacy, effectiveness, and safety of expanded hemodialysis (HDx) versus high-flux HD and/or hemodiafiltration (HDF) for long-term outcomes in end-stage kidney disease.

METHODS

Systematic literature review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. Medline, Medline® Epub Ahead of Print, EconLit, Embase, and EBM reviews were searched to identify relevant publications from 2013 onwards. Eligibility criteria included clinical studies reporting mortality, hospitalizations, cardiovascular outcomes, economic evaluations, cost studies, and quality of life (QoL) studies.

RESULTS

A total of 79 relevant studies were identified with 29 prioritized for detailed analysis; four compared HDx to HD, one compared HDF and HDx, and 24 compared HDF with HD. A total of 13 randomized controlled trial (RCT)-based studies were identified; 11 compared HDF with HD, one compared HDx with HD, and one compared HDF with HDx. Follow-up duration ranged from 16 weeks to 7 years for HDF studies and from 12 weeks to 1 year for HDx studies. HDF showed significant improvements in mortality, cardiovascular outcomes, hospitalizations, and QoL versus high-flux HD. One study reported mortality outcomes for HDx and found no difference versus HDF. QoL benefits with HDx were reported in a small number of studies.

CONCLUSION

The efficacy and safety of HDF is supported by a robust evidence base that includes several RCTs. While HDx may offer benefits over high-flux HD, long-term studies are required to compare HDx with online high volume HDF.

REGISTRATION

PROSPERO registration number: CRD42022301009.

Effects of Expanded Hemodialysis with Medium Cut-Off Membranes on Maintenance Hemodialysis Patients: A Review

Kidney failure is associated with high morbidity and mortality. Hemodialysis, the most prevalent modality of renal replacement therapy, uses the principle of semipermeable membranes to remove solutes and water in the plasma of patients with kidney failure. With the evolution of hemodialysis technology over the last half century, the clearance of small water-soluble molecules in such patients is adequate. However, middle molecules uremic toxins are still retained in the plasma and cause cardiovascular events, anemia, and malnutrition, which significantly contribute to poor quality of life and high mortality in maintenance hemodialysis patients. A new class of membrane, defined as a medium cut-off (MCO) membrane, has emerged in recent years. Expanded hemodialysis with MCO membranes is now recognized as the artificial kidney model closest to natural kidney physiology. This review summarizes the unique morphological characteristics and internal filtration–backfiltration mechanism of MCO membranes, and describes their effects on removing uremic toxins, alleviating inflammation and cardiovascular risk, and improving quality of life in maintenance hemodialysis patients.

Expanded Haemodialysis as a Current Strategy to Remove Uremic Toxins

Chronic kidney disease (CKD) is characterized by the retention of solutes named uremic toxins, which strongly associate with high morbidity and mortality. Mounting evidence suggests that targeting uremic toxins and/or their pathways may decrease the risk of cardiovascular disease in CKD patients. Dialysis therapies have been developed to improve removal of uremic toxins. Advances in our understanding of uremic retention solutes as well as improvements in dialysis membranes and techniques (HDx, Expanded Hemodialysis) will offer the opportunity to ameliorate clinical symptoms and outcomes, facilitate personalized and targeted dialysis treatment, and improve quality of life, morbidity and mortality.

The coincidence of low vitamin K status and high expression of growth differentiation factor 15 may indicate increased mortality risk in stable coronary heart disease patients

BACKGROUND AND AIMS

Matrix Gla protein (MGP) is a natural inhibitor of vascular calcification critically dependent on circulating vitamin K status. Growth differentiation factor 15 (GDF-15) is a regulatory cytokine mainly of the inflammatory and angiogenesis pathways, but potentially also involved in bone mineralization. We sought to determine whether these two circulating biomarkers jointly influenced morbidity and mortality risk in patients with chronic coronary heart disease (CHD).

METHODS AND RESULTS

894 patients ≥6 months after myocardial infarction and/or coronary revascularization at baseline were followed in a prospective study. All-cause and cardiovascular mortality, non-fatal cardiovascular events (myocardial infarction, stroke, any revascularization), and hospitalization for heart failure (HF) were followed as outcomes. Desphospho-uncarboxylated MGP (dp-ucMGP) was used as a biomarker of vitamin K status. Both, increased concentrations of dp-ucMGP (≥884 pmol/L) and GDF-15 (≥1339 pg/mL) were identified as independent predictors of 5-year all-cause or cardiovascular mortality. However, their coincidence further increased mortality risk. The highest risk was observed in patients with high dp-ucMGP plus high GDF-15, not only when compared with those with "normal" concentrations of both biomarkers [HR 5.51 (95% CI 2.91-10.44), p < 0.0001 and 6.79 (95% CI 3.06-15.08), p < 0.0001 for all-cause and cardiovascular mortality, respectively], but even when compared with patients with only one factor increased. This pattern was less convincing with non-fatal cardiovascular events or hospitalization for HF.

CONCLUSIONS

The individual coincidence of low vitamin K status (high dp-ucMGP) and high GDF-15 expression predicts poor survival of stable CHD patients.

High cut-off dialysis mitigates pro-calcific effects of plasma on vascular progenitor cells

Mortality of patients with end-stage renal disease tremendously exceeds that of the general population due to excess cardiovascular morbidity. Large middle-sized molecules (LMM) including pro-inflammatory cytokines are major drivers of uremic cardiovascular toxicity and cannot be removed sufficiently by conventional high-flux (HFL) hemodialysis. We tested the ability of plasma from 19 hemodialysis patients participating in a trial comparing HFL with high cut-off (HCO) membranes facilitating removal of LMM to induce calcification in mesenchymal stromal cells (MSC) functioning as vascular progenitors. HCO dialysis favorably changed plasma composition resulting in reduced pro-calcific activity. LMM were removed more effectively by HCO dialysis including FGF23, a typical LMM we found to promote osteoblastic differentiation of MSC. Protein-bound uremic retention solutes with known cardiovascular toxicity but not LMM inhibited proliferation of MSC without direct toxicity in screening experiments. We could not attribute the effect of HCO dialysis on MSC calcification to distinct mediators. However, we found evidence of sustained reduced inflammation that might parallel other anti-calcifying mechanisms such as altered generation of extracellular vesicles. Our findings imply protection of MSC from dysfunctional differentiation by novel dialysis techniques targeted at removal of LMM. HCO dialysis might preserve their physiologic role in vascular regeneration and improve outcomes in dialysis patients.

Role of Uremic Toxins in Early Vascular Ageing and Calcification

In patients with advanced chronic kidney disease (CKD), the accumulation of uremic toxins, caused by a combination of decreased excretion secondary to reduced kidney function and increased generation secondary to aberrant expression of metabolite genes, interferes with different biological functions of cells and organs, contributing to a state of chronic inflammation and other adverse biologic effects that may cause tissue damage. Several uremic toxins have been implicated in severe vascular smooth muscle cells (VSMCs) changes and other alterations leading to vascular calcification (VC) and early vascular ageing (EVA). The above mentioned are predominant clinical features of patients with CKD, contributing to their exceptionally high cardiovascular mortality. Herein, we present an update on pathophysiological processes and mediators underlying VC and EVA induced by uremic toxins. Moreover, we discuss their clinical impact, and possible therapeutic targets aiming at preventing or ameliorating the harmful effects of uremic toxins on the vasculature.

Pro-calcifying analysis of uraemic serum from patients treated with medium cut-off membrane in a prospective, cross-over study

Background

The retention of a large number of solutes that are normally excreted or metabolized by the kidney is responsible for the symptoms typical in uraemic patients. These molecules are defined as uraemic toxins and can be classified into three groups: small water-soluble molecules, middle molecules and protein-bound toxins. Recently, efforts were put towards developing dialysis membranes that allow the removal of large middle molecules without clinically relevant albumin loss. These membranes are the medium cut-off (MCO) membranes that allow the removal of middle molecules up to ∼50 000 Da.

Methods

We performed a prospective, open-label, controlled, cross-over pilot study comparing expanded haemodialysis (HDx) (novel MCO membrane Theranova 400) and conventional haemodialysis (HD) in 20 prevalent HD patients. Ten patients used conventional HD high-flux dialyser and 10 patients used HDx for 3 months; later the patients switched and received the other treatment for a further 3 months. We then analysed the pro-calcifying effect of uraemic serum in a model of high phosphate(Pi)-induced calcification in vascular smooth muscle cells (VSMCs).

Results

In this study, every patient was the control of himself and, interestingly, we found a tendency of less pro-calcifying potential from HDx-treated patients' serum compared with HD. Studying pathogenetic processes involved in high Pi-induced calcium deposition, we found that uraemic serum of HDx-treated patients induced less VSMC necrosis compared with uraemic serum of HD patients. Nevertheless, no differences were found between the different dialytic treatments in the serum potential to induce apoptosis and to modulate the expression of a panel of genes involved in VSMC simil-osteoblastic differentiation such as bone morphogenetic protein 2, runt-related transcription factor 2, osteocalcin, matrix Gla protein, osteopontin, elastin and collagen I α1. In an effort to characterize the difference in uraemic toxin profile during the two different dialytic treatments, we measured a panel of 10 uraemic toxins and 3 precursors, finding a significant increased removal during HDx of 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid, tryptophane and some of its metabolites, such as 3-indoxyl sulphate, indole 3-acetic acid and kynurenine.

Conclusions

These preliminary data are promising, although larger patients' groups are needed to better understand the effects of HDx on vascular calcification.

High-volume online haemodiafiltration treatment and outcome of end-stage renal disease patients: more than one mode

The reduction of the dismally high mortality of current end-stage renal disease patients maintained on conventional standard haemodialysis (HD) remains an unmet medical need. Online haemodiafiltration (HDF) modes with various sites of fluid substitution (post-, pre-, mixed- and mid-dilution) are increasingly used worldwide as promising alternatives to conventional HD. Large scale cohort studies, post hoc analyses of randomized trials, and individual participant meta-analyses suggest that post-dilution and pre-dilution, especially with high substitution volumes, improve outcomes compared with conventional standard HD. However, there is no definitive proof of a survival advantage of HDF over standard HD. The different modes of high-volume HDF should be considered a therapeutic platform allowing to personalize and tailor routine HDF treatment. The selection of the HDF mode should be made according to individual patient characteristics. Utilizing high retention onset membranes, expanded haemodialysis (HDx) can achieve the same solute removal performance as HDF. Subgroups of high-volume OL-HDF patients could benefit from HDx. Ongoing and future trials should provide definitive proof for the superiority of high-volume OL-HDF over conventional HD or HDx to give guidance for the most favourable mode of dialytic therapy for clinical use.

Expanded haemodialysis: from operational mechanism to clinical results

Recent advances in chemical composition and new production techniques resulted in improved biocompatibility and permeability of dialysis membranes. Among these, the creation of a new class of membranes called medium cut-off (MCO) represents an important step towards improvement of clinical outcomes. Such membranes have been developed to improve the clearance of medium to high molecular weight (MW) solutes (i.e. uraemic toxins in the range of 5–50 kDa). MCO membranes have peculiar retention onset and cut-off characteristics. Due to a modified sieving profile, MCO membranes have also been described as high-retention onset. The significant internal filtration achieved in MCO haemodialysers provides a remarkable convective clearance of medium to high MW solutes. The marginal loss of albumin observed in MCO membranes compared with high cut-off membranes is considered acceptable, if not beneficial, producing a certain clearance of protein-bound solutes. The application of MCO membranes in a classic dialysis modality characterizes a new technique called expanded haemodialysis. This therapy does not need specific software or dedicated hardware, making its application possible in every setting where the quality of dialysis fluid meets current standards.

Vitamin K Dependent Proteins in Kidney Disease

Patients with chronic kidney disease (CKD) have an increased risk of developing vascular calcifications, as well as bone dynamics impairment, leading to a poor quality of life and increased mortality. Certain vitamin K dependent proteins (VKDPs) act mainly as calcification inhibitors, but their involvement in the onset and progression of CKD are not completely elucidated. This review is an update of the current state of knowledge about the relationship between CKD and four extrahepatic VKDPs: matrix Gla protein, osteocalcin, growth-arrest specific protein 6 and Gla-rich protein. Based on published literature in the last ten years, the purpose of this review is to address fundamental aspects about the link between CKD and circulating VKDPs levels as well as to raise new topics about how the interplay between molecular weight and charge could influence the modifications of circulating VKDPs at the glomerular level, or whether distinct renal etiologies have effect on VKDPs. This review is the output of a systematic literature search and may open future research avenues in this niche domain.