Fabrication of Electrospun Poly (Lactide-co-Glycolide)–Fibrin Multiscale Scaffold for Myocardial Regeneration In Vitro

Electrospinning of biomimetic materials with fibrinogen for effective early-stage wound healing

Electrospun biomimetic materials based on polyester of natural origin poly-3-hudroxybutyrate (PHB) modified with hemin (Hmi) and fibrinogen (Fbg) represent a great interest and are potentially applicable in various fields. Here, we describe formulation of the new fibrous PHB-Fbg and PHB-Hmi-Fbg materials with complex structure for biomedical application. The average diameter of the fibers was 3.5 μm and 1.8 μm respectively. Hmi presence increased porosity from 80 % to 94 %, significantly reduced the number of defects, ensured the formation of a larger number of open pores, and improved mechanical properties. Hmi presence significantly improved the molding properties of the material. Hmi facilitated effective Fbg adsorption on the of the PHB wound-healing material, ensuring uniform localization of the protein on the surface of the fibers. Next, we evaluated cytocompatibility, cell behavior, and open wound healing in mice. The results demonstrated that PHB-Fbg and PHB-Hmi-Fbg electrospun materials had pronounced properties and may be promising for early-stage wound healing - the PHB-Hmi-Fbg sample accelerated wound closure by 35 % on the 3rd day, and PHB-Hmi showed 45 % more effective wound closure on the 15th day.

Bilayer scaffold from PLGA/fibrin electrospun membrane and fibrin hydrogel layer supports wound healingin vivo

Hybrid scaffolds from natural and synthetic polymers have been widely used due to the complementary nature of their physical and biological properties. The aim of the present study, therefore, has been to analyzein vivoa bilayer scaffold of poly(lactide-co-glycolide)/fibrin electrospun membrane and fibrin hydrogel layer on a rat skin model. Fibroblasts were cultivated in the fibrin hydrogel layer and keratinocytes on the electrospun membrane to generate a skin substitute. The scaffolds without and with cells were tested in a full-thickness wound model in Wistar Kyoto rats. The histological results demonstrated that the scaffolds induced granulation tissue growth, collagen deposition and epithelial tissue remodeling. The wound-healing markers showed no difference in scaffolds when compared with the positive control. Activities of antioxidant enzymes were decreased concerning the positive and negative control. The findings suggest that the scaffolds contributed to the granulation tissue formation and the early collagen deposition, maintaining an anti-inflammatory microenvironment.

Sources, Characteristics, and Therapeutic Applications of Mesenchymal Cells in Tissue Engineering

Tissue engineering (TE) is a therapeutic option within regenerative medicine that allows to mimic the original cell environment and functional organization of the cell types necessary for the recovery or regeneration of damaged tissue using cell sources, scaffolds, and bioreactors. Among the cell sources, the utilization of mesenchymal cells (MSCs) has gained great interest because these multipotent cells are capable of differentiating into diverse tissues, in addition to their self-renewal capacity to maintain their cell population, thus representing a therapeutic alternative for those diseases that can only be controlled with palliative treatments. This review aimed to summarize the state of the art of the main sources of MSCs as well as particular characteristics of each subtype and applications of MSCs in TE in seven different areas (neural, osseous, epithelial, cartilage, osteochondral, muscle, and cardiac) with a systemic revision of advances made in the last 10 years. It was observed that bone marrow-derived MSCs are the principal type of MSCs used in TE, and the most commonly employed techniques for MSCs characterization are immunodetection techniques. Moreover, the utilization of natural biomaterials is higher (41.96%) than that of synthetic biomaterials (18.75%) for the construction of the scaffolds in which cells are seeded. Further, this review shows alternatives of MSCs derived from other tissues and diverse strategies that can improve this area of regenerative medicine.

Fabrication of Biomedical Scaffolds Using Biodegradable Polymers

Degradable polymers are used widely in tissue engineering and regenerative medicine. Maturing capabilities in additive manufacturing coupled with advances in orthogonal chemical functionalization methodologies have enabled a rapid evolution of defect-specific form factors and strategies for designing and creating bioactive scaffolds. However, these defect-specific scaffolds, especially when utilizing degradable polymers as the base material, present processing challenges that are distinct and unique from other classes of materials. The goal of this review is to provide a guide for the fabrication of biodegradable polymer-based scaffolds that includes the complete pathway starting from selecting materials, choosing the correct fabrication method, and considering the requirements for tissue specific applications of the scaffold.

Tripolyphosphate-Crosslinked Chitosan/Gelatin Biocomposite Ink for 3D Printing of Uniaxial Scaffolds

Chitosan is a natural polymer widely investigated and used due to its antibacterial activity, mucoadhesive, analgesic, and hemostatic properties. Its biocompatibility makes chitosan a favorable candidate for different applications in tissue engineering (TE), such as skin, bone, and cartilage tissue regeneration. Despite promising results obtained with chitosan 3D scaffolds, significant challenges persist in fabricating hydrogel structures with ordered architectures and biological properties to mimic native tissues. In this work, chitosan has been investigated aiming at designing and fabricating uniaxial scaffolds which can be proposed for the regeneration of anisotropic tissues (i.e., skin, skeletal muscle, myocardium) by 3D printing technology. Chitosan was blended with gelatin to form a polyelectrolyte complex in two different ratios, to improve printability and shape retention. After the optimization of the printing process parameters, different crosslinking conditions were investigated, and the 3D printed samples were characterized. Tripolyphosphate (TPP) was used as crosslinker for chitosan-based scaffolds. For the optimization of the printing temperature, the sol-gel temperature of the chitosan-gelatin blend was determined by rheological measurements and extrusion temperature was set to 20°C (i.e., below sol-gel temperature). The shape fidelity and surface morphology of the 3D printed scaffolds after crosslinking was dependent on crosslinking conditions. Interestingly, mechanical properties of the scaffolds were also significantly affected by the crosslinking conditions, nonetheless the stability of the scaffolds was strongly determined by the content of gelatin in the blend. Lastly, in vitro cytocompatibility test was performed to evaluate the interactions between L929 cells and the 3D printed samples. 2% w/v chitosan and 4% w/v gelatin hydrogel scaffolds crosslinked with 10% TPP, 30 min at 4°C following 30 min at 37°C have shown cytocompatible and stable characteristics, compared to all other tested conditions, showing suitable properties for the regeneration of anisotropic tissues.

Fiber Scaffold Patterning for Mending Hearts: 3D Organization Bringing the Next Step

Heart failure (HF) is a leading cause of death worldwide. The most common conditions that lead to HF are coronary artery disease, myocardial infarction, valve disorders, high blood pressure, and cardiomyopathy. Due to the limited regenerative capacity of the heart, the only curative therapy currently available is heart transplantation. Therefore, there is a great need for the development of novel regenerative strategies to repair the injured myocardium, replace damaged valves, and treat occluded coronary arteries. Recent advances in manufacturing technologies have resulted in the precise fabrication of 3D fiber scaffolds with high architectural control that can support and guide new tissue growth, opening exciting new avenues for repair of the human heart. This review discusses the recent advancements in the novel research field of fiber patterning manufacturing technologies for cardiac tissue engineering (cTE) and to what extent these technologies could meet the requirements of the highly organized and structured cardiac tissues. Additionally, future directions of these novel fiber patterning technologies, designs, and applicability to advance cTE are presented.

Osteoclasts degrade fibrinogen scaffolds and induce mesenchymal stem/stromal osteogenic differentiation

Fibrinogen (Fg) is a pro-inflammatory protein with pro-healing properties. Previous work showed that fibrinogen 3D scaffolds (Fg-3D) promote bone regeneration, but the cellular players were not identified. Osteoclasts are bone resorbing cells that promote bone remodeling in close crosstalk with osteoblasts. Herein, the capacity of osteoclasts differentiated on Fg-3D to degrade the scaffolds and promote osteoblast differentiation was evaluated in vitro. Fg-3D scaffolds were prepared by freeze-drying and osteoclasts were differentiated from primary human peripheral blood monocytes. Results obtained showed osteoclasts expressing the enzymes cathepsin K and tartrate resistant acid phosphatase colonizing Fg-3D scaffolds. Osteoclasts were able to significantly degrade Fg-3D, reducing the scaffold's area, and increasing D-dimer concentration, a Fg degradation product, in their culture media. Osteoclast conditioned media from the first week of differentiation promoted significantly stronger human primary mesenchymal stem/stromal cell (MSC) osteogenic differentiation, evaluated by alkaline phosphatase activity. Moreover, week 1 osteoclast conditioned media promoted earlier MSC osteogenic differentiation, than chemical osteogenesis inductors. TGF-β1 was found increased in osteoclast conditioned media from week 1, when compared to week 3 of differentiation. Taken together, our results suggest that osteoclasts are able to differentiate and degrade Fg-3D, producing factors like TGF-β1 that promote MSC osteogenic differentiation.

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.

Random and aligned electrospun PLGA nanofibers embedded in microfluidic chips for cancer cell isolation and integration with air foam technology for cell release

BACKGROUND

Circulating tumor cells (CTCs) comprise the high metastatic potential population of cancer cells in the blood circulation of humans; they have become the established biomarkers for cancer diagnosis, individualized cancer therapy, and cancer development. Technologies for the isolation and recovery of CTCs can be powerful cancer diagnostic tools for liquid biopsies, allowing the identification of malignancies and guiding cancer treatments for precision medicine.

METHODS

We have used an electrospinning process to prepare poly(lactic-co-glycolic acid) (PLGA) nanofibrous arrays in random or aligned orientations on glass slips. We then fabricated poly(methyl methacrylate) (PMMA)-based microfluidic chips embedding the PLGA nanofiber arrays and modified their surfaces through sequential coating with using biotin-(PEG)7-amine through EDC/NHS activation, streptavidin (SA), and biotinylated epithelial-cell adhesion-molecule antibody (biotin-anti-EpCAM) to achieve highly efficient CTC capture. When combined with an air foam technology that induced a high shear stress and, thereby, nondestructive release of the captured cells from the PLGA surfaces, the proposed device system operated with a high cell recovery rate.

RESULTS

The morphologies and average diameters of the electrospun PLGA nanofibers were characterized using scanning electron microscopy (SEM) and confocal Raman imaging. The surface chemistry of the PLGA nanofibers conjugated with the biotin-(PEG)7-amine was confirmed through time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging. The chip system was studied for the effects of the surface modification density of biotin-(PEG)7-amine, the flow rates, and the diameters of the PLGA nanofibers on the capture efficiency of EpCAM-positive HCT116 cells from the spiked liquid samples. To assess their CTC capture efficiencies in whole blood samples, the aligned and random PLGA nanofiber arrays were tested for their abilities to capture HCT116 cells, providing cancer cell capture efficiencies of 66 and 80%, respectively. With the continuous injection of air foam into the microfluidic devices, the cell release efficiency on the aligned PLGA fibers was 74% (recovery rate: 49%), while it was 90% (recovery rate: 73%) on the random PLGA fibers, from tests of 200 spiked cells in 2 mL of whole blood from healthy individuals. Our study suggests that integrated PMMA microfluidic chips embedding random PLGA nanofiber arrays may be suitable devices for the efficient capture and recovery of CTCs from whole blood samples.

Cardiomyogenic differentiation of human bone marrow-derived mesenchymal stem cell spheroids within electrospun collagen nanofiber mats

Collagen is the major structural protein in myocardium and contributes to tissue strength and integrity, cellular orientation, and cell-cell and cell-matrix interactions. Significant post-myocardial infarction related loss of cardiomyocytes and cardiac tissue, and their subsequent replacement with fibrous scar tissue, negatively impacts endogenous tissue repair and regeneration capabilities. To overcome such limitations, tissue engineers are working toward developing a 3D cardiac patch which not only mimics the structural, functional, and biological hierarchy of the native cardiac tissue, but also could deliver autologous stem cells and encourage their homing and differentiation. In this study, we examined the utility of electrospun, randomly-oriented, type-I collagen nanofiber (dia = 789 ± 162 nm) mats on the cardiomyogenic differentiation of human bone marrow-derived mesenchymal stem cells (BM-MSC) spheroids, in the presence or absence of 10 μM 5-azacytidine (aza). Results showed that these scaffolds are biocompatible and enable time-dependent evolution of early (GATA binding protein 4: GATA4), late (cardiac troponin I: cTnI), and mature (myosin heavy chain: MHC) cardiomyogenic markers, with a simultaneous reduction in CD90 (stemness) expression, independent of aza-treatment. Aza-exposure improved connexin-4 expression and sustained sarcomeric α-actin expression, but provided only transient improvement in cardiac troponin T (cTnT) expression. Cell orientation and alignment significantly improved in these nanofiber scaffolds over time and with aza-exposure. Although further quantitative in vitro and in vivo studies are needed to establish the clinical applicability of such stem-cell laden collagen nanofiber mats as cardiac patches for cardiac tissue regeneration, our results underscore the benefits of 3D milieu provided by electrospun collagen nanofiber mats, aza, and spheroids on the survival, cardiac differentiation and maturation of human BM-MSCs. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 3303-3312, 2018.

Differential and Interactive Effects of Substrate Topography and Chemistry on Human Mesenchymal Stem Cell Gene Expression

Variations in substrate chemistry and the micro-structure were shown to have a significant effect on the biology of human mesenchymal stromal cells (hMSCs). This occurs when differences in the surface properties indirectly modulate pathways within numerous signaling networks that control cell fate. To understand how the surface features affect hMSC gene expression, we performed RNA-sequencing analysis of bone marrow-derived hMSCs cultured on tissue culture-treated polystyrene (TCP) and poly(l-lactide) (PLLA) based substrates of differing topography (Fl: flat and Fs: fibrous) and chemistry (Pr: pristine and Am: aminated). Whilst 80% of gene expression remained similar for cells cultured on test substrates, the analysis of differentially expressed genes (DEGs) revealed that surface topography significantly altered gene expression more than surface chemistry. The Fl and Fs topologies introduced opposite directional alternations in gene expression when compared to TCP control. In addition, the effect of chemical treatment interacted with that of topography in a synergistic manner with the Pr samples promoting more DEGs than Am samples in all gene ontology function groups. These findings not only highlight the significance of the culture surface on regulating the overall gene expression profile but also provide novel insights into cell-material interactions that could help further design the next-generation biomaterials to facilitate hMSC applications. At the same time, further studies are required to investigate whether or not the observations noted correlate with subsequent protein expression and functionality of cells.

3D bioprinting and decellularized ECM-based biomaterials for in vitro CV tissue engineering

Advanced extrusion-based 3D printing strategies allow the rapid fabrication of complex anatomically relevant architectures. Moreover, they have the potential to fabricate 3D-bioprinted cardiac constructs by depositing cardiac cells with appropriate biomaterials. Heart-derived decellularized extracellular matrices containing a complex mixture of various extracellular molecules provide a comprehensive microenvironmental niche similar to native cardiac tissue. Nonetheless, a major concern persists pertaining to insufficient vascularization and mimicking of the complex 3D architectural features, which can be tackled using 3D printing approaches. In this review, we discuss the advantage and application of decellularized extracellular matrix-based hydrogels for the 3D printing of engineered cardiac tissues. We also briefly talk about the integration of electroactive materials within cardiac patches to improve the myocardium's electrophysiological properties.

Three Dimensional Honeycomb Patterned Fibrinogen Based Nanofibers Induce Substantial Osteogenic Response of Mesenchymal Stem Cells

Stem cells therapy offers a viable alternative for treatment of bone disorders to the conventional bone grafting. However clinical therapies are still hindered by the insufficient knowledge on the conditions that maximize stem cells differentiation. Hereby, we introduce a novel 3D honeycomb architecture scaffold that strongly support osteogenic differentiation of human adipose derived mesenchymal stem cells (ADMSCs). The scaffold is based on electrospun hybrid nanofibers consisting of poly (L-lactide ε-caprolactone) and fibrinogen (PLCL/FBG). Classical fibers orientations, random or aligned were also produced and studied for comparison. The overall morphology of ADMSC's generally followed the nanofibers orientation and dimensionality developing regular focal adhesions and direction-dependent actin cytoskeleton bundles. However, there was an initial tendency for cells rounding on honeycomb scaffolds before ADMSCs formed a distinct bridging network. This specific cells organization appeared to have significant impact on the differentiation potential of ADMSCs towards osteogenic lineage, as indicated by the alkaline phosphatase production, calcium deposition and specific genes expression. Collectively, it was observed synergistic effect of nanofibers with honeycomb architecture on the behavior of ADMSCs entering osteogenic path of differentiation which outlines the potential benefits from insertion of such bioinspired geometrical cues within scaffolds for bone tissue engineering.

A review of fibrin and fibrin composites for bone tissue engineering

Tissue engineering has emerged as a new treatment approach for bone repair and regeneration seeking to address limitations associated with current therapies, such as autologous bone grafting. While many bone tissue engineering approaches have traditionally focused on synthetic materials (such as polymers or hydrogels), there has been a lot of excitement surrounding the use of natural materials due to their biologically inspired properties. Fibrin is a natural scaffold formed following tissue injury that initiates hemostasis and provides the initial matrix useful for cell adhesion, migration, proliferation, and differentiation. Fibrin has captured the interest of bone tissue engineers due to its excellent biocompatibility, controllable biodegradability, and ability to deliver cells and biomolecules. Fibrin is particularly appealing because its precursors, fibrinogen, and thrombin, which can be derived from the patient's own blood, enable the fabrication of completely autologous scaffolds. In this article, we highlight the unique properties of fibrin as a scaffolding material to treat bone defects. Moreover, we emphasize its role in bone tissue engineering nanocomposites where approaches further emulate the natural nanostructured features of bone when using fibrin and other nanomaterials. We also review the preparation methods of fibrin glue and then discuss a wide range of fibrin applications in bone tissue engineering. These include the delivery of cells and/or biomolecules to a defect site, distributing cells, and/or growth factors throughout other pre-formed scaffolds and enhancing the physical as well as biological properties of other biomaterials. Thoughts on the future direction of fibrin research for bone tissue engineering are also presented. In the future, the development of fibrin precursors as recombinant proteins will solve problems associated with using multiple or single-donor fibrin glue, and the combination of nanomaterials that allow for the incorporation of biomolecules with fibrin will significantly improve the efficacy of fibrin for numerous bone tissue engineering applications.

Nanomaterial-based bone regeneration

Bone diseases/injuries have been driving an urgent quest for bone substitutes for bone regeneration. Nanoscaled materials with bone-mimicking characteristics may create suitable microenvironments to guide effective bone regeneration. In this review, the natural hierarchical architecture of bone and its regeneration mechanisms are elucidated. Recent progress in the development of nanomaterials which can promote bone regeneration through bone-healing mimicry (e.g., compositional, nanocrystal formation, structural, and growth factor-related mimicking) is summarized. The nanoeffects of nanomaterials on the regulation of bone-related biological functions are highlighted. How to prepare nanomaterials with combinative bone-biomimicry features according to the bone healing process is prospected in order to achieve rapid bone regeneration in situ.

Electrospun protein nanofibers in healthcare: A review

Electrospun nanofibers are being utilized for a wide range of healthcare applications. A plethora of natural and synthetic polymers are exploited for their ability to be electrospun and replace the complex habitat provided by the extracellular matrix for the cells. The fabrication of nanofibers can be tuned to act as a multicarrier system to deliver drugs, growth factors and health supplements etc. in a sustained manner. Owing to its pliability, nanofibers reached its heights in tissue engineering and drug delivery applications. This review mainly focuses on various standardized parameters and optimized blending ratios for animal and plant proteins to yield fine, continuous nanofibers for effective utilization in various healthcare applications.

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.

Engineered Biomaterials to Enhance Stem Cell-Based Cardiac Tissue Engineering and Therapy

Cardiovascular disease is a leading cause of death worldwide. Since adult cardiac cells are limited in their proliferation, cardiac tissue with dead or damaged cardiac cells downstream of the occluded vessel does not regenerate after myocardial infarction. The cardiac tissue is then replaced with nonfunctional fibrotic scar tissue rather than new cardiac cells, which leaves the heart weak. The limited proliferation ability of host cardiac cells has motivated investigators to research the potential cardiac regenerative ability of stem cells. Considerable progress has been made in this endeavor. However, the optimum type of stem cells along with the most suitable matrix-material and cellular microenvironmental cues are yet to be identified or agreed upon. This review presents an overview of various types of biofunctional materials and biomaterial matrices, which in combination with stem cells, have shown promises for cardiac tissue replacement and reinforcement. Engineered biomaterials also have applications in cardiac tissue engineering, in which tissue constructs are developed in vitro by combining stem cells and biomaterial scaffolds for drug screening or eventual implantation. This review highlights the benefits of using biomaterials in conjunction with stem cells to repair damaged myocardium and give a brief description of the properties of these biomaterials that make them such valuable tools to the field.

Biomaterial property-controlled stem cell fates for cardiac regeneration

Myocardial infarction (MI) affects more than 8 million people in the United States alone. Due to the insufficient regeneration capacity of the native myocardium, one widely studied approach is cardiac tissue engineering, in which cells are delivered with or without biomaterials and/or regulatory factors to fully regenerate the cardiac functions. Specifically, in vitro cardiac tissue engineering focuses on using biomaterials as a reservoir for cells to attach, as well as a carrier of various regulatory factors such as growth factors and peptides, providing high cell retention and a proper microenvironment for cells to migrate, grow and differentiate within the scaffolds before implantation. Many studies have shown that the full establishment of a functional cardiac tissue in vitro requires synergistic actions between the seeded cells, the tissue culture condition, and the biochemical and biophysical environment provided by the biomaterials-based scaffolds. Proper electrical stimulation and mechanical stretch during the in vitro culture can induce the ordered orientation and differentiation of the seeded cells. On the other hand, the various scaffolds biochemical and biophysical properties such as polymer composition, ligand concentration, biodegradability, scaffold topography and mechanical properties can also have a significant effect on the cellular processes.

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Cell therapy is an attractive approach for cardiac regeneration after myocardial infarction.

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Biomaterials are used as cell carriers.

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This review highlights how biochemical and biophysical properties of biomaterials affect cell fates.

In vivo experience with natural scaffolds for myocardial infarction: the times they are a-changin'

Treating a myocardial infarction (MI), the most frequent cause of death worldwide, remains one of the most exciting medical challenges in the 21st century. Cardiac tissue engineering, a novel emerging treatment, involves the use of therapeutic cells supported by a scaffold for regenerating the infarcted area. It is essential to select the appropriate scaffold material; the ideal one should provide a suitable cellular microenvironment, mimic the native myocardium, and allow mechanical and electrical coupling with host tissues. Among available scaffold materials, natural scaffolds are preferable for achieving these purposes because they possess myocardial extracellular matrix properties and structures. Here, we review several natural scaffolds for applications in MI management, with a focus on pre-clinical studies and clinical trials performed to date. We also evaluate scaffolds combined with different cell types and proteins for their ability to promote improved heart function, contractility and neovascularization, and attenuate adverse ventricular remodeling. Although further refinement is necessary in the coming years, promising results indicate that natural scaffolds may be a valuable translational therapeutic option with clinical impact in MI repair.

Engineering nanoscale stem cell niche: direct stem cell behavior at cell-matrix interface

Biophysical cues on the extracellular matrix (ECM) have proven to be significant regulators of stem cell behavior and evolution. Understanding the interplay of these cells and their extracellular microenvironment is critical to future tissue engineering and regenerative medicine, both of which require a means of controlled differentiation. Research suggests that nanotopography, which mimics the local, nanoscale, topographic cues within the stem cell niche, could be a way to achieve large-scale proliferation and control of stem cells in vitro. This Progress Report reviews the history and contemporary advancements of this technology, and pays special attention to nanotopographic fabrication methods and the effect of different nanoscale patterns on stem cell response. Finally, it outlines potential intracellular mechanisms behind this response.

Biomimetic approaches for cell implantation to the restoration of infarcted myocardium

Compelling evidences accumulated over the years have proven stem cells as a promising source for regenerative medicine. However, the inadequacy with the design of delivery modalities has prolonged the research in realizing an ideal cell-based approach for the regeneration of infarcted myocardium. Currently, some modest improvements in cardiac function have been documented in clinical trials with stem cell treatments, although regenerating a fully functional myocardium remains a dream for cardiac surgeons. This review provides an overview on the significance of stem cell therapy, the current attempts to resolve the drawbacks with the cell implantation approach and the various stratagems adopted with electrospun hybrid nanofibers for implementation in myocardial regenerative therapy.

A novel polyurethane/cellulose fibrous scaffold for cardiac tissue engineering

A high mechanical strength and biomimetic scaffold is electrospun from a blend of polyurethane and ethyl cellulose, being promising in applications for therapeutic purposes as a cardiac graft for reconstructing or regeneration of damaged myocardium.

Nanotopographical Surfaces for Stem Cell Fate Control: Engineering Mechanobiology from the Bottom

During embryogenesis and tissue maintenance and repair in an adult organism, a myriad of stem cells are regulated by their surrounding extracellular matrix (ECM) enriched with tissue/organ-specific nanoscale topographical cues to adopt different fates and functions. Attributed to their capability of self-renewal and differentiation into most types of somatic cells, stem cells also hold tremendous promise for regenerative medicine and drug screening. However, a major challenge remains as to achieve fate control of stem cells in vitro with high specificity and yield. Recent exciting advances in nanotechnology and materials science have enabled versatile, robust, and large-scale stem cell engineering in vitro through developments of synthetic nanotopographical surfaces mimicking topological features of stem cell niches. In addition to generating new insights for stem cell biology and embryonic development, this effort opens up unlimited opportunities for innovations in stem cell-based applications. This review is therefore to provide a summary of recent progress along this research direction, with perspectives focusing on emerging methods for generating nanotopographical surfaces and their applications in stem cell research. Furthermore, we provide a review of classical as well as emerging cellular mechano-sensing and -transduction mechanisms underlying stem cell nanotopography sensitivity and also give some hypotheses in regard to how a multitude of signaling events in cellular mechanotransduction may converge and be integrated into core pathways controlling stem cell fate in response to extracellular nanotopography.

Enrichment of breast cancer stem-like cells by growth on electrospun polycaprolactone-chitosan nanofiber scaffolds

A small population of highly tumorigenic breast cancer cells has recently been identified. These cells, known as breast-cancer stem-like cells (BCSC), express markers similar to mammary stem cells, and are highly resistant to chemotherapy. Currently, study of BCSC is hampered by the inability to propagate these cells in tissue culture without inducing differentiation. Recently, it was reported that proliferation and differentiation can be modified by culturing cells on electrospun nanofibers. Here, we sought to characterize the chemoresistance and stem-like properties of breast cancer cell lines grown on nanofiber scaffolds. Cells cultured on three-dimensional templates of electrospun poly(ε-caprolactone)-chitosan nanofibers showed increases in mammary stem cell markers and in sphere-forming ability compared with cells cultured on polystyrene culture dishes. There was no increase in proliferation of stem cell populations, indicating that culture on nanofibers may inhibit differentiation of BCSC. The increase in stemness was accompanied by increases in resistance to docetaxel and doxorubicin. These data indicate that BCSC populations are enriched in cells cultured on electrospun poly(ε-caprolactone)-chitosan nanofibers, scaffolds that may provide a useful system to study BCSC and their response to anticancer drug treatment.

Nanotechnology in the regulation of stem cell behavior

Stem cells are known for their potential to repair damaged tissues. The adhesion, growth and differentiation of stem cells are likely controlled by the surrounding microenvironment which contains both chemical and physical cues. Physical cues in the microenvironment, for example, nanotopography, were shown to play important roles in stem cell fate decisions. Thus, controlling stem cell behavior by nanoscale topography has become an important issue in stem cell biology. Nanotechnology has emerged as a new exciting field and research from this field has greatly advanced. Nanotechnology allows the manipulation of sophisticated surfaces/scaffolds which can mimic the cellular environment for regulating cellular behaviors. Thus, we summarize recent studies on nanotechnology with applications to stem cell biology, including the regulation of stem cell adhesion, growth, differentiation, tracking and imaging. Understanding the interactions of nanomaterials with stem cells may provide the knowledge to apply to cell-scaffold combinations in tissue engineering and regenerative medicine.

Tissue engineering and regenerative medicine as applied to the gastrointestinal tract

The gastrointestinal (GI) tract is a complex system characterized by multiple cell types with a determined architectural arrangement. Tissue engineering of the GI tract aims to reinstate the architecture and function of all structural layers. The key point for successful tissue regeneration includes the use of cells/biomaterials that elucidate minimal immune response after implantation. Different biomaterial choices and cell sources have been proposed to engineer the GI tract. This review summarizes the recent advances in bioengineering the GI tract with emphasis on cell sources and scaffolding biomaterials.

How Can Nanotechnology Help to Repair the Body? Advances in Cardiac, Skin, Bone, Cartilage and Nerve Tissue Regeneration

Nanotechnologists have become involved in regenerative medicine via creation of biomaterials and nanostructures with potential clinical implications. Their aim is to develop systems that can mimic, reinforce or even create in vivo tissue repair strategies. In fact, in the last decade, important advances in the field of tissue engineering, cell therapy and cell delivery have already been achieved. In this review, we will delve into the latest research advances and discuss whether cell and/or tissue repair devices are a possibility. Focusing on the application of nanotechnology in tissue engineering research, this review highlights recent advances in the application of nano-engineered scaffolds designed to replace or restore the followed tissues: (i) skin; (ii) cartilage; (iii) bone; (iv) nerve; and (v) cardiac.

Improved cellular infiltration in electrospun fiber via engineered porosity

Small pore sizes inherent to electrospun matrices can hinder efficient cellular ingrowth. To facilitate infiltration while retaining its extracellular matrix-like character, electrospinning was combined with salt leaching to produce a scaffold having deliberate, engineered delaminations. We made elegant use of a specific randomizing component of the electrospinning process, the Taylor Cone and the falling fiber beneath it, to produce a uniform, well-spread distribution of salt particles. After 3 weeks of culture, up to 4 mm of cellular infiltration was observed, along with cellular coverage of up to 70% within the delaminations. To our knowledge, this represents the first observation of extensive cellular infiltration of electrospun matrices. Infiltration appears to be driven primarily by localized proliferation rather than coordinated cellular locomotion. Cells also moved from the salt-generated porosity into the surrounding electrospun fiber matrix. Given that the details of salt deposition (amount, size, and number density) are far from optimized, the result provides a convincing illustration of the ability of mammalian cells to interact with appropriately tailored electrospun matrices. These layered structures can be precisely fabricated by varying the deposition interval and particle size conceivably to produce in vivo-like gradients in porosity such that the resulting scaffolds better resemble the desired final structure.