Abstract The implantation of non-biological materials, including scaffolds for tissue engineering, ubiquitously leads to a foreign body response (FBR). We recently reported that this response ...negatively impacts fibroblasts encapsulated within a synthetic hydrogel and in turn leads to a more severe FBR, suggesting a cross-talk between encapsulated cells and inflammatory cells. Given the promise of mesenchymal stem cells (MSCs) in tissue engineering and recent evidence of their immunomodulatory properties, we hypothesized that MSCs encapsulated within poly(ethylene glycol) (PEG) hydrogels will attenuate the FBR. In vitro , murine MSCs encapsulated within PEG hydrogels attenuated classically activated primary murine macrophages by reducing gene expression and protein secretion of pro-inflammatory cytokines, most notably tumor necrosis factor-α. Using a COX2 inhibitor, prostaglandin E2 (PGE2) was identified as a mediator of MSC immunomodulation of macrophages. In vivo , hydrogels laden with MSCs, osteogenically differentiating MSCs, or no cells were implanted subcutaneously into C57BL/6 mice for 28 days to assess the impact of MSCs on the fibrotic response of the FBR. The presence of encapsulated MSCs reduced fibrous capsule thickness compared to acellular hydrogels, but this effect diminished with osteogenic differentiation. The use of MSCs prior to differentiation in tissue engineering may therefore serve as a dynamic approach, through continuous cross-talk between MSCs and the inflammatory cells, to modulate macrophage activation and attenuate the FBR to implanted synthetic scaffolds thus improving the long-term tissue engineering outcome.
Fibroblasts are a major cell population that perform critical functions in the wound healing process. In response to injury, they proliferate and migrate into the wound space, engaging in ...extracellular matrix (ECM) production, remodeling, and contraction. However, there is limited knowledge of how fibroblast functions are altered in diabetes. To address this gap, several state-of-the-art microscopy techniques were employed to investigate morphology, migration, ECM production, 2D traction, 3D contraction, and cell stiffness. Analysis of cell-derived matrix (CDM) revealed that diabetic fibroblasts produce thickened and less porous ECM that hindered migration of normal fibroblasts. In addition, diabetic fibroblasts were found to lose spindle-like shape, migrate slower, generate less traction force, exert limited 3D contractility, and have increased cell stiffness. These changes were due, in part, to a decreased level of active Rac1 and a lack of co-localization between F-actin and Waskott-Aldrich syndrome protein family verprolin homologous protein 2 (WAVE2). Interestingly, deletion of thrombospondin-2 (TSP2) in diabetic fibroblasts rescued these phenotypes and restored normal levels of active Rac1 and WAVE2-F-actin co-localization. These results provide a comprehensive view of the extent of diabetic fibroblast dysfunction, highlighting the regulatory role of the TSP2-Rac1-WAVE2-actin axis, and describing a new function of TSP2 in regulating cytoskeleton organization.
Decellularized biologic scaffolds are gaining popularity over synthetic biomaterials as naturally derived materials capable of promoting improved healing. Nevertheless, the most widely used biologic ...material – acellular dermal matrix (ADM) – exhibits slow repopulation and remodeling, which prevents integration. Additionally, engineering control of these materials is limited because they require a natural source for their production. In the current report, we demonstrate the feasibility of using genetically engineered animals to create decellularized biologic scaffolds with favorable extracellular matrix (ECM) properties. Specifically, we utilized skin from thrombospondin (TSP)-2 KO mice to derive various decellularized products. Scanning electron microscopy and mechanical testing showed that TSP-2 KO ADM exhibited an altered structure and a reduction in elastic modulus and ultimate tensile strength, respectively. When a powdered form of KO ADM was implanted subcutaneously, it was able to promote enhanced vascularization over WT. Additionally, when implanted subcutaneously, intact slabs of KO ADM were populated by higher number of host cells when compared to WT. In vitro studies confirmed the promigratory properties of KO ADM. Specifically, degradation products released by pepsin digestion of KO ADM induced greater cell migration than WT. Moreover, cell-derived ECM from TSP-2 null fibroblasts was more permissive to fibroblast migration. Finally, ADMs were implanted in a diabetic wound model to examine their ability to accelerate wound healing. KO ADM exhibited enhanced remodeling and vascular maturation, indicative of efficient integration. Overall, we demonstrate that genetic manipulation enables engineered ECM-based materials with increased regenerative potential.
Human‐induced pluripotent stem cell‐derived vascular smooth muscle cells (hiPSC‐VSMCs) with proangiogenic properties have huge therapeutic potential. While hiPSC‐VSMCs have already been utilized for ...wound healing using a biomimetic collagen scaffold, an in situ forming hydrogel mimicking the native environment of skin offers the promise of hiPSC‐VSMC mediated repair and regeneration. Herein, the impact of a collagen type‐I‐hyaluronic acid (HA) in situ hydrogel cross‐linked using a polyethylene glycol‐based cross‐linker on hiPSC‐VSMCs viability and proangiogenic paracrine secretion was investigated. Our study demonstrated increases in cell viability, maintenance of phenotype and proangiogenic growth factor secretion, and proangiogenic activity in response to the conditioned medium. The optimally cross‐linked and functionalized collagen type‐I/HA hydrogel system developed in this study shows promise as an in situ hiPSC‐VSMC carrier system for wound regeneration.
An in situ collagen‐HA hydrogel was characterized as a carrier of hiPSC‐VSMCs for wound healing applications. The hydrogel system enhanced cell viability, maintained the phenotype and proangiogenic paracrine secretion of hiPSC‐VSMCs. In addition, the conditioned medium from the in situ hydrogels promoted angiogenesis.
Hydrogels composed of solubilized decellularized extracellular matrix (ECM) are attractive materials because they combine the complexity of native ECM with injectability and ease of use. ...Nevertheless, these materials are typically only tunable by altering the concentration, which alters the ligand landscape, or by incorporating synthetic components, which can result in an unfavorable host response. Herein, we demonstrate the fabrication of genetically tunable ECM-derived materials, by utilizing wild type (WT) and (thrombospondin-2 knockout) TSP-2 KO decellularized skins to prepare hydrogels. The resulting materials exhibited distinct mechanical properties characterized by rheology and different concentrations of collagens when characterized by quantitative proteomics. Mixtures of the gels achieved intermediate effects between the WT and the KO, permitting tunability of the gel properties. In vivo, the hydrogels exhibited tunable cell invasion with a correlation between the content of TSP-2 KO hydrogel and the extent of cell invasion. Additionally, TSP-2 KO hydrogels significantly improved diabetic wound healing at 10 and 21 days. Furthermore, hydrogels derived from genetically engineered in vitro cell-derived matrix mimicked the trends observed for tissue-derived matrix, providing a platform for faster screening of novel manipulations and easier clinical translation. Overall, we demonstrate that genetic engineering approaches impart tunability to ECM-based hydrogels and can result in materials capable of enhanced regeneration.
The biggest challenge in current isolation methods for lipid bilayer‐encapsulated vesicles, such as exosomes, secretory, and synthetic vesicles, lies in the absence of a unified approach that ...seamlessly delivers high purity, yield, and scalability for large‐scale applications. To address this gap, an innovative method is developed that utilizes photosensitive lipid nanoprobes for the efficient isolation of vesicles and sorting them into subpopulations based on size. The photosensitive component in the probe undergoes cleavage upon exposure to light, facilitating the release of vesicles in their near‐native form. The method demonstrates a superior ability in isolating high purity extracellular vesicles from complex biological media and separating them into size‐based subpopulations within 1 h, achieving more efficiency and purity than ultracentrifugation. Furthermore, this method's cost‐effectiveness and rapid enrichment of the vesicles align with demands for large‐scale isolation and downstream analyses of nucleic acids and proteins. The method opens new avenues in exploring, analyzing, and utilizing synthetic and extracellular vesicle subpopulations in various biomedical applications, including diagnostics, therapeutic delivery, and biomarker discovery.
The photosensitive lipid nanoprobe‐based isolation method transforms synthetic and extracellular vesicle research, offering a rapid, scalable, and universally applicable technique with higher purity and recovery rates than existing methods. The 3‐step process efficiently isolates vesicle subpopulations from diverse biological sources. This advancement holds significant potential in large‐scale extracellular vesicle research for diagnostics, disease mechanisms, and therapeutic applications.
Biomaterials are essential to modern medicine as components of reconstructive implants, implantable sensors, and vehicles for localized drug delivery. Advances in biomaterials have led to progression ...from simply making implants that are nontoxic to making implants that are specifically designed to elicit particular functions within the host. The interaction of implants and the extracellular matrix during the foreign body response is a growing area of concern for the field of biomaterials, because it can lead to implant failure. Expression of matricellular proteins is modulated during the foreign body response and these proteins interact with biomaterials. The design of biomaterials to specifically alter the levels of matricellular proteins surrounding implants provides a new avenue for the design and fabrication of biomimetic biomaterials.
•Matricellular proteins participate in the foreign body response to biomaterials.•Modulation of matricellular proteins or their components can alter the FBR.•Biomimetic materials can incorporate matricellular proteins or their components.•Matricellular proteins retained in decellularized ECM influence cell function.
Novel biological vascular conduits, such as decellularized tissue engineered vascular grafts (TEVGs) are hindered by high thrombogenicity. To mimic the antithrombogenic surface of native vessels with ...a continuous glycosaminoglycan layer that is present on endothelial cells (ECs), a hyaluronic acid (HA) modified surface is established, to effectively shield blood platelets from collagen‐triggered activation. Using the amine groups present on 4 mm diameter decellularized TEVGs, a continuous HA hydrogel coating is built via a bifunctional thiol‐reactive cross‐linker, thereby avoiding nonspecific collagen matrix cross‐linking. The HA hydrogel layer recreates a luminal wall, “hiding” exposed collagen from the bloodstream. In vitro blood tests show that adhered platelets, fibrinogen absorption, and fibrin formation on HA‐coated decellularized TEVGs are significantly lower than on uncoated decellularized TEVGs. The HA surface also inhibits macrophage adhesion in vitro. HA‐coated decellularized syngeneic rat aortae (≈1.5 mm diameter), and TEVGs in rat and canine models, respectively, are protected from aggressive thrombus formation, and preserve normal blood flow. Re‐endothelialization is also observed. HA‐coated TEVGs may be an off‐the‐shelf small‐diameter vascular graft with dual benefits: antithrombogenic protection and promotion of endothelium.
To reduce thrombosis risk on small diameter (<6 mm) vascular grafts, hyaluronic acid is coated on the lumen of decellularized tissue engineered vascular grafts. This layer effectively shields platelets from collagen‐triggered activation, while allowing endothelial repopulation over time in vivo. Hence, hyaluronic acid–coated grafts may be an off‐the‐shelf small‐diameter vascular graft with dual benefits: antithrombogenic protection and promotion of endothelium.
Nanomaterials (NMs) have revolutionized multiple aspects of medicine by enabling novel sensing, diagnostic, and therapeutic approaches. Advancements in processing and fabrication have also allowed ...significant expansion in the applications of the major classes of NMs based on polymer, metal/metal oxide, carbon, liposome, or multi-scale macro-nano bulk materials. Concomitantly, concerns regarding the nanotoxicity and overall biocompatibility of NMs have been raised. These involve putative negative effects on both patients and those subjected to occupational exposure during manufacturing. In this review, we describe the current state of testing of NMs including those that are in clinical use, in clinical trials, or under development. We also discuss the cellular and molecular interactions that dictate their toxicity and biocompatibility. Specifically, we focus on the reciprocal interactions between NMs and host proteins, lipids, and sugars and how these induce responses in immune and other cell types leading to topical and/or systemic effects.
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