Bioprinted Tissues Research Articles

Three-Dimensional Bioprinting of Organs: Modern Trends.

The paper presents an overview of some modern technologies for three-dimensional (3D) bioprinting of human tissues and organs. 3D bioprinting of human organs is increasingly used for the production and transplantation of artificial biological organs. Existing technologies of 3D bioprinting using bioink on a special substrate are considered. The features of the production of bioinks using biocompatible polymer compounds, hydrogels are given, some popular modern bioprinters are noted. Modern technologies of bioprinting of tissues of human organs are considered: skin, liver, lungs, heart, brain, existing technological problems in this area are given. Based on the analysis, the future prospects for the development of bioprinting technology for human organs are noted.

Freeform cell-laden cryobioprinting for shelf-ready tissue fabrication and storage

One significant drawback of existing bioprinted tissues is their lack of shelf-availability caused by complications in both fabrication and storage. Here, we report a cryobioprinting strategy for simultaneously fabricating and storing cell-laden volumetric tissue constructs through seamlessly combining extrusion bioprinting and cryopreservation. The cryobioprinting performance was investigated by designing, fabricating, and storing cell-laden constructs made of our optimized cryoprotective gelatin-based bioinks using a freezing plate with precisely controllable temperature. The in situ freezing process further promoted the printability of cell-laden hydrogel bioinks to achieve freeform structures otherwise inconvenient with direct extrusion bioprinting. The effects of bioink composition on printability and cell viability were evaluated. The functionality of the method was finally investigated using cell differentiation and chick ex ovo assays. The results confirmed the feasibility and efficacy of cryobioprinting as a single-step method for concurrent tissue biofabrication and storage.

Advanced Strategies for 3D Bioprinting of Tissue and Organ Analogs Using Alginate Hydrogel Bioinks.

Alginate is a natural polysaccharide that typically originates from various species of algae. Due to its low cost, good biocompatibility, and rapid ionic gelation, the alginate hydrogel has become a good option of bioink source for 3D bioprinting. However, the lack of cell adhesive moieties, erratic biodegradability, and poor printability are the critical limitations of alginate hydrogel bioink. This review discusses the pivotal properties of alginate hydrogel as a bioink for 3D bioprinting technologies. Afterward, a variety of advanced material formulations and biofabrication strategies that have recently been developed to overcome the drawbacks of alginate hydrogel bioink will be focused on. In addition, the applications of these advanced solutions for 3D bioprinting of tissue/organ mimicries such as regenerative implants and in vitro tissue models using alginate-based bioink will be systematically summarized.

Capillary-like Formations of Endothelial Cells in Defined Patterns Generated by Laser Bioprinting.

Bioprinting is seen as a promising technique for tissue engineering, with hopes of one day being able to produce whole organs. However, thick tissue requires a functional vascular network, which naturally contains vessels of various sizes, down to capillaries of ~10 µm in diameter, often spaced less than 200 µm apart. If such thick tissues are to be printed, the vasculature would likely need to be printed at the same time, including the capillaries. While there are many approaches in tissue engineering to produce larger vessels in a defined manner, the small capillaries usually arise only in random patterns by sprouting from the larger vessels or from randomly distributed endothelial cells. Here, we investigated whether the small capillaries could also be printed in predefined patterns. For this purpose, we used a laser-based bioprinting technique that allows for the combination of high resolution and high cell density. Our aim was to achieve the formation of closed tubular structures with lumina by laser-printed endothelial cells along the printed patterns on a surface and in bioprinted tissue. This study shows that such capillaries are directly printable; however, persistence of the printed tubular structures was achieved only in tissue with external stimulation by other cell types.

Non-destructive mechanical assessment for optimization of 3D bioprinted soft tissue scaffolds

Non-destructive mechanical assessment for optimization of 3D bioprinted soft tissue scaffolds

Discovering the technology evolution pathways for 3D printing (3DP) using bibliometric investigation and emerging applications of 3DP during COVID-19

Additive manufacturing (AM) is advantageous in terms of lower carbon emissions, less material-wastage, mobility of digital design, product customization and simpler supply chain management. Moreover, during the global COVID-19 crisis, a robust and IT-driven manufacturing technology was highly required to cope with the peak demands of medical and basic emergency supplies. 3D printing (3DP) enabled the manufacturers to fulfill the deficiencies of healthcare equipment for medical professionals and patients throughout the world. In this paper, some emerging applications and challenges incurred by 3D printing during COVID-19 were briefly summarized. 3D printed PLA-based biodegradable mask filters, medical face shields, respiratory protective equipment and 3D bioprinted tissue models for COVID research are some significant contributions of AM. In this paper, a CiteSpace based bibliometric investigation of 3DP-related literature was conducted, to identify the technology evolution pathways for 3D printing, using the data retrieved from Web of Science and published between 1986 and 2021. The main contributing forces including countries, journals, institutions and subject areas were determined. Knowledge clusters were established to identify networks of the most prolific keywords and documents. In addition, a hierarchical knowledge foundation and hotspots of 3DP were recommended for future research. It was revealed that the policy support of the USA, China, England and Germany was significantly favorable for the development of 3DP research. This article provides insights into the COVID-based applications of 3DP and the research dynamics of this field, which can help in the decision-making process to incorporate innovative and emerging technologies in the AM industry.

Drug-releasing Microspheres for Stem Cell Differentiation.

The ability of stem cells to differentiate into specialized cells make them a valuable tool for therapeutic applications. 3D bioprinting, a subset of additive manufacturing, uses bioinks composed of cells and biomaterials to create living tissues. The use of bioactive factors like small molecules and proteins can promote stem cell differentiation into the desired cell phenotypes for tissue regeneration. Small molecules can accelerate the process of regeneration in tissue engineering, maintain bioactivity in a biological environment, and minimize the costs associated with this process. Additionally, they can be encapsulated in specialized drug-delivery devices called microspheres for controlled release. Microspheres are small (1-1000 μm) spherical particles usually made from biodegradable and biocompatible polymers that can be loaded with drugs and other bioactive components. They can then be integrated into stem-cell-laden bioinks used to form bioprinted tissues, where they will release the encapsulated drug and promote differentiation of stem cells into the desired mature cell type. Microspheres can be widely used to encapsulate a broad range of therapeutic agents, including hydrophilic and hydrophobic small molecule drugs, DNA, and proteins. The release of encapsulated molecules occurs through degradation and erosion of the polymer matrix. This article provides detailed protocols for fabricating and sterilizing drug-releasing microspheres made from poly-ε-caprolactone, a promising biodegradable polymer often used for controlled drug delivery due to its biocompatibility and biodegradation kinetics. Additional protocols describe characterization of the loading and size of microspheres as well as incorporation of microspheres into a fibrin-based bioink for 3D bioprinting. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Fabrication of drug-releasing PCL microspheres Support Protocol 1: Preparation of microspheres for determination of encapsulation efficiency by HPLC Support Protocol 2: Preparation of microspheres for SEM analysis Basic Protocol 2: Incorporation of microspheres into fibrin-based bioink.

Bioprinting of bioactive tissue scaffolds from ecologically-destructive fouling tunicates

Urochordates are the closest invertebrate relative to humans and commonly referred to as tunicates, a name ascribed to their leathery outer “tunic”. The tunic is the outer covering of the organism which functions as the exoskeleton and is rich in carbohydrates and proteins. Invasive or fouling tunicates pose a great threat to the indigenous marine ecosystem and governments spend several hundred thousand dollars for tunicate management, considering the huge adverse economic impact it has on the shipping and fishing industries. In this work, the environmentally destructive colonizing tunicate species of Polyclinum constellatum was successfully identified in the coast of Abu Dhabi and methods of sustainably using it as wound-dressing materials, decellularized extra-cellular matrix (dECM) scaffolds for tissue engineering applications and bioinks for bioprinting of tissue constructs for regenerative medicine are proposed. The intricate three-dimensional nanofibrous cellulosic networks in the tunic remain intact even after the multi-step process of decellularization and lyophilization. The lyophilized dECM tunics possess excellent biocompatibility and remarkable tensile modulus of 3.85 ± 0.93 MPa compared to ∼0.1–1 MPa of other hydrogel systems. This work demonstrates the use of lyophilized tunics as wound-dressing materials, having outperformed the commercial dressing materials with a capacity of absorbing 20 times its weight in the dry state. This work also demonstrates the biocompatibility of dECM scaffold and dECM-derived bioink (3D bioprinting with Mouse Embryonic Fibroblasts (MEFs)). Both dECM scaffolds and bioprinted dECM-based tissue constructs show enhanced metabolic activity and cell proliferation over time. Sustainable utilization of dECM-based biomaterials from ecologically-destructive fouling tunicates proposed in this work helps preserve the marine ecosystem, shipping and fishing industries worldwide, and mitigate the huge cost spent for tunicate management.

Regulation of vascular branch formation in 3D bioprinted tissues using confining force

The quality of the vascular network is key to the success of skin transplants. For skin grafts prepared using a tissue engineering approach, vascularization is a critical step determining tissue survival. Prevascularization of bioengineered tissues is the basis for the effective establishment of high-quality vascular networks. Previously, we established a 3D bioprinted model to simulate the mechanical stimulation of vascular tissue development. Based on this, here, we create a prevascularized tissue using 3D bioprinting and show that the vascular branches of the tissue can be controlled by the confining forces created by changing the size of the polycaprolactone (PCL) framework. In addition, it was found that the Yes-associated protein (YAP) participates in the regulation of vascular branch formation in the tissue. A close relationship was found between the width of the cell-fibrin strip, the magnitude of the force and the number of vascular branches in the bioprinted tissue exists. Together, our findings indicate that vascularization of engineered skin tissue is a complex yet controllable process, and precise mechanical control can lead to effective vascular network generation.

P.170: Preliminary Results on the Development of a Perfusion Device to Study the Function of 3D Bioprinted Pancreatic Tissue In Vitro

Background: The emergent field of 3D bioprinting has the potential to overcome hypoxia and lack of immunoprotection, two major limitations of islet transplantation in encapsulation systems. When transitioning tissue engineered constructs from bench to bedside, several design parameters must be considered, including tissue geometry, islet density, and oxygen tension in different transplantation sites. To address this challenging multifactorial optimization process, we have designed an in vitro flow device that can be used to evaluate bioprinted tissue performance in vitro under different flow, oxygen and tissue geometry conditions. The aim of this work was to assess the function and viability of single 3D bioprinted core-shell fibres containing pseudo-islets or human islets in a novel perfusion device designed to accommodate bioprinted tissues. Methods: The perfusion device was designed using computer-aided design modelling. Computational fluid dynamics (CFD) was used to simulate flow and compute input parameters that would ensure laminar, uniform flow. Pseudo-islets were formed after aggregation of MIN6 cells in AggrewellTM culture plates during 48h. Pseudo-islets and human islets were 3D bioprinted in alginate using an RX1 bioprinter (AspectBiosystems, Vancouver, CA). Free or encapsulated pseudo-islets or human islets were cultured in static conditions as controls. Pseudo-islet function was determined using a glucose stimulation insulin secretion (GSIS) assay in static or perfused conditions. Viability of human islets was evaluated using Calcein AM/Ethidium Homodimer staining. Results: Based on our computational models, by setting the inlet flow speed to 1.0 cm/s, we can achieve physiological flow velocities within the device. This inlet flow speed is also expected to generate smooth, undisturbed streamlines and laminar flow. After a 24h culture in the perfusion device, we detected increased insulin secretion of pseudo-islets in fibres in response to high glucose stimulation (ratio of secreted to total insulin of 0.27% after 15 min at high glucose vs 0.13% after 15 min at low glucose). Human islets bioprinted in fibres showed higher cell viability compared to free human islets after a 48h culture (95% of viability in fibres cultured in the perfusion device compared to 80% viability for free islets). As these results were obtained from a single human pancreas donor, further studies are needed to assess the reproducibility and statistical significance of these observations. Conclusion: These promising preliminary results suggest that (1) the flow device we designed can be used to evaluate the performance of 3D bioprinted pancreatic tissue and (2) pseudo-islets and human islets can be safely bioprinted in core-shell fibres. The platform can be used to streamline the characterization and optimize the configuration in vitro of promising artificial tissues at human-scale. MITACS Accelerate in collaboration with Aspect Biosystems Ltd. Stem Cell Network. ThéCell. CMDO, réseau de recherche en santé cardiométabolique, diabète et obésité. Montreal Diabetes Research Center. Centre Québécois sur les Matériaux Fonctionnels. PROTEO. McGill Regenerative Medicine. Bioencapsulation Research Group.

307.2: Bioprinted Immune-protective Islet-containing Tissues Successfully Regulate Blood Glucose in Rodent Models of Type 1 Diabetes

Introduction: Type 1 diabetes (T1D) is a disease characterized by elevated blood glucose due to insufficient insulin release from pancreatic β-cells. Transplantation of cadaveric islets demonstrates that cell therapy can fully reverse hyperglycemia. However, limited cell supply, immune rejection of implanted allogeneic cells, and cell survival represent major challenges. Cell encapsulation has great potential to overcome these challenges by blocking immune cell access to the grafts while allowing nutrient exchange and secreted products from the implanted cells to be delivered to the body. In this study, we use a unique microfluidic bioprinting technology to precisely control the placement of cells and biomaterials within 3D tissues with micro-architectures optimized for cellular fitness and immune protection. Methods: Living tissues consisting of fibres with a cell-containing core and immune-protective alginate-based shell were generated using Aspect Biosystems’ RX1 bioprinter technology. Core-shell fibres with reaggregated primary human pancreatic islets or embryonic stem cell-derived β-cells were tested in vitro using viability and functional (glucose-stimulated insulin secretion, GSIS) assays. Bioprinted tissues were then implanted into the IP space or omentum of streptozotocin (STZ)-induced diabetic mice and rats, respectively. Glucose homeostasis, body weight, and human C-peptide secretion were monitored for up to 3 months following implantion. Retrieved grafts were fixed and analyzed by histology (H&E, Masson’s trichrome stain) and immunohistochemistry (α-SMA, CD45) to quantify fibrotic encapsulation and immune cell infiltration. Results: Bioprinted tissues supported viability and dynamic insulin secretion of cells in vitro up to 28 days. When transplanted into immunodeficient and immunocompetent diabetic rodents, bioprinted tissues containing reaggregated human islets successfully regulated blood glucose for up to 3 months (Figure 1), although normoglycemia was only sustained in a subset of immunocompetent animals and associated with variable fibrosis. Post-retrieval viability stain, assessment of GSIS, and histology revealed high viability and functionality of implanted cells, and the absence of leukocyte infiltration through the shell. Discussion: This is the first study showing a fully 3D bioprinted tissue composed of a core/shell fibre can successfully deliver a therapeutic dose of xenogeneic cells into a diabetic animal (Figure 2). The unique features of the microfluidic technology were leveraged to bioprint an implantable and retrievable tissue patch that merges the benefits of a single fibre (cell fitness, access to nutrients, immune-protection, perm-selectivity) with those provided by a 3D structure (retrievability, ease of implant, structural integrity). The promising results obtained in rodent studies warrant further investigation to minimize fibrosis and explore the scaling-up of bioprinted tissues in large animal models of T1D.NRC-IRAP. NSERC. Stem Cell Network. Genome BC.

307.1: Bionic Pancreas - The First Results of Functionality Bionic Tissue Model With Pancreatic Islets

Introduction: 3D bioprinting using living cells is the latest technique in the field of biomedical engineering. One of the most important points of the procedure is to preserve the cells and leave them fully functional in the resulting bioconstruction. In the case of bioprinting of bionic tissue, it is important to provide cells with access to nutrients and gas exchange. These are the first results of printed bionic petals and the first studies on a mouse model. Material: The research was carried out on 60 mice (SCID). Diabetes induction was not undertaken in small animal studies because T1D is difficult to achieve in a mouse model. The mice were divided into 3 groups: a control; the IsletTx in which porcine pancreatic islets were transplanted under the renal capsule; 3D Bioprint in which the 3D bioink petals consisted of bioink A and porcine islets. The petals were transplanted into the dorsal part of the muscles under the skin. Daily glucose measurement was performed and the level of C-peptide was tested every 7 days. Results: The results obtained in mice initially showed no differences in the concentration of peptide-C and glucose between the groups. However, as early as 7 days after transplantation, both parameters analyzed in the fasting state were significantly lower in the IsletsTx and 3Dbioprinted groups compared to the control group. On day 14, decreased values of C-peptide and glucose were observed only in the group with petals transplants. Conclusion: Transplantation of bionic petals in mice resulted in a decrease in mean glucose levels. The mice showed a reduced concentration of their own C-peptide, which can indicate relief in mice’s owns islets function. None of the animals died due to postoperative complications or the lack of biocompatibility with the bionic structure. The positive effect of transplantation was maintained throughout the experiment, which proves the optimal selection of the composition of the bioink and the bioprinting parameters. This study was financially supported by The National Centre for Research and Development STRATEGMED3/305813/2/NCBR/2017.

3D Spheroid Cell Cultures and Their Role in Bone Regeneration: a Systematic Review

Recently, the 3D spheroid cell culture application has been extensively used in the treatment of bone defects. A wide variety of methodologies have been used, which has made the comparison of results complex. Therefore, this systematic review has two aims: (i) to perform an analysis focused on the role of 3D spheroid cell culture in bone regeneration strategies; and (ii) address the main challenges in clinical application. A search of the following keywords "3D cell culture", "spheroid", and "bone regeneration" was carried out in the PubMed, Scopus, and ScienceDirect databases and limited to the years 2010-2020. Studies were included if their primary objective was the behavior of cell aggregates to formed spheroids structures by different 3D cell culture techniques focused on the regeneration of bone tissue. To address the risk of bias for in vitro studies, the United States national toxicology program tool was applied, and descriptive statistics of the data were performed, with the SPSS V.22 program. A total of 16 studies were included, which met the established criteria corresponding to in vitro and in vitro/in vivo studies; most of these studies used stem cells for the 3D cell spheroids. The most often methods used for the 3D formation were low adherence surface and rotational methods, moreover, mesenchymal stem cells were the cell line most frequently used because of their regenerative potential in the field of bone tissue engineering. Although the advances in research on the potential use of 3D spheroids in bone regeneration have made great strides, the constant innovation in cell spheroid formation methodologies means that clinical application remains in the future as strategy for 3D tissue bioprinting.

Abstract 14396: Cardioprotective Effects Of Glycyrrhizin On Hyperglycemic Cardiac Tissues

Introduction: Myocardial fibrosis and dysfunction is one of the major cardiac complications of long-term diabetes. Prolonged hyperglycemia is known to induce myocardial dysfunction often leading up to heart failure. Hypothesis: The objective of this study was to investigate the cardioprotective effect of glycyrrhizin (GLC) on myocardial damage in engineered in-vitro human cardiac tissues. Engineered 3D tissue chips present an ideal microenvironment via therapeutically relevant interfaces to study molecular- and cellular-level events and mimic human-specific disease states, and identify new therapeutic targets in vitro. Methods: AC16 human cardiomyocyte cells were used to 3D bioprint cardiac tissue chips based on prior published work. In our study, the 3D bioprinted cardiac tissue chips (CTC) were cultured using normo- (5mM) and hyper-glycemic (25mM) conditions for up to 48 hrs. For the GLC treatment group, a subset of CTC cultured using hyperglycemic conditions were treated with 50 mM of GLC for 24 hours. Results: CTC cultured under hyperglycemic conditions demonstrated altered levels of connexin-43 (CX43) and Troponin-I implying cardiomyocyte injury. Exposure to hyperglycemia revealed changes in epigenetic markers: histone methylation marker (H3K9me)-1, Sirtuin-1, and Histone Deacetylase (HDAC)-2 as well as in inflammatory and stress related mediators such as heat shock protein (HSP)-60, receptor for advanced glycation end products (RAGE), toll like receptor (TLR)-4, high mobility group box (HMGB)-1 and CXC chemokine receptor (CXCR)-4. CTC exposed to 25mM glucose for 24 hours resulted in the downregulation of HSP60 and Sirtuin-1. Prolonged exposure to hyperglycemia led to decrease in the expression of CX43 and CXCR4; thereby adversely affecting cardiomyocyte function. Upregulated expression of DNA-binding nuclear protein HMGB1 along with changes in H3K9me1 indicated long-term hyperglycemia-induced damage to cardiomyocytes. GLC treated CTC exhibited a decrease in the expression of RAGE, TLR4 and also demonstrated altered expression of CX43, CXCR4, and troponin I. Conclusions: This study suggests that GLC possesses cardioprotective effects in human cardiomyocytes exposed to prolonged hyperglycemia.

A Bioprinted Tubular Intestine Model Using a Colon-Specific Extracellular Matrix Bioink.

Tremendous advances have been made toward accurate recapitulation of the human intestinal system in vitro to understand its developmental process, and disease progression. However, current in vitro models are often confined to 2D or 2.5D microarchitectures, which is difficult to mimic the systemic level of complexity of the native tissue. To overcome this problem, physiologically relevant intestinal models are developed with a 3D hollow tubular structure using 3D bioprinting strategy. A tissue-specific biomaterial, colon-derived decellularized extracellular matrix (Colon dECM) is developed and it provides significant maturation-guiding potential to human intestinal cells. To fabricate a perfusable tubular model, a simultaneous printing process of multiple materials through concentrically assembled nozzles is developed and a light-activated Colon dECM bioink is employed by supplementing with ruthenium/sodium persulfate as a photoinitiator. The bioprinted intestinal tissue models show spontaneous 3D morphogenesis of the human intestinal epithelium without any external stimuli. In consequence, the printed cells form multicellular aggregates and cysts and then differentiate into several types of enterocytes, building junctional networks. This system can serve as a platform to evaluate the effects of potential drug-induced toxicity on the human intestinal tissue and create a coculture model with commensal microbes and immune cells for future therapeutics.

Abstract PO-113: The prolyl isomerase PIN1 plays a critical role in fibroblast differentiation states to support pancreatic cancer

Abstract PIN1 is a phosphorylation-directed prolyl isomerase that alters the conformation and, therefore, the function of many proteins. PIN1 overexpression in cancer contributes to cancer cell-intrinsic phenotypes including cellular proliferation and migration. While its pro-tumor functions have generated interest in therapeutic targeting of PIN1 for cancer treatment, the effects of PIN1 inhibition on tumor-associated stromal phenotypes have not yet been studied. We assessed pancreatic cancer xenografts and genetically engineered p48-Cre; LSL-KrasG12D; p53R172H (KPC) mice that were treated with small molecule PIN1 inhibitors or crossed into a full body PIN1 knockout (Pin1−/−), and found that PIN1 inhibition or loss decreased tumor growth and extended overall survival. To interrogate a direct role for PIN1 in the stroma, we orthotopically injected a KPC cell line into syngeneic Pin1+/+ or Pin1−/− hosts and found dramatic reduction of tumor cell growth in Pin1−/− hosts. Further analysis of the Pin1−/− tumor microenvironment revealed decreased expression of alpha-SMA, a marker of myofibroblastic cancer associated fibroblasts (myCAFs), as well as decreased ECM deposition and/or organization. Pancreatic stellate cells (PSCs) activated in the tumor microenvironment play a major role in the deposition of ECM and secrete growth factors to support tumor cell proliferation and survival. We, therefore, interrogated the role of PIN1 in PSCs. We found that loss of PIN1 in PSCs inhibits TGF-beta-induced stellate cell activation into a myofibroblast phenotype. Single cell ATAC-seq analysis demonstrated that a subset of TGF-beta responsive changes to chromatin accessibility are impaired in the absence of PIN1, and suggests that specific transcription factor families may play a role in the PIN1-dependent response to TGF-beta. Further analysis of PSCs or CAFs with PIN1 loss indicated that, at baseline, these cells express gene programs consistent with the recently described antigen presenting CAFs (apCAFs). Finally, in addition to changes in cellular state and plasticity, we found that loss of PIN1 alters PSC secretion of paracrine factors that support oncogenic phenotypes. For example, PSCs with loss of PIN1 have reduced expression of HGF and increased expression of VEGF, resulting in altered cancer cell and vascular phenotypes. This work establishes a role for PIN1 in regulating fibroblast function and suggests that targeting PIN1 in cancer will have a broad anti-tumor effect. Our ongoing work continues to use 2D co-cultures, heterotypic 3D bioprinted tissues, and in vivo mouse models to interrogate the precise mechanisms by which PIN1 controls fibroblast phenotypes and impact of these changes on tumor phenotypes and outcomes. Citation Format: Ellen M. Langer, Isabel A. English, Vidhi Shah, Kevin MacPherson, Kayleigh M. Kresse, Brittany L. Allen-Petersen, Colin J. Daniel, Mara H. Sherman, Andrew Adey, Rosalie C. Sears. The prolyl isomerase PIN1 plays a critical role in fibroblast differentiation states to support pancreatic cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-113.

Advances and challenges in bioprinting of biological tissues and organs.

Artificial OrgansVolume 45, Issue 12 p. 1441-1445 INVITED REVIEW Advances and challenges in bioprinting of biological tissues and organs Maryam Tavafoghi, orcid.org/0000-0001-5050-5822 Department of Bioengineering, University of California-Los Angeles, Los Angeles, California, USASearch for more papers by this authorAli Khademhosseini, orcid.org/0000-0002-2692-1524 Terasaki Institute for Biomedical Innovation (TIBI), Los Angeles, California, USASearch for more papers by this authorSamad Ahadian, Corresponding Author sahadian@terasaki.org orcid.org/0000-0002-6784-5716 Terasaki Institute for Biomedical Innovation (TIBI), Los Angeles, California, USA Correspondence Samad Ahadian, Terasaki Institute for Biomedical Innovation (TIBI), Los Angeles, CA 90024, USA. Email: sahadian@terasaki.orgSearch for more papers by this author Maryam Tavafoghi, orcid.org/0000-0001-5050-5822 Department of Bioengineering, University of California-Los Angeles, Los Angeles, California, USASearch for more papers by this authorAli Khademhosseini, orcid.org/0000-0002-2692-1524 Terasaki Institute for Biomedical Innovation (TIBI), Los Angeles, California, USASearch for more papers by this authorSamad Ahadian, Corresponding Author sahadian@terasaki.org orcid.org/0000-0002-6784-5716 Terasaki Institute for Biomedical Innovation (TIBI), Los Angeles, California, USA Correspondence Samad Ahadian, Terasaki Institute for Biomedical Innovation (TIBI), Los Angeles, CA 90024, USA. Email: sahadian@terasaki.orgSearch for more papers by this author First published: 22 September 2021 https://doi.org/10.1111/aor.14069Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat Volume45, Issue12December 2021Pages 1441-1445 RelatedInformation

3D Bioprinting of Engineered Tissue Flaps with Hierarchical Vessel Networks (VesselNet) for Direct Host-To-Implant Perfusion.

Engineering hierarchical vasculatures is critical for creating implantable functional thick tissues. Current approaches focus on fabricating mesoscale vessels for implantation or hierarchical microvascular in vitro models, but a combined approach is yet to be achieved to create engineered tissue flaps. Here, millimetric vessel-like scaffolds and 3D bioprinted vascularized tissues interconnect, creating fully engineered hierarchical vascular constructs for implantation. Endothelial and support cells spontaneously form microvascular networks in bioprinted tissues using a human collagen bioink. Sacrificial molds are used to create polymeric vessel-like scaffolds and endothelial cells seeded in their lumen form native-like endothelia. Assembling endothelialized scaffolds within vascularizing hydrogels incites the bioprinted vasculature and endothelium to cooperatively create vessels, enabling tissue perfusion through the scaffold lumen. Using a cuffing microsurgery approach, the engineered tissue is directly anastomosed with a rat femoral artery, promoting a rich host vasculature within the implanted tissue. After two weeks in vivo, contrast microcomputer tomography imaging and lectin perfusion of explanted engineered tissues verify the host ingrowth vasculature's functionality. Furthermore, the hierarchical vessel network (VesselNet) supports in vitro functionality of cardiomyocytes. Finally, the proposed approach is expanded to mimic complex structures with native-like millimetric vessels. This work presents a novel strategy aiming to create fully-engineered patient-specific thick tissue flaps.

Transplantation of 3D bio-printed cardiac mesh improves cardiac function and vessel formation via ANGPT1/Tie2 pathway in rats with acute myocardial infarction

A novel tissue engineering strategy using 3D bio-print technology has become a promising therapeutic method for acute myocardial infarction (AMI) in an animal model. However, the application of 3D bio-printed tissue remains limited due to poor graft survival. Therefore, it is a scientific priority to enhance graft survival by precisely adjusting the 3D environment of encapsulated cells. In this study, novel transplantable 3D cardiac mesh (cMesh) tissue with a porous mesh structure was presented using human cardiomyocytes, human cardiac fibroblasts, and gelatin-methacryloyl–collagen hydrogel. Cardiomyocytes and cardiac fibroblasts were well spreaded. The cardiomyocytes were connected with a gap junction channel in bio-printed cMesh and a 3D cardiac patch with an aggregated structure. Porous cMesh demonstrated structural advantages by increased phosphorylation of mTOR, AKT, and ERK signals associated with cell survival. Transplanted cMesh in rats with AMI improved long-term graft survival, vessel formation, and stabilization, reduced fibrosis, increased left ventricle thickness, and enhanced cardiac function. Our results suggest that porous cMesh provides structural advantages and a positive therapeutic effect in an AMI animal model.

Current state and future of 3D bioprinted models for cardiovascular research and drug development.

In the last decade, 3D bioprinting technology has emerged as an innovative tissue engineering approach for regenerative medicine and drug development. This article aims at providing an overview about the most commonly used bioengineered tissues, focusing on 3D bioprinted cardiac cells and how they have been utilized for drug discovery and development. The review describes that, while this field is still developing, cardiovascular research may benefit from laboratory-engineered heart tissues built of specific cell types with precise 3D architecture mimicking the native cardiac microenvironment. It also describes the role played by regulatory agencies and potential commercialization pathways for direct translation from the bench to the bedside of studies using 3D bioprinted cardiac tissues.