Luminal endothelialization of small caliber silk tubular graft for vascular constructs engineering.

The constantly increasing incidence of coronary artery disease worldwide makes necessary to set advanced therapies and tools such as tissue engineered vessel grafts (TEVGs) to surpass the autologous grafts [(i.e., mammary and internal thoracic arteries, saphenous vein (SV)] currently employed in coronary artery and vascular surgery.

3D bioprinting of multi-layered segments of a vessel-like structure with ECM and novel derived bioink.

3D-Bioprinting leads to the realization of tridimensional customized constructs to reproduce the biological structural complexity. The new technological challenge focuses on obtaining a 3D structure with several distinct layers to replicate the hierarchical organization of natural tissues. This work aims to reproduce large blood vessel substitutes compliant with the original tissue, combining the advantages of the 3D bioprinting, decellularization, and accounting for the presence of different cells.

Towards an In Vitro Retinal Model to Study and Develop New Therapies for Age-Related Macular Degeneration.

Age-related macular degeneration (AMD) is the leading cause of vision loss in the elderly worldwide. So far, the etiology and the progression of AMD are not well known. Animal models have been developed to study the mechanisms involved in AMD; however, according to the "Three Rs" principle, alternative methods have been investigated.

A Perfusion Bioreactor for Longitudinal Monitoring of Bioengineered Liver Constructs.

In the field of in vitro liver disease models, decellularised organ scaffolds maintain the original biomechanical and biological properties of the extracellular matrix and are established supports for in vitro cell culture. However, tissue engineering approaches based on whole organ decellularized scaffolds are hampered by the scarcity of appropriate bioreactors that provide controlled 3D culture conditions. Novel specific bioreactors are needed to support long-term culture of bioengineered constructs allowing non-invasive longitudinal monitoring.

Insight on the endothelialization of small silk-based tissue-engineered vascular grafts.

Along with an increased incidence of cardiovascular diseases, there is a strong need for small-diameter vascular grafts. Silk has been investigated as a biomaterial to develop such grafts thanks to different processing options. Endothelialization was shown to be extremely important to ensure graft patency and there is ongoing research on the development and behavior of endothelial cells on vascular tissue-engineered scaffolds.

Shear-resistant hydrogels to control permeability of porous tubular scaffolds in vascular tissue engineering.

Aiming to perfuse porous tubular scaffolds for vascular tissue engineering (VTE) with controlled flow rate, prevention of leakage through the scaffold lumen is required. A gel coating made of 8% w/v alginate and 6% w/v gelatin functionalized with fibronectin was produced using a custom-made bioreactor-based method. Different volumetric proportions of alginate and gelatin were tested (50/50, 70/30, and 90/10).

Multi-stage bioengineering of a layered oesophagus with in vitro expanded muscle and epithelial adult progenitors.

A tissue engineered oesophagus could overcome limitations associated with oesophageal substitution. Combining decellularized scaffolds with patient-derived cells shows promise for regeneration of tissue defects. In this proof-of-principle study, a two-stage approach for generation of a bio-artificial oesophageal graft addresses some major challenges in organ engineering, namely: (i) development of multi-strata tubular structures, (ii) appropriate re-population/maturation of constructs before transplantation, (iii) cryopreservation of bio-engineered organs and (iv) in vivo pre-vascularization.

Estimation of the physiological mechanical conditioning in vascular tissue engineering by a predictive fluid-structure interaction approach.

The in vitro replication of physiological mechanical conditioning through bioreactors plays a crucial role in the development of functional Small-Caliber Tissue-Engineered Blood Vessels. An in silico scaffold-specific model under pulsatile perfusion provided by a bioreactor was implemented using a fluid-structure interaction (FSI) approach for viscoelastic tubular scaffolds (e.g.

Alternating air-medium exposure in rotating bioreactors optimizes cell metabolism in 3D novel tubular scaffold polyurethane foams.

Background: In vitro dynamic culture conditions play a pivotal role in developing engineered tissue grafts, where the supply of oxygen and nutrients, and waste removal must be permitted within construct thickness. For tubular scaffolds, mass transfer is enhanced by introducing a convective flow through rotating bioreactors with positive effects on cell proliferation, scaffold colonization and extracellular matrix deposition. We characterized a novel polyurethane-based tubular scaffold and investigated the impact of 3 different culture configurations over cell behavior: dynamic (i) single-phase (medium) rotation and (ii) double-phase exposure (medium-air) rotation; static (iii) single-phase static culture as control.

Arterial Decellularized Scaffolds Produced Using an Innovative Automatic System.

There is still an unmet clinical need for small-caliber artery substitution. Decellularized scaffolds in tissue engineering represent a promising solution. We have developed an innovative system for the automatic decellularization of blood vessels, used to process pig arteries.

Cells and stimuli in small-caliber blood vessel tissue engineering.

The absence of successful solutions in treatments of small-caliber vessel diseases led to the Vascular Tissue Engineering approach to develop functional nonimmunogenic tissue engineered blood vessels. In this context, the choice of cells to be seeded and the microenvironment conditioning are pivotal. Biochemical and biomechanical stimuli seem to activate physiological regulatory pathways that induce the production of molecules and proteins stimulating stem cell differentiation toward vascular lineage and reproducing natural cross-talks among vascular cells to improve the maturation of tissue engineered blood vessels.

Skeletal muscle tissue engineering: strategies for volumetric constructs.

Skeletal muscle tissue is characterized by high metabolic requirements, defined structure and high regenerative potential. As such, it constitutes an appealing platform for tissue engineering to address volumetric defects, as proven by recent works in this field. Several issues common to all engineered constructs constrain the variety of tissues that can be realized in vitro, principal among them the lack of a vascular system and the absence of reliable cell sources; as it is, the only successful tissue engineering constructs are not characterized by active function, present limited cellular survival at implantation and possess low metabolic requirements.

Detergent-enzymatic decellularization of swine blood vessels: insight on mechanical properties for vascular tissue engineering.

Small caliber vessels substitutes still remain an unmet clinical need; few autologous substitutes are available, while synthetic grafts show insufficient patency in the long term. Decellularization is the complete removal of all cellular and nuclear matters from a tissue while leaving a preserved extracellular matrix representing a promising tool for the generation of acellular scaffolds for tissue engineering, already used for various tissues with positive outcomes. The aim of this work is to investigate the effect of a detergent-enzymatic decellularization protocol on swine arteries in terms of cell removal, extracellular matrix preservation, and mechanical properties.

Enhancing the biological performance of synthetic polymeric materials by decoration with engineered, decellularized extracellular matrix.

Materials based on synthetic polymers can be extensively tailored in their physical properties but often suffer from limited biological functionality. Here we tested the hypothesis that the biological performance of 3D synthetic polymer-based scaffolds can be enhanced by extracellular matrix (ECM) deposited by cells in vitro and subsequently decellularized. The hypothesis was tested in the context of bone graft substitutes, using polyesterurethane (PEU) foams and mineralized ECM laid by human mesenchymal stromal cells (hMSC).

A novel device for the automatic decellularization of biological tissues.

Objectives: Decellularized biological scaffolds represent a promising solution for tissue engineering. They offer a good substrate for cells in terms of biochemical composition, ultrastructure and mechanical properties without generating an immunogenic response. The aim of this study was to design and develop a device for the automatic decellularization of biological tissues to overcome manual operation limits, toward a good manufacturing practice-compliant process.

Trends in biomedical engineering: focus on Regenerative Medicine.

Regenerative medicine is a critical frontier in biomedical and clinical research. The major progresses in the last few years were driven by a strong clinical need which could benefit from regenerative medicine outcomes for the treatment of a large number of conditions including birth defects, degenerative and neoplastic diseases, and traumatic injuries. Regenerative medicine applies the principles of engineering and life sciences to enhance the comprehension of the fundamental biological mechanisms underlying the structure-function relationships in physiologic and pathologic tissues and to accomplish alternative strategies for developing in vitro biological substitutes which are able to restore, maintain, or improve tissue, and organ function.

Cyclic mechanical stimulation favors myosin heavy chain accumulation in engineered skeletal muscle constructs.

Purpose: Since stretching plays a key role in skeletal muscle tissue development in vivo, by making use of an innovative bioreactor and a biodegradable microfibrous scaffold (DegraPol(R)) previously developed by our group, we aimed to investigate the effect of mechanical conditioning on the development of skeletal muscle engineered constructs, obtained by seeding and culturing murine skeletal muscle cells on electrospun membranes.

Methods: Following 5 days of static culture, skeletal muscle constructs were transferred into the bioreactor and further cultured for 13 days, while experiencing a stretching pattern adapted from the literature to resemble mouse development and growth. Sample withdrawal occurred at the onset of cyclic stretching and after 7 and 10 days.

Tissue engineering toward organ replacement: a promising approach in airway transplant.

Autologous tissue transfer, allografts and prosthetic replacements have so far failed to offer functional solutions for the treatment of long circumferential tracheal defects. Because of the shortcomings related with these strategies, interest has turned increasingly to the field of tissue engineering which applies the principles of engineering and life sciences in an effort to develop in vitro biological substitutes able to restore, maintain, or improve tissue and organ function. The advances in this field during the past decade have thus provided a new attractive approach toward the concept of functional substitutes and may represent an alternative to the shortage of suitable grafts for reconstructive airway surgery.

Both epithelial cells and mesenchymal stem cell-derived chondrocytes contribute to the survival of tissue-engineered airway transplants in pigs.

Objective: We sought to determine the relative contributions of epithelial cells and mesenchymal stem cell-derived chondrocytes to the survival of tissue-engineered airway transplants in pigs.

Methods: Nonimmunogenic tracheal matrices were obtained by using a detergent-enzymatic method. Major histocompatibility complex-unmatched animals (weighing 65 +/- 4 kg) were divided into 4 groups (each n = 5), and 6 cm of their tracheas were orthotopically replaced with decellularized matrix only (group I), decellularized matrix with autologous mesenchymal stem cell-derived chondrocytes externally (group II), decellularized matrix with autologous epithelial cells internally (group III), or decellularized matrix with both cell types (group IV).

Structural and morphologic evaluation of a novel detergent-enzymatic tissue-engineered tracheal tubular matrix.

Objective: We sought to bioengineer a nonimmunogenic tracheal tubular matrix of 6 cm in length and test its structural, functional, and immunologic properties in vitro and in vivo.

Methods: Twelve-centimeter tracheal segments were harvested from Yorkshire boars. Half of each segment was subjected to a detergent-enzymatic method (containing sodium deoxycholate/DNase lavations) of decellularization for as many cycles as needed, and the other half was stored in phosphate-buffered saline at 4 degrees C as a control.

A double-chamber rotating bioreactor for the development of tissue-engineered hollow organs: from concept to clinical trial.

Cell and tissue engineering are now being translated into clinical organ replacement, offering alternatives to fight morbidity, organ shortages and ethico-social problems associated with allotransplantation. Central to the recent first successful use of stem cells to create an organ replacement in man was our development of a bioreactor environment. Critical design features were the abilities to drive the growth of two different cell types, to support 3D maturation, to maintain biomechanical and biological properties and to provide appropriate hydrodynamic stimuli and adequate mass transport.

Clinical transplantation of a tissue-engineered airway.

Background: The loss of a normal airway is devastating. Attempts to replace large airways have met with serious problems. Prerequisites for a tissue-engineered replacement are a suitable matrix, cells, ideal mechanical properties, and the absence of antigenicity.

Rotating versus perfusion bioreactor for the culture of engineered vascular constructs based on hyaluronic acid.

It is generally accepted that dynamic culture conditions are required for vascular tissue engineering. We compared the effects of two dynamic culture systems, a perfusion and a rotating bioreactor, using tubular constructs based on hyaluronic acid seeded with porcine aortic smooth muscle cells (SMC), that we recently showed to be adequate for the generation of vascular tissue. In perfused constructs mechanical stimulation importantly affected cell morphology, increased the incidence of cell proliferation and reduced apoptosis.

Prefabricated tracheal prosthesis with partial biodegradable materials: a surgical and tissue engineering evaluation in vivo.

Large and circumferential tracheal defects remain at this time an unsolved problem for reconstructive surgery. Many types of prosthetic and tissue grafts have been used but with limited comfortable results. Major complications are anastomotic dehiscence, graft ischemia and stenosis due to the poor vascularization of the prosthetic complex.