Modulation of integrin and E-cadherin-mediated adhesions to spatially control heterogeneity in human pluripotent stem cell differentiation

A simple tool for the synchronous differentiation of human induced pluripotent stem cells into pancreatic progenitors

Efficient differentiation of human induced pluripotent stem cells (hiPSCs) into functional pancreatic cells holds great promise for diabetes research and treatment. However, a robust culture strategy for producing pancreatic progenitors with high homogeneity is lacking. Here, we established a simple differentiation strategy for generating synchronous iPSC-derived pancreatic progenitors via a two-step method of sequential cell synchronization using botulinum hemagglutinin (HA), an E-cadherin function-blocking agent. Of the various methods tested, the first-step synchronization method with HA exposure induces a synchronous switch from E- to N-cadherin and N- to E-cadherin expression by spatially controlling heterogeneous cell distribution, subsequently improving their competency for directed differentiation into definitive endodermal cells from iPSCs. The iPSC-derived definitive endodermal cells can efficiently generate PDX1+ and NKX6.1+ pancreatic progenitor cells in high yields. The PDX1+ and PDX1+ /NKX6.1+ cell densities showed 1.6- and 2.2-fold increases, respectively, compared with those from unsynchronized cultures. The intra-run and inter-run coefficient of variation were below 10%, indicating stable and robust differentiation across different cultures and runs. Our approach is a simple and efficient strategy to produce large quantities of differentiated cells with the highest homogeneity during multistage pancreatic progenitor differentiation, providing a potential tool for guided differentiation of iPSCs to functional insulin-producing cells.

Bioadhesive and Injectable Hydrogels and Their Correlation with Mesenchymal Stem Cells Differentiation for Cartilage Repair: A Mini-Review

Injectable bioadhesive hydrogels, known for their capacity to carry substances and adaptability in processing, offer great potential across various biomedical applications. They are especially promising in minimally invasive stem cell-based therapies for treating cartilage damage. This approach harnesses readily available mesenchymal stem cells (MSCs) to differentiate into chondrocytes for cartilage regeneration. In this review, we investigate the relationship between bioadhesion and MSC differentiation. We summarize the fundamental principles of bioadhesion and discuss recent trends in bioadhesive hydrogels. Furthermore, we highlight their specific applications in conjunction with stem cells, particularly in the context of cartilage repair. The review also encompasses a discussion on testing methods for bioadhesive hydrogels and direct techniques for differentiating MSCs into hyaline cartilage chondrocytes. These approaches are explored within both clinical and laboratory settings, including the use of genetic tools. While this review offers valuable insights into the interconnected aspects of these topics, it underscores the need for further research to fully grasp the complexities of their relationship.

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.

DUSP6 is a memory retention feedback regulator of ERK signaling for cellular resilience of human pluripotent stem cells in response to dissociation

Cultured human pluripotent stem cells (hPSCs) grow as colonies that require breakdown into small clumps for further propagation. Although cell death mechanism by single-cell dissociation of hPSCs has been well defined, how hPSCs respond to the deadly stimulus and recover the original status remains unclear. Here we show that dissociation of hPSCs immediately activates ERK, which subsequently activates RSK and induces DUSP6, an ERK-specific phosphatase. Although the activation is transient, DUSP6 expression persists days after passaging. DUSP6 depletion using the CRISPR/Cas9 system reveals that DUSP6 suppresses the ERK activity over the long term. Elevated ERK activity by DUSP6 depletion increases both viability of hPSCs after single-cell dissociation and differentiation propensity towards mesoderm and endoderm lineages. These findings provide new insights into how hPSCs respond to dissociation in order to maintain pluripotency.

An in vitro culture platform for studying the effect of collective cell migration on spatial self-organization within induced pluripotent stem cell colonies

BACKGROUND

Human induced pluripotent stem cells (hiPSCs) provide an in vitro system to identify the impact of cell behavior on the earliest stages of cell fate specification during human development. Here, we developed an hiPSC-based model to study the effect of collective cell migration in meso-endodermal lineage segregation and cell fate decisions through the control of space confinement using a detachable ring culture system.

RESULTS

The actomyosin organization of cells at the edge of undifferentiated colonies formed in a ring barrier differed from that of the cells in the center of the colony. In addition, even in the absence of exogenous supplements, ectoderm, mesoderm, endoderm, and extraembryonic cells differentiated following the induction of collective cell migration at the colony edge by removing the ring-barrier. However, when collective cell migration was inhibited by blocking E-cadherin function, this fate decision within an hiPSC colony was altered to an ectodermal fate. Furthermore, the induction of collective cell migration at the colony edge using an endodermal induction media enhanced endodermal differentiation efficiency in association with cadherin switching, which is involved in the epithelial-mesenchymal transition.

CONCLUSIONS

Our findings suggest that collective cell migration can be an effective way to drive the segregation of mesoderm and endoderm lineages, and cell fate decisions of hiPSCs.

Mechanobiology: A landscape for reinterpreting stem cell heterogeneity and regenerative potential in diseased tissues

Mechanical forces play a fundamental role in cellular dynamics from the molecular level to the establishment of complex heterogeneity in somatic and stem cells. Here, we highlight the role of cytoskeletal mechanics and extracellular matrix in generating mechanical forces merging into oscillatory synchronized patterns. We discuss how cellular mechanosensing/-transduction can be modulated by mechanical forces to control tissue metabolism and set the basis for nonpharmacologic tissue rescue. Control of bone anabolic activity and repair, as well as obesity prevention, through a fine-tuning of the stem cell morphodynamics are highlighted. We also discuss the use of mechanical forces in the treatment of cardiovascular diseases and heart failure through the fine modulation of stem cell metabolic activity and regenerative potential. We finally focus on the new landscape of delivering specific mechanical stimuli to reprogram tissue-resident stem cells and enhance our self-healing potential, without the need for stem cell or tissue transplantation.

Organoids

Organoids have attracted increasing attention because they are simple tissue-engineered cell-based in vitro models that recapitulate many aspects of the complex structure and function of the corresponding in vivo tissue. They can be dissected and interrogated for fundamental mechanistic studies on development, regeneration, and repair in human tissues. Organoids can also be used in diagnostics, disease modeling, drug discovery, and personalized medicine. Organoids are derived from either pluripotent or tissue-resident stem (embryonic or adult) or progenitor or differentiated cells from healthy or diseased tissues, such as tumors. To date, numerous organoid engineering strategies that support organoid culture and growth, proliferation, differentiation and maturation have been reported. This Primer serves to highlight the rationale underlying the selection and development of these materials and methods to control the cellular/tissue niche; and therefore, structure and function of the engineered organoid. We also discuss key considerations for generating robust organoids, such as those related to cell isolation and seeding, matrix and soluble factor selection, physical cues and integration. The general standards for data quality, reproducibility and deposition within the organoid community is also outlined. Lastly, we conclude by elaborating on the limitations of organoids in different applications, and key priorities in organoid engineering for the coming years.

Cell Behavioral Dynamics as a Cue in Optimizing Culture Stabilization in the Bioprocessing of Pluripotent Stem Cells

Pluripotent stem cells (PSCs) are important for future regenerative medicine therapies. However, in the production of PSCs and derivatives, the control of culture-induced fluctuations in the outcome of cell quality remains challenging. A detailed mechanistic understanding of how PSC behaviors are altered in response to biomechanical microenvironments within a culture is necessary for rational bioprocessing optimization. In this review, we discuss recent insights into the role of cell behavioral and mechanical homeostasis in modulating the states and functions of PSCs during culture processes. We delineate promising ways to manipulate the culture variability through regulating cell behaviors using currently developed tools. Furthermore, we anticipate their potential implementation for designing a culture strategy based on the concept of Waddington's epigenetic landscape that may provide a feasible solution for tuning the culture quality and stability in the bioprocessing space.

A chemically-defined plastic scaffold for the xeno-free production of human pluripotent stem cells

Clinical use of human pluripotent stem cells (hPSCs) is hampered by the technical limitations of their expansion. Here, we developed a chemically synthetic culture substrate for human pluripotent stem cell attachment and maintenance. The substrate comprises a hydrophobic polyvinyl butyral-based polymer (PVB) and a short peptide that enables easy and uniform coating of various types of cell culture ware. The coated ware exhibited thermotolerance, underwater stability and could be stored at room temperature. The substrate supported hPSC expansion in combination with most commercial culture media with an efficiency similar to that of commercial substrates. It supported not only the long-term expansion of examined iPS and ES cell lines with normal karyotypes during their undifferentiated state but also directed differentiation of three germ layers. This substrate resolves major concerns associated with currently used recombinant protein substrates and could be applied in large-scale automated manufacturing; it is suitable for affordable and stable production of clinical-grade hPSCs and hPSC-derived products.

Controlled domain gels with a biomimetic gradient environment for osteochondral tissue regeneration

In order to repair an osteochondral defect, it is critical to advance a bi-lineage constructive scaffold with gradient transition. In this study, we developed a simple and straightforward approach for fabricating a multi-domain gel scaffold through the assembly/disassembly of low-molecular-weight gels (LMWGs) inside a stable PEGDA network by photopolymerization. The versatility of this technology enabled to vary biological, topological, and mechanical properties through material selection and to generate a chondrogenic-osteogenic gradient transition. The multi-domain gel exhibited an increasing stiffness gradient along the longitudinal direction from the cartilage layer at approximately 20 kPa to the bone layer at approximately 300 kPa as well as spatial variation at the gradient interface. Moreover, the transitional layer with a condensed structure and intermediate stiffness prevented delamination of the contrasting layers and maintained microenvironmental differences in the upper and lower layers. The in vitro results indicated that each domain had an individual capacity to spatially control the differentiation of MSCs toward osteoblastic lineage and chondrocytic lineage. This was mainly because the mechanical and topographical cues from the respective domains played an important role in modulating the Rho-ROCK signaling pathway, whereas the blockage of ROCK signals significantly impaired domain-modulated osteogenesis and enhanced chondrogenesis. Additionally, the quantity and quality of osteochondral repair were evaluated at 4 and 8 weeks through histological analysis and micro-computed tomography (micro-CT). The results indicated that the multi-domain gels distinctly improved the regeneration of subchondral bone and cartilage tissues. Overall, the outcomes of this study can motivate future bioinspired gradient and heterogeneity strategies for osteochondral tissue regeneration. STATEMENT OF SIGNIFICANCE: The regeneration of osteochondral defects remains a major challenge due to the complexity of osteochondral structure and the limited self-repair capacity of cartilage. The gradient design to mimic the transition between the calcified cartilage and the subchondral bone plate as well as the zones of cartilage is an effective strategy. In this study, controlled multi-domain gels were fabricated through the assembly/disassembly of low-molecular-weight gels inside a stable PEGDA network by photopolymerization. The prepared multi-domain gels showed a chondrogenic-osteogenic gradient transition, which decreased the possibility of delamination and stimulated osteochondral tissue regeneration in vivo. Overall, our study promotes new strategies of bioinspired gradients and heterogeneities for more challenging applications.

Moderate mechanical stimulation rescues degenerative annulus fibrosus by suppressing caveolin-1 mediated pro-inflammatory signaling pathway

Mechanical loading can induce or antagonize the extracellular matrix (ECM) synthesis, proliferation, migration, and inflammatory responses of annulus fibrosus cells (AFCs), depending on the loading mode and level. Caveolin-1 (Cav1), the core protein of caveolae, plays an important role in cellular mechanotransduction and inflammatory responses. In the present study, we presented that AFCs demonstrated different behaviors when subjected to cyclic tensile strain (CTS) for 24 h at a magnitude of 0%, 2%, 5% and 12%, respectively. It was found that 5% CTS had positive effects on cell proliferation, migration and anabolism, while 12% CTS had the opposite effects. Besides, cells exposed to interleukin-1β stimulus exhibited an increase expression in inflammatory genes, and the expression of these genes decreased after exposure to moderate mechanical loading with 5% CTS. In addition, 5% CTS decreased the level of Cav1 and integrin β1 and exhibited anti-inflammatory effects. Moreover, the expression of integrin β1 and p-p65 increased in AFCs transfected with Cav1 plasmids. In vivo results revealed that moderate mechanical stimulation could recover the water content and morphology of the discs. In conclusion, moderate mechanical stimulation restrained Cav1-mediated signaling pathway and exhibited anti-inflammatory effects on AFCs. Together with in vivo results, this study expounds the underlying molecular mechanisms on the effect of moderate mechanical stimulation on intervertebral discs (IVDs) and may provide a new therapeutic strategy for the treatment of IVD degeneration.

A Micropatterned Human-Specific Neuroepithelial Tissue for Modeling Gene and Drug-Induced Neurodevelopmental Defects

The generation of structurally standardized human pluripotent stem cell (hPSC)-derived neural embryonic tissues has the potential to model genetic and environmental mediators of early neurodevelopmental defects. Current neural patterning systems have so far focused on directing cell fate specification spatio-temporally but not morphogenetic processes. Here, the formation of a structurally reproducible and highly-organized neuroepithelium (NE) tissue is directed from hPSCs, which recapitulates morphogenetic cellular processes relevant to early neurulation. These include having a continuous, polarized epithelium and a distinct invagination-like folding, where primitive ectodermal cells undergo E-to-N-cadherin switching and apical constriction as they acquire a NE fate. This is accomplished by spatio-temporal patterning of the mesoendoderm, which guides the development and self-organization of the adjacent primitive ectoderm into the NE. It is uncovered that TGFβ signaling emanating from endodermal cells support tissue folding of the prospective NE. Evaluation of NE tissue structural dysmorphia, which is uniquely achievable in the model, enables the detection of apical constriction and cell adhesion dysfunctions in patient-derived hPSCs as well as differentiating between different classes of neural tube defect-inducing drugs.

Transcriptome analysis identifies the differentially expressed genes related to the stemness of limbal stem cells in mice

Limbal stem cells (LSCs) reside in the basal layer of limbal epithelial cells (LECs). They are crucial for maintenance of corneal epithelium homeostasis and corneal wound healing. Their stemness is determined by their gene expression pattern. Despite of several positive identifiers have been reported, the unique biomarker for LSCs still remain elusive. Differentially expressed genes (DEGs) between stem cells and differentiated cells affect the fate of stem cells via specific signaling pathway. In order to understand the DEGs in the LSCs, RNA-seq was firstly conducted using a mouse model. A total of 1907 up-regulated DEGs and 395 down-regulated DEGs were identified in the limbus (L) compared to central cornea (CC) and conjunctiva (Cj). Reliability of the expression of genes from RNA-seq analysis was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) and immunofluorescence staining. The expression pattern of putative biomarkers was considered to be age-related. In up-regulated DEGs GO analysis, 570 gene ontology (GO) terms were significantly enriched. Five groups of genes related with biological processes from these significantly enriched GO terms comprised ionic transport, regulation of tissue development, muscle contraction, visual perception, and cell adhesion, which were clustered as a weighted similar network. Whereas, in down-regulated DEGs GO analysis, 61 GO terms were significantly enriched and only one group of ATP biosynthesis and metabolic process were clustered. Furthermore, we identified 55 signaling pathways by the Kyoto Encyclopedia of Genes and Genomes (KEGG) database based on up-regulated genes and 14 KEGG pathways based on down-regulated genes. In this study, we provide a landscape of the expression of putative LSCs biomarkers and stemness-related signaling pathways in a mouse model. Our findings could aid in the identification of LSC niche factors that may be related to the stemness of the LSCs.

Suspension state regulates epithelial-to-mesenchymal transition and stemness of breast tumor cells

OBJECTIVES

The mechanical forces on circulating tumor cells (CTCs) should not be ignored in blood and it is more essential that CTCs can overcome and utilize the mechanical interaction to acquire the ability of distant metastasis. At present there are few studies on how suspension mechanics regulates the behavior of tumor cells. The aim of the study was to explore the effects of suspension state on the epithelial-mesenchymal transition (EMT) and stemness of breast CTCs and the molecular mechanisms involved.

RESULTS

Suspension state could regulate the program of EMT in breast cancer cells, which supported the complex dynamic concept of EMT. It is that the Ras homolog family member A (RhoA)/Rho-associated coiled-coil containing protein kinase 1 (ROCK1) signaling pathway was activated by suspension state in MCF-7 cells instead of MDA-MB-231 cells. In addition, suspension state increased the stemness of breast cancer cells from different aspects.

CONCLUSION

The study highlighted the emergence of hybrid epithelial/mesenchymal (E/M) state during hematogenous metastasis and the plasticity of CTCs caused by cancer stem cells, further providing novel insights into clinical monitoring of CTCs and therapeutic strategies.

Cell migration regulated by RGD nanospacing and enhanced under moderate cell adhesion on biomaterials

While nanoscale modification of a biomaterial surface is known to influence various cell behaviors, it is unclear whether there is an optimal nanospacing of a bioactive ligand with respect to cell migration. Herein, we investigated the effects of nanospacing of arginine-glycine-aspartate (RGD) peptide on cell migration and its relation to cell adhesion. To this end, we prepared RGD nanopatterns with varied nanospacings (31-125 nm) against the nonfouling background of poly(ethylene glycol), and employed human umbilical vein endothelial cells (HUVECs) to examine cell behaviors on the nanopatterned surfaces. While HUVECs adhered well on surfaces of RGD nanospacing less than 70 nm and exhibited a monotonic decrease of adhesion with the increase of RGD nanospacing, cell migration exhibited a nonmonotonic change with the ligand nanospacing: the maximum migration velocity was observed around 90 nm of nanospacing, and slow or very slow migration occurred in the cases of small or large RGD nanospacings. Therefore, moderate cell adhesion is beneficial for fast cell migration. Further molecular biology studies revealed that attenuated cell adhesion and activated dynamic actin rearrangement accounted for the promotion of cell migration, and the genes of small G proteins such as Cdc42 were upregulated correspondingly. The present study sheds new light on cell migration and its relation to cell adhesion, and paves a way for designing biomaterials for applications in regenerative medicine.

User-defined morphogen patterning for directing human cell fate stratification

Concentration gradients of biochemical stimuli such as morphogens play a critical role in directing cell fate patterning across species and throughout development but are not commonly recapitulated in vitro. While in vitro biomolecule gradients have been generated using customized microfluidic platforms, broad implementation has been limited because these platforms introduce new variables to cell culture such as externally driven flow, culture in a specialized matrix, or extended time for in situ long range diffusion. Here we introduce a method that enables preforming and then transferring user-controlled gradients to cells in standard "open" cultures. Our gradient patterning devices are modular and decoupled from the culture substrate. We find that gradient generation and transfer are predictable by finite element modeling and that device and loading parameters can be used to tune the stimulus pattern. Furthermore, we demonstrate use of these devices to spatially define morphogen signal gradients and direct peri-gastrulation fate stratification of human pluripotent stem cells. This method for extrinsic application of biochemical signal gradients can thus be used to spatially influence cellular fate decisions in a user-controlled manner.

Unchain My Heart: Integrins at the Basis of iPSC Cardiomyocyte Differentiation

The cellular response to the extracellular matrix (ECM) microenvironment mediated by integrin adhesion is of fundamental importance, in both developmental and pathological processes. In particular, mechanotransduction is of growing importance in groundbreaking cellular models such as induced pluripotent stem cells (iPSC), since this process may strongly influence cell fate and, thus, augment the precision of differentiation into specific cell types, e.g., cardiomyocytes. The decryption of the cellular machinery starting from ECM sensing to iPSC differentiation calls for new in vitro methods. Conveniently, engineered biomaterials activating controlled integrin-mediated responses through chemical, physical, and geometrical designs are key to resolving this issue and could foster clinical translation of optimized iPSC-based technology. This review introduces the main integrin-dependent mechanisms and signalling pathways involved in mechanotransduction. Special consideration is given to the integrin-iPSC linkage signalling chain in the cardiovascular field, focusing on biomaterial-based in vitro models to evaluate the relevance of this process in iPSC differentiation into cardiomyocytes.

Long-Term Perfusion Culture of Monoclonal Embryonic Stem Cells in 3D Hydrogel Beads for Continuous Optical Analysis of Differentiation

Developmental cell biology requires technologies in which the fate of single cells is followed over extended time periods, to monitor and understand the processes of self-renewal, differentiation, and reprogramming. A workflow is presented, in which single cells are encapsulated into droplets (Ø: 80 µm, volume: ≈270 pL) and the droplet compartment is later converted to a hydrogel bead. After on-chip de-emulsification by electrocoalescence, these 3D scaffolds are subsequently arrayed on a chip for long-term perfusion culture to facilitate continuous cell imaging over 68 h. Here, the response of murine embryonic stem cells to different growth media, 2i and N2B27, is studied, showing that the exit from pluripotency can be monitored by fluorescence time-lapse microscopy, by immunostaining and by reverse-transcription and quantitative PCR (RT-qPCR). The defined 3D environment emulates the natural context of cell growth (e.g., in tissue) and enables the study of cell development in various matrices. The large scale of cell cultivation (in 2000 beads in parallel) may reveal infrequent events that remain undetected in lower throughput or ensemble studies. This platform will help to gain qualitative and quantitative mechanistic insight into the role of external factors on cell behavior.

Bone physiology as inspiration for tissue regenerative therapies

The development, maintenance of healthy bone and regeneration of injured tissue in the human body comprise a set of intricate and finely coordinated processes. However, an analysis of current bone regeneration strategies shows that only a small fraction of well-reported bone biology aspects has been used as inspiration and transposed into the development of therapeutic products. Specific topics that include inter-scale bone structural organization, developmental aspects of bone morphogenesis, bone repair mechanisms, role of specific cells and heterotypic cell contact in the bone niche (including vascularization networks and immune system cells), cell-cell direct and soluble-mediated contact, extracellular matrix composition (with particular focus on the non-soluble fraction of proteins), as well as mechanical aspects of native bone will be the main reviewed topics. In this Review we suggest a systematic parallelization of (i) fundamental well-established biology of bone, (ii) updated and recent advances on the understanding of biological phenomena occurring in native and injured tissue, and (iii) critical discussion of how those individual aspects have been translated into tissue regeneration strategies using biomaterials and other tissue engineering approaches. We aim at presenting a perspective on unexplored aspects of bone physiology and how they could be translated into innovative regeneration-driven concepts.

The role of integrin β1 in the heterogeneity of human embryonic stem cells culture

The maintenance of the pluripotency of human embryonic stem (hES) cells requires special conditions for culturing. These conditions include specific growth factors containing media and extracellular matrix (ECM) or an appropriate substrate for adhesion. Interactions between the cells and ECM are mediated by integrins, which interact with the components of ECM in active conformation. This study focused on the characterisation of the role of integrin β1 in the adhesion, migration and differentiation of hES cells. Blocking integrin β1 abolished the adhesion of hES cells, decreasing their survival and pluripotency. This effect was in part rescued by the inhibition of RhoA signalling with Y-27632. The presence of Y-27632 increased the migration of hES cells and supported their differentiation into embryoid bodies. The differences in integrin β1 recycling in the phosphorylation of the myosin light chain and in the localisation of TSC2 were observed between the hES cells growing as a single-cell culture and in a colony. The hES cells at the centre and borders of the colony were found to have differences in their morphology, migration and signalling network activity. We concluded that the availability of integrin β1 was essential for the contraction, migration and differentiation ability of hES cells.

Summary: The interaction between integrin β1 and the extracellular matrix differs at the centre of the colony and at the periphery, and is crucial for the survival of embryonic stem cells.

The distinct role of strand-specific miR-514b-3p and miR-514b-5p in colorectal cancer metastasis

The abnormal expression of microRNAs (miRNAs) in colorectal cancer (CRC) progression has been widely investigated. It was reported that the same hairpin RNA structure could generate mature products from each strand, termed 5p and 3p, which binds different target mRNAs. Here, we explored the expression, functions, and mechanisms of miR-514b-3p and miR-514b-5p in CRC cells and tissues. We found that miR-514b-3p was significantly down-regulated in CRC samples, and the ratio of miR-514b-3p/miR-514b-5p increased from advanced CRC, early CRC to matched normal colorectal tissues. Follow-up functional experiments illustrated that miR-514b-3p and miR-514b-5p had distinct effects through interacting with different target genes: MiR-514b-3p reduced CRC cell migration, invasion and drug resistance through increasing epithelial marker and decreasing mesenchymal marker expressions, conversely, miR-514b-5p exerted its pro-metastatic properties in CRC by promoting EMT progression. MiR-514b-3p overexpressing CRC cells developed tumors more slowly in mice compared with control cells, however, miR-514b-5p accelerated tumor metastasis. Overall, our data indicated that though miR-514b-3p and miR-514b-5p were transcribed from the same RNA hairpin, each microRNA has distinct effect on CRC metastasis.

Synthesis, characterization, antibacterial activity in dark and in vitro cytocompatibility of Ag-incorporated TiO2 microspheres with high specific surface area

Postoperative infection associated with medical implants is a devastating complication of orthopedic surgery. Considering the difficulties for the diagnosis and treatment of infection, coating the implant material with antibacterial substances is a promising protocol by which to avoid such an adverse reaction. Nanoparticles (NPs) constructed of anatase microspheres, one form of titanium dioxide (TiO₂), with a high specific surface area are fabricated in this study in a facile one-step process using homogeneous precipitation at 90 °C under atmospheric pressure using titanium sulfate (Ti[SO₄]₂) and urea as the titanium source and precipitant, respectively. The molar ratio of silver (Ag) to TiO₂ can be changed by varying the amount of silver nitrate (AgNO₃). The high specific surface area of the TiO₂ microspheres combined with Ag particles (Ag/TiO₂) exhibit excellent antibacterial properties against both Staphylococcus aureus and Escherichia coli. In addition, the Ag/TiO₂ material in this work possesses satisfactory biological performance on MC3T3-E1 cells. The high specific surface area of Ag/TiO₂ together with good antibacterial properties and cytocompatibility provide promising applications in dentistry, orthopedics, and other fields of medicine that use biomedical devices.

Substrate stiffness modulates the multipotency of human neural crest derived ectomesenchymal stem cells via CD44 mediated PDGFR signaling

Mesenchymal stem cells (MSCs) have been isolated from various mesodermal and ectodermal tissues. While the phenotypic and functional heterogeneity of MSCs stemming from their developmental origins has been acknowledged, the genetic and environmental factors underpinning these differences are not well-understood. Here, we investigated whether substrate stiffness mediated mechanical cues can directly modulate the development of ectodermal MSCs (eMSCs) from a precursor human neural crest stem cell (NCSC) population. We showed that NCSC-derived eMSCs were transcriptionally and functionally distinct from mesodermal bone marrow MSCs. eMSCs derived on lower substrate stiffness specifically increased their expression of the MSC marker, CD44 in a Rho-ROCK signaling dependent manner, which resulted in a concomitant increase in the eMSCs' adipogenic and chondrogenic differentiation potential. This mechanically-induced effect can only be maintained for short-term upon switching back to a stiff substrate but can be sustained for longer-term when the eMSCs were exclusively maintained on soft substrates. We also discovered that CD44 expression modulated eMSC self-renewal and multipotency via the downregulation of downstream platelet-derived growth factor receptor beta (PDGFRβ) signaling. This is the first instance demonstrating that substrate stiffness not only influences the differentiation trajectories of MSCs but also their derivation from upstream progenitors, such as NCSCs.

Recombinant spider silk-based bioinks

Bioinks, 3D cell culture systems which can be printed, are still in the early development stages. Currently, extensive research is going into designing printers to be more accommodating to bioinks, designing scaffolds with stiff materials as support structures for the often soft bioinks, and modifying the bioinks themselves. Recombinant spider silk proteins, a potential biomaterial component for bioinks, have high biocompatibility, can be processed into several morphologies and can be modified with cell adhesion motifs to enhance their bioactivity. In this work, thermally gelled hydrogels made from recombinant spider silk protein encapsulating mouse fibroblast cell line BALB/3T3 were prepared and characterized. The bioinks were evaluated for performance in vitro both before and after printing, and it was observed that unprinted bioinks provided a good platform for cell spreading and proliferation, while proliferation in printed scaffolds was prohibited. To improve the properties of the printed hydrogels, gelatin was given as an additive and thereby served indirectly as a plasticizer, improving the resolution of printed strands. Taken together, recombinant spider silk proteins and hydrogels made thereof show good potential as a bioink, warranting further development.

A Simple and Robust Method for Culturing Human-Induced Pluripotent Stem Cells in an Undifferentiated State Using Botulinum Hemagglutinin

Clinical and industrial applications of human-induced pluripotent stem cells (hiPSCs) is hindered by the lack of robust culture strategies capable of sustaining a culture in an undifferentiated state. Here, a simple and robust hiPSC-culture-propagation strategy incorporating botulinum hemagglutinin (HA)-mediated selective removal of cells deviating from an undifferentiated state is developed. After HA treatment, cell-cell adhesion is disrupted, and deviated cells detached from the central region of the colony to subsequently form tight monolayer colonies following prolonged incubation. The authors find that the temporal and dose-dependent activity of HA regulated deviated-cell removal and recoverability after disruption of cell-cell adhesion in hiPSC colonies. The effects of HA are confirmed under all culture conditions examined, regardless of hiPSC line and feeder-dependent or -free culture conditions. After routine application of our HA-treatment paradigm for serial passages, hiPSCs maintains expression of pluripotent markers and readily forms embryoid bodies expressing markers for all three germ-cell layers. This method enables highly efficient culturing of hiPSCs and use of entire undifferentiated portions without having to pick deviated cells manually. This simple and readily reproducible culture strategy is a potentially useful tool for improving the robust and scalable maintenance of undifferentiated hiPSC cultures.

In Vitro Micropatterned Human Pluripotent Stem Cell Test (µP-hPST) for Morphometric-Based Teratogen Screening

Exposure to teratogenic chemicals during pregnancy may cause severe birth defects. Due to high inter-species variation of drug responses as well as financial and ethical burdens, despite the widely use of in vivo animal tests, it’s crucial to develop highly predictive human pluripotent stem cell (hPSC)-based in vitro assays to identify potential teratogens. Previously we have shown that the morphological disruption of mesoendoderm patterns formed by geometrically-confined cell differentiation and migration using hPSCs could potentially serve as a sensitive morphological marker in teratogen detection. Here, a micropatterned human pluripotent stem cell test (µP-hPST) assay was developed using 30 pharmaceutical compounds. A simplified morphometric readout was developed to quantify the mesoendoderm pattern changes and a two-step classification rule was generated to identify teratogens. The optimized µP-hPST could classify the 30 compounds with 97% accuracy, 100% specificity and 93% sensitivity. Compared with metabolic biomarker-based hPSC assay by Stemina, the µP-hPST could successfully identify misclassified drugs Bosentan, Diphenylhydantoin and Lovastatin, and show a higher accuracy and sensitivity. This scalable µP-hPST may serve as either an independent assay or a complement assay for existing assays to reduce animal use, accelerate early discovery-phase drug screening and help general chemical screening of human teratogens.

Substrate stiffness orchestrates epithelial cellular heterogeneity with controlled proliferative pattern via E-cadherin/β-catenin mechanotransduction

Epithelial cellular heterogeneity has been observed in pathological tissues with abnormal matrix stiffness and cells cultured on rigid substrates. However, it remains unclear how matrix stiffness influences cellular heterogeneity formation in multi-cellular population. Here, we demonstrated that cellular heterogeneity regulated by substrate stiffness is evident starting from the initial single-cell stage (indicated by cellular Young's modulus and morphology) until the resulting multi-cellular stage (indicated by cellular functions) through distinguished proliferative patterns. Epithelial cells on soft substrate proliferated in a neighbor-dependent manner with stronger E-cadherin expression and more homogeneous E-cadherin/β-catenin localization compared to those on coverslips, which resulted in reduced heterogeneity in downstream cellular functions of the multi-cellular population. In particular, decreased heterogeneity in human embryonic stem cells upon expansion and endodermal induction was achieved on soft substrate. Overall, our work provides new insights on mechanotransduction during epithelial proliferation which regulates the formation of cellular heterogeneity and potentially provides a highly efficient approach to regulate stem cell fate by fine-tuning substrate stiffness.

STATEMENT OF SIGNIFICANCE

This study demonstrates that cellular heterogeneity regulated by substrate stiffness is evident starting from the initial single-cell stage until the resulting multi-cellular stage through distinguished proliferative patterns. During this process, E-cadherin/β-catenin mechanotransduction is found to play important role in substrate stiffness-regulated epithelial cellular heterogeneity formation. In particular, decreased heterogeneity in human embryonic stem cells upon expansion and endodermal induction is achieved on soft substrate. Hence, we believe that this work not only provides new insights on mechanotransduction of E-cadherin/β-catenin which regulates the formation of cellular heterogeneity during proliferation, but also potentially provides a highly efficient approach to regulate stem cell fate by fine-tuning substrate stiffness.

Stencil Micropatterning of Human Pluripotent Stem Cells for Probing Spatial Organization of Differentiation Fates

Human pluripotent stem cells (hPSCs), including embryonic stem cells and induced pluripotent stem cells, have the intrinsic ability to differentiate into all three germ layers. This makes them an attractive cell source for regenerative medicine and experimental modeling of normal and diseased organogenesis. However, the differentiation of hPSCs in vitro is heterogeneous and spatially disordered. Cell micropatterning technologies potentially offer the means to spatially control stem cell microenvironments and organize the resultant differentiation fates. Micropatterning hPSCs needs to take into account the stringent requirements for hPSC survival and maintenance. Here, we describe stencil micropatterning as a method that is highly compatible with hPSCs. hPSC micropatterns are specified by the geometries of the cell stencil through-holes, which physically confine the locations where hPSCs can access and attach to the underlying extracellular matrix-coated substrate. Due to this mode of operation, there is greater flexibility to use substrates that can adequately support hPSCs as compared to other cell micropatterning methods. We also highlight critical steps for the successful generation of hPSC micropatterns. As an example, we demonstrate that stencil micropatterning of hPSCs can be used to modulate spatial polarization of cell-cell and cell-matrix adhesions, which in turn determines mesoendoderm differentiation patterns. This simple and robust method to micropattern hPSCs widens the prospects of establishing experimental models to investigate tissue organization and patterning during early embryonic development.

The mechanical regulation of integrin-cadherin crosstalk organizes cells, signaling and forces

Cadherins and integrins are intrinsically linked through the actin cytoskeleton and share common signaling molecules. Although mechanosensing by the integrin-actin axis has long been appreciated, a growing body of literature now demonstrates that cadherins also transduce and respond to mechanical forces. Mounting evidence shows that mechanically driven crosstalk between integrins and cadherins regulates the spatial distribution of these receptors, their signaling intermediates, the actin cytoskeleton and intracellular forces. This interplay between integrins and cadherins can control fibronectin matrix assembly and signaling, and a fine balance between traction forces at focal adhesions and intercellular tension at adherens junctions is crucial for directional collective cell migration. In this Commentary, we discuss two central ideas: (1) how the dynamic interplay between integrins and cadherins regulates the spatial organization of intracellular signals and the extracellular matrix, and (2) the emerging consensus that intracellular force is a central mechanism that dictates cell behavior, guides tissue development and ultimately drives physiology.

Stencil Micropatterning for Spatial Control of Human Pluripotent Stem Cell Fate Heterogeneity

Human pluripotent stem cells (hPSCs) have the intrinsic ability to differentiate and self-organize into distinct tissue patterns, although this requires the presentation of spatial environmental cues, i.e., biochemical and mechanical gradients. Cell micropatterning technologies potentially offer the means to spatially control stem cell microenvironments and organize the resultant differentiation fates. Here, we describe stencil micropatterning as a simple and robust method to generate hPSC micropatterns for controlling hPSC differentiation patterns. hPSC micropatterns are specified by the geometries of the cell stencil through-holes, which physically confine the locations where the underlying extracellular matrix and hPSCs can access and attach to the substrate. This confers the unique capability of stencil micropatterning to work with a variety of culture substrates and extracellular matrices for optimal hPSC culture. We present the detailed steps of stencil micropatterning to successfully generate hPSC micropatterns, which can be used to investigate how spatial polarization of cell adhesion results in cell fate heterogeneity.

Topological control of nitric oxide secretion by tantalum oxide nanodot arrays

BACKGROUND

Nitric oxide (NO) plays a very important role in the cardiovascular system as a major secondary messenger in signaling pathway. Its concentration regulates most of the important physiological indexes including the systemic blood pressure, blood flow, regional vascular tone and other cardiac functions. The effect of nanotopography on the NO secretion in cardiomyocytes has not been elucidated before. In this study, we report how the nanotopography can modulate the secretion profile of NO and attempt to elucidate the genetic pathways responsible for the same by using Tantalum Oxide nanodot arrays ranging from 10 to 200 nm. A series of nanodot arrays were fabricated with dot diameter ranging from 10 to 200 nm. Temporal NO release of cardiomyocytes was quantified when grown on different surfaces. Quantitative RT-PCR and Western blot were performed to verify the genetic pathways of NO release.

RESULTS

After hours 24 of cell seeding, NO release was slowly enhanced by the increase of dot diameter from 10 nm up to 50 nm, mildly enhanced to a medium level at 100 nm, and increase rapidly to a high level at 200 nm. The temporal enhancement of NO release dropped dramatically on day 3. On day 5, a topology-dependent profile was established that maximized at 50 nm and dropped to control level at 200 nm. The NO releasing profile was closely associated with the expression patterns of genes associated with Endothelial nitric oxide synthase (eNOS) pathway [GPCR, PI3K, Akt, Bad, Bcl-2, NFκB(p65), eNOS], but less associated with Inducible nitric oxide synthase (iNOS) pathway (TNF-α, ILK, Akt, IκBα, NFκB, iNOS). Western blotting of Akt, eNOS, iNOS, and NFκB further validated that eNOS pathway was modulated by nanotopology.

CONCLUSIONS

Based on the findings of the present study, 50, 100 nm can serve as the suitable nanotopography patterns for cardiac implant surface design. These two nanodot arrays promote NO secretion and can also promote the vascular smooth muscle relaxation. The results of this study can improve the heart stent design in the medical treatments.

Cell Adhesion Molecules and Stem Cell-Niche-Interactions in the Limbal Stem Cell Niche

Interactions between stem cells and their microenvironment are critical for regulation and maintenance of stem cell function. To elucidate the molecular interactions within the human limbal epithelial stem/progenitor cell (LEPC) niche, which is essential for maintaining corneal transparency and vision, we performed a comprehensive expression analysis of cell adhesion molecules (CAMs) using custom-made quantitative real-time polymerase chain reaction (qRT-PCR) arrays and laser capture-microdissected LEPC clusters, comprising LEPCs, melanocytes, mesenchymal cells, and transmigrating immune cells. We show that LEPCs are anchored to their supporting basement membrane by the laminin receptors α3β1 and α6β4 integrin and the dystroglycan complex, while intercellular contacts between LEPCs and melanocytes are mediated by N-, P-, and E-cadherin together with L1-CAM, a member of the immunoglobulin superfamily (Ig)CAMs. In addition to the LEPC-associated heparan sulfate proteoglycans syndecan-2, glypican-3, and glypican-4, the IgCAM members ICAM-1 and VCAM-1 were found to be variably expressed on LEPCs and associated niche cells and to be dynamically regulated in response to chemokines such as interferon-γ to enhance interactions with immune cells. Moreover, junctional adhesion molecule JAM-C accumulating in the subepithelial limbal matrix, appeared to be involved in recruitment of immune cells, while mesenchymal stromal cells appeared to use the nephronectin receptor integrin α8 for approaching the limbal basement membrane. In summary, we identified a novel combination of cell surface receptors that may regulate both stable and dynamic cell-matrix and cell-cell interactions within the limbal niche. The findings provide a solid foundation for further functional studies and for advancement of our current therapeutic strategies for ocular surface reconstruction.

A method for human teratogen detection by geometrically confined cell differentiation and migration

Unintended exposure to teratogenic compounds can lead to various birth defects; however current animal-based testing is limited by time, cost and high inter-species variability. Here, we developed a human-relevant in vitro model, which recapitulated two cellular events characteristic of embryogenesis, to identify potentially teratogenic compounds. We spatially directed mesoendoderm differentiation, epithelial-mesenchymal transition and the ensuing cell migration in micropatterned human pluripotent stem cell (hPSC) colonies to collectively form an annular mesoendoderm pattern. Teratogens could disrupt the two cellular processes to alter the morphology of the mesoendoderm pattern. Image processing and statistical algorithms were developed to quantify and classify the compounds' teratogenic potential. We not only could measure dose-dependent effects but also correctly classify species-specific drug (Thalidomide) and false negative drug (D-penicillamine) in the conventional mouse embryonic stem cell test. This model offers a scalable screening platform to mitigate the risks of teratogen exposures in human.