Functionalization of in vivo tissue-engineered living biotubes enhance patency and endothelization without the requirement of systemic anticoagulant administration

Versatile Design of NO-Generating Proteolipid Nanovesicles for Alleviating Vascular Injury

Vascular injury is central to the pathogenesis and progression of cardiovascular diseases, however, fostering alternative strategies to alleviate vascular injury remains a persisting challenge. Given the central role of cell-derived nitric oxide (NO) in modulating the endogenous repair of vascular injury, NO-generating proteolipid nanovesicles (PLV-NO) are designed that recapitulate the cell-mimicking functions for vascular repair and replacement. Specifically, the proteolipid nanovesicles (PLV) are versatilely fabricated using membrane proteins derived from different types of cells, followed by the incorporation of NO-generating nanozymes capable of catalyzing endogenous donors to produce NO. Taking two vascular injury models, two types of PLV-NO are tailored to meet the individual requirements of targeted diseases using platelet membrane proteins and endothelial membrane proteins, respectively. The platelet-based PLV-NO (pPLV-NO) demonstrates its efficacy in targeted repair of a vascular endothelium injury model through systemic delivery. On the other hand, the endothelial cell (EC)-based PLV-NO (ePLV-NO) exhibits suppression of thrombosis when modified onto a locally transplanted small-diameter vascular graft (SDVG). The versatile design of PLV-NO may enable a promising therapeutic option for various vascular injury-evoked cardiovascular diseases.

UV-Triggered Hydrogel Coating of the Double Network Polyelectrolytes for Enhanced Endothelialization

The left atrial appendage (LAA) occluder is an important medical device for closing the LAA and preventing stroke. The device-related thrombus (DRT) prevents the implantation of the occluder in exerting the desired therapeutic effect, which is primarily caused by the delayed endothelialization of the occluder. Functional coatings are an effective strategy for accelerating the endothelialization of occluders. However, the occluder surface area is particularly large and structurally complex, and the device is subjected to a large shear friction in the sheath during implantation, which poses a significant challenge to the coating. Herein, a hydrogel coating by the in situ UV-triggered polymerization of double-network polyelectrolytes is reported. The findings reveal that the double network and electrostatic interactions between the networks resulted in excellent mechanical properties of the hydrogel coating. The sulfonate and Arg-Gly-Asp (RGD) groups in the coating promoted hemocompatibility and endothelial growth of the occluder, respectively. The coating significantly accelerated the endothelialization of the LAA occluder in a canine model is further demonstrated. This study has potential clinical benefits in reducing both the incidence of DRT and the postoperative anticoagulant course for LAA closure.

Integrating coaxial electrospinning and 3D printing technologies for the development of biphasic porous scaffolds enabling spatiotemporal control in tumor ablation and osteochondral regeneration

The osteochondral defects (OCDs) resulting from the treatment of giant cell tumors of bone (GCTB) often present two challenges for clinicians: tumor residue leading to local recurrence and non-healing of OCDs. Therefore, this study focuses on developing a double-layer PGPC-PGPH scaffold using shell-core structure nanofibers to achieve "spatiotemporal control" for treating OCDs caused by GCTB. It addresses two key challenges: eliminating tumor residue after local excision and stimulating osteochondral regeneration in non-healing OCD cases. With a shell layer of protoporphyrin IX (PpIX)/gelatin (GT) and inner cores containing chondroitin sulfate (CS)/poly(lactic-co-glycolic acid) (PLGA) or hydroxyapatite (HA)/PLGA, coaxial electrospinning technology was used to create shell-core structured PpIX/GT-CS/PLGA and PpIX/GT-HA/PLGA nanofibers. These nanofibers were shattered into nano-scaled short fibers, and then combined with polyethylene oxide and hyaluronan to formulate distinct 3D printing inks. The upper layer consists of PpIX/GT-CS/PLGA ink, and the lower layer is made from PpIX/GT-HA/PLGA ink, allowing for the creation of a double-layer PGPC-PGPH scaffold using 3D printing technique. After GCTB lesion removal, the PGPC-PGPH scaffold is surgically implanted into the OCDs. The sonosensitizer PpIX in the shell layer undergoes sonodynamic therapy to selectively damage GCTB tissue, effectively eradicating residual tumors. Subsequently, the thermal effect of sonodynamic therapy accelerates the shell degradation and release of CS and HA within the core layer, promoting stem cell differentiation into cartilage and bone tissues at the OCD site in the correct anatomical position. This innovative scaffold provides temporal control for anti-tumor treatment followed by tissue repair and spatial control for precise osteochondral regeneration.

A Dual Reversible Cross-Linked Hydrogel with Enhanced Mechanical Property and Capable of Proangiogenic and Osteogenic Activities for Bone Defect Repair

The clinical treatment of bone defects presents ongoing challenges. One promising approach is bone tissue engineering (BTE), wherein hydrogels have garnered significant attention. However, the application of hydrogels in BTE is severely limited due to their poor mechanical properties, as well as their inferior proangiogenic and osteogenic activities. To address these limitations, our develop a dual cross-linked alendronate (ALN)-Ca2+ /Mg2+ -doped sulfated hyaluronic acid (SHA@CM) hydrogel, using a one-step mixing injection molding method known as "three-in-one" approach. This approach enabled the simultaneous formation of Schiff-Base crosslinking and electric attraction-based crosslinking within the hydrogel. The Schiff-Base crosslinking contributed to the majority of the hydrogel's mechanical strength, while the electric attraction-based crosslinking served as a release reservoir for Ca2+ /Mg2+ and ALN, promoting enhanced osteogenic activities and providing additional mechanical reinforcement to the hydrogel. These experimental data demonstrates several favorable properties of the SHA@CM hydrogel, including satisfactory injectability, rapid gelation, self-healing capacity, and excellent cytocompatibility. Moreover, the presence of sulfated groups and Mg2+ within the SHA@CM hydrogel exhibited pro-angiogenic effects, while the controlled release of nanoparticles formed by Ca2+ /Mg2+ and ALN further enhanced the osteogenesis of the hydrogel. Overall, these results indicate that the SHA@CM hydrogel holds significant potential for the clinical translation of BTE.

Curcumin-loaded porous scaffold: an anti-angiogenic approach to inhibit endochondral ossification

Bone marrow stem cells (BMSCs) are recognized for their robust proliferative capabilities and multidirectional differentiation potential. Ectopic endochondral ossification of BMSC-generated cartilage in subcutaneous environments is a concern associated with vascularization. Hence, devising a reliable strategy to inhibit vascularization is crucial. In this study, an anti-angiogenic drug, curcumin (Cur), was encapsulated into gelatin to create a porous Cur/Gelatin scaffold, with the aim of inhibiting vascular invasion and preventing endochondral ossification of BMSC-regenerated cartilage. In vitro wound healing tests demonstrated that a 30 μM Cur solution could inhibit the migration and growth of human umbilical vein endothelial cells without impeding BMSCs migration and growth. Compared to the gelatin scaffold, our findings verified that the Cur/Gelatin scaffold significantly inhibited vascular invasion after being subcutaneously implanted into rabbits for 12 weeks, as evidenced by gross observation and immunofluorescence CD31 staining. Moreover, both the porous gelatin and Cur/Gelatin scaffolds were populated with BMSCs and underwent in vitro chondrogenic cultivation to produce cartilage, followed by subcutaneous implantation in rabbits for 12 weeks. Histological examinations (including HE, Safranin-O/Fast Green, toluidine blue, and immunohistochemical COL II staining) revealed that the BMSC-generated cartilage in the gelatin group exhibited prominent endochondral ossification. In contrast, the BMSC-generated cartilage in the Cur/Gelatin group maintained cartilage features, such as cartilage matrix and lacunar structure. This study suggests that Cur-loaded scaffolds offer a reliable platform to inhibit endochondral ossification of BMSC-generated cartilage.

A bio-instructive parylene-based conformal coating suppresses thrombosis and intimal hyperplasia of implantable vascular devices

Implantable vascular devices are widely used in clinical treatments for various vascular diseases. However, current approved clinical implantable vascular devices generally have high failure rates primarily due to their surface lacking inherent functional endothelium. Here, inspired by the pathological mechanisms of vascular device failure and physiological functions of native endothelium, we developed a new generation of bioactive parylene (poly(p-xylylene))-based conformal coating to address these challenges of the vascular devices. This coating used a polyethylene glycol (PEG) linker to introduce an endothelial progenitor cell (EPC) specific binding ligand LXW7 (cGRGDdvc) onto the vascular devices for preventing platelet adhesion and selectively capturing endogenous EPCs. Also, we confirmed the long-term stability and function of this coating in human serum. Using two vascular disease-related large animal models, a porcine carotid artery interposition model and a porcine carotid artery-jugular vein arteriovenous graft model, we demonstrated that this coating enabled rapid generation of self-renewable "living" endothelium on the blood contacting surface of the expanded polytetrafluoroethylene (ePTFE) grafts after implantation. We expect this easy-to-apply conformal coating will present a promising avenue to engineer surface properties of "off-the-shelf" implantable vascular devices for long-lasting performance in the clinical settings.

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.

Restoring endothelial function: shedding light on cardiovascular stent development

Complete endothelialization is highly important for maintaining long-term patency and avoiding subsequent complications in implanting cardiovascular stents. It not only refers to endothelial cells (ECs) fully covering the inserted stents, but also includes the newly formed endothelium, which could exert physiological functions, such as anti-thrombosis and anti-stenosis. Clinical outcomes have indicated that endothelial dysfunction, especially the insufficiency of antithrombotic and barrier functions, is responsible for stent failure. Learning from vascular pathophysiology, endothelial dysfunction on stents is closely linked to the microenvironment of ECs. Evidence points to inflammatory responses, oxidative stress, altered hemodynamic shear stress, and impaired endothelial barrier affecting the normal growth of ECs, which are the four major causes of endothelial dysfunction. The related molecular mechanisms and efforts dedicated to improving the endothelial function are emphasized in this review. From the perspective of endothelial function, the design principles, advantages, and disadvantages behind current stents are introduced to enlighten the development of new-generation stents, aiming to offer new alternatives for restoring endothelial function.