Optimizing the biofabrication process of omentum-based scaffolds for engineering autologous tissues

Decellularization of various tissues and organs through chemical methods

Due to the increase in demand for donor organs and tissues during the past 20 years, new approaches have been created. These methods include, for example, tissue engineering in vitro and the production of regenerative biomaterials for transplantation. Applying the natural extracellular matrix (ECM) as a bioactive biomaterial for clinical applications is a unique approach known as decellularization technology. Decellularization is the process of eliminating cells from an extracellular matrix while preserving its natural components including its structural and functional proteins and glycosaminoglycan. This can be achieved by physical, chemical, or biological processes. A naturally formed three-dimensional structure with a biocompatible and regenerative structure is the result of the decellularization process. Decreasing the biological factors and antigens at the transplant site reduces the risk of adverse effects including inflammatory responses and immunological rejection. Regenerative medicine and tissue engineering applications can benefit from the use of decellularization, a promising approach that provides a biomaterial that preserves its extracellular matrix.

Modified ECM-Based Bioink for 3D Printing of Multi-Scale Vascular Networks

The survival and function of tissues depend on appropriate vascularization. Blood vessels of the tissues supply oxygen, and nutrients and remove waste and byproducts. Incorporating blood vessels into engineered tissues is essential for overcoming diffusion limitations, improving tissue function, and thus facilitating the fabrication of thick tissues. Here, we present a modified ECM bioink, with enhanced mechanical properties and endothelial cell-specific adhesion motifs, to serve as a building material for 3D printing of a multiscale blood vessel network. The bioink is composed of natural ECM and alginate conjugated with a laminin adhesion molecule motif (YIGSR). The hybrid hydrogel was characterized for its mechanical properties, biochemical content, and ability to interact with endothelial cells. The pristine and modified hydrogels were mixed with induced pluripotent stem cells derived endothelial cells (iPSCs-ECs) and used to print large blood vessels with capillary beds in between.

Current Strategies for Engineered Vascular Grafts and Vascularized Tissue Engineering

Blood vessels not only transport oxygen and nutrients to each organ, but also play an important role in the regulation of tissue regeneration. Impaired or occluded vessels can result in ischemia, tissue necrosis, or even life-threatening events. Bioengineered vascular grafts have become a promising alternative treatment for damaged or occlusive vessels. Large-scale tubular grafts, which can match arteries, arterioles, and venules, as well as meso- and microscale vasculature to alleviate ischemia or prevascularized engineered tissues, have been developed. In this review, materials and techniques for engineering tubular scaffolds and vasculature at all levels are discussed. Examples of vascularized tissue engineering in bone, peripheral nerves, and the heart are also provided. Finally, the current challenges are discussed and the perspectives on future developments in biofunctional engineered vessels are delineated.

Scaffolds Based on Silk Fibroin with Decellularized Rat Liver Microparticles: Investigation of the Structure, Biological Properties and Regenerative Potential for Skin Wound Healing

The development of advanced biomaterials and constructs for accelerated recovery of damaged tissues is a key direction in regenerative medicine. Biocompatible scaffolds based on natural biopolymers are widely used for these tasks. Organ decellularization enables obtaining a cell-free extracellular matrix (ECM) with preserved composition and biological activity. The objectives of the present work were combining these two approaches for the development of a composite scaffold based on silk fibroin and ECM microparticles and assessing its structure, biological properties, and regenerative potential. ECM microparticles were obtained by grinding the decellularized matrix of Wistar rat liver in liquid nitrogen. Scaffolds in the form of films were prepared by the casting method. The sinuous and rough topography of the scaffold surface was assessed by the scanning probe nanotomography (SPNT) technique. The inclusion of ECM microparticles in the composition did not affect the elasticity and tensile strength of the scaffolds. The obtained scaffold was non-toxic to cells, maintained high levels of adhesion and proliferation of mouse 3T3 fibroblast and Hep-G2 cells, and showed high regenerative potential, which was studied in the experimental model of full-thickness rat skin wound healing. The wound healing was accelerated by 1.74 times in comparison with the control.

A human pancreatic ECM hydrogel optimized for 3-D modeling of the islet microenvironment

Extracellular matrix (ECM) plays a multitude of roles, including supporting cells through structural and biochemical interactions. ECM is damaged in the process of isolating human islets for clinical transplantation and basic research. A platform in which islets can be cultured in contact with natural pancreatic ECM is desirable to better understand and support islet health, and to recapitulate the native islet environment. Our study demonstrates the derivation of a practical and durable hydrogel from decellularized human pancreas that supports human islet survival and function. Islets embedded in this hydrogel show increased glucose- and KCl-stimulated insulin secretion, and improved mitochondrial function compared to islets cultured without pancreatic matrix. In extended culture, hydrogel co-culture significantly reduced levels of apoptosis compared to suspension culture and preserved controlled glucose-responsive function. Isolated islets displayed altered endocrine and non-endocrine cell arrangement compared to in situ islets; hydrogel preserved an islet architecture more similar to that observed in situ. RNA sequencing confirmed that gene expression differences between islets cultured in suspension and hydrogel largely fell within gene ontology terms related to extracellular signaling and adhesion. Natural pancreatic ECM improves the survival and physiology of isolated human islets.

Characterization of decellularized chicken skin as a tissue engineering scaffold

Decellularization has been applied on many tissues and organs to obtain biomaterials for the applications in tissue engineering. In this study, decellularization and characterization of chicken skin was performed to provide comprehensive information and in-depth details on this material as a potential tissue scaffold. Application of Triton X-100 and sodium dodecyl sulfate (SDS) on tissues in different time intervals as two decellularization protocols were compared according to various aspects such as removal of cellular components, DNA quantification, protection of extracellular matrix (ECM), mechanical properties and cytocompatibility to find the optimum technique during preparation of decellularized scaffold. The results showed that treatment with SDS revealed better results when compared with Triton X-100 regarding to preserve tissue structure and morphology although there was no difference on efficiency of decellularization. In general, the tissues decellularized with SDS demonstrated higher level of cytocompatibility and better mechanical properties in comparison with samples treated with Triton X-100. In conclusion, this study revealed that decellularized chicken skin is a cheap, abundant, and biocompatible material that supports cell attachment, growth, and proliferation. Therefore, it could be used as a proper candidate to prepare scaffolds for the further studies on tissue engineering especially for skin tissue engineering. Decellularized chicken skin was prepared and characterized as an abundant, cheap, and biocompatible material for using it as a tissue scaffold. Tissues were treated with Triton X-100 and sodium dodecyl sulfate (SDS) in various time points and samples were compared regarding to cell removal, cell viability, mechanical properties, and preservation of extracellular matrix. 24 hours of decellularization with SDS could be the optimum method to prepare decellularized chicken skin as a scaffold for skin tissue engineering. This article is protected by copyright. All rights reserved.

Regenerating the Injured Spinal Cord at the Chronic Phase by Engineered iPSCs-Derived 3D Neuronal Networks

Cell therapy using induced pluripotent stem cell-derived neurons is considered a promising approach to regenerate the injured spinal cord (SC). However, the scar formed at the chronic phase is not a permissive microenvironment for cell or biomaterial engraftment or for tissue assembly. Engineering of a functional human neuronal network is now reported by mimicking the embryonic development of the SC in a 3D dynamic biomaterial-based microenvironment. Throughout the in vitro cultivation stage, the system's components have a synergistic effect, providing appropriate cues for SC neurogenesis. While the initial biomaterial supported efficient cell differentiation in 3D, the cells remodeled it to provide an inductive microenvironment for the assembly of functional SC implants. The engineered tissues are characterized for morphology and function, and their therapeutic potential is investigated, revealing improved structural and functional outcomes after acute and chronic SC injuries. Such technology is envisioned to be translated to the clinic to rewire human injured SC.

Preparation and characterization of decellularized rooster comb as a scaffold for tissue engineering applications

Decellularization is a method that has been widely used in tissue engineering especially in the last 20 years. In this study decellularized rooster comb was prepared and characterized for using it as a tissue scaffold. Treatment of tissues with sodium dodecyl sulfate (SDS) and Triton X-100 as two decellularization procedures in different time points were compared according to different parameters such as cytocompatibility, cell removal, preservation of extracellular matrix (ECM), and mechanical properties to find the optimum technique. Even though there was no difference regarding to efficiency on cell removal, SDS demonstrated better results on protection of tissue morphology in comparison with Triton X-100. Therefore, in general the samples treated with SDS showed higher levels of mechanical properties and cytocompatibility in comparison with Triton X-100 applied tissues. In the cuisines of many countries, rooster comb is discarded as a waste material however, in this study it was demonstrated that decellularized rooster comb could be utilized as a cheap, easily obtainable, and biocompatible scaffold. In conclusion, it was revealed that decellularized rooster comb is a promising biomaterial for using as scaffold and it is expected to be utilized for the further studies in particular on skin tissue engineering.

Omentum support for cardiac regeneration in ischaemic cardiomyopathy models: a systematic scoping review

OBJECTIVES

Preclinical in vivo studies using omental tissue as a biomaterial for myocardial regeneration are promising and have not previously been collated. We aimed to evaluate the effects of the omentum as a support for bioengineered tissue therapy for cardiac regeneration in vivo.

METHODS

A systematic scoping review was performed. Only English-language studies that used bioengineered cardio-regenerative tissue, omentum and ischaemic cardiomyopathy in vivo models were included.

RESULTS

We initially screened 1926 studies of which 17 were included in the final qualitative analysis. Among these, 11 were methodologically comparable and 6 were non-comparable. The use of the omentum improved the engraftment of bioengineered tissue by improving cell retention and reducing infarct size. Vascularization was also improved by the induction of angiogenesis in the transplanted tissue. Omentum-supported bioengineered grafts were associated with enhanced host reverse remodelling and improved haemodynamic measurements.

CONCLUSIONS

The omentum is a promising support for myocardial regenerative bioengineering in vivo. Future studies would benefit from more homogenous methodologies and reporting of outcomes to allow for direct comparison.

From arteries to capillaries: approaches to engineering human vasculature

From micro-scaled capillaries to millimeter-sized arteries and veins, human vasculature spans multiple scales and cell types. The convergence of bioengineering, materials science, and stem cell biology has enabled tissue engineers to recreate the structure and function of different hierarchical levels of the vascular tree. Engineering large-scale vessels has been pursued over the past thirty years to replace or bypass damaged arteries, arterioles, and venules, and their routine application in the clinic may become a reality in the near future. Strategies to engineer meso- and microvasculature have been extensively explored to generate models to study vascular biology, drug transport, and disease progression, as well as for vascularizing engineered tissues for regenerative medicine. However, bioengineering of large-scale tissues and whole organs for transplantation, have failed to result in clinical translation due to the lack of proper integrated vasculature for effective oxygen and nutrient delivery. The development of strategies to generate multi-scale vascular networks and their direct anastomosis to host vasculature would greatly benefit this formidable goal. In this review, we discuss design considerations and technologies for engineering millimeter-, meso-, and micro-scale vessels. We further provide examples of recent state-of-the-art strategies to engineer multi-scale vasculature. Finally, we identify key challenges limiting the translation of vascularized tissues and offer our perspective on future directions for exploration.

Decellularized Scaffolds for Skin Repair and Regeneration

The skin is the largest organ in the body, fulfilling a variety of functions and acting as a barrier for internal organs against external insults. As for extensive or irreversible damage, skin autografts are often considered the gold standard, however inherent limitations highlight the need for alternative strategies. Engineering of human-compatible tissues is an interdisciplinary and active field of research, leading to the production of scaffolds and skin substitutes to guide repair and regeneration. However, faithful reproduction of extracellular matrix (ECM) architecture and bioactive content capable of cell-instructive and cell-responsive properties remains challenging. ECM is a heterogeneous, connective network composed of collagens, glycoproteins, proteoglycans, and small molecules. It is highly coordinated to provide the physical scaffolding, mechanical stability, and biochemical cues necessary for tissue morphogenesis and homeostasis. Decellularization processes have made it possible to isolate the ECM in its native and three-dimensional form from a cell-populated tissue for use in skin regeneration. In this review, we present recent knowledge about these decellularized biomaterials with the potential to be used as dermal or skin substitutes in clinical applications. We detail tissue sources and clinical indications with success rates and report the most effective decellularization methods compatible with clinical use.

Copolymer/Clay Nanocomposites for Biomedical Applications

Nanoclays still hold a great strength in biomedical nanotechnology applications due to their exceptional properties despite the development of several new nanostructured materials. This article reviews the recent advances in copolymer/clay nanocomposites with a focus on health care applications. In general, the structure of clay comprises aluminosilicate layers separated by a few nanometers. Recently, nanoclay‐incorporated copolymers have attracted the interest of both researchers and industry due to their phenomenal properties such as barrier function, stiffness, thermal/flame resistance, superhydrophobicity, biocompatibility, stimuli responsiveness, sustained drug release, resistance to hydrolysis, outstanding dynamic mechanical properties including resilience and low temperature flexibility, excellent hydrolytic stability, and antimicrobial properties. Surface modification of nanoclays provides additional properties due to improved adhesion between the polymer matrix and the nanoclay, high surface free energy, a high degree of intercalation, or exfoliated morphology. The architecture of the copolymer/clay nanocomposites has great impact on biomedical applications, too, by providing various cues especially in drug delivery systems and regenerative medicine.

Shape memory histocompatible and biodegradable sponges for subcutaneous defect filling and repair: greatly reducing surgical incision

Reducing surgical incision for large area subcutaneous defect filling and repair is a great challenge in the biomedical field, especially for plastic surgery. In this study, a novel hydroxyethyl cellulose/soy protein isolate (HEC/SPI) composite sponge (EHSS) with a fluid responsive shape memory property was constructed, whose thickness could be controlled by hot-pressing conditions to reduce the required surgical incision greatly. Effects of the main factors such as pressure, temperature and hot-pressing cycles on the recovery degree of EHSS were investigated systematically. The structure and physical properties of the sponges were characterized by FTIR spectroscopy, XRD, SEM etc. The results showed that EHSS could be pressed into thin disks with much smaller thickness, and the thickness retention ratio and recovery ratio were affected by hot-pressing conditions such as pressure and temperature. Especially, EHSS could be hot-pressed into a dense thin disk (EHSS-PT-130) at 130 °C with the pressure of 30 MPa, which could quickly recover its original shape by soaking in hydrophilic fluids. EHSS-PT-130 also exhibited good hydrophilicity, cytocompatibility, histocompatibility and in vivo biodegradability. Compared with the original EHSS, in vivo shape memory EHSS-PT-130 required much smaller surgical incision to reach the same repair effect and no need of extra sterilization, showing potential application for subcutaneous defect filling and repair.

Tissue-Engineered Grafts from Human Decellularized Extracellular Matrices: A Systematic Review and Future Perspectives

Tissue engineering and regenerative medicine involve many different artificial and biologic materials, frequently integrated in composite scaffolds, which can be repopulated with various cell types. One of the most promising scaffolds is decellularized allogeneic extracellular matrix (ECM) then recellularized by autologous or stem cells, in order to develop fully personalized clinical approaches. Decellularization protocols have to efficiently remove immunogenic cellular materials, maintaining the nonimmunogenic ECM, which is endowed with specific inductive/differentiating actions due to its architecture and bioactive factors. In the present paper, we review the available literature about the development of grafts from decellularized human tissues/organs. Human tissues may be obtained not only from surgery but also from cadavers, suggesting possible development of Human Tissue BioBanks from body donation programs. Many human tissues/organs have been decellularized for tissue engineering purposes, such as cartilage, bone, skeletal muscle, tendons, adipose tissue, heart, vessels, lung, dental pulp, intestine, liver, pancreas, kidney, gonads, uterus, childbirth products, cornea, and peripheral nerves. In vitro recellularizations have been reported with various cell types and procedures (seeding, injection, and perfusion). Conversely, studies about in vivo behaviour are poorly represented. Actually, the future challenge will be the development of human grafts to be implanted fully restored in all their structural/functional aspects.

ECM-based macroporous sponges release essential factors to support the growth of hematopoietic cells

The success of hematopoietic stem cells (HSCs) transplantation is limited due to the low number of HSCs received from donors. In vivo, HSCs reside within a specialized niche inside the 3D porous spongy bone. The natural environment in the niche is composed of structural proteins, glycosaminoglycans (GAGs) and soluble factors that control cells fate. However, the designed scaffolds for in vitro culture do not fairly recapitulate this microenvironment and cannot efficiently control HSCs fate. Here we report on the development of new omental ECM-based 3D macroporous sponges for hematopoietic cell culture. The scaffolds' structure, porosity and stability were characterized and optimized. Analysis of the biochemical content revealed that they were composed of collagens and GAGs, including sulfated GAGs. This morphology and composition enabled growth factors interaction with the sulfated GAGs, as indicated by the high loading capacity and release profile of three different hematopoietic niche factors. Finally, the ability of the ECM-based scaffolds to efficiently support the growth of hematopoietic cells by releasing stem cell factor (SCF) was demonstrated.