Vascular Calcification: In Vitro Models under the Magnifying Glass

TGF-β Enhances Phosphate-Driven Calcification of Human OA Articular Chondrocytes

The pathological relevance of articular cartilage calcification in osteoarthritis (OA) is becoming increasingly evident. We are only beginning to understand the pathobiological mechanisms that contribute to articular cartilage calcification in OA. How molecular environmental factors interact with calcification mechanisms is poorly explored. In this study, we developed an in vitro phosphate-driven calcification model for human OA articular chondrocytes, in which these cells are cultured in the presence of calcification medium containing adenosine triphosphate (ATP) and β-glycerophosphate (BGP). We employed this model to investigate the role of transforming growth factor β (TGF-β) in chondrocyte calcification. Chondrocyte culture in calcification medium resulted in mineral nodule formation over a time course of 7 days. The presence of calcium and phosphate deposition in these nodules was validated with von Kossa staining, scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX), and colorimetric calcium and phosphate assays. Supplementation of calcification medium with TGF-β resulted in enhanced nodule formation with a different morphology and changed the expression of extracellular matrix-related genes such as collagen type I and III. In conclusion, we developed a new in vitro model for human OA articular chondrocyte calcification, in which we demonstrated a pro-calcifying role for TGF-β. This in vitro model may be used as a basis to aid the investigation of the influence of environmental factors on chondrocyte calcification and the development of new anti-calcification disease-modifying osteoarthritis drugs.

Role of abdominal aortic calcification score in predicting cardiovascular risk in the general population

BACKGROUND

Abdominal aortic calcification (AAC) is closely related to cardiovascular disease. Although its clinical significances have primarily been investigated in patients with chronic kidney disease, its association with cardio-cerebrovascular mortality in the general middle-aged and elderly population has not been sufficiently investigated.

AIMS

To study the association of AAC and cardio-cerebrovascular mortality in both the entire general middle-aged and elderly populations and age subgroups.

METHODS

Data of participants of the National Health and Nutrition Examination Survey (NHANES) 2013-2014 were analyzed. This study included middle-aged and elderly (≥ 40 years old) individuals who underwent dual-energy X-ray absorptiometry. The severity of AAC was assessed by an AAC scoring system (AAC score) with a maximum possible value of 24. Participants were tracked for survival status and major cause of death till 31st December 2019. This study utilized AAC score = 6 as the optimal cut-off according to Harrell's c statistic. Based on AAC scores, participants were trichotomized (0, 0-6, and ≥ 6). Groupwise survival curves and cumulative incidence functions were plotted to reveal the association of AAC and cardio-cerebrovascular mortality. Given results under trichotomization, combination of participants with AAC scores 0 and 0-6 was conducted to reaffirm the association of AAC and adverse prognosis.

RESULTS

Correlation between increased AAC score and poorer survival, higher cumulative incidence of events was revealed. Cox models identified AAC score ≥ 6 as an independent risk factor of cardio-cerebrovascular mortality (AAC score ≥ 6 vs. AAC score = 0: Hazard ratio: 2.38, P = 0.008) after adjusting for cardiovascular risk factors. Results remained significant after regrouping (AAC score ≥ 6 vs. AAC score < 6: Hazard ratio: 2.06, P = 0.016). Subgroup analysis provided no evidence of unparallel change in hazard for the same amount of increase in AAC score among middle-aged (40-65 years old) and elderly (≥ 65 years old) individuals.

CONCLUSIONS

AAC score ≥ 6 independently indicate increased risk of cardio-cerebrovascular death and would be effective in risk stratification among the general middle-aged and elderly population in clinical practice.

Unravelling molecular mechanisms in atherosclerosis using cellular models and omics technologies

Despite the discovery and prevalent clinical use of potent lipid-lowering therapies, including statins and PCSK9 inhibitors, cardiovascular diseases (CVD) caused by atherosclerosis remain a large unmet clinical need, accounting for frequent deaths worldwide. The pathogenesis of atherosclerosis is a complex process underlying the presence of modifiable and non-modifiable risk factors affecting several cell types including endothelial cells (ECs), monocytes/macrophages, smooth muscle cells (SMCs) and T cells. Heterogeneous composition of the plaque and its morphology could lead to rupture or erosion causing thrombosis, even a sudden death. To decipher this complexity, various cell model systems have been developed. With recent advances in systems biology approaches and single or multi-omics methods researchers can elucidate specific cell types, molecules and signalling pathways contributing to certain stages of disease progression. Compared with animals, in vitro models are economical, easily adjusted for high-throughput work, offering mechanistic insights. Hereby, we review the latest work performed employing the cellular models of atherosclerosis to generate a variety of omics data. We summarize their outputs and the impact they had in the field. Challenges in the translatability of the omics data obtained from the cell models will be discussed along with future perspectives.

Breaking new ground: Unraveling the USP1/ID3/E12/P21 axis in vascular calcification

Vascular calcification (VC) poses significant challenges in cardiovascular health. This study employs single-cell transcriptome sequencing to dissect cellular dynamics in this process. We identify distinct cell subgroups, notably in vascular smooth muscle cells (VSMCs), and observe differences between calcified atherosclerotic cores and adjacent regions. Further exploration reveals ID3 as a key gene regulating VSMC function. In vitro experiments demonstrate ID3's interaction with USP1 and E12, modulating cell proliferation and osteogenic differentiation. Animal models confirm the critical role of the USP1/ID3/E12/P21 axis in VC. This study sheds light on a novel regulatory mechanism, offering potential therapeutic targets.

In Vitro Models of Cardiovascular Calcification

Cardiovascular calcification, characterized by hydroxyapatite deposition in the arterial wall and heart valves, is associated with high cardiovascular morbidity and mortality. Cardiovascular calcification is a hallmark of aging but is frequently seen in association with chronic diseases, such as chronic kidney disease (CKD), diabetes, dyslipidemia, and hypertension in the younger population as well. Currently, there is no therapeutic approach to prevent or cure cardiovascular calcification. The pathophysiology of cardiovascular calcification is highly complex and involves osteogenic differentiation of various cell types of the cardiovascular system, such as vascular smooth muscle cells and valve interstitial cells. In vitro cellular and ex vivo tissue culture models are simple and useful tools in cardiovascular calcification research. These models contributed largely to the discoveries of the numerous calcification inducers, inhibitors, and molecular mechanisms. In this review, we provide an overview of the in vitro cell culture and the ex vivo tissue culture models applied in the research of cardiovascular calcification.

A Dynamic Cellular Model as an Emerging Platform to Reproduce the Complexity of Human Vascular Calcification In Vitro

Vascular calcification (VC) is a cardiovascular disease characterized by calcium salt deposition in vascular smooth muscle cells (VSMCs). Standard in vitro models used in VC investigations are based on VSMC monocultures under static conditions. Although these platforms are easy to use, the absence of interactions between different cell types and dynamic conditions makes these models insufficient to study key aspects of vascular pathophysiology. The present study aimed to develop a dynamic endothelial cell-VSMC co-culture that better mimics the in vivo vascular microenvironment. A double-flow bioreactor supported cellular interactions and reproduced the blood flow dynamic. VSMC calcification was stimulated with a DMEM high glucose calcification medium supplemented with 1.9 mM NaH2PO4/Na2HPO4 (1:1) for 7 days. Calcification, cell viability, inflammatory mediators, and molecular markers (SIRT-1, TGFβ1) related to VSMC differentiation were evaluated. Our dynamic model was able to reproduce VSMC calcification and inflammation and evidenced differences in the modulation of effectors involved in the VSMC calcified phenotype compared with standard monocultures, highlighting the importance of the microenvironment in controlling cell behavior. Hence, our platform represents an advanced system to investigate the pathophysiologic mechanisms underlying VC, providing information not available with the standard cell monoculture.

Interorgan communication in neurogenic heterotopic ossification: the role of brain-derived extracellular vesicles

Brain-derived extracellular vesicles participate in interorgan communication after traumatic brain injury by transporting pathogens to initiate secondary injury. Inflammasome-related proteins encapsulated in brain-derived extracellular vesicles can cross the blood‒brain barrier to reach distal tissues. These proteins initiate inflammatory dysfunction, such as neurogenic heterotopic ossification. This recurrent condition is highly debilitating to patients because of its relatively unknown pathogenesis and the lack of effective prophylactic intervention strategies. Accordingly, a rat model of neurogenic heterotopic ossification induced by combined traumatic brain injury and achillotenotomy was developed to address these two issues. Histological examination of the injured tendon revealed the coexistence of ectopic calcification and fibroblast pyroptosis. The relationships among brain-derived extracellular vesicles, fibroblast pyroptosis and ectopic calcification were further investigated in vitro and in vivo. Intravenous injection of the pyroptosis inhibitor Ac-YVAD-cmk reversed the development of neurogenic heterotopic ossification in vivo. The present work highlights the role of brain-derived extracellular vesicles in the pathogenesis of neurogenic heterotopic ossification and offers a potential strategy for preventing neurogenic heterotopic ossification after traumatic brain injury. Brain-derived extracellular vesicles (BEVs) are released after traumatic brain injury. These BEVs contain pathogens and participate in interorgan communication to initiate secondary injury in distal tissues. After achillotenotomy, the phagocytosis of BEVs by fibroblasts induces pyroptosis, which is a highly inflammatory form of lytic programmed cell death, in the injured tendon. Fibroblast pyroptosis leads to an increase in calcium and phosphorus concentrations and creates a microenvironment that promotes osteogenesis. Intravenous injection of the pyroptosis inhibitor Ac-YVAD-cmk suppressed fibroblast pyroptosis and effectively prevented the onset of heterotopic ossification after neuronal injury. The use of a pyroptosis inhibitor represents a potential strategy for the treatment of neurogenic heterotopic ossification.