Biocompatibility of Intensified Decellularized Equine Carotid Arteries in a Rat Subcutaneous Implantation Model and in a Human In Vitro Model

Three-dimensional printing and decellularized-extracellular-matrix based methods for advances in artificial blood vessel fabrication: A review

Blood vessels are the tubes through which blood flows and are divided into three types: millimeter-scale arteries, veins, and capillaries as well as micrometer-scale capillaries. Arteries and veins are the conduits that carry blood, while capillaries are where blood exchanges substances with tissues. Blood vessels are mainly composed of collagen fibers, elastic fibers, glycosaminoglycans and other macromolecular substances. There are about 19 feet of blood vessels per square inch of skin in the human body, which shows how important blood vessels are to the human body. Because cardiovascular disease and vascular trauma are common in the population, a great number of researches have been carried out in recent years by simulating the structures and functions of the person's own blood vessels to create different levels of tissue-engineered blood vessels that can replace damaged blood vessels in the human body. However, due to the lack of effective oxygen and nutrient delivery mechanisms, these tissue-engineered vessels have not been used clinically. Therefore, in order to achieve better vascularization of engineered vascular tissue, researchers have widely explored the design methods of vascular systems of various sizes. In the near future, these carefully designed and constructed tissue engineered blood vessels are expected to have practical clinical applications. Exploring how to form multi-scale vascular networks and improve their compatibility with the host vascular system will be very beneficial in achieving this goal. Among them, 3D printing has the advantages of high precision and design flexibility, and the decellularized matrix retains active ingredients such as collagen, elastin, and glycosaminoglycan, while removing the immunogenic substance DNA. In this review, technologies and advances in 3D printing and decellularization-based artificial blood vessel manufacturing methods are systematically discussed. Recent examples of vascular systems designed are introduced in details, the main problems and challenges in the clinical application of vascular tissue restriction are discussed and pointed out, and the future development trends in the field of tissue engineered blood vessels are also prospected.

The Outcome of Sac Filling With Fibrin Sealant and Gentamicin After Endovascular Aortic Repair of Brucella-Related Aorto-Iliac Artery Aneurysms: A Retrospective Single-Center Study

PURPOSE

This study aimed to analyze the experience of our center and assess the efficacy of sac filling with fibrin sealant (FS) and gentamicin after endovascular aortic repair (EVAR) in patients with Brucella-related aorto-iliac artery aneurysms.

MATERIALS AND METHODS

All patients who received sac filling with FS and gentamicin after EVAR for Brucella-related aorto-iliac artery aneurysms between March 2019 and September 2022 were reviewed. Before and after sac filling with FS and gentamicin, aneurysm sac thrombosis and endoleak were evaluated using a preloaded catheter to monitor immediate repair outcome. Short- to mid-term outcomes were assessed by the incidence of vascular graft infection (VGI), all-cause mortality, maximum aneurysm diameter, aneurysm sac thrombosis, and other adverse events.

RESULTS

There were 14 patients with Brucella-related aorto-iliac artery aneurysms who underwent sac filling with FS and gentamicin after EVAR. Perioperative death due to myocardial infarction in 1 patient resulted in a postoperative all-cause mortality rate of 7.1% (1/14). All patients received anti-Brucella drugs for a median of 6.0 (range: 3-12) months postoperatively. During a median follow-up period of 15.0 (range 0.5-36) months, the absolute and sagittal maximum diameters of the aorto-iliac aneurysm sac were significantly smaller than preoperation (from 46.3 ± 17.0 to 27.2 ± 16.3 mm, P<.001, and from 39.2 ± 13.1 to 24.0 ± 13.8 mm, P<.001). Two of these patients had a postoperative disappearance of the pseudoaneurysm. One patient was reintervened for bilateral femoral artery bypass surgery. Except for sac filling with gentamicin, all patients received anti-brucella medication for a median of 6.0 (range: 3-12) months. There were no allergic reactions, nephrotoxicity, endoleak, recurrence, VGI, aorta-related or infection-related deaths during the perioperative period and follow-up.

CONCLUSIONS

Sac filling with FS and gentamicin adjunctive to EVAR, with targeted drug delivery to the sites of Brucella-related aorto-iliac artery aneurysm infection lesions, may be an effective solution to control pseudoaneurysm infection and rupture.

CLINICAL IMPACT

Previous Brucella-associated aorto-iliac artery aneurysms have been limited to case reports. This study significantly increased the number of Brucella-associated aorto-iliac aneurysms by 19.7% (14/71) and extended the follow-up to 3 years. In this retrospective study of 14 patients with Brucella-associated aorto-iliac aneurysms treated endovascularly with fibrin sealant and gentamicin for sac filling and targeted administration to infection-related aneurysms, there were no aneurysm-related deaths or infection-related complications and may be an effective solution for controlling aneurysm infection and rupture. And, this approach is an attractive treatment for moving away from long-term dependence on antibiotics but still needs further evaluation.

Biomimetic Scaffolds for Tendon Tissue Regeneration

Tendon tissue connects muscle to bone and plays crucial roles in stress transfer. Tendon injury remains a significant clinical challenge due to its complicated biological structure and poor self-healing capacity. The treatments for tendon injury have advanced significantly with the development of technology, including the use of sophisticated biomaterials, bioactive growth factors, and numerous stem cells. Among these, biomaterials that the mimic extracellular matrix (ECM) of tendon tissue would provide a resembling microenvironment to improve efficacy in tendon repair and regeneration. In this review, we will begin with a description of the constituents and structural features of tendon tissue, followed by a focus on the available biomimetic scaffolds of natural or synthetic origin for tendon tissue engineering. Finally, we will discuss novel strategies and present challenges in tendon regeneration and repair.

Decellularized scaffold and its elicited immune response towards the host: the underlying mechanism and means of immunomodulatory modification

The immune response of the host towards a decellularized scaffold is complex. Not only can a number of immune cells influence this process, but also the characteristics, preparation and modification of the decellularized scaffold can significantly impact this reaction. Such factors can, together or alone, trigger immune cells to polarize towards either a pro-healing or pro-inflammatory direction. In this article, we have comprehensively reviewed factors which may influence the immune response of the host towards a decellularized scaffold, including the source of the biomaterial, biophysical properties or modifications of the scaffolds with bioactive peptides, drugs and cytokines. Furthermore, the underlying mechanism has also been recapitulated.

Tissue Engineering for Mimics and Modulations of Immune Functions

In the field of regenerative medicine, advances in tissue engineering have surpassed the reconstruction of individual tissues or organs and begun to work towards engineering systemic factors such as immune objects and functions. The immune system plays a crucial role in protecting and regulating systemic functions in the human body. Engineered immune tissues and organs have shown potential in recovering dysfunctions and aplasia of the immune system and the evasion from immune-mediated inflammatory responses and rejection elicited by engineered implants from allogeneic or xenogeneic sources are also being pursued to facilitate clinical transplantation of tissue engineered grafts. Here, current progress in tissue engineering to mimic or modulate immune functions is reviewed and elaborated from two perspectives: 1) engineering of immune tissues and organs per se and 2) immune evasion of host immunoinflammatory rejection by tissue-engineered implants.

Bioreactivity of decellularized animal, plant, and fungal scaffolds: perspectives for medical applications

Numerous biomedical applications imply supportive materials to improve protective, antibacterial, and regenerative abilities upon surgical interventions, oncotherapy, regenerative medicine, and others. With the increasing variability of the possible sources, the materials of natural origin are among the safest and most accessible biomedical tools. Animal, plant, and fungal tissues can further undergo decellularization to improve their biocompatibility. Decellularized scaffolds lack the most reactive cellular material, nuclear and cytoplasmic components, that predominantly trigger immune responses. At the same time, the outstanding initial three-dimensional microarchitecture, biomechanical properties, and general composition of the scaffolds are preserved. These unique features make the scaffolds perfect ready-to-use platforms for various biomedical applications, implying cell growth and functionalization. Decellularized materials can be repopulated with various cells upon request, including epithelial, endothelial, muscle and neuronal cells, and applied for structural and functional biorepair within diverse biological sites, including the skin and musculoskeletal, cardiovascular, and central nervous systems. However, the molecular and cellular mechanisms behind scaffold and host tissue interactions remain not fully understood, which significantly restricts their integration into clinical practice. In this review, we address the essential aspects of decellularization, scaffold preparation techniques, and its biochemical composition and properties, which determine the biocompatibility and immunogenicity of the materials. With the integrated evaluation of the scaffold profile in living systems, decellularized animal, plant, and fungal scaffolds have the potential to become essential instruments for safe and controllable biomedical applications.

Limitations of recellularized biological scaffolds for human transplantation

A shortage of donor organs for transplantation and the dependence of the recipients on immunosuppressive therapy have motivated researchers to consider alternative regenerative approaches. The answer may reside in acellular scaffolds generated from cadaveric human and animal tissues. Acellular scaffolds are expected to preserve the architectural and mechanical properties of the original organ, permitting cell attachment, growth, and differentiation. Although theoretically, the use of acellular scaffolds for transplantation should pose no threat to the recipient's immune system, experimental data have revealed significant immune responses to allogeneic and xenogeneic transplanted scaffolds. Herein, we review the various factors of the scaffold that could trigger an inflammatory and/or immune response, thereby compromising its use for human transplant therapy. In addition, we provide an overview of the major cell types that have been considered for recellularization of the scaffold and their potential contribution to triggering an immune response.

Decellularized equine carotid artery layers as matrix for regenerated neurites of spiral ganglion neurons

Today’s best solution in compensating for sensorineural hearing loss is the cochlear implant, which electrically stimulates the spiral ganglion neurons in the inner ear. An optimum hearing impression is not ensured due to, among other reasons, a remaining anatomical gap between the spiral ganglion neurons and the implant electrodes. The gap could be bridged via pharmacologically triggered neurite growth toward the electrodes if biomaterials for neurite guidance could be provided. For this, we investigated the suitability of decellularized tissue. We compared three different layers (tunica adventitia, tunica media, and tunica intima) of decellularized equine carotid arteries in a preliminary approach. Rat spiral ganglia explants were cultured on decellularized equine carotid artery layers and neurite sprouting was assessed quantitatively. Generally, neurite outgrowth was possible and it was most prominent on the intima (in average 83 neurites per spiral ganglia explants, followed by the adventitia (62 neurites) and the lowest growth on the media (20 neurites). Thus, decellularized equine carotid arteries showed promising effects on neurite regeneration and can be developed further as efficient biomaterials for neural implants in hearing research.

Functional Vascular Tissue Engineering Inspired by Matricellular Proteins

Modern regenerative medicine, and tissue engineering specifically, has benefited from a greater appreciation of the native extracellular matrix (ECM). Fibronectin, collagen, and elastin have entered the tissue engineer's toolkit; however, as fully decellularized biomaterials have come to the forefront in vascular engineering it has become apparent that the ECM is comprised of more than just fibronectin, collagen, and elastin, and that cell-instructive molecules known as matricellular proteins are critical for desired outcomes. In brief, matricellular proteins are ECM constituents that contrast with the canonical structural proteins of the ECM in that their primary role is to interact with the cell. Of late, matricellular genes have been linked to diseases including connective tissue disorders, cardiovascular disease, and cancer. Despite the range of biological activities, this class of biomolecules has not been actively used in the field of regenerative medicine. The intent of this review is to bring matricellular proteins into wider use in the context of vascular tissue engineering. Matricellular proteins orchestrate the formation of new collagen and elastin fibers that have proper mechanical properties-these will be essential components for a fully biological small diameter tissue engineered vascular graft (TEVG). Matricellular proteins also regulate the initiation of thrombosis via fibrin deposition and platelet activation, and the clearance of thrombus when it is no longer needed-proper regulation of thrombosis will be critical for maintaining patency of a TEVG after implantation. Matricellular proteins regulate the adhesion, migration, and proliferation of endothelial cells-all are biological functions that will be critical for formation of a thrombus-resistant endothelium within a TEVG. Lastly, matricellular proteins regulate the adhesion, migration, proliferation, and activation of smooth muscle cells-proper control of these biological activities will be critical for a TEVG that recellularizes and resists neointimal formation/stenosis. We review all of these functions for matricellular proteins here, in addition to reviewing the few studies that have been performed at the intersection of matricellular protein biology and vascular tissue engineering.

Micro and ultrastructural changes monitoring during decellularization for the generation of a biocompatible liver

Decellularization of a whole organ is an attractive process that has been used to create 3D scaffolds structurally and micro-architecturally similar to the native one. Currently used decellularization protocols exhibit disrupted extracellular matrix (ECM) structure and denatured ECM proteins. Therefore, maintaining a balance between ECM preservation and cellular removal is a major challenge. The aim of this study was to optimize a multistep Triton X-100 based protocol (either using Triton X-100/ammonium hydroxide mixture alone or after its modification with DNase, sodium dodecyl sulfate or trypsin) that could achieve maximum decellularization with minimal liver ECM destruction suitable for subsequent organ implantation without immune rejection. Based on our findings, Triton X-100 multistep protocol was insufficient for whole liver decellularization and needed to be modified with other detergents. Among all Triton X-100 modified protocols, a Triton X-100/DNase-based one was considered the most suitable. It maintains a gradual but sufficient removal of cells to generate decellularized biocompatible liver scaffolds without any significant alteration to ECM micro- and ultra-structure.