Modification of Fibronectin by Non-Enzymatic Glycation Impairs K+ Channel Function in Rat Cerebral Artery Smooth Muscle Cells

ECM Modifications Driven by Age and Metabolic Stress Directly Promote Vascular Smooth Muscle Cell Osteogenic Processes

BACKGROUND

The ECM (extracellular matrix) provides the microenvironmental niche sensed by resident vascular smooth muscle cells (VSMCs). Aging and disease are associated with dramatic changes in ECM composition and properties; however, their impact on VSMC phenotype remains poorly studied.

METHODS

Here, we describe a novel in vitro model system that utilizes endogenous ECM to study how modifications associated with age and metabolic disease impact VSMC phenotype. ECM was synthesized using primary human VSMCs and modified during culture or after decellularization. Integrity, stiffness, and composition of the ECM was measured using superresolution microscopy, atomic force microscopy, and proteomics, respectively. VSMCs reseeded onto the modified ECM were analyzed for viability and osteogenic differentiation.

RESULTS

ECMs produced in response to mineral stress showed extracellular vesicle-mediated hydroxyapatite deposition and sequential changes in collagen composition and ECM properties. VSMCs seeded onto the calcified ECM exhibited increased extracellular vesicle release and Runx2 (Runt-related transcription factor 2)-mediated osteogenic gene expression due to the uptake of hydroxyapatite, which led to increased reactive oxygen species and the induction of DNA damage signaling. VSMCs seeded onto the nonmineralized, senescent ECM also exhibited increased Runx2-mediated osteogenic gene expression and accelerated calcification. In contrast, glycated ECM specifically induced increased ALP (alkaline phosphatase) activity, and this was dependent on RAGE (receptor for advanced glycation end products) signaling with both ALP and RAGE receptor inhibition attenuating calcification.

CONCLUSIONS

ECM modifications associated with aging and metabolic disease can directly induce osteogenic differentiation of VSMCs via distinct mechanisms and without the need for additional stimuli. This highlights the importance of the ECM microenvironment as a key driver of phenotypic modulation acting to accelerate age-associated vascular pathologies and provides a novel model system to study the mechanisms of calcification.

Impact of Matrix Gel Variations on Primary Culture of Microvascular Endothelial Cell Function

OBJECTIVE

The endothelium regulates crucial aspects of vascular function, including hemostasis, vasomotor tone, proliferation, immune cell adhesion, and microvascular permeability. Endothelial cells (ECs), especially in arterioles, are pivotal for flow distribution and peripheral resistance regulation. Investigating vascular endothelium physiology, particularly in microvascular ECs, demands precise isolation and culturing techniques.

METHODS

Freshly isolated ECs are vital for examining protein expression, ion channel behavior, and calcium dynamics. Establishing primary endothelial cell cultures is crucial for unraveling vascular functions and understanding intact microvessel endothelium roles. Despite the significance, detailed protocols and comparisons with intact vessels are scarce in microvascular research. We developed a reproducible method to isolate microvascular ECs, assessing substrate influence by cultivating cells on fibronectin and gelatin matrix gels. This comparative approach enhances our understanding of microvascular endothelial cell biology.

RESULTS

Microvascular mesenteric ECs expressed key markers (VE-cadherin and eNOS) in both matrix gels, confirming cell culture purity. Under uncoated conditions, ECs were undetected, whereas proteins linked to smooth muscle cells and fibroblasts were evident. Examining endothelial cell (EC) physiological dynamics on distinct matrix substrates revealed comparable cell length, shape, and Ca2+ elevations in both male and female ECs on gelatin and fibronectin matrix gels. Gelatin-cultured ECs exhibited analogous membrane potential responses to acetylcholine (ACh) or adenosine triphosphate (ATP), contrasting with their fibronectin-cultured counterparts. In the absence of stimulation, fibronectin-cultured ECs displayed a more depolarized resting membrane potential than gelatin-cultured ECs.

CONCLUSIONS

Gelatin-cultured ECs demonstrated electrical behaviors akin to intact endothelium from mouse mesenteric arteries, thus advancing our understanding of endothelial cell behavior within diverse microenvironments.

Delivery technologies for therapeutic targeting of fibronectin in autoimmunity and fibrosis applications

Fibronectin (FN) is a critical component of the extracellular matrix (ECM) contributing to various physiological processes, including tissue repair and immune response regulation. FN regulates various cellular functions such as adhesion, proliferation, migration, differentiation, and cytokine release. Alterations in FN expression, deposition, and molecular structure can profoundly impact its interaction with other ECM proteins, growth factors, cells, and associated signaling pathways, thus influencing the progress of diseases such as fibrosis and autoimmune disorders. Therefore, developing therapeutics that directly target FN or its interaction with cells and other ECM components can be an intriguing approach to address autoimmune and fibrosis pathogenesis.

Advanced glycated end-products inhibit dilation through constitutive endothelial RAGE and Nox1/4 in rat isolated skeletal muscle arteries

OBJECTIVE

This study investigated the actions of advanced glycated end-products (AGE), their receptors (RAGE), and NAD(P)H oxidase (Nox) subtypes 1, 2, and 4 on mechanisms of endothelium-dependent dilation of the rat cremaster muscle artery (CMA).

METHODS

Immunofluorescence studies were used to examine expression of RAGE in rat arteries. ROS accumulation was measured using luminescence and fluorescence assays. Functional studies were performed using pressure myography.

RESULTS

High levels of RAGE expression were shown in the endothelial cells of the CMA, compared with low endothelial expression in middle cerebral and mesenteric arteries and the aorta. Exogenous AGE (in vitro glycated bovine serum albumin) stimulated H2O2 accumulation in CMA, which was prevented by the RAGE antagonist FPS-ZM1, the NAD(P)H oxidase (Nox) inhibitor apocynin and inhibited by the Nox1/4 inhibitor setanaxib, but not the Nox2 inhibitor GSK2795039. In functional studies, AGE inhibited vasodilation of CMA stimulated by acetylcholine, sodium nitroprusside, and the BKCa activator NS1619, but not adenosine-induced dilation. FPS-ZM1, apocynin, and setanaxib prevented the inhibitory effects of AGE on responses to acetylcholine and NS-1619.

CONCLUSION

These observations suggest RAGE are constitutively expressed in the endothelium of the rat CMA and may be activated by AGE to stimulate Nox1/4 and ROS formation with resulting inhibition of NO and BKCa-mediated endothelium-dependent dilation.

Glycation of fibronectin impairs angiopoietin-1/Tie-2 signaling through uncoupling Tie-2-α5β1 integrin crosstalk

The dysfunction of angiopoietin-1 (Ang-1)/Tie-2 signaling pathways has been implicated in diabetic complications. However, the underlying molecular mechanisms remain unclear. Fibronectin (FN) is thought to have an important role in regulating Ang-1/Tie-2 signaling activation. But no previous study has investigated the effects of FN glycation on Ang-1/Tie-2 signaling. In the present study, FN was glycated by methylglyoxal (MGO) to investigate whether the glycation of FN contributes to diabetes-induced Ang-1/Tie-2 signaling impairment and to understand the molecular mechanisms involved. The results demonstrated that MGO-glycated FN significantly impaired Ang-1-evoked phosphorylation of Tie-2 and Akt, Ang-1-induced endothelial cell migration and tube formation and Ang-1-mediated cell survival. The glycation of FN also inhibited the binding of α5β1 integrin to Tie-2. Moreover, FN was remarkably modified by AGEs in aortae derived from db/db mice, indicating the glycation of FN in vivo. Ang-1-induced aortic ring vessel outgrowth and Ang-1-mediated cell survival were also both significantly inhibited in aortae from db/db mice compared to that from the wild type littermates. Moreover, FN, rather than glycated FN partly restored aortic ring angiogenesis in db/db mice, indicating that the angiogenesis defect in the db/db mice are due to FN glycation. Collectively, the results in the present study suggest that the glycation of FN impairs Ang-1/Tie-2 signaling pathway by uncoupling Tie-2-α5β1 integrin crosstalk. This may provide a mechanism for Ang-1/Tie-2 signaling dysfunction and angiogenesis failure in diabetic ischaemic diseases.