Advanced Healthcare Materials

The inherent characteristics of glioblastoma (GBM), including tumoral heterogeneity and invasive capacity, combined with the presence of the blood-brain tumor barrier (BBTB), present challenges in developing effective treatment for GBM. Especially, the margins of GBM, where GBM cells infiltrate normal brain tissue, exhibit high resistance to therapies. Despite the difficulties in controlling tumor progression from this region, the GBM margin remains a critical area to be studied. Here we report a microengineered model that mimics the BBTB within the GBM margin, incorporating a 3D network of normal astrocytes and GBM cells isolated from patients newly diagnosed with GBM. The interaction between GBM cells and stromal cells results in increased vascular permeability, reactive gliosis, and alterations in astrocyte behavior to foster tumor invasiveness and progression. We compare patient-specific tumor responses to conventional chemotherapy in our BBTB on a chip model with clinical outcomes, demonstrating the capability of the model to predict personalized drug responses. Our BBTB model may serve as a personalized tool to examine the interactions between tumors and normal brain tissue, ultimately facilitating the screening of personalized medicine for GBM treatment.

Human mesenchymal stem cells (hMSCs) are widely represented in ongoing regenerative medicine clinical trials due to their ease of autologous implantation. In bone regeneration, crosstalk between macrophages and hMSCs is critical with macrophages playing a key role in the recruitment and differentiation of hMSCs. However, engineered biomaterials able to both direct hMSC fate and modulate macrophage phenotype have not yet been identified. A novel combinatorial chemistry-microtopography screening platform, the ChemoTopoChip, is used to identify materials suitable for bone regeneration by screening with human immortalized mesenchymal stem cells (hiMSCs) and human macrophages. The osteoinduction achieved in hiMSCs cultured on the "hit" materials in basal media is comparable to that seen when cells are cultured in osteogenic media, illustrating that these materials offer a materials-induced alternative in bone-regenerative applications. These also exhibit immunomodulatory effects, concurrently polarizing macrophages towards a pro-healing phenotype. Control of cell response is achieved when both chemistry and topography are recruited to instruct the required cell phenotype, combining synergistically. The large library of materials reveals that the relative roles of microtopography and material chemistry are similar, and machine learning identifies key material and topographical features for cell-instruction.

Glycosylation regulates immune and neural functions within the central nervous system (CNS), yet biomaterials rarely leverage glycans due to their structural complexity. Polysialic acid (PSA), comprising 2,8-linked sialic acid residues, is a promising candidate owing to its potent immunomodulatory interactions with inhibitory Siglec receptors. Systematic screening of multiple sialic acid derivatives identifies PSA as uniquely effective in inducing anti-inflammatory polarization of bone marrow-derived macrophages (BMDMs). Based on these findings, an injectable microporous annealed particle (MAP) scaffold presenting PSA covalently via its reducing end (MAP-PSA) is engineered, recapitulating physiological glycan orientation. MAP-PSA exhibits robust mechanical properties, stable glycan immobilization, and resistance to enzymatic degradation. Using ischemic stroke as a CNS injury model, MAP-PSA significantly reduces neutrophil infiltration and inflammatory activation while enhancing reparative macrophage and microglial phenotypes. These immunomodulatory effects persist into subacute stages, characterized by sustained reductions in inflammation and enhanced microglial homeostasis. Overall, MAP-PSA scaffolds demonstrate a novel therapeutic paradigm for CNS injuries such as stroke, with translational potential for broader neuroinflammatory and regenerative applications.

Demyelinating diseases are a group of complex neurodegenerative disorders characterized by damage to the myelin, the protective sheath that insulates and supports efficient nerve signal conduction. Such a loss of myelin causes the formation of lesions not only in the brain but also often in the spinal cord (SC). Despite the high prevalence of SC lesions among patients, existing models mostly focus on those in the brain, inadequately capture the unique anatomical and physiological features of SC pathology. In this study, we developed a robust, reproducible in vitro model of SC demyelination by combining microwell technology and piezoelectric scaffolds to engineer human neural stem cell (hNSC)-derived nerve tissues featuring aligned, myelinated, extended axons up to 2000 {micro}m in length. We utilized distinct chemical treatments to induce demyelination with or without axonal degeneration: a cuprizone cocktail, a copper chelator combined with inflammatory cytokines, and lysophosphatidylcholine (LPC). Electrophysiological assessments validated the physiological relevance of our model, demonstrating impaired signal transmission and neural connectivity akin to in vivo demyelination pathology. Our versatile platform thus provides a valuable tool for elucidating SC demyelination pathophysiology and exploring potential therapeutic interventions.

Glioblastoma (GBM) tumor cells are found in the perivascular niche microenvironment and are believed to associate closely with the brain microvasculature. However, it is largely unknown how the resident cells of the perivascular niche, such as endothelial cells, pericytes, and astrocytes, influence GBM tumor cell behavior and disease progression. We describe a three-dimensional in vitro model of the brain perivascular niche developed by encapsulating brain-derived endothelial cells, pericytes, and astrocytes in a gelatin hydrogel. We show that pericytes and astrocytes explicitly contribute to vascular architecture and maturation. We use co-cultures of patient-derived GBM tumor cells with brain microvascular cells to identify a role for pericytes and astrocytes in establishing a perivascular niche environment that modulates GBM cell invasion, proliferation, and therapeutic response. Engineered models provides unique insight regarding the spatial patterning of GBM cell phenotypes in response to a multicellular model of the perivascular niche. Critically, we show that engineered perivascular models provide an important resource to evaluate mechanisms by which inter- cellular interactions modulate GBM tumor cell behavior, drug response, and provide a framework to consider patient-specific disease phenotypes.

Building brain foundation models to capture the underpinning neural dynamics of human behavior requires large functional neural datasets for training, which current implantable Brain-Computer Interfaces (iBCIs) cannot obtain due to the instability of rigid materials in the brain. How can we achieve high-density neural recordings with wide brain region access at single-neuron resolution, while maintaining long-term stability? In this study, we present a novel approach to overcome these trade-offs by introducing Fleuron, a family of ultrasoft, ultra-low-k dielectric materials compatible with thin-film scalable microfabrication techniques. We successfully integrate up to 1,024 channels within a single minimally invasive Fleuron depth electrode. The combination of the novel implant material and geometry enables single-unit level recordings for 18 months in rodent models, and achieves a large number of units detected per electrode across animals. 128-channel Fleuron probes, that cover 8x larger tissue volume than state-of-the-art polyimide counterparts, can track over 100 single-units over months. Stability in neural recordings correlates with reduced glial encapsulation compared to polyimide controls up to 9-month post-implantation. Fleuron probes are integrated with a low-power, mixed-signal ASIC to achieve over 1,000 channels electronic interfaces and can be safely implanted in depth using minimally invasive surgical techniques via a burr hole approach without requiring specialized robotics. Fleuron probes further create a unique contrast in clinical 3T MRI, allowing for post-operative position confirmation. Large-animal and ex vivo human tissue studies confirm safety and functionality in larger brains. Finally, Fleuron probes are used for the first time ever intraoperatively during planned resection surgeries, confirming in-human usability, and demonstrating the potential of the technology for clinical translation in iBCIs.

Neurological disorders are a major cause of death and disability worldwide. The brain's energy metabolism is essential to its proper function, yet the mechanisms driving neuroenergetic dysfunction remain poorly understood. A key challenge is the limited availability of human-relevant models that can reproduce the complexity of brain physiology. An Organ-on-Chip (OoC) system was developed to mimic the neurovascular unit metabolic coupling by incorporating human isogenic iPSC-derived endothelial-like cells, pericyte-like cells, astrocytes, and a cerebral organoid, representing the main cellular components of the NVU. The novel, customized microfluidic platform enables research on neurovascular coupling by interconnecting a blood-brain barrier-on-a-chip model with a 3D brain parenchymal compartment to mimic physiological conditions.

Ovarian tissue cryopreservation and autotransplantation (OTCT) is a crucial fertility preservation strategy for patients facing gonadotoxic cancer treatments, but its clinical success is hampered by ischemic injury and follicle loss following transplantation. This study aimed to enhance OTCT outcomes by employing microporous annealed particle (MAP) hydrogels to promote human ovarian graft revascularization. Unlike non-encapsulated tissue grafts, which exhibited early but transient and disorganized host vascular infiltration followed by regression, tissue grafts encapsulated in MAP hydrogels (OvaMAPs) demonstrated delayed yet organized and stable, long-term revascularization. OvaMAPs had significantly greater mouse CD31+ tissue area and vessel length after 3 and 6 weeks post-transplantation in ovariectomized immunodeficient mice compared to non-encapsulated grafts. By 20 weeks, both groups restored physiological estradiol levels (with OvaMAPs reaching 158 pg/mL) and suppressed follicle-stimulating hormone, confirming integration of the grafts with the hosts hypothalamic-pituitary axes. Notably, OvaMAPs achieved comparable endocrine function restoration with reduced estradiol variability, indicating more consistent graft function. In conclusion, MAP hydrogel encapsulation promoted long-term graft revascularization and vascular stability after OTCT, ultimately supporting consistent endocrine integration with host physiology.

Chondral and osteochondral repair strategies are limited by adverse bony changes that occur after injury. Bone resorption can cause entire scaffolds, engineered tissues, or even endogenous repair tissues to subside below the cartilage surface. To address this translational issue, we fabricated poly(D,L-lactide-co-glycolide) (PLGA) microcapsules containing the pro-osteogenic agents triiodothyronine and {beta}-glycerophosphate, and delivered these microcapsules in a large animal model of osteochondral injury to preserve bone structure. We demonstrate that developed microcapsules ruptured in vitro under increasing mechanical loads, and readily sink within a liquid solution, allowing for gravity-based positioning onto the osteochondral surface. In a large animal, these mechano-active microcapsules (MAMCs) were assessed through two different delivery strategies. Intra-articular injection of control MAMCs enabled fluorescent quantification of MAMC rupture and cargo release in a synovial joint setting over time in vivo. This joint-wide injection also confirmed that the MAMCs do not elicit an inflammatory response. In the contralateral hindlimbs, chondral defects were created, MAMCs were locally administered, and nanofracture (Nfx), a clinically utilized method to promote cartilage repair, was performed. The NFx holes enabled marrow-derived stromal cells to enter the defect area and served as repeatable bone injury sites to monitor over time. Animals were evaluated 1 and 2 weeks after injection and surgery. Analysis of injected MAMCs showed that bioactive cargo was released in a controlled fashion over 2 weeks. A bone fluorochrome label injected at the time of surgery displayed maintenance of mineral labeling in the therapeutic group, but resorption in both control groups. Alkaline phosphatase (AP) staining at the osteochondral interface revealed higher AP activity in defects treated with therapeutic MAMCs. Overall, this study establishes a new micro-fluidically generated delivery platform that releases therapeutic factors in an articulating joint, and reduces this to practice in the delivery of therapeutics that preserve bone structure after osteochondral injury.

In tissues where the vasculature is either lacking or abnormal, biomaterials can be designed to promote vessel formation and enhance tissue repair. In this work, we independently tune the microstructure and bioactivity of microporous annealed particle (MAP) scaffolds to guide cell patterning in 3D and promote de novo assembly of endothelial progenitor-like cells into vessels. We implement both in silico characterization and in vitro experimentation to elucidate an optimal scaffold formulation for vessel formation. We determine that MAP scaffolds with pore volumes on the same order of magnitude as cells facilitate cell growth and vacuole formation. We achieve spatial control over cell spreading by incorporating adhesive microgels in well-mixed, heterogeneous MAP scaffolds. While we demonstrate that integrin engagement is the primary driver of network formation in these materials, introducing adhesive microgels loaded with heparin nanoparticles leads to the formation of vascular tubes after 3 days in culture. We then show in vivo that this unique scaffold formulation enhances vessel maturation in a wound healing model and instructs differential vascular patterning in the tumor microenvironment. Taken together, this work determines the optimal microstructure and ligand presentation within MAP scaffolds that lead to vascular constructs in vitro and facilitate neovascularization in vivo.

Rapid revascularization is critical to tissue graft survival, as delayed reperfusion drives tissue ischemia and compromises cell viability and graft function. Although bulk hydrogels have been explored for promoting vessel formation, vascularization remains too slow to prevent ischemic injury to grafted tissues, highlighting the need for biomaterial platforms that accelerate graft revascularization and reperfusion. In this study, we present granular hydrogel composites (GHCs), where interstitial space is filled with fibrin and collagen to provide a vasculogenic matrix environment. GHCs supported the assembly of embedded endothelial cells into interconnected, lumenized networks in vitro which anastomosed with host vasculature and were systemically perfused 7 days after implantation. Careful optimization studies revealed that GHCs formed from covalently interlinked, RGD-functionalized microgels of 115 {micro}m diameter best supported vascular network formation in vitro and intravascular blood perfusion in vivo. To test the utility of GHCs for the vascular integration of a demanding and therapeutically relevant parenchymal tissue, GHC-based ovarian tissue grafts were implanted in a murine xenograft model and successfully connected to host vasculature, restoring blood flow to embedded human ovarian tissues within 10 days post-implantation. Notably, endothelial cells seeded within GHCs formed viable vasculature without pre-culture. This work establishes GHCs as a biomaterial platform to rapidly connect parenchymal tissues to host vasculature, with broad translational potential across engineered tissue grafting applications.

Pediatric cancer survivors treated with gonadotoxic chemotherapy or radiation face lifelong premature ovarian insufficiency (POI), leading to elevated risk of cardiovascular disease, osteoporosis, and metabolic dysfunction. Pharmacological hormone replacement therapy (HRT) cannot replicate the pulsatile, bidirectional signaling of the hypothalamic-pituitary-gonadal (HPG) axis, leaving a critical therapeutic gap. Immune-isolating hydrogel capsules offer a promising strategy for the implantation of donor ovarian tissue without immunosuppression yet they require optimization for human applications. Here, we engineer a microporous immune-isolating capsule by incorporating thermosensitive gelatin microgels as sacrificial porogens. Microfluidic fabrication yielded monodisperse microgels that dissolved at 37{degrees}C generating disconnected micropores within a non-degradable poly(ethylene glycol) (PEG) matrix. Critically, the diffusion of FSH-scale analogs (40 kDa) increased by almost two-fold through the microporous capsules relative to nanoporous controls, while antibody-scale molecules (150 kDa) were blocked, demonstrating size-discriminating permeability. In ovariectomized mice implanted with encapsulated ovarian xenografts for 20 weeks, microporous capsules restored dynamic HPG-axis signaling evidenced by elevated levels of estradiol and progesterone, FSH suppression, and fluctuating hormone levels that resembled physiological patterns. Microporosity also improved graft viability, increasing stromal cellularity and reducing follicular apoptosis. These findings support microporous immune-isolating capsules as a platform for physiologically authentic therapy for POI.

Recreating 3D bone formation in vitro without biochemical inducers remains a longstanding challenge in preclinical testing. We present a scalable, bioinstructive platform based on polylactic acid microparticles with controlled dimpled surface features that direct mesenchymal stem cell differentiation through endogenous topography-mediated mechanotransduction, establishing a mechanistically validated, additive-free platform. These 3D topographical cues drive cytoskeletal reorganisation and induce osteogenesis via canonical Hedgehog signalling. RNA-Seq revealed early significant upregulation of cytoskeletal components and osteochondral transcription factors, including runt-related transcription factor 2 (RUNX2) and SRY-box transcription factor 9 (SOX9), followed by activation of the insulin growth factor-II pathway and osteogenic commitment. To demonstrate translational potential, two-photon polymerisation lithography was employed to engineer precisely-patterned 3D topographies, inducing graded GLI1 expression without added soluble cues. This establishes a modular, versatile platform for stem cell engineering, offering a topography-driven, non-genetic analogue to mechanogenetics with broad utility for regenerative medicine and human-relevant development of bone models. O_FIG O_LINKSMALLFIG WIDTH=162 HEIGHT=200 SRC="FIGDIR/small/664383v1_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@1b06d7dorg.highwire.dtl.DTLVardef@1e464e1org.highwire.dtl.DTLVardef@19b1299org.highwire.dtl.DTLVardef@1e21f89_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG

Generating 3D bone cell networks in vitro that accurately mimic the dynamic process of osteoblast embedding during early bone formation poses a significant challenge. Herein, we report a synthetic biodegradable macroporous hydrogel for efficient formation of 3D networks from human primary cells, analysis of cell-secreted extracellular matrix (ECM) and microfluidic integration. Using polymerization-induced phase separation, matrix metalloproteinase-sensitive polyethylene glycol hydrogels are formed with interconnected porosity in the presence of living cells. The pore size (5-20 m) and permeability can be fine-tuned by adjusting the concentration and molecular weight of dextran. After encapsulation in these hydrogels, human mesenchymal stem cells and osteoblasts form a 3D cell network within 24 hours. The synthetic nature of this hydrogel enables histological analysis of cell-secreted collagen, a task previously challenging using collagen-derived hydrogels. Moreover, this hydrogel is integrated with a commercial chip, showcasing the potential for microfluidic perfusion cultures. Time-lapsed imaging of fluid flow and fast formation of 3D cell networks is demonstrated on chip. Altogether, this work introduces a versatile synthetic macroporous hydrogel, which can be integrated with microfluidic chip to enable 3D culture of human bone cell networks and analysis of cell-secreted ECM. This hydrogel may facilitate future mechanistic studies on bone development.

The clinical translation of engineered skeletal muscle (eSM) for volumetric muscle regeneration is hindered by the challenge of establishing a functional vascular network capable of sustaining its high metabolic demand and ensuring graft survival. Here, we present a bottom-up biofabrication strategy to generate a pre-vascularized in vitro eSM model through the modular assembly of independently matured muscle and vascular compartments. C2C12 myoblasts were encapsulated within core-shell fibers using rotary wet-spinning (RoWS), yielding anisotropically aligned, multinucleated, and contractile myofibers expressing myosin heavy chain and sarcomeric -actinin. In parallel, gelatin methacryloyl (GelMA)-based microvascular seeds ({micro}VS), pre-endothelialized with human umbilical vein endothelial cells, were engineered to guide rapid and structurally stable vascular formation while preventing uncontrolled capillary self-organization. Fully endothelialized {micro}VS were incorporated into a pro-angiogenic bioink and processed via RoWS to generate tubular vascular fibers with physiological diameters (100-200 m) and continuous CD31-positive lumens. After independent maturation, muscle and vascular constructs were bioassembled into a hierarchically organized tissue and co-cultured. By decoupling myogenic and angiogenic differentiation, this strategy overcomes medium incompatibility typical of conventional co-cultures, preserving compartment-specific architecture and function and establishing a versatile platform for muscle-vascular modeling and translational muscle repair.

BackgroundThe well-functioning of the neurovascular unit (NVU) is supported by the 3D brain physiological microenvironment that allows for extensive neural-neural and neural-vascular interactions. This microenvironment is normally hard to create in traditional in-vitro models such as the transwell model. Organ-on-a-chip (OOC) emerges as advanced model systems by providing better physiological microenvironments. However, NVU modeling in many chip platforms has not met a full 3D condition for neural cultures. MethodsHere, we describe a novel NVU model generated in a microfluidic chip that reproduces the neural-neural and neural-vascular interactions in a full-3D format. The model features an extracellular matrix (ECM) environment that supports both a perfused brain endothelial vessel and 3D cultured neural cells (astrocytes and neurons) beside the tube. Culture conditions were comprehensively optimized for better endothelial tube integrity as well as ECM gel longevity. The model was used to model neuroinflammation-induced brain tube disruption and immune cell extravasation. Furthermore, as a drug testing platform, the model was explored for brain endothelial transcytosis of the heparin-binding EGF-like growth factor (HB-EGF) targeted nanobodies and the data was compared to a parallel transwell model. ResultsImmunofluorescent staining confirmed the expression of endothelial junctional proteins, as well as astrocytic and neuronal markers. The perfused brain endothelial tube exhibited resistance to paracellular leakage of 20 kDa FITC-dextran. Astrocytes and neurons growing in ECM gel developed extensive neural network and showed spontaneous neuronal firing. The neural-vascular interactions were formed through astrocyte migration and axonal outgrowth in the ECM gel towards the tube. Exposure to neuroinflammatory cytokines disrupted the tube barrier, resulting in increased barrier leakage and the recruitment of peripheral blood mononuclear cells (PBMCs) as well as their extravasation. Owing to full-3D model design, endothelial transcytosis and abluminal distribution of the fluorescently labeled HB-EGF targeting Nbs can be clearly visualized in situ. Compared to a transwell model counterpart, the NVU chip model performed better in revealing the binding and transcytosis specificity of the targeted nanobodies. ConclusionsWe demonstrate improved physiological relevance in this full-3D NVU-on-a-chip model. The model could become a faithful platform for NVU research under both healthy and diseased conditions, and can be used as a reliable drug testing platform that aims at developing novel brain-targeted therapeutics.

Recent advances in neuroscience have highlighted the central role of glial cells, particularly astrocytes, in regulating neural network activity through calcium-dependent neuron-glia communication. In parallel, nanostructured cluster-assembled materials have emerged as promising candidates for developing brain-machine interfaces, because of their biomimetic morphology, mechanotransductive properties and neuromorphic behavior. Among these, nanostructured zirconium oxide (ns-ZrOx) thin films have recently demonstrated memristive and signal-processing capabilities compatible with biohybrid neural systems, yet their interaction with heterogeneous neuroglial networks remains poorly understood. Here, we investigate the biocompatibility and functional effects of ns-ZrOx interfaces on primary astrocytes and dorsal root ganglion (DRG) neuron-glia co-cultures, comparing nanostructured and flat zirconia substrates. Both substrates supported cellular adhesion, survival, and differentiation. However, ns-ZrOx selectively enhanced glial calcium signaling, increasing transient amplitude and accelerating response kinetics in both central and peripheral glial populations. Our findings identify ns-ZrOx as an active neurogliomorphic interface capable of modulating neuron-glia communication through nanoscale material properties. By bridging glial physiology with neuromorphic nanomaterials, this work supports the development of hybrid bioelectronic platforms integrating living neural networks with adaptive functional materials for brain-inspired computing and advanced neural interfaces.

Glioblastoma (GBM) is a highly aggressive brain tumor with a five-year survival rate of less than 5%. The current standard of care established 20 years ago includes maximal surgical resection and administration of alkylating agent temozolomide (TMZ). GBM is highly invasive, and GBM cells that evade surgical resection can become resistant to TMZ and develop new aggressive secondary tumors. Post-relapse there are few treatment options available to patients. Tissue engineering approaches suggest the opportunity to develop in vitro models of the GBM tumor microenvironment that may accelerate the discovery of novel therapies for GBM. Here, we report the adaptation of hydrogel microdroplets (microgels) to encapsulate GBM cells in a tailorable 3D matrix to assess patterns of growth and to screen TMZ drug response using patient-derived xenograft (PDX) specimens. We exploit a unique aspect of the microgel system to account for the cellular heterogeneity within the tumor microenvironment (TME). We combine cell-laden microgels generated from TMZ-resistant and TMZ responsive variants of the same PDX specimens to create heterogeneous populations with varying levels of drug sensitivity. We demonstrate a range of drug resistance phenotypes as a function of the ratio of TMZ-responsive to resistance cells and identify the population required for TMZ-resistance to overtake take the response. We then investigate the influence of tumor mimetic shifts in hyaluronic acid bioavailability and hypoxia on patterns of TMZ resistance. We show exposure to matrix-bound hyaluronan increases TMZ resistance and the glioma stem cell population in both cell variants. Lastly, we report an increase in TMZ sensitivity but divergent changes in the GSC subfraction for TMZ resistant vs responsive GBM in the presence of hypoxia. Together, we demonstrate the versatility of cell-laden microgel approach to replicate heterogenous tumor populations, model shifts in the tumor microenvironment, and rapidly screen therapeutic response.

Effective, rapid and functionally perfusable vascularization remains a major challenge in tissue engineering. Current approaches to generate vasculature in vitro require multipart fabrication methods or complex and costly media supplements, limiting their scalability. Here, we demonstrate that exogenous electrical stimulation (estim) offers a promising alternative by enhancing 3D vasculogenesis in engineered human tissues. Exposing 3D endothelial-fibroblast cocultures to pulsed estim promoted the formation of dense and branched vascular networks. In a microfluidic device model, we show that estim induces the formation of an interconnected vascular network that can be perfused, whereas unstimulated control networks remained less mature. Importantly, we demonstrate that upon implantation, estim-pretreated vascular grafts exhibit elevated anastomosis with host and perfusion with blood relative to the untreated grafts. In addition, we use estim to promote engraftment of a vascularized 3D liver construct. Mechanistically, we find that estim induces membrane hyperpolarization in endothelial cells via voltage-gated potassium (KV) channels. Inhibiting KV channels abrogated estims pro-vasculogenic effects in endothelial cells. Conversely, pharmacologically activating hyperpolarization induced endothelial responses even without estim, directly linking KV channel-mediated hyperpolarization as a key mechanism by which estim drives vascular assembly and function. Ultimately, our work establishes estim as a new orthogonal approach to promote formation of perfusable vasculature in engineered tissues.

Astrocytes are key components in reactive gliosis after brain injury, yet defined in vitro models dissecting the influence of extracellular matrix (ECM) components enriched after injury, such as fibrin, on human astrocyte behaviour and function are still missing. Here, we use fibrinogen-derived fibrin and fibrin-alginate-RGD (FAR) 3D hydrogel substrates to examine the influence on human iPSC-derived astrocyte behaviour and their direct conversion into neurons. Astrocytes develop complex morphologies in 3D-FAR hydrogels while are more proliferative and migratory in 3D-Fibrin. Interestingly, gene expression profile analysis revealed different reactive states of astrocytes in 3D-Fibrin and 3D-FAR, which persist over time. The highly inflammatory state in 3D-FAR is largely incompatible with direct neuronal reprogramming hampering the direct conversion even at early stages. Conversely, astrocytes in 3D-Fibrin hydrogels can readily convert into neurons, demonstrating a potent influence of how fibrin is presented on eliciting distinct astrocyte states with great relevance for fate conversion. Research highlightsO_LIFirst transcriptome of human astrocytes in 3D-Fibrin hydrogel and derivative C_LIO_LIFibrin-alginate-RGD (3D-FAR) hydrogel elicits high branching complexity along with exacerbated reactive signature in astrocytes C_LIO_LI3D-Fibrin hydrogels enable proliferation and migration of astrocytes C_LIO_LIDirect conversion of human iPSC-derived astrocytes into neurons in 3D-Fibrin hydrogel C_LI