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The dura mater protects underlying tissues and cerebrospinal fluid, but dural abnormalities can cause leaking and meningitis and wound infections. This review emphasizes the relevance of dural repair and the progress of dural reconstruction materials, focusing on biological scaffolds. A comprehensive assessment of dural substitution literature focused on composite, acellular, natural, synthetic, and homologous materials. Decellularized dura scaffolds as viable natural biomaterials for tissue engineering are explored in this overview of these materials' properties, effectiveness, and therapeutic uses. The evaluation also compares materials and assesses host tissue response in preclinical and clinical studies. The review highlights various dural substitution findings. There is no gold standard for dural repair, despite the variety of materials used. Replicating natural dura mater's mechanical and structural qualities is difficult. Recent research suggests that decellularized dura scaffolds can regenerate tissue while reducing inflammation and transplant rejection. Furthermore, the movement toward personalized medicine in this sector suggests that bespoke alternatives might be chosen depending on patient characteristics, improving treatment effects. Synthesizing dural replacement research and clinical uses in this review adds to knowledge. It tackles standard materials' shortcomings and shows how biological scaffolds might improve dural repair. The analysis opens the door to personalized dural repair research that might enhance patient outcomes and advance neurosurgery. The insights presented herein highlight the intriguing prospects for appropriate dural restorative materials, seeking to improve dural defect treatment. [ABSTRACT FROM AUTHOR]

Conventional methods have failed to show the ability of articular cartilage to completely restore. Decellularized extracellular matrix has achieved interest as a potential biomaterial for cartilage tissue engineering approaches. The decellularized cartilage-derived matrix (CDM) scaffolds retain the native composition of cartilage tissue, providing a conducive microenvironment for cellular growth and differentiation, while exhibit limited mechanical support. Our investigation involved the fabrication of a new hybrid CDM- polyvinyl alcohol (PVA) hydrogel scaffold with four different concentrations (5%, 10%, 15%, and 20%), followed by a comprehensive characterization of the construct's physicochemical, mechanical, and biological properties to elucidate their potential in cartilage regeneration applications. Our results demonstrated that hybridization of the CDM with PVA enhanced the mechanical properties besides ensuring biocompatibility. FTIR and DSC results also confirmed the mechanical improvements in hybrid scaffolds. The hybrid CDM/PVA (15%/5%, 15%/10%, 15%/15%, and 15%/20%) scaffolds showed significantly different compressive strengths (p < 0.0001, p < 0.0004, p < 0.0001, p < 0.012 respectively). Moreover, resazurin test showed cell attachment and growth on all four types of hybrid scaffolds during seven days of three dimensional culture. The cross-linked CDM15%/PVA5% group, demonstrated acceptable mechanical strength, pore size, physicochemical properties, swelling behavior, and cell growth and attachment. Our data indicate that our hybrid CDM/PVA scaffold possess bioactive properties suitable for a promising candidate for cartilage tissue engineering studies. [ABSTRACT FROM AUTHOR]

Motor functional improvement represents a paramount treatment objective in the post-spinal cord injury (SCI) recovery process. However, neuronal cell death and axonal degeneration following SCI disrupt neural signaling, impeding the motor functional recovery. In this study, we developed a multifunctional decellularized spinal cord-derived extracellular matrix (dSECM), crosslinked with glial cell-derived neurotrophic factor (GDNF), to promote differentiation of stem cells into neural-like cells and facilitate axonogenesis and remyelination. After decellularization, the immunogenic cellular components were effectively removed in dSECM, while the crucial protein components were retained which supports stem cells proliferation and differentiation. Furthermore, sustained release of GDNF from the dSECM facilitated axonogenesis and remyelination by activating the PI3K/Akt and MEK/Erk pathways. Our findings demonstrate that the dSECM-GDNF platform promotes neurogenesis, axonogenesis, and remyelination to enhance neural signaling, thereby yielding promising therapeutic effects for motor functional improvement after SCI. The dSECM promotes the proliferation and differentiation of MSCs or NSCs by retaining proteins associated with positive regulation of neurogenesis and neuronal differentiation, while eliminating proteins related to negative regulation of neurogenesis. After crosslinking, GDNF can be gradually released from the platform, thereby promoting neural differentiation, axonogenesis, and remyelination to enhance neural signaling through activation of the PI3K/Akt and MEK/Erk pathways. In vivo experiments demonstrated that dSECM-GDNF/MSC@GelMA hydrogel exhibited the ability to facilitate neuronal regeneration at 4 weeks post-surgery, while promoting axonogenesis and remyelination at 8 weeks post-surgery, ultimately leading to enhanced motor functional recovery. This study elucidates the ability of neural regeneration strategy to promote motor functional recovery and provides a promising approach for designing multifunctional tissue for SCI treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

The extracellular matrix (ECM) is a three-dimensional, acellular network of diverse structural and nonstructural proteins embedded within a gel-like ground substance composed of glycosaminoglycans and proteoglycans. The ECM serves numerous roles that vary according to the tissue in which it is situated. In the myocardium, the ECM acts as a collagen-based scaffold that mediates the transmission of contractile signals, provides means for paracrine signaling, and maintains nutritional and immunologic homeostasis. Given this spectrum, it is unsurprising that both the composition and role of the ECM has been found to be modulated in the context of cardiac pathology. Myocardial infarction (MI) provides a familiar example of this; the ECM changes in a way that is characteristic of the progressive phases of post-infarction healing. In recent years, this involvement in infarct pathophysiology has prompted a search for therapeutic targets: if ECM components facilitate healing, then their manipulation may accelerate recovery, or even reverse pre-existing damage. This possibility has been the subject of numerous efforts involving the integration of ECM-based therapies, either derived directly from biologic sources or bioengineered sources, into models of myocardial disease. In this paper, we provide a thorough review of the published literature on the use of the ECM as a novel therapy for ischemic heart disease, with a focus on biologically derived models, of both the whole ECM and the components thereof. [ABSTRACT FROM AUTHOR]

Decellularized matrices derived from diseased tissues/organs have evolved in the most recent years, providing novel research perspectives for understanding disease occurrence and progression and providing accurate pseudo models for developing new disease treatments. Although decellularized matrix maintaining the native composition, ultrastructure, and biomechanical characteristics of extracellular matrix (ECM), alongside intact and perfusable vascular compartments, facilitates the construction of bioengineered organ explants in vitro and promotes angiogenesis and tissue/organ regeneration in vivo, the availability of healthy tissues and organs for the preparation of decellularized ECM materials is limited. In this paper, we review the research advancements in decellularized diseased matrices. Considering that current research focuses on the matrices derived from cancers and fibrotic organs (mainly fibrotic kidney, lungs, and liver), the pathological characterizations and the applications of these diseased matrices are mainly discussed. Additionally, a contrastive analysis between the decellularized diseased matrices and decellularized healthy matrices, along with the development in vitro 3D models, is discussed in this paper. And last, we have provided the challenges and future directions in this review. Deep and comprehensive research on decellularized diseased tissues and organs will promote in‐depth exploration of source materials in tissue engineering field, thus providing new ideas for clinical transformation. [ABSTRACT FROM AUTHOR]

Abstract Decellularized matrices derived from diseased tissues/organs have evolved in the most recent years, providing novel research perspectives for understanding disease occurrence and progression and providing accurate pseudo models for developing new disease treatments. Although decellularized matrix maintaining the native composition, ultrastructure, and biomechanical characteristics of extracellular matrix (ECM), alongside intact and perfusable vascular compartments, facilitates the construction of bioengineered organ explants in vitro and promotes angiogenesis and tissue/organ regeneration in vivo, the availability of healthy tissues and organs for the preparation of decellularized ECM materials is limited. In this paper, we review the research advancements in decellularized diseased matrices. Considering that current research focuses on the matrices derived from cancers and fibrotic organs (mainly fibrotic kidney, lungs, and liver), the pathological characterizations and the applications of these diseased matrices are mainly discussed. Additionally, a contrastive analysis between the decellularized diseased matrices and decellularized healthy matrices, along with the development in vitro 3D models, is discussed in this paper. And last, we have provided the challenges and future directions in this review. Deep and comprehensive research on decellularized diseased tissues and organs will promote in‐depth exploration of source materials in tissue engineering field, thus providing new ideas for clinical transformation.

The extracellular matrix (ECM) is a three-dimensional, acellular network of diverse structural and nonstructural proteins embedded within a gel-like ground substance composed of glycosaminoglycans and proteoglycans. The ECM serves numerous roles that vary according to the tissue in which it is situated. In the myocardium, the ECM acts as a collagen-based scaffold that mediates the transmission of contractile signals, provides means for paracrine signaling, and maintains nutritional and immunologic homeostasis. Given this spectrum, it is unsurprising that both the composition and role of the ECM has been found to be modulated in the context of cardiac pathology. Myocardial infarction (MI) provides a familiar example of this; the ECM changes in a way that is characteristic of the progressive phases of post-infarction healing. In recent years, this involvement in infarct pathophysiology has prompted a search for therapeutic targets: if ECM components facilitate healing, then their manipulation may accelerate recovery, or even reverse pre-existing damage. This possibility has been the subject of numerous efforts involving the integration of ECM-based therapies, either derived directly from biologic sources or bioengineered sources, into models of myocardial disease. In this paper, we provide a thorough review of the published literature on the use of the ECM as a novel therapy for ischemic heart disease, with a focus on biologically derived models, of both the whole ECM and the components thereof.

Abstract Stem cells transplantation is the main method of tissue engineering regeneration treatment, the viability and therapeutic efficiency are limited. Scaffold materials also play an important role in tissue engineering, whereas there are still many limitations, such as rejection and toxic side effects caused by scaffold materials. Cell sheet engineering is a scaffold-free tissue technology, which avoids the side effects of traditional scaffolds and maximizes the function of stem cells. It is increasingly being used in the field of tissue regenerative medicine. Dental-derived mesenchymal stem cells (DMSCs) are multipotent cells that exist in various dental tissues and can be used in stem cell-based therapy, which is impactful in regenerative medicine. Emerging evidences show that cell sheets derived from DMSCs have better effects in the field of regenerative medicine applications. Extracellular matrix (ECM) is the main component of cell sheets, which is a dynamic repository of signalling biological molecules and has a variety of biological functions and may play an important role in the application of cell sheets. In this review, we summarized the application status, mechanisms that sheets and ECM may play and future prospect of DMSC sheets on regeneration medicine.

Small-diameter vascular grafts (diameter

Abstract Background The ideal conduit for repair of the right ventricular outflow tract (RVOT) during the Ross procedure remains unclear and has yet to be fully elucidated. We perform a pairwise meta-analysis to compare the short-term and long-term outcomes of decellularized versus cryopreserved pulmonary allografts for RVOT reconstruction during the Ross procedure. Main body After a comprehensive literature search, studies comparing decellularized and cryopreserved allografts for patients undergoing RVOT reconstruction during the Ross procedure were pooled to perform a pairwise meta-analysis using the random-effects model. Primary outcomes were early mortality and follow-up allograft dysfunction. Secondary outcomes were reintervention rates and follow-up endocarditis. A total of 4 studies including 1687 patients undergoing RVOT reconstruction during the Ross procedure were included. A total of 812 patients received a decellularized pulmonary allograft, while 875 received a cryopreserved pulmonary allograft. Compared to cryopreserved allografts, the decellularized group showed similar rates of early mortality (odds ratio, 0.55, 95% confidence interval, 0.21–1.41, P = 0.22). At a mean follow-up period of 5.89 years, no significant difference was observed between the two groups for follow-up allograft dysfunction (hazard ratio, 0.65, 95% confidence interval, 0.20–2.14, P = 0.48). Similarly, no difference was seen in reintervention rates (hazard ratio, 0.54, 95% confidence interval, 0.09–3.12, P = 0.49) nor endocarditis (hazard ratio, 0.30, 95% confidence interval, 0.07–1.35, P = 0.12) at a mean follow-up of 4.85 and 5.75 years, respectively. Conclusions Decellularized and cryopreserved pulmonary allografts are associated with similar postoperative outcomes for RVOT reconstruction during the Ross procedure. Larger propensity-matched and randomized control trials are necessary to elucidate the efficacy of decellularized allografts compared to cryopreserved allografts in the setting of the Ross.

In this paper, we aim to explore the application value of tissue engineering for the construction of artificial cartilage in vitro. Chondrocytes from healthy porcine articular cartilage tissue were seeded on articular cartilage extracellular matrix (ACECM) scaffolds and cultivated. Type II collagen immunofluorescent staining was used to assess secretion from the extracellular matrix. Chondrocytes, which were mainly polygonal and cobblestone-shaped, were inoculated on ACECM-oriented scaffolding for 7 days, and the neo-tissue showed translucent shape and toughness. Using inverted and fluorescence microscopy, we found that chondrocytes on the scaffolds performed well in terms of adhesion and growth, and they secreted collagen type II. Moreover, the porcine ACECM scaffolds had good biocompatibility. The inflammatory cell detection, cellular immune response assay and humoral immune response assay showed porcine ACECM scaffolds were used for xenotransplantation without significant immune inflammatory response. All these findings reveal that ACECM-oriented scaffold is an ideal natural biomaterial for cartilage tissue engineering. [ABSTRACT FROM AUTHOR]

Objective: Indirect Jagged1 immobilization efficiently activates canonical Notch signaling in human dental pulp stem cells (hDPSCs). This study aimed to investigate the characteristics of the Jagged1-treated hDPSC-derived decellularized extracellular matrix (dECM) and its biological activity on odonto/osteogenic differentiation of stem cells isolated from apical papilla (SCAPs).Methods: Bioinformatic database of Jagged1-treated hDPSCs was analyzed using NetworkAnalyst. hDPSCs seeded on the Jagged1 immobilized surface were maintained with normal or osteogenic induction medium (OM) followed by decellularization procedure, dECM-N, or dECM-OM, respectively. SCAPs were reseeded on each dECM with either the normal medium or the OM. Cell viability was determined by MTT assay. Characteristics of dECMs and SCAPs were evaluated by SEM, EDX, immunofluorescent staining, and alcian blue staining. Mineralization was assessed by alizarin red S, Von Kossa, and alkaline phosphatase staining. Statistical significance was considered at p < 0.05.Results: RNA-seq database revealed upregulation of several genes involved in ECM organization, ECM–receptor interaction, and focal adhesion in Jagged1-treated hDPSCs. Immobilized Jagged1 increased the osteogenesis of the hDPSC culture with OM. dECMs showed fibrillar-like network structure and maintained major ECM proteins, fibronectin, type I-collagen, and glycosaminoglycans. A decrease in calcium and phosphate components was observed in dECMs after the decellularized process. Cell viability on dECMs did not alter by 7 days. Cell attachment and f-actin cytoskeletal organization of SCAPs proliferated on Jagged1-treated dECMs were comparable to those of the control dECMs. SCAPs exhibited significantly higher mineralization on dECM-N in OM and markedly enhanced on dECM-OM with normal medium or OM conditions.Conclusion: Jagged1-treated hDPSC-derived dECMs are biocompatible and increase odonto/osteogenic differentiation of SCAPs. The results suggested the potential of Jagged1 dECMs, which could be further developed into ECM scaffolds for application in regenerative medicine.

Background: Distant metastasis is the leading risk factor of death in breast cancer patients, with lung and liver being commonly involved sites of distant seeding. Ongoing clinical trials are studying the benefit from additional local treatment to these metastatic sites with radiation therapy. However, little is known about the tissue-specific microenvironment and the modulating response to treatments due to limitations of traditional in vitro systems. By using biomatrix scaffolds (BMSs) to recreate the complex composition of extracellular matrices in normal organs, we chose to study the radiotherapy response with engineered breast cancer "metastases" in liver and lung organ-specific tissues. Methods: Liver and lung BMSs were prepared for tissue culture. Human breast cancer cell lines were passaged on normal tissue culture plates or tissue culture plates coated with Matrigel, liver BMSs, and lung BMSs. Clonogenic assays were performed to measure cell survival with varying doses of radiation. Reactive Oxygen Species (ROS) detection assay was used to measure ROS levels after 6 Gy irradiation to cancer cells. Results: The response of breast cell lines to varying doses of radiotherapy is affected by their in vitro acellular microenvironment. Breast cancer cells grown in liver BMSs were more radiosensitive than when grown in lung BMSs. ROS levels for breast cancer cells cultured in lung and liver BMSs were higher than that in plastic or in Matrigel plate cells, before and after radiotherapy, highlighting the interaction with surrounding tissue-specific growth factors and cytokines. ROSs in both lung and liver BMSs were significantly increased after radiotherapy delivery, suggesting these sites create prime environments for radiation-induced cell death. Conclusions: The therapeutic response of breast cancer metastases is dependent on the organ-specific microenvironment. The interaction between tissue microenvironment in these organs may identify sensitivity of therapeutic drug targets and radiation delivery for future studies. [ABSTRACT FROM AUTHOR]

Recently, a decellularized microvascular graft (inner diameter: 0.6 mm) modified with the integrin α4β1 ligand, REDV, was developed to provide an alternative to autologous‐vein grafting in reconstructive microsurgery, showing good early‐stage patency under arterial flow in rats. This consecutive study evaluated its potential utility not only as an arterial substitute, but also as a venous substitute, using a rat‐tail replantation model. Graft remodeling depending on hemodynamic status was also investigated. ACI rat tail arteries were decellularized via ultra‐high‐hydrostatic pressure treatment and modified with REDV to induce antithrombogenic interfaces and promote endothelialization after implantation. Grafts were implanted into the tail artery and vein to re‐establish blood circulation in amputated Lewis rat tails (n = 12). The primary endpoint was the survival of replants. Secondary endpoints were graft patency, remodeling, and regeneration for 6 months. In all but three cases with technical errors or postoperative self‐mutilation, tails survived without any evidence of ischemia or congestion. Six‐month Kaplan–Meier patency was 100% for tail‐artery implanted grafts and 62% for tail‐vein implanted grafts. At 6 months, the neo‐tunica media (thickness: 95.0 μm in tail‐artery implanted grafts, 9.3 μm in tail‐vein implanted grafts) was regenerated inside the neo‐intima. In conclusion, the microvascular grafts functioned well both as arterial and venous paths of replanted‐rat tails, with different remodeling under arterial and venous conditions. [ABSTRACT FROM AUTHOR]

BackgroundDistant metastasis is the leading risk factor of death in breast cancer patients, with lung and liver being commonly involved sites of distant seeding. Ongoing clinical trials are studying the benefit from additional local treatment to these metastatic sites with radiation therapy. However, little is known about the tissue-specific microenvironment and the modulating response to treatments due to limitations of traditional in vitro systems. By using biomatrix scaffolds (BMSs) to recreate the complex composition of extracellular matrices in normal organs, we chose to study the radiotherapy response with engineered breast cancer “metastases” in liver and lung organ-specific tissues.MethodsLiver and lung BMSs were prepared for tissue culture. Human breast cancer cell lines were passaged on normal tissue culture plates or tissue culture plates coated with Matrigel, liver BMSs, and lung BMSs. Clonogenic assays were performed to measure cell survival with varying doses of radiation. Reactive Oxygen Species (ROS) detection assay was used to measure ROS levels after 6 Gy irradiation to cancer cells.ResultsThe response of breast cell lines to varying doses of radiotherapy is affected by their in vitro acellular microenvironment. Breast cancer cells grown in liver BMSs were more radiosensitive than when grown in lung BMSs. ROS levels for breast cancer cells cultured in lung and liver BMSs were higher than that in plastic or in Matrigel plate cells, before and after radiotherapy, highlighting the interaction with surrounding tissue-specific growth factors and cytokines. ROSs in both lung and liver BMSs were significantly increased after radiotherapy delivery, suggesting these sites create prime environments for radiation-induced cell death.ConclusionsThe therapeutic response of breast cancer metastases is dependent on the organ-specific microenvironment. The interaction between tissue microenvironment in these organs may identify sensitivity of therapeutic drug targets and radiation delivery for future studies.

Xenogeneic scaffolds derived from the decellularized pancreas are plausible biomedical materials for pancreatic tissue engineering applications. During the decellularized process, the ultrastructure of extracellular matrices, including collagen fibers, was destructed, which leads to the decrease of mechanical strength and the immune-inflammatory response after transplantation in vivo. The cross-linking method plays an important role in increasing mechanical strength and reducing the inflammatory potential of decellularized scaffolds. However, no ideal cross-linking agent has been identified for decellularized pancreatic scaffolds yet. In this study, a cyclic perfusion system was used to cross-link decellularized pancreatic scaffolds from Sprague Dawley rat with silver nanoparticles (AgNPs). The optimum concentration of AgNPs was selected according to the scanning electron microscope observation and mechanical evaluation, as well as cytotoxicity to human umbilical vein endothelial cells and MIN-6 cell lines in vitro. The inflammation after transplantation in vivo was evaluated by hematoxylin and eosin staining; M1/M2 polarization phenotype of macrophages was further evaluated. Our results showed that after cross-linking, the scaffold possessed better mechanical property and biocompatibility, with the polarization of M2 macrophages increased. Thus, AgNP-cross-linked pancreatic acellular scaffold can provide an ideal scaffold source for pancreatic tissue engineering. [ABSTRACT FROM AUTHOR]

Stem cells transplantation is the main method of tissue engineering regeneration treatment, the viability and therapeutic efficiency are limited. Scaffold materials also play an important role in tissue engineering, whereas there are still many limitations, such as rejection and toxic side effects caused by scaffold materials. Cell sheet engineering is a scaffold-free tissue technology, which avoids the side effects of traditional scaffolds and maximizes the function of stem cells. It is increasingly being used in the field of tissue regenerative medicine. Dental-derived mesenchymal stem cells (DMSCs) are multipotent cells that exist in various dental tissues and can be used in stem cell-based therapy, which is impactful in regenerative medicine. Emerging evidences show that cell sheets derived from DMSCs have better effects in the field of regenerative medicine applications. Extracellular matrix (ECM) is the main component of cell sheets, which is a dynamic repository of signalling biological molecules and has a variety of biological functions and may play an important role in the application of cell sheets. In this review, we summarized the application status, mechanisms that sheets and ECM may play and future prospect of DMSC sheets on regeneration medicine. [ABSTRACT FROM AUTHOR]

Background: The ideal conduit for repair of the right ventricular outflow tract (RVOT) during the Ross procedure remains unclear and has yet to be fully elucidated. We perform a pairwise meta-analysis to compare the short-term and long-term outcomes of decellularized versus cryopreserved pulmonary allografts for RVOT reconstruction during the Ross procedure. Main body: After a comprehensive literature search, studies comparing decellularized and cryopreserved allografts for patients undergoing RVOT reconstruction during the Ross procedure were pooled to perform a pairwise meta-analysis using the random-effects model. Primary outcomes were early mortality and follow-up allograft dysfunction. Secondary outcomes were reintervention rates and follow-up endocarditis. A total of 4 studies including 1687 patients undergoing RVOT reconstruction during the Ross procedure were included. A total of 812 patients received a decellularized pulmonary allograft, while 875 received a cryopreserved pulmonary allograft. Compared to cryopreserved allografts, the decellularized group showed similar rates of early mortality (odds ratio, 0.55, 95% confidence interval, 0.21–1.41, P = 0.22). At a mean follow-up period of 5.89 years, no significant difference was observed between the two groups for follow-up allograft dysfunction (hazard ratio, 0.65, 95% confidence interval, 0.20–2.14, P = 0.48). Similarly, no difference was seen in reintervention rates (hazard ratio, 0.54, 95% confidence interval, 0.09–3.12, P = 0.49) nor endocarditis (hazard ratio, 0.30, 95% confidence interval, 0.07–1.35, P = 0.12) at a mean follow-up of 4.85 and 5.75 years, respectively. Conclusions: Decellularized and cryopreserved pulmonary allografts are associated with similar postoperative outcomes for RVOT reconstruction during the Ross procedure. Larger propensity-matched and randomized control trials are necessary to elucidate the efficacy of decellularized allografts compared to cryopreserved allografts in the setting of the Ross. [ABSTRACT FROM AUTHOR]

In recent years, it has become common to experiment with ex vivo perfused lungs for organ transplantation and to attempt regenerative pulmonary engineering using decellularized lung matrices. However, our understanding of the physiology of ex vivo organ perfusion is imperfect; it is not currently well understood how decreasing microvascular barrier affects the perfusion of pulmonary parenchyma. In addition, protocols for lung perfusion and organ culture fluid-handling are far from standardized, with widespread variation on both basic methods and on ideally controlled parameters. To address both of these deficits, a robust, noninvasive, and mechanistic model is needed which is able to predict microvascular resistance and permeability in perfused lungs while providing insight into capillary recruitment. Although validated mathematical models exist for fluid flow in native pulmonary tissue, previous models generally assume minimal intravascular leak from artery to vein and do not assess capillary bed recruitment. Such models are difficult to apply to both ex vivo lung perfusions, in which edema can develop over time and microvessels can become blocked, and to decellularized ex vivo organomimetic cultures, in which microvascular recruitment is variable and arterially perfused fluid enters into the alveolar space. Here, we develop a mathematical model of pulmonary microvascular fluid flow which is applicable in both instances, and we apply our model to data from native, decellularized, and regenerating lungs under ex vivo perfusion. The results provide substantial insight into microvascular pressure-flow mechanics, while producing previously unknown output values for tissue-specific capillary-alveolar hydraulic conductivity, microvascular recruitment, and total organ barrier resistance. NEW & NOTEWORTHY We present a validated model of pulmonary microvascular fluid mechanics and apply this model to study the effects of increased capillary permeability in decellularized and regenerating lungs. We find that decellularization alters microvascular steady-state mechanics and that re-endothelialization partially rescues key biologic parameters. The described model provides powerful insight into intraorgan microvascular dynamics and may be used to guide regenerative engineering experiments. We include all data and derivations necessary to replicate this work. [ABSTRACT FROM AUTHOR]

An imbalance exists between the supply of organs for transplantation and the number of patients in the donor transplant waiting lists. Current use of autologous, synthetic, and animal-derived grafts for tissue replacement is limited by the low availability, poor biocompatibility, and high cost. Decellularized plant scaffolds with remarkable physical similarities to human organs have recently emerged and have been found to present favorable characteristics that make them suitable as an alternative biomaterial, such as a superficial surface area, excellent water transport and retention, pre-existing vascular networks, interconnected porosity, and a wide range of mechanical properties. In addition to their unique and superior biocompatibility, plant-derived scaffolds present the advantages of low production cost, no ethical or supply constraints, simple operation and suitability for large-scale production and research. However, there are still some problems and deficiencies in this field, such as immature decellularization standards and methods, insufficient research on the biocompatibility of plant extracellular matrix. At present, research on decellularized plant extracellular matrix is still in its infancy, and its applicability to tissue engineering needs to be further improved. In this review, the current research progress on decellularized plant scaffolds is reviewed, the problems to be solved and future research directions are discussed.

The use of autologous nerve grafts remains the gold standard for treating nerve defects, but current nerve repair techniques are limited by donor tissue availability and morbidity associated with tissue loss. Recently, the use of conduits in nerve injury repair, made possible by tissue engineering, has shown therapeutic potential. We manufactured a biodegradable, collagen-based nerve conduit containing decellularized sciatic nerve matrix and compared this with a silicone conduit for peripheral nerve regeneration using a rat model. The collagen-based conduit contains nerve growth factor, brain-derived neurotrophic factor, and laminin, as demonstrated by enzyme-linked immunosorbent assay. Scanning electron microscopy images showed that the collagen-based conduit had an outer wall to prevent scar tissue infiltration and a porous inner structure to allow axonal growth. Rats that were implanted with the collagen-based conduit to bridge a sciatic nerve defect experienced significantly improved motor and sensory nerve functions and greatly enhanced nerve regeneration compared with rats in the sham control group and the silicone conduit group. Our results suggest that the biodegradable collagen-based nerve conduit is more effective for peripheral nerve regeneration than the silicone conduit.

Upper limb muscle reconstruction is required following cancer resection, trauma, and congenital deformities. Current surgical reconstruction of the muscle involves local, regional and free flaps. However, muscle reconstruction is not always possible due to the size of the defect and functional donor site morbidity. These challenges could be addressed with the production of scaffolds composed of an extracellular matrix (ECM) derived from decellularized human skeletal muscle. This study aimed to find an optimal technique to decellularize a flexor digitorum superficialis muscle. The first two protocols were based on a detergent only (DOT) and a detergent‐enzymatic protocol (DET). The third protocol avoided the use of detergents and proteolytic enzymes (NDNET). The decellularized scaffolds were characterized using qualitative techniques including histological and immunofluorescent staining and quantitative techniques assessing deoxyribonucleic acid (DNA), glycosaminoglycan (GAG), and collagen content. The DOT protocol consisting of 2% SDS for 4 hours was successful at decellularizing human FDS, as shown by DNA content assay and nuclei immunofluorescence staining. The DOT protocol maintained the microstructure of the scaffolds as shown by Masson's trichrome staining and collagen and GAG content. DET and NDNET protocols maintained the ECM, but were unsuccessful in removing all DNA content after two cycles of decellularization. Decellularization of skeletal muscle is a viable option for muscle reconstruction using a detergent only technique for upper limb defects. Further testing in vivo will assess the effectiveness of decellularized scaffolds for upper limb muscle skeletal tissue engineering. [ABSTRACT FROM AUTHOR]

Abstract Background Prosthetic arteriovenous grafts (AVG) continue to have a high rate of failure in clinical use, yet there is continued clinical demand for them. However, there is no small animal model of AVG to test novel tissue-engineered vascular grafts. We established a new rat arteriovenous graft model to compare the healing of decellularized carotid artery (CA) to autologous CA. Materials and methods The infrarenal vena cava and aorta of Wistar rats were exposed and dissected free below renal artery. A longitudinal 1 mm venotomy and arteriotomy were made on the anterior walls. The conduit was either autologous CA or heterologous decellularized CA; a conduit was sewn to the inferior vena cava and aorta in end-to-side fashion. Rats were sacrificed on postoperative day 21 for examination. Results All rats survived without heart failure. Conduits had 100% patency rate (day 21) in both the control and decellularized CA groups (n = 6). Both control and decellularized CA showed similar rates of reendothelialization, inflammatory cell infiltration, and cell turnover. The outflow vein beyond the autologous or decellularized conduits showed similar neointimal thickness and cell turnover. Conclusions Decellularized CA may be a viable tissue engineering graft for use as an arteriovenous graft for dialysis access. The rat aorta-vena cava graft is a useful model to test new materials including tissue-engineered grafts for use as AVG. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Three-dimensional (3D) printing of decellularized extracellular matrix (dECM) hydrogels is a promising technique for regenerative engineering. 3D-printing enables the reproducible and precise patterning of multiple cells and biomaterials in 3D, while dECM has high organ-specific bioactivity. However, dECM hydrogels often display poor printability on their own and necessitate additives or support materials to enable true 3D structures. In this study, we used a sacrificial material, 3D-printed Pluronic F-127, to serve as a platform into which dECM hydrogel can be incorporated to create specifically designed structures made entirely up of dECM. The effects of 3D dECM are studied in the context of engineering the intrahepatic biliary tree, an often-understudied topic in liver tissue engineering. Encapsulating biliary epithelial cells (cholangiocytes) within liver dECM has been shown to lead to the formation of complex biliary trees in vitro. By varying several aspects of the dECM structures' geometry, such as width and angle, we show that we can guide the directional formation of biliary trees. This is confirmed by computational 3D image analysis of duct alignment. This system also enables fabrication of a true multi-layer dECM structure and the formation of 3D biliary trees into which other cell types can be seeded. For example, we show that hepatocyte spheroids can be easily incorporated within this system, and that the seeding sequence influences the resulting structures after seven days in culture. Statement of Significance The field of liver tissue engineering has progressed significantly within the past several years, however engineering the intrahepatic biliary tree has remained a significant challenge. In this study, we utilize the inherent bioactivity of decellularized extracellular matrix (dECM) hydrogels and 3D-printing of a sacrificial biomaterial to create spatially defined, 3D biliary trees. The creation of patterned, 3D dECM hydrogels in the past has only been possible with additives to the gel that may stifle its bioactivity, or with rigid and permanent support structures that may present issues upon implantation. Additionally, the biological effect of 3D spatially patterned liver dECM has not been demonstrated independent of the effects of dECM bioactivity alone. This study demonstrates that sacrificial materials can be used to create pure, multi-layer dECM structures, and that strut width and angle can be changed to influence the formation and alignment of biliary trees encapsulated within. Furthermore, this strategy allows co-culture of other cells such as hepatocytes. We demonstrate that not only does this system show promise for tissue engineering the intrahepatic biliary tree, but it also aids in the study of duct formation and cell-cell interactions. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogels, highly‐hydrated crosslinked polymer networks, closely mimic the microenvironment of native extracellular matrix (ECM) and thus present as ideal platforms for three‐dimensional cell culture. Hydrogels derived from tissue‐ and organ‐specific decellularized ECM (dECM) may retain bioactive signaling cues from the native tissue or organ that could in turn modulate cell–material interactions and response. In this study, we demonstrate that porcine kidney dECM can be processed to form hydrogels suitable for cell culture and encapsulation studies. Scanning electron micrographs of hydrogels demonstrated a fibrous ultrastructure with interconnected pores, and rheological analysis revealed rapid gelation times with shear moduli dependent upon the protein concentration of the hydrogels. Conditionally‐immortalized human glomerular endothelial cells (GEnCs) cultured on top of or encapsulated within hydrogels exhibited high cell viability and proliferation over a one‐week culture period. However, gene expression analysis of GEnCs encapsulated within kidney dECM hydrogels revealed significantly lower expression of several relevant genes of interest compared to those encapsulated within hydrogels composed of only purified collagen I. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A:2448–2462, 2018. [ABSTRACT FROM AUTHOR]

Decellularized biologic scaffolds are gaining popularity over synthetic biomaterials as naturally derived materials capable of promoting improved healing. Nevertheless, the most widely used biologic material – acellular dermal matrix (ADM) – exhibits slow repopulation and remodeling, which prevents integration. Additionally, engineering control of these materials is limited because they require a natural source for their production. In the current report, we demonstrate the feasibility of using genetically engineered animals to create decellularized biologic scaffolds with favorable extracellular matrix (ECM) properties. Specifically, we utilized skin from thrombospondin (TSP)-2 KO mice to derive various decellularized products. Scanning electron microscopy and mechanical testing showed that TSP-2 KO ADM exhibited an altered structure and a reduction in elastic modulus and ultimate tensile strength, respectively. When a powdered form of KO ADM was implanted subcutaneously, it was able to promote enhanced vascularization over WT. Additionally, when implanted subcutaneously, intact slabs of KO ADM were populated by higher number of host cells when compared to WT. In vitro studies confirmed the promigratory properties of KO ADM. Specifically, degradation products released by pepsin digestion of KO ADM induced greater cell migration than WT. Moreover, cell-derived ECM from TSP-2 null fibroblasts was more permissive to fibroblast migration. Finally, ADMs were implanted in a diabetic wound model to examine their ability to accelerate wound healing. KO ADM exhibited enhanced remodeling and vascular maturation, indicative of efficient integration. Overall, we demonstrate that genetic manipulation enables engineered ECM-based materials with increased regenerative potential. [ABSTRACT FROM AUTHOR]

Muscle injury and defect affect people's quality of life, and effective treatment is lacking. Herein, we generated a scaffold to obtain decellularized porcine Achilles tendon myotendinous junction (D-MTJ) extracellular matrix (ECM) with well-preserved native biphasic hierarchical structure, biological composition, and excellent mechanical properties for muscle regeneration. The combined use of potassium chloride, potassium iodide, Triton-X 100, and sodium-dodecyl sulfate (SDS) can completely remove the main immunogenicity, while maintaining the major biological components and microstructure. The specific biomechanics of D-MTJ is comparable to the native muscle-tendon physiological conditions. Additionally, the D-MTJ ECM scaffold induced minimal immunological reaction (histology analysis) through rat subcutaneous implantation. Moreover, in vitro , muscle satellite cells adhered, proliferated, and infiltrated into the D-MTJ scaffold, and myofiber-like cell differentiation was observed as shown by increased expression of myogenesis-related genes during culture. In vivo, newly formed myofibers were observed in a muscle defect model with D-MTJ orthotopic transplantation, while the control group presented mostly with fibrous tissue deposition. Additionally, the number of Myod and MyHC-positive cells in the ECM scaffold group was higher at day 30. We preliminary explored the mechanisms underlying D-MTJ-mediated muscle regeneration, which may be attributed to its specific biphasic hierarchical structure, bio-components, and attractiveness for myogenesis cells. In conclusion, our findings suggest the D-MTJ ECM scaffold prepared in this study is a promising choice for muscle regeneration. Statement of Significance This study is the first to use decellularization technology obtaining the specifically decellularized myotendinous junction (D-MTJ) with well-preserved biphasic hierarchical structure and constituents, excellent mechanical properties and good biocompatibility. The D-MTJ was further proved to be efficient for muscle regeneration in vitro and in vivo , and the underlying mechanisms may be attributed to its specifically structure and constituents, improved myogenesis and good preservation of repair-related factors. Our study may provide basis for the decellularization of other biphasic hierarchical tissues and a platform for further studies on muscle fiber and tendon integrations in vitro . [ABSTRACT FROM AUTHOR]

Contrary to conventional research animals, horses naturally develop asthma, a disease in which the extracellular matrix of the lung plays a significant role. Hence, the horse lung extracellular matrix appears to be an ideal candidate model for in vitro studying the mechanisms and potential treatments for asthma. However, so far, such model to study cell– extracellular matrix interactions in asthma has not been developed. The aim of this study was to establish a protocol for equine lung decellularization that maintains the architecture of the extracellular matrix and could be used in the future as an in vitro model for therapeutic treatment in asthma. For this the equine lungs were decellularized by sodium dodecyl sulfate detergent perfusion at constant gravitational pressure of 30 cmH2O. Lung scaffolds were assessed by immunohistochemistry (collagen I, III, IV, laminin, and fibronectin), scanning electron microscopy, and DNA quantification. Their mechanical property was assessed by measuring lung compliance using the super-syringe technique. The optimized protocol of lung equine decellularization was effective to remove cells (19.8 ng/mg) and to preserve collagen I, III, IV, laminin, and fibronectin. Moreover, scanning electron microscopy analysis demonstrated maintained microscopic lung structures. The decellularized lungs presented lower compliance compared to native lung. In conclusion we described a reproducible decellularization protocol that can produce an acellular equine lung feasible for the future development of novel treatment strategies in asthma. [ABSTRACT FROM AUTHOR]

Tissue extracellular matrix (ECM) is a complex material made up of fibrous proteins and ground substance (glycosaminoglycans, GAGs) that are secreted by cells. ECM contains important biological cues that modulate cell behaviors, and it also serves as a structural scaffold to which cells can adhere. 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. In this study, a decellularized ECM-based composite hydrogel was formulated by using modified GAGs that covalently bind tissue particles. These GAG-ECM composite hydrogels combine the advantages of solid decellularized ECM scaffolds and pepsin-digested ECM hydrogels by facilitating ECM hydrogel formation without a disruptive enzymatic digestion process. Additionally, engineered hydrogels can contain more than one type of ECM (from bone, fat, liver, lung, spleen, cartilage, or brain), at various concentrations. These hydrogels demonstrated tunable gelation kinetics and mechanical properties, offering the possibility of numerous in vivo and in vitro applications with different property requirements. Retained bioactivity of ECM particles crosslinked into this hydrogel platform was confirmed by the variable response of stem cells to different types of ECM particles with respect to osteogenic differentiation in vitro, and bone regeneration in vivo. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 147-159, 2018. [ABSTRACT FROM AUTHOR]

There is a clinical need to provide replacement tracheal tissue for the pediatric population affected by congenital defects, as current surgical solutions are not universally applicable. A potential solution is to use tissue engineered scaffold as the framework for regenerating autologous tissue. Rabbit trachea were used and different detergents (Triton x-100 and sodium deoxycholate) and enzymes (DNAse/RNAse) investigated to create a decellularization protocol. Each reagent was initially tested individually and the outcome used to design a combined protocol. At each stage the resultant scaffold was assessed histologically, molecularly for acellularity and matrix preservation. Immunogenicity of the final scaffold was assessed by implantation into a rat model for 4 weeks. Both enzymes and detergents were required to produce a completely acellular (DNA content 42.78 ng/mg) scaffold with preserved collagen and elastin however, GAG content were reduced (8.78 ± 1.35 vs. 5.5 ± 4.8). Following in vivo implantation the scaffold elicited minimal immune response and showed significant cellular infiltration and vasculogenesis. The luminal aspect of the implanted scaffold showed infiltration of host derived cells, which were positive for pan cytokeratin. It is possible to create biologically derived biocompatible scaffolds to address specific pediatric clinical problems. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2126-2135, 2017. [ABSTRACT FROM AUTHOR]

Introduction Xenogeneic extracellular matrix (ECM) hydrogels have shown promise in remediating cardiac ischemia damage in animal models, yet analogous human ECM hydrogels have not been well development. An original human placenta-derived hydrogel (hpECM) preparation was thus generated for assessment in cardiomyocyte cell culture and therapeutic cardiac injection applications. Methods and results Hybrid orbitrap-quadrupole mass spectrometry and ELISAs showed hpECM to be rich in collagens, basement membrane proteins, and regenerative growth factors (e.g. VEGF-B, HGF). Human induced pluripotent stem cell (iPSC)-derived cardiomyocytes synchronized and electrically coupled on hpECM faster than on conventional cell culture environments, as validated by intracellular calcium measurements. In vivo , injections using biotin-labeled hpECM confirmed its spatially discrete localization to the myocardium proximal to the injection site. hpECM was injected into rat myocardium following an acute myocardium infarction induced by left anterior descending artery ligation. Compared to sham treated animals, which exhibited aberrant electrical activity and larger myocardial scars, hpECM injected rat hearts showed a significant reduction in scar volume along with normal electrical activity of the surviving tissue, as determined by optical mapping. Conclusion Placental matrix and growth factors can be extracted as a hydrogel that effectively supports cardiomyocytes in vitro , and in vivo reduces scar formation while maintaining electrophysiological activity when injected into ischemic myocardium. Statement of Significance This is the first report of an original extracellular matrix hydrogel preparation isolated from human placentas (hpECM). hpECM is rich in collagens, laminin, fibronectin, glycoproteins, and growth factors, including known pro-regenerative, pro-angiogenic, anti-scarring, anti-inflammatory, and stem cell-recruiting factors. hpECM supports the culture of cardiomyocytes, stem cells and blood vessels assembly from endothelial cells. In a rat model of myocardial infarction, hpECM injections were safely deliverable to the ischemic myocardium. hpECM injections repaired the myocardium, resulting in a significant reduction in infarct size, more viable myocardium, and a normal electrophysiological contraction profile. hpECM thus has potential in therapeutic cardiovascular applications, in cellular therapies (as a delivery vehicle), and is a promising biomaterial for advancing basic cell-based research and regenerative medicine applications. [ABSTRACT FROM AUTHOR]

Porcine small intestine sub-mucosa (SIS) and cornea were decellularized using ionic biological detergent (1% SDS) and stored at –20°C in sterile phosphate buffer saline (PBS) solution containing mixture of antibiotics. The prepared biomaterials were subjected to histological and scanning electron microscopic observations to ascertain the decellularization status before their clinical application. Both the biomaterials were evaluated for the repair of corneal defects in 11 animals. Five animals having corneal defects repaired with SIS and 4 repaired with cornea demonstrated successful healing without clinical signs of infections or reoccurrence during the 8 months follow up period. Results of study support the use of decellularized porcine SIS and cornea as an alternative to traditional implantation materials to treat different corneal defects in animals.

Background: Bone grafts are used in approximately one half of all musculoskeletal surgeries. Autograft bone is the historic gold standard but is limited in supply and its harvest imparts significant morbidity to the patient. Alternative sources of bone graft include allografts, synthetics and, less commonly, xenografts which are taken from animal species. Xenografts are available in unlimited supply from healthy animal donors with controlled biology, avoiding the risk of human disease transmission, and may satisfy current demand for bone graft products. Methods: In the current study, cancellous bone was harvested from porcine femurs and subjected to a novel decellularization protocol to derive a bone scaffold. Results: The scaffold was devoid of donor cellular material on histology and DNA sampling (p < 0.01). Microarchitectural properties important for osteoconductive potential were preserved after decellularization as shown by high resolution imaging modalities. Proteomics data demonstrated similar profiles when comparing the porcine bone scaffold against commercially available human demineralized bone matrix approved for clinical use. Conclusion: We are unaware of any porcine-derived bone graft products currently used in orthopaedic surgery practice. Results from the current study suggest that porcine-derived bone scaffolds warrant further consideration to serve as a potential bone graft substitute.

Biomaterials based on natural materials including decellularized tissues and tissue-derived hydrogels are becoming more widely used for clinical applications. Because of their native composition and structure, these biomaterials induce a distinct form of the foreign body response that differs from that of non-native biomaterials. Differences include direct interactions with cells via preserved moieties as well as the ability to undergo remodeling. Moreover, these biomaterials could elicit adaptive immune responses due to the presence of modified native molecules. Therefore, these biomaterials present unique challenges in terms of understanding the progression of the foreign body response. This review covers this response to natural materials including natural polymers, decellularized tissues, cell-derived matrix, tissue derived hydrogels, and biohybrid materials. With the expansion of the fields of regenerative medicine and tissue engineering, the current repertoire of biomaterials has also expanded and requires continuous investigation of the responses they elicit. [ABSTRACT FROM AUTHOR]

As the endoscopic technique is widely used in the diagnosis and treatment of diseases, the incidence of ureteral injuries increases annually. The classical surgical therapies are not always satisfactory. With the constant development of the tissue engineering technology in the field of urinary reconstruction, the ureteral reconstruction has become possible technology. In this study, a novel perfusion-decellularized protocol, which combined a perfusion system with the commonly used physical and chemical methods, was used to prepare the decellularized ureters for ureteral reconstruction and the urinary tract-derived cells (UDCs) were seeded on the surface of the perfusion-decellularized ureters (PDUs) in order to observe the cells survival, adhesion, proliferation and distribution. The data of H&E staining, DAPI staining, and the agarose gel electrophoresis demonstrated that the cellular components of PDUs were removed, and the decellularized time was shorter than previous study. In addition, compared with the native ureters, the DNA content of the PDUs was significantly decreased just two percent residue ( P < 0.05). Scanning electron microscopy, collagen and glycosaminoglycan content assay showed that the three-dimensional (3D) ultrastructure and the compositions of the extracellular matrix (ECM) of PDUs were well preserved. When the UDCs were seeded onto the PDUs, the UDCs formed multilayer structure on the surface of the PDUs, infiltrated into the deep layer of the decellularized ureters and then formed laminated structure. In conclusion, the decellularized ureters prepared by the novel perfusion-decellularized method may be the potential surrogate for ureteral tissue-engineered repair. [ABSTRACT FROM AUTHOR]

Porcine small intestine sub-mucosa (SIS) and cornea were decellularized using ionic biological detergent (1% SDS) and stored at -20°C in sterile phosphate buffer saline (PBS) solution containing mixture of antibiotics. The prepared biomaterials were subjected to histological and scanning electron microscopic observations to ascertain the deceTularization status before their clinical application. Both the biomaterials were evaluated for the repair of corneal defects in 11 animals. Five animals having corneal defects repaired with SIS and 4 repaired with cornea demonstrated successful healing without clinical signs of infections or reoccurrence during the 8 months follow up period. Results of study support the use of decellularized porcine SIS and cornea as an alternative to traditional implantation materials to treat different corneal defects in animals. [ABSTRACT FROM AUTHOR]

Decellularized tissues have been used to investigate the extracellular matrix (ECM) in a number of different tissues and species. Santi and Johnson JARO 14:3-15 (2013) first described the decellularized inner ear in the mouse, rat, and human using scanning thin-sheet laser imaging microscopy (sTSLIM). The purpose of the present investigation is to examine decellularized cochleas in the mouse and human at higher resolution using scanning electron microscopy (SEM). Fresh cochleas were harvested and decellularized using detergent extraction methods. Following decellularization, the ECM of the bone, basilar membrane, spiral limbus, and ligament remained, and all of the cells were removed from the cochlea. A number of similarities and differences in the ECM of the mouse and human were observed. A novel, spirally directed structure was present on the basilar membrane and is located at the border between Hensen and Boettcher cells. These septa-like structures formed a single row in the mouse and multiple rows in the human. The basal lamina of the stria vascularis capillaries was present and appeared thicker in the human compared with the mouse. In the mouse, numerous openings beneath the spiral prominence that previously housed the root processes of the external sulcus cells were observed but in the human there was only a single row of openings. These and other anatomical differences in the ECM between the mouse and human may reflect functional differences and/or be due to aging; however, decellularized cochleas provide a new way to examine the cochlear ECM and reveal new observations. [ABSTRACT FROM AUTHOR]

Extracellular matrix (ECM) collectively represents a class of naturally derived proteinaceous biomaterials purified from harvested organs and tissues with increasing scientific focus and utility in tissue engineering and repair. This interest stems predominantly from the largely unproven concept that processed ECM biomaterials as natural tissue-derived matrices better integrate with host tissue than purely synthetic biomaterials. Nearly every tissue type has been decellularized and processed for re-use as tissue-derived ECM protein implants and scaffolds. To date, however, little consensus exists for defining ECM compositions or sources that best constitute decellularized biomaterials that might better heal, integrate with host tissues and avoid the foreign body response (FBR). Metrics used to assess ECM performance in biomaterial implants are arbitrary and contextually specific by convention. Few comparisons for in vivo host responses to ECM implants from different sources are published. This review discusses current ECM-derived biomaterials characterization methods including relationships between ECM material compositions from different sources, properties and host tissue response as implants. Relevant preclinical in vivo models are compared along with their associated advantages and limitations, and the current state of various metrics used to define material integration and biocompatibility are discussed. Commonly applied applications of these ECM-derived biomaterials as stand-alone implanted matrices and devices are compared with respect to host tissue responses. [ABSTRACT FROM AUTHOR]

Since the meniscus has limited capacity to self-repair, creating a long-lasting meniscus replacement may help reduce the incidence of osteoarthritis (OA) after meniscus damage. As a first step toward this goal, this study evalua ted the mechanical integrity of a decellularized, laser drilled (LD) meniscus as a potential scaffold for meniscal engineering. To evaluate the decellularization process, 24 porcine menisci were processed such that one half remained native tissue, while the other half was decellularized in sodium dodecyl sulphate (SDS). To evaluate the laser drilling process, 24 additional menisci were decellularized, with one half remaining intact while the other half was LD. Decellularization did not affect the tensile properties, hut had significant effects on the cyclic compressive hysteresis and unconfined compressive stress relaxation. Laser drilling decreased the Young's modulus and instantaneous stress during unconfined stress relaxation and the circumferential ultimate strength during tensile testing. However, the losses in mechanical integrity in the LD menisci were generally smaller than the variance observed between samples, and thus, the material properties for the LD tissue remained within a physiological range. In the future, optimization of laser drilling patterns may improve these material properties. Moreover, reseeding the construct with cells may further improve the mechanical properties prior to implantation. As such, this work serves as a proof of concept for generating decellularized, LD menisci scaffolds for the purposes of meniscal engineering. [ABSTRACT FROM AUTHOR]

The performance of implantable biomaterials derived from decellularized tissue, including encouraging results with skeletal muscle, suggests that the extracellular matrix (ECM) derived from native tissue has promising regenerative potential. Yet, the supply of biomaterials derived from donated tissue will always be limited, which is why the in-vitro fabrication of ECM biomaterials that mimic the properties of tissue is an attractive alternative. Towards this end, our group has utilized a novel method to collect the ECM that skeletal muscle myoblasts secrete and form it into implantable scaffolds. The cell derived ECM contained several matrix constituents, including collagen and fibronectin that were also identified within skeletal muscle samples. The ECM was organized into a porous network that could be formed with the elongated and aligned architecture observed within muscle samples. The ECM material supported the attachment and in-vitro proliferation of cells, suggesting effectiveness for cell transplantation, and was well tolerated by the host when examined in-vivo . The results suggest that the ECM collection approach can be used to produce biomaterials with compositions and structures that are similar to muscle samples, and while the physical properties may not yet match muscle values, the in-vitro and in-vivo results indicate it may be a suitable first generation alternative to tissue derived biomaterials. [ABSTRACT FROM AUTHOR]

Mesenchymal bone marrow stromal cells may be a source of cells to preseed decellularized biologic mesh materials for improved cellularization and promote a more physiologic tissue after remodeling. Spontaneous differentiation of mesenchymal stromal cells on the decellularized material would be undesirable. Conversely, induced differentiation of mesenchymal stem cells (MSC) on the material would suggest that these materials may have promise as scaffold materials for bone, cartilage, or adipocyte formation. Two sources of mesenchymal cells were evaluated for induced differentiation in control wells. These MSCs were also evaluated for spontaneous or induced differentiation on decellularized porcine dermis and mesothelium materials. Primarily harvested bone marrow MSCs and commercially obtained MSCs were induced into osteoblasts and adipocytes on decellularized dermis and mesothelium materials. The MSCs were able to be induced into chondrocytes in pellet form but not when grown as a monolayer on the materials. The MSCs did not undergo spontaneous differentiation when grown on the materials for up to four weeks. MSC grown on decellularized porcine dermis or mesothelium do not spontaneously differentiate and may serve as a source of autologous cells for preseeding these extracellular matrix materials prior to implantation. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 2875-2883, 2014. [ABSTRACT FROM AUTHOR]

Objectives/Hypothesis: One potential treatment for vocal fold injury or neoplasia is to replace the entire vocal fold with a tissue-engineered scaffold. This scaffold should ideally have similar mechanical properties and extracellular matrix composition as the native vocal fold. As one approach toward this goal, we decellularized human vocal folds and characterized their mechanical properties and extracellular matrix microstructure. Study Design: Basic science investigation. Methods: Human vocal folds were dissected from the laryngeal framework and treated with sodium dodecyl sulfate (SDS) to remove all cells. Mechanical properties were measured by indentation before and after SDS treatment. The extracellular matrix components of collagen, laminin, elastin, and hyaluronic acid were also characterized before and after decellularization using histology and immunofluorescence. Results: After 4 days of SDS treatment, we obtained a scaffold that retained the original geometry of the vocal fold but was devoid of cells. The elastic modulus of the vocal folds did not change significantly before and after decellularization. Upon qualitative inspection, the decellularized vocal folds retained the original collagen, elastin, and laminin content and orientation but lost the original hyaluronic acid. Conclusions: Vocal folds can be decellularized using SDS without adversely affecting its mechanical stiffness and fibrous extracellular matrix. This preliminary study demonstrates the potential of a decellularized scaffold to serve as a tissueengineered construct for vocal fold replacement. [ABSTRACT FROM AUTHOR]

Decellularization, a technique used in liver regenerative medicine, is the removal of all the cellular components from a tissue or organ, leaving behind an intact structure of extracellular matrix. The biomechanical properties of this novel scaffold material are currently unknown and are important due to the mechanosensitivity of liver cells. Characterizing this material is important for bioengineering liver tissue from this decellularized scaffold as well as creating new 3-dimensional mimetic structures of liver extracellular matrix. This study set out to characterize the biomechanical properties of perfused liver tissue in its native and decellularized states on both a macro- and nano-scale. Poroviscoelastic finite element models were then used to extract the fluid and solid mechanical properties from the experimental data. Tissue-level spherical indentation-relaxation tests were performed on 5 native livers and 8 decellularized livers at two indentation rates and at multiple perfusion rates. Cellular-level spherical nanoindentation was performed on 2 native livers and 1 decellularized liver. Tissue-level results found native liver tissue to possess a long-term Young's modulus of 10.5 kPa and decellularized tissue a modulus of 1.18 kPa. Cellular-level testing found native tissue to have a long-term Young's modulus of 4.40 kPa and decellularized tissue to have a modulus of 0.91 kPa. These results are important for regenerative medicine and tissue engineering where cellular response is dependent on the mechanical properties of the engineered scaffold. [ABSTRACT FROM AUTHOR]

Background: The success of a tissue engineered construct is greatly influenced by the choice of scaffold material. Decellularized esophageal matrix is a promising material for esophageal tissue engineering. The aim of this study was to develop a decellularized ovine esophageal mucosa and to investigate the effect of decellularization on the appearance of the resulting tissue. Methods: Ovine esophagi were decellularized by combination of agitation, enzymatic digestion and treatment with 1 and 5% sodium dodecyl sulphate (SDS). Efficiency of decellularization was assessed by histological examination and DNA quantification. Finally, the effect of decellularization on tissue morphology was investigated by scanning electron microscopy. Results: Decellularization resulted in a highly efficient removal of cells and DNA content. Electron microscopic investigation revealed a denuded, rough, undulating surface with preserved papillary structures. Individual papillae had a length of approximately 55 μm and were present at a density of 1332 μm/mm^{2}. Closer examination revealed a tightly packed sponge-like appearance with pores in the region of 300 nm. Numerous, intact collagen fibres were also visible. Conclusion: Ovine esophagus can be successfully decellularized through treatment with SDS. The resulting decellularized mucosal surface possesses a rough, 2D surface with a well preserved extracellular matrix. Such a material may be of advantage in tissue engineering of the esophagus. Characterisation of the papillary layer gives important insight into the suitability of decellularized esophageal mucosa for use in esophageal reconstruction and also provides morphological information which may help in the design of synthetic, biomimetic materials. [ABSTRACT FROM AUTHOR]