Development of the BioHybrid Assay: Combining Primary Human Vascular Smooth Muscle Cells and Blood to Measure Vascular Calcification Propensity

Dephosphorylated uncarboxylated Matrix-Gla-Protein as candidate biomarker for immune-mediated vascular remodeling and prognosis in pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a disease characterized by pulmonary vascular remodeling. Since dephosphorylated-uncarboxylated Matrix Gla-Protein (dp-ucMGP) is associated with cardiovascular mortality in systemic sclerosis, a disease associated with PAH, and immune-system involvement in PAH is increasingly recognized, we investigated the relationship between dp-ucMGP, vascular remodeling and soluble immune-checkpoint proteins in PAH. This prospective cohort study included patients with idiopathic (I)PAH, connective tissue disease (CTD)-PAH, chronic thrombo-embolic PH (CTEPH) and CTD patients without PAH. Patients with IPAH and CTD-PAH were stratified by clinical signs of immune-mediated inflammatory disease (IMID). We measured dp-ucMGP plasma levels, soluble immune-checkpoint proteins (sICPs), and vascular smooth muscle cell (iVSMC) calcification. We found elevated dp-ucMGP levels in all PAH subtypes and CTD patients compared to healthy controls. PAH patients showed increased iVSMC calcification, but no direct correlation was found with dp-ucMGP. IMID-PAH patients had higher dp-ucMGP levels than non-IMID PAH patients. dp-ucMGP correlated with several sICPs in both IPAH and CTD patients; multiple sICPs were elevated in IMID PAH patients. High dp-ucMGP levels in IPAH patients were associated with worse survival. Our findings suggest dp-ucMGP as a potential biomarker of immune-mediated vascular remodeling in PAH. Hence, dp-ucMGP, could help identify PAH patients who might benefit from immunosuppressive therapies.

Why Current Detection of Vascular Calcification Falls Short and How to Improve on It

Vascular calcification is a common phenomenon in various vascular diseases, where its presence heralds increased occurrence of adverse disease events, which invariably lead to increased morbidity and mortality in patients. Although the impact of calcification has become apparent, adequate and early detection of the most damaging form of early microcalcification is still in its infancy, preventing reliable identification of locations that would benefit from intervention. In this review, we will provide an overview of the current state-of-the-art noninvasive calcification imaging and its persisting limitations. We discuss promising approaches that may address these limitations in the future. In this context particular attention will be paid to imaging modalities such as CT, PET, and ultrasonography and molecular and cellular mechanisms and agents involved in physiological bone formation.

Vitamin K for Vascular Calcification in Kidney Patients: Still Alive and Kicking, but Still a Lot to Learn

Patients with chronic kidney disease (CKD) suffer disproportionately from a high burden of cardiovascular disease, which, despite recent scientific advances, remains partly understood. Vascular calcification (VC) is the result of an ongoing process of misplaced calcium in the inner and medial layers of the arteries, which has emerged as a critical contributor to cardiovascular events in CKD. Beyond its established role in blood clotting and bone health, vitamin K appears crucial in regulating VC via vitamin K-dependent proteins (VKDPs). Among these, the matrix Gla protein (MGP) serves as both a potent inhibitor of VC and a valuable biomarker (in its inactive form) for reflecting circulating vitamin K levels. CKD patients, especially in advanced stages, often present with vitamin K deficiency due to dietary restrictions, medications, and impaired intestinal absorption in the uremic environment. Epidemiological studies confirm a strong association between vitamin K levels, inactive MGP, and increased CVD risk across CKD stages. Based on the promising results of pre-clinical data, an increasing number of clinical trials have investigated the potential benefits of vitamin K supplementation to prevent, delay, or even reverse VC, but the results have remained inconsistent.

The Maastricht Acquisition Platform for Studying Mechanisms of Cell-Matrix Crosstalk (MAPEX): An Interdisciplinary and Systems Approach towards Understanding Thoracic Aortic Disease

Current management guidelines for ascending thoracic aortic aneurysms (aTAA) recommend intervention once ascending or sinus diameter reaches 5-5.5 cm or shows a growth rate of >0.5 cm/year estimated from echo/CT/MRI. However, many aTAA dissections (aTAAD) occur in vessels with diameters below the surgical intervention threshold of <55 mm. Moreover, during aTAA repair surgeons observe and experience considerable variations in tissue strength, thickness, and stiffness that appear not fully explained by patient risk factors. To improve the understanding of aTAA pathophysiology, we established a multi-disciplinary research infrastructure: The Maastricht acquisition platform for studying mechanisms of tissue-cell crosstalk (MAPEX). The explicit scientific focus of the platform is on the dynamic interactions between vascular smooth muscle cells and extracellular matrix (i.e., cell-matrix crosstalk), which play an essential role in aortic wall mechanical homeostasis. Accordingly, we consider pathophysiological influences of wall shear stress, wall stress, and smooth muscle cell phenotypic diversity and modulation. Co-registrations of hemodynamics and deep phenotyping at the histological and cell biology level are key innovations of our platform and are critical for understanding aneurysm formation and dissection at a fundamental level. The MAPEX platform enables the interpretation of the data in a well-defined clinical context and therefore has real potential for narrowing existing knowledge gaps. A better understanding of aortic mechanical homeostasis and its derangement may ultimately improve diagnostic and prognostic possibilities to identify and treat symptomatic and asymptomatic patients with existing and developing aneurysms.

The BioHybrid Assay: A Novel Method for Determining Calcification Propensity

Vascular calcification is an active pathological process, characterised by cellular dysregulation and subsequent changes to the extracellular environment. In vivo detection of vascular calcification is only possible late stage via computed tomography, and there is no single biomarker for detecting progression of vascular calcification. There is an unmet clinical need to determine progression of vascular calcification in vulnerable patients. This is especially needed in chronic kidney disease (CKD) patients where there is a correlation of cardiovascular disease with declining renal status. We hypothesised that the entirety of circulating components should be taken into consideration with vessel wall cells to determine real-time vascular calcification development. In this protocol we describe the isolation and characterisation of human primary vascular smooth muscle cells (hpVSMCs), and the addition of human serum or plasma to hpVSMCs in a calcification assay and analysis. The BioHybrid analysis of biological changes to in vitro hpVSMC calcification is reflective of in vivo vascular calcification status. We suggest this analysis can discriminate between CKD patient cohorts and has the potential for wider application for risk factor determination in CKD and the general population.

Application of the mineral-binding protein fetuin-A for the detection of calcified lesions

Rationale: Calcium plays an essential role in the biology of vertebrates. Calcium content in body fluids is maintained within a narrow physiologic range by feedback control. Phosphate is equally important for metabolism and is likewise controlled, albeit over a wider range. This results in a nearly supersaturated state of calcium phosphate in body liquids driving mineral precipitation in soft tissues, which is actively prevented by calcification inhibitors. The hepatic plasma protein fetuin-A is a circulating mineralization inhibitor regulating calcium phosphate crystal growth and calcified matrix metabolism. Ectopic mineralization is associated with many pathological conditions aggravating their outcome. Current diagnostic methods lack sensitivity towards microcalcifications representing the initial stages of the process. Given the irreversibility of established calcifications, novel diagnostic tools capable of detecting nascent calcium phosphate deposits are highly desirable. Methods: We designed fluorescent fusion proteins consisting of fetuin-A coupled to a green or red fluorescent protein derivate, mEmerald or mRuby3, respectively. The proteins were expressed in mammalian cell lines. Sequence optimization resolved folding issues and increased sensitivity of mineral binding. Chimeric proteins were tested for their ability to detect calcifications in cell cultures and tissue sections retrieved from calcification-prone mice. Results: We employed novel genetically labeled fetuin-A-based fluorescent proteins for the detection of ectopic calcifications. We show that fetuin-A-based imaging agents are non-toxic and suitable for live imaging of microcalcifications beyond the detection limit of conventional staining techniques. The ability of fetuin-A to preferentially bind nascent calcium phosphate crystals allowed the resolution of histopathological detail of early kidney damage that went previously undetected. Endogenous expression of fetuin-A fluorescent fusion proteins allowed extended live imaging of calcifying cells with unprecedented sensitivity and specificity. Conclusion: Ectopic microcalcifications represent a major clinical concern lacking effective diagnostic and treatment options. In this paper, we describe novel highly sensitive fetuin-A-based fluorescent probes for imaging microcalcifications. We show that fusion proteins consisting of a fetuin-A mineral binding moiety and a fluorescent protein are superior to the routine methods for detecting calcifications. They also surpass in continuous live cell imaging the chemically fluorescence labeled fetuin-A, which we established previously.

Development of a cyclic-inverso AHSG/Fetuin A-based peptide for inhibition of calcification in osteoarthritis

OBJECTIVE

Ectopic calcification is an important contributor to chronic diseases, such as osteoarthritis. Currently, no effective therapies exist to counteract calcification. We developed peptides derived from the calcium binding domain of human Alpha-2-HS-Glycoprotein (AHSG/Fetuin A) to counteract calcification.

METHODS

A library of seven 30 amino acid (AA) long peptides, spanning the 118 AA Cystatin 1 domain of AHSG, were synthesized and evaluated in an in vitro calcium phosphate precipitation assay. The best performing peptide was modified (cyclic, retro-inverso and combinations thereof) and evaluated in cellular calcification models and the rat Medial Collateral Ligament Transection + Medial Meniscal Tear (MCLT + MMT) osteoarthritis model.

RESULTS

A cyclic peptide spanning AA 1-30 of mature AHSG showed clear inhibition of calcium phosphate precipitation in the nM-pM range that far exceeded the biological activity of the linear peptide variant or bovine Fetuin. Biochemical and electron microscopy analyses of calcium phosphate particles revealed a similar, but distinct, mode of action in comparison with bFetuin. A cyclic-inverso variant of the AHSG 1-30 peptide inhibited calcification of human articular chondrocytes, vascular smooth muscle cells and during osteogenic differentiation of bone marrow derived stromal cells. Lastly, we evaluated the effect of intra-articular injection of the cyclic-inverso AHSG 1-30 peptide in a rat osteoarthritis model. A significant improvement was found in histopathological osteoarthritis score and animal mobility. Serum levels of IFNγ were found to be lower in AHSG 1-30 peptide treated animals.

CONCLUSIONS

The cyclic-inverso AHSG 1-30 peptide directly inhibits the calcification process and holds the potential for future application in osteoarthritis.