Cardiac differentiation of human pluripotent stem cells using defined extracellular matrix proteins reveals essential role of fibronectin

Adult human heart extracellular matrix improves human iPSC-CM function via mitochondrial and metabolic maturation

Myocardial infarction can lead to the loss of billions of cardiomyocytes, and while cell-based therapies are an option, immature nature of in vitro-generated human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (iCMs) is a roadblock to their development. Existing iPSC differentiation protocols don't go beyond producing fetal iCMs. Recently, adult extracellular matrix (ECM) was shown to retain tissue memory and have some success driving tissue-specific differentiation in unspecified cells in various organ systems. Therefore, we focused on investigating the effect of adult human heart-derived extracellular matrix (ECM) on iPSC cardiac differentiation and subsequent maturation. By preconditioning iPSCs with ECM, we tested whether creating cardiac environments around iPSCs would drive iPSCs toward cardiac fate and which ECM components might be involved. We report novel high- and low-abundance proteomes of young, adult, and aged human hearts, with relative abundances to total proteins and each other. We found that adult ECM had extracellular galactin-1, fibronectin, fibrillins, and perlecan (HSPG2) which are implicated in normal heart development. We also showed preconditioning iPSCs with adult cardiac ECM resulted in enhanced cardiac differentiation, yielding iCMs with higher functional maturity, more developed mitochondrial network and coverage, enhanced metabolic maturity, and shift towards more energetic profile. These findings demonstrate the potential use of cardiac ECM in iCM maturation and as a promising strategy for developing iCM-based therapies, disease modeling, and drug screening studies. Upon manipulating ECM, we concluded that the beneficial effects observed were not solely due to the ECM proteins, which might be related to the decorative units attached.

Stereopy: modeling comparative and spatiotemporal cellular heterogeneity via multi-sample spatial transcriptomics

Understanding complex biological systems requires tracing cellular dynamic changes across conditions, time, and space. However, integrating multi-sample data in a unified way to explore cellular heterogeneity remains challenging. Here, we present Stereopy, a flexible framework for modeling and dissecting comparative and spatiotemporal patterns in multi-sample spatial transcriptomics with interactive data visualization. To optimize this framework, we devise a universal container, a scope controller, and an integrative transformer tailored for multi-sample multimodal data storage, management, and processing. Stereopy showcases three representative applications: investigating specific cell communities and genes responsible for pathological changes, detecting spatiotemporal gene patterns by considering spatial and temporal features, and inferring three-dimensional niche-based cell-gene interaction network that bridges intercellular communications and intracellular regulations. Stereopy serves as both a comprehensive bioinformatics toolbox and an extensible framework that empowers researchers with enhanced data interpretation abilities and new perspectives for mining multi-sample spatial transcriptomics data.

Synthetic hydrogels support robust and reproducible cardiomyocyte differentiation

Cardiomyocyte manufacturing from human pluripotent stem cells is limited by the variability of differentiation efficiencies, partly attributed to the widespread use of the tumor-derived substrate Matrigel. Here, we describe a screening approach to identify fully-defined synthetic PEG hydrogels that support iPSC-derived cardiac progenitor cell (iPSC-CPC) adhesion, survival, and differentiation into iPSC-derived cardiomyocytes (iPSC-CMs). Our PEG hydrogels supported superior iPSC-CM differentiation efficiency, with a 24% increase in cTnT expression, and greater reproducibility when compared to cells cultured on Matrigel. By combining our 5-level, 3-variable full factorial screening approach with multi-variate analysis, we showed that all substrate variables manipulated here (adhesion ligand type/concentration, stiffness) had a significant influence on iPSC-CPC confluency and that iPSC-CM differentiation was significantly influenced by adhesion ligands. These results highlight the benefit of synthetic, tunable cell culture substrates and multi-variate screening studies to identify substrate formulations for a targeted cell behavior.

Differential impact of substrates on myosin heavy and light chain expression in human stem cell-derived cardiomyocytes at single-cell level

To fully exploit the potential of human pluripotent stem cell-derived cardiomyocytes, ideally they should acquire a mature, adult ventricular-like phenotype. Predominant expression of the β-isoform of myosin heavy chain (β-MyHC) and the ventricular isoform of myosin regulatory light chain 2 (MLC2v) is a marker of human adult cardiac ventricle. Yet predominant co-expression of these isoforms is rarely reported by current culture protocols. Here, we assessed the impact of different substrates on β-MyHC and MLC2v expression in single human embryonic stem cell-derived CMs (hESC-CMs). As substrates, surface materials with differing stiffness as defined by Young's modulus were combined with either laminin, a single-component coating, or Matrigel, a multi-component coating including growth factors. Semi-quantitative single-cell immunofluorescence analysis demonstrated that surfaces with supraphysiological stiffness in combination with laminin are sufficient for promotion of predominant β-MyHC expression, but not for predominant MLC2v expression in hESC-CMs. Accordingly, mechanical stimuli likely promote expression of β-MyHC in these cultures. Culture on matrices with a lower stiffness than glass in combination with growth factor-containing Matrigel led to only moderate increases in MLC2v expression, possibly more dependent on growth factors, suggesting different regulation of expression. Integrin-related downstream signal transducers, integrin-linked and cardiac troponin I-interacting kinase, as well as modulation of intracellular Ca2+-concentration and epigenetic signaling did not affect MyHC/MLC2 isoform expression. The data indicate that expression of adult ventricular markers β-MyHC and MLC2v depends on different stimuli like substrate stiffness and growth factors. To conclude, multiple stimuli appear to be necessary to promote an adult ventricular phenotype.

The role of the extracellular matrix in cardiac regeneration

The extracellular matrix (ECM) is a complex and dynamic three-dimensional network that functions as an architectural scaffold to maintain cardiac homeostasis. Important biochemical and mechanical signals associated with cell‒cell communication are provided via the reciprocal interaction between cells and the ECM. By converting mechanical cues into biochemical signals, the ECM regulates many cell processes, including migration, adhesion, growth, differentiation, proliferation, and apoptosis. Moreover, the ECM facilitates the replacement of dead cells and preserves the structural integrity of the heart, making it essential in conditions such as myocardial infarction and other pathological states. When excessive ECM deposition or abnormal production of ECM components occurs, the heart undergoes fibrosis, leading to cardiac dysfunction and heart failure. However, emerging evidence suggests that the ECM may contribute to heart regeneration following cardiac injury. The present review offers a complete overview of the existing information and novel discoveries regarding the involvement of the ECM in heart regeneration from both mechanical and biochemical perspectives. Understanding the ECM and its involvement in mechanotransduction holds significant potential for advancing therapeutic approaches in heart repair and regeneration.

Induced pluripotent stem cell-derived cardiomyocyte in vitro models: benchmarking progress and ongoing challenges

Recent innovations in differentiating cardiomyocytes from human induced pluripotent stem cells (hiPSCs) have unlocked a viable path to creating in vitro cardiac models. Currently, hiPSC-derived cardiomyocytes (hiPSC-CMs) remain immature, leading many in the field to explore approaches to enhance cell and tissue maturation. Here, we systematically analyzed 300 studies using hiPSC-CM models to determine common fabrication, maturation and assessment techniques used to evaluate cardiomyocyte functionality and maturity and compiled the data into an open-access database. Based on this analysis, we present the diversity of, and current trends in, in vitro models and highlight the most common and promising practices for functional assessments. We further analyzed outputs spanning structural maturity, contractile function, electrophysiology and gene expression and note field-wide improvements over time. Finally, we discuss opportunities to collectively pursue the shared goal of hiPSC-CM model development, maturation and assessment that we believe are critical for engineering mature cardiac tissue.

Tissue-engineered fibrillar fibronectin matrices are not only lovely, but also functional for regenerative medicines and in vitro model systems

Fibronectin is an ubiquitous extracellular matrix protein which comprises fibrous three-dimensional microenvironments in native tissues. Although its importance and fibrillogenesis in vivo has been considerably investigated, yet current in vitro tissue engineering platforms for fibrillar fibronectin pose major drawbacks such as low scalability, applicability, and reproducibility. Due to such platform limitations, understanding of spatiotemporal mechanobiology between cells and fibrillar fibronectin matrices largely remains unexplored. This article briefly underlines current tissue-engineering platforms and mechanobiological understanding of fibrillar fibronectin as well as suggests potential directions in future fibronectin researches.

Fibrotic extracellular matrix impacts cardiomyocyte phenotype and function in an iPSC-derived isogenic model of cardiac fibrosis

Cardiac fibrosis occurs following insults to the myocardium and is characterized by the abnormal accumulation of non-compliant extracellular matrix (ECM), which compromises cardiomyocyte contractile activity and eventually leads to heart failure. This phenomenon is driven by the activation of cardiac fibroblasts (cFbs) to myofibroblasts and results in changes in ECM biochemical, structural and mechanical properties. The lack of predictive in vitro models of heart fibrosis has so far hampered the search for innovative treatments, as most of the cellular-based in vitro reductionist models do not take into account the leading role of ECM cues in driving the progression of the pathology. Here, we devised a single-step decellularization protocol to obtain and thoroughly characterize the biochemical and micro-mechanical properties of the ECM secreted by activated cFbs differentiated from human induced pluripotent stem cells (iPSCs). We activated iPSC-derived cFbs to the myofibroblast phenotype by tuning basic fibroblast growth factor (bFGF) and transforming growth factor beta 1 (TGF-β1) signalling and confirmed that activated cells acquired key features of myofibroblast phenotype, like SMAD2/3 nuclear shuttling, the formation of aligned alpha-smooth muscle actin (α-SMA)-rich stress fibres and increased focal adhesions (FAs) assembly. Next, we used Mass Spectrometry, nanoindentation, scanning electron and confocal microscopy to unveil the characteristic composition and the visco-elastic properties of the abundant, collagen-rich ECM deposited by cardiac myofibroblasts in vitro. Finally, we demonstrated that the fibrotic ECM activates mechanosensitive pathways in iPSC-derived cardiomyocytes, impacting on their shape, sarcomere assembly, phenotype, and calcium handling properties. We thus propose human bio-inspired decellularized matrices as animal-free, isogenic cardiomyocyte culture substrates recapitulating key pathophysiological changes occurring at the cellular level during cardiac fibrosis.

Improving iPSC Differentiation Using a Nanodot Platform

Differentiation of induced pluripotent stem cells (iPSCs) is an extremely complex process that has proven difficult to study. In this research, we utilized nanotopography to elucidate details regarding iPSC differentiation by developing a nanodot platform consisting of nanodot arrays of increasing diameter. Subjecting iPSCs cultured on the nanodot platform to a cardiomyocyte (CM) differentiation protocol revealed several significant gene expression profiles that were associated with poor differentiation. The observed expression trends were used to select existing small-molecule drugs capable of modulating differentiation efficiency. BRD K98 was repurposed to inhibit CM differentiation, while iPSCs treated with NSC-663284, carmofur, and KPT-330 all exhibited significant increases in not only CM marker expression but also spontaneous beating, suggesting improved CM differentiation. In addition, quantitative polymerase chain reaction was performed to determine the gene regulation responsible for modulating differentiation efficiency. Multiple genes involved in extracellular matrix remodeling were correlated with a CM differentiation efficiency, while genes involved in the cell cycle exhibited contrasting expression trends that warrant further studies. The results suggest that expression profiles determined via short time-series expression miner analysis of nanodot-cultured iPSC differentiation can not only reveal drugs capable of enhancing differentiation efficiency but also highlight crucial sets of genes related to processes such as extracellular matrix remodeling and the cell cycle that can be targeted for further investigation. Our findings confirm that the nanodot platform can be used to reveal complex mechanisms behind iPSC differentiation and could be an indispensable tool for optimizing iPSC technology for clinical applications.

Influence of Remodeled ECM and Co-culture with iPSC-Derived Cardiac Fibroblasts on the Mechanical Function of Micropatterned iPSC-Derived Cardiomyocytes

INTRODUCTION

In native heart tissue, functions of cardiac fibroblasts (CFs) include synthesis, remodeling, and degradation of the extracellular matrix (ECM) as well as secreting factors that regulate cardiomyocyte (CM) function. The influence of direct co-culture and CF-derived ECM on CM mechanical function are not fully understood.

METHODS

Here we use an engineered culture platform that provides control over ECM geometry and substrate stiffness to evaluate the influence of iPSC-CFs, and the ECM they produce, on the mechanical function of iPSC-CMs. Mechanical analysis was performed using digital image correlation to quantify maximum contractile strain, spontaneous contraction rate, and full-field organization of the contractions.

RESULTS

When cultured alone, iPSC-CFs produce and remodel the ECM into fibers following the underlying 15° chevron patterned ECM. The substrates were decellularized and confirmed to have highly aligned fibers that covered a large fraction of the pattern area before reseeding with iPSC-CMs, alone or in co-culture with iPSC-CFs. When seeded on decellularized ECM, larger maximum contractile strains were observed in the co-culture condition compared to the CM Only condition. No significant difference was found in contractile strain between the Matrigel and decellularized ECM conditions; however, the spontaneous contraction rate was lower in the decellularized ECM condition. A methodology for quantifying alignment of cell contraction across the entire field of view was developed based on trajectories approximating the cell displacements during contraction. Trajectory alignment was unaltered by changes in culture or ECM conditions.

CONCLUSIONS

These combined observations highlight the important role CFs play in vivo and the need for models that enable a quantitative approach to examine interactions between the CFs and CMs, as well as the interactions of these cells with the ECM.

Fibronectin promotes tumor angiogenesis and progression of non-small-cell lung cancer by elevating WISP3 expression via FAK/MAPK/ HIF-1α axis and activating wnt signaling pathway

BACKGROUND

Fibronectin, an extracellular matrix protein, has been reported to be associated with heterogeneous cancer stemness, angiogenesis and progression in multiple cancer types. However, the roles and the underlying mechanism of fibronectin on the progression NSCLC need to be further elucidated.

METHODS

Public dataset such as Kaplan-Meier Plotter was used to determine the prognostic significance of genes. The correlation of different protein expression in clinical and xenograft tissues was tested by immunohistochemistry experiment. Both in vitro and in vivo experiments were performed to determine the role of fibronectin on the tumor growth, metastasis, and angiogenesis in NSCLC. The activation of key signaling pathway under fibronectin was examined by WB assay. RNA-seq was applicated to screening the target gene of fibronectin. Rescue experiment was performed to confirm the role of target gene in fibronectin-mediated function in NSCLC. Finally, luciferase and CHIP assays were used to elucidate the mechanism by which fibronectin regulated the target gene.

RESULTS

Our results revealed that fibronectin was up-regulated in cancer tissues compared with the normal ones in NSCLC patients. Dish- coated fibronectin enhanced the tumor growth, metastasis, and angiogenesis of NSCLC in vitro and in vivo by promoting EMT and maintaining stemness of NSCLC cells. As expected, fibronectin activated FAK and its downstream MAPK/ERK signaling pathway. WISP3 was screened as a potential target gene of fibronectin. Interestingly, WISP3 effectively activated Wnt signaling pathway, and knockdown of WISP3 effectively blocked the influence of fibronectin on the migration, invasion and vascular structure formation potential of NSCLC cells. Our data also manifested that fibronectin elevated the transcription of WISP3 gene by promoting the binding of HIF-1α to the promoter region of WISP3 in NSCLC cells.

CONCLUSIONS

Our findings sketched the outline of the route for fibronectin exert its role in NSCLC, in which fibronectin activated downstream FAK and MAPK/ERK signaling pathways, and mediated the accumulation of HIF-1α. Then, HIF-1α enabled the transcription of WISP3, and subsequently promoted the activation of Wnt signaling pathway, and finally enhanced the tumor growth, metastasis, and angiogenesis in NSCLC.

Differentiating Human Pluripotent Stem Cells to Cardiomyocytes Using Purified Extracellular Matrix Proteins

Human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) can be differentiated into cardiomyocytes (hESC-CMs and iPSC-CMs, respectively), which hold great promise for cardiac regenerative medicine and disease modeling efforts. However, the most widely employed differentiation protocols require undefined substrates that are derived from xenogeneic (animal) products, contaminating resultant hESC- and iPSC-CM cultures with xenogeneic proteins and limiting their clinical applicability. Additionally, typical hESC- and iPSC-CM protocols produce CMs that are significantly contaminated by non-CMs and that are immature, requiring lengthy maturation procedures. In this review, we will summarize recent studies that have investigated the ability of purified extracellular matrix (ECM) proteins to support hESC- and iPSC-CM differentiation, with a focus on commercially available ECM proteins and coatings to make such protocols widely available to researchers. The most promising of the substrates reviewed here include laminin-521 with laminin-221 together or Synthemax (a synthetic vitronectin-based peptide coating), which both resulted in highly pure CM cultures. Future efforts are needed to determine whether combinations of specific purified ECM proteins or derived peptides could further improve CM maturation and culture times, and significantly improve hESC- and iPSC-CM differentiation protocols.