Interdisciplinary approaches to advanced cardiovascular tissue engineering: ECM-based biomaterials, 3D bioprinting, and its assessment

Advancements in textile techniques for cardiovascular tissue replacement and repair

In cardiovascular therapeutics, procedures such as heart transplants and coronary artery bypass graft are pivotal. However, an acute shortage of organ donors increases waiting times of patients, which is reflected in negative effects on the outcome for the patient. Post-procedural complications such as thrombotic events and atherosclerotic developments may also have grave clinical implications. To address these challenges, tissue engineering is emerging as a solution, using textile technologies to synthesize biomimetic scaffolds resembling natural tissues. This comprehensive analysis explains methodologies including electrospinning, electrostatic flocking, and advanced textile techniques developed from weaving, knitting, and braiding. These techniques are evaluated in the context of fabricating cardiac patches, vascular graft constructs, stent designs, and state-of-the-art wearable sensors. We also closely examine the interaction of distinct process parameters with the biomechanical and morphological attributes of the resultant scaffolds. The research concludes by combining current findings and recommendations for subsequent investigation.

A critical review on advances and challenges of bioprinted cardiac patches

Myocardial infarction (MI), which causes irreversible myocardium necrosis, affects 0.25 billion people globally and has become one of the most significant epidemics of our time. Over the past few years, bioprinting has moved beyond a concept of simply incorporating cells into biomaterials, to strategically defining the microenvironment (e.g., architecture, biomolecular signalling, mechanical stimuli, etc.) within which the cells are printed. Among the different bioprinting applications, myocardial repair is a field that has seen some of the most significant advances towards the management of the repaired tissue microenvironment. This review critically assesses the most recent biomedical innovations being carried out in cardiac patch bioprinting, with specific considerations given to the biomaterial design parameters, growth factors/cytokines, biomechanical and bioelectrical conditioning, as well as innovative biomaterial-based "4D" bioprinting (3D scaffold structure + temporal morphology changes) of myocardial tissues, immunomodulation and sustained delivery systems used in myocardium bioprinting. Key challenges include the ability to generate large quantities of cardiac cells, achieve high-density capillary networks, establish biomaterial designs that are comparable to native cardiac extracellular matrix, and manage the sophisticated systems needed for combining cardiac tissue microenvironmental cues while simultaneously establishing bioprinting technologies yielding both high-speed and precision. This must be achieved while considering quality assurance towards enabling reproducibility and clinical translation. Moreover, this manuscript thoroughly discussed the current clinical translational hurdles and regulatory issues associated with the post-bioprinting evaluation, storage, delivery and implantation of the bioprinted myocardial patches. Overall, this paper provides insights into how the clinical feasibility and important regulatory concerns may influence the design of the bioink (biomaterials, cell sources), fabrication and post-fabrication processes associated with bioprinting of the cardiac patches. This paper emphasizes that cardiac patch bioprinting requires extensive collaborations from imaging and 3D modelling technical experts, biomaterial scientists, additive manufacturing experts and healthcare professionals. Further, the work can also guide the field of cardiac patch bioprinting moving forward, by shedding light on the potential use of robotics and automation to increase productivity, reduce financial cost, and enable standardization and true commercialization of bioprinted cardiac patches. STATEMENT OF SIGNIFICANCE: The manuscript provides a critical review of important themes currently pursued for heart patch bioprinting, including critical biomaterial design parameters, physiologically-relevant cardiac tissue stimulations, and newly emerging cardiac tissue bioprinting strategies. This review describes the limited number of studies, to date in the literature, that describe systemic approaches to combine multiple design parameters, including capabilities to yield high-density capillary networks, establish biomaterial composite designs similar to native cardiac extracellular matrix, and incorporate cardiac tissue microenvironmental cues, while simultaneously establishing bioprinting technologies that yield high-speed and precision. New tools such as artificial intelligence may provide the analytical power to consider multiple design parameters and identify an optimized work-flow(s) for enabling the clinical translation of bioprinted cardiac patches.

Decellularized Scaffold-Based Artificial Vascular Patch for Porcine Vascular Repair

Vascular transplantation is an effective strategy against cardiovascular diseases (CVD), and artificial vascular patches are of urgent need across the world. In this work, we designed a multifunctional decellularized scaffolds (DCS)-based vascular patch for porcine vascular repair. Ammonium phosphate zwitter-ion (APZI) and poly(vinyl alcohol) (PVA) hydrogel were coated on the surface of DCS to improve the mechanical properties and biocompatibility of an artificial vascular patch. Then a heparin (Hep)-loaded metal-organic framework (MOF) further decorated the artificial vascular patches to inhibit blood coagulation and promote vascular endothelialization. The obtained artificial vascular patch showed suitable mechanical properties, good biocompatibility, and blood compatibility. In addition, the proliferation and adhesion of endothelial progenitor cells (EPCs) on the surface of artificial vascular patch improved a lot when compared with unmodified PVA/DCS. According to the results of B-ultrasound and CT images, the artificial vascular patch could maintain the patency of the implant site after implanting into the pig carotid artery. The current results solidly support that a MOF-Hep/APZI-PVA/DCS vascular patch would be an excellent vascular replacement material.

Biohybrid 3D Printing of a Tissue-Sensor Platform for Wireless, Real-Time, and Continuous Monitoring of Drug-Induced Cardiotoxicity

Drug-induced cardiotoxicity is regarded as a major hurdle in the early stages of drug development. Although there are various methods for preclinical cardiotoxicity tests, they cannot completely predict the cardiotoxic potential of a compound due to the lack of physiological relevance. Recently, 3D engineered heart tissue (EHT) has been used to investigate cardiac muscle functions as well as pharmacological effects by exhibiting physiological auxotonic contractions. However, there is still no adequate platform for continuous monitoring to test acute and chronic pharmacological effects in vitro. Here, a biohybrid 3D printing method for fabricating a tissue-sensor platform, composed of a bipillar-grafted strain gauge sensor and EHT, is first introduced. Two pillars are three-dimensionally printed as grafts onto a strain gauge-embedded substrate to promote the EHT contractility and guide the self-assembly of the EHTs along with the strain gauge. In addition, the integration of a wireless multi-channel electronic system allows for continuous monitoring of the EHT contractile force by the tissue-sensor platform and, ultimately, for the observation of the acute and chronic drug effects of cardiotoxicants. In summary, biohybrid 3D printing technology is expected to be a potential fabrication method to provide a next-generation tissue-sensor platform for an effective drug development process.

Construction of 3D hierarchical tissue platforms for modeling diabetes

Diabetes mellitus (DM) is one of the most serious systemic diseases worldwide, and the majority of DM patients face severe complications. However, many of underlying disease mechanisms related to these complications are difficult to understand with the use of currently available animal models. With the urgent need to fundamentally understand DM pathology, a variety of 3D biomimetic platforms have been generated by the convergence of biofabrication and tissue engineering strategies for the potent drug screening platform of pre-clinical research. Here, we suggest key requirements for the fabrication of physiomimetic tissue models in terms of recapitulating the cellular organization, creating native 3D microenvironmental niches for targeted tissue using biomaterials, and applying biofabrication technologies to implement tissue-specific geometries. We also provide an overview of various in vitro DM models, from a cellular level to complex living systems, which have been developed using various bioengineering approaches. Moreover, we aim to discuss the roadblocks facing in vitro tissue models and end with an outlook for future DM research.

A 3D bioprinted hybrid encapsulation system for delivery of human pluripotent stem cell-derived pancreatic islet-like aggregates

Islet transplantation is a promising treatment for type 1 diabetes. However, treatment failure can result from loss of functional cells associated with cell dispersion, low viability, and severe immune response. To overcome these limitations, various islet encapsulation approaches have been introduced. Among them, macroencapsulation offers the advantages of delivering and retrieving a large volume of islets in one system. In this study, we developed a hybrid encapsulation system composed of a macroporous polymer capsule with stagger-type membrane and assemblable structure, and a nanoporous decellularized extracellular matrix (dECM) hydrogel containing pancreatic islet-like aggregates using 3D bioprinting technique. The outer part (macroporous polymer capsule) was designed to have an interconnected porous architecture, which allows insulin-producingβ-cells encapsulated in the hybrid encapsulation system to maintain their cellular behaviors, including viability, cell proliferation, and insulin-producing function. The inner part (nanoporous dECM hydrogel), composed of the 3D biofabricated pancreatic islet-like aggregates, was simultaneously placed into the macroporous polymer capsule in one step. The developed hybrid encapsulation system exhibited biocompatibilityin vitroandin vivoin terms of M1 macrophage polarization. Furthermore, by controlling the printing parameters, we generated islet-like aggregates, improving cell viability and functionality. Moreover, the 3D bioprinted pancreatic islet-like aggregates exhibited structural maturation and functional enhancement associated with intercellular interaction occurring at theβ-cell edges. In addition, we also investigated the therapeutic potential of a hybrid encapsulation system by integrating human pluripotent stem cell-derived insulin-producing cells, which are promising to overcome the donor shortage problem. In summary, these results demonstrated that the 3D bioprinting approach facilitates the fabrication of a hybrid islet encapsulation system with multiple materials and potentially improves the clinical outcomes by driving structural maturation and functional improvement of cells.

Employing Extracellular Matrix-Based Tissue Engineering Strategies for Age-Dependent Tissue Degenerations

Tissues and organs are not composed of solely cellular components; instead, they converge with an extracellular matrix (ECM). The composition and function of the ECM differ depending on tissue types. The ECM provides a microenvironment that is essential for cellular functionality and regulation. However, during aging, the ECM undergoes significant changes along with the cellular components. The ECM constituents are over- or down-expressed, degraded, and deformed in senescence cells. ECM aging contributes to tissue dysfunction and failure of stem cell maintenance. Aging is the primary risk factor for prevalent diseases, and ECM aging is directly or indirectly correlated to it. Hence, rejuvenation strategies are necessitated to treat various age-associated symptoms. Recent rejuvenation strategies focus on the ECM as the basic biomaterial for regenerative therapies, such as tissue engineering. Modified and decellularized ECMs can be used to substitute aged ECMs and cell niches for culturing engineered tissues. Various tissue engineering approaches, including three-dimensional bioprinting, enable cell delivery and the fabrication of transplantable engineered tissues by employing ECM-based biomaterials.

Handheld bioprinting strategies for in situ wound dressing

Handheld bioprinting has recently attracted considerable attention as a technology to deliver biomaterials and/or cells to injury sites by using freeform, user-instructed deposition approaches, specifically targeted towards in situ wound dressing and healing. In this review, we present a concise introduction of handheld bioprinting, and a thorough discussion on design and manufacture of handheld bioprinters and choice over bioinks. Finally, the advantages, challenges, and prospective of the said technologies are elaborated. It is believed that handheld bioprinting will play an essential role in the field of in situ wound healing mainly due to its excellent portability, user-friendliness, cost-effectiveness, and amenability to various wound needs.

3D bioprinted and integrated platforms for cardiac tissue modeling and drug testing

Recent advances in biofabrication techniques, including 3D bioprinting, have allowed for the fabrication of cardiac models that are similar to the human heart in terms of their structure (e.g., volumetric scale and anatomy) and function (e.g., contractile and electrical properties). The importance of developing techniques for assessing the characteristics of 3D cardiac substitutes in real time without damaging their structures has also been emphasized. In particular, the heart has two primary mechanisms for transporting blood through the body: contractility and an electrical system based on intra and extracellular calcium ion exchange. This review introduces recent trends in 3D bioprinted cardiac tissues and the measurement of their structural, contractile, and electrical properties in real time. Cardiac models have also been regarded as alternatives to animal models as drug-testing platforms. Thus, perspectives on the convergence of 3D bioprinted cardiac tissues and their assessment for use in drug development are also presented.

3D Bioprinting-Based Vascularized Tissue Models Mimicking Tissue-Specific Architecture and Pathophysiology for in vitro Studies

A wide variety of experimental models including 2D cell cultures, model organisms, and 3D in vitro models have been developed to understand pathophysiological phenomena and assess the safety and efficacy of potential therapeutics. In this sense, 3D in vitro models are an intermediate between 2D cell cultures and animal models, as they adequately reproduce 3D microenvironments and human physiology while also being controllable and reproducible. Particularly, recent advances in 3D in vitro biomimicry models, which can produce complex cell structures, shapes, and arrangements, can more similarly reflect in vivo conditions than 2D cell culture. Based on this, 3D bioprinting technology, which enables to place the desired materials in the desired locations, has been introduced to fabricate tissue models with high structural similarity to the native tissues. Therefore, this review discusses the recent developments in this field and the key features of various types of 3D-bioprinted tissues, particularly those associated with blood vessels or highly vascularized organs, such as the heart, liver, and kidney. Moreover, this review also summarizes the current state of the three categories: (1) chemical substance treatment, (2) 3D bioprinting of lesions, and (3) recapitulation of tumor microenvironments (TME) of 3D bioprinting-based disease models according to their disease modeling approach. Finally, we propose the future directions of 3D bioprinting approaches for the creation of more advanced in vitro biomimetic 3D tissues, as well as the translation of 3D bioprinted tissue models to clinical applications.