Cardiovascular 3D bioprinting:A review on cardiac tissue development

Cardiovascular diseases such as myocardial infarction account for millions of worldwide deaths annually. Cardiovascular tissues constitute a highly organized and complex three-dimensional (3D) structure that makes them hard to fabricate in a biomimetic manner by conventional scaffold fabrication methods. 3D bioprinting has been introduced as a novel cell-based method in the last two decades due to its ability to recapitulate cell density, multicellular architecture, physiochemical environment, and vascularization of biological constructs with accurate designs. This review article aims to provide a comprehensive outlook to obtain cardiovascular functional tissues from the engineering of bioinks comprising cells, hydrogels, and biofactors to bioprinting techniques and relevant biophysical stimulations responsible for maturation and tissue-level functions. Also, cardiac tissue 3D bioprinting investigations and further discussion over its challenges and perspectives are highlighted in this review article

Stem cell-based approaches in cardiac tissue engineering: controlling the microenvironment for autologous cells

Cardiovascular disease is one of the leading causes of mortality worldwide. Cardiac tissue engineering strategies focusing on biomaterial scaffolds incorporating cells and growth factors are emerging as highly promising for cardiac repair and regeneration. The use of stem cells within cardiac microengineered tissue constructs present an inherent ability to differentiate into cell types of the human heart. Stem cells derived from various tissues including bone marrow, dental pulp, adipose tissue and umbilical cord can be used for this purpose. Approaches ranging from stem cell injections, stem cell spheroids, cell encapsulation in a suitable hydrogel, use of prefabricated scaffold and bioprinting technology are at the forefront in the field of cardiac tissue engineering. The stem cell microenvironment plays a key role in the maintenance of stemness and/or differentiation into cardiac specific lineages. This review provides a detailed overview of the recent advances in microengineering of autologous stem cell-based tissue engineering platforms for the repair of damaged cardiac tissue. A particular emphasis is given to the roles played by the extracellular matrix (ECM) in regulating the physiological response of stem cells within cardiac tissue engineering platforms

Bioprinting and In Vitro Characterization of an Egg White-Based Cardiac Patch for Myocardial Infarction

Myocardial infarction (MI) or heart attack occurs when the bloodstream to the heart is blocked, which may destroy a part of the heart muscle (or myocardium) and form perdurable scarred tissue. The infarcted myocardial muscle nowadays has no revival treatments, and also transplantation is limited as an option. Tissue engineering has the potential to restore myocardial function after an MI by fabricating tailored tissues for treatment. For tissue engineering, three-dimensional (3D) bioprinting is a fabrication method to create 3D constructs with living cells, which would be impossible by other traditional methods. Although various biomaterials, biologically-derived or synthetic, are available, only a few can be used in 3D bioprinting of cardiovascular tissues due to their mechanical weakness of natural biomaterials and/or limited bioactivity (in terms of promoting cell functions) of synthetic ones. The present study aims to develop a novel biomaterial solution for bioprinting (referred to as bioink) and on this basis, to bioprint cell-laden patches and characterize the patches in vitro for potential use in MI treatment. For this, a new bioink was formulated based on chicken egg white (EW) and sodium alginate (Alg). EW, as a rich source of albumin and well-known for its drug delivery applications, has been strategically combined with Alg, a common printable polysaccharide with a non-thrombogenic nature. EW was utilized to improve bioactivity and cell adhesion sites and sodium alginate was considered as an extrudability enhancer to provide good printability. The following research objectives were pursued: I) develop and rheologically characterize the albumin-based bioink by adding minimal amounts of alginate as a printability enhancer biomaterial; II) characterize the mechanical properties of the 3D printed albumin-based patches by compression testing and monitoring the swelling and degradation behavior; and III) characterize the biological properties of the 3D bioprinted cell-laden albumin-based patch by examining the in vitro cell viability. EW-Alg blends with different alginate concentrations were synthesized by mixing the pasteurized egg white with sodium alginate powder. Then the blends were tested in terms of their rheological behavior and showed a non-Newtonian shear-thinning functioning, i.e. the increase of shear strain led to a decline in viscosity. Moreover, the addition of each 0.5 gram alginate in 100 milliliter egg white significantly consolidated the blend's texture and notably changed its viscosity and handling. Hence, the more alginate was used in the solution. Hence, the more alginate was used in the solution, the higher the blend's viscosity and the required extrusion pressure. Compression elastic moduli of the 3D printed patches from the printable EW-Alg blends (2.0, 2.5, and 3.0% Alg in EW) with the range 20-27 kPa showed the similarity of these constructs mostly to human cadaver limb specimens with 10-38 kPa compressive elastic modulus. Furthermore, swelling measurements performed in phosphate-buffered saline (PBS) showed swelling ratios of more than 1800% for all three concentrations of the EW-Alg blend, representing these 3D printed patches' ability to uptaking ionic fluids from a body-like environment. Also, all of the constructs showed signs of biodegradation within a month. The EW-2.0%Alg blend, which had the highest egg white ratio to alginate and the lowest viscosity, was 3D bioprinted as a cell-laden bioink. The loaded human umbilical vein endothelial cells (HUVECs) survival rate was more than 90% in all of the time points within a week, showing high biocompatibility of the EW-Alg bioink. The present study developed an egg white-based bioink for 3D cardiac patch bioprinting. Fabricated patches exhibited suitable mechanical properties and biocompatibility in vitro, to be potentially used for MI treatment

Engineering and Assessing Cardiac Tissue Complexity

Cardiac tissue engineering is very much in a current focus of regenerative medicine research as it represents a promising strategy for cardiac disease modelling, cardiotoxicity testing and cardiovascular repair. Advances in this field over the last two decades have enabled the generation of human engineered cardiac tissue constructs with progressively increased functional capabilities. However, reproducing tissue-like properties is still a pending issue, as constructs generated to date remain immature relative to native adult heart. Moreover, there is a high degree of heterogeneity in the methodologies used to assess the functionality and cardiac maturation state of engineered cardiac tissue constructs, which further complicates the comparison of constructs generated in different ways. Here, we present an overview of the general approaches developed to generate functional cardiac tissues, discussing the different cell sources, biomaterials, and types of engineering strategies utilized to date. Moreover, we discuss the main functional assays used to evaluate the cardiac maturation state of the constructs, both at the cellular and the tissue levels. We trust that researchers interested in developing engineered cardiac tissue constructs will find the information reviewed here useful. Furthermore, we believe that providing a unified framework for comparison will further the development of human engineered cardiac tissue constructs displaying the specific properties best suited for each particular application

Current challenges in three-dimensional bioprinting heart tissues for cardiac surgery.

SUMMARY:Previous attempts in cardiac bioengineering have failed to provide tissues for cardiac regeneration. Recent advances in 3-dimensional bioprinting technology using prevascularized myocardial microtissues as 'bioink' have provided a promising way forward. This review guides the reader to understand why myocardial tissue engineering is difficult to achieve and how revascularization and contractile function could be restored in 3-dimensional bioprinted heart tissue using patient-derived stem cells

Tissue Engineering and Regenerative Medicine 2019:The Role of Biofabrication-A Year in Review

Despite its relative youth, biofabrication is unceasingly expanding by assimilating the contributions from various disciplinary areas and their technological advances. Those developments have spawned the range of available options to produce structures with complex geometries while accurately manipulating and controlling cell behavior. As it evolves, biofabrication impacts other research fields, allowing the fabrication of tissue models of increased complexity that more closely resemble the dynamics of living tissue. The recent blooming and evolutions in biofabrication have opened new windows and perspectives that could aid the translational struggle in tissue engineering and regenerative medicine (TERM) applications. Based on similar methodologies applied in past years' reviews, we identified the most high-impact publications and reviewed the major concepts, findings, and research outcomes in the context of advancement beyond the state-of-the-art in the field. We first aim to clarify the confusion in terminology and concepts in biofabrication to therefore introduce the striking evolutions in three-dimensional and four-dimensional bioprinting of tissues. We conclude with a short discussion on the future outlooks for innovation that biofabrication could bring to TERM research

Taking It Personally: 3D Bioprinting a Patient-Specific Cardiac Patch for the Treatment of Heart Failure.

Despite a massive global preventative effort, heart failure remains the major cause of death globally. The number of patients requiring a heart transplant, the eventual last treatment option, far outnumbers the available donor hearts, leaving many to deteriorate or die on the transplant waiting list. Treating heart failure by transplanting a 3D bioprinted patient-specific cardiac patch to the infarcted region on the myocardium has been investigated as a potential future treatment. To date, several studies have created cardiac patches using 3D bioprinting; however, testing the concept is still at a pre-clinical stage. A handful of clinical studies have been conducted. However, moving from animal studies to human trials will require an increase in research in this area. This review covers key elements to the design of a patient-specific cardiac patch, divided into general areas of biological design and 3D modelling. It will make recommendations on incorporating anatomical considerations and high-definition motion data into the process of 3D-bioprinting a patient-specific cardiac patch

Transplantation of a 3D Bioprinted Patch in a Murine Model of Myocardial Infarction.

Testing regenerative properties of 3D bioprinted cardiac patches in vivo using murine models of heart failure via permanent left anterior descending (LAD) ligation is a challenging procedure and has a high mortality rate due to its nature. We developed a method to consistently transplant bioprinted patches of cells and hydrogels onto the epicardium of an infarcted mouse heart to test their regenerative properties in a robust and feasible way. First, a deeply anesthetized mouse is carefully intubated and ventilated. Following left lateral thoracotomy (surgical opening of the chest), the exposed LAD is permanently ligated and the bioprinted patch transplanted onto the epicardium. The mouse quickly recovers from the procedure after chest closure. The advantages of this robust and quick approach include a predicted 28-day mortality rate of up to 30% (lower than the 44% reported by other studies using a similar model of permanent LAD ligation in mice). Moreover, the approach described in this protocol is versatile and could be adapted to test bioprinted patches using different cell types or hydrogels where high numbers of animals are needed to optimally power studies. Overall, we present this as an advantageous approach which may change preclinical testing in future studies for the field of cardiac regeneration and tissue engineering

Comparison of Biomaterial-Dependent and -Independent Bioprinting Methods for Cardiovascular Medicine

There is an increasing need of human organs for transplantation, of alternatives to animal experimentation, and of better in vitro tissue models for drug testing. All these needs create unique opportunities for the development of novel and powerful tissue engineering methods, among which the 3D bioprinting is one of the most promising. However, after decades of incubation, ingenuous efforts, early success and much anticipation, biomaterial-dependent 3D bioprinting, although shows steady progress, is slow to deliver the expected clinical results. For this reason, alternative ‘scaffold-free’ 3D bioprinting methods are developing in parallel at an accelerated pace. In this opinion paper we discuss comparatively the two approaches, with specific examples drawn from the cardiovascular field. Moving the emphasis away from competition, we show that the two platforms have similar goals but evolve in complementary technological niches. We conclude that the biomaterial-dependent bioprinting is better suited for tasks requiring faster, larger, anatomically-true, cell-homogenous and matrix-rich constructs, while the scaffold-free biofabrication is more adequate for cell-heterogeneous, matrix-poor, complex and smaller constructs, but requiring longer preparation time

Recent Applications of Three Dimensional Printing in Cardiovascular Medicine

Three dimensional (3D) printing, which consists in the conversion of digital images into a 3D physical model, is a promising and versatile field that, over the last decade, has experienced a rapid development in medicine. Cardiovascular medicine, in particular, is one of the fastest growing area for medical 3D printing. In this review, we firstly describe the major steps and the most common technologies used in the 3D printing process, then we present current applications of 3D printing with relevance to the cardiovascular field. The technology is more frequently used for the creation of anatomical 3D models useful for teaching, training, and procedural planning of complex surgical cases, as well as for facilitating communication with patients and their families. However, the most attractive and novel application of 3D printing in the last years is bioprinting, which holds the great potential to solve the ever-increasing crisis of organ shortage. In this review, we then present some of the 3D bioprinting strategies used for fabricating fully functional cardiovascular tissues, including myocardium, heart tissue patches, and heart valves. The implications of 3D bioprinting in drug discovery, development, and delivery systems are also briefly discussed, in terms of in vitro cardiovascular drug toxicity. Finally, we describe some applications of 3D printing in the development and testing of cardiovascular medical devices, and the current regulatory frameworks that apply to manufacturing and commercialization of 3D printed products