Reorganization of structural proteins in vascular smooth muscle cells grown in collagen gel and basement membrane matrices (Matrigel): a comparison with their in situ counterparts

Myosin-induced F-actin fragmentation facilitates contraction of actin networks

Mechanical forces play a crucial role in diverse physiological processes, such as cell migration, cytokinesis, and morphogenesis. The actin cytoskeleton generates a large fraction of the mechanical forces via molecular interactions between actin filaments (F-actins) and myosin motors. Recent studies have shown that the common tendency of actomyosin networks to contract into a smaller structure deeply involves F-actin buckling induced by motor activities, fragmentation of F-actins, and the force-dependent unbinding of cross-linkers that inter-connect F-actins. The fragmentation of F-actins was shown to originate from either buckling or tensile force from previous single-molecule experiments. While the role of buckling in network contraction has been studied extensively, to date, the role of tension-induced F-actin fragmentation in network contraction has not been investigated. In this study, we employed in vitro experiments and an agent-based computational model to illuminate when and how the tension-induced F-actin fragmentation facilitates network contraction. Our experiments demonstrated that F-actins can be fragmented due to tensile forces, immediately followed by catastrophic rupture and contraction of networks. Using the agent-based model, we showed that F-actin fragmentation by tension results in distinct rupture dynamics different from that observed in networks only with cross-linker unbinding. Moreover, we found that tension-induced F-actin fragmentation is particularly important for the contraction of networks with high connectivity. Results from our study shed light on an important regulator of the contraction of actomyosin networks which has been neglected. In addition, our results provide insights into the rupture mechanisms of polymeric network structures and bio-inspired materials.

Multiple Cell Cultures for MRI Analysis

Magnetic resonance imaging (MRI) is an imaging method that enables diagnostics. In recent years, this technique has been widely used for research using cell cultures used in pharmaceutical science to understand the distribution of various drugs in a variety of biological samples, from cellular models to tissues. MRI's dynamic development in recent years, in addition to diagnostics, has allowed the method to be implemented to assess response to applied therapies. Conventional MRI imaging provides anatomical and pathological information. Due to advanced technology, MRI provides physiological information. The use of cell cultures is very important in the process of testing new synthesized drugs, cancer research, and stem cell research, among others. Two-dimensional (2D) cell cultures conducted under laboratory conditions, although they provide a lot of information, do not reflect the basic characteristics of the tumor. To replicate the tumor microenvironment in science, a three-dimensional (3D) culture of tumor cells was developed. This makes it possible to reproduce in vivo conditions where, in addition, there is a complex and dynamic process of cell-to-cell communication and cell-matrix interaction. In this work, we reviewed current research in 2D and 3D cultures and their use in MRI studies. Articles for each section were collected from PubMed, ScienceDirect, Web of Science, and Google Scholar.

Design considerations for engineering 3D models to study vascular pathologies in vitro

Many cardiovascular diseases (CVD) are driven by pathological remodelling of blood vessels, which can lead to aneurysms, myocardial infarction, ischaemia and strokes. Aberrant remodelling is driven by changes in vascular cell behaviours combined with degradation, modification, or abnormal deposition of extracellular matrix (ECM) proteins. The underlying mechanisms that drive the pathological remodelling of blood vessels are multifaceted and disease specific; however, unravelling them may be key to developing therapies. Reductionist models of blood vessels created in vitro that combine cells with biomaterial scaffolds may serve as useful analogues to study vascular disease progression in a controlled environment. This review presents the main considerations for developing such in vitro models. We discuss how the design of blood vessel models impacts experimental readouts, with a particular focus on the maintenance of normal cellular phenotypes, strategies that mimic normal cell-ECM interactions, and approaches that foster intercellular communication between vascular cell types. We also highlight how choice of biomaterials, cellular arrangements and the inclusion of mechanical stimulation using fluidic devices together impact the ability of blood vessel models to mimic in vivo conditions. In the future, by combining advances in materials science, cell biology, fluidics and modelling, it may be possible to create blood vessel models that are patient-specific and can be used to develop and test therapies. STATEMENT OF SIGNIFICANCE: Simplified models of blood vessels created in vitro are powerful tools for studying cardiovascular diseases and understanding the mechanisms driving their progression. Here, we highlight the key structural and cellular components of effective models and discuss how including mechanical stimuli allows researchers to mimic native vessel behaviour in health and disease. We discuss the primary methods used to form blood vessel models and their limitations and conclude with an outlook on how blood vessel models that incorporate patient-specific cells and flows can be used in the future for personalised disease modelling.

Aortic "Disease-in-a-Dish": Mechanistic Insights and Drug Development Using iPSC-Based Disease Modeling

Thoracic aortic diseases, whether sporadic or due to a genetic disorder such as Marfan syndrome, lack effective medical therapies, with limited translation of treatments that are highly successful in mouse models into the clinic. Patient-derived induced pluripotent stem cells (iPSCs) offer the opportunity to establish new human models of aortic diseases. Here we review the power and potential of these systems to identify cellular and molecular mechanisms underlying disease and discuss recent advances, such as gene editing, and smooth muscle cell embryonic lineage. In particular, we discuss the practical aspects of vascular smooth muscle cell derivation and characterization, and provide our personal insights into the challenges and limitations of this approach. Future applications, such as genotype-phenotype association, drug screening, and precision medicine are discussed. We propose that iPSC-derived aortic disease models could guide future clinical trials via “clinical-trials-in-a-dish”, thus paving the way for new and improved therapies for patients.

A novel human cell culture model to study visceral smooth muscle phenotypic modulation in health and disease

Adaptation of the smooth muscle cell (SMC) phenotype is essential for homeostasis and is often involved in pathologies of visceral organs (e.g., uterus, bladder, gastrointestinal tract). In vitro studies of the behavior of visceral SMCs under (patho)-physiological conditions are hampered by a spontaneous, uncontrolled phenotypic modulation of visceral SMCs under regular tissue culture conditions. We aimed to develop a new visceral SMC culture model that allows controlled phenotypic modulation. Human uterine SMCs [ULTR and telomerase-immortalized human myometrial cells (hTERT-HM)] were grown to confluency and kept for up to 6 days on regular tissue culture surfaces or basement membrane (BM) matrix-coated surfaces in the presence of 0-10% serum. mRNA and protein expression and localization of SMC-specific phenotype markers and their transcriptional regulators were investigated by quantitative PCR, Western blotting, and immunofluorescence. Maintaining visceral SMCs confluent for 6 days increased α-smooth muscle actin (1.9-fold) and smooth muscle protein 22-α (3.1-fold), whereas smooth muscle myosin heavy chain was only slightly upregulated (1.3-fold). Culturing on a BM matrix-coated surface further increased these proteins and also markedly promoted mRNA expression of γ-smooth muscle actin (15.0-fold), smoothelin (3.5-fold), h-caldesmon (5.2-fold), serum response factor (7.6-fold), and myocardin (8.1-fold). Whereas additional serum deprivation only minimally affected contractile markers, platelet-derived growth factor-BB and transforming growth factor β1 consistently reduced versus increased their expression. In conclusion, we present a simple and reproducible visceral SMC culture system that allows controlled phenotypic modulation toward both the synthetic and the contractile phenotype. This may greatly facilitate the identification of factors that drive visceral SMC phenotypic changes in health and disease.

Versatile synthetic alternatives to Matrigel for vascular toxicity screening and stem cell expansion

The physiological relevance of Matrigel as a cell-culture substrate and in angiogenesis assays is often called into question. Here, we describe an array-based method for the identification of synthetic hydrogels that promote the formation of robust in vitro vascular networks for the detection of putative vascular disruptors, and that support human embryonic stem cell expansion and pluripotency. We identified hydrogel substrates that promoted endothelial-network formation by primary human umbilical vein endothelial cells and by endothelial cells derived from human induced pluripotent stem cells, and used the hydrogels with endothelial networks to identify angiogenesis inhibitors. The synthetic hydrogels show superior sensitivity and reproducibility over Matrigel when evaluating known inhibitors, as well as in a blinded screen of a subset of 38 chemicals, selected according to predicted vascular disruption potential, from the Toxicity ForeCaster library of the US Environmental Protection Agency. The identified synthetic hydrogels should be suitable alternatives to Matrigel for common cell-culture applications.

Modeling and rescue of the vascular phenotype of Williams-Beuren syndrome in patient induced pluripotent stem cells

Elastin haploinsufficiency in Williams-Beuren syndrome (WBS) leads to increased vascular smooth muscle cell (SMC) proliferation and stenoses. Our objective was to generate a human induced pluripotent stem (hiPS) cell model for in vitro assessment of the WBS phenotype and to test the ability of candidate agents to rescue the phenotype. hiPS cells were reprogrammed from skin fibroblasts of a WBS patient with aortic and pulmonary stenosis and healthy control BJ fibroblasts using four-factor retrovirus reprogramming and were differentiated into SMCs. Differentiated SMCs were treated with synthetic elastin-binding protein ligand 2 (EBPL2) (20 μg/ml) or the antiproliferative drug rapamycin (100 nM) for 5 days. We generated four WBS induced pluripotent stem (iPS) cell lines that expressed pluripotency genes and differentiated into all three germ layers. Directed differentiation of BJ iPS cells yielded an 85%-92% pure SMC population that expressed differentiated SMC markers, were functionally contractile, and formed tube-like structures on three-dimensional gel assay. Unlike BJ iPS cells, WBS iPS cells generated immature SMCs that were highly proliferative, showed lower expression of differentiated SMC markers, reduced response to the vasoactive agonists, carbachol and endothelin-1, impaired vascular tube formation, and reduced calcium flux. EBPL2 partially rescued and rapamycin fully rescued the abnormal SMC phenotype by decreasing the smooth muscle proliferation rate and enhancing differentiation and tube formation. WBS iPS cell-derived SMCs demonstrate an immature proliferative phenotype with reduced functional and contractile properties, thereby recapitulating the human disease phenotype. The ability of rapamycin to rescue the phenotype provides an attractive therapeutic candidate for patients with WBS and vascular stenoses.

Characterization of clonal vascular smooth muscle cell lines derived from young and old Fischer 344 rats

A significant finding with aging humans (and aging animal models) is that blood vessels lose their ability to respond to beta-adrenergic receptor stimuli. Therefore, they produce less cyclic adenosine monophosphate (cAMP) and have decreased vasorelaxation with advancing age. This change likely contributes to hypertension, insufficient blood flow, and atherosclerosis. Our goal was to develop a vascular smooth muscle cell culture model that replicates the molecular and biochemical changes observed in blood vessels with advancing age. A clonal selection strategy was used to produce cell lines from 2-, 6-, 12-, and 24-month-old male Fischer 344 rat aortae. Cultures were validated as smooth muscle cells with immunocytochemistry positive for α-actin and negative for von Willebrand factor VIII. Positive staining for G protein-coupled receptor kinase 2 indicated presence of this adrenergic receptor regulator. A total of n = 5 clones from n = 7 animals for each age group were initially analyzed for cAMP accumulation under three conditions: basal, isoproterenol stimulated, and forskolin stimulated. Results found that at passage 3, there was a significant reduction in cAMP accumulation to isoproterenol. However, this reduction disappeared by passage 6. Secondary analysis segregated clones into phenotypic age groups independent of donor animal age. Segregation identified n = 3 clones per group. At passage 3, the age-related change in the beta-adrenergic change was magnified. However, even with segregation, the adrenergic response was lost by passage 6. Our results show that early passaged clonal vascular smooth muscle cell cultures maintain their aging, adrenergic phenotype. Two separate strategies to identify age-representative phenotypes into later passage were unsuccessful.

Mechanical Loading Modulates the Differentiation State of Vascular Smooth Muscle Cells

The cause underlying the onset of stenosis after vascular reconstruction is not well understood. In the present study, we evaluated the effect of mechanical unloading on the differentiation state of human vascular smooth muscle cells (hVSMCs) using a tissue-engineered vascular media (TEVM). hVSMCs cultured in a mechanically loaded three-dimensional environment, known as a living tissue sheet, had a higher differentiated state than cells grown on plastic. When the living tissue sheet was detached from its support, the release of the residual stress resulted in a mechanical unloading and cells within the extracellular matrix (ECM) dedifferentiated as shown by downregulation of differentiation markers. The relaxed living tissue sheet can be rolled onto a tubular mandrel to form a TEVM. The rolling procedure resulted in the reintroduction of a mechanical load leading to a cohesive compacted tissue. During this period, cells gradually redifferentiated and aligned circumferentially to the tubular support. Our results suggest that differentiation of hVSMCs can be driven by mechanical loading and may occur simultaneously in the absence of other cell types. The extrapolation of our results to the clinical context suggests the hypothesis that hVSMCs may adopt a proliferative phenotype resulting from the mechanical unloading of explanted blood vessels during vascular reconstruction. Therefore, we propose that this mechanical unloading may play an important role in the onset of vascular graft stenosis.

Activities of MC3T3-E1 cells cultured on gamma-irradiated salmon atelocollagen scaffold

We investigated the effect of gamma-irradiation on the activities of MC3T3-E1 cells cultured on gamma-irradiated salmon atelocollagen (SAC) scaffolds. SAC-cultured samples were irradiated at doses of 10, 15, and 25 kGy. Gamma-irradiation had a significant impact on the activities of MC3T3-E1 cells. The proliferation rates and alkaline phosphatase activities of MC3T3-E1 cells increased with gamma-irradiation dose.

Podosome-mediated matrix resorption and cell motility in vascular smooth muscle cells

The migration of vascular smooth muscle cells (VSMCs) is a principal factor for the development and progression of vascular diseases. In addition, phenotypic alteration from the contractile (differentiated) to the synthetic (dedifferentiated) state and a proteolytic process in the form of extra cellular matrix degradation are necessary for SMC invasion. The actual mechanism leading to the focal degradation of basement membrane matrix components and, hence, SMC migration within the tissue itself is, however, unclear. In response to phorbol ester [phorbol-12,13-dibutyrate (PDBu)], VSMCs in culture form podosomes, dynamic organelles critical for cell adhesion and substrate degradation that are typically found in invasive cells and cells that cross tissue boundaries. Here, we show that PDBu-stimulated VSMCs resorb the extracellular matrix at the sites of podosomes. Podosome formation correlates with an increased polarization of VSMCs on fibronectin- or collagen-coated flexible substrates in addition to a concomitant induction of cell motility. VSMCs embedded in reconstituted basement membrane support adopt the typical spindle-shaped morphology of differentiated SMCs in vivo and, after PDBu treatment, form peripheral lamellipodia and podosomes around their matrix-contacting surface. Our findings demonstrate that podosome formation is the potential mechanism underlying the ability of VSMCs to traverse the surrounding basement membrane and escape the barrier of the tunica media in vascular diseases.