Vascularization strategies for tissue engineers

Advances in oxygen-releasing matrices for regenerative engineering applications

In recent years, the effects of hypoxia on tissue repair have received wider attention with the deepening of tissue engineering research. Various oxygen supply strategies have wider applications in the field of tissue repair. Currently, commonly used methods of oxygen supply for defective tissues include hyperbaric oxygen (HBO) and oxygen-releasing materials. Between them, oxygen-releasing materials continuously and efficiently release oxygen from within the defective tissue. Compared with HBO, which may cause oxidative stress in healthy tissues, supplying oxygen via oxygen-releasing materials is safer because of their oxygen-releasing in situ and specific oxygen supply characteristics. However, there still exist some problems in the study of oxygen-releasing materials, such as cytotoxicity and the shortage of oxygen-releasing time. The current reviews on oxygen-releasing materials mostly elaborate on the principles of oxygen-releasing materials and lack a review of their preparation methods and applications. In this paper, different types of oxygen-releasing materials, such as hydrogels, microspheres, and layers, are reviewed concerning their applications, structures, current development status, and challenges.

Innovations in 3D ovarian and follicle engineering for fertility preservation and restoration

In-vitro maturation (IVM) is the process of cultivating early-stage follicles from the primordial to the antral stage and facilitating the maturation of oocytes outside the body within a supportive environment. This intricate procedure requires the careful coordination of various factors to replicate the natural ovarian conditions. Advanced techniques for IVM are designed to mimic the natural ovarian environment and enhance the development of follicles. Three-dimensional (3D) culture systems provide a more biologically relevant setting for follicle growth compared to traditional two-dimensional (2D) cultures. Traditional culture systems, often fail to support the complex process of follicle development effectively. However, modern engineered reproductive tissues and culture systems are making it possible to create increasingly physiological in-vitro models of folliculogenesis. These innovative methods are enabling researchers and clinicians to better replicate the dynamic and supportive environment of the ovary, thereby improving the outcomes of IVM offering new hope for fertility preservation and treatment. This paper focuses on the routine 3D culture, and innovative 3D culture of ovary and follicles, including a tissue engineering scaffolds, microfluidic (dynamic) culture system, organ-on-chip models, EVATAR system, from a clinical perspective to determine the most effective approach for achieving in-vitro maturation of follicles. These techniques provide critical support for ovarian function in various ovarian-associated disorders, including primary ovarian insufficiency (POI), premature ovarian failure (POF), ovarian cancer, and age-related infertility.

Vaginal reconstruction with a double-sided biomembrane-a preclinical experimental study on large animals

Tissue engineering techniques bring the promise of vaginal reconstruction with low invasiveness and fewer complications. However, existing biomaterial scaffolds remain limited in efficient vaginal recovery, focusing only on regenerating an epithelial layer, but muscle layers are missing or abnormal. The lack of a multi-tissue hierarchical structure in the reconstructed vagina leads to shrinking, stenosis, and fibrosis. Here, an acellular matrix named a double-sided biomembrane (DBM) is demonstrated for vaginal recovery. The regeneration of epithelial and muscle layers is achieved simultaneously since the smooth side of the DBM is helpful for guiding epithelial cell growth, while its loose and porous side guides muscle cell growth. In addition, the DBM demonstrates excellent mechanical properties similar to vaginal tissue, and hydrophilicity. Therefore, neovaginas were observed in the fourth and twelfth weeks after DBMs were transplanted to repair full-thickness vaginal defects (4 cm) that we established in large animals. The DBMs can effectively promote rapid epithelialization, the formation of large muscle bundles, higher rates of angiogenesis, and the restoration of physiological function in a neovagina. That is, the injured vagina achieves nearly complete recovery in anatomy and function, similar to a normal vagina. These preclinical results indicate that the DBM has prospects for vaginal injury repair.

Improving the 3D Printability of Sugar Glass to Engineer Sacrificial Vascular Templates

A prominent obstacle in scaling up tissue engineering technologies for human applications is engineering an adequate supply of oxygen and nutrients throughout artificial tissues. Sugar glass has emerged as a promising 3D-printable, sacrificial material that can be used to embed perfusable networks within cell-laden matrices to improve mass transfer. To characterize and optimize a previously published sugar ink, we investigated the effects of sucrose, glucose, and dextran concentration on the glass transition temperature (Tg), printability, and stability of 3D-printed sugar glass constructs. We identified a sucrose ink formulation with a significantly higher Tg (40.0 ± 0.9°C) than the original formulation (sucrose-glucose blend, Tg = 26.2 ± 0.4°C), which demonstrated a pronounced improvement in printability, resistance to bending, and final print stability, all without changing dissolution kinetics and decomposition temperature. This formulation allowed printing of 10-cm-long horizontal cantilever filaments, which can enable the printing of complex vascular segments along the x-, y-, and z-axes without the need for supporting structures. Vascular templates with a single inlet and outlet branching into nine channels were 3D printed using the improved formulation and subsequently used to generate perfusable alginate constructs. The printed lattice showed high fidelity with respect to the input geometry, although with some channel deformation after alginate casting and gelation-likely due to alginate swelling. Compared with avascular controls, no significant acute cytotoxicity was noted when casting pancreatic beta cell-laden alginate constructs around improved ink filaments, whereas a significant decrease in cell viability was observed with the original ink. The improved formulation lends more flexibility to sugar glass 3D printing by facilitating the fabrication of larger, more complex, and more stable sacrificial networks. Rigorous characterization and optimization methods for improving sacrificial inks may facilitate the fabrication of functional cellular constructs for tissue engineering, cellular biology, and other biomedical applications.

Construction of a vascularized fascia-prosthesis compound model with axial pedicle for ear reconstruction surgery

Background: To design a vascular pedicled fascia-prosthesis compound model that can be used for ear reconstruction surgery. Methods: A vascularized tissue engineering chamber model was constructed in New Zealand rabbits, and fresh tissues were obtained after 4 weeks. The histomorphology and vascularization of the newly born tissue compound were analyzed and evaluated by tissue staining and Micro-CT scanning. Results: The neoplastic fibrous tissue formed in the vascularized tissue engineering chamber with the introduction of abdominal superficial vessels, similar to normal fascia, was superior to the control group in terms of vascularization, vascular density, total vascular volume, and total vascular volume/total tissue volume. Conclusion: In vivo, introducing abdominal superficial vessels in the tissue engineering chamber prepped for ear prosthesis may form a well-vascularized pedicled fascia-prosthesis compound that can be used for ear reconstruction.

Perimeter and carvacrol-loading regulate angiogenesis and biofilm growth in 3D printed PLA scaffolds

Carvacrol is a natural low-cost compound derived from oregano which presents anti-bacterial properties against both Gram-positive and Gram-negative bacteria. In this work, carvacrol-loaded PLA scaffolds were fabricated by 3D printing as platforms to support bone tissue regeneration while preventing biofilm development. Scaffolds were printed with or without a perimeter (lateral wall) mimicking the cortical structure of bone tissue to further evaluate if the lateral interconnectivity could affect the biological or antimicrobial properties of the scaffolds. Carvacrol incorporation was performed by loading either the PLA filament prior to 3D printing or the already printed PLA scaffold. The loading method determined carvacrol localization in the scaffolds and its release profile. Biphasic profiles were recorded in all cases, but scaffolds loaded post-printed released carvacrol much faster, with 50-80% released in the first day, compared to those containing carvacrol in PLA filament before printing which sustained the release for several weeks. The presence or absence of the perimeter did not affect the release rate, but total amount released. Tissue integration and vascularization of carvacrol-loaded scaffolds were evaluated in a chorioallantoic membrane model (CAM) using a novel quantitative micro-computed tomography (micro-CT) analysis approach. The obtained results confirmed the CAM tissue ingrowth and new vessel formation within the porous structure of the scaffolds after 7 days of incubation, without leading to hemorrhagic or cytotoxic effects. The absence of lateral wall facilitated lateral integration of the scaffolds in the host tissue, although increased the anisotropy of the mechanical properties. Scaffolds loaded with carvacrol post-printing showed antibiofilm activity against Staphylococcus aureus and Pseudomonas aeruginosa as observed in a decrease in CFU counting after biofilm detachment, changes in metabolic heat measured by calorimetry, and increased contact killing efficiency. In summary, this work demonstrated the feasibility of tuning carvacrol release rate and the amount released from PLA scaffolds to achieve antibiofilm protection without altering angiogenesis, which was mostly dependent on the perimeter density of the scaffolds.

Emerging polymeric biomaterials and manufacturing techniques in regenerative medicine

The current demand for patients’ organ and tissue repair and regeneration is continually increasing, where autologous or allograft is the golden standard treatment in the clinic. However, due to the shortage of donors, mismatched size and modality, functional loss of the donor region, possible immune rejection, and so forth, the application of auto‐/allo‐grafts is frequently hindered in many cases. In order to solve these problems, artificial constructs structurally and functionally imitating the extracellular matrix have been developed as substitutes to promoting cell attachment, proliferation, and differentiation, and ultimately forming functional tissues or organs for better tissue regeneration. Particularly, polymeric materials have been widely utilized in regenerative medicine because of their ease of manufacturing, flexibility, biocompatibility, as well as good mechanical, chemical, and thermal properties. This review presents a comprehensive overview of a variety of polymeric materials, their fabrication methods as well applications in regenerative medicine. Finally, we discussed the future challenges and perspectives in the development and clinical transformation of polymeric biomaterials.

Scalable macroporous hydrogels enhance stem cell treatment of volumetric muscle loss

Volumetric muscle loss (VML), characterized by an irreversible loss of skeletal muscle due to trauma or surgery, is accompanied by severe functional impairment and long-term disability. Tissue engineering strategies combining stem cells and biomaterials hold great promise for skeletal muscle regeneration. However, scaffolds, including decellularized extracellular matrix (dECM), hydrogels, and electrospun fibers, used for VML applications generally lack macroporosity. As a result, the scaffolds used typically delay host cell infiltration, transplanted cell proliferation, and new tissue formation. To overcome these limitations, we engineered a macroporous dECM-methacrylate (dECM-MA) hydrogel, which we will refer to as a dECM-MA sponge, and investigated its therapeutic potential in vivo. Our results demonstrate that dECM-MA sponges promoted early cellularization, endothelialization, and establishment of a pro-regenerative immune microenvironment in a mouse VML model. In addition, dECM-MA sponges enhanced the proliferation of transplanted primary muscle stem cells, muscle tissue regeneration, and functional recovery four weeks after implantation. Finally, we investigated the scale-up potential of our scaffolds using a rat VML model and found that dECM-MA sponges significantly improved transplanted cell proliferation and muscle regeneration compared to conventional dECM scaffolds. Together, these results validate macroporous hydrogels as novel scaffolds for VML treatment and skeletal muscle regeneration.

Construction and Evaluation of Small-Diameter Bioartificial Arteries Based on a Combined-Mold Technology

Arterial stenosis or blockage is the leading cause of cardiovascular disease, and the common solution is to substitute the arteries by autologous veins or bypass the blood vessels physically. With the development of science and technology, arteries with diameter larger than 6 mm can be substituted by unbiodegradable polymers, such as polytetrafluoroethylene, clinically. Nevertheless, the construction of a small-diameter (less than 6 mm) artery with living cells has always been a thorny problem. In this study, a suit of combined mold was designed and forged for constructing small-diameter arterial vessels. Based on this combined mold, bioactive arterial vessels containing adipose-derived stem cells (ASCs) and different growth factors (GFs) were assembled together to mimic the inner and middle layers of the natural arteries. Before assembling, ASCs and GFs were loaded into a gelatin/alginate hydrogel. To enhance the mechanical property of the bilayer arterial vessels, polylactic–glycolic acid (PLGA) was applied on the surface of the bilayer vessels to form the outer third layer. The biocompatibility, morphology and mechanical property of the constructed triple-layer arterial vessels were characterized. The morphological results manifested that cells grow well in the gelatin/alginate hydrogels, and ASCs were differentiated into endothelial cells (ECs) and smooth muscle cells (SMCs), respectively. In addition, under the action of shear stress produced by the flow of the culture medium, cells in the hydrogels with high density were connected to each other, similar to the natural vascular endothelial tissues (i.e., endothelia). Especially, the mechanical property of the triple-layer arterial vessels can well meet the anti-stress requirements as human blood vessels. In a word, a small-diameter arterial vessel was successfully constructed through the combined mold and has a promising application prospect as a clinical small-diameter vessel graft.

Biomimetic Surface Topography from the Rubus fruticosus Leaf as a Guidance of Angiogenesis in Tissue Engineering Applications

The promotion of angiogenesis is a fundamental step for efficient organ/tissue reconstitution and replacement. Thus, several strategies to promote vascularization of scaffolds were studied to satisfy this unsolved clinical need. The interface between cells and substrates is a determinant for the success of tissue engineering (TE) strategies. Substrate's topography is reported to play a key role in influencing endothelial cell behavior, namely, on its proliferation, metabolic activity, morphology, migration, and secretion of cytokines and chemokines. Therefore, surface topography of the biomaterial-based grafts is a crucial property that is considered in the development of a new TE approach. Herein, we hypothesize that the surface of Rubus fruticosus leaf plays a crucial role in driving angiogenesis since its architecture resembles the vascular structures at a biologically relevant size scale. For this, we produced biomimetic polycaprolactone (PCL) membranes (BpMs) replicating the surface topography of a R. fruticosus leaf by replica molding and nanoimprint lithography. Our results showed an enhanced performance in terms of proliferation of the human endothelial cell line on top of the BpM. Moreover, an asymmetric cellular spatial distribution among the surface of the BpM was observed. These cells seem to have higher density for longer time periods in the region that replicates the leaf veins. Finally, we assess the angiogenic capacity through a chick chorioallantoic membrane assay, revealing that BpMs are more prone to support angiogenesis than flat PCL membranes. We strongly believe that this strategy can bring new insights into developing TE strategies with an enhanced performance in terms of the vascular integration between the host and the scaffolds implanted.

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.

Tissue engineered in-vitro vascular patch fabrication using hybrid 3D printing and electrospinning

Three-dimensional (3D) engineered cardiovascular tissues have shown great promise to replace damaged structures. Specifically, tissue engineering vascular grafts (TEVG) have the potential to replace biological and synthetic grafts. We aimed to design an in-vitro patient-specific patch based on a hybrid 3D print combined with vascular smooth muscle cells (VSMC) differentiation. Based on the medical images of a 2 months-old girl with aortic arch hypoplasia and using computational modelling, we evaluated the most hemodynamically efficient aortic patch surgical repair. Using the designed 3D patch geometry, the scaffold was printed using a hybrid fused deposition modelling (FDM) and electrospinning techniques. The scaffold was seeded with multipotent mesenchymal stem cells (MSC) for later maturation to derived VSMC (dVSMC). The graft showed adequate resistance to physiological aortic pressure (burst pressure 101 ​± ​15 ​mmHg) and a porosity gradient ranging from 80 to 10 ​μm allowing cells to infiltrate through the entire thickness of the patch. The bio-scaffolds showed good cell viability at days 4 and 12 and adequate functional vasoactive response to endothelin-1. In summary, we have shown that our method of generating patient-specific patch shows adequate hemodynamic profile, mechanical properties, dVSMC infiltration, viability and functionality. This innovative 3D biotechnology has the potential for broad application in regenerative medicine and potentially in heart disease prevention.

Recent advances on bioengineering approaches for fabrication of functional engineered cardiac pumps: A review

The field of cardiac tissue engineering has advanced over the past decades; however, most research progress has been limited to engineered cardiac tissues (ECTs) at the microscale with minimal geometrical complexities such as 3D strips and patches. Although microscale ECTs are advantageous for drug screening applications because of their high-throughput and standardization characteristics, they have limited translational applications in heart repair and the in vitro modeling of cardiac function and diseases. Recently, researchers have made various attempts to construct engineered cardiac pumps (ECPs) such as chambered ventricles, recapitulating the geometrical complexity of the native heart. The transition from microscale ECTs to ECPs at a translatable scale would greatly accelerate their translational applications; however, researchers are confronted with several major hurdles, including geometrical reconstruction, vascularization, and functional maturation. Therefore, the objective of this paper is to review the recent advances on bioengineering approaches for fabrication of functional engineered cardiac pumps. We first review the bioengineering approaches to fabricate ECPs, and then emphasize the unmatched potential of 3D bioprinting techniques. We highlight key advances in bioprinting strategies with high cell density as researchers have begun to realize the critical role that the cell density of non-proliferative cardiomyocytes plays in the cell-cell interaction and functional contracting performance. We summarize the current approaches to engineering vasculatures both at micro- and meso-scales, crucial for the survival of thick cardiac tissues and ECPs. We showcase a variety of strategies developed to enable the functional maturation of cardiac tissues, mimicking the in vivo environment during cardiac development. By highlighting state-of-the-art research, this review offers personal perspectives on future opportunities and trends that may bring us closer to the promise of functional ECPs.

In Situ Prevascularization Strategy with Three-Dimensional Porous Conduits for Neural Tissue Engineering

Neovascularization is crucial for peripheral nerve regeneration and long-term functional restoration. Previous studies have emphasized strategies that enhance axonal repair over vascularization. Here, we describe the development and application of an in situ prevascularization strategy that uses 3D porous nerve guidance conduits (NGCs) to achieve angiogenesis-mediated neural regeneration. The optimal porosity of the NGC is a critical feature for achieving neovascularization and nerve growth patency. Hollow silk fibroin/poly(l-lactic acid-co-ε-caprolactone) NGCs with 3D sponge-like walls were fabricated using electrospinning and freeze-drying. In vitro results showed that 3D porous NGC favored cell biocompatibility had neuroregeneration potential and, most importantly, had angiogenic activity. Results from our mechanistic studies suggest that activation of HIF-1α signaling might be associated with this process. We also tested in situ prevascularized 3D porous NGCs in vivo by transplanting them into a 10 mm rat sciatic nerve defect model with the aim of regenerating the severed nerve. The prevascularized 3D porous NGCs greatly enhanced intraneural angiogenesis, resulting in demonstrable neurogenesis. Eight weeks after transplantation, the performance of the prevascularized 3D NGCs was similar to that of traditional autografts in terms of improved anatomical structure, morphology, and neural function. In conclusion, combining a reasonably fabricated 3D-pore conduit structure with in situ prevascularization promoted functional nerve regeneration, suggesting an alternative strategy for achieving functional recovery after peripheral nerve trauma.

Engineering calcium peroxide based oxygen generating scaffolds for tissue survival

Oxygen supply is essential for the long-term viability and function of tissue engineered constructs in vitro and in vivo. The integration with the host blood supply as the primary source of oxygen to cells requires 4 to 5 weeks in vivo and involves neovascularization stages to support the delivery of oxygenated blood to cells. Consequently, three-dimensional (3D) encapsulated cells during this process are prone to oxygen deprivation, cellular dysfunction, damage, and hypoxia-induced necrosis. Here we demonstrate the use of calcium peroxide (CaO2) and polycaprolactone (PCL), as part of an emerging paradigm of oxygen-generating scaffolds that substitute the host oxygen supply via hydrolytic degradation. The 35-day in vitro study showed predictable oxygen release kinetics that achieved 5% to 29% dissolved oxygen with increasing CaO2 loading. As a biomaterial, the iterations of 0 mg, 40 mg, and 60 mg of CaO2 loaded scaffolds yielded modular mechanical behaviors, ranging from 5-20 kPa in compressive strength. The other controlled physiochemical features included swelling capacities of 22-33% and enzymatic degradation rates of 0.8% to 60% remaining mass. The 3D-encapsulation experiments of NIH/3T3 fibroblasts, L6 rat myoblasts, and primary cardiac fibroblasts in these scaffolds showed enhanced cell survival, proliferation, and function under hypoxia. During continuous oxygen release, the scaffolds maintained a stable tissue culture system between pH 8 to 9. The broad basis of this work supports prospects in the expansion of robust and clinically translatable tissue constructs.

Bioactive glass activates VEGF paracrine signaling of cardiomyocytes to promote cardiac angiogenesis

The heart contains a wide range of cell types, which are not isolated but interact with one another via multifarious paracrine, autocrine and endocrine factors. In terms of cardiac angiogenesis, previous studies have proved that regulating the communication between cardiomyocytes and endothelial cells is efficacious to promote capillary formation. Firstly, this study investigated the effect and underlying mechanism of bioactive glass (BG) acted on vascular endothelial growth factor (VEGF) paracrine signaling in cardiomyocytes. We found that bioactive ions released from BG significantly promoted the VEGF production and secretion of cardiomyocytes. Subsequently, we proved that cardiomyocyte-derived VEGF played an important role in mediating the behavior of endothelial cells. Further research showed that the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/hypoxia-inducible factor 1α (HIF-1α) signaling pathway was upregulated by BG, which was involved in VEGF expression of cardiomyocytes. This study revealed that by means of modulating cellular crosstalk via paracrine signaling of host cells in heart is a new direction for the application of BGs in cardiac angiogenesis.

Fabrication of centimeter-sized 3D constructs with patterned endothelial cells through assembly of cell-laden microbeads as a potential bone graft

Modular tissue engineering is a promising biofabrication strategy to create engineered bone grafts in a bottom-up manner, in which cell-laden micro-modules are prepared as basic building blocks to assemble macroscopic tissues via different integrating mechanisms. In this study, we prepared collagen microbeads loaded with human bone marrow derived mesenchymal stem cells (BMSCs) using a microfluidic approach. The cell-laden microbeads were characterized for size change, cell activity, osteogenesis, as well as their self-assembly properties to generate centimeter-sized constructs. Moreover, using the cell-laden beads as a supporting medium, induced pluripotent stem cell-derived endothelial cells (iPSC-EC) were patterned inside bead aggregates through extrusion-based 3D printing. This fabrication approach that combines modular tissue engineering and supports 3D printing has the potential to create 3D engineered bone grafts with a pre-existing, customized vasculature.

Signaling molecules orchestrating liver regenerative medicine

The liver is in charge of more than 500 functions in the human body, which any damage and failure to the liver can significantly compromise human life. Numerous studies are being carried out in regenerative medicine, as a potential driving force, toward alleviating the need for liver donors and fabrication of a 3D-engineered transplantable hepatic tissue. Liver tissue engineering brings three main factors of cells, extracellular matrix (ECM), and signaling molecules together, while each of these three factors tries to mimic the physiological state of the tissue to direct tissue regeneration. Signaling molecules play a crucial role in directing tissue fabrication in liver tissue engineering. When mimicking the natural in vivo process of regeneration, it is tightly associated with three main phases of differentiation, proliferation (progression), and tissue maturation through vascularization while directing each of these phases is highly regulated by the specific signaling molecules. The understanding of how these signaling molecules guide the dynamic behavior of regeneration would be a tool for further tailoring of bioengineered systems to help the liver regeneration with many cellular, molecular, and tissue-level functions. Hence, the signaling molecules come to aid all these phases for further improvements toward the clinical use of liver tissue engineering as the goal.

The role of CD44 in pathological angiogenesis

Angiogenesis is required for normal development and occurs as a pathological step in a variety of disease settings, such as cancer, ocular diseases, and ischemia. Recent studies have revealed the role of CD44, a widely expressed cell surface adhesion molecule, in promoting pathological angiogenesis and the development of its associated diseases through its regulation of diverse function of endothelial cells, such as proliferation, migration, adhesion, invasion, and communication with the microenvironment. Conversely, the absence of CD44 expression or inhibition of its function impairs pathological angiogenesis and disease progression. Here, we summarize the current understanding of the roles of CD44 in pathological angiogenesis and the underlying cellular and molecular mechanisms.

Silicate bioceramics: from soft tissue regeneration to tumor therapy

Great efforts have been devoted to exploiting silicate bioceramics for various applications in soft tissue regeneration, owing to their excellent bioactivity. Based on the inherent ability of silicate bioceramics to repair tissue, bioactive ions are easily incorporated into silicate bioceramics to endow them with extra biological properties, such as enhanced angiogenesis, antibiosis, enhanced osteogenesis, and antitumor effect, which significantly expands the application of multifunctional silicate bioceramics. Furthermore, silicate nanobioceramics with unique structures have been widely employed for tumor therapy. In recent years, the novel applications of silicate bioceramics for both tissue regeneration and tumor therapy have substantially grown. Eliminating the skin tumors first and then repairing the skin wounds has been widely investigated by our groups, which might shed some light on treating other soft tissue tumor or tumor-induced defects. This review first describes the recent advances made in the development of silicate bioceramics as therapeutic platforms for soft tissue regeneration. We then highlight the major silicate nanobioceramics used for tumor therapy. Silicate bioceramics for both soft tissue regeneration and tumor therapy are further emphasized. Finally, challenges and future directions of silicate bioceramics stepping into the clinics are discussed. This review will inspire researchers to create the efficient and functional silicate bioceramics needed for regeneration and tumor therapy of other tissues.

Pre-Seeding of Simple Electrospun Scaffolds with a Combination of Endothelial Cells and Fibroblasts Strongly Promotes Angiogenesis

BACKGROUND

Introduction of pro-angiogenic cells into tissue-engineered (TE) constructs (prevascularisation) is a promising approach to overcome delayed neovascularisation of such constructs post-implantation. Accordingly, in this study, we examined the contribution of human dermal microvascular endothelial cells (HDMECs) and human dermal fibroblasts (HDFs) alone and in combination on the formation of new blood vessels in ex-ovo chick chorioallantoic membrane (CAM) assay.

METHODS

Poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) and polycaprolactone (PCL) were first examined in terms of their physical, mechanical, and biological performances. The effect of gelatin coating and co-culture conditions on enhancing endothelial cell viability and growth was then investigated. Finally, the angiogenic potential of HDMECs and HDFs were assessed macroscopically and histologically after seeding on simple electrospun PHBV scaffolds either in isolation or in indirect co-culture using an ex-ovo CAM assay.

RESULTS

The results demonstrated that PHBV was slightly more favourable than PCL for HDMECs in terms of cell metabolic activity. The gelatin coating of PHBV scaffolds and co-culture of HDMECs with HDFs both showed a positive impact on HDMECs viability and growth. Both cell types induced angiogenesis over 7 days in the CAM assay either in isolation or in co-culture. The introduction of HDMECs to the scaffolds resulted in the production of more blood vessels in the area of implantation than the introduction of HDFs, but the co-culture of HDMECs and HDFs gave the most significant angiogenic activity.

CONCLUSION

Our findings showed that the in vitro prevascularisation of TE constructs with HDMECs and HDFs alone or in co-culture promotes angiogenesis in implantable TE constructs.

2-deoxy-d-ribose (2dDR) upregulates vascular endothelial growth factor (VEGF) and stimulates angiogenesis

BACKGROUND

Delayed neovascularisation of tissue-engineered (TE) complex constructs is a major challenge that causes their failure post-implantation. Although significant progress has been made in the field of angiogenesis, ensuring rapid neovascularisation still remains a challenge. The use of pro-angiogenic agents is an effective approach to promote angiogenesis, and vascular endothelial growth factor (VEGF) has been widely studied both at the biological and molecular levels and is recognised as a key stimulator of angiogenesis. However, the exogenous use of VEGF in an uncontrolled manner has been shown to result in leaky, permeable and haemorrhagic vessels. Thus, researchers have been actively seeking alternative agents to upregulate VEGF production rather than exogenous use of VEGF in TE systems. We have previously revealed the potential of 2-deoxy-d-ribose (2dDR) as an alternative pro-angiogenic agent to induce angiogenesis and accelerates wound healing. However, to date, there is not any clear evidence on whether 2dDR influences the angiogenic cascade that involves VEGF.

METHODS

In this study, we explored the angiogenic properties of 2dDR either by its direct application to human aortic endothelial cells (HAECs) or when released from commercially available alginate dressings and demonstrated that when 2dDR promotes angiogenesis, it also increases the VEGF production of HAECs.

RESULTS

The VEGF quantification results suggested that VEGF production by HAECs was increased with 2dDR treatment but not with other sugars, including 2-deoxy-l-ribose (2dLR) and d-glucose (DG). The stability studies demonstrated that approximately 40-50% of the 2dDR had disappeared in the media over 14 days, either in the presence or absence of HAECs, and the reduction was higher when cells were present. The concentration of VEGF in the media also fell after day 4 associated with the reduction in 2dDR.

CONCLUSION

This study suggests that 2dDR (but not other sugars tested in this study) stimulates angiogenesis by increasing the production of VEGF. We conclude 2dDR appears to be a practical and effective indirect route to upregulating VEGF for several days, leading to increased angiogenesis.

Supercritical CO2 foamed composite scaffolds incorporating bioactive lipids promote vascularized bone regeneration via Hif-1α upregulation and enhanced type H vessel formation

Bone tissue engineering has substantial potential for the treatment of massive bone defects; however, efficient vascularization coupled with bone regeneration still remains a challenge in this field. In the current study, supercritical carbon dioxide (scCO₂) foaming technique was adopted to fabricate mesoporous bioactive glasses (MBGs) particle-poly (lactic-co-glycolic acid) (PLGA) composite scaffolds with appropriate mechanical and degradation properties as well as in vitro bioactivity. The MBG-PLGA scaffolds incorporating the bioactive lipid FTY720 (designated as FTY/MBG-PLGA) exhibited simultaneously sustained release of the bioactive lipid and ions. In addition to providing a favorable microenvironment for cellular adhesion and proliferation, FTY/MBG-PLGA scaffolds significantly facilitated the in vitro osteogenic differentiation of rBMSCs and also markedly stimulated the upregulation of Hif-1α expression via the activation of the Erk1/2 pathway, which mediated the osteogenic and pro-angiogenic effects on rBMSCs. Furthermore, FTY/MBG-PLGA extracts induced superior in vitro angiogenic performance of HUVECs. In vivo evaluation of critical-sized rat calvarial bone defects indicated that FTY/MBG-PLGA scaffolds potently promoted vascularized bone regeneration. Notably, the significantly enhanced formation of type H vessels (CD31^hiEmcn^hi neo-vessels) was observed in newly formed bone tissue in FTY/MBG-PLGA group, strongly suggesting that FTY720 and therapeutic ions released from the scaffolds synergistically induced more type H vessel formation, which indicated the coupling of angiogenesis and osteogenesis to achieve efficiently vascularized bone regeneration. Overall, the results indicated that the foamed porous MBG-PLGA scaffolds incorporating bioactive lipids achieved desirable vascularization-coupled bone formation and could be a promising strategy for bone regenerative medicine. STATEMENT OF SIGNIFICANCE: Efficacious coupling of vascularizationandbone formation is critical for the restoration of large bone defects. Anoveltechnique was used to fabricate composite scaffolds incorporating bioactive lipids which possessedsynergistic cues of bioactive lipids and therapeutic ions to potently promotebone regenerationas well as vascularization. The underlying molecular mechanism for the osteogenic and pro-angiogenic effects of the compositescaffolds was unveiled. Interestingly, the scaffolds were furtherfoundto enhance the formation oftype H capillarieswithin the bone healing microenvironment to couple angiogenesis to osteogenesis to achieve satisfyingvascularizedbone regeneration.These findings provide a novel strategy to develop efficiently vascularized engineering constructs to treat massive bone defects.

Exploration of 2-deoxy-D-ribose and 17β-Estradiol as alternatives to exogenous VEGF to promote angiogenesis in tissue-engineered constructs

Aim: In this study, we explored the angiogenic potential and proangiogenic concentration ranges of 2-deoxy-D-ribose (2dDR) and 17β-Estradiol (E2) in comparison with VEGF. The 2dDR and E2 were then loaded into tissue engineering (TE) scaffolds to investigate their proangiogenic potential when released from fibers. Materials & methods: Ex ovo chick chorioallantoic membrane (CAM) assay was used to evaluate angiogenic activity of 2dDR and E2. Both factors were then introduced into scaffolds via electrospinning to assess their angiogenic potential when released from fibers. Results: Both factors were approximately 80% as potent as VEGF and showed a dose-dependent angiogenic response. The sustained release of both agents from the scaffolds stimulated neovascularization over 7 days in the chorioallantoic membrane assay. Conclusion: We conclude that both 2dDR and E2 provide attractive alternatives to VEGF for the functionalization of tissue engineering scaffolds to promote angiogenesis in vivo.

[Vascular endothelial growth factor/polylactide-polyethyleneglycol-polylactic acid copolymer/basic fibroblast growth factor mixed microcapsules in promoting angiogenic differentiation of rat bone marrow mesenchymal stem cells in vitro]

Objective

To observe the effect of vascular endothelial growth factor/polylactide-polyethyleneglycol-polylactic acid copolymer/basic fibroblast growth factor (VEGF/PELA/bFGF) mixed microcapsules in promoting the angiogenic differentiation of rat bone marrow mesenchymal stem cells (BMSCs) in vitro.

Methods

The BMSCs were isolated by the method of whole bone marrow adherent, and sub-cultured. The passage 3 BMSCs were identified by Wright-Giemsa staining and flow cytometry, and used for subsequent experiments. VEGF/PELA/bFGF (group A), PELA/bFGF (group B), VEGF/PELA (group C), and PELA (group D) microcapsules were prepared. The biodegradable ability and cytotoxicity of PELA microcapsule were determined，and the slow-released ability of VEGF/PELA/bFGF mixed microcapsules was measured. The passage 3 BMSCs were co-cultured with the extracts of groups A, B, C, and D, separately. At 1, 3, 7, 14, and 20 days after being cultured, the morphological changes of induced BMSCs were recorded. At 21 days, the induced BMSCs were tested for DiI-labeled acetylated low density lipoprotein (Dil-ac-LDL) and FITC-labeled ulex europaeus agglutinin I (FITC-UEA-I) uptake ability. The tube-forming ability of the induced cells on Matrigel was also verified. The differences of the vascularize indexes in nodes, master junctions, master segments, and tot.master segments length in 4 groups were summarized and analyzed.

Results

The isolated and cultured cells were identified as BMSCs. The degradation time of PELA was more than 20 days. There was no significant effect on cell viability under co-culture conditions. At 20 days, the cumulative release of VEGF in the mixed microcapsules exceeded 95%, and the quantity of bFGF exceeded 80%. The morphology of cells in groups A, B, and C were changed. The cells in groups A and B showed the typical change of cobble-stone morphology. The numbers of double fluorescent labeled cells observed by fluorescence microscope were the most in group A, and decreases from group B and group C, with the lowest in group D. The cells in groups A and B formed a grid-like structure on Matrigel. Quantitative analysis showed that the differences in the number of nodes, master junctions, master segments, and tot.master segments length between groups A, B and groups C, D were significant ( P<0.05). The number of nodes and the tot.master segments length of group A were more than those of group B ( P<0.05). There was no significant differences in the number of master junctions and master segments between group A and group B ( P>0.05).

Conclusion

VEGF/PELA/bFGF mixed microcapsules have significantly ability to promote the angiogenic differentiation of rat BMSCs in vitro.

Cationized Bombyx mori silk fibroin as a delivery carrier of the VEGF165-Ang-1 coexpression plasmid for dermal tissue regeneration

The angiogenesis of an implanted construct is among the most important issues in tissue engineering. In this study, spermine was used to modify Bombyx mori silk fibroin (BSF) to synthesize cationized BSF (CBSF). BSF and CBSF were coated in sequence on the surface of polyethyleneimine (PEI)/vascular endothelial growth factor 165/angiopoietin-1 coexpression plasmid DNA (pDNA) complexes to form CBSF/BSF/PEI/pDNA quaternary complexes. BSF scaffolds loaded with carrier/pDNA complexes were prepared as dermal regeneration scaffolds by freeze-drying. In one set of experiments, scaffolds were used to cover a chick embryo chorioallantoic membrane (CAM) to investigate the influence of carrier/pDNA complexes on angiogenesis; in another set of experiments, scaffolds were implanted into dorsal full-thickness wounds in Sprague-Dawley rats to evaluate the effect of carrier/pDNA complex-loaded BSF scaffolds on neovascularization and dermal tissue regeneration. After modification with spermine, the surface zeta potential value of BSF rose to +11 mV from an initial value of -9 mV, and the isoelectric point of BSF increased from 4.20 to 9.04. The in vitro transfection of human umbilical vein endothelial cells (EA.hy926) with quaternary complexes revealed that the CBSF/BSF/PEI/pDNA complexes clearly exhibited lower cytotoxicity and higher transfection efficiency than the PEI/pDNA complexes. The CAM assay showed a more abundant branching pattern of blood vessels in BSF scaffolds loaded with CBSF/BSF/PEI/pDNA complexes than in BSF scaffolds without complexes or loaded with PEI/pDNA complexes. The in vivo experimental results demonstrated that the incorporation of CBSF/BSF/PEI/pDNA complexes could effectively enhance angiogenesis in the implanted BSF scaffolds, thereby promoting the regeneration of dermal tissue, providing a new scaffold for the regeneration of dermal tissue and other tissues containing blood vessels.

Vascular extracellular matrix and fibroblasts-coculture directed differentiation of human mesenchymal stem cells toward smooth muscle-like cells for vascular tissue engineering

Construction of an artificial vascular graft is widely considered a promising strategy in vascular tissue engineering. However, limited sources of functional vascular smooth muscle cells (VSMCs) remain a major obstacle in vascular tissue engineering. In this study, we innovatively developed an approach to obtain functional VSMCs by onsite differentiating human bone marrow-derived mesenchymal stem cells (MSCs) directed by decellularized extracellular matrix (ECM) and fibroblasts. The resulting cells and ECM-cells constructs were characterized by real time RT-PCR, immunofluorescence staining, cell contractile functions, and migration capacity. Our results showed both ECM and fibroblasts induced MSCs differentiation toward VSMC-like cells with increased transcription of marker genes, upregulated expression of contractile apparatus proteins, and enhanced functional activity of VSMC phenotype. Interestingly, our findings revealed that native ECM and fibroblasts-coculture had a higher potential to promote MSCs differentiation into VSMCs than growth factors cocktail (GFC) supplemented culture, thereby providing a potential source of VSMCs for blood vessel constitution.

The Arteriovenous (AV) Loop in a Small Animal Model to Study Angiogenesis and Vascularized Tissue Engineering

A functional blood vessel network is a prerequisite for the survival and growth of almost all tissues and organs in the human body. Moreover, in pathological situations such as cancer, vascularization plays a leading role in disease progression. Consequently, there is a strong need for a standardized and well-characterized in vivo model in order to elucidate the mechanisms of neovascularization and develop different vascularization approaches for tissue engineering and regenerative medicine. We describe a microsurgical approach for a small animal model for induction of a vascular axis consisting of a vein and artery that are anastomosed to an arteriovenous (AV) loop. The AV loop is transferred to an enclosed implantation chamber to create an isolated microenvironment in vivo, which is connected to the living organism only by means of the vascular axis. Using 3D imaging (MRI, micro-CT) and immunohistology, the growing vasculature can be visualized over time. By implanting different cells, growth factors and matrices, their function in blood vessel network formation can be analyzed without any disturbing influences from the surroundings in a well controllable environment. In addition to angiogenesis and antiangiogenesis studies, the AV loop model is also perfectly suited for engineering vascularized tissues. After a certain prevascularization time, the generated tissues can be transplanted into the defect site and microsurgically connected to the local vessels, thereby ensuring immediate blood supply and integration of the engineered tissue. By varying the matrices, cells, growth factors and chamber architecture, it is possible to generate various tissues, which can then be tailored to the individual patient's needs.

Human hepatocytes loaded in 3D bioprinting generate mini-liver

BACKGROUND

Because of an increasing discrepancy between the number of potential liver graft recipients and the number of organs available, scientists are trying to create artificial liver to mimic normal liver function and therefore, to support the patient's liver when in dysfunction. 3D printing technique meets this purpose. The present study was to test the feasibility of 3D hydrogel scaffolds for liver engineering.

METHODS

We fabricated 3D hydrogel scaffolds with a bioprinter. The biocompatibility of 3D hydrogel scaffolds was tested. Sixty nude mice were randomly divided into four groups, with 15 mice in each group: control, hydrogel, hydrogel with L02 (cell line HL-7702), and hydrogel with hepatocyte growth factor (HGF). Cells were cultured and deposited in scaffolds which were subsequently engrafted into livers after partial hepatectomy and radiation-induced liver damage (RILD). The engrafted tissues were examined after two weeks. The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin, total bilirubin, CYP1A2, CYP2C9, glutathione S-transferase (a-GST), and UDP-glucuronosyl transferase (UGT-2) were compared among the groups. Hematoxylin-eosin (HE) staining and immunohistochemistry of cKit and cytokeratin 18 (CK18) of engrafted tissues were evaluated. The survival time of the mice was also compared among the four groups.

RESULTS

3D hydrogel scaffolds did not impact the viability of cells. The levels of ALT, AST, albumin, total bilirubin, CYP1A2, CYP2C9, a-GST and UGT-2 were significantly improved in mice engrafted with 3D scaffold loaded with L02 compared with those in control and scaffold only (P<0.05). HE staining showed clear liver tissue and immunohistochemistry of cKit and CK18 were positive in the engrafted tissue. Mice treated with 3D scaffold+L02 cells had longer survival time compared with those in control and scaffold only (P<0.05).

CONCLUSION

3D scaffold has the potential of recreating liver tissue and partial liver functions and can be used in the reconstruction of liver tissues.

Fabrication of Biodegradable Synthetic Vascular Networks and Their Use as a Model of Angiogenesis

One of the greatest challenges currently faced in tissue engineering is the incorporation of vascular networks within tissue-engineered constructs. The aim of this study was to develop a technique for producing a perfusable, 3-dimensional, cell-friendly model of vascular structures that could be used to study the factors affecting angiogenesis and vascular biology in engineered systems in more detail. Initially, biodegradable synthetic pseudovascular networks were produced via the combination of robocasting and electrospinning techniques. The internal surfaces of the vascular channels were then recellularized with human dermal microvascular endothelial cells (HDMECs) with and without the presence of human dermal fibroblasts (HDFs) on the outer surface of the scaffold. After 7 days in culture, channels that had been reseeded with HDMECs alone demonstrated irregular cell coverage. However, when using a co-culture of HDMECs inside and HDFs outside the vascular channels, coverage was found to be continuous throughout the internal channel. Using this cell combination, collagen gels loaded with vascular endothelial growth factor were deposited onto the outer surface of the scaffold and cultured for a further 7 days. After this, endothelial cell outgrowth from within the channels into the collagen gel was observed, showing that the engineered vasculature maintains its capacity for angiogenesis. Furthermore, the HDMECs appeared to have formed perfusable tubules within the gel. These results show promising steps towards the development of an in vitro platform for studying angiogenesis and vascular biology in a tissue engineering context.

Tissue Engineering by Intrinsic Vascularization in an In Vivo Tissue Engineering Chamber

In reconstructive surgery, there is a clinical need for an alternative to the current methods of autologous reconstruction which are complex, costly and trade one defect for another. Tissue engineering holds the promise to address this increasing demand. However, most tissue engineering strategies fail to generate stable and functional tissue substitutes because of poor vascularization. This paper focuses on an in vivo tissue engineering chamber model of intrinsic vascularization where a perfused artery and a vein either as an arteriovenous loop or a flow-through pedicle configuration is directed inside a protected hollow chamber. In this chamber-based system angiogenic sprouting occurs from the arteriovenous vessels and this system attracts ischemic and inflammatory driven endogenous cell migration which gradually fills the chamber space with fibro-vascular tissue. Exogenous cell/matrix implantation at the time of chamber construction enhances cell survival and determines specificity of the engineered tissues which develop. Our studies have shown that this chamber model can successfully generate different tissues such as fat, cardiac muscle, liver and others. However, modifications and refinements are required to ensure target tissue formation is consistent and reproducible. This article describes a standardized protocol for the fabrication of two different vascularized tissue engineering chamber models in vivo.

Three-Dimensional Imaging of the Developing Vasculature within Stem Cell-Seeded Scaffolds Cultured in ovo

Successful tissue engineering requires functional vascularization of the three-dimensional constructs with the aim to serve as implants for tissue replacement and regeneration. The survival of the implant is only possible if the supply of oxygen and nutrients by developing capillaries from the host is established. The chorioallantoic membrane (CAM) assay is a valuable tool to study the ingrowth and distribution of vessels into scaffolds composed by appropriate biomaterials and stem cell populations that are used in cell-based regenerative approaches. The developing vasculature of chicken embryos within cell-seeded scaffolds can be visualized with microcomputed tomography after intravenous injection of MicroFil®, which is a radiopaque contrast agent. Here, we provide a step-by-step protocol for the seeding of stem cells into silk fibroin scaffolds, the CAM culture conditions, the procedure of MicroFil® perfusion, and finally the microcomputed tomography scanning. Three-dimensional imaging of the vascularized tissue engineered constructs provides an important analytical tool for studying the potential of cell seeded scaffolds to attract vessels and form vascular networks, as well as for analyzing the number, density, length, branching, and diameter of vessels. This in ovo method can greatly help to screen implants that will be used for tissue regeneration purposes before their in vivo testing, thereby reducing the amount of animals needed for pre-clinical studies.

Angiogenesis in tissue-engineered nerves evaluated objectively using MICROFIL perfusion and micro-CT scanning

Angiogenesis is a key process in regenerative medicine generally, as well as in the specific field of nerve regeneration. However, no convenient and objective method for evaluating the angiogenesis of tissue-engineered nerves has been reported. In this study, tissue-engineered nerves were constructed in vitro using Schwann cells differentiated from rat skin-derived precursors as supporting cells and chitosan nerve conduits combined with silk fibroin fibers as scaffolds to bridge 10-mm sciatic nerve defects in rats. Four weeks after surgery, three-dimensional blood vessel reconstructions were made through MICROFIL perfusion and micro-CT scanning, and parameter analysis of the tissue-engineered nerves was performed. New blood vessels grew into the tissue-engineered nerves from three main directions: the proximal end, the distal end, and the middle. The parameter analysis of the three-dimensional blood vessel images yielded several parameters, including the number, diameter, connection, and spatial distribution of blood vessels. The new blood vessels were mainly capillaries and microvessels, with diameters ranging from 9 to 301 μm. The blood vessels with diameters from 27 to 155 μm accounted for 82.84% of the new vessels. The microvessels in the tissue-engineered nerves implanted in vivo were relatively well-identified using the MICROFIL perfusion and micro-CT scanning method, which allows the evaluation and comparison of differences and changes of angiogenesis in tissue-engineered nerves implanted in vivo.

Cell-based strategies for vascular regeneration

Vascular regeneration is known to play an essential role in the repair of injured tissues mainly through accelerating the repair of vascular injury caused by vascular diseases, as well as the recovery of ischemic tissues. However, the clinical vascular regeneration is still challenging. Cell-based therapy is thought to be a promising strategy for vascular regeneration, since various cells have been identified to exert important influences on the process of vascular regeneration such as the enhanced endothelium formation on the surface of vascular grafts, and the induction of vessel-like network formation in the ischemic tissues. Here are a vast number of diverse cell-based strategies that have been extensively studied in vascular regeneration. These strategies can be further classified into three main categories, including cell transplantation, construction of tissue-engineered grafts, and surface modification of scaffolds. Cells used in these strategies mainly refer to terminally differentiated vascular cells, pluripotent stem cells, multipotent stem cells, and unipotent stem cells. The aim of this review is to summarize the reported research advances on the application of various cells for vascular regeneration, yielding insights into future clinical treatment for injured tissue/organ.

Fibrin Scaffolds Designing in order to Human Adipose-derived Mesenchymal Stem Cells Differentiation to Chondrocytes in the Presence of TGF-β3

BACKGROUND AND OBJECTIVES

One of the most cellular source used for cartilage tissue engineering are mesenchymal stem cells (MSCs). In present study, human MSCs were used as cellular source. Since scaffold plays an important role in tissue engineering the aim of this study is to assess fibrin scaffold ability in chondrogenic differentiation of adipose-derived mesenchymal stem cells (ADMSCs).

METHODS

ADMSCs were isolated and cultured in DMEM medium supplemented with 10% FBS. Also ADMSCs expanded and characterised by flow cytometry. ADMSCs expressed CD44, CD90, CD105 but not CD34. After trypsinization, cells were entered within the fibrin scaffold. Then, chondrogenic medium was added to the scaffold. Seven days after cell culture, cell viability and proliferation were assessed by MTT test. Finally, 14 days after the ending of chondrogenic differentiation, analysis of chondrogenic genes expression was evaluated by RT-PCR and Real time PCR. Also, formation and development of chondrocyte cells was analysed by histological and immunohistochemistry evaluations.

RESULTS

Viability and proliferation as well as chondrogenic genes expression within fibrin scaffold increased significantly compared with control group (cells free scaffold). Also, histological and immunohistochemistry evaluation showed that chondrocyte cells and collagen type II are formed on fibrin scaffold.

CONCLUSIONS

Fibrin is a suitable scaffold for chondrogenic differentiation of ADMSCs.

Stem cell-derived vasculature: A potent and multidimensional technology for basic research, disease modeling, and tissue engineering

Proper blood vessel networks are necessary for constructing and re-constructing tissues, promoting wound healing, and delivering metabolic necessities throughout the body. Conversely, an understanding of vascular dysfunction has provided insight into the pathogenesis and progression of diseases both common and rare. Recent advances in stem cell-based regenerative medicine - including advances in stem cell technologies and related progress in bioscaffold design and complex tissue engineering - have allowed rapid advances in the field of vascular biology, leading in turn to more advanced modeling of vascular pathophysiology and improved engineering of vascularized tissue constructs. In this review we examine recent advances in the field of stem cell-derived vasculature, providing an overview of stem cell technologies as a source for vascular cell types and then focusing on their use in three primary areas: studies of vascular development and angiogenesis, improved disease modeling, and the engineering of vascularized constructs for tissue-level modeling and cell-based therapies.