Scaffold-Based Tissue Engineering Strategies for Osteochondral Repair

Over centuries, several advances have been made in osteochondral (OC) tissue engineering to regenerate more biomimetic tissue. As an essential component of tissue engineering, scaffolds provide structural and functional support for cell growth and differentiation. Numerous scaffold types, such as porous, hydrogel, fibrous, microsphere, metal, composite and decellularized matrix, have been reported and evaluated for OC tissue regeneration in vitro and in vivo, with respective advantages and disadvantages. Unfortunately, due to the inherent complexity of organizational structure and the objective limitations of manufacturing technologies and biomaterials, we have not yet achieved stable and satisfactory effects of OC defects repair. In this review, we summarize the complicated gradients of natural OC tissue and then discuss various osteochondral tissue engineering strategies, focusing on scaffold design with abundant cell resources, material types, fabrication techniques and functional properties.

Apigenin Induces Browning in White Adipocytes Mediated by VEGF-PRDM16 Signaling.

The white adipose tissues are metabolically inert which results in deranged biological signalling disorders resulting in obesity. Lack of vascularisation in these tissues is mainly responsible to make them metabolically inert. Not much work has been done in this direction to understand the role of angiogenesis in white adipocytes metabolism. In the present study, we evaluated the effect of angiogenic modulator in modulating the metabolism in white adipocyte. Nutraceuticals apigenin (Apg) was employed as angiogenic modulator. The results indicated that promoting angiogenesis by Apg enhanced the de novo differentiation and trans-differentiation of white adipocyte into brown like phenotype by triggering vascular endothelial growth factor A. Cross talk between endothelial and adipocytes were observed in co-culture studies. The metabolic shift in white adipocytes was observed to be due to the upregulation of PRDM16 cascade. The study provides new insights for inducing metabolic shift in white adipocytes by modulation of angiogenesis in white adipocyte to trigger browning for the treatment of obesity. Further the study opens scopes for development of medical devices for obese subjects, an area that needs to be addressed specifically with reference to soft tissue engineering as commercial soft tissue engineering scaffolds does not suit the obese patients.

Liquid-Assisted Electrospinning Three-Dimensional Polyacrylonitrile Nanofiber Crosslinked with Chitosan

Electrospinning has become a popular nanotechnology for the fabrication of tissue engineering scaffolds, which can precisely regulate fiber diameter and microstructure. Herein, we have prepared a three-dimensional polyacrylonitrile (PAN) nanofiber by liquid-assisted electrospinning. The spacing between PAN nanofibers can reach to 15-20 μm, as the uniform internally connected pore structure can be formed, through the regulation of parameters. Furthermore, the chitosan attached to the as-prepared nanofibers gives the material antibacterial effect and increases its biocompatibility. Meanwhile, the special structure of chitosan also provides the possibility for further loading drugs in dressings in the future. This newly developed nanocomposite seems to be highly suitable for wound healing due to its unique properties of biodegradability, biocompatibility, and antimicrobial effectiveness.

Periodontal Bifunctional Biomaterials: Progress and Perspectives

Periodontitis is a chronic infectious disease that destroys periodontal supportive tissues and eventually causes tooth loss. It is attributed to microbial and immune factors. The goal of periodontal therapy is to achieve complete alveolar bone regeneration while keeping inflammation well-controlled. To reach this goal, many single or composite biomaterials that produce antibacterial and osteogenic effects on periodontal tissues have been developed, which are called bifunctional biomaterials. In this review, we summarize recent progress in periodontal bifunctional biomaterials including bioactive agents, guided tissue regeneration/guided bone regeneration (GTR/GBR) membranes, tissue engineering scaffolds and drug delivery systems and provide novel perspectives. In conclusion, composite biomaterials have been greatly developed and they should be chosen with care due to the risk of selection bias and the lack of evaluation of the validity of the included studies.

Small Ruminant Models for Articular Cartilage Regeneration by Scaffold-Based Tissue Engineering

Animal models play an important role in preclinical studies, especially in tissue engineering scaffolds for cartilage repair, which require large animal models to verify the safety and effectiveness for clinical use. The small ruminant models are most widely used in this field than other large animals because they are cost-effective, easy to raise, not to mention the fact that the aforementioned animal presents similar anatomical features to that of humans. This review discusses the experimental study of tissue engineering scaffolds for knee articular cartilage regeneration in small ruminant models. Firstly, the selection of these scaffold materials and the preparation process in vitro that have been already used in vivo are briefly reviewed. Moreover, the major factors influencing the rational design and the implementation as well as advantages and limitations of small ruminants are also demonstrated. As regards methodology, this paper applies principles and methods followed by most researchers in the process of experimental design and operation of this kind. By summarizing and comparing different therapeutic concepts, this paper offers suggestions aiming to increase the effectiveness of preclinical research using small ruminant models and improve the process of developing corresponding therapies.

Environmental Impact for 3D Bone Tissue Engineering Scaffolds Life Cycle: An Assessment

With the development of additive manufacturing technology, 3D bone tissue engineering scaffolds have evolved. Bone tissue engineering is one of the techniques for repairing bone abnormalities caused by a variety of circumstances, such as injuries or the need to support damaged sections. Many bits of research have gone towards developing 3D bone tissue engineering scaffolds all across the world. The assessment of the environmental impact, on the other hand, has received less attention. As a result, the focus of this study is on developing a life cycle assessment (LCA) model for 3D bone tissue engineering scaffolds and evaluating potential environmental impacts. One of the methodologies to evaluating a complete environmental impact assessment is life cycle assessment (LCA). The cradle-to-grave method will be used in this study, and GaBi software was used to create the analysis for this study. Previous research on 3D bone tissue engineering fabrication employing poly(ethylene glycol) diacrylate (PEGDA) soaked in dimethyl sulfoxide (DMSO), and diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO) as a photoinitiator will be reviewed. Meanwhile, digital light processing (DLP) 3D printing is employed as the production technique. The GaBi program and the LCA model developed to highlight the potential environmental impact. This study shows how the input and output of LCA of 3D bone tissue engineering scaffolds might contribute to environmental issues such as air, freshwater, saltwater, and industrial soil emissions. The emission contributing to potential environmental impacts comes from life cycle input, electricity and transportation consumption, manufacturing process, and material resources. The results from this research can be used as an indicator for the researcher to take the impact of the development of 3D bone tissue engineering on the environment seriously.

Forskolin-Loaded Halloysite Nanotubes as Osteoconductive Additive for the Biopolymer Tissue Engineering Scaffolds

Here we report the use of forskolin-modified halloysite nanotubes (HNTs) as a dopant for biopolymer porous hydrogel scaffolds to impart osteoinductive properties. Forskolin is a labdane diterpenoid isolated from the Indian Coleus plant. This small molecule is widely used as a supplement in molecular biology for cell differentiation. It has been reported in some earlier publications that forskolin can activate osteodifferentiation process by cyclic adenosine monophosphate (c-AMP) signalling activation in stem cells. In presented study it was demonstrated that forskolin release from halloysite-doped scaffolds induced the osteodifferentiation of equine mesenchymal stem cells (MSCs) in vitro without addition of any specific growth factors. The reinforcement of mechanical properties of cells and intercellular space during the osteodifferentiation was demonstrated using atomic force microscopy (AFM). These clay-doped scaffolds may find applications to accelerate the regeneration of horse bone defects by inducing the processes of osteodifferentiation of endogenous MSCs.

Poly(L-lactic acid) Reinforced with Hydroxyapatite and Tungsten Disulfide Nanotubes

Poly(L-lactic acid) (PLLA) is a biocompatible, biodegradable, and semi-crystalline polymer with numerous applications including food packaging, medical implants, stents, tissue engineering scaffolds, etc. Hydroxyapatite (HA) is the major component of natural bone. Conceptually, combining PLLA and HA could produce a bioceramic suitable for implants and bone repair. However, this nanocomposite suffers from poor mechanical behavior under tensile strain. In this study, films of PLLA and HA were prepared with small amounts of nontoxic WS2 nanotubes (INT-WS2). The structural aspects of the films were investigated via electron microscopy, X-ray diffraction, Raman microscopy, and infrared absorption spectroscopy. The mechanical properties were evaluated via tensile measurements, micro-hardness tests, and nanoindentation. The thermal properties were investigated via differential scanning calorimetry. The composite films exhibited improved mechanical and thermal properties compared to the films prepared from the PLLA and HA alone, which is advantageous for medical applications.