Compliant substratum guides endothelial commitment from human pluripotent stem cells

Effects of PDMS culture on stem cell differentiation towards definitive endoderm and hepatocytes

The generation of human induced pluripotent stem cell (hiPSC) derivatives for regenerative medicine applications holds tremendous promise in treating various disorders. One critical target includes liver disease, in which the primary curative treatment is a cellular transplant aimed to restore the lost function of hepatocytes. In an effort to improve the differentiation of hiPSC-derived liver tissue, we manipulated the mechanical conditions of endoderm specification through directed perturbation of the cytoskeleton and through 2D substrate culture on viscoelastic materials. Through a combination of qRT-PCR, immunofluorescence staining, and functional assays, we found that mechanical cues can bias endoderm specification in an actomyosin and Yes-associated protein (YAP) dependent manner, unveiling new insights into mechanotransduction in germ layer specification and downstream maturation toward parenchymal cells. STATEMENT OF SIGNIFICANCE: The translational potential of using human induced pluripotent stem cell (hiPSC) derived hepatocytes to therapeutically improve impaired liver function holds great clinical promise. However, challenges remain in efficiently differentiating functional hepatocytes with mature marker expression. In an effort to improve the differentiation efficiency of hepatocytes, the role of early mechanosensing mechanisms was investigated in the specification of hiPSCs to definitive endoderm progenitor populations. Through a combination of cytoskeletal modulation, control of mechanoresponsive, yes-associated protein expression, and culture on physiologically compliant PDMS substrates, we found that soft environments not only improve progenitor specification but also impact the downstream functionality of differentiated hepatocytes. These results contribute to the collective appreciation that mechanical cues are critical in developmental processes.

Toward robust and reproducible pluripotent stem cell expansion in bioprinted GelMA constructs

Combining the technologies of 3D bioprinting and human induced pluripotent stem cells (hiPSCs) has allowed for the creation of tissues with organ-level function in the lab, a promising technique for disease modeling and regenerative medicine. Expanding the stem cells in bioprinted tissues prior to differentiation allows for high cell density, which is important for the formation of cell-cell junctions necessary for macroscale function upon differentiation. Yet, stem cell expansion, critical to successful in situ differentiation, depends heavily on the composition of the bioprinted scaffold. Here, we demonstrate how a common bioink component, gelatin methacryloyl (GelMA), varies depending on the vendor and degree of functionalization. We found that the vendor/GelMA production technique played a greater role in dictating the mechanical properties of the bioprinted constructs than the degree of functionalization, emphasizing the importance of reporting detailed characterization of GelMA scaffolds. Furthermore, the ability of singularized hiPSCs to survive and expand in GelMA scaffolds greatly varied across batches from different vendors and degrees of functionalization, where expansion correlated with the mechanical properties of the scaffold. Yet, we found that using a commercial cloning supplement could restore the ability of single hiPSCs to survive and expand across GelMA types, thus compensating for the varied mechanical properties of the scaffolds. These findings provide a practical guide for the expansion of hiPSCs in GelMA constructs with various mechanical properties as required for successful in situ differentiation.

Gelatin-Mediated Vascular Self-Assembly via a YAP-MMP Signaling Axis

Tissue self-assembly relies on the interplay between structural cues imparted by the extracellular matrix and instructive chemical factors that guide cellular signaling pathways. Here, we report that endothelial cell-laden gelatin-based hydrogels with optimized mechanical and chemical properties facilitate de novo vasculogenesis and recruitment of endogenous blood vessels in vivo. We demonstrate that these engineered matrices, with tailored viscoelastic features and stiffness, drive vascular self-assembly in a yes-associated protein mechanosensing-dependent manner through αvβ3 integrin and matrix metalloproteinase 2 activity. Our research highlights how the extracellular matrix, in the form of gelatin-based hydrogels with adjustable stress relaxation rates, drive vascular morphogenesis in the absence of growth factor supplementation, lending to a minimalistic platform for discretizing features of the microenvironment niche. Collectively, these results demonstrate a testbed that enables mechanistic evaluation of morphogenetic processes. Specifically, our results show how mechanical cues impact signaling pathways that modulate vascular remodeling, a critical tissue engineering paradigm needed for the translational application of vascularized grafts for regenerative medicine applications.

Assessment of human embryonic stem cells differentiation into definitive endoderm lineage on the soft substrates

Pluripotent stem cells (PSCs) hold enormous potential for treating multiple diseases owing to their ability to self-renew and differentiate into any cell type. Albeit possessing such promising potential, controlling their differentiation into a desired cell type continues to be a challenge. Recent studies suggest that PSCs respond to different substrate stiffness and, therefore, can differentiate towards some lineages via Hippo pathway. Human PSCs can also differentiate and self-organize into functional cells, such as organoids. Traditionally, human PSCs are differentiated on stiff plastic or glass plates towards definitive endoderm and then into functional pancreatic progenitor cells in the presence of soluble growth factors. Thus, whether stiffness plays any role in differentiation towards definitive endoderm from human pluripotent stem cells (hPSCs) remains unclear. Our study found that the directed differentiation of human embryonic stem cells towards endodermal lineage on the varying stiffness did not differ from the differentiation on stiff plastic dishes. We also observed no statistical difference between the expression of yes-associated protein (YAP) and phosphorylated YAP. Furthermore, we demonstrate that lysophosphatidic acid, a YAP activator, enhanced definitive endoderm formation, whereas verteporfin, a YAP inhibitor, did not have the significant effect on the differentiation. In summary, our results suggest that human embryonic stem cells may not differentiate in response to changes in stiffness, and that such cues may not have as significant impact on the level of YAP. Our findings indicate that more research is needed to understand the direct relationship between biophysical forces and hPSCs differentiation.

Vascularized liver-on-a-chip model to investigate nicotine-induced dysfunction

The development of physiologically relevant in vitro systems for simulating disease onset and progression and predicting drug metabolism holds tremendous value in reducing drug discovery time and cost. However, many of these platforms lack accuracy in replicating the tissue architecture and multicellular interactions. By leveraging three-dimensional cell culture, biomimetic soft hydrogels, and engineered stimuli, in vitro models have continued to progress. Nonetheless, the incorporation of the microvasculature has been met with many challenges, specifically with the addition of parenchymal cell types. Here, a systematic approach to investigating the initial seeding density of endothelial cells and its effects on interconnected networks was taken and combined with hepatic spheroids to form a liver-on-a-chip model. Leveraging this system, nicotine's effects on microvasculature and hepatic function were investigated. The findings indicated that nicotine led to interrupted adherens junctions, decreased guanosine triphosphate cyclohydrolase 1 expression, impaired angiogenesis, and lowered barrier function, all key factors in endothelial dysfunction. With the combination of the optimized microvascular networks, a vascularized liver-on-a-chip was formed, providing functional xenobiotic metabolism and synthesis of both albumin and urea. This system provides insight into potential hepatotoxicity caused by various drugs and allows for assessing vascular dysfunction in a high throughput manner.

How Hydrogel Stiffness Affects Adipogenic Differentiation of Mesenchymal Stem Cells under Controlled Morphology

Matrix stiffness has been disclosed as an essential regulator of cell fate. However, it is barely studied how the matrix stiffness affects stem cell functions when cell morphology changes. Thus, in this study, the effect of hydrogel stiffness on adipogenic differentiation of human bone-marrow-derived mesenchymal stem cells (hMSCs) with controlled morphology was investigated. Micropatterns of different size and elongation were prepared by a photolithographical micropatterning technique. The hMSCs were cultured on the micropatterns and showed a different spreading area and elongation following the geometry of the underlying micropatterns. The cells with controlled morphology were embedded in agarose hydrogels of different stiffnesses. The cells showed a different level of adipogenic differentiation that was dependent on both hydrogel stiffness and cell morphology. Adipogenic differentiation became strong when the cell spreading area decreased and hydrogel stiffness increased. Adipogenic differentiation did not change with cell elongation. Therefore, cell spreading area and hydrogel stiffness could synergistically affect adipogenic differentiation of hMSCs, while cell elongation did not affect adipogenic differentiation. A change of cell morphology and hydrogel stiffness was accompanied by actin filament alignment that was strongly related to adipogenic differentiation. The results indicated that cell morphology could affect cellular sensitivity to hydrogel stiffness. The results will provide useful information for the elucidation of the interaction of stem cells and their microenvironmental biomechanical cues.

Stiff Substrate Induces Nucleus Pulposus Cell Ferroptosis via YAP and N-Cadherin Mediated Mechanotransduction

Increased tissue stiffness is associated with various pathological processes, such as fibrosis, inflammation, and aging. The matrix stiffness of the nucleus pulposus (NP) tissues increases gradually during intervertebral disc degeneration (IDD), while the mechanism through which NP cells sense and react to matrix stiffness remains unclear. In this study, the results indicate that ferroptosis is involved in stiff substrate-induced NP cell death. The expression of acyl-CoA synthetase long-chain family member 4 (ACSL4) increases in NP cells of the stiff group, which mediates lipid peroxidation and ferroptosis in NP cells. In addition, stiff substrate activates the hippo signaling cascade and induces the nuclear translocation of yes-associated protein (YAP). Interestingly, inhibition of YAP is efficient to reverse the increase of ACSL4 expression caused by matrix stiffness. Furthermore, stiff substrate suppresses the expression of N-cadherin in NP cells. N-cadherin overexpression can inhibit YAP nuclear translocation via the formation of the N-cadherin/β-catenin/YAP complex, and reverse matrix stiffness-induced ferroptosis in NP cells. Finally, the effects of YAP inhibition and N-cadherin overexpression on IDD progression are further illustrated in animal models. These findings reveal a new mechanism of mechanotransduction in NP cells, providing novel insights into the development of therapies for the treatment of IDD.

Induced pluripotent stem cells for cardiovascular therapeutics: Progress and perspectives

The discovery of methods for reprogramming adult somatic cells into induced pluripotent stem cells (iPSCs) opens up prospects of developing personalized cell-based therapy options for a variety of human diseases as well as disease modeling and new drug discovery. Like embryonic stem cells, iPSCs can give rise to various cell types of the human body and are amenable to genetic correction. This allows usage of iPSCs in the development of modern therapies for many virtually incurable human diseases. The review summarizes progress in iPSC research in the context of application in the cardiovascular field including modeling cardiovascular disease, drug study, tissue engineering, and perspectives for personalized cardiovascular medicine.

Hydrogels to Recapture Extracellular Matrix Cues That Regulate Vascularization

The ECM (extracellular matrix) is a 3-dimensional network that supports cellular responses and maintains structural tissue integrity in healthy and pathological conditions. The interactions between ECM and cells trigger signaling cascades that lead to phenotypic changes and structural and compositional turnover of the ECM, which in turn regulates vascular cell behavior. Hydrogel biomaterials are a powerful platform for basic and translational studies and clinical applications due to their high swelling capacity and exceptional versatility in compositions and properties. This review highlights recent developments and uses of engineered natural hydrogel platforms that mimic the ECM and present defined biochemical and mechanical cues for vascularization. Specifically, we focus on modulating vascular cell stimulation and cell-ECM/cell-cell interactions in the microvasculature that are the established biomimetic microenvironment.

The extracellular matrix mechanics in the vasculature

Mechanical stimuli from the extracellular matrix (ECM) modulate vascular differentiation, morphogenesis and dysfunction of the vasculature. With innovation in measurements, we can better characterize vascular microenvironment mechanics in health and disease. Recent advances in material sciences and stem cell biology enable us to accurately recapitulate the complex and dynamic ECM mechanical microenvironment for in vitro studies. These biomimetic approaches help us understand the signaling pathways in disease pathologies, identify therapeutic targets, build tissue replacement and activate tissue regeneration. This Review analyzes how ECM mechanics regulate vascular homeostasis and dysfunction. We highlight approaches to examine ECM mechanics at tissue and cellular levels, focusing on how mechanical interactions between cells and the ECM regulate vascular phenotype, especially under certain pathological conditions. Finally, we explore the development of biomaterials to emulate, measure and alter the physical microenvironment of pathological ECM to understand cell-ECM mechanical interactions toward the development of therapeutics.

Extracellular matrix cues regulate the differentiation of pluripotent stem cell-derived endothelial cells

The generation of endothelial cells (ECs) from human pluripotent stem cells (PSCs) has been a promising approach for treating cardiovascular diseases for several years. Human PSCs, particularly induced pluripotent stem cells (iPSCs), are an attractive source of ECs for cell therapy. Although there is a diversity of methods for endothelial cell differentiation using biochemical factors, such as small molecules and cytokines, the efficiency of EC production varies depending on the type and dose of biochemical factors. Moreover, the protocols in which most EC differentiation studies have been performed were in very unphysiological conditions that do not reflect the microenvironment of native tissue. The microenvironment surrounding stem cells exerts variable biochemical and biomechanical stimuli that can affect stem cell differentiation and behavior. The stiffness and components of the extracellular microenvironment are critical inducers of stem cell behavior and fate specification by sensing the extracellular matrix (ECM) cues, adjusting the cytoskeleton tension, and delivering external signals to the nucleus. Differentiation of stem cells into ECs using a cocktail of biochemical factors has been performed for decades. However, the effects of mechanical stimuli on endothelial cell differentiation remain poorly understood. This review provides an overview of the methods used to differentiate ECs from stem cells by chemical and mechanical stimuli. We also propose the possibility of a novel EC differentiation strategy using a synthetic and natural extracellular matrix.

Getting physical: Material mechanics is an intrinsic cell cue

Advances in biomaterial science have allowed for unprecedented insight into the ability of material cues to influence stem cell function. These material approaches better recapitulate the microenvironment, providing a more realistic ex vivo model of the cell niche. However, recent advances in our ability to measure and manipulate niche properties in vivo have led to novel mechanobiological studies in model organisms. Thus, in this review, we will discuss the importance of material cues within the cell niche, highlight the key mechanotransduction pathways involved, and conclude with recent evidence that material cues regulate tissue function in vivo.

Progress and emerging techniques for biomaterial-based derivation of mesenchymal stem cells (MSCs) from pluripotent stem cells (PSCs)

The use of mesenchymal stem cells (MSCs) for clinical purposes has skyrocketed in the past decade. Their multilineage differentiation potentials and immunomodulatory properties have facilitated the discovery of therapies for various illnesses. MSCs can be isolated from infant and adult tissue sources, which means they are easily available. However, this raises concerns because of the heterogeneity among the various MSC sources, which limits their effective use. Variabilities arise from donor- and tissue-specific differences, such as age, sex, and tissue source. Moreover, adult-sourced MSCs have limited proliferation potentials, which hinders their long-term therapeutic efficacy. These limitations of adult MSCs have prompted researchers to develop a new method for generating MSCs. Pluripotent stem cells (PSCs), such as embryonic stem cells and induced PSCs (iPSCs), can differentiate into various types of cells. Herein, a thorough review of the characteristics, functions, and clinical importance of MSCs is presented. The existing sources of MSCs, including adult- and infant-based sources, are compared. The most recent techniques for deriving MSCs from iPSCs, with a focus on biomaterial-assisted methods in both two- and three-dimensional culture systems, are listed and elaborated. Finally, several opportunities to develop improved methods for efficiently producing MSCs with the aim of advancing their various clinical applications are described.

Stiffness-Tunable Hydrogel-Sandwich Culture Modulates the YAP-Mediated Mechanoresponse in Induced-Pluripotent Stem Cell Embryoid Bodies and Augments Cardiomyocyte Differentiation

Microenvironmental factors, including substrate stiffness, regulate stem cell behavior and differentiation. However, the effects of substrate stiffness on the behavior of induced pluripotent stem cell (iPSC)- derived embryoid bodies (EB) remain unclear. To investigate the effects of mechanical cues on iPSC-EB differentiation, a 3D hydrogel-sandwich culture (HGSC) system is developed that controls the microenvironment surrounding iPSC-EBs using a stiffness-tunable polyacrylamide hydrogel assembly. Mouse iPSC-EBs are seeded between upper and lower polyacrylamide hydrogels of differing stiffness (Young's modulus [E'] = 54.3 ± 7.1 kPa [hard], 28.1 ± 2.3 kPa [moderate], and 5.1 ± 0.1 kPa [soft]) and cultured for 2 days. HGSC induces stiffness-dependent activation of the yes-associated protein (YAP) mechanotransducer and actin cytoskeleton rearrangement in the iPSC-EBs. Moreover, moderate-stiffness HGSC specifically upregulates the mRNA and protein expression of ectoderm and mesoderm lineage differentiation markers in iPSC-EBs via YAP-mediated mechanotransduction. Pretreatment of mouse iPSC-EBs with moderate-stiffness HGSC promotes cardiomyocyte (CM) differentiation and structural maturation of myofibrils. The proposed HGSC system provides a viable platform for investigating the role of mechanical cues on the pluripotency and differentiation of iPSCs that can be beneficial for research into tissue regeneration and engineering.

ECM Architecture-Mediated Regulation of β-Cell Differentiation from hESCs via Hippo-Independent YAP Activation

Changes in the extracellular matrix (ECM) influence stem cell fate. When hESCs were differentiated on a thin layer of Matrigel coated onto PDMS (Matrigel__PDMS), they exhibited a substantial increase in focal adhesion and focal adhesion-associated proteins compared with those cultured on Matrigel coated onto TCPS (Matrigel__TCPS), resulting in YAP/TEF1 activation and ultimately promoting the transcriptional activities of pancreatic endoderm (PE)-associated genes. Interestingly, YAP activation in PE cells was mediated through integrin α3-FAK-CDC42-PP1A signaling rather than the typical Hippo signaling pathway. Furthermore, pancreatic islet-like organoids (PIOs) generated on Matrigel__PDMS secreted more insulin than those generated from Matrigel__TCPS. Electron micrographs revealed differential Matrigel architectures depending on the underlying substrate, resulting in varying cell-matrix anchorage resistance levels. Accordingly, the high apparent stiffness of the unique mucus-like network structure of Matrigel__PDMS was the critical factor that directly upregulated focal adhesion, thereby leading to better maturation of the pancreatic development of hESCs in vitro.

Inner ear organoids: progress and outlook, with a focus on the vascularization

The inner ear is a complex organ that encodes sound, motion, and orientation in space. Given the complexity of the inner ear, it is not surprising that treatments are relatively limited despite the fact that, in 2015, hearing loss was the fourth leading cause of years lived with disability worldwide. Inner ear organoid models are a promising tool to advance the study of multiple aspects of the inner ear to aid the development of new treatments and validate drug-based therapies. The blood supply of the inner ear plays a pivotal role in growth, maturation, and survival of inner ear tissues and their physiological functions. This vasculature cannot be ignored in order to achieve a truly in vivo-like model that mimics the microenvironment and niches of organ development. However, this aspect of organoid development has remained largely absent in the generation of inner ear organoids. The current review focuses on three-dimensional inner ear organoid and how recent technical progress in generating in vitro vasculature can enhance the next generation of these models.

Role of YAP as a Mechanosensing Molecule in Stem Cells and Stem Cell-Derived Hematopoietic Cells

Yes-associated protein (YAP) and WW domain-containing transcription regulator protein 1 (WWTR1, also known as TAZ) are transcriptional coactivators in the Hippo signaling pathway. Both are well-known regulators of cell proliferation and organ size control, and they have significant roles in promoting cell proliferation and differentiation. The roles of YAP and TAZ in stem cell pluripotency and differentiation have been extensively studied. However, the upstream mediators of YAP and TAZ are not well understood. Recently, a novel role of YAP in mechanosensing and mechanotransduction has been reported. The present review updates information on the regulation of YAP by mechanical cues such as extracellular matrix stiffness, fluid shear stress, and actin cytoskeleton tension in stem cell behaviors and differentiation. The review explores mesenchymal stem cell fate decisions, pluripotent stem cells (PSCs), self-renewal, pluripotency, and differentiation to blood products. Understanding how cells sense their microenvironment or niche and mimic those microenvironments in vitro could improve the efficiency of producing stem cell products and the efficacy of the products.

An overview of substrate stiffness guided cellular response and its applications in tissue regeneration

Cell-matrix interactions play a critical role in tissue repair and regeneration. With gradual uncovering of substrate mechanical characteristics that can affect cell-matrix interactions, much progress has been made to unravel substrate stiffness-mediated cellular response as well as its underlying mechanisms. Yet, as a part of cell-matrix interaction biology, this field remains in its infancy, and the detailed molecular mechanisms are still elusive regarding scaffold-modulated tissue regeneration. This review provides an overview of recent progress in the area of the substrate stiffness-mediated cellular responses, including 1) the physical determination of substrate stiffness on cell fate and tissue development; 2) the current exploited approaches to manipulate the stiffness of scaffolds; 3) the progress of recent researches to reveal the role of substrate stiffness in cellular responses in some representative tissue-engineered regeneration varying from stiff tissue to soft tissue. This article aims to provide an up-to-date overview of cell mechanobiology research in substrate stiffness mediated cellular response and tissue regeneration with insightful information to facilitate interdisciplinary knowledge transfer and enable the establishment of prognostic markers for the design of suitable biomaterials.

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Substrate stiffness physically determines cell fate and tissue development.

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Rational design of scaffolds requires the understanding of cell-matrix interactions.

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Substrate stiffness depends on scaffold molecular-constituent-structure interaction.

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Substrate stiffness-mediated cellular responses vary in different tissues.

Delivering Mechanical Stimulation to Cells: State of the Art in Materials and Devices Design

Biochemical signals, such as growth factors, cytokines, and transcription factors are known to play a crucial role in regulating a variety of cellular activities as well as maintaining the normal function of different tissues and organs. If the biochemical signals are assumed to be one side of the coin, the other side comprises biophysical cues. There is growing evidence showing that biophysical signals, and in particular mechanical cues, also play an important role in different stages of human life ranging from morphogenesis during embryonic development to maturation and maintenance of tissue and organ function throughout life. In order to investigate how mechanical signals influence cell and tissue function, tremendous efforts have been devoted to fabricating various materials and devices for delivering mechanical stimuli to cells and tissues. Here, an overview of the current state of the art in the design and development of such materials and devices is provided, with a focus on their design principles, and challenges and perspectives for future research directions are highlighted.

Endothelial Cell Differentiation and Hemogenic Specification

Formation of the vasculature is a critical step within the developing embryo and its disruption causes early embryonic lethality. This complex process is driven by a cascade of signaling events that controls differentiation of mesodermal progenitors into primordial endothelial cells and their further specification into distinct subtypes (arterial, venous, hemogenic) that are needed to generate a blood circulatory network. Hemogenic endothelial cells give rise to hematopoietic stem and progenitor cells that generate all blood cells in the body during embryogenesis and postnatally. We focus our discussion on the regulation of endothelial cell differentiation, and subsequent hemogenic specification, and highlight many of the signaling pathways involved in these processes, which are conserved across vertebrates. Gaining a better understanding of the regulation of these processes will yield insights needed to optimize the treatment of vascular and hematopoietic disease and generate human stem cell-derived vascular and hematopoietic cells for tissue engineering and regenerative medicine.

Substrate stiffness regulates differentiation of induced pluripotent stem cells into heart valve endothelial cells

Substrate stiffness has been indicated as a primary determinant for stem cell fate, being capable of influencing motility, proliferation, and differentiation. Although the effects of stiffness on cardiac differentiation of human-induced pluripotent stem cells (h-iPSCs) have been reported, whether stiffness of polydimethylsiloxane-based substrates could enhance differentiation of h-iPSCs toward heart valve endothelial cells lineage (VECs) or not remains unknown. Herein, we modulated the substrate stiffness to evaluate its effect on the differentiation of h-iPSCs into valve endothelial-like cells (h-iVECs) in vitro and determine the suitable stiffness. The results revealed that VECs-related genes (PECAM1, CDH5, NFATC1, etc.) were significantly increased in h-iVECs obtained from the three substrates compared with h-iPSCs. Gene expression levels and differentiation efficiency were higher in the medium group than in the stiff and soft groups. An increase in substrate stiffness to 2.8 GPa decreased the efficiency of h-iPSCs differentiation into h-iVECs and downregulated VECs specific genes. Through mRNA sequencing, we determined the key genetic markers involved in stiffness guiding the differentiation of cardiac progenitor cells into h-iVECs. Unsupervised hierarchical clustering showed that medium stiffness were more suitable for the differentiation of h-iPSCs into h-iVECs in vitro. Moreover, this process is regulated by the WNT/Calcineurin signaling pathway. Overall, this study demonstrates how stiffness can be used to enhance the h-iVECs differentiation of iPSCs and emphasizes the importance of using substrate stiffness to accomplish a more specific and mature differentiation of h-iVECs for future therapeutic and tissue engineering valve applications. STATEMENT OF SIGNIFICANCE: Several studies have examined the stiffness-induced cell fate from pluripotent stem cells during the stage of mesoderm cell differentiation. This is the first research that rigorously examines the effect of substrate stiffness on human valve endothelial-like cells differentiation from cardiac progenitor cells. We found that the medium stiffness can increase the differentiation efficiency of h-iVECs from 40% to about 60%, and this process was regulated by the WNT/CaN signaling pathway through the activation of WNT5a. Substrate stiffness not only increases the differentiation efficiency of h-iVECs, but also improves its cellular functions such as low-density lipoprotein uptake and NO release. This study emphasizes the importance of using substrate stiffness to accomplish a more specific and mature differentiation of h-iVECs.

Home Away From Home: Bioengineering Advancements to Mimic the Developmental and Adult Stem Cell Niche

The inherent self-organizing capacity of pluripotent and adult stem cell populations has advanced our fundamental understanding of processes that drive human development, homeostasis, regeneration, and disease progression. Translating these principles into in vitro model systems has been achieved with the advent of organoid technology, driving innovation to harness patient-specific, cell-laden regenerative constructs that can be engineered to augment or replace diseased tissue. While developmental organization and regenerative adult stem cell niches are tightly regulated in vivo, in vitro analogs lack defined architecture and presentation of physicochemical cues, leading to the unhindered arrangement of mini-tissues that lack complete physiological mimicry. This review aims to highlight the recent integrative engineering approaches that elicit spatio-temporal control of the extracellular niche to direct the structural and functional maturation of pluripotent and adult stem cell derivatives. While the advances presented here leverage multi-pronged strategies ranging from synthetic biology to microfabrication technologies, the methods converge on recreating the biochemical and biophysical milieu of the native tissue to be modeled or regenerated.

A novel engineered vascular construct of stem cell-laden 3D-printed PGSA scaffold enhances tissue revascularization

Development of transplantable engineered tissue has been hampered by lacking vascular network within the engineered tissue. Three-dimensional (3D) printing has emerged as a new technology with great potential in fabrication and customization of geometric microstructure. In this study, utilizing digital light processing system, we manufactured a recently designed novel 3D architecture scaffold with poly(glycerol sebacate) acrylate (PGSA). Vascular construct was subsequently generated by seeding stem cells within this scaffold. PGSA provided inductive substrate in terms of supporting three-germ layer differentiation of embryonic stem cells (ESCs) and also promoting ESCs-derived vascular progenitor cells (VPCs) differentiation into endothelial cells (ECs). Furthermore, the differentiation efficiency of VPCs into ECs on PGSA was much higher than that on collagen IV or fibronectin. The results from seeding VPCs in the rotating hexagonal PGSA scaffold suggest that this architectural framework is highly efficient for cell engraftment in 3D structures. After long-term suspension culture of the VPCs in scaffold under directed EC differentiation condition, VPC-differentiated ECs were populated in the scaffold and expressed EC markers. Transplantation of the vascular construct in mice resulted in formation of new vascular network and integration of the microvasculature within the scaffold into the existing vasculature of host tissue. Importantly, in a mouse model of wound healing, ECs from the transplanted vascular construct directly contributed to revascularization and enhanced blood perfusion at the injured site. Collectively, this transplantable vascular construct provides an innovative alternative therapeutic strategy for vascular tissue engineering.

Early Vascular Cells Improve Microvascularization Within 3D Cardiac Spheroids

Introduction: A key obstacle in the creation of engineered cardiac tissues of clinically relevant sizes is limited diffusion of oxygen and nutrients. Thus, there is a need for organized vascularization within a three-dimensional (3D) tissue environment. Human induced pluripotent stem cell (hiPSC)-derived early vascular cells (EVCs) have shown to improve organization of vascular networks within hydrogels. We hypothesize that introduction of EVCs into 3D microtissue spheroids will lead to increased microvascular formation and improve spheroid formation. Methods: HiPSC-derived cardiomyocytes (CMs) were cocultured with human adult ventricular cardiac fibroblasts (FB) and either human umbilical vein endothelial cells (HUVECs) or hiPSC-derived EVCs for 72 h to form mixed cell spheroids. Three different groups of cell ratios were tested: Group 1 (control) consisted of CM:FB:HUVEC 70:15:15, Group 2 consisted of CM:FB:EVC 70:15:15, and Group 3 consisted of CM:FB:EVC 40:15:45. Vascularization, cell distribution, and cardiac function were investigated. Results: Improved microvasculature was found in EVC spheroids with new morphologies of endothelial organization not found in Group 1 spheroids. CMs were found in a core-shell type distribution in Group 1 spheroids, but more uniformly distributed in EVC spheroids. Contraction rate increased into Group 2 spheroids compared to Group 1 spheroids. Conclusion: The triculture of CM, FB, and EVC within a multicellular cardiac spheroid promotes microvascular formation and cardiac spheroid contraction.

Biomaterials Regulate Mechanosensors YAP/TAZ in Stem Cell Growth and Differentiation

Tissue-resident stem cells are surrounded by a microenvironment known as 'stem cell niche' which is specific for each stem cell type. This niche comprises of cell-intrinsic and -extrinsic factors like biochemical and biophysical signals, which regulate stem cell characteristics and differentiation. Biochemical signals have been thoroughly studied however, the effect of biophysical signals on stem cell regulation is yet to be completely understood. Biomaterials have aided in addressing this issue since they can provide a defined and tuneable microenvironment resembling in vivo conditions. We review various biomaterials used in many studies which have shown a connection between biomaterial-generated mechanical signals and alteration in stem cell behaviour. Researchers probed to understand the mechanism of mechanotransduction and reported that the signals from the extracellular matrix regulate a transcription factor yes-associated protein (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ), which is a downstream-regulator of the Hippo pathway and it transduces the mechanical signals inside the nucleus. We highlight the role of the YAP/TAZ as mechanotransducers in stem cell self-renewal and differentiation in response to substrate stiffness, also the possibility of mechanobiology as the emerging field of regenerative medicines and three-dimensional tissue printing.

Understanding the influence of substrate when growing tumorspheres

Background

Cancer stem cells are important for the development of many solid tumors. These cells receive promoting and inhibitory signals that depend on the nature of their environment (their niche) and determine cell dynamics. Mechanical stresses are crucial to the initiation and interpretation of these signals.

Methods

A two-population mathematical model of tumorsphere growth is used to interpret the results of a series of experiments recently carried out in Tianjin, China, and extract information about the intraspecific and interspecific interactions between cancer stem cell and differentiated cancer cell populations.

Results

The model allows us to reconstruct the time evolution of the cancer stem cell fraction, which was not directly measured. We find that, in the presence of stem cell growth factors, the interspecific cooperation between cancer stem cells and differentiated cancer cells induces a positive feedback loop that determines growth, independently of substrate hardness. In a frustrated attempt to reconstitute the stem cell niche, the number of cancer stem cells increases continuously with a reproduction rate that is enhanced by a hard substrate. For growth on soft agar, intraspecific interactions are always inhibitory, but on hard agar the interactions between stem cells are collaborative while those between differentiated cells are strongly inhibitory. Evidence also suggests that a hard substrate brings about a large fraction of asymmetric stem cell divisions. In the absence of stem cell growth factors, the barrier to differentiation is broken and overall growth is faster, even if the stem cell number is conserved.

Conclusions

Our interpretation of the experimental results validates the centrality of the concept of stem cell niche when tumor growth is fueled by cancer stem cells. Niche memory is found to be responsible for the characteristic population dynamics observed in tumorspheres. The model also shows why substratum stiffness has a deep influence on the behavior of cancer stem cells, stiffer substrates leading to a larger proportion of asymmetric doublings. A specific condition for the growth of the cancer stem cell number is also obtained

Supplementary Information

The online version contains supplementary material available at (10.1186/s12885-021-07918-1).

HIF2A gain-of-function mutation modulates the stiffness of smooth muscle cells and compromises vascular mechanics

Heterozygous gain-of-function (GOF) mutations of hypoxia-inducible factor 2α (HIF2A), a key hypoxia-sensing regulator, are associated with erythrocytosis, thrombosis, and vascular complications that account for morbidity and mortality of patients. We demonstrated that the vascular pathology of HIF2A GOF mutations is independent of erythrocytosis. We generated HIF2A GOF-induced pluripotent stem cells (iPSCs) and differentiated them into endothelial cells (ECs) and smooth muscle cells (SMCs). Unexpectedly, HIF2A-SMCs, but not HIF2A-ECs, were phenotypically aberrant, more contractile, stiffer, and overexpressed endothelin 1 (EDN1), myosin heavy chain, elastin, and fibrillin. EDN1 inhibition and knockdown of EDN1-receptors both reduced HIF2-SMC stiffness. Hif2A GOF heterozygous mice displayed pulmonary hypertension, had SMCs with more disorganized stress fibers and higher stiffness in their pulmonary arterial smooth muscle cells, and had more deformable pulmonary arteries compared with wild-type mice. Our findings suggest that targeting these vascular aberrations could benefit patients with HIF2A GOF and conditions of augmented hypoxia signaling.

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HIF2-SMCs are stiffer than WT-SMCs and differ in contractile SMC marker expression

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HIF2-SMCs and WT-SMCs differ in EDN1 production and ECM composition

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HIF- 2α induces EDN1; EDNI subsequently induces SMC stiffening

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Hif2A GOF mouse arterial SMCs have more disorganized stress fibers and are stiffer

Tethering transforming growth factor β1 to soft hydrogels guides vascular smooth muscle commitment from human mesenchymal stem cells

Mesenchymal stem cells (MSCs) hold great promise for vascular smooth muscle regeneration. However, most studies have mainly relied on extended supplementation of sophisticated biochemical regimen to drive MSC differentiation towards vascular smooth muscle cells (vSMCs). Herein we demonstrate a concomitant method that exploits the advantages of biomimetic matrix stiffness and tethered transforming growth factor β1 (TGF-β1) to guide vSMC commitment from human MSCs. Our designed poly(ethylene glycol) hydrogels, presenting a biomimetic stiffness and tethered TGF-β1, provide an instructive environment to potently upregulate smooth muscle marker expression in vitro and in vivo. Importantly, it significantly enhances the functional contractility of vSMCs derived from MSCs within 3 days. Interestingly, compared to non-tethered one, tethered TGF-β1 enhanced the potency of vSMC commitment on hydrogels. We provide compelling evidence that combining stiffness and tethered TGF-β1 on poly(ethylene glycol) hydrogels can be a promising approach to drastically enhance maturation and function of vSMCs from stem cell differentiation in vitro and in vivo. STATEMENT OF SIGNIFICANCE: A fast, reliable and safe regeneration of vascular smooth muscle cells (vSMCs) from stem cell differentiation is promising for vascular tissue engineering and regenerative medicine applications, but remains challenging. Herein, a photo-click hydrogel platform is devised to recapitulate the stiffness of vascular tissue and appropriate presentation of transforming growth factor β1 (TGF-β1) to guide vSMC commitment from mesenchymal stem cells (MSCs). We demonstrate that such concomitant method drastically enhanced regeneration of mature, functional vSMCs from MSCs in vitro and in vivo within only a 3-days span. This work is not only of fundamental scientific importance, revealing how physiochemical factors and the manner of their presentation direct stem cell differentiation, but also attacks the long-standing difficulty in regenerating highly functional vSMCs within a short period.

Injectable Highly Tunable Oligomeric Collagen Matrices for Dental Tissue Regeneration

Current stem cell transplantation approaches lack efficacy, because they limit cell survival and retention and, more importantly, lack a suitable cellular niche to modulate lineage-specific differentiation. Here, we evaluate the intrinsic ability of type I oligomeric collagen matrices to modulate dental pulp stem cells (DPSCs) endothelial and odontogenic differentiation as a potential stem cell-based therapy for regenerative endodontics. DPSCs were encapsulated in low-stiffness (235 Pa) and high-stiffness (800 Pa) oligomeric collagen matrices and then evaluated for long-term cell survival, as well as endothelial and odontogenic differentiation following in vitro cell culture. Moreover, the effect of growth factor incorporation, i.e., vascular endothelial growth factor (VEGF) into 235 Pa oligomeric collagen or bone morphogenetic protein (BMP2) into the 800 Pa oligomeric collagen counterpart on endothelial or odontogenic differentiation of encapsulated DPSCs was investigated. DPSCs-laden oligomeric collagen matrices allowed long-term cell survival. Real time polymerase chain reaction (RT-PCR) data showed that the DPSCs cultured in 235 Pa matrices demonstrated an increased expression of endothelial markers after 28 days, and the effect was enhanced upon VEGF incorporation. There was a significant increase in alkaline phosphatase (ALP) activity at Day 14 in the 800 Pa DPSCs-laden oligomeric collagen matrices, regardless of BMP2 incorporation. However, Alizarin S data demonstrated higher mineralization by Day 21 and the effect was amplified in BMP2-modified matrices. Herein, we present key data that strongly support future research aimed at clinical translation of an injectable oligomeric collagen system for delivery and fate regulation of DPSCs to enable pulp and dentin regeneration at specific locations of the root canal system.

Differential HDAC6 Activity Modulates Ciliogenesis and Subsequent Mechanosensing of Endothelial Cells Derived from Pluripotent Stem Cells

The role of primary cilia in mechanosensation is essential in endothelial cell (EC) shear responsiveness. Here, we find that venous, capillary, and progenitor ECs respond to shear stress in vitro in a cilia-dependent manner. We then demonstrate that primary cilia assembly in human induced pluripotent stem cell (hiPSC)-derived ECs varies between different cell lines with marginal influence of differentiation protocol. hiPSC-derived ECs lacking cilia do not align to shear stress, lack stress fiber assembly, have uncoordinated migration during wound closure in vitro, and have aberrant calcium influx upon shear exposure. Transcriptional analysis reveals variation in regulatory genes involved in ciliogenesis among different hiPSC-derived ECs. Moreover, inhibition of histone deacetylase 6 (HDAC6) activity in hiPSC-ECs lacking cilia rescues cilia formation and restores mechanical sensing. Taken together, these results show the importance of primary cilia in hiPSC-EC mechano-responsiveness and its modulation through HDAC6 activity varies among hiPSC-ECs.

Application of Human Induced Pluripotent Stem Cells in Generating Tissue-Engineered Blood Vessels as Vascular Grafts

In pace with the advancement of tissue engineering during recent decades, tissue-engineered blood vessels (TEBVs) have been generated using primary seed cells, and their impressive success in clinical trials have demonstrated the great potential of these TEBVs as implantable vascular grafts in human regenerative medicine. However, the production, therapeutic efficacy, and readiness in emergencies of current TEBVs could be hindered by the accessibility, expandability, and donor-donor variation of patient-specific primary seed cells. Alternatively, using human induced pluripotent stem cells (hiPSCs) to derive seed vascular cells for vascular tissue engineering could fundamentally address this current dilemma in TEBV production. As an emerging research field with a promising future, the generation of hiPSC-based TEBVs has been reported recently with significant progress. Simultaneously, to further promote hiPSC-based TEBVs into vascular grafts for clinical use, several challenges related to the safety, readiness, and structural integrity of vascular tissue need to be addressed. Herein, this review will focus on the evolution and role of hiPSCs in vascular tissue engineering technology and summarize the current progress, challenges, and future directions of research on hiPSC-based TEBVs.

Isolation and culture of vascular smooth muscle cells from rat placenta

We developed a new separation method for isolating placental vascular smooth muscle cells (PVSMCs) from a rat in this study. Our method used the magnetic force between a magnet and ferrous ferric oxide (Fe3 O 4 ) to make the separation and extraction processes easier and more efficient. From the first to sixth generation, the cells isolated using this protocol were identified as smooth muscle cells (SMCs) by their immunoreactivity to the SMC markers and by the "hill and valley" morphology. PVSMCs were exposed to angiotensin II (1 μmol/L) and resulted in sharply increased intracellular Ca 2+ concentration. Furthermore, activation of protein kinase C (PKC) increased concomitantly with a decrease in calponin expression. These results indicate that the isolated cells had biological activity. Our method of isolating PVSMCs from rat leads to isolation of cultured cells with activity and high purity. The approach will be useful in research studies on placental vascular diseases.

Generation of Endothelial Cells From Human Pluripotent Stem Cells

Endothelial cells (ECs) are critical for several aspects of cardiovascular disease therapy, including vascular regeneration, personalized drug development, and tissue engineering. Human pluripotent stem cells (hPSCs) afford us with an unprecedented opportunity to produce virtually unlimited quantities of human ECs. In this review, we highlight key developments and outstanding challenges in our ability to derive ECs de novo from hPSCs. Furthermore, we consider strategies for recapitulating the vessel- and tissue-specific functional heterogeneity of ECs in vitro. Finally, we discuss ongoing attempts to utilize hPSC-derived ECs and their progenitors for various therapeutic applications. Continued progress in generating hPSC-derived ECs will profoundly enhance our ability to discover novel drug targets, revascularize ischemic tissues, and engineer clinically relevant tissue constructs. Visual Overview- An online visual overview is available for this article.

Combining Stem Cells and Biomaterial Scaffolds for Constructing Tissues and Cell Delivery

Combining stem cells with biomaterial scaffolds serves as a promising strategy for engineering tissues for both in vitro and in vivo applications. This updated review details commonly used biomaterial scaffolds for engineering tissues from stem cells. We first define the different types of stem cells and their relevant properties and commonly used scaffold formulations. Next, we discuss natural and synthetic scaffold materials typically used when engineering tissues, along with their associated advantages and drawbacks and gives examples of target applications. New approaches to engineering tissues, such as 3D bioprinting, are described as they provide exciting opportunities for future work along with current challenges that must be addressed. Thus, this review provides an overview of the available biomaterials for directing stem cell differentiation as a means of producing replacements for diseased or damaged tissues.

Cell population balance of cardiovascular spheroids derived from human induced pluripotent stem cells

Stem cell-derived cardiomyocytes and vascular cells can be used for a variety of applications such as studying human heart development and modelling human disease in culture. In particular, protocols based on modulation of Wnt signaling were able to produce high quality of cardiomyocytes or vascular cells from human pluripotent stem cells (hPSCs). However, the mechanism behind the development of 3D cardiovascular spheroids into either vascular or cardiac cells has not been well explored. Hippo/Yes-associated protein (YAP) signaling plays important roles in the regulation of organogenesis, but its impact on cardiovascular differentiation has been less evaluated. In this study, the effects of seeding density and a change in YAP signaling on 3D cardiovascular spheroids patterning from hPSCs were evaluated. Compared to 2D culture, 3D cardiovascular spheroids exhibited higher levels of sarcomeric striations and higher length-to-width ratios of α-actinin⁺ cells. The spheroids with high seeding density exhibited more α-actinin⁺ cells and less nuclear YAP expression. The 3D cardiovascular spheroids were also treated with different small molecules, including Rho kinase inhibitor (Y27632), Cytochalasin D, Dasatinib, and Lysophosphatidic acid to modulate YAP localization. Nuclear YAP inhibition resulted in lower expression of active β-catenin, vascular marker, and MRTF, the transcription factor mediated by RhoGTPases. Y27632 also promoted the gene expression of MMP-2/-3 (matrix remodeling) and Notch-1 (Notch signaling). These results should help our understanding of the underlying effects for the efficient patterning of cardiovascular spheroids after mesoderm formation from hPSCs.

Tissue-Level Mechanosensitivity: Predicting and Controlling the Orientation of 3D Vascular Networks

Understanding the mechanosensitivity of tissues is a fundamentally important problem having far-reaching implications for tissue engineering. Here we study vascular networks formed by a coculture of fibroblasts and endothelial cells embedded in three-dimensional biomaterials experiencing external, physiologically relevant forces. We show that cyclic stretching of the biomaterial orients the newly formed network perpendicular to the stretching direction, independent of the geometric aspect ratio of the biomaterial's sample. A two-dimensional theory explains this observation in terms of the network's stored elastic energy if the cell-embedded biomaterial features a vanishing effective Poisson's ratio, which we directly verify. We further show that under a static stretch, vascular networks orient parallel to the stretching direction due to force-induced anisotropy of the biomaterial polymer network. Finally, static stretching followed by cyclic stretching reveals a competition between the two mechanosensitive mechanisms. These results demonstrate tissue-level mechanosensitivity and constitute an important step toward developing enhanced tissue repair capabilities using well-oriented vascular networks.

Biomaterial Engineering for Controlling Pluripotent Stem Cell Fate

Pluripotent stem cells (PSCs) represent an exciting cell source for tissue engineering and regenerative medicine due to their self-renewal and differentiation capacities. The majority of current PSC protocols rely on 2D cultures and soluble factors to guide differentiation; however, many other environmental signals are beginning to be explored using biomaterial platforms. Biomaterials offer new opportunities to engineer the stem cell niches and 3D environments for exploring biophysical and immobilized signaling cues to further our control over stem cell fate. Here, we review the biomaterial platforms that have been engineered to control PSC fate. We explore how altering immobilized biochemical cues and biophysical cues such as dimensionality, stiffness, and topography can enhance our control over stem cell fates. Finally, we highlight biomaterial culture systems that assist in the translation of PSC technologies for clinical applications.

Modeling Disease with Human Inducible Pluripotent Stem Cells

Understanding the physiopathology of disease remains an essential step in developing novel therapeutics. Although animal models have certainly contributed to advancing this enterprise, their limitation in modeling all the aspects of complex human disorders is one of the major challenges faced by the biomedical research field. Human induced pluripotent stem cells (hiPSCs) derived from patients represent a great opportunity to overcome this deficiency because these cells cover the genetic diversity needed to fully model human diseases. Here, we provide an overview of the history of hiPSC technology and discuss common challenges and approaches that we and others have faced when using hiPSCs to model disease. Our emphasis is on liver disease, and consequently, we review the progress made using this technology to produce functional liver cells in vitro and how these systems are being used to recapitulate a diversity of developmental, metabolic, genetic, and infectious liver disorders.

Substrate elasticity regulates vascular endothelial growth factor A (VEGFA) expression in adipose-derived stromal cells: Implications for potential angiogenesis

Adipose-derived stromal cells (ASCs) have potential in bioengineering angiogenesis due to their paracrine role in supporting endothelial tubulogenesis and vascular network formation. However, the precise mechanism of the inner angiogenic capacity of ASCs determined by the biophysical properties of the extracellular matrix needs to be further elucidated. In the current study, we fabricated two silicon-based elastomer polydimethylsiloxane (PDMS) substrates with different stiffnesses (stiff substrate, E = 195 kPa and soft substrate, E = 15 kPa) and found there were cytoskeletal changes in ASCs in response to different substrate stiffnesses. We then showed the expression of vinculin in focal adhesion plaques was enhanced and the nuclear translocation of β-catenin signaling was increased in ASCs on the stiff substrate relative to those on the soft substrate. We next used bioinformatics and found the downstream proteins of β-catenin signaling had binding sites in the promoter of vascular endothelial growth factor A (VEGFA), which is responsible for angiogenesis; then, we further confirmed the enhanced endogenous VEGFA expression in ASCs on the stiff substrate relative to that on the soft substrate. Finally, by using ectogenic VEGFA, we showed the stiff substrate could promote angiogenesis of ASCs in the form of more ring-like formations in 2D and vessel-like structure formations in 3D under VEGFA induction compared to that of the soft substrate. This study not only indicates the inner angiogenic capacity of ASCs but also elucidates the influence of substrate elasticity on ASC differentiation in bioengineering angiogenesis.

Cytoskeletal tension regulates mesodermal spatial organization and subsequent vascular fate

Morphogenesis during human development relies on the interplay between physiochemical cues that are mediated in part by cellular density and cytoskeletal tension. Here, we interrogated these factors on vascular lineage specification during human-induced pluripotent stem-cell (hiPSC) fate decision. We found that independent of chemical cues, spatially presented physical cues induce the self-organization of Brachyury-positive mesodermal cells, in a RhoA/Rho-associated kinase (ROCK)-dependent manner. Using unbiased support vector machine (SVM) learning, we found that density alone is sufficient to predict mesodermal fate. Furthermore, the long-withstanding presentation of spatial confinement during hiPSC differentiation led to an organized vascular tissue, reminiscent of native blood vessels, a process dependent on cell density as found by SVM analysis. Collectively, these results show how tension and density relate to vascular identity mirroring early morphogenesis. We propose that such a system can be applied to study other aspects of the stem-cell niche and its role in embryonic patterning.

miR-33a hinders the differentiation of adipose mesenchymal stem cells towards urothelial cells in an inductive condition by targeting β‑catenin and TGFR

Tissue engineering technology offers an appealing approach for tissue reconstruction of the urothelium. Adipose-derived mesenchymal stem cells (ADSCs) represent an abundant source for tissue engineering applications. However, ASCs primarily possess mesoderm lineage differentiation potential. It is difficult to induce differentiation of ASCs towards urothelial cells that are derived from the endoderm, although a recent findings have reported that a conditioned medium may drive ADSCs towards differentiation into the urothelium phenotype. In the present study, human ADSCs were isolated from abdominal adipose tissues and incubated in this conditioned medium for indicated time periods. Western blotting showed that protein expression levels of urothelial specific marks, including CK7, CK20 and UPIII, were increased after seven days' incubation, but immunofluorescence microscopy determined that cells with CK7 and UPIII staining were scarce, which suggested a low-efficiency for the differentiation. Prolonging the incubation time did not further increase CK20 and UPIII expression. Furthermore, miR-33a expression was increased with ADSC differentiation. Using synthetic miRNAs to mimic or inhibit the action of miR-33a revealed that miR-33a hinders the differentiation of ADSCs towards urothelial cells. Furthermore, luciferase reporter assay confirmed that β-catenin and transforming growth factor-β receptor (TGFR) are targets of miR-33a. Inhibition of miR-33a expression increased β-catenin and TGFR expression and improved the efficiency of ADSCs towards differentiation into the urothelium phenotype. The present novel finding suggests that miR-33 may be an important target in tissue engineering and regenerative medicine for urothelium repair.