Tissue Bioengineering Research Articles

Titanium Biohybrid Middle Ear Prostheses: A Preliminary In Vitro Study.

Ossiculoplasty is a surgical operation performed to restore auditory transmission through the reconstruction of the ossicular chain using prosthetics. Tissue bioengineering has assumed a pivotal role in implementing alternatives to conventional ossicular middle ear replacement prostheses, to overcome extrusion while preserving acoustic properties. This in vitro study aims to explore, for the first time in current literature, the feasibility of a biohybrid middle ear prosthesis, composed of titanium surrounded by a bone extracellular matrix as bio-coating. We have hereby studied the adhesion and proliferation of human adipose-derived mesenchymal stem cells (hASC) on titanium scaffolds in vitro. Moreover, we identified the osteogenic differentiation of hASC using an immunofluorescence assay to analyze osteoblasts' gene expression profiles (Alp, Runx2, Col1a1, Osx, and Bglap), and we counted the presence of collagen as a marker of hASC's ability to secrete an extracellular matrix. We utilized scanning electron microscopy to evaluate the presence of an extracellular matrix on the scaffolds. Our preliminary data demonstrated the titanium's ability to support human adipose-derived mesenchymal stem cell colonization, proliferation, and osteoblastic differentiation, in order to obtain a biohybrid device. Our experience seems encouraging; thus, we advocate for further in vivo research to corroborate our results regarding bone transplantation.

Freeze-Dried Mesenchymal Stem Cells: From Bench to Bedside. Review.

This review describes the freeze-dried mesenchymal stem cells (MSCs) and their ability to restore damaged tissues and organs. An analysis of the literature shows that after the lyophilization MSCs retain >80% of paracrine factors and that the mechanism of their action on the restoration of damaged tissues and organs is similar to the mechanism of action of paracrine factors in fresh and cryopreserved mesenchymal stem cells. Based on the own materials, the use of paracrine factors of freeze-dried MSCs in vivo and in vitro for the treatment of various diseases of organs and tissues has shown to be effective. The study also discusses about the advantages and disadvantages of freeze-dried MSCs versus cryopreserved MSCs. However, for the effective use of freeze-dried MSCs in clinical practice, a more detailed study of the mechanism of interaction of paracrine factors of freeze-dried MSCs with target cells and tissues is required. It is also necessary to identify possible other specific paracrine factors of freeze-dried MSCs. In addition, develop new therapeutic strategies for the use of freeze-dried MSCs in regenerative medicine and tissue bioengineering.

The Use of Shells of Marine Molluscs in Spanish Ethnomedicine: A Historical Approach and Present and Future Perspectives.

Since ancient times, the shells of marine molluscs have been used as a therapeutic and/or prophylactic resource. In Spain, they were part of practical guides for doctors or pharmacists until the 19th century. In general, seashells were prepared by dissolving in vinegar and were part of plasters or powders used as toothpaste, or to treat dyspepsia, heartburn and leprosy. Thus, the nacre or mother-of-pearl of various molluscs was regularly used in the Royal Colleges of Surgery and in hospitals during the times of the Cortes of Cadiz, as a medicine in galenic preparations based on powders. In contemporary Spanish ethnomedicine, seashells, with a high symbolic value, have been used as an amulet to prevent cracks in the breasts and promote their development during lactation, to avoid teething pain in young children, to eliminate stains on the face or to cure erysipelas. But, as in other countries, products derived from seashells have also been empirically applied. The two resources used traditionally have been the cuttlebone, the internal shell of cuttlefish and the nacre obtained from the external shells of some species. Cuttlebone, dried and pulverised, has been applied externally to cure corneal leukoma and in dental hygiene. In the case of nacre, a distinction must be made between chemical and physical remedies. Certain seashells, macerated in lemon juice, were used in coastal areas to remove spots on the face during postpartum. However, the most common practice in Spain mainland was to dissolve mother-of-pearl buttons in lemon juice (or vinegar). The substance thus obtained has been used to treat different dermatological conditions of the face (chloasma, acne), as well as to eliminate freckles. For the extraction of foreign bodies in the eyes, a very widespread traditional remedy has been to introduce small mother-of-pearl buttons under the lid. These popular remedies and practices are compared with those collected in classic works of medicine throughout history, and data on the pharmacological activity and pharmaceutical applications of the products used are provided. The use of cuttlebone powders is supported by different works on anti-inflammatory, immune-modulatory and/or wound healing properties. Nacre powder has been used in traditional medicines to treat palpitations, convulsions or epilepsy. As sedation and a tranquilisation agent, nacre is an interesting source for further drug development. Likewise, nacre is a biomaterial for orthopaedic and other tissue bioengineering applications. This article is a historical, cultural and anthropological view that can open new epistemological paths in marine-derived product research.

Evaluation of human amnion denuded derived mesenchymal stem cell on 3D porous hydroxyapatite composite scaffolds for osteogenic differentiation: Prolonged in vitro study

Recent studies using composite porous scaffolds have globally demonstrated the biocompatibility of mesenchymal stem cell sources. It is especially important in hard tissue bioengineering due to its desirable features and stemness effectivity. This study has emphasized primarily the evaluation of the morphological aspects of human amnion-denuded derived mesenchymal stem cells (hAMMSC) in combination with the fabrication of three-dimensional (3D) porous hydroxyapatite (Hap) composite scaffolds for bone tissue engineering based on the principal component of bone mineralization. We presented a novel combination of hAMMSC and nano-crystalline powder hydroxyapatite/bioactive glass (Hap/BG) composite scaffolds fabricated through the hydrothermal method via a novel formulation method from a previous study of stem cell in vitro prolonged culture. The 3D porous scaffold, 6 mm in size, was fabricated from 70 nm nanocrystalline powder and interacted with hAMMSC cultured in osteo-inductive conditions for 30 days. The characterization of 3D porous scaffolds was analyzed via Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) to explore the particle structure, morphology, bioactivity, and porosity of the composite powder and scaffolds in contact with hAMMSCs culture. Furthermore, biocompatibility was assessed using the PrestoBlueTM viability assay and scanning electron microscopy observation (SEM), which revealed the attachment, morphology, and spreading of hAMMSCs on the 3D porous scaffolds of Hap/BG by showing spindle-like morphology and forming the spreading filopodia bridge-like structure within the scaffolds. Subsequently, the secondary objective is the characterization of human AMMSC differentiation capacity assessed by early osteoblast differentiation and mineralization behaviour investigated by early detected assay via alkaline phosphatase activity (ALP) activity marker and energy dispersive X-ray (EDX) analysis simultaneously of the mineralization within bone matrix elements. It was comparatively evaluated via ALP and EDX for calcium quantification elements. Immunomodulatory properties were analyzed via ELISA kits. In conclusion, our findings indicate that 3D porous scaffolds made of Hap/BG composites could be great candidates for future regenerative medicine applications due to their support towards stem cell growth and enhancement of bone cell capacity.

Utilization of a Decellularized Skin Scaffold for Repair of a Cleft Palate in a Dog: A Case Report.

Cleft palates are oral deformities that mostly affect puppies. They are frequently extensive and characterized by bone and palatal mucosa malformation. This deformity is a serious condition that may result in the death of the dog, therefore surgical treatment is recommended. Tissue bioengineering has emerged as a valuable option to treat cleft palates by applying acellular biological scaffolds as grafts. This case report proposed a new approach for surgical correction of canine cleft palate through a grafting technique using a decellularized scaffold. A decellularized portion of skin was implanted to correct a large cleft palate in a 3-month-old female Pug dog. The skin fragment was obtained from a dog cadaver and a decellularization protocol was performed. Under general anesthesia, a bilateral mucoperiosteal separation of the entire length of cleft margins was performed, and the scaffold was then positioned between the tissue and the bone palate. The interaction of the grafted scaffold with the oral mucosa and palatine layers resulted in total cleft closure, without postsurgical rejection or infection, indicating the applicability of this technique in dog's cleft palate correction. This is the first reported case demonstrating this new technique, which resulted in full cleft closure and healing.

Focal adhesion kinase (FAK): its structure, characteristics, and signaling in skeletal system

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase and distributes important regulatory functions in skeletal system. Mesenchymal stem cell (MSC) possesses significant migration and differentiation capacity, is an important source of distinctive bone cells production and a prominent bone development pathway. MSC has a wide range of applications in tissue bioengineering and regenerative medicine, and is frequently employed for hematopoietic support, immunological regulation, and defect repair, although current research is insufficient. FAK has been identified to cross-link with many other keys signaling pathways in bone biology and is considered as a fundamental “crossroad” on the signal transduction pathway and a “node” in the signal network to mediate MSC lineage development in skeletal system. In this review, we summarized the structure, characteristics, cellular signaling, and the interactions of FAK with other signaling pathways in the skeletal system. The discovery of FAK and its mediated molecules will lead to a new knowledge of bone development and bone construction as well as considerable potential for therapeutic use in the treatment of bone-related disorders such as osteoporosis, osteoarthritis, and osteosarcoma.

Photosynthetic microorganisms for the oxygenation of advanced 3D bioprinted tissues.

3D bioprinting technology has emerged as a tool that promises to revolutionize the biomedical field, including tissue engineering and regeneration. Despite major technological advancements, several challenges remain to be solved before 3D bioprinted tissues could be fully translated from the bench to the bedside. As oxygen plays a key role in aerobic metabolism, which allows energy production in the mitochondria; as a consequence, the lack of tissue oxygenation is one of the main limitations of current bioprinted tissues and organs. In order to improve tissue oxygenation, recent approaches have been established for a broad range of clinical applications, with some already applied using 3D bioprinting technologies. Among them, the incorporation of photosynthetic microorganisms, such as microalgae and cyanobacteria, is a promising approach that has been recently explored to generate chimerical plant-animal tissues where, upon light exposure, oxygen can be produced and released in a localized and controlled manner. This review will briefly summarize the state-of-the-art approaches to improve tissue oxygenation, as well as studies describing the use of photosynthetic microorganisms in 3D bioprinting technologies. STATEMENT OF SIGNIFICANCE: 3D bioprinting technology has emerged as a tool for the generation of viable and functional tissues for direct in vitro and in vivo applications, including disease modeling, drug discovery and regenerative medicine. Despite the latest advancements in this field, suboptimal oxygen delivery to cells before, during and after the bioprinting process limits their viability within 3D bioprinted tissues. This review article first highlights state-of-the-art approaches used to improve oxygen delivery in bioengineered tissues to overcome this challenge. Then, it focuses on the emerging roles played by photosynthetic organisms as novel biomaterials for bioink generation. Finally, it provides considerations around current challenges and novel potential opportunities for their use in bioinks, by comparing latest published studies using algae for 3D bioprinting.

Microgel Particle Collision with Smooth and Nanofiber Hydrophobic Surfaces during Three-Dimensional Printing of a Biopolymer Layer.

The impact of microgel particles onto a wall represents an elementary process that determines the one-stage production of a biopolymer layer on a nanofiber scaffold in the framework of tissue bioengineering. The formation of a microgel layer is experimentally examined on a hydrophobic uniform surface and a nonwoven polymer membrane made of vinylidene fluoride-tetrafluoroethylene copolymer. In-air microfluidics methods, namely, an external vibration disturbance on the microflow of a cross-linkable biopolymer, make it possible to form the microstructures of "beads-on-thread" with a uniform distance between microgel particles of identical size (340-480 μm, depending on the sample). The successive particle-surface and particle-particle collisions are explored to develop the concept of technology for depositing microgel particles on surfaces for mobile one-stage production of microgel layers with a thickness of one and two particles, respectively. A physical model of successive particle-surface and particle-particle interactions is proposed. Empirical expressions are derived for predicting the diameters of maximum spreading (deformation) and the minimum heights of microgel particles on smooth and nanofiber surfaces, as well as in particle-particle collisions using a dimensionless criterion of gelation degree. The effect of microgel viscosity and fluidity on the maximum particle spreading during successive particle-surface and particle-particle collisions is elucidated. The consistent findings have made it possible to develop a predictive method for determining the growth dynamics of microgel layer area with a thickness of one or two particles on a nanofiber scaffold within a few seconds. The specific behavior of a microgel with a given gelation degree is simulated to produce a layer.

Systematic discovery of transcription factors that improve hPSC-derived cardiomyocyte maturation via temporal analysis of bioengineered cardiac tissues.

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) have the potential to become powerful tools for disease modeling, drug testing, and transplantation; however, their immaturity limits their applications. Transcription factor (TF) overexpression can improve hPSC-CM maturity, but identifying these TFs has been elusive. Toward this, we establish here an experimental framework for systematic identification of maturation enhancing factors. Specifically, we performed temporal transcriptome RNAseq analyses of progressively matured hPSC-derived cardiomyocytes across 2D and 3D differentiation systems and further compared these bioengineered tissues to native fetal and adult-derived tissues. These analyses revealed 22 TFs whose expression did not increase in 2D differentiation systems but progressively increased in 3D culture systems and adult mature cell types. Individually overexpressing each of these TFs in immature hPSC-CMs identified five TFs (KLF15, ZBTB20, ESRRA, HOPX, and CAMTA2) as regulators of calcium handling, metabolic function, and hypertrophy. Notably, the combinatorial overexpression of KLF15, ESRRA, and HOPX improved all three maturation parameters simultaneously. Taken together, we introduce a new TF cocktail that can be used in solo or in conjunction with other strategies to improve hPSC-CM maturation and anticipate that our generalizable methodology can also be implemented to identify maturation-associated TFs for other stem cell progenies.

Jammed microgel growth medium prepared by flash-solidification of agarose for 3D cell culture and 3D bioprinting

Although cells cultured in three-dimensional (3D) platforms are proven to be beneficial for studying cellular behavior in settings similar to their physiological state, due to the ease, convenience, and accessibility, traditional 2D culturing approaches are widely adopted. Jammed microgels are a promising class of biomaterials extensively suited for 3D cell culture, tissue bioengineering, and 3D bioprinting. However, existing protocols for fabricating such microgels either involve complex synthesis steps, long preparation times, or polyelectrolyte hydrogel formulations that sequester ionic elements from the cell growth media. Hence, there is an unmet need for a broadly biocompatible, high-throughput, and easily accessible manufacturing process. We address these demands by introducing a rapid, high-throughput, and remarkably straightforward method to synthesize jammed microgels composed of flash-solidified agarose granules directly prepared in a culture medium of choice. Our jammed growth media are optically transparent, porous, yield stress materials with tunable stiffness and self-healing properties, which makes them ideal for 3D cell culture as well as 3D bioprinting. The charge-neutral and inert nature of agarose make them suitable for culturing various cell types and species, the specific growth media for which do not alter the chemistry of the manufacturing process. Unlike several existing 3D platforms, these microgels are readily compatible with standard techniques such as absorbance-based growth assays, antibiotic selection, RNA extraction, and live cell encapsulation. In effect, we present a versatile, highly accessible, inexpensive, and easily adoptable biomaterial for 3D cell culture and 3D bioprinting. We envision their widespread application not just in routine laboratory settings but also in designing multicellular tissue mimics and dynamic co-culture models of physiological niches.

Isolation and primary culture of human abdominal aorta smooth muscle cells from brain-dead donors: an experimental model for vascular diseases.

Primary cell cultures are essential tools for elucidating the physiopathological mechanisms of the cardiovascular system. Therefore, a primary culture growth protocol of cardiovascular smooth muscle cells (VSMCs) obtained from human abdominal aortas was standardized. Ten abdominal aorta samples were obtained from patients diagnosed with brain death who were organ and tissue donors with family consent. After surgical ablation to capture the aorta, the aortic tissue was removed, immersed in a Custodiol® solution, and kept between 2 and 8°C. In the laboratory, in a sterile environment, the tissue was fragmented and incubated in culture plates containing an enriched culture medium (DMEM/G/10% fetal bovine serum, L-glutamine, antibiotics and antifungals) and kept in an oven at 37°C and 5% CO2. The aorta was removed after 24h of incubation, and the culture medium was changed every six days for twenty days. Cell growth was confirmed through morphological analysis using an inverted optical microscope (Nikon®) and immunofluorescence for smooth muscle alpha-actin and nuclei. The development of the VSMCs was observed, and from the twelfth day, differentiation, long cytoplasmic projections, and adjacent cell connections occurred. On the twentieth day, the morphology of the VSMCs was confirmed by actin fiber immunofluorescence, which is a typical characteristic of VSMCs. The standardization allowed VSMC growth and the replicability of the in vitro test, providing a protocol that mimics natural physiological environments for a better understanding of the cardiovascular system. Its use is intended for investigation, tissue bioengineering, and pharmacological treatments.

Bioengineered tissue and cell therapy products are efficiently cryopreserved with pathogen-inactivated human platelet lysate-based solutions

BackgroundThere remains much interest in improving cryopreservation techniques for advanced therapy medicinal products (ATMPs). Recently, human platelet lysate (hPL) has emerged as a promising candidate to replace fetal bovine serum (FBS) as a xeno-free culture supplement for the expansion of human cell therapy products. Whether hPL can also substitute for FBS in cryopreservation procedures remains poorly studied. Here, we evaluated several cryoprotective formulations based on a proprietary hPL for the cryopreservation of bioengineered tissues and cell therapy products.MethodsWe tested different xenogeneic-free, pathogen-inactivated hPL (ihPL)- and non-inactivated-based formulations for cryopreserving bioengineered tissue (cellularized nanostructured fibrin agarose hydrogels (NFAHs)) and common cell therapy products including bone marrow-derived mesenchymal stromal cells (BM-MSCs), human dermal fibroblasts (FBs) and neural stem cells (NSCs). To assess the tissue and cellular properties post-thaw of NFAHs, we analyzed their cell viability, identity and structural and biomechanical properties. Also, we evaluated cell viability, recovery and identity post-thaw in cryopreserved cells. Further properties like immunomodulation, apoptosis and cell proliferation were assessed in certain cell types. Additionally, we examined the stability of the formulated solutions. The formulations are under a bidding process with MD Bioproducts (Zurich, Switzerland) and are proprietary.ResultsAmongst the tissue-specific solutions, Ti5 (low-DMSO and ihPL-based) preserved the viability and the phenotype of embedded cells in NFAHs and preserved the matrix integrity and biomechanical properties similar to those of the standard cryopreservation solution (70% DMEM + 20% FBS + 10% DMSO). All solutions were stable at − 20 °C for at least 3 months. Regarding cell-specific solutions, CeA maintained the viability of all cell types > 80%, preserved the immunomodulatory properties of BM-MSCs and promoted good recovery post-thaw. Besides, both tested solutions were stable at − 20 °C for 18 months. Finally, we established that there is a 3-h window in which thawed NFAHs and FBs maintain optimum viability immersed in the formulated solutions and at least 2 h for BM-MSCs.ConclusionsOur results show that pathogen-inactivated solutions Ti5 allocated for bioengineered tissues and CeA allocated for cells are efficient and safe candidates to cryopreserve ATMPs and offer a xenogeneic-free and low-DMSO alternative to commercially available cryoprotective solutions.

CPD: Developments in corneal transplants

Dr Douglas Clarkson reviews the latest developments in corneal transplantation and corneal tissue bioengineering (C104966, suitable for logging as one provider-led distance learning CPD point for optometrists and dispensing opticians)

Biomaterials for Testicular Bioengineering: How far have we come and where do we have to go?

Traditional therapeutic interventions aim to restore male fertile potential or preserve sperm viability in severe cases, such as semen cryopreservation, testicular tissue, germ cell transplantation and testicular graft. However, these techniques demonstrate several methodological, clinical, and biological limitations, that impact in their results. In this scenario, reproductive medicine has sought biotechnological alternatives applied for infertility treatment, or to improve gamete preservation and thus increase reproductive rates in vitro and in vivo. One of the main approaches employed is the biomimetic testicular tissue reconstruction, which uses tissue-engineering principles and methodologies. This strategy pursues to mimic the testicular microenvironment, simulating physiological conditions. Such approach allows male gametes maintenance in culture or produce viable grafts that can be transplanted and restore reproductive functions. In this context, the application of several biomaterials have been proposed to be used in artificial biological systems. From synthetic polymers to decellularized matrixes, each biomaterial has advantages and disadvantages regarding its application in cell culture and tissue reconstruction. Therefore, the present review aims to list the progress that has been made and the continued challenges facing testicular regenerative medicine and the preservation of male reproductive capacity, based on the development of tissue bioengineering approaches for testicular tissue microenvironment reconstruction.

Current Trends on Bioengineering Approaches for Ovarian Microenvironment Reconstruction.

Ovarian tissue has a unique microarchitecture and a complex cellular and molecular dynamics that are essential for follicular survival and development. Due to this great complexity, several factors may lead to ovarian insufficiency, and therefore to systemic metabolic disorders and female infertility. Techniques currently used in the reproductive clinic such as oocyte cryopreservation or even ovarian tissue transplant, although effective, have several limitations, which impair their wide application. In this scenario, mimetic ovarian tissue reconstruction comes as an innovative alternative to develop new methodologies for germ cells preservation and ovarian functions restoration. The ovarian extracellular matrix (ECM) is crucial for oocyte viability maintenance, once it acts actively in folliculogenesis. One of the key components of ovarian bioengineering is biomaterials application that mimics ECM and provides conditions for cell anchorage, proliferation, and differentiation. Therefore, this review aims at describing ovarian tissue engineering approaches and listing the main limitations of current methods for preservation and reestablishment of ovarian fertility. In addition, we describe the main elements that structure this study field, highlighting the main advances and the challenges to overcome to develop innovative methodologies to be applied in reproductive medicine. Impact Statement This review presents the main advances in the application of tissue bioengineering in the ovarian tissue reconstruction to develop innovative solutions for ovarian fertility reestablishment.

Hydroxyapatite, alginate and gelatin composites used for bone regeneration: a systematic review

Aim: to investigate and describe, through a systematic review, the biological behavior and osteogenic potential of composite biomaterials containing hydroxyapatite (HA), alginate and gelatin, in different associations, after in vivo implantation. Materials and Methods: for the search and selection of articles, the Medical Literature Analysis and Retrieval System Online (PubMed/MEDLINE) and Scientific Electronic Library Online (SciELO) databases were used, published between 2012 and 2022, using the descriptors: “bone regeneration”; “biocompatible material”; “durapatite”; “alginate”; “gelatin”. Initially, an association was made with the Boolean operator "OR" between the descriptors and their respective entry terms, considering that the MeSH and DeCS platforms use different terms to refer to the same keywords. Subsequently, the "AND" operator was used in nine associations between the descriptors. Results: during the searches, 1939 articles were located. After using the inclusion and exclusion criteria, 16 studies were included in the review. The main themes found in the searches were: HA and Alginate; HA and Gelatin; HA, Alginate and Zinc; HA, Gelatin and mesenchymal cells; HA, Alginate and Chitosan; HA, Alginate and Silk Fibrin; HA, Gelatin and titanium dioxide; HA, Alginate and Gelatin. It was observed that HA, when associated with alginate or gelatin, has improved its osteogenic properties. Final Considerations: HA composites associated with alginate and gelatin provide a range of applications and promising strategies applied to bone repair. Studies have shown that these composites have great potential for application in Bone Tissue Bioengineering.

A novel anisotropic stress‐driven model for bioengineered tissues accounting for remodeling and reorientation based on homeostatic surfaces

AbstractA co‐rotated formulation of the intermediate configuration is derived in a thermodynamically consistent manner. As a result of this formulation, algorithmic differentiation (AD) and the equations of the material model can be combined directly, i.e., the equations can be implemented into the AD tool and the corresponding derivatives can be calculated using AD. This is not possible when the equations are given in terms of the intermediate configuration, since the multiplicative decomposition suffers from an inherent rotational non‐uniqueness. Moreover, a novel stress‐driven kinematic growth model is presented that takes homeostasis and fiber reorientation into account and is based on the co‐rotated formulation. A numerical example reveals the promising potential of both the co‐rotated formulation and the stress‐driven growth model.

Effect of Electrospun PLGA/Collagen Scaffolds on Cell Adhesion, Viability, and Collagen Release: Potential Applications in Tissue Engineering

The development of scaffolding obtained by electrospinning is widely used in tissue engineering due to porous and fibrous structures that can mimic the extracellular matrix. In this study, poly (lactic-co-glycolic acid) (PLGA)/collagen fibers were fabricated by electrospinning method and then evaluated in the cell adhesion and viability of human cervical carcinoma HeLa and NIH-3T3 fibroblast for potential application in tissue regeneration. Additionally, collagen release was assessed in NIH-3T3 fibroblasts. The fibrillar morphology of PLGA/collagen fibers was verified by scanning electron microscopy. The fiber diameter decreased in the fibers (PLGA/collagen) up to 0.6 µm. FT-IR spectroscopy and thermal analysis confirmed that both the electrospinning process and the blend with PLGA give structural stability to collagen. Incorporating collagen in the PLGA matrix promotes an increase in the material's rigidity, showing an increase in the elastic modulus (38%) and tensile strength (70%) compared to pure PLGA. PLGA and PLGA/collagen fibers were found to provide a suitable environment for the adhesion and growth of HeLa and NIH-3T3 cell lines as well as stimulate collagen release. We conclude that these scaffolds could be very effective as biocompatible materials for extracellular matrix regeneration, suggesting their potential applications in tissue bioengineering.

A novel extrusion-based 3D bioprinting system for skeletal muscle tissue engineering

Three-dimensional (3D) bioprinting is an emerging technology, which turned out to be an optimal tool for tissue engineering approaches. To date, different printing systems have been developed. Among them, the extrusion-based approach demonstrated to be the most suitable for skeletal muscle tissue engineering, due to its ability to produce and deposit printing fibers in a parallel pattern that well mimic the native skeletal muscle tissue architecture. In tissue bioengineering, a key role is played by biomaterials, which must possess the key requisite of ‘printability’. Nevertheless, this feature is not often well correlated with cell requirements, such as motives for cellular adhesion and/or absorbability. To overcome this hurdle, several efforts have been made to obtain an effective bioink by combining two different biomaterials in order to reach a good printability besides a suitable biological activity. However, despite being efficient, this strategy reveals several outcomes limitations. We report here the development and characterization of a novel extrusion-based 3D bioprinting system, and its application for correction of volumetric muscle loss (VML) injury in a mouse model. The developed bioprinting system is based on the use of PEG-Fibrinogen, a unique biomaterial with excellent biocompatibility, well-suited for skeletal muscle tissue engineering. With this approach, we obtained highly organized 3D constructs, in which murine muscle progenitors were able to differentiate into muscle fibers arranged in aligned bundles and capable of spontaneously contracting when cultured in vitro. Furthermore, to evaluate the potential of the developed system in future regenerative medicine applications, bioprinted constructs laden with either murine or human muscle progenitors were transplanted to regenerate the Tibialis Anterior muscle of a VML murine model, one month after grafting.

Application of Nano-HydroxyApatite (n-HAp) for Wound Healing and Tissue Bioengineering

PRéCIS- A wound, or tissue defect can be defined as a disruption in the normal structure and function that occurs due to internal or external injury. In tissue bioengineering, natural hemostasis, and the inflammatory phase stand at the beginning of the wound and defect healing cascade. Briefly, the restorative, regenerative or reparative response to tissue injury is governed/driven by resident and circulating cells, homing to the injury site that release signals (soluble mediators) generated from the extracellular matrix. For bone defects, optimal healing can be simply classified as either primary (1o) or secondary (2o). It undergoes acascade of complex, orderly, and predictable events, that include four/five over-lapping phases: hemostasis/haematoma formation, inflammation, proliferation, callus formation (or not), and remodeling (Haversian/osteonal bone remodelling). Herein, the bone healing type is dependent on the removal of a fracture haematoma and the fixation (stabilization) strategy performed. For example, optimal stability results in 1o bone healing, with no callus formation, normal bone architecture and functional integrity restored within 3 months. On the other hand, in 2o healing, where fixation is not done, fracture haematoma, callus formation and healing via endochondral ossification ensues. Despite limitations, the main alternative for damaged or lost bone tissue replacement, restoration, regeneration, reconstruction, or repair is the autogenous bone graft, to date.