Control of stem cell fate and function by engineering physical microenvironments

Stiffness assisted cell-matrix remodeling trigger 3D mechanotransduction regulatory programs

Engineered matrices provide a valuable platform to understand the impact of biophysical factors on cellular behavior such as migration, proliferation, differentiation, and tissue remodeling, through mechanotransduction. While recent studies have identified some mechanisms of 3D mechanotransduction, there is still a critical knowledge gap in comprehending the interplay between 3D confinement, ECM properties, and cellular behavior. Specifically, the role of matrix stiffness in directing cellular fate in 3D microenvironment, independent of viscoelasticity, microstructure, and ligand density remains poorly understood. To address this gap, we designed a nanoparticle crosslinker to reinforce collagen-based hydrogels without altering their chemical composition, microstructure, viscoelasticity, and density of cell-adhesion ligand and utilized it to understand cellular dynamics. This crosslinking mechanism utilizes nanoparticles as crosslink epicenter, resulting in 10-fold increase in mechanical stiffness, without other changes. Human mesenchymal stem cells (hMSCs) encapsulated in 3D responded to mechanical stiffness by displaying circular morphology on soft hydrogels (5 kPa) and elongated morphology on stiff hydrogels (30 kPa). Stiff hydrogels facilitated the production and remodeling of nascent extracellular matrix (ECM) and activated mechanotransduction cascade. These changes were driven through intracellular PI3AKT signaling, regulation of epigenetic modifiers and activation of YAP/TAZ signaling. Overall, our study introduces a unique biomaterials platform to understand cell-ECM mechanotransduction in 3D for regenerative medicine as well as disease modelling.

The Role of Stem Cell on Wound Healing After Revascularization-Healing Following Revascularization-Unlocking Skin Potential

Wound healing is a complex and dynamic process involving a series of cellular and molecular events. Revascularization, the restoration of blood flow to ischemic or damaged tissue, is a key step in wound healing. Adequate vascularization has been recognized as a necessary factor for successful tissue regeneration. In the later stage of revascularization and tissue remodeling in wound healing, stem cells regulate other repair cells and matrix formation by influencing the maturation of blood vessels. The reductive oxidation (REDOX) state may be a key mechanism through stem/progenitor cells to influence endothelial cells to mature blood vessels and improve the quality of healing. Mitochondria may play an important role in this process.

Regulated Behavior in Living Cells with Highly Aligned Configurations on Nanowrinkled Graphene Oxide Substrates: Deep Learning Based on Interplay of Cellular Contact Guidance

Micro-/nanotopographical cues have emerged as a practical and promising strategy for controlling cell fate and reprogramming, which play a key role as biophysical regulators in diverse cellular processes and behaviors. Extracellular biophysical factors can trigger intracellular physiological signaling via mechanotransduction and promote cellular responses such as cell adhesion, migration, proliferation, gene/protein expression, and differentiation. Here, we engineered a highly ordered nanowrinkled graphene oxide (GO) surface via the mechanical deformation of an ultrathin GO film on an elastomeric substrate to observe specific cellular responses based on surface-mediated topographical cues. The ultrathin GO film on the uniaxially prestrained elastomeric substrate through self-assembly and subsequent compressive force produced GO nanowrinkles with periodic amplitude. To examine the acute cellular behaviors on the GO-based cell interface with nanostructured arrays of wrinkles, we cultured L929 fibroblasts and HT22 hippocampal neuronal cells. As a result, our developed cell-culture substrate obviously provided a directional guidance effect. In addition, based on the observed results, we adapted a deep learning (DL)-based data processing technique to precisely interpret the cell behaviors on the nanowrinkled GO surfaces. According to the learning/transfer learning protocol of the DL network, we detected cell boundaries, elongation, and orientation and quantitatively evaluated cell velocity, traveling distance, displacement, and orientation. The presented experimental results have intriguing implications such that the nanotopographical microenvironment could engineer the living cells' morphological polarization to assemble them into useful tissue chips consisting of multiple cell types.

Highly Aligned Ternary Nanofiber Matrices Loaded with MXene Expedite Regeneration of Volumetric Muscle Loss

Current therapeutic approaches for volumetric muscle loss (VML) face challenges due to limited graft availability and insufficient bioactivities. To overcome these limitations, tissue-engineered scaffolds have emerged as a promising alternative. In this study, we developed aligned ternary nanofibrous matrices comprised of poly(lactide-co-ε-caprolactone) integrated with collagen and Ti3C2Tx MXene nanoparticles (NPs) (PCM matrices), and explored their myogenic potential for skeletal muscle tissue regeneration. The PCM matrices demonstrated favorable physicochemical properties, including structural uniformity, alignment, microporosity, and hydrophilicity. In vitro assays revealed that the PCM matrices promoted cellular behaviors and myogenic differentiation of C2C12 myoblasts. Moreover, in vivo experiments demonstrated enhanced muscle remodeling and recovery in mice treated with PCM matrices following VML injury. Mechanistic insights from next-generation sequencing revealed that MXene NPs facilitated protein and ion availability within PCM matrices, leading to elevated intracellular Ca2+ levels in myoblasts through the activation of inducible nitric oxide synthase (iNOS) and serum/glucocorticoid regulated kinase 1 (SGK1), ultimately promoting myogenic differentiation via the mTOR-AKT pathway. Additionally, upregulated iNOS and increased NO- contributed to myoblast proliferation and fiber fusion, thereby facilitating overall myoblast maturation. These findings underscore the potential of MXene NPs loaded within highly aligned matrices as therapeutic agents to promote skeletal muscle tissue recovery.

Regenerative bioelectronics: A strategic roadmap for precision medicine

In the past few decades, stem cell-based regenerative engineering has demonstrated its significant potential to repair damaged tissues and to restore their functionalities. Despite such advancement in regenerative engineering, the clinical translation remains a major challenge. In the stance of personalized treatment, the recent progress in bioelectronic medicine likewise evolved as another important research domain of larger significance for human healthcare. Over the last several years, our research group has adopted biomaterials-based regenerative engineering strategies using innovative bioelectronic stimulation protocols based on either electric or magnetic stimuli to direct cellular differentiation on engineered biomaterials with a range of elastic stiffness or functional properties (electroactivity/magnetoactivity). In this article, the role of bioelectronics in stem cell-based regenerative engineering has been critically analyzed to stimulate futuristic research in the treatment of degenerative diseases as well as to address some fundamental questions in stem cell biology. Built on the concepts from two independent biomedical research domains (regenerative engineering and bioelectronic medicine), we propose a converging research theme, 'Regenerative Bioelectronics'. Further, a series of recommendations have been put forward to address the current challenges in bridging the gap in stem cell therapy and bioelectronic medicine. Enacting the strategic blueprint of bioelectronic-based regenerative engineering can potentially deliver the unmet clinical needs for treating incurable degenerative diseases.

Protein ligand and nanotopography separately drive the phenotype of mouse embryonic stem cells

Biochemical and biomechanical signals regulate stem cell function in the niche environments in vivo. Current in vitro culture of mouse embryonic stem cells (mESC) uses laminin (LN-511) to provide mimetic biochemical signaling (LN-521 for human systems) to maintain stemness. Alternative approaches propose topographical cues to provide biomechanical cues, however combined biochemical and topographic cues may better mimic the in vivo environment, but are largely unexplored for in vitro stem cell expansion. In this study, we directly compare in vitro signals from LN-511 and/or topographic cues to maintain stemness, using systematically-varied submicron pillar patterns or flat surfaces with or without preadsorbed LN-511. The adhesion of cells, colony formation, expression of the pluripotency marker,octamer-binding transcription factor 4 (Oct4), and transcriptome profiling were characterized. We observed that either biochemical or topographic signals could maintain stemness of mESCs in feeder-free conditions, indicated by high-level Oct4 and gene profiling by RNAseq. The combination of LN-511 with nanotopography reduced colony growth, while maintaining stemness markers, shifted the cellular phenotype indicating that the integration of biochemical and topographic signals is antagonistic. Overall, significantly faster (up to 2.5 times) colony growth was observed at nanotopographies without LN-511, suggesting for improved ESC expansion.

Embryonic Stem Cells Can Generate Oral Epithelia under Matrix Instruction

We aimed to investigate whether molecular clues from the extracellular matrix (ECM) can induce oral epithelial differentiation of pluripotent stem cells. Mouse embryonic stem cells (ESC) of the feeder-independent cell line E14 were used as a model for pluripotent stem cells. They were first grown in 2D on various matrices in media containing vitamin C and without leukemia inhibitory factor (LIF). Matrices investigated were gelatin, laminin, and extracellular matrices (ECM) synthesized by primary normal oral fibroblasts and keratinocytes in culture. Differentiation into epithelial lineages was assessed by light microscopy, immunocytochemistry, and flow cytometry for cytokeratins and stem cell markers. ESC grown in 2D on various matrices were afterwards grown in 3D organotypic cultures with or without oral fibroblasts in the collagen matrix and examined histologically and by immunohistochemistry for epithelial (keratin pairs 1/10 and 4/13 to distinguish epidermal from oral epithelia and keratins 8,18,19 to phenotype simple epithelia) and mesenchymal (vimentin) phenotypes. ECM synthesized by either oral fibroblasts or keratinocytes was able to induce, in 2D cultures, the expression of cytokeratins of the stratified epithelial phenotype. When grown in 3D, all ESC developed into two morphologically distinct cell populations on collagen gels: (i) epithelial-like cells organized in islands with occasional cyst- or duct-like structures and (ii) spindle-shaped cells suggestive of mesenchymal differentiation. The 3D culture on oral fibroblast-populated collagen matrices was necessary for further differentiation into oral epithelia. Only ESC initially grown on 2D keratinocyte or fibroblast-synthesized matrices reached full epithelial maturation. In conclusion, ESC can generate oral epithelia under matrix instruction.

Biosensors integrated 3D organoid/organ-on-a-chip system: A real-time biomechanical, biophysical, and biochemical monitoring and characterization

As a full-fidelity simulation of human cells, tissues, organs, and even systems at the microscopic scale, Organ-on-a-Chip (OOC) has significant ethical advantages and development potential compared to animal experiments. The need for the design of new drug high-throughput screening platforms and the mechanistic study of human tissues/organs under pathological conditions, the evolving advances in 3D cell biology and engineering, etc., have promoted the updating of technologies in this field, such as the iteration of chip materials and 3D printing, which in turn facilitate the connection of complex multi-organs-on-chips for simulation and the further development of technology-composite new drug high-throughput screening platforms. As the most critical part of organ-on-a-chip design and practical application, verifying the success of organ model modeling, i.e., evaluating various biochemical and physical parameters in OOC devices, is crucial. Therefore, this paper provides a logical and comprehensive review and discussion of the advances in organ-on-a-chip detection and evaluation technologies from a broad perspective, covering the directions of tissue engineering scaffolds, microenvironment, single/multi-organ function, and stimulus-based evaluation, and provides a more comprehensive review of the progress in the significant organ-on-a-chip research areas in the physiological state.

Engineering of an Osteoinductive and Growth Factor-Free Injectable Bone-Like Microgel for Bone Regeneration

Bone autografts remain the gold standard for bone grafting surgeries despite having increased donor site morbidity and limited availability. Bone morphogenetic protein-loaded grafts represent another successful commercial alternative. However, the therapeutic use of recombinant growth factors has been associated with significant adverse clinical outcomes. This highlights the need to develop biomaterials that closely approximate the structure and composition of bone autografts, which are inherently osteoinductive and biologically active with embedded living cells, without the need for added supplements. Here, injectable growth factor-free bone-like tissue constructs are developed, that closely approximate the cellular, structural, and chemical composition of bone autografts. It is demonstrated that these micro-constructs are inherently osteogenic, and demonstrate the ability to stimulate mineralized tissue formation and regenerate bone in critical-sized defects in-vivo. Furthermore, the mechanisms that allow human mesenchymal stem cells (hMSCs) to be highly osteogenic in these constructs, despite the lack of osteoinductive supplements, are assessed, whereby Yes activated protein (YAP) nuclear localization and adenosine signaling appear to regulate osteogenic cell differentiation. The findings represent a step toward a new class of minimally invasive, injectable, and inherently osteoinductive scaffolds, which are regenerative by virtue of their ability to mimic the tissue cellular and extracellular microenvironment, thus showing promise for clinical applications in regenerative engineering.

PDMS Micropatterns Coated with PDA and RGD Induce a Regulatory Macrophage-like Phenotype

Regulatory macrophages (Mreg) are a special cell type that present a potential therapeutic strategy for various inflammatory diseases. In vitro, Mreg generation mainly takes 7-10 days of treatment with chemicals, including cytokines. In the present study, we established a new approach for Mreg generation using a three-dimensional (3D) micropatterned polydimethylsiloxane (PDMS) surface coated with a natural biopolymer adhesive polydopamine (PDA) and the common cell adhesion peptide motif arginylglycylaspartic acid (RGD). The 3D PDMS surfaces were fabricated by photolithography and soft lithography techniques and were subsequently coated with an RGD+PDA mixture to form a surface that facilitates cell adhesion. Human monocytes (THP-1 cells) were cultured on different types of 2D or 3D micropatterns for four days, and the cell morphology, elongation, and Mreg marker expression were assessed using microscopic and flow cytometric analyses. The cells grown on the PDA+RGD-coated 3D micropatterns (20-µm width/20-µm space) exhibited the most elongated morphology and strongest expression levels of Mreg markers, such as CD163, CD206, CD209, CD274, MER-TK, TREM2, and DHRS9. The present study demonstrated that PDA+RGD-coated 3D PDMS micropatterns successfully induced Mreg-like cells from THP-1 cells within four days without the use of cytokines, suggesting a time- and cost-effective method to generate Mreg-like cells in vitro.

Regulation of Traction Force through the Direct Binding of Basigin and Calpain 4

Traction force and mechanosensing (the ability to sense mechanical attributes of the environment) are two important factors used by a cell to modify behavior during migration. Previously it was determined that the calpain small subunit, calpain 4, regulates the production of traction force independent of its proteolytic holoenzyme. A proteolytic enzyme is formed by calpain4 binding to either of its catalytic partners, calpain 1 and 2. To further understand how calpain 4 regulates traction force, we used two-hybrid analysis to identify more components of the traction pathway. We discovered that basigin, an integral membrane protein and a documented matrix-metalloprotease (MMP) inducer binds to calpain 4 in two-hybrid and pull-down assays. Traction force was deficient when basigin was silenced in MEF cells, and defective in substrate adhesion strength. Consistent with Capn4 ^-/- MEF cells, the cells deficient in basigin responded to localized stimuli. Together these results implicate basigin in the pathway in which calpain 4 regulates traction force independent of the catalytic large subunits.

Elevated Serum Vinculin in Patients with HBV/HCV-Associated Liver Cirrhosis and Hepatocellular Carcinoma: A Pilot Study

Background

The stiffness of the extracellular matrix (ECM) controls many cellular processes, such as migration and differentiation. Cells detect stiffness through adhesion structures termed focal adhesions (FAs). Vinculin, an actin-binding FA protein, plays a pivotal role in FA-mediated mechanotransduction.

Aim

This study aimed to explore the role of vinculin in the development of HBV/HCV-induced hepatocellular carcinoma (HCC).

Methods

Vinculin levels in a total number of 100 serum samples from patients with HBV/HCV-induced liver cirrhosis and HCC, as well as healthy controls, were analyzed using an enzyme-linked immunosorbent assay (ELISA).

Results

In patients with HCC and liver cirrhosis, the serum vinculin levels were significantly greater than in controls (503.8±242.2 and 728.4±1044.8 vs 77.7±36.1 respectively, p<0.001). However, results showed no link between serum vinculin and the clinicopathological features of HCC.

Conclusion

Patients with HBVor HCV-induced liver cirrhosis and HCC have significantly higher serum levels of vinculin than do controls. This might point to a potential role for vinculin in the development of HCC. More research into how this protein affects the development of HCC at the molecular level could lead to better clinical treatments and the development of new molecular therapies.

Nanocomposite Hydrogels as Functional Extracellular Matrices

Over recent years, nano-engineered materials have become an important component of artificial extracellular matrices. On one hand, these materials enable static enhancement of the bulk properties of cell scaffolds, for instance, they can alter mechanical properties or electrical conductivity, in order to better mimic the in vivo cell environment. Yet, many nanomaterials also exhibit dynamic, remotely tunable optical, electrical, magnetic, or acoustic properties, and therefore, can be used to non-invasively deliver localized, dynamic stimuli to cells cultured in artificial ECMs in three dimensions. Vice versa, the same, functional nanomaterials, can also report changing environmental conditions-whether or not, as a result of a dynamically applied stimulus-and as such provide means for wireless, long-term monitoring of the cell status inside the culture. In this review article, we present an overview of the technological advances regarding the incorporation of functional nanomaterials in artificial extracellular matrices, highlighting both passive and dynamically tunable nano-engineered components.

How Mechanical and Physicochemical Material Characteristics Influence Adipose-Derived Stem Cell Fate

Adipose-derived stem cells (ASCs) are a subpopulation of mesenchymal stem cells. Compared to bone marrow-derived stem cells, they can be harvested with minimal invasiveness. ASCs can be easily expanded and were shown to be able to differentiate into several clinically relevant cell types. Therefore, this cell type represents a promising component in various tissue engineering and medical approaches (e.g., cell therapy). In vivo cells are surrounded by the extracellular matrix (ECM) that provides a wide range of tissue-specific physical and chemical cues, such as stiffness, topography, and chemical composition. Cells can sense the characteristics of their ECM and respond to them in a specific cellular behavior (e.g., proliferation or differentiation). Thus, in vitro biomaterial properties represent an important tool to control ASCs behavior. In this review, we give an overview of the current research in the mechanosensing of ASCs and current studies investigating the impact of material stiffens, topography, and chemical modification on ASC behavior. Additionally, we outline the use of natural ECM as a biomaterial and its interaction with ASCs regarding cellular behavior.

Physical and biological advances in endothelial cell-based engineered co-culture model systems

Scientific knowledge in the field of cell biology and mechanobiology heavily leans on cell-based in vitro experiments and models that favor the examination and comprehension of certain biological processes and occurrences across a variety of environments. Cell culture assays are an invaluable instrument for a vast spectrum of biomedical and biophysical investigations. The quality of experimental models in terms of simplicity, reproducibility, and combinability with other methods, and in particular the scale at which they depict cell fate in native tissues, is critical to advancing the knowledge of the comprehension of cell-cell and cell-matrix interactions in tissues and organs. Typically, in vitro models are centered on the experimental tinkering of mammalian cells, most often cultured as monolayers on planar, two-dimensional (2D) materials. Notwithstanding the significant advances and numerous findings that have been accomplished with flat biology models, their usefulness for generating further new biological understanding is constrained because the simple 2D setting does not reproduce the physiological response of cells in natural living tissues. In addition, the co-culture systems in a 2D stetting weakly mirror their natural environment of tissues and organs. Significant advances in 3D cell biology and matrix engineering have resulted in the creation and establishment of a new type of cell culture shapes that more accurately represents the in vivo microenvironment and allows cells and their interactions to be analyzed in a biomimetic approach. Contemporary biomedical and biophysical science has novel advances in technology that permit the design of more challenging and resilient in vitro models for tissue engineering, with a particular focus on scaffold- or hydrogel-based formats, organotypic cultures, and organs-on-chips, which cover the purposes of co-cultures. Even these complex systems must be kept as simplified as possible in order to grasp a particular section of physiology too very precisely. In particular, it is highly appreciated that they bridge the space between conventional animal research and human (patho)physiology. In this review, the recent progress in 3D biomimetic culturation is presented with a special focus on co-cultures, with an emphasis on the technological building blocks and endothelium-based co-culture models in cancer research that are available for the development of more physiologically relevant in vitro models of human tissues under normal and diseased conditions. Through applications and samples of various physiological and disease models, it is possible to identify the frontiers and future engagement issues that will have to be tackled to integrate synthetic biomimetic culture systems far more successfully into biomedical and biophysical investigations.

Biomaterials directed activation of a cryostable therapeutic secretome in induced pluripotent stem cell derived mesenchymal stromal cells

Mesenchymal stem cell therapy has suffered from wide variability in clinical efficacy, largely due to heterogeneous starting cell populations and large-scale cell death during and after implantation. Optimizing the manufacturing process has led to reproducible cell populations that can be cryopreserved for clinical applications. Nevertheless, ensuring a reproducible cell state that persists after cryopreservation remains a significant challenge, and is necessary to ensure reproducible clinical outcomes. Here we demonstrate how matrix-conjugated hydrogel cell culture materials can normalize a population of induced pluripotent stem cell derived mesenchymal stem cells (iPSC-MSCs) to display a defined secretory profile that promotes enhanced neovascularization in vitro and in vivo. Using a protein-conjugated biomaterials screen we identified two conditions-1 kPa collagen and 10 kPa fibronectin coated polyacrylamide gels-that promote reproducible secretion of pro-angiogenic and immunomodulatory cytokines from iPSC-MSCs that enhance tubulogenesis of endothelial cells in Geltrex and neovascularization in chick chorioallantoic membranes. Using defined culture substrates alone, we demonstrate maintenance of secretory activity after cryopreservation for the first time. This advance provides a simple and scalable approach for cell engineering and subsequent manufacturing, toward normalizing and priming a desired cell activity for clinical regenerative medicine.

Advances in Concentration Gradient Generation Approaches in a Microfluidic Device for Toxicity Analysis

This systematic review aimed to analyze the development and functionality of microfluidic concentration gradient generators (CGGs) for toxicological evaluation of different biological organisms. We searched articles using the keywords: concentration gradient generator, toxicity, and microfluidic device. Only 33 of the 352 articles found were included and examined regarding the fabrication of the microdevices, the characteristics of the CGG, the biological model, and the desired results. The main fabrication method was soft lithography, using polydimethylsiloxane (PDMS) material (91%) and SU-8 as the mold (58.3%). New technologies were applied to minimize shear and bubble problems, reduce costs, and accelerate prototyping. The Christmas tree CGG design and its variations were the most reported in the studies, as well as the convective method of generation (61%). Biological models included bacteria and nematodes for antibiotic screening, microalgae for pollutant toxicity, tumor and normal cells for, primarily, chemotherapy screening, and Zebrafish embryos for drug and metal developmental toxicity. The toxic effects of each concentration generated were evaluated mostly with imaging and microscopy techniques. This study showed an advantage of CGGs over other techniques and their applicability for several biological models. Even with soft lithography, PDMS, and Christmas tree being more popular in their respective categories, current studies aim to apply new technologies and intricate architectures to improve testing effectiveness and reduce common microfluidics problems, allowing for high applicability of toxicity tests in different medical and environmental models.

A reductionist approach to determine the effect of cell-cell contact on human epidermal stem cell differentiation

The balance between stem cell renewal and differentiation is determined by the interplay between intrinsic cellular controls and extrinsic factors presented by the microenvironment, or 'niche'. Previous studies on cultured human epidermis have utilised suspension culture and restricted cell spreading to investigate regulation of differentiation in single keratinocytes. However, keratinocytes are typically adherent to neighbouring cells in vivo. We therefore developed experimental models to investigate the combined effects of cell-ECM adhesion and cell-cell contact. We utilized lipid-modified oligonucleotides to form clusters of keratinocytes which were subsequently placed in suspension to induce terminal differentiation. In this experimental model cell-cell contact had no effect on suspension-induced differentiation of keratinocytes. We next developed a high-throughput platform for robust geometrical confinement of keratinocytes to hexagonal ECM-coated islands permitting direct cell-cell contact between single cells. As in the case of circular islands, differentiation was stimulated on the smallest single hexagonal islands. However, the percentage of involucrin-positive cells on small bowtie islands was significantly lower than on single islands, demonstrating that cell-cell contact reduced differentiation in response to decreased substrate adhesion. None of the small bowtie islands contained two involucrin-positive cells. Rather, if one cell was involucrin-positive the other was involucrin-negative. This suggests that there is intrinsic asymmetry in the effect of cell-cell contact in decreasing differentiation. Thus, our reductionist approaches provide new insights into the effect of the niche on keratinocyte differentiation. STATEMENT OF SIGNIFICANCE: Stem cell behaviour is regulated by a combination of external signals, including the nature of the adhesive substrate and cell-cell interactions. An understanding of how different signals are integrated creates the possibility of developing new biomaterials to promote tissue regeneration and broaden our understanding of skin diseases such as eczema and psoriasis, in which stem cell proliferation and differentiation are perturbed. In this study we have applied two methods to engineer intercellular adhesion of human epidermal stem cells, one involving lipid-modified DNA and the other involving hexagonal micropatterns. We show that the effect of cell-cell adhesion depends on cell-substrate adhesion and uncover evidence that two cells in equivalent environments can nevertheless behave differently.

Three-Dimensional Poly-(ε-Caprolactone) Nanofibrous Scaffolds Promote the Maturation of Human Pluripotent Stem Cells-Induced Cardiomyocytes

Although pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) have been proved to be a new platform for heart regeneration, the lack of maturity significantly hinders the clinic application. Recent researches indicate that the function of stem cell is associated with the nanoscale geometry/topography of the extracellular matrix (ECM). However, the effects of 3D nanofibrous scaffolds in maturation of iPSC-CMs still remain unclear. Thus, we explored the effects of restructuring iPSC-CMs in 3D nano-scaffolds on cell morphology, cardiac-specific structural protein, gap junction and calcium transient kinetics. Using the electrospinning technology, poly-(ε-caprolactone) (PCL) nanofibrous scaffold were constructed and iPSC-CMs were seeded into these forms. As expected, strong sarcolemmal remodeling processes and myofilament reorientation were observed in 3D nano-scaffolds culture, as well as more expression of cardiac mature proteins, such as β-MHC and MLC2v. The mature morphology of 3D-shaped iPSC-CMs leaded to enhanced calcium transient kinetics, with increased calcium peak transient amplitude and the maximum upstroke velocity (Vmax). The results revealed that the maturation of iPSC-CMs was enhanced by the electrospun 3D PCL nanofibrous scaffolds treatment. These findings also proposed a feasible strategy to improve the myocardium bioengineering by combining stem cells with scaffolds.

Combinatorial wound healing therapy using adhesive nanofibrous membrane equipped with wearable LED patches for photobiomodulation

Wound healing is the dynamic tissue regeneration process replacing devitalized and missing tissue layers. With the development of photomedicine techniques in wound healing, safe and noninvasive photobiomodulation therapy is receiving attention. Effective wound management in photobiomodulation is challenged, however, by limited control of the geometrical mismatches on the injured skin surface. Here, adhesive hyaluronic acid-based gelatin nanofibrous membranes integrated with multiple light-emitting diode (LED) arrays are developed as a skin-attachable patch. The nanofibrous wound dressing is expected to mimic the three-dimensional structure of the extracellular matrix, and its adhesiveness allows tight coupling between the wound sites and the flexible LED patch. Experimental results demonstrate that our medical device accelerates the initial wound healing process by the synergetic effects of the wound dressing and LED irradiation. Our proposed technology promises progress for wound healing management and other biomedical applications.

Novel electrospun conduit based on polyurethane/collagen enhanced by nanobioglass for peripheral nerve tissue engineering

Peripheral nerve injury can significantly affect the daily life of individuals with impaired nerve function and permanent nerve deformity. One of the most common treatments is autograft transplantation. Tissue engineering is one of the efficient methods to regenerate injured nerves using scaffolds, cells, and growth factors. Conduits, which are produced by a variety of techniques, could be used as an alternative treatment for patients with damaged nerves. The electrospinning technique is one of the most important and widely used methods for generating nanofiber conduits from biocompatible polymers. In this study, using the electrospinning method, three different conduits, including polyurethane (PU), polyurethane/collagen (PU/C), and a new conduit based on polyurethane + collagen + nanobioglass (PU/C/NBG), were prepared. The characteristics of these three types of conduits were evaluated by SEM, XRD, and various experiments, including porosity, degradation, contact angle, DMTA, FTIR, MTT, and DAPI staining. The results of MTT and DAPI assays revealed the safety of conduits and proper cell attachment. Overall, the results obtained from various experiments showed that the novel PU/C/NBG conduit has better mechanical properties in terms of porosity, hydrophilicity, and biocompatibility in comparison with PU and PU/C conduits and could be a suitable candidate for peripheral nerve regeneration and axonal growth due to its repair potential.

Biomaterials as a Vital Frontier for Stem Cell-Based Tissue Regeneration

Biomaterials and tissue regeneration represent two fields of intense research and rapid advancement. Their combination allowed the utilization of the different characteristics of biomaterials to enhance the expansion of stem cells or their differentiation into various lineages. Furthermore, the use of biomaterials in tissue regeneration would help in the creation of larger tissue constructs that can allow for significant clinical application. Several studies investigated the role of one or more biomaterial on stem cell characteristics or their differentiation potential into a certain target. In order to achieve real advancement in the field of stem cell-based tissue regeneration, a careful analysis of the currently published information is critically needed. This review describes the fundamental description of biomaterials as well as their classification according to their source, bioactivity and different biological effects. The effect of different biomaterials on stem cell expansion and differentiation into the primarily studied lineages was further discussed. In conclusion, biomaterials should be considered as an essential component of stem cell differentiation strategies. An intense investigation is still required. Establishing a consortium of stem cell biologists and biomaterial developers would help in a systematic development of this field.

Design of experiments approach to developing a robust ink for bioprinting

Despite advancements in tissue engineering, the methods used to generate three-dimensional (3D)in vitromodels for rapid screening and characterization studies remain time and labor intensive. Bioprinting offers an opportunity to offset these limitations by providing a scalable, high-throughput method with precise control over biomaterial scaffold and cellular deposition. However, the process of formulating bioinks can be complex in terms of balancing the mechanical integrity of a bioscaffold and viability of cells. One key factor, especially in alginate-based bioinks, is the rate of bioscaffold dissolution. It must allow cells to replace the bioscaffold with extracellular matrix (ECM), yet remain durable during extended tissue culture. This study uses a Design of Experiments (DoE) approach to understand the dependencies of multiple variables involved in the formulation and processing of an alginate-based bioink. The focus of the DoE was to understand the effects of hydrogel composition on bioink durability while maintaining cell viability. Three ingredients were varied in all: alginate, nanocellulose, and fibrinogen. Their effects on the bioink were then measured with respect to extrudability, strength, and stiffness as determined by dynamic mechanical analysis (DMA). The DoE demonstrated that mechanical integrity increased with increasing alginate concentration. In contrast, fibrinogen and nanofibril concentration had no statistically significant effect. The optimized ink containing fibroblasts was printable using multiple nozzle sizes while also supporting fibroblast cell viability. DMA characterization further showed that the composition of the cell culture medium did not modulate the degradation rate of the hydrogel. Ultimately, the study outlines a methodology for formulating a bioink that will result in robust bioscaffolds forin vitromodel development.

DNA/Magnetic Nanoparticles Composite to Attenuate Glass Surface Nanotopography for Enhanced Mesenchymal Stem Cell Differentiation

Mesenchymal stem cells (MSCs) have extensive pluripotent potential to differentiate into various cell types, and thus they are an important tool for regenerative medicine and biomedical research. In this work, the differentiation of hTERT-transduced adipose-derived MSCs (hMSCs) into chondrocytes, adipocytes and osteoblasts on substrates with nanotopography generated by magnetic iron oxide nanoparticles (MNPs) and DNA was investigated. Citrate-stabilized MNPs were synthesized by the chemical co-precipitation method and sized around 10 nm according to microscopy studies. It was shown that MNPs@DNA coatings induced chondrogenesis and osteogenesis in hTERT-transduced MSCs. The cells had normal morphology and distribution of actin filaments. An increase in the concentration of magnetic nanoparticles resulted in a higher surface roughness and reduced the adhesion of cells to the substrate. A glass substrate modified with magnetic nanoparticles and DNA induced active chondrogenesis of hTERT-transduced MSC in a twice-diluted differentiation-inducing growth medium, suggesting the possible use of nanostructured MNPs@DNA coatings to obtain differentiated cells at a reduced level of growth factors.

The Role of Substrate Topography and Stiffness on MSC Cells Functions: Key Material Properties for Biomimetic Bone Tissue Engineering

The hypothesis of the present research is that by altering the substrate topography and/or stiffness to make it biomimetic, we can modulate cells behavior. Substrates with similar surface chemistry and varying stiffnesses and topographies were prepared. Bulk PCL and CNTs-reinforced PCL composites were manufactured by solvent casting method and electrospinning and further processed to obtain tunable moduli of elasticity in the range of few MPa. To ensure the same chemical profile for the substrates, a protein coating was added. Substrate topography and properties were investigated. Further on, the feedback of Wharton’s Jelly Umbilical Cord Mesenchymal Stem Cells to substrates characteristics was investigated. Solvent casting scaffolds displayed superior mechanical properties compared to the corresponding electrospun films. However, the biomimetic fibrous texture of the electrospun substrates induced improved feedback of the cells with respect to their viability and proliferation. Cells’ adhesion and differentiation was remarkably pronounced on solvent casting substrates compared to the electrospun substrates. Soft substates improved cells multiplication and migration, while stiff substrates induced differentiation into bone cells. Aspects related to the key factors and the ideal properties of substrates and microenvironments were clarified, aiming towards the deep understanding of the required optimum biomimetic features of biomaterials.

Sulfated Hydrogels in Intervertebral Disc and Cartilage Research

Hydrogels are commonly used for the 3D culture of musculoskeletal cells. Sulfated hydrogels, which have seen a growing interest over the past years, provide a microenvironment that help maintain the phenotype of chondrocytes and chondrocyte-like cells and can be used for sustained delivery of growth factors and other drugs. Sulfated hydrogels are hence valuable tools to improve cartilage and intervertebral disc tissue engineering. To further advance the utilization of these hydrogels, we identify and summarize the current knowledge about different sulfated hydrogels, highlight their beneficial effects in cartilage and disc research, and review the biofabrication processes most suitable to secure best quality assurance through deposition fidelity, repeatability, and attainment of biocompatible morphologies.

MMP modulated differentiation of mouse embryonic stem cells on engineered cell derived matrices

Stem cell differentiation is dictated by the dynamic crosstalk between cells and their underlying extracellular matrix. While the importance of matrix degradation mediated by enzymes such as matrix metalloproteinases (MMPs) in the context of cancer invasion is well established, the role of MMPs in stem cell differentiation remains relatively unexplored. Here we address this question by assaying MMP expression and activity during differentiation of mouse embryonic stem cells (mESCs) on mouse embryonic fibroblast (MEF) derived matrices (MEFDMs) of varying stiffness and composition. We show that mESC differentiation into different germ layers is associated with expression of several MMPs including MMP-11, 2, 17, 25 and 9, with MMP-9 detected in cell secreted media. Different extents of softening of the different MEFDMs led to altered integrin expression, activated distinct mechanotransduction and metabolic pathways, and induced expression of germ layer-specific markers. Inhibition of MMP proteolytic activity by the broad spectrum MMP inhibitor GM6001 led to alterations in germ layer commitment of the differentiating mESCs. Together, our results illustrate the effect of MMPs in regulating mESC differentiation on engineered cell derived matrices and establish MEFDMs as suitable substrates for understanding molecular mechanisms regulating stem cell development and for regenerative medicine applications.

Droplet microfluidic devices for organized stem cell differentiation into germ cells: capabilities and challenges

Demystifying the mechanisms that underlie germline development and gamete production is critical for expanding advanced therapies for infertile couples who cannot benefit from current infertility treatments. However, the low number of germ cells, particularly in the early stages of development, represents a serious challenge in obtaining sufficient materials required for research purposes. In this regard, pluripotent stem cells (PSCs) have provided an opportunity for producing an unlimited source of germ cells in vitro. Achieving this ambition is highly dependent on accurate stem cell niche reconstitution which is achievable through applying advanced cell engineering approaches. Recently, hydrogel microparticles (HMPs), as either microcarriers or microcapsules, have shown promising potential in providing an excellent 3-dimensional (3D) biomimetic microenvironment alongside the systematic bioactive agent delivery. In this review, recent studies of utilizing various HMP-based cell engineering strategies for appropriate niche reconstitution and efficient in vitro differentiation are highlighted with a special focus on the capabilities of droplet-based microfluidic (DBM) technology. We believe that a deep understanding of the current limitations and potentials of the DBM systems in integration with stem cell biology provides a bright future for germ cell research.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12551-021-00907-5.

Micro/nanoengineered technologies for human pluripotent stem cells maintenance and differentiation

Human pluripotent stem cells (hPSCs) are a promising source of cells for cell replacement-based therapies as well as modeling human development and diseases in vitro. However, achieving fate control of hPSC with a high yield and specificity remains challenging. The fate specification of hPSCs is regulated by biochemical and biomechanical cues in their environment. Driven by this knowledge, recent exciting advances in micro/nanoengineering have been leveraged to develop a broad range of tools for the generation of extracellular biomechanical and biochemical signals that determine the behavior of hPSCs. In this review, we summarize such micro/nanoengineered technologies for controlling hPSC fate and highlight the role of biochemical and biomechanical cues such as substrate rigidity, surface topography, and cellular confinement in the hPSC-based technologies that are on the horizon.

Regulation of stem cell fate using nanostructure-mediated physical signals

One of the major issues in tissue engineering is regulation of stem cell differentiation toward specific lineages. Unlike biological and chemical signals, physical signals with adjustable properties can be applied to stem cells in a timely and localized manner, thus making them a hot topic for research in the fields of biomaterials, tissue engineering, and cell biology. According to the signals sensed by cells, physical signals used for regulating stem cell fate can be classified into six categories: mechanical, light, thermal, electrical, acoustic, and magnetic. In most cases, external macroscopic physical fields cannot be used to modulate stem cell fate, as only the localized physical signals accepted by the surface receptors can regulate stem cell differentiation via nanoscale fibrin polysaccharide fibers. However, surface receptors related to certain kinds of physical signals are still unknown. Recently, significant progress has been made in the development of functional materials for energy conversion. Consequently, localized physical fields can be produced by absorbing energy from an external physical field and subsequently releasing another type of localized energy through functional nanostructures. Based on the above concepts, we propose a methodology that can be utilized for stem cell engineering and for the regulation of stem cell fate via nanostructure-mediated physical signals. In this review, the combined effect of various approaches and mechanisms of physical signals provides a perspective on stem cell fate promotion by nanostructure-mediated physical signals. We expect that this review will aid the development of remote-controlled and wireless platforms to physically guide stem cell differentiation both in vitro and in vivo, using optimized stimulation parameters and mechanistic investigations while driving the progress of research in the fields of materials science, cell biology, and clinical research.

3D-bioprinted BMSC-laden biomimetic multiphasic scaffolds for efficient repair of osteochondral defects in an osteoarthritic rat model

Osteochondral defect repair in osteoarthritis (OA) remains an unsolved clinical problem due to the lack of enough seed cells in the defect and chronic inflammation in the joint. To address this clinical need, we designed a bone marrow-derived mesenchymal stem cell (BMSC)-laden 3D-bioprinted multilayer scaffold with methacrylated hyaluronic acid (MeHA)/polycaprolactone incorporating kartogenin and β-TCP for osteochondral defect repair within each region. BMSC-laden MeHA was designed to actively introduce BMSCs in situ, and diclofenac sodium (DC)-incorporated matrix metalloproteinase-sensitive peptide-modified MeHA was induced on the BMSC-laden scaffold as an anti-inflammatory strategy. BMSCs in the scaffolds survived, proliferated, and produced large amounts of cartilage-specific extracellular matrix in vitro. The effect of BMSC-laden scaffolds on osteochondral defect repair was investigated in an animal model of medial meniscectomy-induced OA. BMSC-laden scaffolds facilitated chondrogenesis by promoting collagen II and suppressed interleukin 1β in osteochondral defects of the femoral trochlea. Congruently, BMSC-laden scaffolds significantly improved joint function of the injured leg with respect to the ground support force, paw grip force, and walk gait parameters. Therefore, this research demonstrates the potential of 3D-bioprinted BMSC-laden scaffolds to simultaneously inhibit joint inflammation and promote cartilage defect repair in OA joints.

Tissue Engineering and Its Potential to Reduce Prostate Cancer Treatment Sequelae-Narrative Review

Tissue engineering offers the possibility to overcome limitations of current management for postprostatectomy incontinence and ED. Developed in recent years biotechnological feasibility of mesenchymal stem cell isolation, in vitro cultivation and implantation became the basis for new cell-based therapies oriented to induce regeneration of adult tissue. The perspective to offer patients suffering from post-prostatectomy incontinence or erectile dysfunction minimal invasive one-time procedure utilizing autologous stem cell transplantation is desired management.

Direct Surface Modification of Polycaprolactone-Based Shape Memory Materials to Introduce Positive Charge Aiming to Enhance Cell Affinity

In this study, the introduction of a positive charge on the surface of a shape memory material was investigated to enhance cell affinity. To achieve this, the direct chemical modification of a material surface was proposed. Sheet-type, crosslinked poly(caprolactone-co-α-bromo-ɤ-butyrolactone) (poly(CL-co-BrBL)) were prepared, and the direct reaction of amino compounds with bromo groups was conducted on the material surface with a positive charge. Branched poly(CL-co-BrBL) was prepared, followed by the introduction of methacryloyl groups to each chain end. Using the branched macromonomers, stable and sheet-type materials were derived through UV-light irradiation. Then, the materials were soaked in an amino compound solution to react with the bromo groups under various conditions. Differential scanning calorimetry and surface analysis of the modified materials indicated that 10 vol% of N, N-dimethylethylenediamine in n-hexane and 1 h soaking time were optimal to maintain the inherent thermal properties. The achievement of increased luminance and a positive zeta potential proved that the direct modification method effectively introduced the positive charge only on the surface, thereby enhancing cell affinity.

Effect of Polymeric Matrix Stiffness on Osteogenic Differentiation of Mesenchymal Stem/Progenitor Cells: Concise Review

Mesenchymal stem/progenitor cells (MSCs) have a multi-differentiation potential into specialized cell types, with remarkable regenerative and therapeutic results. Several factors could trigger the differentiation of MSCs into specific lineages, among them the biophysical and chemical characteristics of the extracellular matrix (ECM), including its stiffness, composition, topography, and mechanical properties. MSCs can sense and assess the stiffness of extracellular substrates through the process of mechanotransduction. Through this process, the extracellular matrix can govern and direct MSCs' lineage commitment through complex intracellular pathways. Hence, various biomimetic natural and synthetic polymeric matrices of tunable stiffness were developed and further investigated to mimic the MSCs' native tissues. Customizing scaffold materials to mimic cells' natural environment is of utmost importance during the process of tissue engineering. This review aims to highlight the regulatory role of matrix stiffness in directing the osteogenic differentiation of MSCs, addressing how MSCs sense and respond to their ECM, in addition to listing different polymeric biomaterials and methods used to alter their stiffness to dictate MSCs' differentiation towards the osteogenic lineage.

An Advanced 'clickECM' That Can be Modified by the Inverse-Electron-Demand Diels-Alder Reaction

The extracellular matrix (ECM) represents the natural environment of cells in tissue and therefore is a promising biomaterial in a variety of applications. Depending on the purpose, it is necessary to equip the ECM with specific addressable functional groups for further modification with bioactive molecules, for controllable cross-linking and/or covalent binding to surfaces. Metabolic glycoengineering (MGE) enables the specific modification of the ECM with such functional groups without affecting the native structure of the ECM. In a previous approach (S. M. Ruff, S. Keller, D. E. Wieland, V. Wittmann, G. E. M. Tovar, M. Bach, P. J. Kluger, Acta Biomater. 2017, 52, 159-170), we demonstrated the modification of an ECM with azido groups, which can be addressed by bioorthogonal copper-catalyzed azide-alkyne cycloaddition (CuAAC). Here, we demonstrate the modification of an ECM with dienophiles (terminal alkenes, cyclopropene), which can be addressed by an inverse-electron-demand Diels-Alder (IEDDA) reaction. This reaction is cell friendly as there are no cytotoxic catalysts needed. We show the equipment of the ECM with a bioactive molecule (enzyme) and prove that the functional groups do not influence cellular behavior. Thus, this new material has great potential for use as a biomaterial, which can be individually modified in a wide range of applications.

High-Throughput Routes to Biomaterials Discovery

Many existing clinical treatments are limited in their ability to completely restore decreased or lost tissue and organ function, an unenviable situation only further exacerbated by a globally aging population. As a result, the demand for new medical interventions has increased substantially over the past 20 years, with the burgeoning fields of gene therapy, tissue engineering, and regenerative medicine showing promise to offer solutions for full repair or replacement of damaged or aging tissues. Success in these fields, however, inherently relies on biomaterials that are engendered with the ability to provide the necessary biological cues mimicking native extracellular matrixes that support cell fate. Accelerating the development of such "directive" biomaterials requires a shift in current design practices toward those that enable rapid synthesis and characterization of polymeric materials and the coupling of these processes with techniques that enable similarly rapid quantification and optimization of the interactions between these new material systems and target cells and tissues. This manuscript reviews recent advances in combinatorial and high-throughput (HT) technologies applied to polymeric biomaterial synthesis, fabrication, and chemical, physical, and biological screening with targeted end-point applications in the fields of gene therapy, tissue engineering, and regenerative medicine. Limitations of, and future opportunities for, the further application of these research tools and methodologies are also discussed.

Novel low shear 3D bioreactor for high purity mesenchymal stem cell production

Bone marrow derived human Mesenchymal Stem Cells (hMSCs) are an attractive candidate for regenerative medicine. However, their harvest can be invasive, painful, and expensive, making it difficult to supply the enormous amount of pure hMSCs needed for future allogeneic therapies. Because of this, a robust method of scaled bioreactor culture must be designed to supply the need for high purity, high density hMSC yields. Here we test a scaled down model of a novel bioreactor consisting of an unsubmerged 3D printed Polylactic Acid (PLA) lattice matrix wetted by culture media. The growth matrix is uniform, replicable, and biocompatible, enabling homogenous cell culture in three dimensions. The goal of this study was to prove that hMSCs would culture well in this novel bioreactor design. The system tested resulted in comparable stem cell yields to other cell culture systems using bone marrow derived hMSCs, while maintaining viability (96.54% ±2.82), high purity (>98% expression of combined positive markers), and differentiation potential.

Caveolin-1 mediates soft scaffold-enhanced adipogenesis of human mesenchymal stem cells

BACKGROUND

Human bone marrow-derived mesenchymal stem cells (hBMSCs) can differentiate into adipocytes upon stimulation and are considered an appropriate cell source for adipose tissue engineering. In addition to biochemical cues, the stiffness of a substrate that cells attach to has also been shown to affect hBMSC differentiation potential. Of note, most current studies are conducted on monolayer cultures which do not directly inform adipose tissue engineering, where 3-dimensional (3D) scaffolds are often used to create proper tissue architecture. In this study, we aim to examine the adipogenic differentiation of hBMSCs within soft or stiff scaffolds and investigate the molecular mechanism mediating the response of hBMSCs to substrate stiffness in 3D culture, specifically the involvement of the integral membrane protein, caveolin-1 (CAV1), known to regulate signaling in MSCs via compartmentalizing and concentrating signaling molecules.

METHODS

By adjusting the photo-illumination time, photocrosslinkable gelatin scaffolds with the same polymer concentration but different stiffnesses were created. hBMSCs were seeded within soft and stiff scaffolds, and their response to adipogenic induction under different substrate mechanical conditions was characterized. The functional involvement of CAV1 was assessed by suppressing its expression level using CAV1-specific siRNA.

RESULTS

The soft and stiff scaffolds used in this study had a compressive modulus of ~0.5 kPa and ~23.5 kPa, respectively. hBMSCs showed high viability in both scaffold types, but only spread out in the soft scaffolds. hBMSCs cultured in soft scaffolds displayed significantly higher adipogenesis, as revealed by histology, qRT-PCR, and immunostaining. Interestingly, a lower CAV1 level was observed in hBMSCs in the soft scaffolds, concomitantly accompanied by increased levels of Yes-associated protein (YAP) and decreased YAP phosphorylation, when compared to cells seeded in the stiff scaffolds. Interestingly, reducing CAV1 expression with siRNA was shown to further enhance hBMSC adipogenesis, which may function through activation of the YAP signaling pathway.

CONCLUSIONS

Soft biomaterials support superior adipogenesis of encapsulated hBMSCs in 3D culture, which is partially mediated by the CAV1-YAP axis. Suppressing CAV1 expression levels represents a robust method in the promotion of hBMSC adipogenesis.

Study of Stem Cells Influence on Cardiac Cells Cultured with a Cyanide-P-Trifluoromethoxyphenylhydrazone in Organ-on-a-Chip System

Regenerative medicine and stem cells could prove to be an effective solution to the problem of treating heart failure caused by ischemic heart disease. However, further studies on the understanding of the processes which occur during the regeneration of damaged tissue are needed. Microfluidic systems, which provide conditions similar to in vivo, could be useful tools for the development of new therapies using stem cells. We investigated how mesenchymal stem cells (MSCs) affect the metabolic activity of cardiac cells (rat cardiomyoblasts and human cardiomyocytes) incubated with a potent uncoupler of mitochondrial oxidative phosphorylation under microfluidic conditions. A cyanide p-trifluoromethoxyphenylhydrazone (FCCP) was used to mimic disfunctions of mitochondria of cardiac cells. The study was performed in a microfluidic system integrated with nanofiber mats made of poly-l-lactid acid (PLLA) or polyurethane (PU). The microsystem geometry allows four different cell cultures to be conducted under different conditions (which we called: normal, abnormal-as both a mono- and co-culture). Metabolic activity of the cells, based on the bioluminescence assay, was assessed in the culture's performed in the microsystem. It was proved that stem cells increased metabolic activity of cardiac cells maintained with FCCP.

Edge-localized alteration in pluripotency state of mouse ES cells forming topography-confined layers on designed mesh substrates

Self-organization of pluripotent stem cells during tissue formation is directed by the adhesion microenvironment, which defines the resulting tissue topography. Although the influence of tissue topography on pluripotency state has been inferred, this aspect of self-organization remains largely unexplored. In this study, to determine the effect of self-organized tissue topography on pluripotency loss, we designed novel island mesh substrates to confine the self-organization process of mouse embryonic stem cells, enabling us to generate isolated cell layers with an island-like topography and overhanging edges. Using immunofluorescence microscopy, we determined that cells at the tissue edge exhibited deformed nuclei associated with low OCT3/4, in contrast with cells nested in the tissue interior which had round-shaped nuclei and exhibited sustained OCT3/4 expression. Interestingly, F-actin and phospho-myosin light chain were visibly enriched at the tissue edge where ERK activation and elevated AP-2γ expression were also found to be localized, as determined using both immunofluorescence microscopy and RT-qPCR analysis. Since actomyosin contractility is known to cause ERK activation, these results suggest that mechanical condition at the tissue edge can contribute to loss of pluripotency leading to differentiation. Thus, our study draws attention to the influence of self-organized tissue topography in stem cell culture and differentiation.

Modulation of Human Mesenchymal Stem Cells by Electrical Stimulation Using an Enzymatic Biofuel Cell

Enzymatic biofuel cells (EBFCs) have excellent potential as components in bioelectronic devices, especially as active biointerfaces to regulate stem cell behavior for regenerative medicine applications. However, it remains unclear to what extent EBFC-generated electrical stimulation can regulate the functional behavior of human adipose-derived mesenchymal stem cells (hAD-MSCs) at the morphological and gene expression levels. Herein, we investigated the effect of EBFC-generated electrical stimulation on hAD-MSC cell morphology and gene expression using next-generation RNA sequencing. We tested three different electrical currents, 127 ± 9, 248 ± 15, and 598 ± 75 nA/cm2, in mesenchymal stem cells. We performed transcriptome profiling to analyze the impact of EBFC-derived electrical current on gene expression using next generation sequencing (NGS). We also observed changes in cytoskeleton arrangement and analyzed gene expression that depends on the electrical stimulation. The electrical stimulation of EBFC changes cell morphology through cytoskeleton re-arrangement. In particular, the results of whole transcriptome NGS showed that specific gene clusters were up- or down-regulated depending on the magnitude of applied electrical current of EBFC. In conclusion, this study demonstrates that EBFC-generated electrical stimulation can influence the morphological and gene expression properties of stem cells; such capabilities can be useful for regenerative medicine applications such as bioelectronic devices.

Current Status and Challenges of Stem Cell Treatment for Alzheimer's Disease

Neurodegenerative diseases called tauopathies, such as Alzheimer's disease (AD), frontotemporal dementia, progressive supranuclear palsy, and Parkinson's disease, among others, are characterized by the pathological processing and accumulation of tau protein. AD is the most prevalent neurodegenerative disease and is characterized by two lesions: neurofibrillary tangles (NFTs) and neuritic plaques. The presence of NFTs in the hippocampus and neocortex in early and advanced stages, respectively, correlates with the patient's cognitive deterioration. So far, no drugs can prevent, decrease, or limit neuronal death due to abnormal pathological tau accumulation. Among potential non-pharmacological treatments, physical exercise has been shown to stimulate the development of stem cells (SCs) and may be useful in early stages. However, this does not prevent neuronal death from the massive accumulation of NFTs. In recent years, SCs therapies have emerged as a promising tool to repopulate areas involved in cognition in neurodegenerative diseases. Unfortunately, protocols for SCs therapy are still being developed and the mechanism of action of such therapy remains unclear. In this review, we show the advances and limitations of SCs therapy. Finally, we provide a critical analysis of its clinical use for AD.

Embedding cells within nanoscale, rapidly mineralizing hydrogels: A new paradigm to engineer cell-laden bone-like tissue

Bone mineralization is a highly specific and dynamic nanoscale process that has been studied extensively from a structural, chemical, and biological standpoint. Bone tissue, therefore, may be defined by the interplay of its intricately mineralized matrix and the cells that regulate its biological function. However, the far majority of engineered bone model systems and bone replacement materials have been unable to replicate this key characteristic of bone tissue; that is, the ability of cells to be gradually and rapidly embedded in a three-dimensional (3D) heavily calcified matrix material. Here we review the characteristics that define the bone matrix from a nanostructural perspective. We then revisit the benefits and challenges of existing model systems and engineered bone replacement materials, and discuss recent efforts to replicate the biological, cellular, mechanical, and materials characteristics of bone tissue on the nano- to microscale. We pay particular attention to a recently proposed method developed by our group, which seeks to replicate key aspects of the entrapment of bone cells within a mineralized matrix with precisions down to the level of individual nano-crystallites, inclusive of the bone vasculature, and osteogenic differentiation process. In summary, this paper discusses existing and emerging evidence pointing towards future developments bridging the gap between the fields of biomineralization, structural biology, stem cells, and tissue engineering, which we believe will hold the key to engineer truly functional bone-like tissue in the laboratory.

Biophysical and epigenetic regulation of cancer stemness, invasiveness and immune action

PURPOSE OF REVIEW

The tumor microenvironment (TME) is an amalgam of multiple dysregulated biophysical cues that can alter cellular behavior through mechanotransductive signaling and epigenetic modifications. Through this review, we seek to characterize the extent of biophysical and epigenetic regulation of cancer stemness and tumor-associated immune cells in order to identify ideal targets for cancer therapy.

RECENT FINDINGS

Recent studies have identified cancer stemness and immune action as significant contributors to neoplastic disease, due to their susceptibility to microenvironmental influences. Matrix stiffening, altered vasculature, and resultant hypoxia within the TME can influence cancer stem cell (CSC) and immune cell behavior, as well as alter the epigenetic landscapes involved in cancer development.

SUMMARY

This review highlights the importance of aberrant biophysical cues in driving cancer progression through altered behavior of CSCs and immune cells, which in turn sustains further biophysical dysregulation. We examine current and potential therapeutic approaches that break this self-sustaining cycle of disease progression by targeting the presented biophysical and epigenetic signatures of cancer. We also summarize strategies including the normalization of the TME, targeted drug delivery, and inhibition of cancer-enabling epigenetic players.

A Tissue Engineering Approach to Metastatic Colon Cancer

Colon cancer remains the third most common cause of cancer in the US, and the third most common cause of cancer death. Worldwide, colon cancer is the second most common cause of cancer and cancer deaths. At least 25% of patients still present with metastatic disease, and at least 25-30% will develop metastatic colon cancer in the course of their disease. While chemotherapy and surgery remain the mainstay of treatment, understanding the fundamental cellular niche and mechanical properties that result in metastases would facilitate both prevention and cure. Advances in biomaterials, novel 3D primary human cells, modelling using microfluidics and the ability to alter the physical environment, now offers a unique opportunity to develop and test impactful treatment.