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Anatomically and biologically relevant vascular models are critical to progress our understanding of cardiovascular diseases (CVDs) that can lead to effective therapies. Despite advances in 3D bioprinting, recapitulating complex architectures (i.e., freestanding, branching, multilayered, perfusable) of a cell-laden vascular construct remains technically challenging, and the development of new techniques that can recapitulate both anatomical and biological features of blood vessels is of paramount importance. In this work, we introduce a unique, microfluidics-enabled molding technique that allows us to fabricate anatomically-relevant, cell-laden hydrogel vascular models. Our approach employed 3D-printed porous molds of poly(ethylene glycol) diacrylate (PEGDA) as templates to cast alginate-containing bioinks. Due to the porous and aqueous nature of the PEGDA mold, the calcium ion (Ca2+) was diffusively released to crosslink the bioinks to create hollow structures. Applying this technique, multiscale, multilayered vascular constructs that were freestanding and perfusable were readily fabricated using cell-compatible bioinks (i.e., alginate and gelatin methacryloyl (GelMA)). The bioinks were also readily customizable to either improve the compatibility with specific vascular cells or tune the mechanical modulus to mimic native blood vessels. Importantly, we successfully integrated smooth muscle cells and endothelial cells in a biomimetic organization within our vessel constructs and demonstrated a significant increase in monocyte adhesion upon stimulation with an inflammatory cytokine, tumor necrosis factor-alpha (TNF-α). We also demonstrated that the fabricated vessels were amenable for testing percutaneous coronary interventions (i.e., drug-eluting balloons and stents) under physiologically-relevant mechanical states, such as vessel stretching and bending. Overall, we introduce a versatile fabrication technique with multi-faceted possibilities of generating biomimetic vascular models that can benefit future research in mechanistic understanding of CVD progression and the development of therapeutic interventions.

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., This paper reports the generation of a reproducible and highly organized neuroepithelial (NE) tissue by combining human pluripotent stem cell (hPSC) micropatterning and a temporally sequenced induction protocol to specify NE cells in spatial juxtaposition to mesoendoderm cells. By evaluating NE tissue structural dysmorphia in the micropatterned NE model, we can successfully model gene‐ and drug‐induced neurodevelopmental defects.

Translin-associated protein X (TRAX) is a scaffold protein with various functions and has been associated with mental illnesses, including schizophrenia. We have previously demonstrated that TRAX interacts with a Gsα protein-coupled receptor, the A2A adenosine receptor (A2AR), and mediates the function of this receptor in neuritogenesis. In addition, stimulation of the A2AR markedly ameliorates DNA damage evoked by elevated oxidative stress in neurons derived from induced pluripotent stem cells (iPSCs). Here, we report that glycogen synthase kinase 3 beta (GSK3β) and disrupted-in-schizophrenia 1 (DISC1) are two novel interacting proteins of TRAX. We present evidence to suggest that the stimulation of A2AR markedly facilitated DNA repair through the TRAX/DISC1/GSK3β complex in a rat neuronal cell line (PC12), primary mouse neurons, and human medium spiny neurons derived from iPSCs. A2AR stimulation led to the inhibition of GSK3β, thus dissociating the TRAX/DISC1/GSK3β complex and facilitating the non-homologous end-joining pathway (NHEJ) by enhancing the activation of a DNA-dependent protein kinase via phosphorylation at Thr2609. Similarly, pharmacological inhibition of GSK3β by SB216763 also facilitated the TRAX-mediated repair of oxidative DNA damage. Collectively, GSK3β binds with TRAX and negatively affects its ability to facilitate NHEJ repair. The suppression of GSK3β by A2AR activation or a GSK3β inhibitor releases TRAX for the repair of oxidative DNA damage. Our findings shed new light on the molecular mechanisms underlying diseases associated with DNA damage and provides a novel target (i.e., the TRAX/DISC1/GSK3β complex) for future therapeutic development for mental disorders.

In article number 2001100, Yi‐Chin Toh and co‐workers combine hPSC micropatterning and a temporally‐sequenced induction protocol to specify neuroepithelial (NE) cells in spatial juxtaposition to mesoendoderm cells. This results in the formation of a reproducible and highly‐organized NE tissue. By evaluating NE tissue structural dysmorphia in the micropatterned NE model, gene‐ and drug‐induced neurodevelopmental defects can be successfully modelled. [Image: see text]

The ability to mimic and control neuroectoderm (NE) development in vitro has important applications in modeling neurodevelopmental diseases and modulating efficiency and uniformity of brain organoid generation. Current human neural differentiation model-systems can dictate NE cell fate specification but not their morphogenesis. We report a first instance of directing the formation of a structurally reproducible and highly-organized NE tissue from human pluripotent stem cells (hPSCs) that recapitulates architectural and cellular characteristics of early neural tube morphogenesis. These include having a continuous, polarized epithelium and a distinct invagination-like folding, where the NE cells undergo E-to-N-cadherin switching and apical constriction. This is accomplished by spatiotemporal patterning of the mesoendoderm (ME) that guides self-organization of the adjacent NE. We uncover that TGF signaling emanating from endodermal cells is obligatory in NE tissue folding. Notably, evaluation of NE structural dysmorphia, which is uniquely achievable in our model, allows for early detection and quantitative measurement of pathologies mediated by FMR1 silencing in Fragile X Syndrome. Altogether, such unprecedented degree of control over the NE tissue architecture greatly expands the potential applications of human stem cell-modeling for early neural tissue development and pathologies.

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.

The kidney is one of the major target organs for drug-induced toxicity. The renal proximal tubule is frequently affected due to its roles in drug transport and in concentrating the glomerular filtrate. Drug-induced kidney injury is associated with increased morbidity and mortality of patients. During drug development, nephrotoxicity is typically detected only late, which leads to high costs for the pharmaceutical industry. A central problem is the lack of pre-clinical models with high predictability. Regulatory accepted or validated in vitro models for the prediction of nephrotoxicity are not available. We developed a novel in vitro model for the prediction of renal proximal tubular toxicity in humans. It employs human primary renal proximal tubular cells and the expression levels of interleukin (IL)-6 and IL-8 were used as the endpoint. The model was evaluated with 41 well-characterized drugs and chemicals. The median values of the major performance metrics (balanced accuracy, sensitivity, specificity, positive predictive value, negative predictive value and area under the curve of the receiver operating characteristic curve) ranged between 0.76 and 0.85. This revealed that the predictability of the model is high and it would be expected that in ∼76%–85% of the cases where compounds were predicted as positives or negatives the predictions would be correct. Altogether, the data suggest that the model would allow the prediction of drug-induced proximal tubular toxicity at early pre-clinical stages during drug development. Future work will aim at further validating this model and adapting it to recently developed renal proximal tubular-like cells derived from human pluripotent stem cells.