Local decorin delivery via hyaluronic acid microrods improves cardiac performance, ventricular remodeling after myocardial infarction.

Heart failure (HF) remains a global public health burden and often results following myocardial infarction (MI). Following injury, cardiac fibrosis forms in the myocardium which greatly hinders cellular function, survival, and recruitment, thus severely limits tissue regeneration. Here, we leverage biophysical microstructural cues made of hyaluronic acid (HA) loaded with the anti-fibrotic proteoglycan decorin to more robustly attenuate cardiac fibrosis after acute myocardial injury. Microrods showed decorin incorporation throughout the entirety of the hydrogel structures and exhibited first-order release kinetics in vitro. Intramyocardial injections of saline (n = 5), microrods (n = 7), decorin microrods (n = 10), and free decorin (n = 4) were performed in male rat models of ischemia-reperfusion MI to evaluate therapeutic effects on cardiac remodeling and function. Echocardiographic analysis demonstrated that rats treated with decorin microrods (5.21% ± 4.29%) exhibited significantly increased change in ejection fraction (EF) at 8 weeks post-MI compared to rats treated with saline (-4.18% ± 2.78%, p < 0.001) and free decorin (-3.42% ± 1.86%, p < 0.01). Trends in reduced end diastolic volume were also identified in decorin microrod-treated groups compared to those treated with saline, microrods, and free decorin, indicating favorable ventricular remodeling. Quantitative analysis of histology and immunofluorescence staining showed that treatment with decorin microrods reduced cardiac fibrosis (p < 0.05) and cardiomyocyte hypertrophy (p < 0.05) at 8 weeks post-MI compared to saline control. Together, this work aims to contribute important knowledge to guide rationally designed biomaterial development that may be used to successfully treat cardiovascular diseases.

Harnessing Biomaterials for Immunomodulatory-Driven Tissue Engineering.

Abstract: The immune system plays a crucial role during tissue repair and wound healing processes. Biomaterials have been leveraged to assist in this in situ tissue regeneration process to dampen the foreign body response by evading or suppressing the immune system. An emerging paradigm within regenerative medicine is to use biomaterials to influence the immune system and create a pro-reparative microenvironment to instigate endogenously driven tissue repair. In this review, we discuss recent studies that focus on immunomodulation of innate and adaptive immune cells for tissue engineering applications through four biomaterial-based mechanisms of action: biophysical cues, chemical modifications, drug delivery, and sequestration. These materials enable augmented regeneration in various contexts, including vascularization, bone repair, wound healing, and autoimmune regulation. While further understanding of immune-material interactions is needed to design the next generation of immunomodulatory biomaterials, these materials have already demonstrated great promise for regenerative medicine. Lay Summary: The immune system plays an important role in tissue repair. Many biomaterial strategies have been used to promote tissue repair, and recent work in this area has looked into the possibility of doing repair by tuning. Thus, we examined the literature for recent works showcasing the efficacy of these approaches in animal models of injuries. In these studies, we found that biomaterials successfully tuned the immune response and improved the repair of various tissues. This highlights the promise of immune-modulating material strategies to improve tissue repair.

Encapsulation of ß-NGF in injectable microrods for localized delivery accelerates endochondral fracture repair.

Introduction: Currently, there are no non-surgical FDA-approved biological approaches to accelerate fracture repair. Injectable therapies designed to stimulate bone healing represent an exciting alternative to surgically implanted biologics, however, the translation of effective osteoinductive therapies remains challenging due to the need for safe and effective drug delivery. Hydrogel-based microparticle platforms may be a clinically relevant solution to create controlled and localized drug delivery to treat bone fractures. Here, we describe poly (ethylene glycol) dimethacrylate (PEGDMA)-based microparticles, in the shape of microrods, loaded with beta nerve growth factor (ß-NGF) for the purpose of promoting fracture repair. Methods: Herein, PEGDMA microrods were fabricated through photolithography. PEGDMA microrods were loaded with ß-NGF and in vitro release was examined. Subsequently, bioactivity assays were evaluated in vitro using the TF-1 tyrosine receptor kinase A (Trk-A) expressing cell line. Finally, in vivo studies using our well-established murine tibia fracture model were performed and a single injection of the ß-NGF loaded PEGDMA microrods, non-loaded PEGDMA microrods, or soluble ß-NGF was administered to assess the extent of fracture healing using Micro-computed tomography (µCT) and histomorphometry. Results: In vitro release studies showed there is significant retention of protein within the polymer matrix over 168 hours through physiochemical interactions. Bioactivity of protein post-loading was confirmed with the TF-1 cell line. In vivo studies using our murine tibia fracture model show that PEGDMA microrods injected at the site of fracture remained adjacent to the callus for over 7 days. Importantly, a single injection of ß-NGF loaded PEGDMA microrods resulted in improved fracture healing as indicated by a significant increase in the percent bone in the fracture callus, trabecular connective density, and bone mineral density relative to soluble ß-NGF control indicating improved drug retention within the tissue. The concomitant decrease in cartilage fraction supports our prior work showing that ß-NGF promotes endochondral conversion of cartilage to bone to accelerate healing. Discussion: We demonstrate a novel and translational method wherein ß-NGF can be encapsulated within PEGDMA microrods for local delivery and that ß-NGF bioactivity is maintained resulting in improved bone fracture repair.

Transthyretin amyloid fibrils alter primary fibroblast structure, function, and inflammatory gene expression.

Age-related wild-type transthyretin amyloidosis (wtATTR) is characterized by systemic deposition of amyloidogenic fibrils of misfolded transthyretin (TTR) in the connective tissue of many organs. In the heart, this leads to cardiac dysfunction, which is a significant cause of age-related heart failure. The hypothesis tested is that TTR affects cardiac fibroblasts in ways that may contribute to fibrosis. When primary cardiac fibroblasts were cultured on TTR-deposited substrates, the F-actin cytoskeleton was disorganized, focal adhesion formation was decreased, and nuclear shape was flattened. Fibroblasts had faster collective and single-cell migration velocities on TTR-deposited substrates. In addition, fibroblasts cultured on microposts with TTR deposition had reduced attachment and increased proliferation above untreated. Transcriptomic and proteomic analyses of fibroblasts grown on glass covered with TTR showed significant upregulation of inflammatory genes after 48 h, indicative of progression in TTR-based diseases. Together, results suggest that TTR deposited in tissue extracellular matrix may affect the structure, function, and gene expression of cardiac fibroblasts. As therapies for wtATTR are cost-prohibitive and only slow disease progression, better understanding of cellular maladaptation may elucidate novel therapeutic targets.NEW & NOTEWORTHY Transthyretin (TTR) cardiac amyloidosis involves deposition of fibrils of misfolded TTR in the aging human heart, leading to cardiac dysfunction and heart failure. Our novel in vitro studies show that TTR fibrils alter primary cardiac fibroblast cytoskeletal and nuclear structure and focal adhesion formation. Furthermore, both fibrillar and tetrameric TTR significantly increased cellular migration velocity and caused upregulation of inflammatory genes determined by transcriptomic RNA and protein analysis. These findings may suggest new therapeutic approaches.

Theranostic biomaterials for tissue engineering.

Tissue engineering strategies, notably biomaterials, can be modularly designed and tuned to match specific patient needs. Although many challenges within tissue engineering remain, the incorporation of diagnostic strategies to create theranostic (combined therapy and diagnostic) biomaterials presents a unique platform to provide dual monitoring and treatment capabilities and advance the field toward personalized technologies. In this review, we summarize recent developments in this young field of regenerative theranostics and discuss the clinical potential and outlook of these systems from a tissue engineering perspective. As the need for precision and personalized medicines continues to increase to address diseases in all tissues in a patient-specific manner, we envision that such theranostic platforms can serve these needs.

Synthetic networks with tunable responsiveness, biodegradation, and molecular recognition for precision medicine applications.

Formulations and devices for precision medicine applications must be tunable and multiresponsive to treat heterogeneous patient populations in a calibrated and individual manner. We engineered modular poly(acrylamide-co-methacrylic acid) copolymers, cross-linked into multiresponsive nanogels with either a nondegradable or degradable disulfide cross-linker, that were customized via orthogonal chemistries to target biomarkers of an individual patient's disease or deliver multiple therapeutic modalities. Upon modification with functional small molecules, peptides, or proteins, these nanomaterials delivered methylene blue with environmental responsiveness, transduced visible light for photothermal therapy, acted as a functional enzyme, or promoted uptake by cells. In addition to quantifying the nanogels' composition, physicochemical characteristics, and cytotoxicity, we used a QCM-D method for characterizing nanomaterial degradation and a high-throughput assay for cellular uptake. In conclusion, we generated a tunable nanogel composition for precision medicine applications and new quantitative protocols for assessing the bioactivity of similar platforms.

Tunable poly(methacrylic acid-co-acrylamide) nanoparticles through inverse emulsion polymerization.

Environmentally responsive biomaterials have played key roles in the design of biosensors and drug delivery vehicles. Their physical response to external stimuli, such as temperature or pH, can transduce a signal or trigger the release of a drug. In this work, we designed a robust, highly tunable, pH-responsive nanoscale hydrogel system. We present the design and characterization of poly(methacrylic acid-co-acrylamide) hydrogel nanoparticles, crosslinked with methylenebisacrylamide, through inverse emulsion polymerization. The effects of polymerization parameters (i.e., identities and concentrations of monomer and surfactant) and polymer composition (i.e., weight fraction of ionic and crosslinking monomers) on the nanoparticles' bulk and environmentally responsive properties were determined. We generated uniform, spherical nanoparticles which, through modulation of crosslinking, exhibit a volume swelling of 1.77-4.07, relative to the collapsed state in an acidic environment. We believe our system has potential as a base platform for the targeted, injectable delivery of hydrophilic therapeutics. With equal importance, however, we hope that our systematic analysis of the individual impacts of polymerization and purification conditions on nanoparticle composition, morphology, and performance can be used to expedite the development of alternate hydrophilic nanomaterials for a range of biomedical applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1677-1686, 2018.

Student award for outstanding research winner in the Ph.D. category for the 2017 society for biomaterials annual meeting and exposition, april 5-8, 2017, Minneapolis, Minnesota: Characterization of protein interactions with molecularly imprinted hydrogels that possess engineered affinity for high isoelectric point biomarkers.

Molecularly imprinted polymers (MIPs) with selective affinity for protein biomarkers could find extensive utility as environmentally robust, cost-efficient biomaterials for diagnostic and therapeutic applications. In order to develop recognitive, synthetic biomaterials for prohibitively expensive protein biomarkers, we have developed a molecular imprinting technique that utilizes structurally similar, analogue proteins. Hydrogel microparticles synthesized by molecular imprinting with trypsin, lysozyme, and cytochrome c possessed an increased affinity for alternate high isoelectric point biomarkers both in isolation and plasma-mimicking adsorption conditions. Imprinted and non-imprinted P(MAA-co-AAm-co-DEAEMA) microgels containing PMAO-PEGMA functionalized polycaprolactone nanoparticles were net-anionic, polydisperse, and irregularly shaped. MIPs and control non-imprinted polymers (NIPs) exhibited regions of Freundlich and BET isotherm adsorption behavior in a range of non-competitive protein solutions, where MIPs exhibited enhanced adsorption capacity in the Freundlich isotherm regions. In a competitive condition, imprinting with analogue templates (trypsin, lysozyme) increased the adsorption capacity of microgels for cytochrome c by 162% and 219%, respectively, as compared to a 122% increase provided by traditional bulk imprinting with cytochrome c. Our results suggest that molecular imprinting with analogue protein templates is a viable synthetic strategy for enhancing hydrogel-biomarker affinity and promoting specific protein adsorption behavior in biological fluids. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1565-1574, 2017.