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Decellularized allogeneic and xenogeneic articular cartilage matrix scaffolds (CMS) are considered ideal scaffolds for cartilage regeneration owing to their heterogeneous architecture, and biochemical and biomechanical properties of native articular cartilage. However, the dense structure of the articular cartilage extracellular matrix, particularly the arrangement of collagen fibers, limits cellular infiltration, leading to poor cartilage regeneration. In addition, the incomplete removal of xenograft cells is associated with immunogenic reaction in the host. To facilitate the migration of chondrocytes into scaffolds and the rate of decellularization processing, we applied a carbon dioxide laser technique to modify the surface of porcine CMS while retaining major properties of the scaffold. By optimizing the laser parameters, we introduced orderly, lattice-arranged conical micropores of suitable depth and diameter onto the cartilage scaffold surface without affecting the cartilage shape or mechanical properties. We found that laser-modified CMS (LM-CMS) could enhance the degree of decellularization and were conducive to cell adhesion, as compared with the intact CMS. Decellularized scaffolds were seeded with rabbit-derived chondrocytes and cultured for 8 weeks in vitro. We found that cell-scaffold constructs formed cartilage-like tissue within the micropores and on the scaffold surface. In vivo, we found that cell-scaffold constructs subcutaneously implanted into the flanks of nude mice formed ivory-white neocartilage with high contents of DNA and cartilage matrix components, as well as good mechanical strength as compared with native CMS. Furthermore, scaffolds combined with autogenous chondrocytes induced neocartilage and better structural restoration at 8 weeks after transplantation into rabbit knee articular cartilage defects. In conclusion, decellularized xenogeneic CMS with laser-machined micropores offers an ideal scaffold with high fidelity for the functional reconstruction of articular cartilage., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Tissue scaffolds with three-dimensional (3D) nanofibrous biomimetic structures have attracted attention in the field of bone regeneration. In recent years, emerging strategies based on electrospinning technologies have facilitated the preparation of 3D nanofibrous scaffolds. Based on these developments, in this study, 3D scaffolds possessing both nanofibrous morphologies and interconnected pores were fabricated for their potential in bone tissue engineering. By combining homogenizing, freeze-drying, and thermal crosslinking techniques, nano-hydroxyapatite/PLLA/gelatin (nHA/PLA/GEL) 3D nanofibrous scaffolds were prepared using pre-fabricated electrospun nanofibers. Then, utilizing a polydopamine (pDA)-assisted coating strategy, bone morphogenetic protein-2 (BMP-2)-derived peptides were further immobilized onto the 3D scaffolds to obtain the resulting nano-hydroxyapatite/PLLA/gelatin-peptide (nHA/PLA/GEL-PEP) 3D nanofibrous scaffolds capable of sustained release. Bone mesenchymal stem cells (BMSCs) were cultured on the 3D nanofibrous scaffolds, then relative cell viability, alkaline phosphatase (ALP) activity, and gene expression assays were performed to study the effects of the scaffolds on cell growth and osteogenic differentiation in vitro. Furthermore, the ability of bone formation in vivo was evaluated using a rat cranial bone defect model. In vitro and in vivo results demonstrated that the 3D nanofibrous scaffolds incorporated with nHA and BMP-2 peptides exhibited favorable biocompatibility and osteoinductivity. Therefore, these nanofibrous scaffolds have excellent potential in bone regenerative medicine., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Repair of cartilage defects is highly challenging in clinical treatment. Tissue engineering provides a promising approach for cartilage regeneration and repair. As a core component of tissue engineering, scaffolds have a crucial influence on cartilage regeneration, especially in immunocompetent large animal and human. Native polymers, such as gelatin and hyaluronic acid, have known as ideal biomimetic scaffold sources for cartilage regeneration. However, how to precisely control their structure, degradation rate, and mechanical properties suitable for cartilage regeneration remains a great challenge. To address these issues, a series of strategies were introduced in the current study to optimize the scaffold fabrication. First, gelatin and hyaluronic acid were prepared into a hydrogel and 3D printing was adopted to ensure precise control in both the outer 3D shape and internal pore structure. Second, methacrylic anhydride and a photoinitiator were introduced into the hydrogel system to make the material photocurable during 3D printing. Finally, lyophilization was used to further enhance mechanical properties and prolong degradation time. According to the current results, by integrating photocuring 3D printing and lyophilization techniques, gelatin and hyaluronic acid were successfully fabricated into human ear- and nose-shaped scaffolds, and both scaffolds achieved shape similarity levels over 90% compared with the original digital models. The scaffolds with 50% infill density achieved proper internal pore structure suitable for cell distribution, adhesion, and proliferation. Besides, lyophilization further enhanced mechanical strength of the 3D-printed hydrogel and slowed its degradation rate matching to cartilage regeneration. Most importantly, the scaffolds combined with chondrocytes successfully regenerated mature cartilage with typical lacunae structure and cartilage-specific extracellular matrixes both in vitro and in the autologous goat model. The current study established novel scaffold-fabricated strategies for native polymers and provided a novel natural 3D scaffold with satisfactory outer shape, pore structure, mechanical strength, degradation rate, and weak immunogenicity for cartilage regeneration.

Introduction: Herniation of the nucleus pulposus (NP) because of defects in the annulus fibrosus (AF) is a well-known cause of low back pain. Defects in the AF thus remain a surgical challenge, and efforts have been made to develop new techniques for closure and repair. In this study, we developed an electrospun aligned nanoyarn scaffold (AYS) and nanoyarn/three-dimensional porous nanofibrous hybrid scaffold (HS) for AF tissue engineering., Methods: The AYS was fabricated via conjugated electrospinning, while the aligned nanofibrous scaffold (AFS) was prepared by traditional electrospinning as a baseline scaffold. The HS was constructed by freeze-drying and cross-linking methods. Scanning electron microscopy and mechanical measurement were used to characterize the properties of these scaffolds. Bone marrow derived mesenchymal stem cells (BMSCs) were seeded on scaffolds, and cell proliferation was determined by CCK-8 assay, while cell infiltration and differentiation were assessed by histological measurement and quantitative real-time polymerase chain reaction, respectively., Results: Morphological measurements showed that AYS presented a relatively better three-dimensional structure with larger pore sizes, higher porosity, and better fibers' alignment compared to AFS. Mechanical testing demonstrated that the tensile property of AFS and AYS was qualitatively similar to the native AF tissue, albeit to a lesser extent. When BMSCs were seeded and cultured on these scaffolds, the number of cells cultured on HS and AYS was found to be significantly higher than that on AFS and culture plate after 7 days of culture ( P <0.05). In addition, cell infiltration was significantly higher in HS when compared with AFS and AYS ( P <0.05). A part of BMSCs ingressed into the inner part of AYS upon long-term in vitro culture. No significant difference was observed between AFS and AYS in terms of the median infiltration depth ( P >0.05). BMSCs seeded on AYS demonstrated an increased expression of COL1A1 , while the expression levels of SOX-9 , COL2A1 , and Aggrecan were higher in HS compared to other scaffolds ( P <0.05)., Conclusion: These findings indicate that HS makes a proper scaffold for the AF tissue engineering as it replicates the axial compression and tensile property of AF, thereby providing a better platform for cell infiltration and cell-scaffold interaction., Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Electrospinning is a versatile and convenient technology to generate nanofibers suitable for tissue engineering. However, the low production rate of traditional needle electrospinning hinders its applications. Needleless electrospinning is a potential strategy to promote the application of electrospun nanofiber in various fields. In this study, disc-electrospinning (one kind of needleless electrospinning) was conducted to produce poly(ε-caprolactone)/gelatin (PCL/GT) scaffolds of different structure, namely the nanoscale structure constructed by nanofiber and multiscale structure consisting of nanofiber and microfiber. It was found that, due to the inhomogeneity of PCL/GT solution, disc-electrospun PCL-GT scaffold presented multiscale structure with larger pores than that of the acid assisted one (PCL-GT-A). Scanning electron microscopy images indicated the PCL-GT scaffold was constructed by nanofibers and microfibers. Mouse fibroblasts and rat bone marrow stromal cells both showed higher proliferation rates on multiscale scaffold than nanoscale scaffolds. It was proposed that the nanofibers bridged between the microfibers enhanced cell adhesion and spreading, while the large pores on the three dimensional (3D) PCL-GT scaffold provide more effective space for cells to proliferate and migrate. However, the uniform nanofibers and densely packed structure in PCL-GT-A scaffold limited the cells on the surface. This study demonstrated the potential of disc-electrospun PCL-GT scaffold containing nanofiber and microfiber for 3D tissue regeneration., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Fabrication of 3D scaffold to mimic the nanofibrous structure of the nature extracellular matrix (ECM) with appropriate mechanical properties and excellent biocompatibility, remain an important technical challenge in tissue engineering. The present study reports the strategy to fabricate a 3D nanofibrous scaffold with similar structure to collagen in ECM by combining electrospinning and freeze-drying technique. With the technique reported here, a nanofibrous structure scaffold with hydrophilic and superabsorbent properties can be readily prepared by Gelatin and Polylactic acid (PLA). In wet state the scaffold also shows a super-elastic property, which could bear a compressive strain as high as 80% and recovers its original shape afterwards. Moreover, after 6 days of culture, L-929 cells grow, proliferate and infiltrated into the scaffold. The results suggest that this 3D nanofibrous scaffold would be promising for varied field of tissue engineering application., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Restenosis caused by thrombopoiesis is one of the biggest hinders of endovascular stent-graft used in small-diameter vessels. Rapid endothelialization of the lumen of stent is a promising approach to prevent thrombosis. In this study, we aimed at loading heparin, a potent anticoagulants, and vascular endothelial growth factor (VEGF) into the core of poly(L-lactide-co-caprolactone) nanofiber via emulsion electrospinning. The nanofiber was covered on the stent and applied in the treatment of vascular diseases such as aneurysm. The morphologies of the emulsion electrospun nanofibers and core--shell structure were observed by scanning electron microscope and laser scanning confocal microscope. The release profiles of heparin and VEGF, degradation rate of nanofiber mats and cell proliferation in vitro were investigated. It was found that the release of both heparin and VEGF from the nanofiber lasted for more than 30 days without serious initial burst release. The degradation rate of nanofiber mats containing heparin and VEGF was faster than that of pure PLCL nanofiber mats. Moreover, the released VEGF could promote the proliferation of Pig iliac endothelial cells (PIECs) cultured on the nanofiber mat, which was of great benefit to stent endothelialization. The results of digital subtraction angiography (DSA) follow-up indicated the aneurysm was obliterated by separating the aneurysm dome from the blood circulation and the parent artery kept long-term patency. Results of the study demonstrated that the heparin and VEGF loaded nanofiber could provide an approach to fabricate covered stent-graft with properties of anticoagulation and induction of rapid endothelialization.

Electrospinning has been widely used in fabrication of tissue engineering scaffolds. Currently, most of the electrospun nanofibers performed like a conventional two-dimensional (2D) membrane, which hindered their further applications. Moreover, the low production rate of the traditional needle-electrospinning (NE) also limited the commercialization. In this article, disc-electrospinning (DE) was utilized to fabricate a three-dimensional (3D) scaffold consisting of porous macro/nanoscale fibers. The morphology of the porous structure was investigated by scanning electron microscopy images, which showed irregular pores of nanoscale spreading on the surface of DE polycaprolactone (PCL) fibers. Protein adsorption assessment illustrated the porous structure could significantly enhance proteins pickup, which was 55% higher than that of solid fiber scaffolds. Fibroblasts were cultured on the scaffold. The results demonstrated that DE fiber scaffold could enhance initial cell attachment. In the 7 days of culture, fibroblasts grew faster on DE fiber scaffold in comparison with solid fiber, solvent cast (SC) film and TCP. Fibroblasts on DE fibers showed a stretched shape and integrated with the porous surface tightly. Cells were also found to migrate into the DE scaffold up to 800μm. Results supported the use of DE PCL fibers as a 3D tissue engineering scaffold in soft tissue regeneration., (Copyright © 2014 Elsevier B.V. All rights reserved.)

A novel electrospun nanoyarn scaffold, aimed to improve cell infiltration and vascularization, as well as guide cell behaviors by its biomimetic structure, was fabricated for tissue engineering. Electrospun nanofibers were deposited and twisted into yarns in a water vortex before collecting on a rotating mandrel to form a nanoyarn scaffold. Field emission-scanning electronic microscope (FE-SEM) images revealed that the scaffold, composed of aligned nanoyarns (24 micro m) which were composed of a bundle of nanofibers, created a porous structure which may be conducive to cellular infiltration. Thus, we hypothesized that the biomimetic nanoyarn will have a positive influence on cell proliferation and morphology. Pig iliac endothelial cells (PIECs) and MC3T3-E1 pre-osteoblastic cells cultured on the nanoyarn scaffolds showed significantly higher proliferation rates than that on traditional electrospun nanofiber scaffolds. Histological analysis demonstrated that cells infiltrate throughout the nanoyarn scaffolds over a 10-day period, however, no cell infiltration was observed on the nanofiber scaffolds. Moreover, confocal microscopy images indicated that both PIECs and MC3T3-E1 pre-osteoblastic cells cultured on the nanoyarn scaffolds exhibit an extremely elongated morphology compared to the flattened morphology when cells were cultured on electrospun nanofiber scaffolds or tissue culture plates. Furthermore, complex capillary-like structures were observed when PIECs cultured on the nanoyarn scaffold for 7 days, indicating that the nanoyarns provide templates and topographical cues for the assembly of PIECs and the promotion of a capillary network in vitro. In conclusion, the positive cellular interactions on the nanoyarn scaffold demonstrate potential application for use in tissue engineering.

A porous scaffold was prepared by gelatin groove fibers for cartilage tissue engineering. The morphology of groove fibers and porous scaffolds were observed by scanning electron microscopy (SEM). The water absorption property of scaffolds was tested which demonstrated values as high as 1187%. The compressive mechanical property of scaffolds was also evaluated. In wet state, this scaffold exhibited elastic behaviour, and could bear 100 cycles compressive fatigue test. Moreover, this scaffold could promote rat chondrocyte and bone marrow mesenchymal stem cells (BMSC) proliferation. The findings indicate that such scaffold could be valuable candidates for cartilage tissue engineering. [ABSTRACT FROM AUTHOR]

• Cartilage decellularized matrix (CDM) is processed into inks for 3D printing. • CDM-based scaffolds with controlled 3D shape and pore structure are obtained. • Fibers can improve the mechanical property of 3D-printed CDM scaffolds. • 3D-printed fiber-reinforced CDM scaffolds exhibit elasticity in wet condition. • Fiber-reinforced CDM scaffolds can repair articular cartilage defects in rabbits. Cartilage decellularized matrix (CDM) is considered a promising biomaterial for fabricating cartilage tissue engineering scaffolds. An ideal CDM-based scaffold should possess customizable 3D shape for complex tissue regeneration and proper pore size for cell infiltration, as well as provide mechanical support for cell growth. 3D printing is an efficiently technique for preparing customizable 3D scaffolds, however, fabricating CDM-based 3D-printed scaffolds with customizable shapes, proper pore structure and satisfactory mechanical properties remains a challenge. In the current study, to achieve customizable CDM-based 3D scaffolds, CDM was successfully processed into inks suitable for 3D printing. Further, the poor mechanics of CDM-based scaffolds were significantly improved by adding electrospinning fiber into the CDM-based inks for 3D printing. Importantly, the 3D-printed electrospinning fiber-reinforced CDM-based scaffold presented good biocompatibility and can enhance repair articular cartilage defects in rabbits. The current study provides a novel strategy for printing electrospinning fiber-reinforced CDM-based scaffolds for tissue regeneration. [ABSTRACT FROM AUTHOR]

The fabrication of three-dimensional (3D) electrospun fibrous scaffolds with customizable shapes and large pores is a challenging task. In this study, for the first time, one-dimensional (1D) gelatin/poly (lactic- co -glycolic acid) (PLGA) electrospun fibers were processed into inks suitable for 3D printing. By combining 3D printing and freeze drying, electrospun fiber-based inks were successfully fabricated into 3D-printed scaffolds (3DP) with precisely controlled shapes and large pores, in addition to fibrous surface morphologies similar to that of a native extracellular matrix (ECM). The 3DP exhibited good elasticity and water-induced shape memory, and was found to be superior to 3D-printed scaffolds fabricated using pure gelatin fibers and freeze-shaped scaffolds fabricated using non-fibrous gelatin/PLGA powder. Moreover, 3DP combined with chondrocytes achieved satisfactory cartilage regeneration in vivo. The novel strategy of 3D printing electrospun fibers established in this study provides a research model for the design and fabrication of multiple scaffolds for various tissue regeneration applications. Unlabelled Image • Electrospun fibers were processed into three-dimensional inks for the first time. • Fiber scaffolds with controlled shapes and large pores were successfully fabricated. • Three-dimensional printed fiber scaffolds exhibited elastic property in the wet condition. • Three-dimensional fiber scaffolds combined with chondrocytes achieved satisfactory cartilage regeneration in vivo. [ABSTRACT FROM AUTHOR]

An electrospun-aligned nanoyarn-reinforced nanofibrous scaffold (NRS) was developed for tendon tissue engineering to improve mechanical strength and cell infiltration. The novel scaffold composed of aligned nanoyarns and random nanofibers was fabricated via electrospinning using a two-collector system. The aim of the present study was to investigate three different types of electrospun scaffolds (random nanofibrous scaffold, aligned nanofibrous scaffold and NRS) based on silk fibroin (SF) and poly( l -lactide- co -caprolactone) blends. Morphological analysis demonstrated that the NRS composed of aligned nanoyarns and randomly distributed nanofibers formed a 3D microstructure with relatively large pore sizes and high porosity. Biocompatibility analysis revealed that bone marrow-derived mesenchymal stem cells exhibited a higher proliferation rate when cultured on the NRS compared with the other scaffolds. The mechanical testing results indicated that the tensile properties of the NRS were reinforced in the direction parallel to the nanoyarns and satisfied the mechanical requirements for tendon repair. In addition, cell infiltration was significantly enhanced on the NRS. In conclusion, with its improved porosity and appropriate mechanical properties, the developed NRS shows promise for tendon tissue engineering applications. [ABSTRACT FROM AUTHOR]

• Cartilage decellularized matrix was processed into hydrogel (CDEM-pHA). • CDEM-pHA was injectable and photo-crosslinkable. • CDEM-pHA combined with chondrocytes formed mature cartilage in vivo. Cartilage decellularized extracellular matrix (CDEM) is a promising biomaterial for preparing tissue engineering scaffolds, and CDEM-based hydrogels constitute an ideal choice for repairing cartilage damage. In this study, CDEM powders and photo-responsive hyaluronic acid (pHA) were successfully fabricated into injectable and photo-crosslinkable hydrogel (CDEM-pHA). The rheological properties of CDEM-pHA indicated that CDEM-pHA exhibited shear-thinning behavior, and the storage modulus of the hydrogel increased with increasing UV irradiation. Chondrocytes were loaded into CDEM-pHA and implanted into the subcutaneous tissue of nude mice for eight weeks; the results indicated that CDEM-pHA combined with chondrocytes successfully regenerated mature cartilage in vivo. This study established a novel strategy for preparing CDEM-based hydrogel for cartilage regeneration. [ABSTRACT FROM AUTHOR]