Uremic mouse model to study vascular calcification and "inflamm-aging"

LPS-induced senescence of macrophages aggravates calcification and senescence of vascular smooth muscle cells via IFITM3

BACKGROUND

Cellular senescence, macrophages infiltration, and vascular smooth muscle cells (VSMCs) osteogenic transdifferentiation participate in the pathophysiology of vascular calcification in chronic kidney disease (CKD). Senescent macrophages are involved in the regulation of inflammation in pathological diseases. In addition, senescent cells spread senescence to neighboring cells via Interferon-induced transmembrane protein3 (IFITM3). However, the role of senescent macrophages and IFITM3 in VSMCs calcification remains unexplored.

AIMS

To explore the hypothesis that senescent macrophages contribute to the calcification and senescence of VSMCs via IFITM3.

METHODS

Here, the macrophage senescence model was established using Lipopolysaccharides (LPS). The VSMCs were subjected to supernatants from macrophages (MCFS) or LPS-induced macrophages (LPS-MCFS) in the presence or absence of calcifying media (CM). Senescence-associated β-galactosidase (SA-β-gal), Alizarin red (AR), immunofluorescent staining, and western blot were used to identify cell senescence and calcification.

RESULTS

The expression of IFITM3 was significantly increased in LPS-induced macrophages and the supernatants. The VSMCs transdifferentiated into osteogenic phenotype, expressing higher osteogenic differentiation markers (RUNX2) and lower VSMCs constructive makers (SM22α) when cultured with senescent macrophages supernatants. Also, senescence markers (p16 and p21) in VSMCs were significantly increased by senescent macrophages supernatants treated. However, IFITM3 knockdown inhibited this process.

CONCLUSIONS

Our study showed that LPS-induced senescence of macrophages accelerated the calcification of VSMCs via IFITM3. These data provide a new perspective linking VC and aging, which may provide clues for diagnosing and treating accelerated vascular aging in patients with CKD.

Pathogenesis and Mechanism of Uremic Vascular Calcification

This review elucidates the modeling and mechanistic studies of vascular calcification in chronic kidney disease - mineral and bone disorder. In patients with chronic kidney disease, metabolic abnormalities in uremic toxins, including phosphate and indole sulfate, are closely associated with vascular calcification. Vitamin K, vascular circadian clock, and autophagy are also key factors involved in vascular calcification. Furthermore, communication between endothelial cells and smooth muscle cells also plays a pivotal role in the regulation of this process. Together, these factors accelerate vascular calcification progression and increase the risk of cardiovascular events. Therefore, timely intervention for vascular calcification is essential for patients with chronic kidney disease.

The functional role of cellular senescence during vascular calcification in chronic kidney disease

Vascular calcification (VC) has emerged as a key predictor of cardiovascular events in patients with chronic kidney disease (CKD). In recent years, an expanding body of research has put forth the concept of accelerated vascular aging among CKD patients, highlighting the significance of vascular cells senescence in the process of VC. Within the milieu of uremia, senescent vascular endothelial cells (VECs) release extracellular microvesicles (MV) that promote vascular smooth muscle cells (VSMCs) senescence, thereby triggering the subsequent osteogenic phenotypic switch and ultimately contributing to the VC process. In addition, senescent vascular progenitor or stem cells with diminished ability to differentiate into VECs and VSMCS, compromise the repair of vascular integrity, on the other hand, release a cascade of molecules associated with senescence, collectively known as the senescence-associated secretory phenotype (SASP), perpetuating the senescence phenomenon. Furthermore, SASP triggers the recruitment of monocytes and macrophages, as well as adjacent VECs and VSMCs into a pro-adhesive and pro-inflammatory senescent state. This pro-inflammatory microenvironment niche not only impacts the functionality of immune cells but also influences the differentiation of myeloid immune cells, thereby amplifying the reduced ability to effectively clear senescent cells of senescent macrophages, promoted calcification of VSMCs. The objective of this paper is to provide a comprehensive review of the contribution of vascular cell senescence to the emergence and advancement of VC. Gaining a comprehensive understanding of the involvement of cellular senescence within the vessel wall is pivotal, especially when it comes to its intersection with VC. This knowledge is essential for advancing groundbreaking anti-aging therapies, aiming to effectively mitigate cardiovascular diseases.

Protein-Bound Uremic Toxins in Senescence and Kidney Fibrosis

Chronic kidney disease (CKD) is a progressive condition of kidney dysfunction due to diverse causes of injury. In healthy kidneys, protein-bound uremic toxins (PBUTs) are cleared from the systemic circulation by proximal tubule cells through the concerted action of plasma membrane transporters that facilitate their urinary excretion, but the endogenous metabolites are hardly removed with kidney dysfunction and may contribute to CKD progression. Accumulating evidence suggests that senescence of kidney tubule cells influences kidney fibrosis, the common endpoint for CKD with an excessive accumulation of extracellular matrix (ECM). Senescence is a special state of cells characterized by permanent cell cycle arrest and limitation of proliferation, which promotes fibrosis by releasing senescence-associated secretory phenotype (SASP) factors. The accumulation of PBUTs in CKD causes oxidative stress and increases the production of inflammatory (SASP) factors that could trigger fibrosis. Recent studies gave some clues that PBUTs may also promote senescence in kidney tubular cells. This review provides an overview on how senescence contributes to CKD, the involvement of PBUTs in this process, and how kidney senescence can be studied. Finally, some suggestions for future therapeutic options for CKD while targeting senescence are given.

Role of nutritional vitamin D in chronic kidney disease-mineral and bone disorder: A narrative review

Chronic kidney disease-mineral and bone disorder has complex and diverse clinical manifestations, including the simplest abnormalities of calcium, phosphorus and parathyroid hormone detected in blood, abnormalities of bone transformation and mineralization in bone, and calcification of blood vessels or other soft tissues detected on imaging. Patients with CKD-MBD combined low bone mineral density and fragility fractures are referred to as CKD-MBD with low bone mineral density. Vascular calcification refers to ectopic deposition of calcium phosphate in the blood vessel walls and heart valves. The degree of vascular calcification was inversely proportional to bone mineral density. The more severe the degree of vascular calcification, the lower the bone mineral density, and the higher the risk of death, indicating that the bone-vascular axis exists. Activation and alteration of the Wnt signaling pathway are central to the treatment of vascular diseases in uremia. Vitamin D supplementation can prevent secondary hyperparathyroidism, activate osteoblasts, relieve muscle weakness and myalgia, and reduce vascular calcification. Nutritional vitamin D may improve vascular calcification in uremia patients by regulating Wnt signaling pathway.