Decellularized matrices for tissue engineering

Effects of decellularization on glycosaminoglycans and collagen macromolecules in bovine bone extracellular matrix

Bovine bones were decellularized to obtain extracellular matrices with potential use for Tissue Bioengineering. The objective of the present study was to develop a decellularization protocol for bovine trabecular bone while maintaining the integrity of the extracellular matrix (ECM). The protocol proved to be effective in significantly reducing the Amount of genetic material and cellular content, and it was considered innovative, being filed as a patent. The scaffold obtained showed a reduction in the content of glycosaminoglycans (GAGs) and collagen. Even with the loss of these ECM components, the material obtained can be considered an alternative for use in Tissue Engineering and Regenerative Medicine.

Region-specific brain decellularized extracellular matrix promotes cell recovery in an in vitro model of stroke

Brain decellularized extracellular matrix (ECM) can be an attractive scaffold capable of mimicking the native ecosystem of the central nervous system tissue. We studied the in vitro response of neural cultures exposed to region-specific brain decellularized ECM scaffolds from three distinct neuroanatomical sections: cortex, cerebellum and remaining areas. First, each brain region was evaluated with the isotropic fractionator method to understand the cellular composition of the different cerebral areas. Second, the cerebral regions were subjected to the decellularization process and their respective characterization using molecular, histological, and ultrastructural techniques. Third, the levels of neurotrophic factors in the decellularized brain scaffold were analyzed. Fourth, we studied the region-specific brain decellularized ECM as a mimetic platform for the maturation of PC12 cells, as a unidirectional model of differentiation. Finally, in vitro studies were carried out to evaluate the cell recovery capacity of brain decellularized ECM under stroke-mimetic conditions. Our results show that region-specific brain decellularized ECM can serve as a biomimetic scaffold capable of promoting the growth of neural lineage cells and, in addition, it possesses a combination of structural and biochemical signals (e.g., neurotrophic factors) that are capable of inducing cell phenotypic changes and promote viability and cell recovery in a stroke/ischemia model in vitro.

Innovative approaches to tissue engineering: Utilizing decellularized extracellular matrix hydrogels for mesenchymal stem cell transport

In recent years, the realm of tissue regeneration experienced significant advancements, leading to the development of innovative therapeutic agents. The systemic delivery of mesenchymal stem cells (MSCs) emerged as a promising strategy for promoting tissue regeneration. However, this approach is hindered by hurdles such as poor cell survival, limited cell propagation, and inadequate cell integration. Decellularized extracellular matrix (dECM) hydrogel serves as an innovative carrier that protects MSCs from the detrimental effects of the hostile microenvironment, facilitates their localization and retention at the injection site, and preserves their viability. Regarding its low immunogenicity, low cytotoxicity, high biocompatibility, and its ability to mimic natural extracellular matrix (ECM), this natural hydrogel offers a new avenue for systemic delivery of MSCs. This review digs into the properties of dECM hydrogels (dECMHs), the methods employed for decellularization and the utilization of dECMH as carriers for various types of MSCs for tissue regeneration purposes. This review also sheds light on the benefits of hybrid hydrogels composed of dECMH and other components such as proteins and polysaccharides. By addressing the limitations of conventional hydrogels and enhancing efficacy of cell therapy, dECMH opens new pathways for the future of tissue regeneration.

In vivo transplantation of intrahepatic cholangiocyte organoids with decellularized liver-derived hydrogels supports hepatic cellular proliferation and differentiation in chronic liver injury

The limited replicative potential of primary hepatocytes (Hep) is a major hurdle for obtaining sufficient quantity and quality hepatocytes during cell therapy in patients with liver failure. Intrahepatic cholangiocyte organoids (ICOs) derived from intrahepatic bile ducts differentiate into both hepatocytes and cholangiocytes in vitro. Here, we studied in vivo effects of transplanting ICOs and Hep in chronic liver injury mice models. Well characterized primary mouse ICOs and Hep were mixed in decellularized liver (DCL) matrix hydrogels and injected into the subcapsular left lateral liver lobe of CCl4-induced liver injury models whereas mice given DCL alone were in the sham group. Two weeks post-transplantation, transplanted liver lobes were collected and studied by histology and RNA sequencing. Transplanted animals did not exhibit any tumors, mortality or morbidity. Mice livers transplanted with ICOs had increased cellular proliferation and vascularization as compared to Hep transplanted mice or sham. Collagen deposition in the liver was significantly reduced and serum albumin levels were significantly increased in transplanted groups compared to the sham group. Expression of genes associated with hepatocyte differentiation was highest in Hep transplanted livers among the three groups, but they were also upregulated in ICO transplanted livers compared to sham. Our study demonstrates that ICOs encapsulated in DCL hydrogels when transplanted in chronically injured mice livers engraft well and show hepatocyte differentiation and reduction of fibrosis, indicating that hydrogel transplanted cholangiocyte organoids may serve as an efficient cell source and therapy for renewal of hepatocytes, restoration of hepatocyte functions and resolution of liver injury.

LCST/UCST behavior of polysaccharides for hydrogel fabrication

Hydrogel-based scaffolds play a crucial role in widespread biotechnological applications by providing physicochemical stability to loaded cells or therapeutic agents, interacting with organismal microenvironments, and controlling cargo release. Polysaccharides are regarded as attractive candidates among substrate materials because of their high water-retaining capacity, reactive functional groups, ease of gelation, low immunogenicity, biodegradability, and biocompatibility. However, employing polysaccharide-based hydrogel scaffolds for practical use in response to ongoing physiological and pathological changes within the human body, such as insufficient mechanical strength, uncertain degradation, and uncontrollable release patterns, is challenging. Several physically noncovalent or chemically covalent crosslinking strategies have been utilized to modify the physicochemical properties and biofunctionality of polysaccharide-based hydrogels. Among them, thermo-responsive gelation systems have been considered a promising approach for fabricating advanced scaffolds, referred to as 'stimuli-responsive' or 'smart' hydrogels. This is because of the sol-gel transition with a single trigger, requiring no further environmental or chemical intervention, and in situ and reversible gelation under ambient physiological temperature changes in a minimally invasive manner. This review highlights the classification, reaction mechanisms, characteristics, and advanced studies on thermo-responsive polysaccharides exploited in various biomedical fields.

Mimicking the extracellular world: from natural to fully synthetic matrices utilizing supramolecular biomaterials

The extracellular matrix (ECM) has evolved around complex covalent and non-covalent interactions to create impressive function-from cellular signaling to constant remodeling. A major challenge in the biomedical field is the de novo design and control of synthetic ECMs for applications ranging from tissue engineering to neuromodulation to bioelectronics. As we move towards recreating the ECM's complexity in hydrogels, the field has taken several approaches to recapitulate the main important features of the native ECM (i.e. mechanical, bioactive and dynamic properties). In this review, we first describe the wide variety of hydrogel systems that are currently used, ranging from fully natural to completely synthetic to hybrid versions, highlighting the advantages and limitations of each class. Then, we shift towards supramolecular hydrogels that show great potential for their use as ECM mimics due to their biomimetic hierarchical structure, inherent (controllable) dynamic properties and their modular design, allowing for precise control over their mechanical and biochemical properties. In order to make the next step in the complexity of synthetic ECM-mimetic hydrogels, we must leverage the supramolecular self-assembly seen in the native ECM; we therefore propose to use supramolecular monomers to create larger, hierarchical, co-assembled hydrogels with complex and synergistic mechanical, bioactive and dynamic features.

Biomimetic pulp scaffolds prepared from extracellular matrix derived from stem cells from human exfoliated deciduous teeth promote pulp-dentine complex regeneration

AIM

To evaluate the role of biomimetic pulp scaffolds derived from the extracellular matrix derived of stem cells from human exfoliated deciduous teeth (SHED-ECM-PS) in promoting pulp-dentine complex regeneration.

METHODOLOGY

SHED-ECM-PS was prepared through cell aggregation and decellularization techniques. Histological and immunofluorescence analyses, scanning electron microscopy, and DNA quantification assays were used to characterize the SHED-ECM-PS. Additionally, a tooth slice implantation model was established to evaluate the effects of SHED-ECM-PS on regeneration of the pulp-dentine complex in vivo. Extraction medium for SHED-ECM-PS was prepared, and its effect on bone marrow mesenchymal stem cells (BMMSCs) was assessed in vitro. Cell counting kit-8 and Ki-67 staining assays were performed to determine cell proliferation. The rate of apoptosis was evaluated by flow cytometry. Wound healing and transwell assays were conducted to evaluate cell migration. Alizarin red S staining was performed to examine mineralized nodule formation. Western blotting was used to detect the expression of osteogenic and odontogenic markers. The results were analysed using an independent two-tailed Student's t-test. p < .05 was considered statistically significant.

RESULTS

SHED-ECM-PS was successfully constructed, exhibiting a striped dental pulp-like shape devoid of nuclear structures or DNA components, and rich in fibronectin, collagen I, DMP1 and DSPP. Notably, SHED-ECM-PS showed no impact on the proliferation or apoptosis of BMMSCs. Histological analysis revealed that dental pulp fibroblasts formed an interwoven mesh in the root canal, and angiogenesis was observed in the SHED-ECM-PS group. Moreover, a continuous, newly formed tubular dentine layer with polarized odontoblast-like cells was observed along the inner wall of the root canal. SHED-ECM-PS promoted the migration, polar alignment and mineralized nodule formation of BMMSCs and specifically elevated the expression levels of odontogenic markers, but not osteogenic markers, compared with the control group in vitro.

CONCLUSION

SHED-ECM-PS exhibited no cytotoxicity and promoted pulp-dentine complex regeneration in vivo as well as cell migration and odontogenic differentiation of BMMSCs in vitro. These findings provide evidence that SHED-ECM-PS, as a novel biological scaffold, has the potential to improve the outcomes of REPs.

Two Decades of Advances and Limitations in Organ Recellularization

The recellularization of tissues after decellularization is a relatively new technology in the field of tissue engineering (TE). Decellularization involves removing cells from a tissue or organ, leaving only the extracellular matrix (ECM). This can then be recellularized with new cells to create functional tissues or organs. The first significant mention of recellularization in decellularized tissues can be traced to research conducted in the early 2000s. One of the landmark studies in this field was published in 2008 by Ott, where researchers demonstrated the recellularization of a decellularized rat heart with cardiac cells, resulting in a functional organ capable of contraction. Since then, other important studies have been published. These studies paved the way for the widespread application of recellularization in TE, demonstrating the potential of decellularized ECM to serve as a scaffold for regenerating functional tissues. Thus, although the concept of recellularization was initially explored in previous decades, these studies from the 2000s marked a major turning point in the development and practical application of the technology for the recellularization of decellularized tissues. The article reviews the historical advances and limitations in organ recellularization in TE over the last two decades.

Tissue-engineered and autologous pericardium in congenital heart surgery: comparative histopathological study of human vascular explants

OBJECTIVES

The goal of this histological study was to assess the biocompatibility of vascular patches used in the repair of congenital heart defects.

METHODS

We examined tissue-engineered bovine (n = 7) and equine (n = 7) patches and autologous human pericardium (n = 7), all explanted due to functional issues or follow-up procedures. Techniques like Movat-Verhoeff, von Kossa and immunohistochemical staining were used to analyse tissue composition, detect calcifications and identify immune cells. A semi-quantitative scoring system was implemented to evaluate the biocompatibility aspects, thrombus formation, extent of pannus, inflammation of pannus, cellular response to patch material, patch degradation, calcification and neoadventitial inflammation.

RESULTS

We observed distinct material degradation patterns among types of patches. Bovine patches showed collagen disintegration and exudate accumulation, whereas equine patches displayed edematous swelling and material dissolution. Biocompatibility scores were lower in terms of cellular response, degradation and overall score for human autologous pericardial patches compared to tissue-engineered types. The extent of pannus formation was not influenced by the type of patch. Bovine patches had notable calcifications causing tissue hardening, and foreign body giant cells were more frequently seen in equine patches. Plasma cells were frequently detected in the neointimal tissue of engineered patches.

CONCLUSIONS

Our results confirm the superior biocompatibility of human autologous patches and highlight discernible variations in the changes of patch material and the cellular response to patch material between bovine and equine patches. Our approach implements the semi-quantitative scoring of various aspects of biocompatibility, facilitating a comparative quantitative analysis across all types of patches, despite their inherent differences.

Decellularized extracellular matrix biomaterials for regenerative therapies: Advances, challenges and clinical prospects

Tissue engineering and regenerative medicine have shown potential in the repair and regeneration of tissues and organs via the use of engineered biomaterials and scaffolds. However, current constructs face limitations in replicating the intricate native microenvironment and achieving optimal regenerative capacity and functional recovery. To address these challenges, the utilization of decellularized tissues and cell-derived extracellular matrix (ECM) has emerged as a promising approach. These biocompatible and bioactive biomaterials can be engineered into porous scaffolds and grafts that mimic the structural and compositional aspects of the native tissue or organ microenvironment, both in vitro and in vivo. Bioactive dECM materials provide a unique tissue-specific microenvironment that can regulate and guide cellular processes, thereby enhancing regenerative therapies. In this review, we explore the emerging frontiers of decellularized tissue-derived and cell-derived biomaterials and bio-inks in the field of tissue engineering and regenerative medicine. We discuss the need for further improvements in decellularization methods and techniques to retain structural, biological, and physicochemical characteristics of the dECM products in a way to mimic native tissues and organs. This article underscores the potential of dECM biomaterials to stimulate in situ tissue repair through chemotactic effects for the development of growth factor and cell-free tissue engineering strategies. The article also identifies the challenges and opportunities in developing sterilization and preservation methods applicable for decellularized biomaterials and grafts and their translation into clinical products.

Recent advances in soluble decellularized extracellular matrix for heart tissue engineering and organ modeling

Despite the advent of tissue engineering (TE) for the remodeling, restoring, and replacing damaged cardiovascular tissues, the progress is hindered by the optimal mechanical and chemical properties required to induce cardiac tissue-specific cellular behaviors including migration, adhesion, proliferation, and differentiation. Cardiac extracellular matrix (ECM) consists of numerous structural and functional molecules and tissue-specific cells, therefore it plays an important role in stimulating cell proliferation and differentiation, guiding cell migration, and activating regulatory signaling pathways. With the improvement and modification of cell removal methods, decellularized ECM (dECM) preserves biochemical complexity, and bio-inductive properties of the native matrix and improves the process of generating functional tissue. In this review, we first provide an overview of the latest advancements in the utilization of dECM in in vitro model systems for disease and tissue modeling, as well as drug screening. Then, we explore the role of dECM-based biomaterials in cardiovascular regenerative medicine (RM), including both invasive and non-invasive methods. In the next step, we elucidate the engineering and material considerations in the preparation of dECM-based biomaterials, namely various decellularization techniques, dECM sources, modulation, characterizations, and fabrication approaches. Finally, we discuss the limitations and future directions in fabrication of dECM-based biomaterials for cardiovascular modeling, RM, and clinical translation.

Recent developments in nanomaterials for upgrading treatment of orthopedics diseases

Nanotechnology has changed science in the last three decades. Recent applications of nanotechnology in the disciplines of medicine and biology have enhanced medical diagnostics, manufacturing, and drug delivery. The latest studies have demonstrated this modern technology's potential for developing novel methods of disease detection and treatment, particularly in orthopedics. According to recent developments in bone tissue engineering, implantable substances, diagnostics and treatment, and surface adhesives, nanomedicine has revolutionized orthopedics. Numerous nanomaterials with distinctive chemical, physical, and biological properties have been engineered to generate innovative medication delivery methods for the local, sustained, and targeted delivery of drugs with enhanced therapeutic efficacy and minimal or no toxicity, indicating a very promising strategy for effectively controlling illnesses. Extensive study has been carried out on the applications of nanotechnology, particularly in orthopedics. Nanotechnology can revolutionize orthopedics cure, diagnosis, and research. Drug delivery precision employing nanotechnology using gold and liposome nanoparticles has shown especially encouraging results. Moreover, the delivery of drugs and biologics for osteosarcoma is actively investigated. Different kind of biosensors and nanoparticles has been used in the diagnosis of bone disorders, for example, renal osteodystrophy, Paget's disease, and osteoporosis. The major hurdles to the commercialization of nanotechnology-based composite are eventually examined, thus helping in eliminating the limits in connection to some pre-existing biomaterials for orthopedics, important variables like implant life, quality, cure cost, and pain and relief from pain. The potential for nanotechnology in orthopedics is tremendous, and most of it looks to remain unexplored, but not without challenges. This review aims to highlight the up tp date developments in nanotechnology for boosting the treatment modalities for orthopedic ailments. Moreover, we also highlighted unmet requirements and present barriers to the practical adoption of biomimetic nanotechnology-based orthopedic treatments.

Extracellular Matrix-Based and Electrospun Scaffolding Systems for Vaginal Reconstruction

Congenital vaginal anomalies and pelvic organ prolapse affect different age groups of women and both have significant negative impacts on patients' psychological well-being and quality of life. While surgical and non-surgical treatments are available for vaginal defects, their efficacy is limited, and they often result in long-term complications. Therefore, alternative treatment options are urgently needed. Fortunately, tissue-engineered scaffolds are promising new treatment modalities that provide an extracellular matrix (ECM)-like environment for vaginal cells to adhere, secrete ECM, and be remodeled by host cells. To this end, ECM-based scaffolds or the constructs that resemble ECM, generated by self-assembly, decellularization, or electrospinning techniques, have gained attention from both clinicians and researchers. These biomimetic scaffolds are highly similar to the native vaginal ECM and have great potential for clinical translation. This review article aims to discuss recent applications, challenges, and future perspectives of these scaffolds in vaginal reconstruction or repair strategies.

Fabrication and Evaluation of Porous dECM/PCL Scaffolds for Bone Tissue Engineering

Porous scaffolds play a crucial role in bone tissue regeneration and have been extensively investigated in this field. By incorporating a decellularized extracellular matrix (dECM) onto tissue-engineered scaffolds, bone regeneration can be enhanced by replicating the molecular complexity of native bone tissue. However, the exploration of porous scaffolds with anisotropic channels and the effects of dECM on these scaffolds for bone cells and mineral deposition remains limited. To address this gap, we developed a porous polycaprolactone (PCL) scaffold with anisotropic channels and functionalized it with dECM to capture the critical physicochemical properties of native bone tissue, promoting osteoblast cells' proliferation, differentiation, biomineralization, and osteogenesis. Our results demonstrated the successful fabrication of porous dECM/PCL scaffolds with multiple channel sizes for bone regeneration. The incorporation of 100 μm grid-based channels facilitated improved nutrient and oxygen infiltration, while the porous structure created using 30 mg/mL of sodium chloride significantly enhanced the cells' attachment and proliferation. Notably, the mechanical properties of the scaffolds closely resembled those of human bone tissue. Furthermore, compared with pure PCL scaffolds, the presence of dECM on the scaffolds substantially enhanced the proliferation and differentiation of bone marrow stem cells. Moreover, dECM significantly increased mineral deposition on the scaffold. Overall, the dECM/PCL scaffold holds significant potential as an alternative bone graft substitute for repairing bone injuries.

The conjunctival extracellular matrix, related disorders and development of substrates for conjunctival restoration

The conjunctiva can be damaged by numerous diseases with scarring, loss of tissue and dysfunction. Depending on extent of damage, restoration of function may require a conjunctival graft. A wide variety of biological and synthetic substrates have been tested in the search for optimal conditions for ex vivo culture of conjunctival epithelial cells as a route toward tissue grafts. Each substrate has specific advantages but also disadvantages related to their unique physical and biological characteristics, and identification and development of an improved substrate remains a priority. To achieve the goal of mimicking and restoring a biological material, requires information from the material. Specifically, extracellular matrix (ECM) derived from conjunctival tissue. Knowledge of the composition and structure of native ECM and identifying contributions of individual components to its function would enable using or mimicking those components to develop improved biological substrates. ECM is comprised of two components: basement membrane secreted predominantly by epithelial cells containing laminins and type IV collagens, which directly support epithelial and goblet cell adhesion differentiation and growth and, interstitial matrix secreted by fibroblasts in lamina propria, which provides mechanical and structural support. This review presents current knowledge on anatomy, composition of conjunctival ECM and related conjunctival disorders. Requirements of potential substrates for conjunctival tissue engineering and transplantation are discussed. Biological and synthetic substrates and their components are described in an accompanying review.

Biomaterial mediated immunomodulation: An interplay of material environment interaction for ameliorating wound regeneration

Chronic wounds are the outcome of an imbalanced inflammatory response caused by sustenance of immune microenvironment. In this context, tissue engineered graft played great role in healing wounds but faced difficulty in scar remodelling, immune rejection and poor vascularization. All the limitations faced are somewhere linked with the immune cells involved in healing. In this consideration, immunomodulatory biomaterials bridge a large gap with the delivery of modulating factors for triggering key inflammatory cells responsible towards interplay in the wound micro-environment. Inherent physico-chemical properties of biomaterials substantially determine the nature of cell-materials interaction thereby facilitating differential cytokine gradient involved in activation or suppression of inflammatory signalling pathways, and followed by surface marker expression. This review aims to systematically describe the interplay of immune cells involved in different phases in the wound microenvironment and biomaterials. Additionally, it also focuses on modulating innate immune cell responses in the context of triggering the halted phase of the wound healing, i.e., inflammatory phase. The various strategies are highlighted for modulation of wound microenvironment towards wound regeneration including stem cells, cytokines, growth factors, vitamins, and anti-inflammatory agents to induce interactive ability of biomaterials with immune cells. The last section focuses on prospective approaches and current potential strategies for wound regeneration. This includes the development of different models to bridge the gap between mouse models and human patients. Emerging new tools to study inflammatory response owing to biomaterials and novel strategies for modulation of monocyte and macrophage behaviour in the wound environment are also discussed.

Electrically conductive carbon-based (bio)-nanomaterials for cardiac tissue engineering

A proper self-regenerating capability is lacking in human cardiac tissue which along with the alarming rate of deaths associated with cardiovascular disorders makes tissue engineering critical. Novel approaches are now being investigated in order to speedily overcome the challenges in this path. Tissue engineering has been revolutionized by the advent of nanomaterials, and later by the application of carbon-based nanomaterials because of their exceptional variable functionality, conductivity, and mechanical properties. Electrically conductive biomaterials used as cell bearers provide the tissue with an appropriate microenvironment for the specific seeded cells as substrates for the sake of protecting cells in biological media against attacking mechanisms. Nevertheless, their advantages and shortcoming in view of cellular behavior, toxicity, and targeted delivery depend on the tissue in which they are implanted or being used as a scaffold. This review seeks to address, summarize, classify, conceptualize, and discuss the use of carbon-based nanoparticles in cardiac tissue engineering emphasizing their conductivity. We considered electrical conductivity as a key affecting the regeneration of cells. Correspondingly, we reviewed conductive polymers used in tissue engineering and specifically in cardiac repair as key biomaterials with high efficiency. We comprehensively classified and discussed the advantages of using conductive biomaterials in cardiac tissue engineering. An overall review of the open literature on electroactive substrates including carbon-based biomaterials over the last decade was provided, tabulated, and thoroughly discussed. The most commonly used conductive substrates comprising graphene, graphene oxide, carbon nanotubes, and carbon nanofibers in cardiac repair were studied.

[Methods of surgical reconstruction of the conjunctiva]

Reconstruction of the conjunctiva is required for restoration of damaged ocular surface and is an essential part of that process. Traumas, chemical and thermal burns, multiple surgical intervention can seriously damage the integrity of conjunctival tissue and promote the growth of fibrous tissue, scarring of contractures and their shortening, as well as other complications such as trichiasis, erosion and ulcers on the cornea. When a larger area is affected, there may not be enough donor tissue to replace the defect, in which case the tissue grafts are required to be large enough. Modern modifications of surgical techniques and the continued development of tissue engineering, as well as advancements in stem cell research offer promising novel alternatives for solution of those problems. This article reviews the existing surgical methods of conjunctival reconstruction.

Advancements in the Use of Hydrogels for Regenerative Medicine: Properties and Biomedical Applications

Due to their particular water absorption capacity, hydrogels are the most widely used scaffolds in biomedical studies to regenerate damaged tissue. Hydrogels can be used in tissue engineering to design scaffolds for three-dimensional cell culture, providing a novel alternative to the traditional two-dimensional cell culture as hydrogels have a three-dimensional biomimetic structure. This material property is crucial in regenerative medicine, especially for the nervous system, since it is a highly complex and delicate structure. Hydrogels can move quickly within the human body without physically disturbing the environment and possess essential biocompatible properties, as well as the ability to form a mimetic scaffold in situ. Therefore, hydrogels are perfect candidates for biomedical applications. Hydrogels represent a potential alternative to regenerating tissue lost after removing a brain tumor and/or brain injuries. This reason presents them as an exciting alternative to highly complex human physiological problems, such as injuries to the central nervous system and neurodegenerative disease.

Mid-term performance of decellularized equine pericardium in congenital heart surgery

OBJECTIVE

The aim was to report mid-term performance of decellularized equine pericardium used for repair of various congenital heart defects in the pediatric population.

METHODS

A retrospective review of all patients undergoing patch implantation between 2016 - 2020 was performed. Patch quality, surgical handling, hemostasis and early patch-related complications were studied on all patients. Mid-term performance was observed in patients with ≥12 months follow-up and intact patch at discharge (without reoperation/stent implantation).

RESULTS

A total of 201 patients with median age of 2.5 years [interquartile range (IQR): 0.6-6.5] underwent 207 procedures at 314 implant locations. The patch was used in following numbers/locations: 171 for pulmonary artery (PA) augmentation, 36 for aortic repair, 35 for septal defect closure, 22 for valvular repair and 50 at other locations. Early/30-day mortality was 6.5%. Early patch-related reoperations/stent implantations occurred in 28 locations (8.9%). No patch-related complications were noted except for bleeding from implant site in three locations (1%). Follow-up ≥ 12 months was available for 132 patients/200 locations. During a median follow-up of 29.7 months [IQR: 20.7-38.3], 53 patch-related reoperations/catheter reinterventions occurred (26.5%) with the majority in PA position (88.7%, 47/53). Overall 12- and 24-months freedom from patch-related reoperation/catheter reintervention per location was 91.5% (95% CI: 86.7%-94.6%) and 85.2% (95% CI: 78.9%-89.6%) respectively.

CONCLUSION

Decellularized equine pericardium used for repair of various congenital heart defects showed acceptable mid-term performance. Reoperation/reintervention rates were in a range as observed with other xenogeneic materials previously reported articles, occurring most frequently after PA augmentation.

Decellularized vs Non-decellularized Allogeneic Pulmonary Artery Patches for Pulmonary Arterioplasty

We studied pulmonary artery size, reinterventions, and panel reactive antibodies in patients with single-ventricle physiology who underwent a pulmonary arterioplasty with decellularized (DAPAP) and non-decellularized allogeneic pulmonary artery patches (non-DAPAP). Retrospective review identified 59 patients with single-ventricle physiology who underwent pulmonary arterioplasty from 2008 to 2017: 28 patients underwent arterioplasty with DAPAP and 31 patients with non-DAPAP. Demographic and operative variables were similar between groups. Among patients who underwent a Norwood procedure, a right ventricle to pulmonary artery shunt was more commonly used in the DAPAP group (12/20, 60%) and a modified Blalock-Taussig shunt was more commonly used in the non-DAPAP group (17/22, 77%). On multivariable analysis, the use of DAPAP was associated with higher pre-Fontan angiography Z-scores in right (estimate = 0.17, standard error = 0.04, P = 0.0005) and left pulmonary arteries (estimate = 0.12, standard error = 0.05, P = 0.01). No areas of calcification, discrete coarctation, or pulmonary dilation were noted in any of the pulmonary arteries. On multivariable analysis, the use of DAPAP was associated with higher freedom from pulmonary artery reinterventions (Hazard ratio = 0.36, 95% confidence interval = 0.13-0.9, P = 0.04). The median value for Class I panel reactive antibodies was 0% (IQR 0, 4) in the DAPAP and 23% (IQR 14, 36) in the non-DAPAP group. The median value for Class II panel reactive antibodies was 15% (IQR 0, 17) in the DAPAP and 21% (IQR 10, 22) in the non-DAPAP group. Pulmonary arterioplasty with DAPAP was associated with higher pre-Fontan pulmonary artery Z-scores and higher freedom from pulmonary artery reinterventions.

Decellularized adipose tissue matrix-coated and simvastatin-loaded hydroxyapatite microspheres for bone regeneration

Simvastatin (SIM)-loaded and human decellularized adipose tissue (DAT)-coated porous hydroxyapatite (HAp) microspheres were developed for the first time to investigate their potential on bone regeneration. Microspheres were loaded with SIM and then coated with DAT for modifying SIM release and improving their biological response. HAp microspheres were prepared by water-in-oil emulsion method using camphene (C₁₀ H₁₆ ) as porogen followed by camphene removal by freeze-drying and sintering at 1200°C for 3 h. Sintered HAp microspheres with an average particle size of ~400 µm were porous and spherical in shape. Microspheres were incubated with 1, 2.5, and 5 mg/ml SIM stock solutions for drug loading, and drug loading was determined as 7.5 ± 0.79, 20.41 ± 1.93, and 46.26 ± 0.29 µg SIM/mg microspheres, respectively. SIM loading increased with the increase of the initial SIM loading amount. Faster SIM release was observed in DAT-coated microspheres compared to bare counterparts. Higher SaoS-2 cell attachment and proliferation were observed on DAT-coated microspheres. Significantly higher alkaline phosphatase activity of SaoS-2 cells was observed on DAT-coated microspheres containing 0.01 mg/ml SIM than all other groups (p < 0.01). DAT-coated microspheres loaded with SIM at low doses hold promise for bone tissue engineering applications.

Decellularized Human Umbilical Tissue-Derived Hydrogels Promote Proliferation and Chondrogenic Differentiation of Mesenchymal Stem Cells

Tissue engineering is a promising approach for the repair and regeneration of cartilaginous tissue. Appropriate three-dimensional scaffolding materials that mimic cartilage are ideal for the repair of chondral defects. The emerging decellularized tissue-based scaffolds have the potential to provide essential biochemical signals and structural integrity, which mimics the natural tissue environment and directs cellular fate. Umbilical cord-derived hydrogels function as 3D scaffolding material, which support adherence, proliferation, migration, and differentiation of cells due to their similar biochemical composition to cartilage. Therefore, the present study aimed to establish a protocol for the formulation of a hydrogel from decellularized human umbilical cord (DUC) tissue, and assess its application in the proliferation and differentiation of UC-MSCs along chondrogenic lineage. The results showed that the umbilical cord was efficiently decellularized. Subsequently, DUC hydrogel was prepared, and in vitro chondral differentiation of MSCs seeded on the scaffold was determined. The developed protocol efficiently removed the cellular and nuclear content while retaining the extracellular matrix (ECM). DUC tissue, pre-gel, and hydrogels were evaluated by FTIR spectroscopy, which confirmed the gelation from pre-gel to hydrogel. SEM analysis revealed the fibril morphology and porosity of the DUC hydrogel. Calcein AM and Alamar blue assays confirmed the MSC survival, attachment, and proliferation in the DUC hydrogels. Following seeding of UC-MSCs in the hydrogels, they were cultured in stromal or chondrogenic media for 28 days, and the expression of chondrogenic marker genes including TGF-β1, BMP2, SOX-9, SIX-1, GDF-5, and AGGRECAN was significantly increased (* p ≤ 0.05, ** p ≤ 0.01, *** p ≤ 0.001). Moreover, the hydrogel concentration was found to significantly affect the expression of chondrogenic marker genes. The overall results indicate that the DUC-hydrogel is compatible with MSCs and supports their chondrogenic differentiation in vitro.

Recent scaffold-based tissue engineering approaches in premature ovarian failure treatment

Recently, tissue engineering and regenerative medicine have received significant attention with outstanding advances. The main scope of this technology is to recover the damaged tissues and organs or to maintain and improve their function. One of the essential fields in tissue engineering is scaffold designing and construction, playing an integral role in damaged tissues reconstruction and repair. However, premature ovarian failure (POF) is a disorder causing many medical and psychological problems in women. POF treatment using tissue engineering and various scaffold has recently made tremendous and promising progress. Due to the importance of the subject, we have summarized the recently examined scaffolds in the treatment of POF in this review.

Bioactive Decellularized Extracellular Matrix Hydrogel Microspheres Fabricated Using a Temperature-Controlling Microfluidic System

Hydrogel microspheres have drawn great attention as functional three-dimensional (3D) microcarriers for cell attachment and growth, which have shown great potential in cell-based therapies and biomedical research. Hydrogels derived from a decellularized extracellular matrix (dECM) retain the intrinsic physical and biological cues from the native tissues, which often exhibit high bioactivity and tissue-specificity in promoting tissue regeneration. Herein, a novel two-stage temperature-controlling microfluidic system was developed which enabled production of pristine dECM hydrogel microspheres in a high-throughput manner. Porcine decellularized peripheral nerve matrix (pDNM) was used as the model raw dECM material for continuous generation of pDNM microgels without additional supporting materials or chemical crosslinking. The sizes of the microspheres were well-controlled by tuning the feed ratios of water/oil phases into the microfluidic device. The resulting pDNM microspheres (pDNM-MSs) were relatively stable, which maintained a spherical shape and a nanofibrous ultrastructure for at least 14 days. Schwann cells and PC12 cells preseeded on the pDNM-MSs not only showed excellent viability and an adhesive property, but also promoted cell extension compared to the commercially available gelatin microspheres. Moreover, primary neural stem/progenitor cells attached well to the pDNM-MSs, which further facilitated their proliferation. The successfully fabricated dECM hydrogel microspheres provided a highly bioactive microenvironment for 3D cell culture and functionalization, which showed promising potential in versatile biomedical applications.

Mechanical and Biocompatibility Properties of Sintered Titanium Powder for Mimetic 3D-Printed Bone Scaffolds

A composite comprising Ti and NaCl powders was sintered similar to a three-dimensional (3D)-printed patient-customized artificial bone scaffold. Additionally, a proper microstructure of the mimetic scaffold and the optimum processing parameters for its development were analyzed. The mechanical properties of the metal-based porous-structured framework used as an artificial bone scaffold were an optimum replacement for the human bone. Thus, it was confirmed that patient-customized scaffolds could be manufactured via 3D printing. The 3D-printed mimetic specimens were fabricated by a powder-sintering method using Ti for the metal parts, NaCl as the pore former, and polylactic acid as the biodegradable binder. Scanning electron microscopy (SEM) images showed that pores were formed homogeneously, while X-ray computed tomography confirmed that open pores were generated. The porosity and pore size distribution were measured using a mercury porosimeter, while the flexural strength and flexural elastic modulus were calculated using the three-point bending test. Based on these measurements, a pore-former content of 15 vol % optimized the density and flexural strength to 2.52 g cm^-2 and 283 MPa, respectively, similar to those of the actual iliac bone. According to the 3D-printing production method, a selective laser-sintering process was applied for the fabrication of the mimetic specimen, and it was determined that the microstructure and properties similar to those of previous metal specimens could be achieved in the as-prepared specimen. Additionally, a decellularized extracellular matrix (dECM) was used to coat the surfaces and interiors of the specimens for evaluating their biocompatibilities. SEM image analysis indicated that the adipose-derived stem cells grew evenly inside the pores of the coated specimens, as compared with the bulky Ti specimens without the dECM coating. The doubling time at 65% was measured at 72, 75, and 83 h for specimens with pore-former contents of 5, 10, and 15 vol %, respectively. The doubling time without the pore former was 116 h. As compared with the specimens without the pore former (73 h), 15% of the dECM-coated specimens showed a doubling time of 64%, measured at 47 h.

A physiologically relevant, estradiol‐17β [E2]‐responsive in vitro tissue‐engineered model of the vaginal epithelium for vaginal tissue research

Aims

There are many situations where preclinical models of the human vagina would be valuable for in vitro studies into the pathophysiology of vaginally transmitted diseases, microbicide efficacy, irritability testing, and particularly, for assessing materials to be inserted in the vagina for support of the pelvic floor. The aim of this study is to develop a physiologically relevant, low cost, and ethically suitable model of the vagina using sheep vaginal tissue (SVT) to reduce the need for animal testing in gynecological research.

Methods

Tissue‐engineered (TE) vaginal models were developed by culturing primary vaginal epithelial cells and vaginal fibroblasts, isolated from the native SVTs on decellularized sheep vaginal matrices at an air–liquid interface. Morphological analyses of the models were conducted by performing hematoxylin and eosin staining and further characterization was done by immunohistofluorescence (IHF) of structural proteins and cytokeratins.

Results

Histological analysis of the models revealed a gradual formation of a stratified epithelium on our decellularized matrices and cell metabolic activity remained high for 21 days as measured by the resazurin assay. Our models showed a dose‐dependent response to estradiol‐17β [E₂] with an increase in the vaginal epithelium thickness and cellular proliferation under higher E₂ concentrations (100–400 pg/ml). The physiological relevance of these results was confirmed by the IHF analysis of Ki67, and cytokeratins 10 and 19 expression.

Conclusion

In this study, we have developed an estradiol‐responsive TE vaginal model that closely mimics the structural and physiological properties of the native SVT.

The advances in nanomedicine for bone and cartilage repair

With the gradual demographic shift toward an aging and obese society, an increasing number of patients are suffering from bone and cartilage injuries. However, conventional therapies are hindered by the defects of materials, failing to adequately stimulate the necessary cellular response to promote sufficient cartilage regeneration, bone remodeling and osseointegration. In recent years, the rapid development of nanomedicine has initiated a revolution in orthopedics, especially in tissue engineering and regenerative medicine, due to their capacity to effectively stimulate cellular responses on a nanoscale with enhanced drug loading efficiency, targeted capability, increased mechanical properties and improved uptake rate, resulting in an improved therapeutic effect. Therefore, a comprehensive review of advancements in nanomedicine for bone and cartilage diseases is timely and beneficial. This review firstly summarized the wide range of existing nanotechnology applications in the medical field. The progressive development of nano delivery systems in nanomedicine, including nanoparticles and biomimetic techniques, which are lacking in the current literature, is further described. More importantly, we also highlighted the research advancements of nanomedicine in bone and cartilage repair using the latest preclinical and clinical examples, and further discussed the research directions of nano-therapies in future clinical practice.

Detection of Human Neutrophil Elastase by Fluorescent Peptide Sensors Conjugated to TEMPO-Oxidized Nanofibrillated Cellulose

Peptide-cellulose conjugates designed for use as optical protease sensors have gained interest for point-of-care (POC) detection. Elevated serine protease levels are often found in patients with chronic illnesses, necessitating optimal biosensor design for POC assessment. Nanocellulose provides a platform for protease sensors as a transducer surface, and the employment of nanocellulose in this capacity combines its biocompatibility and high specific surface area properties to confer sensitive detection of dilute biomarkers. However, a basic understanding of the spatiotemporal relationships of the transducer surface and sensor disposition is needed to improve protease sensor design and development. Here, we examine a tripeptide, fluorogenic elastase biosensor attached to TEMPO-oxidized nanofibrillated cellulose via a polyethylene glycol linker. The synthetic conjugate was found to be active in the presence of human neutrophil elastase at levels comparable to other cellulose-based biosensors. Computational models examined the relationship of the sensor molecule to the transducer surface. The results illustrate differences in two crystallite transducer surfaces ((110) vs. (1-10)) and reveal preferred orientations of the sensor. Finally, a determination of the relative (110) vs. (1-10) orientations of crystals extracted from cotton demonstrates a preference for the (1-10) conformer. This model study potentiates the HNE sensor results for enhanced sensor activity design.

Bioinks Enriched with ECM Components Obtained by Supercritical Extraction

Extracellular matrix (ECM)-based bioinks have been steadily gaining interest in the field of bioprinting to develop biologically relevant and functional tissue constructs. Herein, we propose the use of supercritical carbon dioxide (scCO₂) technology to extract the ECM components of cell-sheets that have shown promising results in creating accurate 3D microenvironments replicating the cell’s own ECM, to be used in the preparation of bioinks. The ECM extraction protocol best fitted for cell sheets was defined by considering efficient DNA removal with a minor effect on the ECM. Cell sheets of human dermal fibroblasts (hDFbs) and adipose stem cells (hASCs) were processed using a customised supercritical system by varying the pressure of the reactor, presence, exposure time, and type of co-solvent. A quantification of the amount of DNA, protein, and sulfated glycosaminoglycans (sGAGs) was carried out to determine the efficiency of the extraction in relation to standard decellularization methodologies. The bioinks containing the extracted ECM were fabricated by combining them with alginate as a support polymer. The influence of the alginate (1%, 2% w/vol) and ECM (0.5% and 1.5% w/vol) amounts on the printability of the blends was addressed by analysing the rheological behaviour of the suspensions. Finally, 3D printed constructs were fabricated using an in-house built extrusion-based bioprinter, and the impact of the extrusion process on cell viability was assessed. The optimised scCO₂ protocol allowed efficient removal of DNA while preserving a higher number of proteins and sGAGs than the standard methodologies. The characterization of extract’s composition also revealed that the ECM produced by hDFbs (fECM) and hASCs (aECM) is distinctively affected by the extraction protocols. Furthermore, rheological analysis indicated an increase in viscosity with increasing ECM composition, an effect even more prominent in samples containing aECM. 3D printing of alginate/ECM constructs demonstrated that cell viability was only marginally affected by the extrusion process, and this effect was also dependent on the ECM source. Overall, this work highlights the benefits of supercritical fluid-based methods for ECM extraction and strengthens the relevance of ECM-derived bioinks in the development of printed tissue-like constructs.

Preservation of the naïve features of mesenchymal stromal cells in vitro: Comparison of cell- and bone-derived decellularized extracellular matrix

The fate and behavior of bone marrow mesenchymal stem/stromal cells (BM-MSC) is bidirectionally influenced by their microenvironment, the stem cell niche, where a magnitude of biochemical and physical cues communicate in an extremely orchestrated way. It is known that simplified 2D in vitro systems for BM-MSC culture do not represent their naïve physiological environment. Here, we developed four different 2D cell-based decellularized matrices (dECM) and a 3D decellularized human trabecular-bone scaffold (dBone) to evaluate BM-MSC behavior. The obtained cell-derived matrices provided a reliable tool for cell shape-based analyses of typical features associated with osteogenic differentiation at high-throughput level. On the other hand, exploratory proteomics analysis identified native bone-specific proteins selectively expressed in dBone but not in dECM models. Together with its architectural complexity, the physico-chemical properties of dBone triggered the upregulation of stemness associated genes and niche-related protein expression, proving in vitro conservation of the naïve features of BM-MSC.

Multifunctional GelMA platforms with nanomaterials for advanced tissue therapeutics

Polymeric hydrogels are fascinating platforms as 3D scaffolds for tissue repair and delivery systems of therapeutic molecules and cells. Among others, methacrylated gelatin (GelMA) has become a representative hydrogel formulation, finding various biomedical applications. Recent efforts on GelMA-based hydrogels have been devoted to combining them with bioactive and functional nanomaterials, aiming to provide enhanced physicochemical and biological properties to GelMA. The benefits of this approach are multiple: i) reinforcing mechanical properties, ii) modulating viscoelastic property to allow 3D printability of bio-inks, iii) rendering electrical/magnetic property to produce electro-/magneto-active hydrogels for the repair of specific tissues (e.g., muscle, nerve), iv) providing stimuli-responsiveness to actively deliver therapeutic molecules, and v) endowing therapeutic capacity in tissue repair process (e.g., antioxidant effects). The nanomaterial-combined GelMA systems have shown significantly enhanced and extraordinary behaviors in various tissues (bone, skin, cardiac, and nerve) that are rarely observable with GelMA. Here we systematically review these recent efforts in nanomaterials-combined GelMA hydrogels that are considered as next-generation multifunctional platforms for tissue therapeutics. The approaches used in GelMA can also apply to other existing polymeric hydrogel systems.

Acceleration of Bone Regeneration Induced by a Soft-Callus Mimetic Material

Clinical implementation of endochondral bone regeneration (EBR) would benefit from the engineering of devitalized cartilaginous constructs of allogeneic origins. Nevertheless, development of effective devitalization strategies that preserves extracellular matrix (ECM) is still challenging. The aim of this study is to investigate EBR induced by devitalized, soft callus-mimetic spheroids. To challenge the translatability of this approach, the constructs are generated using an allogeneic cell source. Neo-bone formation is evaluated in an immunocompetent rat model, subcutaneously and in a critical size femur defect. Living spheroids are used as controls. Also, the effect of spheroid maturation towards hypertrophy is evaluated. The devitalization procedure successfully induces cell death without affecting ECM composition or bioactivity. In vivo, a larger amount of neo-bone formation is observed for the devitalized chondrogenic group both ectopically and orthotopically. In the femur defect, accelerated bone regeneration is observed in the devitalized chondrogenic group, where defect bridging is observed 4 weeks post-implantation. The authors' results show, for the first time, a dramatic increase in the rate of bone formation induced by devitalized soft callus-mimetics. These findings pave the way for the development of a new generation of allogeneic, "off-the-shelf" products for EBR, which are suitable for the treatment of every patient.

Impact of Donor Age on the Osteogenic Supportive Capacity of Mesenchymal Stromal Cell-Derived Extracellular Matrix

Mesenchymal stromal cells (MSC) have been proposed as an emerging cell-based therapeutic option for regenerative medicine applications as these cells can promote tissue and organ repair. In particular, MSC have been applied for the treatment of bone fractures. However, the healing capacity of these fractures is often compromised by patient's age. Therefore, considering the use of autologous MSC, we evaluated the impact of donor age on the osteogenic potential of bone marrow (BM)-derived MSC. MSC from older patients (60 and 80 years old) demonstrated impaired proliferative and osteogenic capacities compared to MSC isolated from younger patients (30 and 45 years old), suggesting that aging potentially changes the quantity and quality of MSC. Moreover, in this study, we investigated the capacity of the microenvironment [i.e., extracellular matrix (ECM)] to rescue the impaired proliferative and osteogenic potential of aged MSC. In this context, we aimed to understand if BM MSC features could be modulated by exposure to an ECM derived from cells obtained from young or old donors. When aged MSC were cultured on decellularized ECM derived from young MSC, their in vitro proliferative and osteogenic capacities were enhanced, which did not happen when cultured on old ECM. Our results suggest that the microenvironment, specifically the ECM, plays a crucial role in the quality (assessed in terms of osteogenic differentiation capacity) and quantity of MSC. Specifically, the aging of ECM is determinant of osteogenic differentiation of MSC. In fact, old MSC maintained on a young ECM produced higher amounts of extracellularly deposited calcium (9.10 ± 0.22 vs. 4.69 ± 1.41 μg.μl-1.10-7 cells for young ECM and old ECM, respectively) and up-regulated the expression of osteogenic gene markers such as Runx2 and OPN. Cell rejuvenation by exposure to a functional ECM might be a valuable clinical strategy to overcome the age-related decline in the osteogenic potential of MSC by recapitulating a younger microenvironment, attenuating the effects of aging on the stem cell niche. Overall, this study provides new insights on the osteogenic potential of MSC during aging and opens new possibilities for developing clinical strategies for elderly patients with limited bone formation capacity who currently lack effective treatments.

Recapitulating the Cancer Microenvironment Using Bioprinting Technology for Precision Medicine

The complex and heterogenous nature of cancer contributes to the development of cancer cell drug resistance. The construction of the cancer microenvironment, including the cell-cell interactions and extracellular matrix (ECM), plays a significant role in the development of drug resistance. Traditional animal models used in drug discovery studies have been associated with feasibility issues that limit the recapitulation of human functions; thus, in vitro models have been developed to reconstruct the human cancer system. However, conventional two-dimensional and three-dimensional (3D) in vitro cancer models are limited in their ability to emulate complex cancer microenvironments. Advances in technologies, including bioprinting and cancer microenvironment reconstruction, have demonstrated the potential to overcome some of the limitations of conventional models. This study reviews some representative bioprinted in vitro models used in cancer research, particularly fabrication strategies for modeling and consideration of essential factors needed for the reconstruction of the cancer microenvironment. In addition, we highlight recent studies that applied such models, including application in precision medicine using advanced bioprinting technologies to fabricate biomimetic cancer models. Furthermore, we discuss current challenges in 3D bioprinting and suggest possible strategies to construct in vitro models that better mimic the pathophysiology of the cancer microenvironment for application in clinical settings.

Image-Based Method to Quantify Decellularization of Tissue Sections

Tissue decellularization is typically assessed through absorbance-based DNA quantification after tissue digestion. This method has several disadvantages, namely its destructive nature and inadequacy in experimental situations where tissue is scarce. Here, we present an image processing algorithm for quantitative analysis of DNA content in (de)cellularized tissues as a faster, simpler and more comprehensive alternative. Our method uses local entropy measurements of a phase contrast image to create a mask, which is then applied to corresponding nuclei labelled (UV) images to extract average fluorescence intensities as an estimate of DNA content. The method can be used on native or decellularized tissue to quantify DNA content, thus allowing quantitative assessment of decellularization procedures. We confirm that our new method yields results in line with those obtained using the standard DNA quantification method and that it is successful for both lung and heart tissues. We are also able to accurately obtain a timeline of decreasing DNA content with increased incubation time with a decellularizing agent. Finally, the identified masks can also be applied to additional fluorescence images of immunostained proteins such as collagen or elastin, thus allowing further image-based tissue characterization.

Pulmonary artery augmentation using decellularized equine pericardium (Matrix Patch™): initial single-centre experience

OBJECTIVES

The aim of this study was to report our initial experience when using Matrix Patch™ a cell-free equine-derived pericardium for the augmentation of branch pulmonary arteries (PAs) in children.

METHODS

Between September 2016 and September 2019, Matrix Patch was used for the augmentation of branch PAs in 96 patients and implanted in 147 separate locations. The median age at implantation was 3.2 years (interquartile range: 0.9-8.4), and 33% of patients were infants. The patch was used mainly in redo surgeries (89.6%). Intra-procedural feasibility and reinterventions were analysed. Primary end points were death or patch-related reoperation/stent implantation. Explanted patches were stained for recellularization/calcification, or to reveal proliferation/inflammation.

RESULTS

A total of 81 patients, who received patches in 119 separate locations, were followed within a median of 20 months (interquartile range: 10.2-30.2). Patients with early reoperation/stent implantation were excluded from follow-up. No patch-related death was noted. Survival at last follow-up was 88% (95% CI: 78.8-93.7%). Overall probability of freedom from reoperation/stent implantation per location, 12 and 24 months after initial surgery was 85.8% (95% CI: 76.2-91.7%) and 78.7 (95% CI: 65.9-87.2%), respectively. At 20 months, superficial proliferation with discrete macrophage activity was seen in explants; however, no signs of calcification are observed.

CONCLUSIONS

The initial experience with the Matrix Patch in PAs showed comparable results to other xenogeneic patch materials. Long-term follow-up data are needed to prove the desired durability of the patch in different locations.

A Preliminary Study on the Promotion of Canine Adipose-Derived Stem Cell Differentiation by Perfusion-Decellularized Ureter Matrix

BACKGROUND

This study was to assess the possibility of the perfusing decellularized ureters (DUs) promoting the differentiation of the canine adipose stem cell (cASCs).

METHODS

cASCs were isolated and cultured in different induction media to determine their multidirectional differentiation potential. The perfusion system was used to prepare the DUs, and the prepared DUs were systematically evaluated. The DU coating was prepared by enzymatic digestion for cell culture. The cASCs were seeded on the coverslips covered with DU coating and samples were collected on days 3, 7, and 10. Immunofluorescence staining and molecular biology testing were used to examine the differentiation of cASCs seeded on the DU coating.

RESULTS

The cASCs were isolated and identified by flow cytometry. The prepared DUs removed the nuclear materials, and the 3-dimensional structure and biological compositions of the ureter were well preserved. Immunofluorescence staining showed the expression of anti-alpha smooth muscle actin (α-SMA). Western blot results suggested that the content of α-SMA in the experimental group was significantly higher than that in the control group at 3 different time points, and the mRNA expressions of α-SMA in the experimental group gradually increased with extended the culture time, whereas there was no significant change in the control group.

CONCLUSION

The cASCs seeded on the coverslips of DU coating could differentiate into smooth muscle cells, and the number of differentiated cASCs increased significantly with extended incubation time.

Osteochondral Tissue Engineering: The Potential of Electrospinning and Additive Manufacturing

The socioeconomic impact of osteochondral (OC) damage has been increasing steadily over time in the global population, and the promise of tissue engineering in generating biomimetic tissues replicating the physiological OC environment and architecture has been falling short of its projected potential. The most recent advances in OC tissue engineering are summarised in this work, with a focus on electrospun and 3D printed biomaterials combined with stem cells and biochemical stimuli, to identify what is causing this pitfall between the bench and the patients' bedside. Even though significant progress has been achieved in electrospinning, 3D-(bio)printing, and induced pluripotent stem cell (iPSC) technologies, it is still challenging to artificially emulate the OC interface and achieve complete regeneration of bone and cartilage tissues. Their intricate architecture and the need for tight spatiotemporal control of cellular and biochemical cues hinder the attainment of long-term functional integration of tissue-engineered constructs. Moreover, this complexity and the high variability in experimental conditions used in different studies undermine the scalability and reproducibility of prospective regenerative medicine solutions. It is clear that further development of standardised, integrative, and economically viable methods regarding scaffold production, cell selection, and additional biochemical and biomechanical stimulation is likely to be the key to accelerate the clinical translation and fill the gap in OC treatment.

Biological tissues and components, and synthetic substrates for conjunctival cell transplantation

The conjunctiva is the largest component of the ocular surface. It can be damaged by various pathological processes leading to scarring, loss of tissue and dysfunction. Depending on the amount of damage, restoration of function may require a conjunctival graft. Numerous studies have investigated biological and synthetic substrates in the search for optimal conditions for the ex vivo culture of conjunctival epithelial cells that can be used as tissue grafts for transplantation. These substrates have advantages and disadvantages that are specific to the characteristics of each material; the development of an improved material remains a priority. This review is the second of a two-part review in The Ocular Surface. In the first review, the structure and function of the conjunctiva was evaluated with a focus on the extracellular matrix and the basement membrane, and biological and mechanical characteristics of the ideal substrate with recommendations for further studies. In this review the types of biological and synthetic substrates used for conjunctival transplantation are discussed including substrates based on the extracellular matrix. .

Prospective Multicenter Evaluation of an Advanced Extracellular Matrix for Wound Management

OBJECTIVE

To evaluate an advanced extracellular matrix made of ovine forestomach matrix (OFM) for healing a variety of wound types.

METHODS

Participants were enrolled from inpatient, outpatient, and home healthcare settings. The OFM was used to treat all wounds and applied to the wound bed every 3 to 7 days until closure.

RESULTS

Researchers enrolled 29 participants with 33 wounds. Average time to wound closure was 8.2 weeks, the percentage of wounds that reduced in size by 50% or more at 4 weeks was 64%, the average wound area reduction at 4 weeks was 66%, and 73% of wounds had closed at 12 weeks. No adverse effects were observed.

CONCLUSIONS

This represents the first Canadian evaluation of OFM for the treatment of wounds, and the positive healing outcomes observed could support more widespread adoption of this matrix.

Rapid Preparation Method for Preparing Tracheal Decellularized Scaffolds: Vacuum Assistance and Optimization of DNase I

Decellularized scaffolds are an effective way for tracheal tissue engineering to perform alternative treatments. However, clinically used decellularized tracheal scaffolds have a long preparation cycle. The purpose of this study is to improve the efficiency of decellularization by vacuum assistance and optimizing the concentration of DNase I in the decellularization process and to quickly obtain tracheal decellularized scaffolds. The trachea of New Zealand white rabbits was decellularized with 2, 4, 6, and 8 KU/mL DNase I under vacuum. The performance of the decellularized tracheal scaffold was evaluated through histological analysis, immunohistochemical staining, DNA residue, extracellular matrix composition, scanning electron microscopy, mechanical properties, cell compatibility, and in vivo experiments. Histological analysis and immunohistochemical staining showed that compared with the native trachea, the hierarchical structure of the decellularized trachea remained unchanged after decellularization, nonchondrocytes were effectively removed, and the antigenicity of the scaffold was significantly weakened. Deoxyribonucleic acid (DNA) quantitative analysis showed that the amount of residual DNA in the 6-KU group was significantly decreased. Scanning electron microscopy and mechanical tests showed that small gaps appeared in the basement membrane of the 6-KU group, and the mechanical properties decreased. The CCK-8 test results and in vivo experiments showed that the 6-KU group's acellular scaffold had good cell compatibility and new blood vessels were visible on the surface. Taken together, the 6-KU group could quickly prepare rabbit tracheal scaffolds with good decellularization effects in only 2 days, which significantly shortened the preparation cycle reducing the required cost.

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.

Stabilized albumin coatings on engineered xenografts for attenuation of acute immune and inflammatory responses

Xenogeneic grafts are promising candidates for transplantation therapy due to their easily accessible sources. Nevertheless, the immune and inflammatory responses induced by xenografts need to be addressed for clinical use. A novel and facile method was introduced for the attenuation of immune and inflammatory responses by extending the immune evasion potential of albumin to the tissue engineering field and coating albumin, which could passivate biomaterial surfaces, onto xenografts. Albumin was first modified by dopamine to enhance its adhesion on graft surfaces. Porcine chondrocytes derived living hyaline cartilage graft (LhCG) and decellularized LhCG (dLhCG) were applied as xenograft models implanted in the omentum of rats. Both LhCG which contained porcine chondrocytes as well as secreted ECM and dLhCG which was mainly composed of the porcine source ECM showed alleviated immune and inflammatory responses after being coated with albumin at cell, protein and gene levels, respectively. Significantly less inflammatory cells including neutrophils, macrophages and lymphocytes were recruited according to pathological analysis and immunohistochemistry staining with lower gene expression encoding inflammation-related cytokines including MCP-1, IL-6 and IL-1β after employing LhCG and dLhCG with albumin passivation coating.

Atomic force microscopy for revealing micro/nanoscale mechanics in tumor metastasis: from single cells to microenvironmental cues

Mechanics are intrinsic properties which appears throughout the formation, development, and aging processes of biological systems. Mechanics have been shown to play important roles in regulating the development and metastasis of tumors, and understanding tumor mechanics has emerged as a promising way to reveal the underlying mechanisms guiding tumor behaviors. In particular, tumors are highly complex diseases associated with multifaceted factors, including alterations in cancerous cells, tissues, and organs as well as microenvironmental cues, indicating that investigating tumor mechanics on multiple levels is significantly helpful for comprehensively understanding the effects of mechanics on tumor progression. Recently, diverse techniques have been developed for probing the mechanics of tumors, among which atomic force microscopy (AFM) has appeared as an excellent platform enabling simultaneously characterizing the structures and mechanical properties of living biological systems ranging from individual molecules and cells to tissue samples with unprecedented spatiotemporal resolution, offering novel possibilities for understanding tumor physics and contributing much to the studies of cancer. In this review, we survey the recent progress that has been achieved with the use of AFM for revealing micro/nanoscale mechanics in tumor development and metastasis. Challenges and future progress are also discussed.

Fabrication of Nanopores Polylactic Acid Microtubes by Core-Sheath Electrospinning for Capillary Vascularization

There has been substantial progress in tissue engineering of biological substitutes for medical applications. One of the major challenges in development of complex tissues is the difficulty of creating vascular networks for engineered constructs. The diameter of current artificial vascular channels is usually at millimeter or submillimeter level, while human capillaries are about 5 to 10 µm in diameter. In this paper, a novel core-sheath electrospinning process was adopted to fabricate nanoporous microtubes to mimic the structure of fenestrated capillary vessels. A mixture of polylactic acid (PLA) and polyethylene glycol (PEO) was used as the sheath solution and PEO was used as the core solution. The microtubes were observed under a scanning electron microscope and the images were analyzed by ImageJ. The diameter of the microtubes ranged from 1-8 microns. The diameter of the nanopores ranged from 100 to 800 nm. The statistical analysis showed that the microtube diameter was significantly influenced by the PEO ratio in the sheath solution, pump rate, and the viscosity gradient between the sheath and the core solution. The electrospun microtubes with nanoscale pores highly resemble human fenestrated capillaries. Therefore, the nanoporous microtubes have great potential to support vascularization in engineered tissues.

Long-term preservation effects on biological properties of acellular placental sponge patches

Decellularization, preservation protocol and storage time influence the biomechanical and biological properties of allografts and xenografts. Here, we examined the consequences of storage time on the antibacterial, angiogenic and biocompatibility properties of the decellularized placental sponge (DPS) in vitro and in vivo. The DPS samples were preserved for one, three and six months at -20 °C. The decellularized scaffolds showed uniform morphology with interconnected pores compared with not decellularized sponges. Storage time did not interfere with collagen and vascular endothelial growth factor contents, and cytobiocompatibility for Hu02 fibroblast cells. Chorioallantoic membrane assay and subcutaneous implantation indicated a decreased new vessel formation and neovascularization in six months DPS sample compared with other experimental groups. The number of CD4⁺ and CD68⁺ cells infiltrated into the six months DPS on the implanted site showed a significant increase compared with one and three months sponges. The antibacterial activities and angiogenic properties of the DPS decreased over storage time. Three months preservation at -20 °C is suggested as the optimal storage period to retain its antibacterial activity and high stimulation of new vessel formation. This storage protocol could be considered for preservation of similar decellularized placenta-derived products with the aim of retaining their biological properties.

Patient-derived scaffolds as a model of colorectal cancer

Background

Colorectal cancer is the second most common cause of cancer‐related death worldwide and standardized therapies often fail to treat the more aggressive and progressive types of colorectal cancer. Tumor cell heterogeneity and influence from the surrounding tumor microenvironment (TME) contribute to the complexity of the disease and large variability in clinical outcomes.

Methods

To model the heterogeneous nature of colorectal cancer, we used patient‐derived scaffolds (PDS), which were obtained via decellularization of surgically resected tumor material, as a growth substrate for standardized cell lines.

Results

After confirmation of native cell absence and validation of the structural and compositional integrity of the matrix, 89 colorectal PDS were repopulated with colon cancer cell line HT29. After 3 weeks of PDS culture, HT29 cells varied their gene and protein expression profiles considerably compared to 2D‐grown HT29 cells. Markers associated with proliferation were consistently decreased, while markers associated with pluripotency were increased in PDS‐grown cells compared to their 2D counterparts. When comparing the PDS‐induced changes in HT29 cells with clinically relevant tumor information from individual patients, we observed significant associations between stemness/pluripotency markers and tumor location, and between epithelial‐to‐mesenchymal transition (EMT) markers and cancer mortality. Kaplan–Meier analysis revealed that low PDS‐induced EMT correlated with worse cancer‐specific survival.

Conclusions

The colorectal PDS model can be used as a simplified personalized tool that can potentially reveal important diagnostic and pathophysiological information related to the TME.