3D Bioprinted Model Research Articles

3D-bioprinted model of adult neural stem cell microenvironment in Alzheimer’s disease

Neurogenesis plays a major role in neuroplasticity and memory. In adult human and mouse brains, neural stem cells (NSCs) are mainly distributed in two extensively characterized neurogenic niches: the subgranular zone (SGZ) of the hippocampus and the subventricular zone (SVZ) of the lateral ventricles. Impaired neurogenesis is one of the consequences of Alzheimer’s disease (AD), contributing to cognitive decline and progressive memory loss. Developing new in vitro models that resemble this three-dimensional (3D) structure is fundamental for enhancing our understanding of the SVZ neurogenic niche dynamics in AD. Herein, we produced and characterized a 3D-bioprinted model of the adult SVZ neurogenic niche containing amyloid β (Aβ) oligomers, mimicking the NSC microenvironment in AD. In this model, Aβ oligomers induce oxidative stress and reduce the proliferative potential of NSCs, while stimulating neuronal differentiation. We hypothesize that these events are an early attempt of adult NSCs to compensate for neuronal death in AD pathogenesis. Our 3D model simulates the NSC niche physiology, reproducing an early response of NSCs in AD, strengthening the importance of studying the potential of neurogenesis in neurodegeneration.

Advanced strategies in 3D bioprinting for vascular tissue engineering and disease modelling using smart bioinks

ABSTRACT Advanced three-dimensional (3D) bioprinting technology enables the precise production of complex vascular structures and biomimetic models, driving advancements in tissue engineering and disease mechanism research. At the core of this technology is smart bioink, which is suitable for fabricating biomimetic models that can be vascularised to meet the property requirements of various tissues. Examples of smart bioinks include decellularized extracellular matrix (dECM), photocrosslinkable, reversible, and microgel-based biphasic (MB) bioinks, whose mechanical properties can be tuned through external stimuli. This tuning helps generate high-resolution and complex-shaped vascular networks essential for cell survival and functional maturation. This review explores advanced 3D bioprinting strategies using smart bioinks for spatially controlled and perfusable vascular in vitro models, emphasising the reconstruction of functional vascular structures within 3D bioprinted models. It also discusses challenges and future prospects, suggesting that 3D bioprinted models could serve as alternatives to traditional animal models for disease modelling and drug screening.

3D in vitro modeling of the exocrine pancreatic unit using tomographic volumetric bioprinting

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer, a leading cause of cancer-related deaths globally. Initial lesions of PDAC develop within the exocrine pancreas' functional units, with tumor progression driven by interactions between PDAC and stromal cells. Effective therapies require anatomically and functionally relevantin vitrohuman models of the pancreatic cancer microenvironment. We employed tomographic volumetric bioprinting, a novel biofabrication method, to create human fibroblast-laden constructs mimicking the tubuloacinar structures of the exocrine pancreas. Human pancreatic ductal epithelial (HPDE) cells overexpressing the KRAS oncogene (HPDE-KRAS) were seeded in the multiacinar cavity to replicate pathological tissue. HPDE cell growth and organization within the structure were assessed, demonstrating the formation of a thin epithelium covering the acini inner surfaces. Immunofluorescence assays showed significantly higher alpha smooth muscle actin (α-SMA) vs. F-actin expression in fibroblasts co-cultured with cancerous versus wild-type HPDE cells. Additionally,α-SMA expression increased over time and was higher in fibroblasts closer to HPDE cells. Elevated interleukin (IL)-6 levels were quantified in supernatants from co-cultures of stromal and HPDE-KRAS cells. These findings align with inflamed tumor-associated myofibroblast behavior, serving as relevant biomarkers to monitor early disease progression and target drug efficacy. To our knowledge, this is the first demonstration of a 3D bioprinted model of exocrine pancreas that recapitulates its true 3-dimensional microanatomy and shows tumor triggered inflammation.

3D Humanized Bioprinted Tubulointerstitium Model to Emulate Renal Fibrosis In Vitro.

Chronic kidney disease (CKD) leads to a gradual loss of kidney function, with fibrosis as pathological endpoint, which is characterized by extracellular matrix (ECM) deposition and remodeling. Traditionally, in vivo models are used to study interstitial fibrosis, through histological characterization of biopsy tissue. However, ethical considerations and the 3Rs (replacement, reduction, and refinement) regulations emphasizes the need for humanized 3D in vitro models. This study introduces a bioprinted in vitro model which combines primary human cells and decellularized and partially digested extracellular matrix (ddECM). A protocol was established to decellularize kidney pig tissue and the ddECM was used to encapsulate human renal cells. To investigate fibrosis progression, cells were treated with transforming growth factor beta 1 (TGF-β1), and the mechanical properties of the ddECM hydrogel were modulated using vitamin B2 crosslinking. The bioprinting perfusable model replicates the renal tubulointerstitium. Results show an increased Young's modulus over time, together with the increase of ECM components and cell dedifferentiation toward myofibroblasts. Multiple fibrotic genes resulted upregulated, and the model closely resembled fibrotic human tissue in terms of collagen deposition. This 3D bioprinted model offers a more physiologically relevant platform for studying kidney fibrosis, potentially improving disease progression research and high-throughput drug screening.

Heat-inducible CAR-T overcomes adverse mechanical tumor microenvironment in a 3D bioprinted glioblastoma model

Glioblastoma (GBM) presents a significant therapeutic challenge due to the limited efficacy of existing treatments. Chimeric antigen receptor (CAR) T-cell therapy offers promise, but its potential in solid tumors like GBM is undermined by the physical barrier posed by the extracellular matrix (ECM). To address the inadequacies of traditional 2D cell culture, animal models, and Matrigel-based 3D culture in mimicking the mechanical characteristics of tumor tissues, we employed biomaterials and digital light processing-based 3D bioprinting to fabricate biomimetic tumor models with finely tunable ECM stiffness independent of ECM composition. Our results demonstrated that increased material stiffness markedly impeded CAR-T cell penetration and tumor cell cytotoxicity in GBM models. The 3D bioprinted models enabled us to examine the influence of ECM stiffness on CAR-T cell therapy effectiveness, providing a clinically pertinent evaluation tool for CAR-T cell development in stiff solid tumors. Furthermore, we developed an innovative heat-inducible CAR-T cell therapy, effectively overcoming the challenges posed by the stiff tumor microenvironment.

Biodegradable SPI-based hydrogel for controlled release of nanomedicines: A potential approach against brain tumors recurrence

Glioblastoma (GB) is the most common and aggressive brain tumor. The treatment for newly diagnosed glioblastoma is surgical resection of the primary tumor mass, followed by radiotherapy and chemotherapy. However, recurrences frequently occur in proximity to the surgical resection area. In these cases, none of the current therapies is effective. Recently, implantable biomaterials seem to be a promising strategy against GB recurrence. Here, for the first time we combined the tailorable properties of soy-protein hydrogels with the versatility of drug-loaded liposomes to realize a hybrid biomaterial for controlled and sustained nanoparticles release. Hydrogel consisting of 18–20 % w/v soy-protein isolated were fabricated in absence of chemical cross-linkers. They were biodegradable (−10 % and −30 % of weight by hydrolytic and enzymatic degradation, respectively in 3 days), biocompatible (>95 % of cell viability after treatment), and capable of sustained release of intact doxorubicin-loaded liposomes (diffusion coefficient between 10−18 and 10 −19 m2 s−1). A proof-of-concept in a “donut-like” 3D-bioprinted model shows that liposomes released by hydrogels were able to diffuse in a model with a complex extracellular matrix-like network and a 3D structural organization, targeting glioblastoma cells.The combination of nanoparticles' encapsulation capabilities with the hydrogels' structural support and controlled release properties will provide a powerful tool with high clinical relevance that could be applicable for the treatment of other cancers, realizing patient-specific interventions.

Abstract 651: 3D-bioprinted cancer models for target discovery, drug development, and personalized therapy

Abstract Many drugs show promising results in laboratory research, but eventually fail in clinical trials. We hypothesize that one main reason for this translational gap is that the cancer models used are inadequate. Most models lack the complex tumor-stromal cell interactions with their microenvironment which are required for tumor progression. Conventional 2D cultures, where cells grow on rigid plastic plates mainly as mono-cultures of a single type of cells, are not able to recapitulate the complex settings of such interactions. Therefore, there is a need to develop a 3D model that better mimics the tumor microenvironment. Hence, we developed a vascularized, hydrogel-based 3D-bioprinted tumor model consisting of patient-derived tumor and microenvironmental cells. Our 3D-bioprinted models are based on a library of hydrogels that we developed as scaffolds for different tumor types, designed according to the mechanical properties of the tissue/organ of origin. The patient-derived models consist of cells from a biopsy, constructed based on CT/MRI scans, and include functional vessels that allow serum and peripheral blood mononuclear cells (PBMC) to flow when connected to a pump. Using this unique model platform, we identified P-selectin as a novel immune checkpoint in the brain regulating cancer-microglia-tumor-associated macrophages (TAMs) interactions. Moreover, we are currently validating our 3D platform for its ability to mimic patient-specific tumors and their microenvironment in order to predict patient response to different treatments (such as chemotherapy, immunotherapy, and targeted therapies). Hence, we are currently conducting an 80-patient “basket” clinical trial testing different treatments on patient samples to validate the ability of our model to predict patient outcomes covering 7 different cancer types. These unique 3D-bioprinted models have the potential to facilitate target discovery and drug development, as well as to serve as a reliable system for precision medicine. Citation Format: Ronit Satchi-Fainaro, Anne Krinsky, Anshika Katyal, Opal Avramoff, Eilam Yeini, Lena Neufeld, Sharon Halparin, Ronnie Frommer-Shapira. 3D-bioprinted cancer models for target discovery, drug development, and personalized therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 651.

Intracellular proteomics and extracellular vesiculomics as a metric of disease recapitulation in 3D-bioprinted aortic valve arrays.

In calcific aortic valve disease (CAVD), mechanosensitive valvular cells respond to fibrosis- and calcification-induced tissue stiffening, further driving pathophysiology. No pharmacotherapeutics are available to treat CAVD because of the paucity of (i) appropriate experimental models that recapitulate this complex environment and (ii) benchmarking novel engineered aortic valve (AV)-model performance. We established a biomaterial-based CAVD model mimicking the biomechanics of the human AV disease-prone fibrosa layer, three-dimensional (3D)-bioprinted into 96-well arrays. Liquid chromatography-tandem mass spectrometry analyses probed the cellular proteome and vesiculome to compare the 3D-bioprinted model versus traditional 2D monoculture, against human CAVD tissue. The 3D-bioprinted model highly recapitulated the CAVD cellular proteome (94% versus 70% of 2D proteins). Integration of cellular and vesicular datasets identified known and unknown proteins ubiquitous to AV calcification. This study explores how 2D versus 3D-bioengineered systems recapitulate unique aspects of human disease, positions multiomics as a technique for the evaluation of high throughput-based bioengineered model systems, and potentiates future drug discovery.

Modeling inflammatory response using 3D bioprinting of polarized macrophages

The field of drug discovery has seen the rise of three-dimensional (3D) bioprinting as a promising tool for disease modeling. The focus to date has been on tissue engineering and cancer modeling, although the application of 3D-bioprinted models for the study of inflammation using macrophages is still in its infancy. This study explores the potential of bioprinting technology in the development of a 3D macrophage model and macrophage response to inflammatory stimuli using this platform. To this end, we established a 3D-bioprinted macrophage model and assessed the inflammatory and anti-inflammatory response to bacterial endotoxin (lipopolysaccharide, LPS) and the drug ibuprofen (Ibu), respectively. Optimal conditions for macrophage differentiation of the human monocytic cell line, THP-1, in the 3D environment were studied, as well as the effect of the 3D microenvironment on macrophage polarization. Viability of THP-1 cells following the 3D bioprinting process was demonstrated and maintained, allowing successful macrophage differentiation of the cells. The developed 3D-bioprinted macrophage model exhibited elevated expression of selected pro-inflammatory gene and protein markers following exposure to LPS, consistent with polarization from M0 to M1 phenotype. Additionally, the model was responsive to the anti-inflammatory properties of Ibu, demonstrating its potential in drug screening and discovery. The current study highlights the potential of bioprinting in the investigation of inflammatory cell response and behavior in a 3D environment ex vivo, opening new avenues for research in modeling inflammatory responses to various stimuli.  

Cell viability prediction and optimization in extrusion-based bioprinting via neural network-based Bayesian optimization models

The fields of regenerative medicine and cancer modeling have witnessed tremendous growth in the application of 3D bioprinting. Maintaining high cell viability throughout the bioprinting process is crucial for the success of this technology, as it directly affects the accuracy of the 3D bioprinted models, the validity of experimental results, and the discovery of new therapeutic approaches. Therefore, optimizing bioprinting conditions, which include numerous variables influencing cell viability during and after the procedure, is of utmost importance to achieve desirable results. So far, these optimizations have been accomplished primarily through trial and error and repeating multiple time-consuming and costly experiments. To address this challenge, we initiated the process by creating a dataset of these parameters for gelatin and alginate-based bioinks and the corresponding cell viability by integrating data obtained in our laboratory and those derived from the literature. Then, we developed machine learning models to predict cell viability based on different bioprinting variables. The trained neural network yielded regression R2 value of 0.71 and classification accuracy of 0.86. Compared to models that have been developed so far, the performance of our models is superior and shows great prediction results. The study further introduces a novel optimization strategy that employs the Bayesian optimization model in combination with the developed regression neural network to determine the optimal combination of the selected bioprinting parameters to maximize cell viability and eliminate trial-and-error experiments. Finally, we experimentally validated the optimization model’s performance.

Advantages and limitations of using cell viability assays for 3D bioprinted constructs

Bioprinting shows promise for bioengineered scaffolds and three-dimensional (3D) disease models, but assessing the viability of embedded cells is challenging. Conventional assays are limited by the technical problems that derive from using multi-layered bioink matrices dispersing cells in three dimensions. In this study, we tested bioprinted osteogenic bioinks as a model system. Alginate- or gelatin-based bioinks were loaded with/without ceramic microparticles and osteogenic cells (bone tumor cells, with or without normal bone cells). Despite demonstrating 80%–90% viability through manual counting and live/dead staining, this was time-consuming and operator-dependent. Moreover, for the alginate-bioprinted scaffold, cell spheroids could not be distinguished from single cells. The indirect assay (alamarBlue), was faster but less accurate than live/dead staining due to dependence on hydrogel permeability. Automated confocal microscope acquisition and cell counting of live/dead staining was more reproducible, reliable, faster, efficient, and avoided overestimates compared to manual cell counting by optical microscopy. Finally, for 1.2 mm thick 3D bioprints, dual-photon confocal scanning with vital staining greatly improved the precision of the evaluation of cell distribution and viability and cell–cell interactions through the z-axis. In summary, automated confocal microscopy and cell counting provided superior accuracy for the assessment of cell viability and interactions in 3D bioprinted models compared to most commonly and currently used techniques.

High Concentrations of Cannabidiol Induce Neurotoxicity in Neurosphere Culture System.

Recent studies have demonstrated that cannabinoids are potentially effective in the treatment of various neurological conditions, and cannabidiol (CBD), one of the most studied compounds, has been proposed as a non-toxic option. However, the adverse effects of CBD on neurodevelopmental processes have rarely been studied in cell culture systems. To better understand CBD's influence on neurodevelopment, we exposed neural progenitor cells (NPCs) to different concentrations of CBD (1µM, 5µM, and 10µM). We assessed the morphology, migration, differentiation, cell death, and gene expression in 2D and 3D bioprinted models to stimulate physiological conditions more effectively. Our results showed that CBD was more toxic at higher concentrations (5µM and 10µM) and affected the viability of NPCs than at lower concentrations (1µM), in both 2D and 3D models. Moreover, our study revealed that higher concentrations of CBD drastically reduced the size of neurospheres and the number of NPCs within neurospheres, impaired the morphology and mobility of neurons and astrocytes after differentiation, and reduced neurite sprouting. Interestingly, we also found that CBD alters cellular metabolism by influencing the expression of glycolytic and β-oxidative enzymes in the early and late stages of metabolic pathways. Therefore, our study demonstrated that higher concentrations of CBD promote important changes in cellular functions that are crucial during CNS development.

Three-dimensional bioprinting for musculoskeletal regeneration and disease modeling

Musculoskeletal disease and injury are highly prevalent disorders that impose tremendous medical and socioeconomic burdens. Tissue engineering has attracted increasing attention as a promising technique of regenerative medicine to restore degenerative or damaged tissues and is used to produce functional disease models. As a revolutionary technology, three-dimensional (3D) bioprinting has demonstrated a considerable potential in enhancing the versatility of tissue engineering. 3D bioprinting allows for the rapid and accurate spatial patterning of cells, growth factors, and biomaterials to generate biomimetic tissue constructs. Meanwhile, 3D-bioprinted in vitro models also offer a viable option to enable precise pharmacological interventions in various diseases. This review provides an overview of 3D bioprinting methods and bioinks for therapeutic applications and describes their potential for musculoskeletal tissue regeneration. We also highlight the fabrication of 3D-bioprinted models for drug development targeting musculoskeletal disease. Finally, the existing challenges and future perspectives of 3D bioprinting for musculoskeletal regeneration and disease modeling are discussed.

Building in vitro models for mechanistic understanding of liver regeneration in chronic liver diseases.

The liver has excellent regeneration potential and attains complete functional recovery from partial hepatectomy. The regenerative mechanisms malfunction in chronic liver diseases (CLDs), which fuels disease progression. CLDs account for 2 million deaths per year worldwide. Pathophysiological studies with clinical correlation have shown evidence of deviation of normal regenerative mechanisms and its contribution to fueling fibrosis and disease progression. However, we lack realistic in vitro models that can allow experimental manipulation for mechanistic understanding of liver regeneration in CLDs and testing of candidate drugs. In this review, we aim to provide the framework for building appropriate organotypic models for dissecting regenerative responses in CLDs, with the focus on non-alcoholic steatohepatitis (NASH). By drawing parallels with development and hepatectomy, we explain the selection of critical components such as cells, signaling, and, substrate-driven biophysical cues to build an appropriate CLD model. We highlight the organoid-based organotypic models available for NASH disease modeling, including organ-on-a-chip and 3D bioprinted models. With the focus on bioprinting as a fabrication method, we prescribe building in vitro CLD models and testing schemes for exploring the regenerative responses in the bioprinted model.

Incorporation of hair follicles in 3D bioprinted models of human skin.

Current approaches fail to adequately introduce complex adnexal structures such as hair follicles within tissue engineered models of skin. Here, we report on the use of 3D bioprinting to incorporate these structures in engineered skin tissues. Spheroids, induced by printing dermal papilla cells (DPCs) and human umbilical vein cells (HUVECs), were precisely printed within a pregelled dermal layer containing fibroblasts. The resulting tissue developed hair follicle-like structures upon maturation, supported by migration of keratinocytes and melanocytes, and their morphology and composition grossly mimicked that of the native skin tissue. Reconstructed skin models with increased complexity that better mimic native adnexal structures can have a substantial impact on regenerative medicine as grafts and efficacy models to test the safety of chemical compounds.

The 3D bioprinted human induced pluripotent stem cell-derived cardiac model: Toward functional and patient-derived in vitro models for disease modeling and drug screening

More relevant human tissue models are needed to produce reliable results when studying disease mechanisms of genetic diseases and developing or testing novel drugs in cardiac tissue engineering (TE). Three-dimensional (3D) bioprinting enables physiologically relevant positioning of the cells inside the growth matrix according to the detailed digital design. Here we combined human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs) with methacrylated gelatin (GelMA) and collagen I-based bioink and 3D extrusion bioprinted a cardiac in vitro model for disease modeling and drug screening. Bioprinted constructs were characterized for their rheological properties, swelling behavior, degradation, as well as shape fidelity. The printed structures demonstrated good mechanical properties and high shape fidelity upon culture. Immunocytochemistry revealed elongated hiPSC-CMs growing inside the structures and the presence of the connexin 43 marker, indicating cardiac gap junctions between printed cells and tissue formation. Extensive functional analyses with calcium imaging showed normal functionality and calcium-handling properties for hiPSC-CMs. Finally, suitability of this 3D bioprinted construct for patient-specific disease modeling was demonstrated by bioprinting hiPSC-CMs from a patient carrying an inherited gene mutation causing catecholaminergic polymorphic ventricular tachycardia (CPVT). CPVT hiPSC-CMs responded to adrenaline treatment in the 3D bioprinted model in a manner that is characteristic for CPVT disease specific phenotype. Thus, the 3D bioprinted hiPSC-CM in vitro model has great potential for disease modeling and drug screening in cardiac tissue engineering.

World's First Long-Term Colorectal Cancer Model by 3D Bioprinting as a Mechanism for Screening Oncolytic Viruses.

Long-term modelization of cancer as it changes in the human body is a difficult goal, particularly when designing and testing new therapeutic strategies. This becomes even more difficult with metastasis modeling to show chemotherapeutic molecule delivery directly to tumoral cells. Advanced therapeutics, including oncolytic viruses, antibody-based and cell-based therapies are increasing. The question is, are screening tests also evolving? Next-generation therapeutics need equally advanced screening tests, which whilst difficult to achieve, are the goal of our work here, creating models of micro- and macrotumors using 3D bioprinting. We developed advanced colorectal cancer tumor processing techniques to provide options for cellular expansion, microtumor printing, and long-term models, which allow for the evaluation of the kinetics of penetration testing, therapeutic success, targeted therapies, and personalized medicine. We describe how we tested tumors from a primary colorectal patient and, applying 3D bioprinting, matured long-term models for oncolytic metastatic screening. Three-dimensional microtumors were kept alive for the longest time ever recorded in vitro, allowing longitudinal studies, screening of oncolytic viruses and realistic modelization of colorectal cancer. These 3D bioprinted models were maintained for around 6 months and were able to demonstrate the effective delivery of a product to the tumoral environment and represent a step forward in therapeutic screening.

Engineered dermis loaded with confining forces promotes full-thickness wound healing by enhancing vascularisation and epithelialisation

Tissue-engineered skin is ideal for clinical wound repair. Restoration of skin tissue defects using tissue-engineered skin remains a challenge owing to insufficient vascularisation. In our previous study, we developed a 3D bioprinted model with confined force loading and demonstrated that the confined force can affect vascular branching, which is regulated by the YAP signalling pathway. The mechanical properties of the model must be optimised to suture the wound edges. In this study, we explored the ability of a GelMA-HAMA-fibrin scaffold to support the confined forces created by 3D bioprinting and promote vascularisation and wound healing. The shape of the GelMA-HAMA-fibrin scaffold containing 3% GelMA was affected by the confined forces produced by the embedded cells. The GelMA-HAMA-fibrin scaffold was easy to print, had optimal mechanical properties, and was biocompatible. The constructs were successfully sutured together after 14 d of culture. Scaffolds seeded with cells were transplanted into skin tissue defects in nude mice, demonstrating that the cell-seeded GelMA-HAMA-fibrin scaffold, under confined force loading, promoted neovascularisation and wound restoration by enhancing blood vessel connections, creating a patterned surface, growth factors, and collagen deposition. These results provide further insights into the production of hydrogel composite materials as tissue-engineered scaffolds under an internal mechanical load that can enhance vascularisation and offer new treatment methods for wound healing. Statement of significanceTissue-engineered skin is ideal for use in clinical wound repair. However, treatment of tissue defects using synthetic scaffolds remains challenging, mainly due to slow and insufficient vascularization. Our previous study developed a 3D bioprinted model with confined force loading, and demonstrated that confined force can affect vascular branching regulated by the YAP signal pathway. The mechanical properties of the construct need to be optimized for suturing to the edges of wounds. Here, we investigated the ability of a GelMA-HAMA-fibrin scaffold to support the confined forces created by 3D bioprinting and promote vascularization in vitro and wound healing in vivo. Our findings provide new insight into the development of degradable macroporous composite materials with mechanical stimulation as tissue-engineered scaffolds with enhanced vascularization, and also provide new treatment options for wound healing.

Abstract P3024: Endothelial To Mesenchymal Transition Frequency Increases In Williams Syndrome Pulmonary Artery Endothelial Cells In Novel 3D Bioprinted In Vitro Arterial Model

Introduction: Pulmonary artery stenosis (PAS) affects 1 in 2000 live births worldwide, with several causes, most commonly by genetic mutations that lead to or are associated with other congenital heart diseases (CHD). Despite its prevalence, long-term treatment strategies for patients with PAS remains ineffective due to its heterogenous etiology. In the last few decades, researchers have found hemodynamic forces to be a great contributor to stenosis development because it induces endothelial cell (EC) dysfunction through endothelial-to-mesenchymal transition (EndMT). Current pulmonary artery models, in vivo and in vitro , are ineffective in uncovering this mechanism in PAS because they either are unable to recapitulate the phenotype or the micromechanical environment. Methods: To address these limitations, we developed and optimized a high-throughput 3D bioprinted in vitro vascular model that recapitulates patient-specific disease states to determine how EndMT plays a role in stenosis development. This bioprinted model will be a cellularized bilayer comprised of EC and smooth muscle cells (SMC) sourced from either human primary cells or our established Williams Syndrome (WS) induced-pluripotent stem cell (iPSC) lines. WS was chosen due to its high predisposition in developing PAS, around 50%. Our hypothesis is that utilizing our 3D bioprinted model, we will demonstrate how alterations in hemodynamic forces, specifically flow regiments, will further promote EndMT in the WS group. Results: Encapsulated SMC functionality and differentiated phenotype was confirmed by calcium measurement and immunohistochemistry, respectively. Single-cell RNA sequencing (scRNA-seq) was used to examine EC, SMC, EC-SMC crosstalk, and EndMT gene expression profiles. Conclusion: This work represents a new and substantive departure from conventional in vitro vascular modeling, for it will allow us to identify initial vascular cellular responses in acute non-homeostatic conditions and uncover unique signaling pathways found in multiple CHD related PAS. This fundamental knowledge from our vascular mimics can then be applied to facilitate translational advancements in treatment of PAS via surgical and transcatheter intervention methods.

Using 3D-bioprinted models to study pediatric neural crest-derived tumors.

The use of three-dimensional (3D) bioprinting has remained at the forefront of tissue engineering and has recently been employed for generating bioprinted solid tumors to be used as cancer models to test therapeutics. In pediatrics, neural crest-derived tumors are the most common type of extracranial solid tumors. There are only a few tumor-specific therapies that directly target these tumors, and the lack of new therapies remains detrimental to improving the outcomes for these patients. The absence of more efficacious therapies for pediatric solid tumors, in general, may be due to the inability of the currently employed preclinical models to recapitulate the solid tumor phenotype. In this study, we utilized 3D bioprinting to generate neural crest-derived solid tumors. The bioprinted tumors consisted of cells from established cell lines and patient-derived xenograft tumors mixed with a 6% gelatin/1% sodium alginate bioink. The viability and morphology of the bioprints were analyzed via bioluminescence and immunohisto chemistry, respectively. We compared the bioprints to traditional twodimensional (2D) cell culture under conditions such as hypoxia and therapeutics. We successfully produced viable neural crest-derived tumors that retained the histology and immunostaining characteristics of the original parent tumors. The bioprinted tumors propagated in culture and grew in orthotopic murine models. Furthermore, compared to cells grown in traditional 2D culture, the bioprinted tumors were resistant to hypoxia and chemotherapeutics, suggesting that the bioprints exhibited a phenotype that is consistent with that seen clinically in solid tumors, thus potentially making this model superior to traditional 2D culture for preclinical investigations. Future applications of this technology entail the potential to rapidly print pediatric solid tumors for use in high-throughput drug studies, expediting the identification of novel, individualized therapies.