Markers of the Endothelial Glycocalyx Are Improved following Kidney Transplantation

Syndecan-1 in the Serum of Deceased Kidney Donors as a Potential Biomarker of Kidney Function

BACKGROUND

The process of kidney transplantation remains the optimal treatment for end-stage renal disease, offering improved quality of life and increased survival rates compared to long-term dialysis. However, despite advances in surgical techniques, immunosuppression regimens, and post-operative care, there are still significant challenges in predicting the organ's status and long-term outcomes of transplantation. Among the many factors that influence graft survival, the quality of the donated organ plays a fundamental role. There is an ongoing need for accurate and reliable biomarkers. Syndecan-1 is found in the endothelial glycocalyx and shed at a higher rate into the blood during systemic pathological conditions. The aim of this study is to evaluate the potential of serum syndecan-1 levels as a biomarker for assessing donor kidney quality and to investigate its correlation with donor characteristics and short-term outcomes in kidney recipients.

MATERIAL AND METHODS

We investigated serum syndecan-1 levels in 80 deceased donors and correlated them with donor characteristics and short-term outcomes (defined as delayed graft function - defined as the need for dialysis within the first week post-transplantation and renal function at 3 months post-transplantation - assessed using serum creatinine levels) in 104 corresponding kidney recipients. This single-center retrospective observational cohort study was conducted from April to December 2021.

RESULTS

The donor pool consisted of 65% males with a median age of 53 years. Of these, 45 donors (56%) were classified as extended criteria donors. Higher syndecan-1 levels correlated with the last creatinine levels before organ procurement (R = 0.32, p = 0.01) and were marginally higher in donors with acute kidney injury (p = 0.07). However, syndecan-1 levels were not associated with short-term outcomes in kidney recipients (renal function at 3 months).

CONCLUSIONS

The data suggests syndecan-1 could be a potential biomarker for assessing donor kidney quality, although its implications on recipient outcomes require further study. This pilot investigation underscores the importance of syndecan-1 in evaluating organ quality but highlights the necessity for more extensive research to validate these findings and explore their implications in transplant success.

VASCULAR ENDOTHELIAL DYSFUNCTION IMPROVEMENTS IN PATIENTS WITH UREMIA USING PENTOXIFYLLINE-SUPPRESSING NLRP3 EXPRESSIONS AND HMGB1 RELEASE

ABSTRACT

This study aimed to investigate the protective effect of pentoxifylline (PTX) on vascular endothelial dysfunction in uremia. The human aortic endothelial cells (HAECs) required for the experiments were all obtained from the National Collection of Authenticated Cell Cultures (Salisbury, UK). The permeability of HAECs was assessed. Each group had six samples. Compared with the healthy volunteer group, HAEC proliferation in the 20% uremia group was significantly inhibited after 72 h ( P < 0.001), co-localization of nucleotide-binding domain, leucine-rich repeat-containing receptor family pyrin domain-containing 3 (NLRP3) and apoptosis-associated speck-like (ASC) protein induced by uremic serum was enhanced ( P < 0.01) and high mobility group box 1 (HMGB1) release was increased (0.594 ± 0.057, P = 0.03). The co-immunoprecipitation of NLRP3, ASC, and HMGB1 induced by uremic toxin was also enhanced ( P < 0.01), and PTX inhibited this phenomenon. The expression of NLRP3 (0.810 ± 0.032, P = 0.02) and caspase-1 (0.580 ± 0.041, P = 0.03) was increased, whereas the expression of ZO-1 (0.255 ± 0.038, P = 0.03) and VE-cadherin (0.0546 ± 0.053, P = 0.02) was decreased in the uremia group; compared with the healthy volunteer group, treated with PTX (NLRP3, 0.298 ± 0.042, P = 0.03; caspase-1, 0.310 ± 0.021, P = 0.03; ZO-1, 0.412 ± 0.028, P = 0.02; VE-cadherin, 0.150 ± 0.034, P = 0.02) and MCC950 (NLRP3, 0.432 ± 0.022, P = 0.03; caspase-1, 0.067 ± 0.031, P > 0.05; ZO-1, 0.457 ± 0.026, P = 0.03; VE-cadherin, 0.286 ± 0.017, P = 0.03) these lessened this trend. Pentoxifylline promoted the HAEC permeability mediated by uremic toxins (1.507 ± 0.012, P = 0.02). In conclusion, PTX enhances the release of HMGB1, which is dependent on NLRP3 activation, and consequently exerts positive effects on interconnecting proteins, ultimately leading to an improvement in vascular permeability.

Kidney Transplant Recipients Show Limited Lung Diffusion Capacity but Similar Hydrogen Peroxide Exhalation as Healthy Matched Volunteers: A Pilot Study

Patients with end-stage chronic kidney disease show higher systemic oxidative stress and exhale more hydrogen peroxide (H2O2) than healthy controls. Kidney transplantation reduces oxidative stress and H2O2 production by blood polymorphonuclear leukocytes (PMNs). Kidney transplant recipients (KTRs) may be predisposed to an impairment of lung diffusing capacity due to chronic inflammation. Lung function and H2O2 concentration in the exhaled breath condensate (EBC) were compared in 20 KTRs with stable allograft function to 20 healthy matched controls. Serum interleukin eight (IL-8) and C-reactive protein (CRP), blood cell counts, and spirometry parameters did not differ between groups. However, KTRs showed lower total lung diffusing capacity for carbon monoxide, corrected for hemoglobin concentration (TLCOc), in comparison to healthy controls (92.1 ± 11.5% vs. 102.3 ± 11.9% of predicted, p = 0.009), but similar EBC H2O2 concentration (1.63 ± 0.52 vs. 1.77 ± 0.50 µmol/L, p = 0.30). The modality of pre-transplant renal replacement therapy had no effect on TLCOc and EBC H2O2. TLCOc did not correlate with time after transplantation. In this study, TLCOc was less reduced in KTRs in comparison to previous reports. We suggest this fact and the non-elevated H2O2 exhalation exhibited by KTRs, may result perhaps from the evolution of the immunosuppressive therapy.

The Role of Pre- and Post-Transplant Hydration Status in Kidney Graft Recovery and One-Year Function

Background and Objectives: Early improvements to graft function are crucial for good outcomes in kidney transplantation (kTx). Various factors can influence early graft function. This study aimed to evaluate the pre- and post-transplant hydration statuses of kTx recipients using bioimpedance analysis (BIA) and lung ultrasonography (LUS) and to investigate the hydration status' relationship with the function of the transplanted kidney during the first year after transplantation. Materials and Methods: This observational prospective cohort study included deceased kidney recipients transplanted in the Hospital of the Lithuanian University of Health Sciences between September 2016 and January 2023. BIA and LUS were performed before transplantation, on days 3 and 7, and at discharge. Data on recipient and donor clinical characteristics were collected. Graft function was evaluated according to the serum creatinine reduction ratio and the need for dialysis. Hydration status was evaluated by calculating B-lines (BL) on LUS and the ratio of extracellular/total body water on BIA. Results: Ninety-eight kTx recipients were included in the study. Patients with immediate graft function (IGF) were compared to those with slow or delayed graft function (SGF + DGF). Recipients in the SGF + DGF group had a higher sum of BL on LUS before transplantation. After transplantation in early postoperative follow-up, both groups showed hyperhydration as determined by BIA and LUS. After one year, recipients with no BL before transplantation had better graft function than those with BL. Logistic regression analysis showed that having more than one BL in LUS was associated with a 2.5 times higher risk of SGF or DGF after transplantation. Conclusions: This study found that lung congestion detected by LUS before kTx was associated with slower graft recovery and worse kidney function after 1 year. Meanwhile, the hyperhydration status detected by BIA analysis did not correlate with the function of the transplanted kidney.

Plasma glycocalyx pattern: a mirror of endothelial damage in chronic kidney disease

Background

Endothelial damage and cardiovascular disease complicate chronic kidney disease (CKD). The increased atherogenicity observed in patients with CKD can be linked to microinflammation and endothelial damage. Circulating endothelial glycocalyx degradation products, such as perlecan and decorin, tend to be elevated in CKD. We aimed to explore the association between the plasma perlecan and decorin levels and this pro-inflammatory and atherogenic state by studying monocyte subpopulations and intracellular adhesion molecule (ICAM)-1 expression in patients with CKD.

Methods

We studied 17 healthy controls, 23 patients with advanced CKD, 25 patients on haemodialysis, 23 patients on peritoneal dialysis and 20 patients who underwent kidney transplantation. Perlecan and decorin levels were evaluated using enzyme-linked immunosorbent assays, and the monocyte phenotype was analysed using direct immunofluorescence and flow cytometry.

Results

The plasma perlecan levels were higher in patients with CKD than in the healthy controls. These levels were associated with a higher prevalence of ICAM-1+ monocytes. Conversely, patients with advanced CKD (pre-dialysis) had higher plasma decorin levels, which were associated with a reduced ICAM-1 expression per monocyte.

Conclusions

Elevated perlecan levels in CKD may be associated with a higher prevalence of ICAM-1+ monocytes and a pro-inflammatory phenotype. Elevated decorin levels may act as a negative regulator of ICAM-1 expression in monocytes. Therefore, perlecan and decorin may be related to inflammation and monocyte activation in CKD and may act as potential markers of endothelial damage.

Endothelial Cell Dysfunction and Increased Cardiovascular Risk in Patients With Chronic Kidney Disease

The endothelium is considered to be the gatekeeper of the vessel wall, maintaining and regulating vascular integrity. In patients with chronic kidney disease, protective endothelial cell functions are impaired due to the proinflammatory, prothrombotic and uremic environment caused by the decline in kidney function, adding to the increase in cardiovascular complications in this vulnerable patient population. In this review, we discuss endothelial cell functioning in healthy conditions and the contribution of endothelial cell dysfunction to cardiovascular disease. Further, we summarize the phenotypic changes of the endothelium in chronic kidney disease patients and the relation of endothelial cell dysfunction to cardiovascular risk in chronic kidney disease. We also review the mechanisms that underlie endothelial changes in chronic kidney disease and consider potential pharmacological interventions that can ameliorate endothelial health.

Microvascular perfusion, perfused boundary region and glycocalyx shedding in patients with autosomal dominant polycystic kidney disease: results from the GlycoScore III study

Background

Vascular abnormalities and endothelial dysfunction are part of the spectrum of autosomal dominant polycystic kidney disease (ADPKD). The mechanisms behind these manifestations, including potential effects on the endothelial surface layer (ESL) and glycocalyx integrity, remain unknown.

Methods

Forty-five ambulatory adult patients with ADPKD were enrolled in this prospective, observational, cross-sectional, single-centre study. Fifty-one healthy volunteers served as a control group. All participants underwent real-time microvascular perfusion measurements of the sublingual microcirculation using sidestream dark field imaging. After image acquisition, the perfused boundary region (PBR), an inverse parameter for red blood cell (RBC) penetration into the ESL, was automatically calculated. Microvascular perfusion was assessed by RBC filling and capillary density. Concentrations of circulating glycocalyx components were determined by enzyme-linked immunosorbent assay.

Results

ADPKD patients showed a significantly larger PBR compared with healthy controls (2.09 ± 0.23 µm versus 1.79 ± 0.25 µm; P < .001). This was accompanied by significantly lower RBC filling (70.4 ± 5.0% versus 77.9 ± 5.4%; P < .001) as well as a higher valid capillary density {318/mm² [interquartile range (IQR) 269-380] versus 273/mm² [230-327]; P = .007}. Significantly higher plasma concentrations of heparan sulphate (1625 ± 807 ng/ml versus 1329 ± 316 ng/ml; P = .034), hyaluronan (111 ng/ml [IQR 79-132] versus 92 ng/ml [82-98]; P = .042) and syndecan-1 were noted in ADPKD patients compared with healthy controls (35 ng/ml [IQR 27-57] versus 29 ng/ml [23-42]; P = .035).

Conclusions

Dimensions and integrity of the ESL are impaired in ADPKD patients. Increased capillary density may be a compensatory mechanism for vascular dysfunction to ensure sufficient tissue perfusion and oxygenation.

Updated Pathways in Cardiorenal Continuum after Kidney Transplantation

Cardiovascular disease (CVD) remains one of the leading causes for increased morbidity and mortality in chronic kidney disease (CKD). Kidney transplantation is the preferred treatment option for CKD G5. Improved perioperative and postoperative care, personalized immunosuppressive regimes, and refined matching procedures of kidney transplants improves cardiovascular health in the early posttransplant period. However, the long-term burden of CVD is considerable. Previously underrecognized, the role of the complement system alongside innate immunity, inflammaging, structural changes in the glomerular filtration barrier and early vascular ageing also seem to play an important role in the posttransplant management. This review provides up-to-date knowledge on these pathways that may influence the cardiovascular and renal continuum and identifies potential targets for future therapies. Arterial destiffening strategies and the applicability of sodium-glucose cotransporter 2 inhibitors and their role in cardiovascular health after kidney transplantation are also addressed.

The Glomerular Endothelium Restricts Albumin Filtration

Inflammatory activation and/or dysfunction of the glomerular endothelium triggers proteinuria in many systemic and localized vascular disorders. Among them are the thrombotic microangiopathies, many forms of glomerulonephritis, and acute inflammatory episodes like sepsis and COVID-19 illness. Another example is the chronic endothelial dysfunction that develops in cardiovascular disease and in metabolic disorders like diabetes. While the glomerular endothelium is a porous sieve that filters prodigious amounts of water and small solutes, it also bars the bulk of albumin and large plasma proteins from passing into the glomerular filtrate. This endothelial barrier function is ascribed predominantly to the endothelial glycocalyx with its endothelial surface layer, that together form a relatively thick, mucinous coat composed of glycosaminoglycans, proteoglycans, glycolipids, sialomucins and other glycoproteins, as well as secreted and circulating proteins. The glycocalyx/endothelial surface layer not only covers the glomerular endothelium; it extends into the endothelial fenestrae. Some glycocalyx components span or are attached to the apical endothelial cell plasma membrane and form the formal glycocalyx. Other components, including small proteoglycans and circulating proteins like albumin and orosomucoid, form the endothelial surface layer and are bound to the glycocalyx due to weak intermolecular interactions. Indeed, bound plasma albumin is a major constituent of the endothelial surface layer and contributes to its barrier function. A role for glomerular endothelial cells in the barrier of the glomerular capillary wall to protein filtration has been demonstrated by many elegant studies. However, it can only be fully understood in the context of other components, including the glomerular basement membrane, the podocytes and reabsorption of proteins by tubule epithelial cells. Discovery of the precise mechanisms that lead to glycocalyx/endothelial surface layer disruption within glomerular capillaries will hopefully lead to pharmacological interventions that specifically target this important structure.