Automated freeze-thaw cycles for decellularization of tendon tissue - a pilot study

Liver tissue engineering using decellularized scaffolds: Current progress, challenges, and opportunities

Liver transplantation represents the only definitive treatment for patients with end-stage liver disease. However, the shortage of liver donors provokes a dramatic gap between available grafts and patients on the waiting list. Whole liver bioengineering, an emerging field of tissue engineering, holds great potential to overcome this gap. This approach involves two main steps; the first is liver decellularization and the second is recellularization. Liver decellularization aims to remove cellular and nuclear materials from the organ, leaving behind extracellular matrices containing different structural proteins and growth factors while retaining both the vascular and biliary networks. Recellularization involves repopulating the decellularized liver with appropriate cells, theoretically from the recipient patient, to reconstruct the parenchyma, vascular tree, and biliary network. The aim of this review is to identify the major advances in decellularization and recellularization strategies and investigate obstacles for the clinical application of bioengineered liver, including immunogenicity of the designed liver extracellular matrices, the need for standardization of scaffold fabrication techniques, selection of suitable cell sources for parenchymal repopulation, vascular, and biliary tree reconstruction. In vivo transplantation models are also summarized for evaluating the functionality of bioengineered livers. Finally, the regulatory measures and future directions for confirming the safety and efficacy of bioengineered liver are also discussed. Addressing these challenges in whole liver bioengineering may offer new solutions to meet the demand for liver transplantation and improve patient outcomes.

Swim bladder-derived biomaterials: structures, compositions, properties, modifications, and biomedical applications

Animal-derived biomaterials have been extensively employed in clinical practice owing to their compositional and structural similarities with those of human tissues and organs, exhibiting good mechanical properties and biocompatibility, and extensive sources. However, there is an associated risk of infection with pathogenic microorganisms after the implantation of tissues from pigs, cattle, and other mammals in humans. Therefore, researchers have begun to explore the development of non-mammalian regenerative biomaterials. Among these is the swim bladder, a fish-derived biomaterial that is rapidly used in various fields of biomedicine because of its high collagen, elastin, and polysaccharide content. However, relevant reviews on the biomedical applications of swim bladders as effective biomaterials are lacking. Therefore, based on our previous research and in-depth understanding of this field, this review describes the structures and compositions, properties, and modifications of the swim bladder, with their direct (including soft tissue repair, dural repair, cardiovascular repair, and edible and pharmaceutical fish maw) and indirect applications (including extracted collagen peptides with smaller molecular weights, and collagen or gelatin with higher molecular weights used for hydrogels, and biological adhesives or glues) in the field of biomedicine in recent years. This review provides insights into the use of swim bladders as source of biomaterial; hence, it can aid biomedicine scholars by providing directions for advancements in this field.

Extracellular matrix-derived materials for tissue engineering and regenerative medicine: A journey from isolation to characterization and application

Biomaterial choice is an essential step during the development tissue engineering and regenerative medicine (TERM) applications. The selected biomaterial must present properties allowing the physiological-like recapitulation of several processes that lead to the reestablishment of homeostatic tissue or organ function. Biomaterials derived from the extracellular matrix (ECM) present many such properties and their use in the field has been steadily increasing. Considering this growing importance, it becomes imperative to provide a comprehensive overview of ECM biomaterials, encompassing their sourcing, processing, and integration into TERM applications. This review compiles the main strategies used to isolate and process ECM-derived biomaterials as well as different techniques used for its characterization, namely biochemical and chemical, physical, morphological, and biological. Lastly, some of their applications in the TERM field are explored and discussed.

The trend of allogeneic tendon decellularization: literature review

Tendon injuries repair is a significant burden for orthopaedic surgeons. Finding a proper graft material to repair tendon is one of the main challenges in orthopaedics, for which the requirement of substitute for tendon repair would be different for each clinical application. Among biological scaffolds, the use of decellularized tendon increasingly represents an interesting approach to treat tendon injuries and several articles have investigated the approaches of tendon decellularization. To understand the outcomes of the the approaches of tendon decellularization on effect of tendon transplantation, a literature review was performed. This review was conducted by searching in Pubmed and Embase and 64 studies were included in this study. The findings revealed that the common approaches to decellularize tendon include chemical, physical, and enzymatic decellularization methods or their combination. With the development of tissue engineering, researchers also put forward new theories such as automatic acellular machine, 3D printing technology to manufacture acellular scaffold.

Decellularization and Their Significance for Tissue Regeneration in the Era of 3D Bioprinting

Three-dimensional bioprinting is an emerging technology that has high potential application in tissue engineering and regenerative medicine. Increasing advancement and improvement in the decellularization process have led to an increase in the demand for using a decellularized extracellular matrix (dECM) to fabricate tissue engineered products. Decellularization is the process of retaining the extracellular matrix (ECM) while the cellular components are completely removed to harvest the ECM for the regeneration of various tissues and across different sources. Post decellularization of tissues and organs, they act as natural biomaterials to provide the biochemical and structural support to establish cell communication. Selection of an effective method for decellularization is crucial, and various factors like tissue density, geometric organization, and ECM composition affect the regenerative potential which has an impact on the end product. The dECM is a versatile material which is added as an important ingredient to formulate the bioink component for constructing tissue and organs for various significant studies. Bioink consisting of dECM from various sources is used to generate tissue-specific bioink that is unique and to mimic different biometric microenvironments. At present, there are many different techniques applied for decellularization, and the process is not standardized and regulated due to broad application. This review aims to provide an overview of different decellularization procedures, and we also emphasize the different dECM-derived bioinks present in the current global market and the major clinical outcomes. We have also highlighted an overview of benefits and limitations of different decellularization methods and various characteristic validations of decellularization and dECM-derived bioinks.

An increase in Wharton's jelly membrane osteocompatibility by a genipin-cross-link

Wharton's Jelly (WJ) has attracted significant interest in the field of tissue healing thanks to its biological properties, including antibacterial activity and immunomodulation. However, due to the fast degradation and poor mechanical behavior in biological environment, its application in bone regeneration is compromised. Here, we proposed to use genipin as an efficient cross-linking agent to significantly improve the elasticity and the enzymatical stability of the WJ matrix. The degree of cross-linking, linear elastic moduli, and collagenase resistance varied over a wide range depending on genipin concentration. Furthermore, our results highlighted that an increase in genipin concentration led to a decreased surface wettability, therefore impairing cell attachment and proliferation. The genipin cross-linking prevented rapid in vitro and in vivo degradation, but led to an adverse host reaction and calcification. When implanted in the parietal bone defect, a limited parietal bone regeneration to the dura was observed. We conclude that genipin-cross-linked WJ is a versatile medical device however, a careful selection is required with regards to the genipin concentration.

Tailoring the multiscale mechanics of tunable decellularized extracellular matrix (dECM) for wound healing through immunomodulation

With the discovery of the pivotal role of macrophages in tissue regeneration through shaping the tissue immune microenvironment, various immunomodulatory strategies have been proposed to modify traditional biomaterials. Decellularized extracellular matrix (dECM) has been extensively used in the clinical treatment of tissue injury due to its favorable biocompatibility and similarity to the native tissue environment. However, most reported decellularization protocols may cause damage to the native structure of dECM, which undermines its inherent advantages and potential clinical applications. Here, we introduce a mechanically tunable dECM prepared by optimizing the freeze-thaw cycles. We demonstrated that the alteration in micromechanical properties of dECM resulting from the cyclic freeze-thaw process contributes to distinct macrophage-mediated host immune responses to the materials, which are recently recognized to play a pivotal role in determining the outcome of tissue regeneration. Our sequencing data further revealed that the immunomodulatory effect of dECM was induced via the mechnotrasduction pathways in macrophages. Next, we tested the dECM in a rat skin injury model and found an enhanced micromechanical property of dECM achieved with three freeze-thaw cycles significantly promoted the M2 polarization of macrophages, leading to superior wound healing. These findings suggest that the immunomodulatory property of dECM can be efficiently manipulated by tailoring its inherent micromechanical properties during the decellularization process. Therefore, our mechanics-immunomodulation-based strategy provides new insights into the development of advanced biomaterials for wound healing.

Decellularization of Dense Regular Connective Tissue-Cellular and Molecular Modification with Applications in Regenerative Medicine

Healing of dense regular connective tissue, due to a high fiber-to-cell ratio and low metabolic activity and regeneration potential, frequently requires surgical implantation or reconstruction with high risk of reinjury. An alternative to synthetic implants is using bioscaffolds obtained through decellularization, a process where the aim is to extract cells from the tissue while preserving the tissue-specific native molecular structure of the ECM. Proteins, lipids, nucleic acids and other various extracellular molecules are largely involved in differentiation, proliferation, vascularization and collagen fibers deposit, making them the crucial processes in tissue regeneration. Because of the multiple possible forms of cell extraction, there is no standardized protocol in dense regular connective tissue (DRCT). Many modifications of the structure, shape and composition of the bioscaffold have also been described to improve the therapeutic result following the implantation of decellularized connective tissue. The available data provide a valuable source of crucial information. However, the wide spectrum of decellularization makes it important to understand the key aspects of bioscaffolds relative to their potential use in tissue regeneration.

Application of decellularization-recellularization technique in plastic and reconstructive surgery

ABSTRACT

In the field of plastic and reconstructive surgery, the loss of organs or tissues caused by diseases or injuries has resulted in challenges, such as donor shortage and immunosuppression. In recent years, with the development of regenerative medicine, the decellularization-recellularization strategy seems to be a promising and attractive method to resolve these difficulties. The decellularized extracellular matrix contains no cells and genetic materials, while retaining the complex ultrastructure, and it can be used as a scaffold for cell seeding and subsequent transplantation, thereby promoting the regeneration of diseased or damaged tissues and organs. This review provided an overview of decellularization-recellularization technique, and mainly concentrated on the application of decellularization-recellularization technique in the field of plastic and reconstructive surgery, including the remodeling of skin, nose, ears, face, and limbs. Finally, we proposed the challenges in and the direction of future development of decellularization-recellularization technique in plastic surgery.

Decellularization: Leveraging a Tissue Engineering Technique for Food Production

The edible nature of many plants makes leaves particularly useful as scaffolds for the development of cultured meat, where animal tissue is grown in the laboratory setting. Recently, we demonstrated that decellularized spinach leaves can serve as scaffolds to grow and differentiate cells for cultured meat products. However, conventional decellularization methods use solutions that are not considered safe for use in food, such as organic solvents (hexanes) and detergents (triton X-100 (TX100)). This study modified decellularization protocols to incorporate detergents that are regulated (REG) by the United States Food and Drug Administration (FDA) for use in food, such as Polysorbate 20 (PS20), and eliminates the use of hexanes for cuticle removal. Spinach leaves were decellularized with sodium dodecyl sulfate and then with either TX100 (control) or PS20. The average DNA content for TX100 samples and PS20 samples was similar (1.3 ± 0.07 vs 1.3 ± 0.05 ng/mg; TX100 vs PS20, p = ns). The importance of cuticle removal was tested by removing hexanes from the protocol. Groups that included the cuticle removal step exhibited an average reduction in DNA content of approximately 91.7%, and groups that omitted the cuticle removal step exhibited an average reduction of approximately 90.3% (p = ns), suggesting that the omission of the cuticle removal step did not impede decellularization. Lastly, primary bovine satellite cells (PBSCs) were cultured for 7 days (d) on the surface of spinach leaves decellularized using the REG protocol. After the 7 d incubation period, PBSCs grown on the surface of REG scaffolds had an average viability of approximately 97.4%. These observations suggest that the REG protocol described in this study is an effective decellularization method, more closely adhering to food safety guidelines, that could be implemented in lab grown meat and alternative protein products.

Xeno-free culture and proliferation of hPSCs on 2D biomaterials

Human pluripotent stem cells (human embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs)) have unlimited proliferative potential, whereas adult stem cells such as bone marrow-derived stem cells and adipose-derived stem cells have problems with aging. When hPSCs are intended to be cultured on feeder-free or xeno-free conditions without utilizing mouse embryonic fibroblasts or human fibroblasts, they cannot be cultured on conventional tissue culture polystyrene dishes, as adult stem cells can be cultured but should be cultivated on material surfaces grafted or coated with (a) natural or recombinant extracellular matrix (ECM) proteins, (b) ECM protein-derived peptides and specific synthetic polymer surfaces in xeno-free and/or chemically defined conditions. This review describes current developing cell culture biomaterials for the proliferation of hPSCs while maintaining the pluripotency and differentiation potential of the cells into 3 germ layers. Biomaterials for the cultivation of hPSCs without utilizing a feeder layer are essential to decrease the risk of xenogenic molecules, which contributes to the potential clinical usage of hPSCs. ECM proteins such as human recombinant vitronectin, laminin-511 and laminin-521 have been utilized instead of Matrigel for the feeder-free cultivation of hPSCs. The following biomaterials are also discussed for hPSC cultivation: (a) decellularized ECM, (b) peptide-grafted biomaterials derived from ECM proteins, (c) recombinant E-cadherin-coated surface, (d) polysaccharide-immobilized surface, (e) synthetic polymer surfaces with and without bioactive sites, (f) thermoresponsive polymer surfaces with and without bioactive sites, and (g) synthetic microfibrous scaffolds.

Different Decellularization Methods in Bovine Lung Tissue Reveals Distinct Biochemical Composition, Stiffness, and Viscoelasticity in Reconstituted Hydrogels

Extracellular matrix (ECM)-derived hydrogels are in demand for use in lung tissue engineering to mimic the native microenvironment of cells in vitro. Decellularization of native tissues has been pursued for preserving organotypic ECM while eliminating cellular content and reconstitution into scaffolds which allows re-cellularization for modeling homeostasis, regeneration, or diseases. Achieving mechanical stability and understanding the effects of the decellularization process on mechanical parameters of the reconstituted ECM hydrogels present a challenge in the field. Stiffness and viscoelasticity are important characteristics of tissue mechanics that regulate crucial cellular processes and their in vitro representation in engineered models is a current aspiration. The effect of decellularization on viscoelastic properties of resulting ECM hydrogels has not yet been addressed. The aim of this study was to establish bovine lung tissue decellularization for the first time via pursuing four different protocols and characterization of reconstituted decellularized lung ECM hydrogels for biochemical and mechanical properties. Our data reveal that bovine lungs provide a reproducible alternative to human lungs for disease modeling with optimal retention of ECM components upon decellularization. We demonstrate that the decellularization method significantly affects ECM content, stiffness, and viscoelastic properties of resulting hydrogels. Lastly, we examined the impact of these aspects on viability, morphology, and growth of lung cancer cells, healthy bronchial epithelial cells, and patient-derived lung organoids.

The Canine Pancreatic Extracellular Matrix in Diabetes Mellitus and Pancreatitis: Its Essential Role and Therapeutic Perspective

Diabetes mellitus and pancreatitis are common pancreatic diseases in dogs, affecting the endocrine and exocrine portions of the organ. Dogs have a significant role in the history of research related to genetic diseases, being considered potential models for the study of human diseases. This review discusses the importance of using the extracellular matrix of the canine pancreas as a model for the study of diabetes mellitus and pancreatitis, in addition to focusing on the importance of using extracellular matrix in new regenerative techniques, such as decellularization and recellularization. Unlike humans, rabbits, mice, and pigs, there are no reports in the literature characterizing the healthy pancreatic extracellular matrix in dogs, in addition to the absence of studies related to matrix components that are involved in triggering diabetes melittus and pancreatitis. The extracellular matrix plays the role of physical support for the cells and allows the regulation of various cellular processes. In this context, it has already been demonstrated that physiologic and pathologic pancreatic changes lead to ECM remodeling, highlighting the importance of an in-depth study of the changes associated with pancreatic diseases.

The Development of Small-Caliber Vascular Grafts Using Human Umbilical Artery: An Evaluation of Methods

Due to the prevalence of cardiovascular disease in the United States, small-caliber vascular grafts for coronary bypass surgery continue to be in high demand. Human umbilical arteries, an underutilized resource, were decellularized using zwitterionic (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate [CHAPS]) and ionic (sodium dodecyl sulfate [SDS]) detergents and evaluated as potential vascular grafts. Vessels were tested for decellularization efficacy, mechanical integrity, and recellularization potential. Hematoxylin and eosin staining and DNA quantification revealed moderate to successful removal of cells in both conditions. While CHAPS-decellularized vessels displayed collagen structure most similar to intact tissue, both CHAPS- and SDS-decellularized vessels demonstrated burst pressures lower than that of intact tissue. Alcian Blue staining and sulfated glycosaminoglycan (sGAG) quantification indicated the preservation of sGAG content after both decellularization pathways. Both conditions were also capable of recellularization with human umbilical vein endothelial cells, and the use of a basic fibroblast growth factor treatment did not have a significant effect on the density of adhered cells after 5 days. Whole CHAPS-decellularized vessels were successfully recellularized. Additionally, an evaluation of the effects of freeze-thaw cycles was performed. In summary, human umbilical arteries present a promising alternative for small-caliber vascular grafts due to their high availability and ability to be decellularized and recellularized for safe and successful implantation. Impact Statement Coronary heart disease accounts for one of nine deaths in the United States each year. Bypass surgery has been shown to decrease the risk of heart attack; however, many patients do not have a suitable saphenous vein, which is required to redirect blood flow around their blocked arteries. In this study, we evaluate decellularized umbilical artery as a potential small-diameter vascular graft based on its mechanical properties and its recellularization potential.

Functional acellular matrix for tissue repair

In view of their low immunogenicity, biomimetic internal environment, tissue- and organ-like physicochemical properties, and functionalization potential, decellularized extracellular matrix (dECM) materials attract considerable attention and are widely used in tissue engineering. This review describes the composition of extracellular matrices and their role in stem-cell differentiation, discusses the advantages and disadvantages of existing decellularization techniques, and presents methods for the functionalization and characterization of decellularized scaffolds. In addition, we discuss progress in the use of dECMs for cartilage, skin, nerve, and muscle repair and the transplantation or regeneration of different whole organs (e.g., kidneys, liver, uterus, lungs, and heart), summarize the shortcomings of using dECMs for tissue and organ repair after refunctionalization, and examine the corresponding future prospects. Thus, the present review helps to further systematize the application of functionalized dECMs in tissue/organ transplantation and keep researchers up to date on recent progress in dECM usage.

Automated Assessment of Cell Infiltration and Removal in Decellularized Scaffolds - Experimental Study in Rabbits

Objective  Semiquantitative and automated measurement of nuclear material removal and cell infiltration in decellularized tendon scaffolds (DTSs). Method  16 pure New Zealand rabbits were used, and the gastrocnemius muscle tendon was collected bilaterally from half of these animals (16 tendons collected); 4 were kept as control and 12 were submitted to the decellularization protocol (DTS). Eight of the DTSs were used as an in vivo implant in the experimental rotator cuff tear (RCT) model, and the rest, as well as the controls, were used in the semiquantitative and automated evaluation of nuclear material removal. The eight additional rabbits were used to make the experimental model of RCT and subsequent evaluation of cellular infiltration after 2 or 8 weeks, within the DTS. Results  The semiquantitative and automated analysis used demonstrated a removal of 79% of nuclear material ( p  < 0.001 and power > 99%) and a decrease of 88% (p < 0.001 and power >99%) in the area occupied by nuclear material after the decellularization protocol. On cell infiltration in DTS, an increase of 256% (p < 0.001 and power >99%) in the number of cells within the DTS was observed in the comparison between 2 and 8 weeks postoperatively. Conclusion  The proposed semiquantitative and automated measurement method was able to objectively measure the removal of nuclear material and cell infiltration in DTS.

Preparation and Application of Decellularized ECM-Based Biological Scaffolds for Articular Cartilage Repair: A Review

Cartilage regeneration is dependent on cellular-extracellular matrix (ECM) interactions. Natural ECM plays a role in mechanical and chemical cell signaling and promotes stem cell recruitment, differentiation and tissue regeneration in the absence of biological additives, including growth factors and peptides. To date, traditional tissue engineering methods by using natural and synthetic materials have not been able to replicate the physiological structure (biochemical composition and biomechanical properties) of natural cartilage. Techniques facilitating the repair and/or regeneration of articular cartilage pose a significant challenge for orthopedic surgeons. Whereas, little progress has been made in this field. In recent years, with advances in medicine, biochemistry and materials science, to meet the regenerative requirements of the heterogeneous and layered structure of native articular cartilage (AC) tissue, a series of tissue engineering scaffolds based on ECM materials have been developed. These scaffolds mimic the versatility of the native ECM in function, composition and dynamic properties and some of which are designed to improve cartilage regeneration. This review systematically investigates the following: the characteristics of cartilage ECM, repair mechanisms, decellularization method, source of ECM, and various ECM-based cartilage repair methods. In addition, the future development of ECM-based biomaterials is hypothesized.

Decellularization in Tissue Engineering and Regenerative Medicine: Evaluation, Modification, and Application Methods

Reproduction of different tissues using scaffolds and materials is a major element in regenerative medicine. The regeneration of whole organs with decellularized extracellular matrix (dECM) has remained a goal despite the use of these materials for different purposes. Recently, decellularization techniques have been widely used in producing scaffolds that are appropriate for regenerating damaged organs and may be able to overcome the shortage of donor organs. Decellularized ECM offers several advantages over synthetic compounds, including the preserved natural microenvironment features. Different decellularization methods have been developed, each of which is appropriate for removing cells from specific tissues under certain conditions. A variety of methods have been advanced for evaluating the decellularization process in terms of cell removal efficiency, tissue ultrastructure preservation, toxicity, biocompatibility, biodegradability, and mechanical resistance in order to enhance the efficacy of decellularization methods. Modification techniques improve the characteristics of decellularized scaffolds, making them available for the regeneration of damaged tissues. Moreover, modification of scaffolds makes them appropriate options for drug delivery, disease modeling, and improving stem cells growth and proliferation. However, considering different challenges in the way of decellularization methods and application of decellularized scaffolds, this field is constantly developing and progressively moving forward. This review has outlined recent decellularization and sterilization strategies, evaluation tests for efficient decellularization, materials processing, application, and challenges and future outlooks of decellularization in regenerative medicine and tissue engineering.

Decellularized extracellular matrix scaffolds: Recent trends and emerging strategies in tissue engineering

The application of scaffolding materials is believed to hold enormous potential for tissue regeneration. Despite the widespread application and rapid advance of several tissue-engineered scaffolds such as natural and synthetic polymer-based scaffolds, they have limited repair capacity due to the difficulties in overcoming the immunogenicity, simulating in-vivo microenvironment, and performing mechanical or biochemical properties similar to native organs/tissues. Fortunately, the emergence of decellularized extracellular matrix (dECM) scaffolds provides an attractive way to overcome these hurdles, which mimic an optimal non-immune environment with native three-dimensional structures and various bioactive components. The consequent cell-seeded construct based on dECM scaffolds, especially stem cell-recellularized construct, is considered an ideal choice for regenerating functional organs/tissues. Herein, we review recent developments in dECM scaffolds and put forward perspectives accordingly, with particular focus on the concept and fabrication of decellularized scaffolds, as well as the application of decellularized scaffolds and their combinations with stem cells (recellularized scaffolds) in tissue engineering, including skin, bone, nerve, heart, along with lung, liver and kidney.

Engineering of Tracheal Grafts Based on Recellularization of Laser-Engraved Human Airway Cartilage Substrates

OBJECTIVE

Implantation of tissue-engineered tracheal grafts represents a visionary strategy for the reconstruction of tracheal wall defects after resections and may develop into a last chance for a number of patients with severe cicatricial stenosis. The use of a decellularized tracheal substrate would offer an ideally stiff graft, but the matrix density would challenge efficient remodeling into a living cartilage. In this study, we hypothesized that the pores of decellularized laser-perforated tracheal cartilage (LPTC) tissues can be colonized by adult nasal chondrocytes (NCs) to produce new cartilage tissue suitable for the repair of tracheal defects.

DESIGN

Human, native tracheal specimens, isolated from cadaveric donors, were exposed to decellularized and laser engraving-controlled superficial perforation (300 μm depth). Human or rabbit NCs were cultured on the LPTCs for 1 week. The resulting revitalized tissues were implanted ectopically in nude mice or orthotopically in tracheal wall defects in rabbits. Tissues were assayed histologically and by microtomography analyses before and after implantation.

RESULTS

NCs were able to efficiently colonize the pores of the LPTCs. The extent of colonization (i.e., percentage of viable cells spanning >300 μm of tissue depth), cell morphology, and cartilage matrix deposition improved once the revitalized constructs were implanted ectopically in nude mice. LPTCs could be successfully grafted onto the tracheal wall of rabbits without any evidence of dislocation or tracheal stenosis, 8 weeks after implantation. Rabbit NCs, within the LPTCs, actively produced new cartilage matrix.

CONCLUSION

Implantation of NC-revitalized LPTCs represents a feasible strategy for the repair of tracheal wall defects.

Decellularization for the retention of tissue niches

Decellularization of natural tissues to produce extracellular matrix is a promising method for three-dimensional scaffolding and for understanding microenvironment of the tissue of interest. Due to the lack of a universal standard protocol for tissue decellularization, recent investigations seek to develop novel methods for whole or partial organ decellularization capable of supporting cell differentiation and implantation towards appropriate tissue regeneration. This review provides a comprehensive and updated perspective on the most recent advances in decellularization strategies for a variety of organs and tissues, highlighting techniques of chemical, physical, biological, enzymatic, or combinative-based methods to remove cellular contents from tissues. In addition, the review presents modernized approaches for improving standard decellularization protocols for numerous organ types.

Efficient Decellularization by Application of Moderate High Hydrostatic Pressure with Supercooling Pretreatment

Decellularized tissues are considered superior scaffolds for cell cultures, preserving the microstructure of native tissues and delivering many kinds of cytokines. High hydrostatic pressure (HHP) treatment could remove cells physically from biological tissues rather than chemical methods. However, there are some risks of inducing destruction or denaturation of extracellular matrices (ECMs) at an ultrahigh level of HHP. Therefore, efficient decellularization using moderate HHP is required to remove almost all cells simultaneously to suppress tissue damage. In this study, we proposed a novel decellularization method using a moderate HHP with supercooling pretreatment. To validate the decellularization method, a supercooling device was developed to incubate human dermal fibroblasts or collagen gels in a supercooled state. The cell suspension and collagen gels were subjected to 100, 150, and 200 MPa of HHP after supercooling pretreatment, respectively. After applying HHP, the viability and morphology of the cells and the collagen network structure of the gels were evaluated. The viability of cells decreased dramatically after HHP application with supercooling pretreatment, whereas the microstructures of collagen gels were preserved and cell adhesivity was retained after HHP application. In conclusion, it was revealed that supercooling pretreatment promoted the denaturation of the cell membrane to improve the efficacy of decellularization using static application of moderate HHP. Furthermore, it was demonstrated that the HHP with supercooling pretreatment did not degenerate and damage the microstructure in collagen gels.

Rho/ROCK Inhibition Promotes TGF-β3-Induced Tenogenic Differentiation in Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSC) represent a promising therapeutic tool for tendon regeneration. Their tenogenic differentiation is crucial for tissue engineering approaches and may support their beneficial effects after cell transplantation in vivo. The transforming growth factor (TGF)-β, signalling via intracellular Smad molecules, is a potent paracrine mediator of tenogenic induction. Moreover, scaffold topography or tendon matrix components induced tenogenesis via activation of the Rho/ROCK cascade, which, however, is also involved in pathological adaptations in extracellular matrix pathologies. The aim of this study was to investigate the interplay of Rho/ROCK and TGF-β3/Smad signalling in tenogenic differentiation in both human and equine MSC. Primary equine and human MSC isolated from adipose tissue were cultured as monolayers or on tendon-derived decellularized scaffolds to evaluate the influence of the ROCK inhibitor Y-27632 on TGF-β3-induced tenogenic differentiation. The MSC were incubated with and without TGF-β3 (10 ng/ml), Y-27632 (10 μM), or both. On day 1 and day 3, the signalling pathway of TGF-β and the actin cytoskeleton were visualized by Smad 2/3 and phalloidin staining, and gene expression of signalling molecules and tendon markers was assessed. ROCK inhibition was confirmed by disruption of the actin cytoskeleton. Activation of Smad 2/3 with nuclear translocation was evident upon TGF-β3 stimulation. Interestingly, this effect was most pronounced with additional ROCK inhibition in both species (p < 0.05 in equine MSC). In line with that, the tendon marker scleraxis showed the strongest upregulation when TGF-β3 and ROCK inhibition were combined (p < 0.05 in human MSC). The regulation pattern of tendon extracellular matrix components and the signalling molecules TGF-β3 and Smad 8 showed differences between human and equine MSC. The obtained results showed that ROCK inhibition promotes the TGF-β3/Smad 2/3 axis, with possible implications for future MSC priming regimes in tendon therapy.

Host Response to Biomaterials for Cartilage Tissue Engineering: Key to Remodeling

Biomaterials play a core role in cartilage repair and regeneration. The success or failure of an implanted biomaterial is largely dependent on host response following implantation. Host response has been considered to be influenced by numerous factors, such as immune components of materials, cytokines and inflammatory agents induced by implants. Both synthetic and native materials involve immune components, which are also termed as immunogenicity. Generally, the innate and adaptive immune system will be activated and various cytokines and inflammatory agents will be consequently released after biomaterials implantation, and further triggers host response to biomaterials. This will guide the constructive remolding process of damaged tissue. Therefore, biomaterial immunogenicity should be given more attention. Further understanding the specific biological mechanisms of host response to biomaterials and the effects of the host-biomaterial interaction may be beneficial to promote cartilage repair and regeneration. In this review, we summarized the characteristics of the host response to implants and the immunomodulatory properties of varied biomaterial. We hope this review will provide scientists with inspiration in cartilage regeneration by controlling immune components of biomaterials and modulating the immune system.

Distinct chemical composition and enzymatic treatment induced human endothelial cells survival in acellular ovine aortae

Objective

The current experiment aimed to assess the impact of detergents such as 3% Triton X-100, 1% peracetic acid, 1% Tween-20, and 1% SDS in combination with Trypsin–EDTA on acellularization of ovine aortae after 7 days.

Results

Hematoxylin–Eosin staining showed an appropriate acellularization rate in ovine aortae, indicated by a lack of cell nuclei in the tunica media layer. DAPI staining confirmed the lack of nuclei in the vascular wall after being exposed to the combination of chemical and enzymatic solutions. Verhoeff-Van Gieson staining showed that elastin fibers were diminished in acellular samples compared to the control group while collagen stands were unchanged. CCK-8 survival assay showed enhanced viability in human umbilical vein endothelial cells 5 days after being cultured on decellularized samples compared to the cells cultured on a plastic surface (p < 0.05). SEM imaging showed flattening of endothelial cells on the acellular surface.

A 3D Dynamic In Vitro Model of Inflammatory Tendon Disease

Three-dimensional (3D) cell cultures combining multipotent mesenchymal stromal cells (MSC), tendon extracellular matrix scaffolds, and mechanical stimulation by a bioreactor have been used to induce tenogenic differentiation in vitro. Yet, these conditions alone do not mimic the environment of acute inflammatory tendon disease adequately, thus the results of such studies are not representatives for tendon regeneration after acute injury. In this chapter, we describe two different approaches to introduce inflammatory stimuli, comprising co-culture with leukocytes and supplementation with the cytokines IL-1 β and TNF-α. The presented in vitro model of inflammatory tendon disease could be used to study musculoskeletal pathophysiology and regeneration in more depth.

Contribution of Physical Methods in Decellularization of Animal Tissues

Biologic scaffolds composed of extracellular matrix (ECM) are frequently used for clinical purposes of tissue regeneration. Different methods have been developed for this purpose. All methods of decellularization including chemical and physical approaches leave some damage on the ECM; however, the effects of these methods are different which make some of these procedures more proper to maintain ECM structure than other methods. This review is aimed to introduce and compare new physical methods for the decellularization of different tissues and organs in tissue engineering. All recent reports and research that have used at least one physical method in the procedure of decellularization, were included and evaluated in this paper. The advantages and drawbacks of each method were examined and compared considering the effectiveness. This review tried to highlight the prospective potentials and benefits of applying physical methods for decellularization protocols in tissue engineering instead of the current chemical methods. These chemical methods are harsh in nature and were shown to be destructive and harmful to essential substances of ECM and scaffold structure. Therefore, using physical methods as a partial or even a whole protocol could save time, costs, and quality of the final acellular tissue in complicated decellularization procedures. Moreover, regarding the control factor that could be achieved easily with physical methods, optimization of different decellularization protocols would be quite satisfactory. Combined methods take advantage of both chemical and physical approaches.

Fundamental Study of Decellularization Method Using Cyclic Application of High Hydrostatic Pressure

Decellularized tissues are promising materials that mainly consist of extracellular matrices (ECMs) obtained by removing all cells from organs and tissues. High hydrostatic pressure (HHP) has been used for decellularization to remove cells physically from organs or tissues rather than by chemical methods. However, ultrahigh pressure induces denaturation of the ECM structure. In this study, we examined the effects of cyclic HHP at low and high pressures on the cell membrane structure to establish a novel decellularization method that enables decellularization without the denaturation of the ECM. A decellularization device using cyclic HHP (maximum pressure: 250 MPa, cycle number: 5) was developed. NB1RGB cell suspension was injected into a plastic bag to be subjected to cyclic HHP. After applying cyclic HHP, the amount of DNA inside the cells and the morphological changes of the cells were evaluated. As a result, the amount of DNA inside the cells decreased after the cyclic HHP compared to the static HHP. In addition, cyclic HHP was suggested to promote the destruction of the cell and nuclear membrane. In conclusion, it was revealed that the cell structure could be denatured and destroyed by cyclic HHP at a lower level than that of previous approaches.

Tissue-Specific Decellularization Methods: Rationale and Strategies to Achieve Regenerative Compounds

The extracellular matrix (ECM) is a complex network with multiple functions, including specific functions during tissue regeneration. Precisely, the properties of the ECM have been thoroughly used in tissue engineering and regenerative medicine research, aiming to restore the function of damaged or dysfunctional tissues. Tissue decellularization is gaining momentum as a technique to obtain potentially implantable decellularized extracellular matrix (dECM) with well-preserved key components. Interestingly, the tissue-specific dECM is becoming a feasible option to carry out regenerative medicine research, with multiple advantages compared to other approaches. This review provides an overview of the most common methods used to obtain the dECM and summarizes the strategies adopted to decellularize specific tissues, aiming to provide a helpful guide for future research development.

A novel decellularization method to produce brain scaffolds

Scaffolds composed of extracellular matrix (ECM) can assist tissue remodeling and repair following injury. The ECM is a complex biomaterial composed of proteins, glycoproteins, proteoglycans, and glycosaminoglycans, secreted by cells. The ECM contains fundamental biological cues that modulate cell behavior and serves as a structural scaffold for cell adhesion and growth. For clinical applications, where immune rejection is a constraint, ECM can be processed using decellularization methods intended to remove cells and donor antigens from tissue or organs, while preserving native biological cues essential for cell growth and differentiation. Recent studies show bioengineered organs composed by a combination of a diversity of materials and stem cells as a possibility of new therapeutic strategies to treat diseases that affect different tissues and organs, including the central nervous system (CNS). Nevertheless, the methodologies currently described for brain decellularization involve the use of several chemical reagents with many steps that ultimately limit the process of organ or tissue recellularization. Here, we describe for the first time a fast and straightforward method for complete decellularization of mice brain by the combination of rapid freezing and thawing following the use of only one detergent (Sodium dodecyl sulfate (SDS)). Our data show that using the protocol we describe here, the brain was entirely decellularized, while still maintaining ECM components that are essential for cell survival on the scaffold. Our results also show the cell-loading of the decellularized brain matrix with Neuro2a cells, which were identified by immunohistochemistry in their undifferentiated form. We conclude that this novel and simple method for brain decellularization can be used as a scaffold for cell-loading.

Exploiting crosslinked decellularized matrix to achieve uterus regeneration and construction

Decellularized extracellular matrix (dECM) has been considered as a promising scaffold in xenotransplantation, yet natural tissue dECM is often mechanically weak and rapidly degraded, compromising the outcomes. How to restore the mechanical strength and optimise the in vivo degradation, but maintain the microstructure and maximumly suppress the immune rejection, remains challenging. For this aim, we prepared and characterised various crosslinked decellularized rabbit uterus matrix (dUECM) and evaluated in vivo performance after uterus xenotransplantation from rabbit to rat. Naturally derived genipin (GP) and procyanidins (PC) were chosen to crosslink the dUECM, producing significant mechanical enhanced crosslinked-dUECM along with prolonged enzymatic degradation rate. Xenogeneic subcutaneous graft studies revealed that PC- and GP-crosslinked dUECM experienced significant cell infiltration and caused low immune reactions, indicating the desired biocompatibility. In vivo transplantation of GP- and PC-crosslinked dUECM to a uterus circular excised rat yielded excellent recellularization ability and promoted uterus regeneration after 90 days. While the reconstruction efficacy of crosslinked dUECM is highly depended on the crosslinking degree, crosslinking condition must be carefully evaluated to balance the role of crosslinked dECM in mechanical and biological support for tissue regeneration promotion.

In Vitro Biocompatibility of Decellularized Cultured Plant Cell-Derived Matrices

There has been a recent increase in exploring the use of decellularized plant tissue as a novel "green" material for biomedical applications. As part of this effort, we have developed a technique to decellularize cultured plant cells (tobacco BY-2 cells and rice cells) and tissue (tobacco hairy roots) that uses deoxyribonuclease I (DNase I)). As a proof of concept, all cultured plant cells and tissue were transformed to express recombinant enhanced green fluorescent protein (EGFP) to show that the proteins of interest could be retained within the matrices. Decellularization of lyophilized tobacco BY-2 cells with DNase for 30 min depleted the DNA content from 1503 ± 459 to 31 ± 5 ng/sample. The decellularization procedure resulted in approximately 36% total protein retention (154 ± 60 vs 424 ± 70 μg/sample) and 33% EGFP retention. Similar results for DNA removal and protein retention were observed with the rice cells and tobacco hairy root matrices. When exposed to decellularized BY-2 cell-derived matrices, monolayer cultures of human foreskin fibroblasts (hFFs) maintained or increased metabolic activity, which is an indicator of cell viability. Furthermore, hFFs were able to attach, spread, and proliferate when cultured with the decellularized BY-2 cell-derived matrices in an aggregate model. Overall, these studies demonstrate that cultured plant cells and tissue can be effectively decellularized with DNase I with substantial protein retention. The resulting material has a positive impact on hFF metabolic activity and could be employed to create a three-dimensional environment for cell growth. These results thus show the promise of using naturally derived cellulose matrices from cultured plant cells and tissues for biomedical applications.

Forced Unfolding of Proteins Directs Biochemical Cascades

Many proteins in cells and in the extracellular matrix assemble into force-bearing networks, and some proteins clearly transduce mechanical stimuli into biochemical signals. Although structural mechanisms remain poorly understood, the designs of such proteins enable mechanical forces to either inhibit or facilitate interactions of protein domains with other proteins, including small molecules and enzymes, including proteases and kinases. Here, we review some of the structural proteins and processes that exhibit distinct modes of force-dependent signal conversion.

Determination of antibiotic impurities in good manufacturing practices-grade cell therapy medicinal products

Backrounds: According to the regulations of the health autorities, cell-based therapy products must be manufactured in good manufacturing production (GMP) facilities, fulfilling the required GMP standards. Products developed under the high quality control (QC) necessarity need to be approved for some QC tests. One of the main residual test is antibiotic test and this test should be validated. The aim of this study is to validate and determine the methods of detection of the antibiotic residue in the final product.Methods: Liquid Chromatography Tandem-Mass Spectrometry (LC-MS/MS) methods were used for the main steps of the production procedure, as well as the final products. Pharmaceutical Grade penicillin G and streptomycin sulfate were used as positive controls.Results: The results suggest that penicillin is broken down during cell culture and streptomycin is eliminated at the first washing step of the final product manufacture. It is shown in this study that LC-MS/MS method is one of the convenient method to test residual anibiotics and can be used to detect the antibiotic residues in cellular therapy products.Discussion: Since the antibiotic residues are eliminated in the final product and also it could be suggested that the methodology we followed is sufficiently safe and final product is pure.

Recent Trends in Decellularized Extracellular Matrix Bioinks for 3D Printing: An Updated Review

The promise of regenerative medicine and tissue engineering is founded on the ability to regenerate diseased or damaged tissues and organs into functional tissues and organs or the creation of new tissues and organs altogether. In theory, damaged and diseased tissues and organs can be regenerated or created using different configurations and combinations of extracellular matrix (ECM), cells, and inductive biomolecules. Regenerative medicine and tissue engineering can allow the improvement of patients' quality of life through availing novel treatment options. The coupling of regenerative medicine and tissue engineering with 3D printing, big data, and computational algorithms is revolutionizing the treatment of patients in a huge way. 3D bioprinting allows the proper placement of cells and ECMs, allowing the recapitulation of native microenvironments of tissues and organs. 3D bioprinting utilizes different bioinks made up of different formulations of ECM/biomaterials, biomolecules, and even cells. The choice of the bioink used during 3D bioprinting is very important as properties such as printability, compatibility, and physical strength influence the final construct printed. The extracellular matrix (ECM) provides both physical and mechanical microenvironment needed by cells to survive and proliferate. Decellularized ECM bioink contains biochemical cues from the original native ECM and also the right proportions of ECM proteins. Different techniques and characterization methods are used to derive bioinks from several tissues and organs and to evaluate their quality. This review discusses the uses of decellularized ECM bioinks and argues that they represent the most biomimetic bioinks available. In addition, we briefly discuss some polymer-based bioinks utilized in 3D bioprinting.

Recent development and biomedical applications of decellularized extracellular matrix biomaterials

Decellularized matrix (dECM) is isolated extracellular matrix of tissues from its original inhabiting cells, which has emerged as a promising natural biomaterial for tissue engineering, aiming at support, replacement or regeneration of damaged tissues. The dECM can be easily obtained from tissues/organs of various species by adequate decellularization methods, and mimics the structure and composition of the native extracellular matrix, providing a favorable cellular environment. In this review, we summarize the recent developments in the preparation of dECM materials, including decellularization, crosslinking and sterilization. Also, we cover the advances in the utilization of dECM biomaterials in regeneration medicine in pre-clinic and clinical trials. Moreover, we highlight those emerging medical benefits of dECM beyond tissue engineering, such as cell transplantation, in vitro/in vivo model and therapeutic cues delivery. With the advances in the preparation and broader application, the dECM biomaterials could become the gold scaffold and pharmaceutical excipients in medical sciences.

Artificial controlled model of blood circulation system for adhesive evaluation

Since there are several casualties due to uncontrolled bleeding resulting from simple injury to surgery, effective styptic or vessel adhesives are important; however, their development is limited by the lack of standardized systems to evaluate potential compounds. The current study outlines the development of an aorta styptic evaluation system, comprising of decellularized swine aorta tissue and a heart pump-mimicking system. Although the cells in the swine aorta were removed, the structural stability of the aorta was sustained due to the maintenance of the extracellular matrix. Using a control adhesive, Cyanoacrylate, the developed model was found to have similar adhesive efficacy to intact aorta. The circulatory-mimicking system was designed to mimic the beat rate and strength of blood-flow from the heart, which was necessary to evaluate the adherent efficacy. The decellularized aorta improves instabilities of intact tissues, which occurs on account of storage and origin, thereby allowing for a more standardized system. The system was able to simulate several symptoms of circulation, according to patient age and health, by adjusting pumping frequency and intensity. Therefore, this system can be used as a standardized evaluation system for screening adhesives. Further, it would also evaluate other medical devices, such as stent or medications.

Decellularization of Large Tendon Specimens: Combination of Manually Performed Freeze-Thaw Cycles and Detergent Treatment

Reliable decellularization techniques applicable to tendon tissue play a critical role in the field of current tissue engineering. Particularly, an application as three-dimensional culture model for in vitro research and translational approaches to establish graft-based tendon repair as a routine clinical tool represent two main application fields for decellularized tendon scaffolds. Considering methodological issues of tendon decellularization, one of the major challenges lies in the preservation of the tendon-specific extracellular matrix (ECM) architecture to reflect natural tissue characteristic as best as possible. Concurrently, further requirements for high-quality decellularized biological tendon scaffolds include not only the reduction of resident cells, but also an ensured cytocompatibility.To date, a large number and a wide variety of decellularization protocols for natural tendon tissue have already been investigated and usually, physical as well as chemical and/or enzyme-based treatments are used for the purpose of decellularization. However, to the best of our knowledge, there is a lack of evidence-based protocols for the processing of full-thickness large tendon samples, such as the equine flexor tendons.Therefore, the here presented protocol describes a reliable procedure to decellularize equine superficial digital flexor tendons by using a combined treatment of physical decellularization in the form of repetitive freeze-thaw cycles, and of chemical decellularization with the non-ionic detergent Triton X-100. The decellularization effectiveness evaluated by reduction of cell and DNA content, the influence of decellularization on the morphology of the tendon extracellular matrix (ECM) as well as the cytocompatibility of the decellularized tendon scaffolds obtained have been investigated previously. Based on this previous study, the here present protocol is an effective procedure, particularly applicable for large tendon specimens.