N-desulfated and reacetylated modification of heparin modulates macrophage polarization

Construction of bFGF/heparin and Fe3O4 nanoparticles functionalized scaffolds aiming at vascular repair and magnetic resonance imaging monitoring

This work develops a bioactive basic fibroblast growth factor (bFGF)/heparin and Fe3O4 nanoparticles (NPs) trifunctionalized degradable construct with the potential of using as a vascular tissue engineering scaffold with the aim of improving vascular repair and regeneration therapy. The covalent modification of heparin onto the poly(lactic acid) (PLA)-gelatin (Gel)-Fe3O4 (PGF) scaffold improves the hydrophilicity of the scaffold. Furthermore, the electrostatic adsorption of bFGF on heparin allows for a more consistent and prolonged release of bFGF in situ, hence increasing the stability and effectiveness of bFGF around the surrounding vascular tissues. The sustained release of bFGF promotes the M2 macrophage polarization, and adhesion and migration of macrophages and endothelial cells (ECs), providing a stable and favorable microenvironment for vascular regeneration. Furthermore, the covalently modified heparin minimizes platelet adhesion on the scaffold surface, potentially contributing to the long-term patency of the vascular tissue engineering scaffold. Including Fe3O4 NPs in the scaffold delays degradation and provides an in vivo magnetic resonance imaging (MRI) effect to monitor the scaffold's location and in vivo degradation. Furthermore, the mild photothermal effect of Fe3O4 NPs plays a facilitating role in bFGF release, immune modulation, and ECs manipulation, therefore contributary to the vascular tissue reconstruction.

Targeting Macrophage Polarization for Reinstating Homeostasis following Tissue Damage

Tissue regeneration and remodeling involve many complex stages. Macrophages are critical in maintaining micro-environmental homeostasis by regulating inflammation and orchestrating wound healing. They display high plasticity in response to various stimuli, showing a spectrum of functional phenotypes that vary from M1 (pro-inflammatory) to M2 (anti-inflammatory) macrophages. While transient inflammation is an essential trigger for tissue healing following an injury, sustained inflammation (e.g., in foreign body response to implants, diabetes or inflammatory diseases) can hinder tissue healing and cause tissue damage. Modulating macrophage polarization has emerged as an effective strategy for enhancing immune-mediated tissue regeneration and promoting better integration of implantable materials in the host. This article provides an overview of macrophages' functional properties followed by discussing different strategies for modulating macrophage polarization. Advances in the use of synthetic and natural biomaterials to fabricate immune-modulatory materials are highlighted. This reveals that the development and clinical application of more effective immunomodulatory systems targeting macrophage polarization under pathological conditions will be driven by a detailed understanding of the factors that regulate macrophage polarization and biological function in order to optimize existing methods and generate novel strategies to control cell phenotype.

Heparinized Acellular Hydrogels for Magnetically Induced Wound Healing Applications

The control of angiogenesis has the potential to be used for regulation of several pathological and physiological processes, which can be instrumental on the development of anticancer and wound healing therapeutical approaches. In this study, mesenchymal stem/stromal cells (MSCs) were seeded on magnetic-responsive gelatin, with or without heparin functionalization, and exposed to a static 0.08 T magnetic field (MF), for controlling their anti-inflammatory and angiogenic activity, with the aim of accelerating tissue healing. For the first time, it was examined how the amount of heparin and magnetic nanoparticles (MNPs) distributed on gelatin scaffolds affected the mechanical properties of the hydrogels and the morphology, proliferation, and secretome profiling of MSCs. The findings demonstrated that the addition of MNPs and heparin affects the hydrogel swelling capacity and renders distinct MSC proliferation rates. Additionally, MF acts as a topographical cue to guide MSCs alignment and increases the level of expression of specific genes and proteins that promote angiogenesis. The results also suggested that the presence of higher amounts of heparin (10 μg/cm3) interferes with the secretion and limits the capacity of angiogenic factors to diffuse through the hydrogel and into the culture medium. Ultimately, this study shows that acellular heparinized hydrogels efficiently retain the angiogenic growth factors released by magnetically stimulated MSCs thus rendering superior wound contraction (55.8% ± 0.4%) and cell migration rate (49.4% ± 0.4%), in comparison to nonheparinized hydrogels (35.2% ± 0.7% and 37.8% ± 0.7%, respectively). Therefore, these heparinized magnetic hydrogels can be used to facilitate angiogenesis in various forms of tissue damage including bone defects, skin wounds, and cardiovascular diseases, leading to enhanced tissue regeneration.

TAM-Hijacked Immunoreaction Rescued by Hypoxia-Pathway-Intervened Strategy for Enhanced Metastatic Cancer Immunotherapy

Immunotherapy is regarded as a prospective strategy against metastatic cancer. However, tumor-associated macrophages (TAMs), which accumulate in hypoxic tumor microenvironment, reduce the effectiveness of immunotherapy by blocking or "hijacking" the initiation of the immune response. Here, a novel tumor-targeted nanoplatform loaded with hypoxia-pathway-intervened docosahexaenoic acid (DHA) and chemotherapeutic drug carfilzomib (CFZ) is developed, which realizes the rescue of TAM-hijacked immune response and effective metastatic cancer immunotherapy. DHA is conjugated to fucoidan (Fuc) via a reduction cleavable selenylsulfide bond (SSe) for micelle preparation, and CFZ is encapsulated in the hydrophobic cores of micelles. The functionalized nanoplatforms (Fuc─SSe─DHA (FSSeD)-CFZs) induce immunogenic cell death, inhibit hypoxia-inducible factor-1α expression, and improve immunosuppression by TAM suppression. FSSeD-CFZs enhance immune response against primary tumor development and metastasis formation. In brief, the novel rescue strategy for TAM-hijacked immunoreaction by inhibiting hypoxia pathway has the potential and clinically translational significance for enhanced metastatic cancer immunotherapy.

Small-diameter PCL/PU vascular graft modified with heparin-aspirin compound for preventing the occurrence of acute thrombosis

The occurrence of acute thrombosis, directly related to platelet aggregation and coagulant system, is a considerable reason for the failure of small-diameter vascular grafts. Heparin is commonly used as a functional molecule for graft modification due to the strong anticoagulant effect. Unfortunately, heparin cannot directly resist the adhesion and aggregation of platelets. Therefore, we have prepared a heparin-aspirin compound by coupling heparin with aspirin, an antiplatelet drug, and covalently grafted it onto the surface of polycaprolactone/polyurethane composite tube. In this way, the graft not only showed a dual function of both anticoagulation and antiplatelet, but also effectively avoided the rapid drug release and excessive toxicity to other organs caused by simple blending the medicine with material matrix. The compound retained the original function of heparin, showing good hydrophilicity and biocompatibility, which could promote the adhesion and proliferation of endothelial cells (ECs) and facilitate the process of tissue regeneration. What's more, the compound showed more effective than heparin in reducing platelet activation and preventing thrombosis. The graft modified by this compound maintained completely unobstructed for one month of implantation, while severe obstruction or stenosis occurred in PCL/PU and PCL/PU-Hep lumen at the first week, verifying the effect of the compound on preventing acute thrombosis. In general, this study proposed a designing method for small-diameter vascular graft which could prevent acute thrombosis and promote intimal construction.