A 3D aligned microfibrous myocardial tissue construct cultured under transient perfusion

Lipase-Catalyzed Poly(glycerol-1,8-octanediol-sebacate): Biomaterial Engineering by Combining Compositional and Crosslinking Variables

This study examined poly(glycerol-1,8-octanediol-sebacate) (PGOS) copolymers with low-level substitution of O (1,8-octanediol) for G (glycerol) units (G/O ratios 0.5:0.5, 0.66:0.33, 0.75:0.25, 0.8:0.2, and 0.91:0.09) prepared in bulk by immobilized Candida antarctica Lipase B (N435) catalysis. The central question explored was the extent that exchanging less than half of poly(glycerol sebacate) (PGS) glycerol units with 1,8-octanediol can be used as a strategy to fine-tune biomaterial properties. Synthesized copolymers having G/O ratios of 0.66:0.33, 0.75:0.25, 0.8:0.2, and 0.91:0.09 have similar molecular weights, where M_w varied from 52,800 to 63,800 g/mol, M_n varied from 5100 to 6450 g/mol, and Đ_M (molecular mass dispersity, M_w/M_n) values were also similar (8.4-11.4). All of the copolymers were branched, and dendritic glycerol units reached 11% for PGOS-0.91:0.09:1.0. Analysis of DSC second heating scans revealed that copolymers with higher 1,8-octanediol contents have relatively higher T_m and ΔH_f values. Over the copolymer compositional range studied herein, T_m and ΔH_f values varied from 5.3 to 21.1 °C and 8.0 to 23.1 J/g, respectively. Stress-strain curves of PGOS copolymers cured at 140 °C for 48 h exhibited either a unimodal, bimodal, or trimodal response to tensile loading. Varying G/O from 10:1 to 2:1 resulted in significant increases in the peak stress (0.26-4.01 MPa), preyield modulus (0.65-62.59 MPa), failure to strain (64-110%), and failure toughness (0.1-0.56 MPa). This demonstrates that altering the G/O ratio over a narrow compositional range provides biomaterials with widely different yet tunable mechanical properties. Further investigation of PGOS-0.75:0.25:1.0 films revealed that varying the cure conditions from 120 to 160 °C for periods of 24-72 h provides access to biomaterials with a failure strain range from 15 to 224% and Young's modulus from 1.17 to 10.85 MPa. Hence, using the dual variables of compositional variation and changes in cure conditions provides an exciting platform for PGS analogues to optimize material-tissue interactions. Increased contents of 1,8-octanediol slowed in vitro degradation. Slowed degradation of PGOS relative to PGS will be valuable for use in slower healing wounds.

Wharton's Jelly-Mesenchymal Stem Cell-Engineered Conduit for Pulmonary Artery Reconstruction in Growing Piglets

Surgical treatment of congenital heart defects affecting the right ventricular outflow tract often requires complex reconstruction and multiple reoperations. With a randomized controlled trial, we compared a novel tissue-engineered small intestine submucosa-based graft for pulmonary artery reconstruction (seeded with mesenchymal stem cells derived from Wharton's Jelly) with conventional small intestine submucosa in growing piglets. Six months after implantation, seeded grafts showed integration with host tissues at cellular level and exhibited growth potential on transthoracic echocardiography and cardiovascular magnetic resonance. Our seeded graft is a promising biomaterial for pulmonary artery reconstruction in pediatric patients with right ventricular outflow tract abnormalities.

Polymeric Nanocomposite Structures Based on Functionalized Graphene with Tunable Properties for Nervous Tissue Replacement

Electroconductive scaffolds can be a promising approach to repair conductive tissues when natural healing fails. Recently, nerve tissue engineering constructs have been widely investigated due to the challenges in creating a structure with optimized physiochemical and mechanical properties close to the native tissue. The goal of the current study was to fabricate graphene-containing polycaprolactone/gelatin/polypyrrole (PCL/gelatin/PPy) and polycaprolactone/polyglycerol-sebacate/polypyrrole (PCL/PGS/PPy) with intrinsic electrical properties through an electrospinning process. The effect of graphene on the properties of PCL/gelatin/PPy and PCL/PGS/PPy were investigated. Results demonstrated that graphene incorporation remarkably modulated the physical and mechanical properties of the scaffolds such that the electrical conductivity increased from 0.1 to 3.9 ± 0.3 S m^-1 (from 0 to 3 wt % graphene) and toughness was found to be 76 MPa (PCL/gelatin/PPy 3 wt % graphene) and 143.4 MPa (PCL/PGS/PPy 3 wt % graphene). Also, the elastic moduli of the scaffolds with 0, 1, and 2 wt % graphene were reported as 210, 300, and 340 kPa in the PCL/gelatin/PPy system and 72, 85, and 92 kPa for the PCL/PGS/PPy system. A cell viability study demonstrated the noncytotoxic nature of the resultant scaffolds. The sum of the results presented in this study suggests that both PCL/gelatin/PPy/graphene and PCL/PGS/PPy/graphene compositions could be promising biomaterials for a range of conductive tissue replacement or regeneration applications.

Tissue engineering techniques for iPSC derived three-dimensional cardiac constructs

Recent developments in applied developmental physiology have provided well-defined methodologies for producing human stem cell derived cardiomyocytes. Cardiomyocytes produced in this way have become commonplace as cardiac physiology research models. This accessibility has also allowed for the development of tissue engineered human heart constructs for drug screening, surgical intervention, and investigating cardiac pathogenesis. However, cardiac tissue engineering is an interdisciplinary field that involves complex engineering and physiological concepts, which limits its accessibility. This review provides a readable, broad reaching, and thorough discussion of major factors to consider for the development of cardiovascular tissues from stem cell derived cardiomyocytes. This review will examine important considerations in undertaking a cardiovascular tissue engineering project, and will present, interpret, and summarize some of the recent advancements in this field. This includes reviewing different forms of tissue engineered constructs, a discussion on cardiomyocyte sources, and an in-depth discussion of the fabrication and maturation procedures for tissue engineered heart constructs.

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.

Wharton's Jelly-Mesenchymal Stem Cell-Engineered Conduit for Pediatric Translation in Heart Defect

The materials available for the right ventricular outflow tract (RVOT) reconstruction in patients with tetralogy of fallot (TOF)/pulmonary atresia come with the severe limitation of long-term degeneration and lack of growth potential, causing right ventricular dysfunction, aneurysm formation, and arrhythmias, thus necessitating several high-risk reoperations throughout patients' lives. In this study, we evaluated the capacity of mesenchymal stem cells (MSCs) derived from the Wharton's Jelly (WJ-MSCs), the gelatinous inner portion of the umbilical cord, to grow and recellularize an extracellular matrix (ECM) graft in our optimized xeno-free, good manufacturing practice-compliant culture system. WJ-MSCs were phenotypically and functionally characterized by flow cytometry and multilineage differentiation capacity, respectively. The typical MSC immunophenotype and functional characteristics were retained in our xeno-free culture system, as well as the capacity to grow and engraft onto a naturally occurring scaffold. WJ-MSCs, from both human and swine source, showed excellent capacity to recellularize ECM graft producing a living cell-seeded construct. In addition, we have provided an in vivo proof of concept of feasibility of the cellularized conduit, engineered with swine WJ-MSCs, to be used in a novel porcine model of main pulmonary artery reconstruction, where it showed good integration within the host tissue. Our study indicates that the addition of WJ-MSCs to the ECM scaffold can upgrade the material, converting it into a living tissue, with the potential to grow, repair, and remodel the RVOT. These results could potentially represent a paradigm shift in pediatric cardiac intervention toward new modalities for effective and personalized surgical restoration of pulmonary artery and RVOT function in TOF/pulmonary atresia patients. Impact Statement The materials available for pulmonary artery reconstruction in pediatric patients with Congenital Heart Defect come with the limitation of long-term degeneration and lack of growth, thus necessitating several reoperations. Here, we describe a novel approach combining perinatal stem cells and naturally occurring scaffold to create a living tissue engineered conduit that showed good growth potential in a pulmonary artery reconstruction porcine model. We envision this approach is of great interest and relevance in tissue engineering field applied to cardiovascular regenerative medicine, as it may open up new avenues for correction of congenital cardiac defects, with remarkable medical and social benefits.

Identify the role of Human Wharton's Jelly Mesenchymal Stem Cells in repairing injured uterine of rat

AIM

Maternal complications caused by the cesarean delivery inhibit the capability of preserving the uterus and subsequent fertility. However, successful restoration of the incisional scar continuously still remains a challenge. This work was to evaluate the repairing effect of Human Wharton's Jelly Mesenchymal Stem Cells (hWJ-MSC) on incisional scar of the uterine.

METHODS

Eighteen rats were randomly assigned into two groups and nine for each: one group injected with hWJ-MSC in phosphate buffer saline (PBS) and the other injected with PBS for comparison.

RESULTS

With hWJ-MSC in PBS injected, the uterine endometrium and myometrium with full-thickness injury were restored and the functionality was greatly improved in comparison with the group only with PBS injected.

CONCLUSION

The hWJ-MSC can repair the injured uterine effectively by promoting the uterine endometrium and myometrium cells proliferation and according to the chi-square analysis the pregnancy is improved.

Advanced 3D Cell Culture Techniques in Micro-Bioreactors, Part II: Systems and Applications

In this second part of our systematic review on the research area of 3D cell culture in micro-bioreactors we give a detailed description of the published work with regard to the existing micro-bioreactor types and their applications, and highlight important results gathered with the respective systems. As an interesting detail, we found that micro-bioreactors have already been used in SARS-CoV research prior to the SARS-CoV2 pandemic. As our literature research revealed a variety of 3D cell culture configurations in the examined bioreactor systems, we defined in review part one “complexity levels” by means of the corresponding 3D cell culture techniques applied in the systems. The definition of the complexity is thereby based on the knowledge that the spatial distribution of cell-extracellular matrix interactions and the spatial distribution of homologous and heterologous cell–cell contacts play an important role in modulating cell functions. Because at least one of these parameters can be assigned to the 3D cell culture techniques discussed in the present review, we structured the studies according to the complexity levels applied in the MBR systems.

Advanced 3D Cell Culture Techniques in Micro-Bioreactors, Part I: A Systematic Analysis of the Literature Published between 2000 and 2020

Bioreactors have proven useful for a vast amount of applications. Besides classical large-scale bioreactors and fermenters for prokaryotic and eukaryotic organisms, micro-bioreactors, as specialized bioreactor systems, have become an invaluable tool for mammalian 3D cell cultures. In this systematic review we analyze the literature in the field of eukaryotic 3D cell culture in micro-bioreactors within the last 20 years. For this, we define complexity levels with regard to the cellular 3D microenvironment concerning cell–matrix-contact, cell–cell-contact and the number of different cell types present at the same time. Moreover, we examine the data with regard to the micro-bioreactor design including mode of cell stimulation/nutrient supply and materials used for the micro-bioreactors, the corresponding 3D cell culture techniques and the related cellular microenvironment, the cell types and in vitro models used. As a data source we used the National Library of Medicine and analyzed the studies published from 2000 to 2020.

Human Cell Modeling for Cardiovascular Diseases

The availability of appropriate and reliable in vitro cell models recapitulating human cardiovascular diseases has been the aim of numerous researchers, in order to retrace pathologic phenotypes, elucidate molecular mechanisms, and discover therapies using simple and reproducible techniques. In the past years, several human cell types have been utilized for these goals, including heterologous systems, cardiovascular and non-cardiovascular primary cells, and embryonic stem cells. The introduction of induced pluripotent stem cells and their differentiation potential brought new prospects for large-scale cardiovascular experiments, bypassing ethical concerns of embryonic stem cells and providing an advanced tool for disease modeling, diagnosis, and therapy. Each model has its advantages and disadvantages in terms of accessibility, maintenance, throughput, physiological relevance, recapitulation of the disease. A higher level of complexity in diseases modeling has been achieved with multicellular co-cultures. Furthermore, the important progresses reached by bioengineering during the last years, together with the opportunities given by pluripotent stem cells, have allowed the generation of increasingly advanced in vitro three-dimensional tissue-like constructs mimicking in vivo physiology. This review provides an overview of the main cell models used in cardiovascular research, highlighting the pros and cons of each, and describing examples of practical applications in disease modeling.

ECM Mimetic Electrospun Porous Poly (L-lactic acid) (PLLA) Scaffolds as Potential Substrates for Cardiac Tissue Engineering

Cardiac tissue engineering (CTE) aims to generate potential scaffolds to mimic extracellular matrix (ECM) for recreating the injured myocardium. Highly porous scaffolds with properties that aid cell adhesion, migration and proliferation are critical in CTE. In this study, electrospun porous poly (l-lactic acid) (PLLA) porous scaffolds were fabricated and modified with different ECM derived proteins such as collagen, gelatin, fibronectin and poly-L-lysine. Subsequently, adult human cardiac fibroblasts (AHCF) were cultured on the protein modified and unmodified fibers to study the cell behavior and guidance. Further, the cytotoxicity and reactive oxygen species (ROS) assessments of the respective fibers were performed to determine their biocompatibility. Excellent cell adhesion and proliferation of the cardiac fibroblasts was observed on the PLLA porous fibers regardless of the surface modifications. The metabolic rate of cells was on par with the conventional cell culture ware while the proliferation rate surpassed the latter by nearly two-folds. Proteome profiling revealed that apart from being an anchorage platform for cells, the surface topography has modulated significant expression of the cellular proteome with many crucial proteins responsible for cardiac fibroblast growth and proliferation.

A review: Nanofibrous scaffold in possible prevention and treatment of coronary artery disease

Nanofibrous scaffolds have potential to improve coronary stent applications by promoting endothelial recovery on the stent surface and aids regeneration of cardiac tissues. Presently, scaffolds fabricated via electro-spinning are been widely used because of their ability to bio-mimic the precise anatomical structure of the protein fibers. Properties like convenience to spin on several components and functionalization with several bioactive molecules have signify the use of nanofibrous scaffolds for tissue engineering. This review highlights some recent applications of electrospun nanofibrous scaffolds in the treatment and management of cardiac arterial diseases and engineering new cardiac tissues.

Chitosan/Calcium Silicate Cardiac Patch Stimulates Cardiomyocyte Activity and Myocardial Performance after Infarction by Synergistic Effect of Bioactive Ions and Aligned Nanostructure

Cardiac tissue engineering (CTE) remains a great challenge to construct a cell-inductive scaffold that has positive effects on cardiac cell behaviors and cardiac tissue repair. In this study, we for the first time demonstrated that Si ions evidently stimulated the expression of cardiac-specific genes and proliferation of neonatal rat cardiomyocytes (NRCMs) at concentration ranges of 0.13-10.78 ppm. Accordingly, the optimized concentrations of calcium silicate (CS) were incorporated into the controllable aligned chitosan electrospun nanofibers, constructing the composite cardiac patch scaffolds. These scaffolds showed synergistic effect of bioactive chemical and structural signals on both cardiomyocytes and endothelial cells with aligned cell morphology and enhanced viability and function characterized by upregulated expressions of cardiac and angiogenic specific markers, improved myofilament structure, and better Ca²⁺ transients of NRCMs as compared to the scaffolds free of CS component or with disordered structures. The in vivo studies further demonstrated that the NRCM-seeded aligned CS/chitosan cardiac patch evidently improved cardiac function via limiting the scar area and promoting angiogenesis in postmyocardial infarction rats. Conclusively, our study highlights the potential application of bioactive ions and nanostructured biomaterials in CTE, and the CS/chitosan composite cardiac patch may be a promising scaffold for repair of infarcted myocardium.

Microfibrous scaffolds from poly(l-lactide-co-ε-caprolactone) blended with xeno-free collagen/hyaluronic acid for improvement of vascularization in tissue engineering applications

Success of 3D tissue substitutes in clinical applications depends on the presence of vascular networks in their structure. Accordingly, research in tissue engineering is focused on the stimulation of angiogenesis or generation of a vascular network in the scaffolds prior to implantation. A novel, xeno-free, collagen/hyaluronic acid-based poly(l-lactide-co-ε-caprolactone) (PLC/COL/HA) (20/9.5/0.5 w/w/w) microfibrous scaffold was produced by electrospinning. Collagen types I and III, and hyaluronic acid were isolated from human umbilical cords and blended with the GMP grade PLC. When compared with PLC scaffolds the PLC/COL/HA had higher water uptake capacity (103% vs 66%) which may have contributed to the decrease in its Young's Modulus (from 1.31 to 0.89 MPa). The PLC/COL/HA better supported adipose tissue-derived mesenchymal stem cell (AT MSC) adhesion; within 24 h the cell number on the PLC/COL/HA scaffolds was 3 fold higher. Co-culture of human umbilical vein endothelial cells and AT MSCs induced capillary formation on both scaffold types, but the PLC/COL/HA led to formation of interconnected vessels whose total length was 1.6 fold of the total vessel length on PLC. Clinical use of this scaffold would eliminate the immune response triggered by xenogeneic collagen and transmission of animal-borne diseases while promoting a better vascular network formation.

Elastic materials for tissue engineering applications: Natural, synthetic, and hybrid polymers

Elastin and collagen are the two main components of elastic tissues and provide the tissue with elasticity and mechanical strength, respectively. Whereas collagen is adequately produced in vitro, production of elastin in tissue-engineered constructs is often inadequate when engineering elastic tissues. Therefore, elasticity has to be artificially introduced into tissue-engineered scaffolds. The elasticity of scaffold materials can be attributed to either natural sources, when native elastin or recombinant techniques are used to provide natural polymers, or synthetic sources, when polymers are synthesized. While synthetic elastomers often lack the biocompatibility needed for tissue engineering applications, the production of natural materials in adequate amounts or with proper mechanical strength remains a challenge. However, combining natural and synthetic materials to create hybrid components could overcome these issues. This review explains the synthesis, mechanical properties, and structure of native elastin as well as the theories on how this extracellular matrix component provides elasticity in vivo. Furthermore, current methods, ranging from proteins and synthetic polymers to hybrid structures that are being investigated for providing elasticity to tissue engineering constructs, are comprehensively discussed.

STATEMENT OF SIGNIFICANCE

Tissue engineered scaffolds are being developed as treatment options for malfunctioning tissues throughout the body. It is essential that the scaffold is a close mimic of the native tissue with regards to both mechanical and biological functionalities. Therefore, the production of elastic scaffolds is of key importance to fabricate tissue engineered scaffolds of the elastic tissues such as heart valves and blood vessels. Combining naturally derived and synthetic materials to reach this goal proves to be an interesting area where a highly tunable material that unites mechanical and biological functionalities can be obtained.

A tissue-engineered scale model of the heart ventricle

Laboratory studies of the heart use cell and tissue cultures to dissect heart function yet rely on animal models to measure pressure and volume dynamics. Here, we report tissue-engineered scale models of the human left ventricle, made of nanofibrous scaffolds that promote native-like anisotropic myocardial tissue genesis and chamber-level contractile function. Incorporating neonatal rat ventricular myocytes or cardiomyocytes derived from human induced pluripotent stem cells, the tissue-engineered ventricles have a diastolic chamber volume of ~500 μL (comparable to that of the native rat ventricle and approximately 1/250 the size of the human ventricle), and ejection fractions and contractile work 50–250 times smaller and 10⁴–10⁸ times smaller than the corresponding values for rodent and human ventricles, respectively. We also measured tissue coverage and alignment, calcium-transient propagation and pressure/volume loops in the presence or absence of test compounds. Moreover, we describe an instrumented bioreactor with ventricular-assist capabilities, and provide a proof-of-concept disease model of structural arrhythmia. The model ventricles can be evaluated with the same assays used in animal models and in clinical settings.

A Single-Step Self-Assembly Approach for the Fabrication of Aligned and Multilayered Three-Dimensional Tissue Constructs Using Multidomain Peptide Hydrogel

Hydrogels are homogenous materials that are limited in their ability to form oriented multilayered architecture in three-dimensional (3D) tissue constructs. Current techniques have led to advancements in this area. Such techniques often require extra devices and/or involve complex processes that are inaccessible to many laboratories. Here is described a one-step methodology that permits reliable alignment of cells into multiple layers using a self-assembling multidomain peptide (MDP) hydrogels. We characterized the structural features, viability, and molecular properties of dental pulp cells fabricated with MDP and demonstrated that manipulation of the layering of cells in the scaffolds was achieved by decreasing the weight by volume percentage (w/v%) of MDP contained within the scaffold. This approach allows cells to remodel their environment and enhanced various gene expression profiles, such as cell proliferation, angiogenesis, and extracellular matrix (ECM) remodeling-related genes. We further validated our approach for constructing various architectural configurations of tissues by fabricating cells into stratified multilayered and tubular structures. Our methodology provides a simple, rapid way to generate 3D tissue constructs with multilayered architectures. This method shows great potential to mimic in vivo microenvironments for cells and may be of benefit in modeling more complex tissues in the field of regenerative medicine.

Artificial Cardiac Muscle with or without the Use of Scaffolds

During the past several decades, major advances and improvements now promote better treatment options for cardiovascular diseases. However, these diseases still remain the single leading cause of death worldwide. The rapid development of cardiac tissue engineering has provided the opportunity to potentially restore the contractile function and retain the pumping feature of injured hearts. This conception of cardiac tissue engineering can enable researchers to produce autologous and functional biomaterials which represents a promising technique to benefit patients with cardiovascular diseases. Such an approach will ultimately reshape existing heart transplantation protocols. Notable efforts are accelerating the development of cardiac tissue engineering, particularly to create larger tissue with enhanced functionality. Decellularized scaffolds, polymer synthetics fibrous matrix, and natural materials are used to build robust cardiac tissue scaffolds to imitate the morphological and physiological patterns of natural tissue. This ultimately helps cells to implant properly to obtain endogenous biological capacity. However, newer designs such as the hydrogel scaffold-free matrix can increase the applicability of artificial tissue to engineering strategies. In this review, we summarize all the methods to produce artificial cardiac tissue using scaffold and scaffold-free technology, their advantages and disadvantages, and their relevance to clinical practice.

In vitro models of the cardiac microenvironment to study myocyte and non-myocyte crosstalk: bioinspired approaches beyond the polystyrene dish

The heart is a complex pluricellular organ composed of cardiomyocytes and non-myocytes including fibroblasts, endothelial cells and immune cells. Myocytes are responsible for electrical conduction and contractile force generation, while the other cell types are responsible for matrix deposition, vascularization, and injury response. Myocytes and non-myocytes are known to communicate and exert mutual regulatory effects. In concert, they determine the structural, electrical and mechanical characteristics in the healthy and remodelled myocardium. Dynamic crosstalk between myocytes and non-myocytes plays a crucial role in stress/injury-induced hypertrophy and fibrosis development that can ultimately lead to heart failure and arrhythmias. Investigations of heterocellular communication in the myocardium are hampered by the intricate interspersion of the different cell types and the complexity of the tissue architecture. In vitro models have facilitated investigations of cardiac cells in a direct and controllable manner and have provided important functional and mechanistic insights. However, these cultures often lack regulatory input from the other cell types as well as additional topographical, electrical, mechanical and biochemical cues from the cardiac microenvironment that all contribute to modulating cell differentiation, maturation, alignment, function and survival. Advancements in the development of more complex pluricellular physiological platforms that incorporate diverse cues from the myocardial microenvironment are expected to lead to more physiologically relevant cardiac tissue-like in vitro models for mechanistic biological research, disease modelling, therapeutic target identification, drug testing and regeneration.

The Horizon of Materiobiology: A Perspective on Material-Guided Cell Behaviors and Tissue Engineering

Although the biological functions of cell and tissue can be regulated by biochemical factors (e.g., growth factors, hormones), the biophysical effects of materials on the regulation of biological activity are receiving more attention. In this Review, we systematically summarize the recent progress on how biomaterials with controllable properties (e.g., compositional/degradable dynamics, mechanical properties, 2D topography, and 3D geometry) can regulate cell behaviors (e.g., cell adhesion, spreading, proliferation, cell alignment, and the differentiation or self-maintenance of stem cells) and tissue/organ functions. How the biophysical features of materials influence tissue/organ regeneration have been elucidated. Current challenges and a perspective on the development of novel materials that can modulate specific biological functions are discussed. The interdependent relationship between biomaterials and biology leads us to propose the concept of "materiobiology", which is a scientific discipline that studies the biological effects of the properties of biomaterials on biological functions at cell, tissue, organ, and the whole organism levels. This Review highlights that it is more important to develop ECM-mimicking biomaterials having a self-regenerative capacity to stimulate tissue regeneration, instead of attempting to recreate the complexity of living tissues or tissue constructs ex vivo. The principles of materiobiology may benefit the development of novel biomaterials providing combinative bioactive cues to activate the migration of stem cells from endogenous reservoirs (i.e., cell niches), stimulate robust and scalable self-healing mechanisms, and unlock the body's innate powers of regeneration.

Fibers for hearts: A critical review on electrospinning for cardiac tissue engineering

Cardiac cell therapy holds a real promise for improving heart function and especially of the chronically failing myocardium. Embedding cells into 3D biodegradable scaffolds may better preserve cell survival and enhance cell engraftment after transplantation, consequently improving cardiac cell therapy compared with direct intramyocardial injection of isolated cells. The primary objective of a scaffold used in tissue engineering is the recreation of the natural 3D environment most suitable for an adequate tissue growth. An important aspect of this commitment is to mimic the fibrillar structure of the extracellular matrix, which provides essential guidance for cell organization, survival, and function. Recent advances in nanotechnology have significantly improved our capacities to mimic the extracellular matrix. Among them, electrospinning is well known for being easy to process and cost effective. Consequently, it is becoming increasingly popular for biomedical applications and it is most definitely the cutting edge technique to make scaffolds that mimic the extracellular matrix for industrial applications. Here, the desirable physico-chemical properties of the electrospun scaffolds for cardiac therapy are described, and polymers are categorized to natural and synthetic.Moreover, the methods used for improving functionalities by providing cells with the necessary chemical cues and a more in vivo-like environment are reported.

Synthesis of polyester urethane urea and fabrication of elastomeric nanofibrous scaffolds for myocardial regeneration

Fabrication of bioactive scaffolds is one of the most promising strategies to reconstruct the infarcted myocardium. In this study, we synthesized polyester urethane urea (PEUU), further blended it with gelatin and fabricated PEUU/G nanofibrous scaffolds. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC) and X-ray diffraction were used for the characterization of the synthesized PEUU and properties of nanofibrous scaffolds were evaluated using scanning electron microscopy (SEM), ATR-FTIR, contact angle measurement, biodegradation test, tensile strength analysis and dynamic mechanical analysis (DMA). In vitro biocompatibility studies were performed using cardiomyocytes. DMA analysis showed that the scaffolds could be reshaped with cyclic deformations and might remain stable in the frequencies of the physiological activity of the heart. On the whole, our study suggests that aligned PEUU/G 70:30 nanofibrous scaffolds meet the required specifications for cardiac tissue engineering and could be used as a promising construct for myocardial regeneration.

Mesoporous silica nanoparticles in tissue engineering – a perspective

In this review, we summarize the latest developments and give a perspective on future applications of mesoporous silica nanoparticles (MSNs) in regenerative medicine. MSNs constitute a flexible platform for controlled delivery of drugs and imaging agents in tissue engineering and stem cell therapy. We highlight the recent advances in applying MSNs for controlled drug delivery and stem cell tracking. We touch upon novel functions of MSNs in real time imaging of drug release and biological function, and as tools to control the chemical and mechanical environment of stem cells. We discuss the need for novel model systems for studying biofunctionality and biocompatibility of MSNs, and how the interdisciplinary activities within the field will advance biotechnology research.

Fibrous scaffolds for building hearts and heart parts

Extracellular matrix (ECM) structure and biochemistry provide cell-instructive cues that promote and regulate tissue growth, function, and repair. From a structural perspective, the ECM is a scaffold that guides the self-assembly of cells into distinct functional tissues. The ECM promotes the interaction between individual cells and between different cell types, and increases the strength and resilience of the tissue in mechanically dynamic environments. From a biochemical perspective, factors regulating cell-ECM adhesion have been described and diverse aspects of cell-ECM interactions in health and disease continue to be clarified. Natural ECMs therefore provide excellent design rules for tissue engineering scaffolds. The design of regenerative three-dimensional (3D) engineered scaffolds is informed by the target ECM structure, chemistry, and mechanics, to encourage cell infiltration and tissue genesis. This can be achieved using nanofibrous scaffolds composed of polymers that simultaneously recapitulate 3D ECM architecture, high-fidelity nanoscale topography, and bio-activity. Their high porosity, structural anisotropy, and bio-activity present unique advantages for engineering 3D anisotropic tissues. Here, we use the heart as a case study and examine the potential of ECM-inspired nanofibrous scaffolds for cardiac tissue engineering. We asked: Do we know enough to build a heart? To answer this question, we tabulated structural and functional properties of myocardial and valvular tissues for use as design criteria, reviewed nanofiber manufacturing platforms and assessed their capabilities to produce scaffolds that meet our design criteria. Our knowledge of the anatomy and physiology of the heart, as well as our ability to create synthetic ECM scaffolds have advanced to the point that valve replacement with nanofibrous scaffolds may be achieved in the short term, while myocardial repair requires further study in vitro and in vivo.

In vitro cardiac tissue models: Current status and future prospects

Cardiovascular disease is the leading cause of death worldwide. Achieving the next phase of potential treatment strategies and better prognostic tools will require a concerted effort from interdisciplinary fields. Biomaterials-based cardiac tissue models are revolutionizing the area of preclinical research and translational applications. The goal of in vitro cardiac tissue modeling is to create physiological functional models of the human myocardium, which is a difficult task due to the complex structure and function of the human heart. This review describes the advances made in area of in vitro cardiac models using biomaterials and bioinspired platforms. The field has progressed extensively in the past decade, and we envision its applications in the areas of drug screening, disease modeling, and precision medicine.

Fabrication and effect on regulating vSMC phenotype of a biomimetic tunica media scaffold

We constructed a bFGF@TGF-β1 loaded porous film-like PLGA scaffold with dual surface topography of nanofiber and micro-orientation structures for regulating the phenotype of vascular smooth muscle cell (vSMC).

Polyol-based biodegradable polyesters: a short review

Catalyst-free thermal polyesterification has recently emerged as a potential strategy for designing biodegradable thermoset polymers, particularly polyol-based polyesters for biomedical applications. These thermoset polyesters are synthesized through polycondensation of polyol and polyacid without the presence of catalyst or solvents. The mechanical properties, degradation rates, crystallinity, hydrophilicity, and biocompatibility can be controlled by adjusting the monomer feed ratios and curing conditions. These polyesters often degrade via surface erosion that allows the polymers to maintain structural integrity throughout hydrolysis. Additionally, polyol-based polyesters demonstrated good biocompatibility as non-toxic catalysts and/or solvents involved in the reaction, and the monomers used are endogenous to human metabolism which can be resorbed and metabolized in various physiological pathways. This review summarizes the polyol-based biodegradable polyesters that were synthesized by catalyst-free polyesterification.

Cell Sheet-Based Tissue Engineering for Organizing Anisotropic Tissue Constructs Produced Using Microfabricated Thermoresponsive Substrates

In some native tissues, appropriate microstructures, including orientation of the cell/extracellular matrix, provide specific mechanical and biological functions. For example, skeletal muscle is made of oriented myofibers that is responsible for the mechanical function. Native artery and myocardial tissues are organized three-dimensionally by stacking sheet-like tissues of aligned cells. Therefore, to construct any kind of complex tissue, the microstructures of cells such as myotubes, smooth muscle cells, and cardiomyocytes also need to be organized three-dimensionally just as in the native tissues of the body. Cell sheet-based tissue engineering allows the production of scaffold-free engineered tissues through a layer-by-layer construction technique. Recently, using microfabricated thermoresponsive substrates, aligned cells are being harvested as single continuous cell sheets. The cell sheets act as anisotropic tissue units to build three-dimensional tissue constructs with the appropriate anisotropy. This cell sheet-based technology is straightforward and has the potential to engineer a wide variety of complex tissues. In addition, due to the scaffold-free cell-dense environment, the physical and biological cell-cell interactions of these cell sheet constructs exhibit unique cell behaviors. These advantages will provide important clues to enable the production of well-organized tissues that closely mimic the structure and function of native tissues, required for the future of tissue engineering.

[Research process of the preparation of electrostatic spinning of poly-glycerol sebacate and the application in tissue engineering]

Poly-glycerol sebacate (PGS) is a novel biodegradable elastomer, it has been widely applied in the biomedical fields of heart, blood vessel and cartilage owing to its excellent biological performance, mechanical property and degradability. Electrostatic spinning is a preparation method of tissue engineering scaffolds with the characteristics of convenience, processing controllability and cost efficiency. In this paper, the author reviewed the research process of electrostatic spinning preparation and the application in the field of tissue engineering.

Mesoporous silica particle-PLA-PANI hybrid scaffolds for cell-directed intracellular drug delivery and tissue vascularization

Instructive materials are expected to revolutionize stem cell based tissue engineering. As many stem cell cues have adverse effects on normal tissue homeostasis, there is a need to develop bioactive scaffolds which offer locally retained and cell-targeted drug delivery for intracellular release in targeted cell populations. Further, the scaffolds need to support vascularization to promote tissue growth and function. We have developed an electrospun PLA-PANI fiber scaffold, and incorporated mesoporous silica nanoparticles within the scaffold matrix to obtain cell-targeted and localized drug delivery. The isotropy of the scaffold can be tuned to find the optimal morphology for a given application and the scaffold is electroactive to support differentiation of contractile tissues. We demonstrate that there is no premature drug release from particles under physiological conditions over a period of one week and that the drug is released upon internalization of particles by cells within the scaffold. The scaffold is biocompatible, supports muscle stem cell differentiation and cell-seeded scaffolds are vascularized in vivo upon transplantation on the chorioallantoic membrane of chicken embryos. The scaffold is a step towards instructive biomaterials for local control of stem cell differentiation, and tissue formation supported by vascularization and without adverse effects on the homeostasis of adjacent tissues due to diffusion of biological cues.

Electrospun anisotropic architectures and porous structures for tissue engineering

Recent advances in electrospun anisotropic architectures and porous structures, as well as their applications in tissue engineering, are presented.

Electrospun PLGA fibers incorporated with functionalized biomolecules for cardiac tissue engineering

Structural similarity of electrospun fibers (ESFs) to the native extracellular matrix provides great potential for the application of biofunctional ESFs in tissue engineering. This study aimed to synthesize biofunctionalized poly (L-lactide-co-glycolide) (PLGA) ESFs for investigating the potential for cardiac tissue engineering application. We developed a simple but novel strategy to incorporate adhesive peptides in PLGA ESFs. Two adhesive peptides derived from laminin, YIGSR, and RGD, were covalently conjugated to poly-L-lysine, and then mingled with PLGA solution for electrospinning. Peptides were uniformly distributed on the surface and in the interior of ESFs. PLGA ESFs incorporated with YIGSR or RGD or adsorbed with laminin significantly enhanced the adhesion of cardiomyocytes isolated from neonatal rats. Furthermore, the cells were found to adhere better on ESFs compared with flat substrates after 7 days of culture. Immunofluorescent staining of F-actin, vinculin, a-actinin, and N-cadherin indicated that cardiomyocytes adhered and formed striated α-actinin better on the laminin-coated ESFs and the YIGSR-incorporated ESFs compared with the RGD-incorporated ESFs. The expression of α-myosin heavy chain and β-tubulin on the YIGSR-incorporated ESFs was significantly higher compared with the expression level on PLGA and RGD-incorporated samples. Furthermore, the contraction of cardiomyocytes was faster and lasted longer on the laminin-coated ESFs and YIGSR-incorporated ESFs. The results suggest that aligned YIGSR-incorporated PLGA ESFs is a better candidate for the formation of cardiac patches. This study demonstrated the potential of using peptide-incorporated ESFs as designable-scaffold platform for tissue engineering.

Plasma-functionalized electrospun matrix for biograft development and cardiac function stabilization

Cardiac tissue engineering approaches can deliver large numbers of cells to the damaged myocardium and have thus increasingly been considered as a possible curative treatment to counteract the high prevalence of progressive heart failure after myocardial infarction (MI). Optimal scaffold architecture and mechanical and chemical properties, as well as immune- and bio-compatibility, need to be addressed. We demonstrated that radio-frequency plasma surface functionalized electrospun poly(ɛ-caprolactone) (PCL) fibres provide a suitable matrix for bone-marrow-derived mesenchymal stem cell (MSC) cardiac implantation. Using a rat model of chronic MI, we showed that MSC-seeded plasma-coated PCL grafts stabilized cardiac function and attenuated dilatation. Significant relative decreases of 13% of the ejection fraction (EF) and 15% of the fractional shortening (FS) were observed in sham treated animals; respective decreases of 20% and 25% were measured 4 weeks after acellular patch implantation, whereas a steadied function was observed 4 weeks after MSC-patch implantation (relative decreases of 6% for both EF and FS).

Use of umbilical cord and cord blood-derived stem cells for tissue repair and regeneration

INTRODUCTION

Potential use of umbilical cord (UC) is one of the most exciting frontiers in medicine for repairing damaged tissues. UC and cord blood-derived stem cells are the world's largest potential sources of stem cells. UC contains a mixture of stem and progenitor cells at different lineage commitment stages and UC has been verified as a candidate for cell-based therapies and tissue engineering applications due to the capability of these cells for extensive self-renewal and multi-lineage character in differentiation potential.

AREAS COVERED

UC-based repair or regeneration of organs (i.e., heart, nerve, skin, etc.) is a high-priority research worldwide.

EXPERT OPINION

The aim of this review is to summarize the knowledge about UC with main focus on its applications for tissue repair and regeneration.

Characterization of structural, mechanical and nano-mechanical properties of electrospun PGS/PCL fibers

Structural and mechanical properties of aligned PGS/PCL nanofibers for cornea tissue engineering are studied and compared to natural corneal stroma.

Polymeric scaffold aided stem cell therapeutics for cardiac muscle repair and regeneration

The constantly expanding repository of novel polymers and stem cells has opened up new vistas in the field of cardiac tissue engineering. Successful regeneration of the complex cardiac tissue mainly centres on the appropriate scaffold material with topographical features that mimic the native environment. The integration of stem cells on these scaffolds is expected to enhance the regeneration potential. This review elaborates on the interplay of these vital factors in achieving the functional cardiac tissue. The recent advances in polymers, nanocomposites, and stem cells from different sources are highlighted. Special emphasis is laid on the clinical trials involving stem cells and the state-of-the-art materials to obtain a balanced perspective on the translational potential of this strategy.

Mechanostimulation protocols for cardiac tissue engineering

Owing to the inability of self-replacement by a damaged myocardium, alternative strategies to heart transplantation have been explored within the last decades and cardiac tissue engineering/regenerative medicine is among the present challenges in biomedical research. Hopefully, several studies witness the constant extension of the toolbox available to engineer a fully functional, contractile, and robust cardiac tissue using different combinations of cells, template bioscaffolds, and biophysical stimuli obtained by the use of specific bioreactors. Mechanical forces influence the growth and shape of every tissue in our body generating changes in intracellular biochemistry and gene expression. That is why bioreactors play a central role in the task of regenerating a complex tissue such as the myocardium. In the last fifteen years a large number of dynamic culture devices have been developed and many results have been collected. The aim of this brief review is to resume in a single streamlined paper the state of the art in this field.

PGS:Gelatin nanofibrous scaffolds with tunable mechanical and structural properties for engineering cardiac tissues

A significant challenge in cardiac tissue engineering is the development of biomimetic grafts that can potentially promote myocardial repair and regeneration. A number of approaches have used engineered scaffolds to mimic the architecture of the native myocardium tissue and precisely regulate cardiac cell functions. However, previous attempts have not been able to simultaneously recapitulate chemical, mechanical, and structural properties of the myocardial extracellular matrix (ECM). In this study, we utilized an electrospinning approach to fabricate elastomeric biodegradable poly(glycerol sebacate) (PGS):gelatin nanofibrous scaffolds with a wide range of chemical composition, stiffness and anisotropy. Our findings demonstrated that through incorporation of PGS, it is possible to create nanofibrous scaffolds with well-defined anisotropy that mimic the left ventricular myocardium architecture. Furthermore, we studied attachment, proliferation, differentiation and alignment of neonatal rat cardiac fibroblast cells (CFs) as well as protein expression, alignment, and contractile function of cardiomyocyte (CMs) on PGS:gelatin scaffolds with variable amount of PGS. Notably, aligned nanofibrous scaffold, consisting of 33 wt. % PGS, induced optimal synchronous contractions of CMs while significantly enhanced cellular alignment. Overall, our study suggests that the aligned nanofibrous PGS:gelatin scaffold support cardiac cell organization, phenotype and contraction and could potentially be used to develop clinically relevant constructs for cardiac tissue engineering.