Stem Cell and Biologic Scaffold Engineering

Tissue engineering and regenerative medicine is a rapidly evolving research field which effectively combines stem cells and biologic scaffolds in order to replace damaged tissues. Biologic scaffolds can be produced through the removal of resident cellular populations using several tissue engineering approaches, such as the decellularization method. Indeed, the decellularization method aims to develop a cell-free biologic scaffold while keeping the extracellular matrix (ECM) intact. Furthermore, biologic scaffolds have been investigated for their in vitro potential for whole organ development. Currently, clinical products composed of decellularized matrices, such as pericardium, urinary bladder, small intestine, heart valves, nerve conduits, trachea, and vessels, are being evaluated for use in human clinical trials. Tissue engineering strategies require the interaction of biologic scaffolds with cellular populations. Among them, stem cells are characterized by unlimited cell division, self-renewal, and differentiation potential, distinguishing themselves as a frontline source for the repopulation of decellularized matrices and scaffolds. Under this scheme, stem cells can be isolated from patients, expanded under good manufacturing practices (GMPs), used for the repopulation of biologic scaffolds and, finally, returned to the patient. The interaction between scaffolds and stem cells is thought to be crucial for their infiltration, adhesion, and differentiation into specific cell types. In addition, biomedical devices such as bioreactors contribute to the uniform repopulation of scaffolds. Until now, remarkable efforts have been made by the scientific society in order to establish the proper repopulation conditions of decellularized matrices and scaffolds. However, parameters such as stem cell number, in vitro cultivation conditions, and specific growth media composition need further evaluation. The ultimate goal is the development of “artificial” tissues similar to native ones, which is achieved by properly combining stem cells and biologic scaffolds and thus bringing them one step closer to personalized medicine. The original research articles and comprehensive reviews in this Special Issue deal with the use of stem cells and biologic scaffolds that utilize state-of-the-art tissue engineering and regenerative medicine approaches

Giant liposarcoma of the back with 4 types of histopathology: a case report

The incidence of soft tissue tumours, both malignant and benign, is very common. However, the coexistence of 4 types of histopathology is rare and the aim of this article is to present one treated in our Department. An 87-year-old Greek man was treated in our Department for a huge tumour on his back, under local anaesthesia. The pathology report of the specimen referred 4 types of neoplasia. This case represents this incidence in a giant liposarcoma of the back

Biocompatibility and immunogenicity of decellularised allogeneic aorta in the orthotopic rat model

Background and aim of the study: Peripheral arterial disease causes blood vessel dysfunction that requires surgical intervention. Current surgical interventions employ synthetic or allogeneic vascular grafts, which offer biocompatible materials solutions that are not able to regenerate or grow with the patient. Decellularised scaffolds have gained significant momentum in the past few years, since they have the potential to regenerate in the patient. The aim of this study was to investigate the effects of modified decellularisation protocol on the biocompatibility and immunogenicity of allogeneic rat abdominal aorta in an orthotopic rat model. Methods: Native syngeneic Wistar (W) and allogeneic Dark Agouti (DA) aortas, together with decellularised allogeneic DA aortas, were assessed histologically, immunohistochemically and biomechanically. The immunogenicity of the untreated and decellularized syngeneic and allogeneic grafts was assessed in W rats, implanted orthotopically. Following implantation for 6 weeks, the grafts were explanted and assessed for the presence of T cells and macrophages by immunohistochemistry, and for their biomechanical integrity and histoarchitecture. Results: No obvious histoarchitectural differences were observed between the native W and DA aortas, with both presenting similar three-layered structures. Histological analysis of decellularized DA aortas did not reveal any remaining cells. Explanted native DA allografts showed media necrosis, partial elastic fibre degradation and adventitia thickening, as well as infiltration by lymphocytes (CD3+, CD4+) and macrophages (CD68+) in the adventitia. The explanted decellularized DA allografts indicated reduced immune injury compared to the explanted native DA allografts. The explanted native W syngeneic grafts showed a mild immune response, with an intact media and no lymphocyte infiltration. The explanted native DA allografts showed significantly lower collagen phase slope than the decellularized DA allografts prior implantation, and significantly higher thickness than the explanted decellularized DA allografts. Conclusions: The results indicated that the modified decellularization protocol did not affect significantly the mechanical and histological properties of the native DA rat aorta. Overall, the immune response was improved by decellularization. Native DA allografts induced an adverse immune response in W rats, whereas syngeneic W grafts showed good tissue integration

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Design and Fabrication of Artificial Stem Cell Microenvironments

Major key features of stem cells’ functions are self-renewal and their capacity for differentiation, allowing for maintain a proper stem cell reservoir as well as producing lineage-committed cells [...

Future Perspectives in Small-Diameter Vascular Graft Engineering

The increased demands of small-diameter vascular grafts (SDVGs) globally has forced the scientific society to explore alternative strategies utilizing the tissue engineering approaches. Cardiovascular disease (CVD) comprises one of the most lethal groups of non-communicable disorders worldwide. It has been estimated that in Europe, the healthcare cost for the administration of CVD is more than 169 billion €. Common manifestations involve the narrowing or occlusion of blood vessels. The replacement of damaged vessels with autologous grafts represents one of the applied therapeutic approaches in CVD. However, significant drawbacks are accompanying the above procedure; therefore, the exploration of alternative vessel sources must be performed. Engineered SDVGs can be produced through the utilization of non-degradable/degradable and naturally derived materials. Decellularized vessels represent also an alternative valuable source for the development of SDVGs. In this review, a great number of SDVG engineering approaches will be highlighted. Importantly, the state-of-the-art methodologies, which are currently employed, will be comprehensively presented. A discussion summarizing the key marks and the future perspectives of SDVG engineering will be included in this review. Taking into consideration the increased number of patients with CVD, SDVG engineering may assist significantly in cardiovascular reconstructive surgery and, therefore, the overall improvement of patients’ life

Short Term Results of Fibrin Gel Obtained from Cord Blood Units: A Preliminary in Vitro Study

Background: Recent findings have shown that the fibrin gel derived from cord blood units (CBUs) play a significant role in wound healing and tissue regeneration. The aim of this study was to standardize the fibrin gel production process in order to allow for its regular use. Methods: CBUs (n = 200) were assigned to 4 groups according to their initial volume. Then, a two-stage centrifugation protocol was applied in order to obtain platelet rich plasma (PRP). The concentration of platelets (PLTs), white blood cells (WBCs) and red blood cells (RBCs) were determined prior to and after the production process. In addition, targeted proteomic analysis using multiple reaction monitoring was performed. Finally, an appropriate volume of calcium gluconate was used in PRP for the production of fibrin gel. Results: The results of this study showed that high volume CBUs were characterized by greater recovery rates, concentration and number of PLTs compared to the low volume CBUs. Proteomic analysis revealed the presence of key proteins for regenerative medicine. Fibrin gel was successfully produced from CBUs of all groups. Conclusion: In this study, low volume CBUs could be an alternative source for the production of fibrin gel, which can be used in multiple regenerative medicine approaches

Evaluation of HLA-G Expression in Multipotent Mesenchymal Stromal Cells Derived from Vitrified Wharton’s Jelly Tissue

Background: Mesenchymal Stromal Cells (MSCs) from Wharton’s Jelly (WJ) tissue express HLA-G, a molecule which exerts several immunological properties. This study aimed at the evaluation of HLA-G expression in MSCs derived from vitrified WJ tissue. Methods: WJ tissue samples were isolated from human umbilical cords, vitrified with the use of VS55 solution and stored for 1 year at −196 °C. After 1 year of storage, the WJ tissue was thawed and MSCs were isolated. Then, MSCs were expanded until reaching passage 8, followed by estimation of cell number, cell doubling time (CDT), population doubling (PD) and cell viability. In addition, multilineage differentiation, Colony-Forming Units (CFUs) assay and immunophenotypic analyses were performed. HLA-G expression in MSCs derived from vitrified samples was evaluated by immunohistochemistry, RT-PCR/PCR, mixed lymphocyte reaction (MLR) and immunofluorescence. MSCs derived from non-vitrified WJ tissue were used in order to validate the results obtained from the above methods. Results: MSCs were successfully obtained from vitrified WJ tissues retaining their morphological and multilineage differentiation properties. Furthermore, MSCs from vitrified WJ tissues successfully expressed HLA-G. Conclusion: The above results indicated the successful expression of HLA-G by MSCs from vitrified WJ tissues, thus making them ideal candidates for immunomodulation

Introduction to the Special Issue on Stem Cell and Biologic Scaffold Engineering

Tissue engineering and regenerative medicine is a rapidly evolving research field that effectively combines stem cells and biologic scaffolds in order to replace damaged tissues. Biologic scaffolds can be produced through the removal of resident cellular populations using several tissue engineering approaches, such as the decellularization method. In addition, tissue engineering requires the interaction of biologic scaffolds with cellular populations. Stem cells are characterized by unlimited cell division, self-renewal, and differentiation potential, distinguishing themselves as a frontline source for the repopulation of decellularized matrices and scaffolds. However, parameters such as stem cell number, in vitro cultivation conditions, and specific growth media composition need further evaluation. The ultimate goal is the development of “artificial” tissues similar to native ones, which is achieved by properly combining stem cells and biologic scaffolds, thus bringing artificial tissues one step closer to personalized medicine. In this special issue of Bioengineering, we highlight the beneficial effects of stem cells and scaffolds in the emerging field of tissue engineering. The current issue includes articles regarding the use of stem cells in tissue engineering approaches and the proper production of biologically based scaffolds like nerve conduit, esophageal scaffold, and fibrin gel

Δημιουργία αγγείων από ανθρώπινο ομφάλιο λώρο και μελέτη της λειτουργικότητας τους πριν και μετά την κρυοκατάψυξη τους

Η ανάπτυξη και η χρήση συμβατών αγγειακών μοσχευμάτων μικρής διαμέτρου (<2 mm) αποτελεί μια από τις μεγαλύτερες προκλήσεις της σύγχρονης ιατρικής. Tα συγκεκριμένα μοσχεύματα βρίσκουν εφαρμογή σε επεμβάσεις αρτηριακής παράκαμψης, αιμοκάθαρσης και σε περιπτώσεις αποκατάστασης σε άτομα μικρής ηλικίας. Με βάση τα νεώτερα δεδομένα, η καρδιαγγειακή νόσος (ΚΑΝ) αποτελεί την πρώτη αιτία θανάτου των μη μεταδιδόμενων νοσημάτων στις αναπτυγμένες χώρες. Επιπρόσθετα, η νεφρική νόσος (οξεία-χρόνια) αποτελεί την ένατη αιτία θανάτου, ενώ περίπου 1.3 εκατομμύρια ασθενείς υποβάλλονται σε αιμοκάθαρση. Ως κύρια στρατηγική αντιμετώπισης αποτελεί η χρήση αυτόλογων μοσχευμάτων και πολυμερών/ συνθετικών υλικών τα οποία όμως εμφανίζουν σημαντικές επιπλοκές. Η συγκεκριμένη διατριβή έχει δύο πρωταρχικούς στόχους: 1) Την ανάπτυξη αγγειακών μοσχευμάτων <2 mm προερχόμενα από τον ανθρώπινο ομφάλιο λώρο, και 2) την αποθήκευση τους στους -196ο C και τον λειτουργικό έλεγχο αυτών. Για τον λόγο αυτό χρησιμοποιήθηκαν ανθρώπινες ομφαλικές αρτηρίες προερχόμενες από τελειόμηνες κυήσεις (38-40 εβδομάδων). Τα συγκεκριμένα αγγεία αποκυτταροποιήθηκαν με τη χρήση κατάλληλου πρωτοκόλλου και στην συνέχεια, αποθηκεύτηκαν σε υγρό άζωτο στους -196ο C με την χρήση του κρυοσυντηριτικού διαλύματος VS55. Ακολούθησε η αξιολόγηση της τρισδιάστατης δομής των αγγείων μέσω ιστολογικών χρώσεων, ποσοτικοποίησης του κολλαγόνου, των γλυκοζαμινογλυκανών και του γενετικού υλικού, κατόπιν της διαδικασίας αποκυτταροποίησης και κρυοσυντήρησης. Επίσης, προκειμένου να διαπιστωθεί εάν τα διαλύματα της αποκυτταροποίησης και της κρυοσυντήρησης επέφεραν τοξικότητα στα «δημιουργηθέντα» ικριώματα, διενεργήθηκε έλεγχος κυτταροτοξικότητας των δειγμάτων. Επιπρόσθετα πειράματα περιλάμβαναν την επανακυτταροποίηση των αγγεικών μοσχευμάτων με διαφοροποιημένους κυτταρικούς πληθυσμούς καθώς επίσης και πειράματα μεταμόσχευσης σε ζωικά μοντέλα. Συμπερασματικά, οι ανθρώπινες ομφαλικές αρτηρίες μπορούν να αποτελέσουν σημαντική πηγή για την ανάπτυξη εξατομικευμένων αγγειακών μοσχευμάτων μικρής διαμέτρου, καθιστώντας τα άμεσα προς διάθεση και χρήση στην περίπτωση που αυτά απαιτηθούν.of the biggest challenges in modern medicine is the development of functional small diameter vascular grafts (<2 mm). These grafts can be applied widely in coronary artery bypass surgery, hemodialysis treatment and reconstructive surgeries in pediatric patients. The cardiovascular disease (CAD) is one of the leading causes of death in developed countries. In addition, acute and chronic kidney disease is the 9th mortality reason, with 1.3 million of patients to be submitted in hemodialysis treatment. As primary therapeutic strategy is the use of autologous and polymer/synthetic vessels. However, their use is accompanied by major adverse reactions. Due to this, the use of alternative sources for the development of small diameter vascular grafts is an urgent need. This study aimed to the production of vascular grafts with diameter < 2 mm utilizing the human umbilical arteries. Second goal of this study was the successful long term storage of the produced vascular grafts at -196oC and the evaluation of their fuctionality. For this purpose, human umbilical arteries derived from end term gestations (38-40 weeks) were used. These vessels were decellularized according to a previous described protocol, then vitrified with the use of VS55 solution and stored for a time period of 2 years. Histological analysis, biochemical and biomechanical analysis was performed in order to evaluate the ultrastructure of the produced vascular grafts. Contact and tissue extract cytotoxicity assay was also performed in order to assess the possibility of toxicity in the produced grafts. Furthermore, recellularization of the vascular grafts was performed by the use of differentiated cellular populations such as ECs and VSMCs. Finally, transplantation of the vitrified vascular grafts was performed in a porcine model. Based on the results of this study, the human umbilical arteries could serve as an alternative source for the production of small diameter vascular grafts, and moreover could be used in personalized patient treatment