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Vascular disease is a leading cause of death and disability worldwide. Current surgical intervention and treatment options for vascular diseases have exhibited limited long-term success, emphasizing the need to develop advanced treatment paradigms for early detection and more effective treatment of dysfunctional cells in a specific blood vessel lesion. Advances in targeted nanoparticles mediating cargo delivery enables more robust prevention, screening, diagnosis, and treatment of vascular disorders. In particular, nanotheranostics integrates diagnostic imaging and therapeutic function into a single agent, and is an emerging platform towards more effective and localized vascular treatment. This review article highlights recent advances and current challenges associated with the utilization of targeted nanoparticles for real-time diagnosis and treatment of vascular diseases. Given recent developments, nanotheranostics offers great potential to serve as an effective platform for targeted, localized, and personalized vascular treatment.

Stem and progenitor cells that exhibit significant regenerative potential and critical roles in cancer initiation and progression remain difficult to characterize. Cell fates are determined by reciprocal signaling between the cell microenvironment and the nucleus; hence parameters derived from nuclear remodeling are ideal candidates for stem/progenitor cell characterization. Here we applied high-content, single cell analysis of nuclear shape and organization to examine stem and progenitor cells destined to distinct differentiation endpoints, yet undistinguishable by conventional methods. Nuclear descriptors defined through image informatics classified mesenchymal stem cells poised to either adipogenic or osteogenic differentiation, and oligodendrocyte precursors isolated from different regions of the brain and destined to distinct astrocyte subtypes. Nuclear descriptors also revealed early changes in stem cells after chemical oncogenesis, allowing the identification of a class of cancer-mitigating biomaterials. To capture the metrology of nuclear changes, we developed a simple and quantitative "imaging-derived" parsing index, which reflects the dynamic evolution of the high-dimensional space of nuclear organizational features. A comparative analysis of parsing outcomes via either nuclear shape or textural metrics of the nuclear structural protein NuMA indicates the nuclear shape alone is a weak phenotypic predictor. In contrast, variations in the NuMA organization parsed emergent cell phenotypes and discerned emergent stages of stem cell transformation, supporting a prognosticating role for this protein in the outcomes of nuclear functions.

A practical approach toward developing dual-functional hydrogels with high adhesiveness and hydrophobic drug delivery is described. An additional Schiff base reaction was introduced into a phenol-phenol crosslinked gelatin hydrogel to markedly increase adhesiveness. Oxidized beta-cyclodextrin (o beta-CD) functionalized with aldehyde groups and possessing a hydrophobic cavity was exploited as a crosslinker in the Schiff base reaction to solubilize the hydrophobic drug. Simply blending gelatin-tyramine (GTA) and ob-CD in the presence of horseradish peroxidase (HRP)/H2O2 rapidly and controllably formed GTAo beta-CD hydrogels in situ. The optimal composition of GTA-o beta-CD hydrogels was found to be 5 wt% GTA (GTA5) with 1 wt% ob-CD. Their adhesiveness was 2.3-and 6.2-fold higher than those of GTA-only hydrogels and fibrin glue, respectively. Their elastic modulus and degradation rate were 1.8-and 1.5-fold higher than those of GTA hydrogels owing to additional imine bonds. Hydrophobic drugs (dexamethasone and curcumin) could be dissolved homogeneously in GTA-o beta-CD matrices with greater loading efficiencies than in GTA matrices. An in vitro test of cell viability using human dermal fibroblasts demonstrated that GTA-o beta-CD hydrogels were cytocompatible. In summary, dual-functional injectable GTA-o beta-CD hydrogels can be used as a promising platform to improve tissue adhesion and hydrophobic drug delivery.

hMSC source-specific behaviors in 3D NO gel represent EC-like differentiation of ADSCs and pericyte-like characteristics of BMSCs., Angiogenesis is stimulated by nitric oxide (NO) production in endothelial cells (ECs). Although proangiogenic actions of human mesenchymal stem cells (hMSCs) have been extensively studied, the mechanistic role of NO in this action remains obscure. Here, we used a gelatin hydrogel that releases NO upon crosslinking by a transglutaminase reaction (“NO gel”). Then, the source-specific behaviors of bone marrow versus adipose tissue-derived hMSCs (BMSCs versus ADSCs) were monitored in the NO gels. NO inhibition resulted in significant decreases in their angiogenic activities. The NO gel induced pericyte-like characteristics in BMSCs in contrast to EC differentiation in ADSCs, as evidenced by tube stabilization versus tube formation, 3D colocalization versus 2D coformation with EC tube networks, pericyte-like wound healing versus EC-like vasculogenesis in gel plugs, and pericyte versus EC marker production. These results provide previously unidentified insights into the effects of NO in regulating hMSC source-specific angiogenic mechanisms and their therapeutic applications.

Angiogenesis induction into damaged sites has long been an unresolved issue. Local treatment with pro-angiogenic molecules has been the most common approach. However, this approach has critical side effects including inflammatory coupling, tumorous vascular activation, and off-target circulation. Here, the concept that a structure can guide desirable biological function is applied to physically engineer three-dimensional channel networks in implant sites, without any therapeutic treatment. Microchannel networks are generated in a gelatin hydrogel to overcome the diffusion limit of nutrients and oxygen three-dimensionally. Hydrogel implantation in mouse and porcine models of hindlimb ischemia rescues severely damaged tissues by the ingrowth of neighboring host vessels with microchannel perfusion. This effect is guided by microchannel size-specific regenerative macrophage polarization with the consequent functional recovery of endothelial cells. Multiple-site implantation reveals hypoxia and neighboring vessels as major causative factors of the beneficial function. This technique may contribute to the development of therapeutics for hypoxia/inflammatory-related diseases., Restoration of blood flow to damaged sites has commonly involved treatment with pro-angiogenic molecules but these have undesired side effects. Here the authors present a microchannel-patterned gelatin hydrogel that is able to rescue mouse and porcine models of hindlimb ischemia.

Stimuli-responsive biomaterials undergo significant alterations in material structure and property in response to changes of local environmental factors (e.g. pH, temperature, enzyme activation, and water absorption). In particular, reactive oxygen species (ROS) is considered as a major stimulus because over-production of ROS involves most types of major pathogenesis. The application of ROS-responsive biomaterials requires suitable material designs to program user-defined changes of their structure and property in response to a sudden change in the local ROS level. This chapter summarizes the progress in designing and applying major types of ROS-responsive biomaterials within the past 10 years.

Superparamagnetic iron oxide nanoparticles (SPIONs) are often encapsulated into drug-carrying nano/microsized particles for simultaneous magnetic resonance (MR) imaging and treatment of diseased tissues. Unfortunately, encapsulated SPIONs may have a limited ability to modulate the T(2)-weighted relaxation of water protons, but this insight has not been examined systematically. This study demonstrates that SPIONs immobilized on 200 nm diameter poly(lactic-co-glycolic acid) (PLGA) nanoparticles using Pickering emulsification present 18-fold higher relaxivity than encapsulated SPIONs and 1.5-fold higher relaxivity than free SPIONs. In contrast, the SPIONs immobilized on 10 μm diameter PLGA particles exhibit a minor increase in MR relaxivity. This interesting finding will significantly impact current efforts to synthesize and assemble advanced MR contrast agents.

Shape memory materials have been successfully applied to minimally invasive implantation of medical devices. However, organ-movement-specific shape programing at a microscale level has never been demonstrated despite significant unmet needs. As vein-to-artery grafting induces vein dilation and stenosis, a polymeric self-enclosable external support (SES) is designed to wrap the vascular out-wall. Its micropores are programmed to increase sizes and interconnections upon dilation. Vessel dilation promotes venous maturation, but overdilation induces stenosis by disturbed blood flow. Therefore, the unique elastic shape-fixity of SES provides a foundation to enable a stable microscale shape transition by maintaining the vein dilation. The shape transition of micropore architecture upon dilation induces beneficial inflammation, thereby regenerating vasa vasorum and directing smooth muscle cell migration toward adventitia with the consequent muscle reinforcement of veins. This game-changer approach prevents the stenosis of vein-to-artery grafting by rescuing ischemic disorders and promoting arterial properties of veins.

Thermo-responsive shape memory polymers (SMPs) can be programmed to fit into small-bore incisions and recover their functional shape upon deployment in the body. This property is of significant interest for developing the next generation of minimally-invasive medical devices. To be used in such applications, SMPs should exhibit adequate mechanical strengths that minimize adverse compliance mismatch-induced host responses (e.g. thrombosis, hyperplasia), be biodegradable, and demonstrate switch-like shape recovery near body temperature with favorable biocompatibility. Combinatorial approaches are essential in optimizing SMP material properties for a particular application. In this study, a new class of thermo-responsive SMPs with pendant, photocrosslinkable allyl groups, x%poly(e-caprolactone)-co-y%(α-allyl carboxylate e-caprolactone) (x%PCL-y%ACPCL), are created in a robust, facile manner with readily tunable material properties. Thermomechanical and shape memory properties can be drastically altered through subtle changes in allyl composition. Molecular weight and gel content can also be altered in this combinatorial format to fine-tune material properties. Materials exhibit highly elastic, switch-like shape recovery near 37 °C. Endothelial compatibility is comparable to tissue culture polystyrene (TCPS) and 100%PCL in vitro and vascular compatibility is demonstrated in vivo in a murine model of hindlimb ischemia, indicating promising suitability for vascular applications. Statement of Significance With the ongoing thrust to make surgeries minimally-invasive, it is prudent to develop new biomaterials that are highly compatible and effective in this workflow. Thermo-responsive shape memory polymers (SMPs) have great potential for minimally-invasive applications because SMP medical devices (e.g. stents, grafts) can fit into small-bore minimally-invasive surgical devices and recover their functional shape when deployed in the body. To realize their potential, it is imperative to devise combinatorial approaches that enable optimization of mechanical, SM, and cellular responses for a particular application. In this study, a new class of thermo-responsive SMPs is created in a robust, facile manner with readily tunable material properties. Materials exhibit excellent, switch-like shape recovery near body temperature and promising biocompatibility for minimally-invasive vascular applications.

The organization and composition of the extracellular matrix (ECM) have been shown to impact the propagation of electrical signals in multiple tissue types. To date, many studies with electroactive biomaterial substrates have relied upon passive electrical stimulation of the ionic media to affect cell behavior. However, development of cell culture systems in which stimulation can be directly applied to the material – thereby isolating the signal to the cell-material interface and cell–cell contracts – would provide a more physiologically-relevant paradigm for investigating how electrical cues modulate lineage-specific stem cell differentiation. In the present study, we have employed unmodified, directly-stimulated, (un)patterned graphene as a cell culture substrate to investigate how extrinsic electrical cycling influences the differentiation of naïve human mesenchymal stem cells (hMSCs) without the bias of exogenous biochemicals. We first demonstrated that cyclic stimulation does not deteriorate the cell culture media or result in cytotoxic pH, which are critical experiments for correct interpretation of changes in cell behavior. We then measured how the expression of osteogenic and neurogenic lineage-specific markers were altered simply by exposure to electrical stimulation and/or physical patterns. Expression of the early osteogenic transcription factor RUNX2 was increased by electrical stimulation on all graphene substrates, but the mature marker osteopontin was only modulated when stimulation was combined with physical patterns. In contrast, the expression of the neurogenic markers MAP2 and β3-tubulin were enhanced in all electrical stimulation conditions, and were less responsive to the presence of patterns. These data indicate that specific combinations of non- biological inputs – material type, electrical stimulation, physical patterns – can regulate hMSC lineage specification. This study represents a substantial step in understanding how the interplay of electrophysical stimuli regulate stem cell behavior and helps to clarify the potential for graphene substrates in tissue engineering applications.

Cardiomyocytes derived from human induced pluripotent stem cells (iPSC-CMs) hold great promise for modeling human heart diseases. However, iPSC-CMs studied to date resemble immature embryonic myocytes and therefore do not adequately recapitulate native adult cardiomyocyte phenotypes. Since extracellular matrix plays an essential role in heart development and maturation in vivo , we sought to develop a synthetic culture matrix that could enhance functional maturation of iPSC-CMs in vitro . In this study, we employed a library of combinatorial polymers comprising of three functional subunits – poly-e-caprolacton (PCL), polyethylene glycol (PEG), and carboxylated PCL (cPCL) – as synthetic substrates for culturing human iPSC-CMs. Of these, iPSC-CMs cultured on 4%PEG-96%PCL (each % indicates the corresponding molar ratio) exhibit the greatest contractility and mitochondrial function. These functional enhancements are associated with increased expression of cardiac myosin light chain-2v, cardiac troponin I and integrin alpha-7. Importantly, iPSC-CMs cultured on 4%PEG-96%PCL demonstrate troponin I (TnI) isoform switch from the fetal slow skeletal TnI (ssTnI) to the postnatal cardiac TnI (cTnI), the first report of such transition in vitro . Finally, culturing iPSC-CMs on 4%PEG-96%PCL also significantly increased expression of genes encoding intermediate filaments known to transduce integrin-mediated mechanical signals to the myofilaments. In summary, our study demonstrates that synthetic culture matrices engineered from combinatorial polymers can be utilized to promote in vitro maturation of human iPSC-CMs through the engagement of critical matrix-integrin interactions.

Effective treatment of diabetic neuropathy (DN) remains unsolved. We serendipitously observed dramatic relief of pain in several patients with painful DN receiving granulocyte-colony stimulating factor (G-CSF). The aim of this study was to determine if G-CSF could treat DN in an animal model and to ascertain its mechanism of action. In a rodent model of DN, G-CSF dramatically recovered nerve function, retarded histological nerve changes and increased the expression of neurotrophic factors within nerve. A sex-mismatched bone marrow transplantation (BMT) study revealed that G-CSF treatment increased the abundance of bone marrow (BM)-derived cells in nerves damaged by DN. However, we did not observe evidence of transdifferentiation or cell fusion of BM-derived cells. The beneficial effects of G-CSF were dependent on the integrity of BM. In conclusion, G-CSF produced a therapeutic effect in a rodent model of DN, which was attributed, at least in part, to the actions of BM-derived cells.

Live models that resemble surgical conditions of humans are needed for training free-flap harvesting and anastomosis. Animal models for training purposes have been available for years in many surgical fields. We used the female (because they are easy to handle for the procedure) Yorkshire pigs for the head and neck reconstruction by harvesting the deep inferior epigastric artery perforator or the superior epigastric artery perforator flap. The anastomosis site (neck skin defect or tracheal wall defect) was prepared via the dissection of the common carotid artery and the internal jugular vein, in which 3.5× loupe magnification was used for anastomosis as we use on human cases in real life. This procedure demonstrates a new training method using a reliable learning model and provides a detailed anatomy in a live scenario. We focused on the ischemia time, harvesting, vessel anastomosis, and designing the flap to fit the defect site. This model improves tissue handling and with the use of proper instruments can be repeated many times so that the surgeon is fully confident before starting the surgery on humans.

To date, bone tissue regeneration strategies lack an approach that effectively provides an osteogenic and angiogenic environment conducive to bone growth. In the current study, we evaluated the osteogenic and angiogenic response of human mesenchymal stem cells (hMSCs) and green fluorescent protein-expressing human umbilical vein endothelial cells (GFP-HUVECs) cocultured on a self-assembled, peptide amphiphile nanomatrix functionalized with the cell adhesive ligand RGDS (PA-RGDS). Analysis of alkaline phosphatase activity, von Kossa staining, Alizarin Red quantification, and osteogenic gene expression, indicates a significant synergistic effect between the PA-RGDS nanomatrix and coculture that promoted hMSC osteogenesis. In addition, coculturing on PA-RGDS resulted in enhanced HUVEC network formation and upregulated vascular endothelial growth factor gene and protein expression. Though PA-RGDS and coculturing hMSCs with HUVECs were each previously reported to individually enhance hMSC osteogenesis, this study is the first to demonstrate a synergistic promotion of HUVEC angiogenesis and hMSC osteogenesis by integrating coculturing with the PA-RGDS nanomatrix. We believe that using the combination of hMSC/HUVEC coculture and PA-RGDS substrate is an efficient method for promoting osteogenesis and angiogenesis, which has immense potential as an efficacious, engineered platform for bone tissue regeneration.

Stimuli-responsive biomaterials undergo significant alterations in material structure and property in response to changes of local environmental factors (e.g. pH, temperature, enzyme activation, and water absorption). In particular, reactive oxygen species (ROS) is considered as a major stimulus because over-production of ROS involves most types of major pathogenesis. The application of ROS-responsive biomaterials requires suitable material designs to program user-defined changes of their structure and property in response to a sudden change in the local ROS level. This chapter summarizes the progress in designing and applying major types of ROS-responsive biomaterials within the past 10 years.

Stem cells have recently emerged as an important candidate for cell therapy. However, some major limitations still exist such as a small quantity of cell supply, senescence, and insufficient differentiation efficiency. Therefore, there is an unmet need to control stem cell behavior for better clinical performance. Since native microenvironment factors including stem cell niche, genetic factors, and growth factors direct stem cell fate cooperatively, user-specified in vitro settings are required to understand the regulatory roles and effects of each factor, thereby applying the factors for improved cell therapy. Among others, various types of biomaterials and transfection method have been employed as key tools for development of the in vitro settings. This review focuses on the current strategies to improve stemness maintenance, direct differentiation, and reprogramming using biomaterials and genetic factors without any aids from additional biochemicals and growth factors.

The leading cause of synthetic graft failure includes thrombotic occlusion and intimal hyperplasia at the site of vascular anastomosis. Herein, we report a co- immobilization strategy of heparin and potent anti-neointimal drug (Mitogen Activated Protein Kinase II inhibitory peptide; MK2i) by using a tyrosinase-catalyzed oxidative reaction for preventing thrombotic occlusion and neointimal formation of synthetic vascular grafts. The binding of heparin–tyramine polymer (HT) onto the polycarprolactone (PCL) surface enhanced blood compatibility with significantly reduced protein absorption (64.7% decrease) and platelet adhesion (82.2% decrease) compared to bare PCL surface. When loading MK2i, 1) the HT depot surface gained high MK2i- loading efficiency through charge-charge interaction, and 2) this depot platform enabled long-term, controlled release over 4 weeks (92–272 μg/mL of MK2i). The released MK2i showed significant inhibitory effects on VSMC migration through down-regulated phosphorylation of target proteins (HSP27 and CREB) associated with intimal hyperplasia. In addition, it was found that the released MK2i infiltrated into the tissue with a cumulative manner in ex vivo human saphenous vein (HSV) model. This present study demonstrates that enzymatically HT-coated surface modification is an effective strategy to induce long-term MK2i release as well as hemocompatibility, thereby improving anti- neointimal activity of synthetic vascular grafts.

Peripheral artery disease (PAD) is characterized by vessel occlusion and ischemia in the limbs. Treatment for PAD with surgical interventions has been showing limited success. Moreover, recent clinical trials with treatment of angiogenic growth factors proved ineffective as increased angiogenesis triggered severe inflammation in a proportionally coupled fashion. Hence, the overarching goal of this research was to address this issue by developing a biomaterial system that enables controlled, dual delivery of pro-angiogenic C16 and anti-inflammatory Ac-SDKP peptides in a minimally-invasive way. To achieve the goal, a peptide-loaded injectable microgel system was developed and tested in a mouse model of PAD. When delivered through multiple, low volume injections, the combination of C16 and Ac-SDKP peptides promoted angiogenesis, muscle regeneration, and perfusion recovery, while minimizing detrimental inflammation. Additionally, this peptide combination regulated inflammatory TNF-α pathways independently of MMP-9 mediated pathways of angiogenesis in vitro, suggesting a potential mechanism by which angiogenic and inflammatory responses can be uncoupled in the context of PAD. This study demonstrates a translatable potential of the dual peptide-loaded injectable microgel system for PAD treatment.

Human bone marrow derived mesenchymal stem cells (hMSCs) hold great promise for regenerative medicine due to their multipotent differentiation capacity and immunomodulatory capabilities. Substantial research has elucidated mechanisms by which extracellular cues regulate hMSC fate decisions, but considerably less work has addressed how material properties can be leveraged to maintain undifferentiated stem cells. Here, we show that synthetic culture substrates designed to exhibit moderate cell-repellency promote high stemness and low oxidative stress—two indicators of naïve, healthy stem cells—in commercial and patient-derived hMSCs. Furthermore, the material-mediated effect on cell behavior can be tuned by altering the molar percentage (mol %) and/or chain length of poly(ethylene glycol) (PEG), the repellant block linked to hydrophobic poly(ε-caprolactone) (PCL) in the copolymer backbone. Nano- and angstrom-scale characterization of the cell-material interface reveals that PEG interrupts the adhesive PCL domains in a chain-length-dependent manner; this prevents hMSCs from forming mature focal adhesions and subsequently promotes cell–cell adhesions that require connexin-43. This study is the first to demonstrate that intrinsic properties of synthetic materials can be tuned to regulate the stemness and redox capacity of hMSCs and provides new insight for designing highly scalable, programmable culture platforms for clinical translation.

The blood-brain barrier (BBB) plays a critical role in brain homeostasis at the cellular and global level. Mimicking the selective permeability and transport properties of the BBB to specific molecules and cells remains a significant challenge towards the development of a physiologically relevant in vitro BBB model. In this study, we developed electrospun poly (e-caprolactone) (PCL) and polyethylene glycol (PEG) copolymer membranes that supported different cellular components of the neurovascular unit including human-derived endothelial cells, pericytes and astrocytes. Comparative analyses of thickness, morphology, biocompatibility and permeability of membranes were also conducted. We found that collagen coated 4%PEG-96%PCL membranes supported the growth of a confluent and tight endothelium confirmed by transendothelial electrical resistance measurements (TEER). Based on fabrication process and reported results, we finally discuss the adoption of these electrospun fiber membranes for in vitro and on-a-chip human BBB models.

Remarkable achievements have been made in the clinical application of mechanical circulatory support and cardiac transplantation for patients with end-stage heart failure. Despite the successes, complications associated with these therapies continue to drive cardiac regenerative research utilizing stem cell based therapies. Multiple stem cell lineages hold clinical promise for cardiac regeneration—mostly through cellular differentiation, cellular fusion, and paracrine signaling mechanisms. Bone marrow-derived endothelial progenitor cells are among the most intriguing and controversial cell types currently being investigated. Formidable barriers exist, however, in finding the ideal cardiac regenerative stem cell, such as identifying specific lineage markers, optimizing in vitro cellular expansion and improving methods of stem cell delivery. Hybrid approaches of cardiac regeneration using stem cell therapies in conjunction with immunomodulation after cardiac transplantation or with mechanical circulatory support produce cutting edge stem cell technologies. This review summarizes the current knowledge and therapeutic applications of stem cells in patients with end-stage heart failure, including stem cell therapy after implantation of mechanical circulatory support and cardiac transplantation. J. Cell. Biochem. 115: 1217–1224, 2014. © 2014 Wiley Periodicals, Inc.

Background Mechanical properties and cyto-compatibility of a composite scaffold which possessed negative (−) Poisson’s ratio (NPR) was investigated for effective load transfer from auxetic scaffold to cell. Methods Organic/inorganic composite scaffolds were prepared by mixing hydroxyapatite (HA) to poly(lactide-co-glycolide) (PLGA). To induce NPR in composite scaffold, 3-directional volumetric compression was applied during the scaffold fabrication at adequate temperature(60°C). The pore size of scaffold ranged between 355–400 μm. Results Poisson’s ratios of NPR scaffolds and control scaffolds were −0.07 and 0.16 at 10 % strain. For stable physical stimulating to loaded cells, ceramic/polymer composite scaffold was prepared by incorporating HA in PLGA to increase mechanical strength. Compressive strength of the HA/PLGA composite scaffold (15 wt. % HA to PLGA) was about 21.7 % higher than that of PLGA-only scaffold. The recovery rates of the NPR composite scaffold after applying compression in the dry and wet states were 90 % and 60 %, respectively. Also the composite scaffold was shown to have better hydrophilicity (61.9°) compared to the PLGA-only scaffolds (65.3°). Cell proliferation of osteoblast-like cell line (MG-63) in the composite scaffold was 20 % higher than in PLGA-only scaffold at static compressive stimulation. For dynamic compressive stimulation (15 min cyclic interval), cell proliferation in the composite scaffold was 2 times higher than that of in PLGA-only scaffold. In conclusion, NPR composite (HA/PLGA) scaffold was effective in isotropic compressive load delivery for osteogenic cell proliferation. Conclusion This composite scaffold with stimulation can be used as tissue engineered scaffold and dynamic cell culture system for bone tissue regeneration.

Inserting a graft into vessels with different diameters frequently causes severe damage to the host vessels. Poor flow patency is an unresolved issue in grafts, particularly those with diameters less than 6 mm, because of vessel occlusion caused by disturbed blood flow following fast clotting. Herein, successful patency in the deployment of an ≈2 mm diameter graft into a porcine vessel is reported. A new library of property-tunable shape-memory polymers that prevent vessel damage by expanding the graft diameter circumferentially upon implantation is presented. The polymers undergo seven consecutive cycles of strain energy-preserved shape programming. Moreover, the new graft tube, which features a diffuser shape, minimizes disturbed flow formation and prevents thrombosis because its surface is coated with nitric-oxide-releasing peptides. Improved patency in a porcine vessel for 18 d is demonstrated while occlusive vascular remodeling occurs. These insights will help advance vascular graft design.

Aim: To evaluate the efficacy of electrically conductive, biocompatible composite scaffolds in modulating the cardiomyogenic differentiation of human mesenchymal stem cells (hMSCs). Materials & methods: Electrospun scaffolds of poly(ε-caprolactone) with or without carbon nanotubes were developed to promote the in vitro cardiac differentiation of hMSCs. Results: Results indicate that hMSC differentiation can be enhanced by either culturing in electrically conductive, carbon nanotube-containing composite scaffolds without electrical stimulation in the presence of 5-azacytidine, or extrinsic electrical stimulation in nonconductive poly(ε-caprolactone) scaffolds without carbon nanotube and azacytidine. Conclusion: This study suggests a first step towards improving hMSC cardiomyogenic differentiation for local delivery into the infarcted myocardium. Original submitted 23 July 2012; Revised submitted 31 October 2012; Published online 27 March 2013

Understanding cellular interactions with culture substrate features is important to advance cell biology and regenerative medicine. When surface topographical features are considerably larger in vertical dimension and are spaced at least one cell dimension apart, the features act as 3D physical barriers that can guide cell adhesion, thereby altering cell behavior. In the present study, we investigated competitive interactions of cells with neighboring cells and matrix using a novel nanoneedle gradient array. A gradient array of nanoholes was patterned at the surface of fused silica by single-pulse femtosecond laser machining. A negative replica of the pattern was extracted by nanoimprinting with a thin film of polymer. Silica was deposited on top of the polymer replica to form silica nanoneedles. NIH 3T3 fibroblasts were cultured on silica nanoneedles and their behavior was studied and compared with those cultured on a flat silica surface. The presence of silica nanoneedles was found to enhance the adhesion of fibroblasts while maintaining cell viability. The anisotropy in the arrangement of silica nanoneedles was found to affect the morphology and spreading of fibroblasts. Additionally, variations in nanoneedle spacing regulated cell–matrix and cell–cell interactions, effectively preventing cell aggregation in areas of tightly-packed nanoneedles. This proof-of-concept study provides a reproducible means for controlling competitive cell adhesion events and offers a novel system whose properties can be manipulated to intimately control cell behavior.

Circulating monocytes undergo spontaneous apoptosis when there is no activation stimulus, which is critical to population control for proper host response to implants. As activation and apoptosis of monocytes/macrophages are regulated by cell-cell and cell-matrix interactions, their regulatory mechanism was investigated in this study using polyethylene glycol (PEG)-containing polyurethane films in which PEG-rich and polyester-rich domains were phase separated. Human blood monocyte-derived macrophages (HBMs) preferentially adhered to PEG domains (cell-matrix interaction) due to the low molecular weight (600 g mol⁻¹), resulting in increased HBM density (cell-cell interaction). As both cell-cell and cell-matrix interactions were promoted, HBM apoptosis increased, while their activation as measured by phagocytosis, intracellular reactive oxygen species (ROS) level and matrix metalloproteinase-9 production decreased compared to PEG-free films. When cell seeding density and cell-adhesive gelatin coating on silicone films were controlled, a cooperative role of cell-matrix (adhesion) and cell-cell (density) interactions in inducing HBM apoptosis was observed. Expression of the macrophage adhesion molecule CD11b caused apoptosis in this context, which was mediated by tissue necrosis factor-α signaling but down-regulated by the ROS inhibitor diphenylene iodonium and the anti-inflammatory peptide Ac-SDKP, suggesting a new concept for the design of biomaterials that allows for cell adhesion without excessive inflammatory activation.

Recently, significant progress has been made in developing “stimuli-sensitive” biomaterials as a new therapeutic approach to interact with dynamic physiological conditions. Reactive oxygen species (ROS) production has been implicated in important pathophysiological events, such as atherosclerosis, aging, and cancer. ROS are often overproduced locally in diseased cells and tissues, and they individually and synchronously contribute to many of the abnormalities associated with local pathogenesis. Therefore, the advantages of developing ROS-responsive materials extend beyond site-specific targeting of therapeutic delivery, and potentially include navigating, sensing, and repairing the cellular damages via programmed changes in material properties. Here we review the mechanism and development of biomaterials with ROS-induced solubility switch or degradation, as well as their performance and potential for future biomedical applications.

Background Auxetic scaffolds (experimental) was fabricated by using poly(D, L-lactic-co-glycolic acid), 50:50, (PLGA) for effective bone cell proliferation with mechanical stimulation. Methods Negative Poisson’s ratio in scaffold, 3-directional volumetric compression was applied during the scaffold fabrication at adequate temperature (60 °C). The pore size of scaffold ranged between 355 and 400 μm. Results The porous morphology of the prepared auxetic scaffolds had shown partially concave and dent shapes in SEM image as expected. The lowest Poisson’s ratios of experimental group was −0.07 at 60 °C/10 min. Compressive strength of experimental group was shown about 3.12 times higher than control group (conventional scaffold) in dry state at 25 °C. The compressive strengths of both groups were tended to be decreased dramatically in wet state compared to in dry state. However, compressive strengths of experimental group were higher 3.08 times and 1.88 times in EtOH/PBS (25 °C) and EtOH/PBS/DMEM (37 °C) than control group in wet state, respectively. Degradation rate of the scaffolds showed about 16 % weight loss in 5 weeks. In cell attachment test, experimental group showed 1.46 times higher cell proliferation than control group at 1-day with compressive stimulation. In 3-day culture, the experimental group showed 1.32 times higher than control group. However, there was no significant difference in cell proliferation in 5-day cultivation. Conclusion Overall, negative Poisson’s ratio scaffolds with static mechanical stimulation could affect the cell proliferation at initial cultivation time.

Material-induced cell aggregation drives a proangiogenic expression profile. Copolymer substrates containing cell-repellent and cell-adhesive domains force the aggregation of human mesenchymal stem cells, which results in enhanced tubulogenesis in vitro and stabilization of vasculature in vivo. These findings can be used to design instructive biomaterial scaffolds for clinical use.

A key parameter in the operation of an electrochemical double-layer capacitor is the voltage window, which dictates the device energy density and power density. Here we demonstrate experimental evidence that π-π stacking at a carbon-ionic liquid interface can modify the operation voltage of a supercapacitor device by up to 30%, and this can be recovered by steric hindrance at the electrode-electrolyte interface introduced by poly(ethylene oxide) polymer electrolyte additives. This observation is supported by Raman spectroscopy, electrochemical impedance spectroscopy, and differential scanning calorimetry that each independently elucidates the signature of π-π stacking between imidazole groups in the ionic liquid and the carbon surface and the role this plays to lower the energy barrier for charge transfer at the electrode-electrolyte interface. This effect is further observed universally across two separate ionic liquid electrolyte systems and is validated by control experiments showing an invariant electrochemical window in the absence of a carbon-ionic liquid electrode-electrolyte interface. As interfacial or noncovalent interactions are usually neglected in the mechanistic picture of double-layer capacitors, this work highlights the importance of understanding chemical properties at supercapacitor interfaces to engineer voltage and energy capability.

Veins used as grafts in heart bypass or as access points in hemodialysis exhibit high failure rates, thereby causing significant morbidity and mortality for patients. Interventional or revisional surgeries required to correct these failures have been met with limited success and exorbitant costs, particularly for the US Centers for Medicare & Medicaid Services. Vein stenosis or occlusion leading to failure is primarily the result of neointimal hyperplasia. Systemic therapies have achieved little long-term success, indicating the need for more localized, sustained, biomaterial-based solutions. Numerous studies have demonstrated the ability of external stents to reduce neointimal hyperplasia. However, successful results from animal models have failed to translate to the clinic thus far, and no external stent is currently approved for use in the US to prevent vein graft or hemodialysis access failures. This review discusses current progress in the field, design considerations, and future perspectives for biomaterial-based external stents. More comparative studies iteratively modulating biomaterial and biomaterial-drug approaches are critical in addressing mechanistic knowledge gaps associated with external stent application to the arteriovenous environment. Addressing these gaps will ultimately lead to more viable solutions that prevent vein graft and hemodialysis access failures.

Polymers have been used extensively taking forms as scaffolds, patterned surface and nanoparticle for regenerative medicine applications. Angiogenesis is an essential process for successful tissue regeneration, and endothelial cell-cell interaction plays a pivotal role in regulating their tight junction formation, a hallmark of angiogenesis. Though continuous progress has been made, strategies to promote angiogenesis still rely on small molecule delivery or nuanced scaffold fabrication. As such, the recent paradigm shift from top-down to bottom-up approaches in tissue engineering necessitates development of polymer-based modular engineering tools to control angiogenesis. Here, we developed cationic nanocylinders (NCs) as inducers of cell-cell interaction and investigated their effect on angiogenic activities of human umbilical vein endothelial cells (HUVECs) in vitro. Electrospun poly (L-lactic acid) (PLLA) fibers were aminolyzed to generate positively charged NCs. The aninolyzation time was changed to produce two different aspect ratios of NCs. When HUVECs were treated with NCs, the electrostatic interaction of cationic NCs with negatively charged plasma membranes promoted migration, permeability and tubulogenesis of HUVECs compared to no treatment. This effect was more profound when the higher aspect ratio NC was used. The results indicate these NCs can be used as a new tool for the bottom-up approach to promote angiogenesis.

Optical neural interfaces offer several advantages over electrophysiological methods in both clinical and experimental applications. Optical stimulation techniques exhibit high spatial selectivity, do not create electrical artifacts, and allow for stimulation of specific neuronal populations. Calcium- and voltage-sensitive dyes can probe neuronal and astrocytic signaling at both single cell and network scales, and miniature optical sensors can measure a variety of physiological signals in situ. However, optical neural interfaces must be robust, safe, and effective over long periods of time in order to be acceptable for use in human patients. In this article, we draw the attention of the materials science community to the need for a new generation of materials that have the necessary optical performance and, at the same time, conform to the constraints placed on implanted devices in terms of size, relevant mechanical properties, and biocompatibility, providing some examples of recent advancements in the field.

Recently, the application of nanostructured materials in the field of tissue engineering has garnered attention to mediate treatment and regeneration of bone defects. In this study, poly(l-lactic acid) (PLLA)/gelatin (PG) fibrous scaffolds are fabricated and β-cyclodextrin (βCD) grafted nano-hydroxyapatite (HAp) is coated onto the fibrous scaffold surface via an interaction between βCD and adamantane. Simvastatin (SIM), which is known to promote osteoblast viability and differentiation, is loaded into the remaining βCD. The specimen morphologies are characterized by scanning electron microscopy. The release profile of SIM from the drug loaded scaffold is also evaluated. In vitro proliferation and osteogenic differentiation of human adipose derived stem cells on SIM/HAp coated PG composite scaffolds is characterized by alkaline phosphatase (ALP) activity, mineralization (Alizarin Red S staining), and real time Polymerase chain reaction (PCR). The scaffolds are then implanted into rabbit calvarial defects and analyzed by microcomputed tomography for bone formation after four and eight weeks. These results demonstrate that SIM loaded PLLA/gelatin/HAp-(βCD) scaffolds promote significantly higher ALP activity, mineralization, osteogenic gene expression, and bone regeneration than control scaffolds. This suggests the potential application of this material toward bone tissue engineering.

An estimated 16 million people in the United States have coronary artery disease (CAD), and approximately 325,000 people die annually from cardiac arrest. About two-thirds of unexpected cardiac deaths occur without prior recognition of cardiac disease. A vast majority of these deaths are attributable to the rupture of 'vulnerable atherosclerotic plaques'. Clinically, plaque vulnerability is typically assessed through imaging techniques, and ruptured plaques leading to acute myocardial infarction are treated through angioplasty or stenting. Despite significant advances, it is clear that current imaging methods are insufficiently capable for elucidating plaque composition--which is a key determinant of vulnerability. Further, the exciting improvement in the treatment of CAD afforded by stenting procedures has been buffered by significant undesirable host-implant effects, including restenosis and late thrombosis. Nanotechnology has led to some potential solutions to these problems by yielding constructs that interface with plaque cellular components at an unprecedented size scale. By leveraging the innate ability of macrophages to phagocytose nanoparticles, contrast agents can now be targeted to plaque inflammatory activity. Improvements in nano-patterning procedures have now led to increased ability to regenerate tissue isotropy directly on stents, enabling gradual regeneration of normal, physiologic vascular structures. Advancements in immunoassay technologies promise lower costs for biomarker measurements, and in the near future, may enable the addition of routine blood testing to the clinician's toolbox--decreasing the costs of atherosclerosis-related medical care. These are merely three examples among many stories of how nanotechnology continues to promise advances in the diagnosis and treatment of vulnerable atherosclerotic plaques.

Characterization of the degradation mechanism of polymeric scaffolds and delivery systems for regenerative medicine is essential to assess their clinical applicability. Key performance criteria include induction of a minimal, transient inflammatory response and controlled degradation to soluble non-cytotoxic breakdown products that are cleared from the body by physiological processes. Scaffolds fabricated from biodegradable poly(ester urethane)s (PEURs) undergo controlled degradation to non-cytotoxic breakdown products and support the ingrowth of new tissue in preclinical models of tissue regeneration. While previous studies have shown that PEUR scaffolds prepared from lysine-derived polyisocyanates degrade faster under in vivo compared to in vitro conditions, the degradation mechanism is not well understood. In this study, we have shown that PEUR scaffolds prepared from lysine triisocyanate (LTI) or a trimer of hexamethylene diisocyanate (HDIt) undergo hydrolytic, esterolytic, and oxidative degradation. Hydrolysis of ester bonds to yield α-hydroxy acids is the dominant mechanism in buffer, and esterolytic media modestly increase the degradation rate. While HDIt scaffolds show a modest (

Human mesenchymal stem cells (hMSCs) have been widely studied for therapeutic development in tissue engineering and regenerative medicine. They can be harvested from human donors via tissue biopsies, such as bone marrow aspiration, and cultured to reach clinically relevant cell numbers. However, an unmet issue lies in the fact that the hMSC donors for regenerative therapies are more likely to be of advanced age. Their stem cells are not as potent compared to those of young donors, and continue to lose healthy, stemness-related activities when the hMSCs are serially passaged in tissue culture plates. Here, we have developed a cheap, scalable, and effective copolymer film to culture hMSCs obtained from aged human donors over several passages without loss of reactive oxygen species (ROS) handling or differentiation capacity. Assays of cell morphology, reactive oxygen species load, and differentiation potential demonstrate the effectiveness of copolymer culture on reduction in senescence-related activities of aging donor-derived hMSCs that could hinder the therapeutic potential of autologous stem cell therapies.

Stem cells are a promising cell source for regenerative medicine due to their differentiation and self-renewal capacities. In the field of regenerative medicine and tissue engineering, a variety of biomedical technologies have been tested to improve proangiogenic activities of stem cells. However, their therapeutic effect is found to be limited in the clinic because of cell loss, senescence, and insufficient therapeutic activities. To address this type of issue, advanced techniques for biomaterial synthesis and fabrication have been approached to mimic proangiogenic microenvironment and to direct proangiogenic activities. This review highlights the types of polymers and design strategies that have been studied to promote proangiogenic activities of stem cells. In particular, scaffolds, hydrogels, and surface topographies, as well as insight into their underlying mechanisms to improve proangiogenic activities are the focuses. The strategy to promote angiogenic activities of hMSCs by controlling substrate repellency is introduced, and the future direction is proposed.

We have developed a novel approach combining high information and high throughput analysis to characterize cell adhesive responses to biomaterial substrates possessing gradients in surface topography. These gradients were fabricated by subjecting thin film blends of tyrosine-derived polycarbonates, i.e. poly(DTE carbonate) and poly(DTO carbonate) to a gradient temperature annealing protocol. Saos-2 cells engineered with a green fluorescent protein (GFP) reporter for farnesylation (GFP-f) were cultured on the gradient substrates to assess the effects of nanoscale surface topology and roughness that arise during the phase separation process on cell attachment and adhesion strength. The high throughput imaging approach allowed us to rapidly identify the “global” and “high content” structure-property relationships between cell adhesion and biomaterial properties such as polymer chemistry and topography. This study found that cell attachment and spreading increased monotonically with DTE content and were significantly elevated at the position with intermediate regions corresponding to the highest “gradient” of surface roughness, while GFP-f farnesylation intensity descriptors were sensitively altered by surface roughness, even in cells with comparable levels of spreading.

A 3D microvascularized gelatin hydrogel is produced using thermoresponsive sacrificial poly(N-isopropylacrylamide) (PNIPAM) microfibers. The capillary-like microvascular network allows constant perfusion of media throughout the thick hydrogel, and signifcantly improves the viability of human neonatal dermal fibroblasts encapsulated within the gel at a high density.

Despite recent advances in biomimetic substrates, there is still only limited understanding of how the extracellular matrix (ECM) functions in the maintenance of cardiomyocyte (CM) phenotype. In this study, we designed electrospun substrates inspired by morphologic features of non-failing and failing human heart ECM, and examined how these substrates regulate phenotypes of adult and neonatal rat ventricular CMs (ARVM and NRVM, respectively). We found that poly(e-caprolactone) fiber substrates designed to mimic the organized ECM of a non-failing human heart maintained healthy CM phenotype (evidenced by cell morphology, organized actin/myomesin bands and expression of β-MYH7 and SCN5A.1 and SCN5A.2) compared to both failing heart ECM-mimetic substrates and tissue culture plates. Moreover, culture of ARVMs and NRVMs on aligned substrates showed differences in m- and z-line alignment; with ARVMs aligning parallel to the ECM fibers and the NRVMs aligning perpendicular to the fibers. The results provide new insight into cardiac tissue engineering by illustrating the importance models that mimic the cardiac ECM microenvironment in vitro.

Because of their potential to regenerate tissues and organs, stem cells garner extensive interest worldwide for treating a wide range of degenerative diseases. In numerous efforts, a variety of stem cell formats have been considered for therapeutic purposes to combat such pathologies, one being vascular-related diseases. In particular, the prevalence of peripheral artery disease (PAD) has steadily increased with the growth of the aging population in many first-world countries. Considering this disturbing trend as well as the obesity epidemic and the ballooning population growth in third-world nations, the burden of PAD is expected to increase worldwide to alarming levels in the coming decades. The advent of stem cell treatments could stymie this burden by alleviating the complications and improving upon the less-than-satisfactory outcomes from current standard-of-care surgical/pharmacological interventions for PAD. This chapter reviews the relevant, cutting-edge clinical and animal model research efforts in the field and explores the remaining questions as they pertain to convergence technologies that may provide the potential for stem cells to reverse PAD-induced tissue damage. Harnessing and translating this potential to create more viable and efficacious PAD treatments should be of paramount global and public health concern.

Primary dilated cardiomyopathy (DCM) is a non-ischemic heart disease with impaired pumping function of the heart. In this study, we used human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) from a healthy volunteer and a primary DCM patient to investigate the impact of DCM on iPSC-CMs׳ responses to different types of anisotropic strain. A bioreactor system was established that generates cardiac-mimetic forces of 150 kPa at 5% anisotropic cyclic strain and 1 Hz frequency. After confirming cardiac induction of the iPSCs, it was determined that fibronectin was favorable to other extracellular matrix protein coatings (gelatin, laminin, vitronectin) in terms of viable cell area and density, and was therefore selected as the coating for further study. When iPSC-CMs were exposed to three strain conditions (no strain, 5% static strain, and 5% cyclic strain), the static strain elicited significant induction of sarcomere components in comparison to other strain conditions. However, this induction occurred only in iPSC-CMs from a healthy volunteer ("control iPSC-CMs"), not in iPSC-CMs from the DCM patient ("DCM iPSC-CMs"). The donor type also significantly influenced gene expressions of cell-cell and cell-matrix interaction markers in response to the strain conditions. Gene expression of connexin-43 (cell-cell interaction) had a higher fold change in healthy versus diseased iPSC-CMs under static and cyclic strain, as opposed to integrins α-5 and α-10 (cell-matrix interaction). In summary, our iPSC-CM-based study to model the effects of different strain conditions suggests that intrinsic, genetic-based differences in the cardiomyocyte responses to strain may influence disease manifestation in vivo.

Thermo-responsive shape memory polymers (SMPs) can be programmed to fit into small-bore incisions and recover their functional shape upon deployment in the body. This property is of significant interest for developing the next generation of minimally-invasive medical devices. To be used in such applications, SMPs should exhibit adequate mechanical strengths that minimize adverse compliance mismatch-induced host responses (e.g. thrombosis, hyperplasia), be biodegradable, and demonstrate switch-like shape recovery near body temperature with favorable biocompatibility. Combinatorial approaches are essential in optimizing SMP material properties for a particular application. In this study, a new class of thermo-responsive SMPs with pendant, photocrosslinkable allyl groups, x%poly(e-caprolactone)-co-y%(α-allyl carboxylate e-caprolactone) (x%PCL-y%ACPCL), are created in a robust, facile manner with readily tunable material properties. Thermomechanical and shape memory properties can be drastically altered through subtle changes in allyl composition. Molecular weight and gel content can also be altered in this combinatorial format to fine-tune material properties. Materials exhibit highly elastic, switch-like shape recovery near 37 °C. Endothelial compatibility is comparable to tissue culture polystyrene (TCPS) and 100%PCL in vitro and vascular compatibility is demonstrated in vivo in a murine model of hindlimb ischemia, indicating promising suitability for vascular applications. Statement of Significance With the ongoing thrust to make surgeries minimally-invasive, it is prudent to develop new biomaterials that are highly compatible and effective in this workflow. Thermo-responsive shape memory polymers (SMPs) have great potential for minimally-invasive applications because SMP medical devices (e.g. stents, grafts) can fit into small-bore minimally-invasive surgical devices and recover their functional shape when deployed in the body. To realize their potential, it is imperative to devise combinatorial approaches that enable optimization of mechanical, SM, and cellular responses for a particular application. In this study, a new class of thermo-responsive SMPs is created in a robust, facile manner with readily tunable material properties. Materials exhibit excellent, switch-like shape recovery near body temperature and promising biocompatibility for minimally-invasive vascular applications.

Induced pluripotent stem cells (iPSCs) from patients’ somatic tissues provide a viable source to create autologous cardiomyocytes (CMs) for potential cardiac-related cell therapies. However, a gap between the generation of iPSC-derived cardiomyocytes (iPSC-CMs) and the successful intra-cardiac engraftment of the cells to restore heart function remains to be bridged. Clinical data reporting engraftment of cells within human heart tissue has not been without its challenges, with significant cell loss from the site of delivery due to the physical stress of the cardiac cycle and the hostile inflammatory response within the infarct zone.[1–3] Hydrogels have been proven to support the survival of multiple cell types and have served as a platform for cell transplantation.[4, 5] Yet the use of tissue-adhesive, temperature-sensitive hydrogels to deliver iPSC-derived cardiomyocytes to infarcted heart remains to be explored. Therefore, we developed a polymer hydrogel to encapsulate, deliver, and integrate iPSC-CMs into infarcted myocardium to restore heart function. A temperature-sensitive biodegradable copolymer (polyethylene glycol-co-poly-e-caprolactone (PEG-PCL)) was synthesized [6] and conjugated with a collagen-binding peptide (SYIRIADTNIT). [7] The polymer was soluble in aqueous solutions at room temperature and underwent solution-to-gel transition at 37°C (Fig. 1 a,b).[6] As the peptide-modified polymer had a strong affinity to collagen I in vitro (Fig. 1c), it was expected that it would significantly increase the binding of the hydrogel to an infarcted heart, thus immobilizing iPSC-CMs within the damaged myocardium. Functional, beating cardiomyocytes were derived from patient fibroblast-derived iPSCs using a “Matrigel sandwich” method.[8] Cardiac differentiation was confirmed by fluorescence-activated cell sorting (FACS) and by immunostaining with known cardiac markers cardiac troponin T (cTNT), ryanodine receptor 2 (RYR) and α-actinin (Fig. 1f). The iPSC-CMs encapsulated in the polymer hydrogel at 37°C for two weeks maintained their viability (Fig. 1g) and cardiac phenotype, as evidenced by strong expression of troponin T and Nkx2.5 (Fig. 1h); thus, PEG-PCL does not appear to have obvious toxic effects on iPSC-CMs. Fig. 1 PEG-PCL copolymer was (a) dissolved in PBS at RT and (b) gelled at 37°C within 5 min (Sol-gel transition). Collagen-binding study was performed by adding peptide-modified polymer to collagen-coated surface at 37°C, and unbound polymer ... Engraftment of iPSC-CMs into infarcted myocardium using the peptide-modified hydrogel and its impact on infarcted heart function and structure were assessed with a rat myocardial infarction (MI) model. All animal surgery and animal care were approved by the Institutional Animal Care and Use Committee (IACUC) at Vanderbilt University (protocol: M/12/074). The left anterior descending (LAD) coronary artery of nude rats was ligated to induce MI. At 30 minutes post-MI, iPSC-CMs alone, or modified copolymer solution with or without iPSC-CMs (2–4 million/rat) were injected around the infarct border zone. A negative control group received the LAD ligation and phosphate-buffered saline (PBS) injection without cells or copolymer. At two weeks post-injection, heart dimensions and functional output were assessed by echocardiography. All groups had ventricular dilation and reduced fractional shortening (FS) (Fig. 2). However, rats treated with iPSC-CM-encapsulated copolymer demonstrated significantly less decline in FS (Δ= −6.37±0.49%) compared to other groups (Δ= −12.77±2.04%, −11.44±2.04% and −12.65±1.53% for PBS control, iPSC-CM only, and polymer only groups, respectively (Fig. 2a). p=0.016 vs. PBS, p=0.021 vs. iPSC-CM only, and p=0.005 vs. polymer only). Overall, the iPSC-CM plus polymer group demonstrated 50.1%, 28.2% and 49.6% improvement in LV systolic function over PBS, iPSC-CM only and polymer only groups (Fig. 2b). Moreover, rats treated with iPSC-CM plus polymer demonstrated a trend toward less LV enlargement (Δ= 15.07±3.24%) compared to other groups (Δ=24.44±3.99%, 25.02±2.03% and 23.17±4.51% for PBS control, iPSC-CM only, and polymer only groups, respectively; Fig. 2c) although this reached statistical significance only in comparison to the iPSC-CM group (p=0.032). Overall, iPSC-CM plus polymer group demonstrated 38.3%, 39.8% and 35.0% less LV enlargement over PBS, iPSC-CM only and polymer only groups, suggesting that iPSC-CM encapsulated in polymer curtailed adverse ventricular remodeling better than other treatment modalities. Fig. 2 The effects of hydrogel-encapsulated iPSC-CMs on left ventricle function and remodeling. (a–c) Echocardiography was performed before the ligation of rat LAD coronary arteries (baseline) and again 2 weeks post-delivery (n=5 rats per group). (a, ... Histological examination of the hearts was performed, and the LV anterior free wall thickness was measured using ImageJ and averaged from 3 randomly selected regions in each rat heart. Result demonstrated that, in addition to LV chamber enlargement, the LAD ligation resulted in dramatic thinning and significant fibrosis of the LV anterior free wall at two weeks in control groups (Fig. 2e). In contrast, heart injected with polymer-encapsulated iPSC-CMs had smaller LV chamber, thicker LV free wall and less fibrosis (Fig. 2e). Overall, hearts in the iPSC-CM plus polymer group were significantly thicker than all other groups; the average LV anterior wall thickness of cell plus polymer group was 2.46±0.06mm, compared with 0.48±0.07, 0.35±0.05 and 0.39±0.02mm in PBS, cell only and polymer only groups, respectively (Fig. 2d, p