Glomerular mesangial cell adhesion to fibrinogen is mediated by αvβ3 integrin

The Perspective of Vitamin D on suPAR-Related AKI in COVID-19

The coronavirus disease 2019 (COVID-19) pandemic has claimed the lives of millions of people around the world. Severe vitamin D deficiency can increase the risk of death in people with COVID-19. There is growing evidence that acute kidney injury (AKI) is common in COVID-19 patients and is associated with poorer clinical outcomes. The kidney effects of SARS-CoV-2 are directly mediated by angiotensin 2-converting enzyme (ACE2) receptors. AKI is also caused by indirect causes such as the hypercoagulable state and microvascular thrombosis. The increased release of soluble urokinase-type plasminogen activator receptor (suPAR) from immature myeloid cells reduces plasminogen activation by the competitive inhibition of urokinase-type plasminogen activator, which results in low plasmin levels and a fibrinolytic state in COVID-19. Frequent hypercoagulability in critically ill patients with COVID-19 may exacerbate the severity of thrombosis. Versican expression in proximal tubular cells leads to the proliferation of interstitial fibroblasts through the C3a and suPAR pathways. Vitamin D attenuates the local expression of podocyte uPAR and decreases elevated circulating suPAR levels caused by systemic inflammation. This decrease preserves the function and structure of the glomerular barrier, thereby maintaining renal function. The attenuated hyperinflammatory state reduces complement activation, resulting in lower serum C3a levels. Vitamin D can also protect against COVID-19 by modulating innate and adaptive immunity, increasing ACE2 expression, and inhibiting the renin-angiotensin-aldosterone system. We hypothesized that by reducing suPAR levels, appropriate vitamin D supplementation could prevent the progression and reduce the severity of AKI in COVID-19 patients, although the data available require further elucidation.

General sites of nanoparticle biodistribution as a novel opportunity for nanomedicine

The development of nanomedical devices has led to a considerable number of clinically applied nanotherapeutics. Yet, the overall poor translation of nanoparticular concepts into marketable systems has not met the initial expectations and led to increasing criticism in recent years. Most novel nano approaches thereby use highly refined formulations including a plethora of active targeting sequences, but ultimately fail to reach their target due to a generally high off-target deposition in organs such as the liver or kidney. In this context, we argue that initial nanoparticle (NP) development should not entirely become set on conventional formulation aspects. In contrast, we propose a change of focus towards a prior analysis of general sites of NP in vivo deposition and an assessment of how accumulation in these organs or tissues can be harnessed to develop therapies for site-related pathologies. We therefore give a comprehensive overview of existing nanotherapeutic targeting strategies for specific cell types within three of the usual suspects, i.e. the liver, kidney and the vascular system. We discuss the physiological surroundings and relevant pathologies of described tissues as well as the implications for NP-mediated drug delivery. Additionally, successful cell-selective NP concepts using active targeting strategies are assessed. By bringing together both (patho)physiological aspects and concepts for cell-selective NP formulations, we hope to show a novel opportunity for the development of more promising nanotherapeutic devices.

Elevated serum fibrinogen level is an independent risk factor for IgA nephropathy

Background

IgA nephropathy is a primary cause of renal failure, and inflammation and renal fibrosis are the main mechanisms leading to kidney damage. The serum fibrinogen level is closely related to inflammatory states, but its relationship to the prognosis of IgA nephropathy (IgAN) is unclear.

Materials and Methods

1053 patients diagnosed with IgAN after renal biopsy were enrolled from two Nephrology Departments. Demographic and clinical data and histopathological features were collected. The patients were divided into four groups (Q1–Q4) according to the serum fibrinogen levels at the time of renal biopsy, and the relationships of serum fibrinogen levels with other risk factors and the prognosis of IgAN were investigated.

Results

672 patients with proven primary IgAN were included in this study, which included a median follow-up of 36 months. Patients with higher serum fibrinogen levels had elevated serum creatinine levels, 24-hour urinary protein, and blood pressure compared with patients with the lowest levels of serum fibrinogen as well as severe renal damage at the time of renal biopsy. Univariate and multivariate Cox regression analyses confirmed that the serum fibrinogen level at the time of renal biopsy was significantly related to the prognosis of patients with IgAN.

Conclusions

In patients with IgAN, an elevated serum fibrinogen level at the time of renal biopsy is associated with poor renal outcomes, which suggests the need for more aggressive early interventions. Greater benefits of aggressive treatments were observed in patients with higher serum fibrinogen levels.

Kidney podocytes as specific targets for cyclo(RGDfC)-modified nanoparticles

Renal nanoparticle passage opens the door for targeting new cells like podocytes, which constitute the exterior part of the renal filter. When cyclo(RGDfC)-modified Qdots are tested on isolated primary podocytes for selective binding to the αvβ3 integrin receptor a highly cell- and receptor-specific binding can be observed. In displacement experiments with free cyclo(RGDfC) IC(50) values of 150 nM for αvβ3 integrin over-expressing U87-MG cells and 60 nM for podocytes are measured. Confocal microscopy shows a cellular Qdot uptake into vesicle-like structures. Our ex vivo study gives clear evidence that, after renal filtration, nanoparticles can be targeted to podocyte integrin receptors in the future. This could be a highly promising approach for future therapy and diagnostics of podocyte-associated diseases.

Serial non-invasive monitoring of renal disease following immune-mediated injury using near-infrared optical imaging

BACKGROUND

Non-invasive monitoring of disease progression in kidney disease is still a major challenge in clinical practice. In vivo near-infrared (NIR) imaging provides a new tool for studying disease mechanisms and non-invasive monitoring of disease development, even in deep organs. The LI-COR IRDye® 800CW RGD optical probe (RGD probe) is a NIR fluorophore, that can target integrin alpha v beta 3 (α(v)β(3)) in tissues.

OBJECTIVE

This study aims to monitor renal disease progression in an anti-glomerular basement membrane (GBM) nephritis mouse model.

METHODS

Anti-GBM nephritis was induced in 129x1/svJ mice by anti-GBM serum challenge. The expression of integrin α(v)β(3) in the diseased kidney was examined by immunohistochemistry and quantitative polymerase chain reaction. The RGD probe and control fluorophores, the 800CW dye, and the BSA-conjugated 800CW dye, were administered into anti-GBM nephritic mice. LI-COR Pearl® Impulse imaging system was used for in vivo imaging; while ex vivo organ imaging was acquired using the Maestro(TM) imaging system.

RESULTS

Kidney tissue from anti-GBM nephritic mice showed higher levels of integrin α(v)β(3) expression at both the protein and the mRNA level compared to normal mice. The RGD probe allowed in vivo renal imaging and the fluorescent signal could be specifically captured in the diseased kidneys up to 14 days, reflecting longitudinal changes in renal function.

CONCLUSION

The infrared RGD molecular probe that tracks integrin expression can be successfully used to monitor renal disease progression following immune-mediated nephritis.

Divalent cations influence colon cancer cell adhesion in a murine transplantable tumor model

BACKGROUND

Cancer cells adhere principally by integrins, matrix receptors that may be influenced by divalent cations. Surgical wound fluid is high in Mg2+ and low in Ca2+. We hypothesized that Mg+ and Mn2+ promote perioperative adhesion of shed cancer cells to surgical sites and that washing surgical wounds with Ca2+ inhibits implantation.

METHODS

We tested our hypothesis in a murine colon 26 adenocarcinoma model. We added 10 mmol/L CaCl2, 0.25 mmol/L MgCl2, or 0.5 mmol/L MnCl2 to suspended murine colon 26 cancer cells and placed these suspensions into wounds in anesthetized mice. After 30 minutes, we washed away nonadherent cells. In some studies, we 51Cr-labeled the cells and assayed tumor adhesion by wound radioactivity. In parallel studies, we closed the wounds and observed the mice for 90 days.

RESULTS

Mg2+ increased adhesion to 188% +/- 15% of control (n = 10, P < .001) and Mn2+ to 130% +/- 6% (n = 7, P < .001). However, Ca2+ inhibited adhesion to 61% +/- 12% (n = 7, P = .006) of control. Seventy-two percent of survival controls developed tumors during follow-up. Mg2+ and Mn2+ stimulated tumor formation to 96% and 92%, respectively, but adding Ca2+ to the wounds reduced subsequent tumor formation to 56% without altering serum Ca2+. The survival curves each differed significantly by log-rank test (P < .01 each). All pair-wise multiple comparisons were significant (Holm-Sidak, P < .05 each).

CONCLUSION

Thus, the high Mg2+ in endogenous wound fluid may potentiate tumor cell adhesion. However, 10 micromol/L Ca2+ inhibits cancer cell adhesion to murine wounds and subsequent tumor development. Irrigating with dilute CaCl2 could decrease local tumor recurrence by inhibiting the adhesion of shed tumor cells.