Design, Fabrication, and Characterization of a Multimodal Reconfigurable Bioreactor for Bone Tissue Engineering

Monitoring Cell Cytoskeleton Variations upon Piezoelectric Stimulation: Implications for the Immune System

Piezoelectric stimulation can have a significant impact on different cellular functions with possible applications in several fields, such as regenerative medicine, cancer therapy, and immunoregulation. For example, piezoelectric stimulation has been shown to modulate cytoskeleton variations: the implications of this effect range from the regulation of migration and invasion of cancer cells to the activation of pro- or anti-inflammatory phenotypes in immune cells. In this chapter, we will present different methodologies to evaluate cytoskeleton variations, focusing on modifications on f-/g-actin ratio and on the migration and invasion ability of tumor cells.

JANUS: an open-source 3D printable perfusion bioreactor and numerical model-based design strategy for tissue engineering

Bioreactors have been employed in tissue engineering to sustain longer and larger cell cultures, managing nutrient transfer and waste removal. Multiple designs have been developed, integrating sensor and stimulation technologies to improve cellular responses, such as proliferation and differentiation. The variability in bioreactor design, stimulation protocols, and cell culture conditions hampered comparison and replicability, possibly hiding biological evidence. This work proposes an open-source 3D printable design for a perfusion bioreactor and a numerical model-driven protocol development strategy for improved cell culture control. This bioreactor can simultaneously deliver capacitive-coupled electric field and fluid-induced shear stress stimulation, both stimulation systems were validated experimentally and in agreement with numerical predictions. A preliminary in vitro validation confirmed the suitability of the developed bioreactor to sustain viable cell cultures. The outputs from this strategy, physical and virtual, are openly available and can be used to improve comparison, replicability, and control in tissue engineering applications.

Bilayer scaffolds/membranes for bone tissue engineering applications: A systematic review

OBJECTIVE

This systematic review evaluates the purpose, materials, physio-mechanical, and biological effects of bilayer scaffolds/membranes used for bone tissue engineering applications.

METHODS

A comprehensive electronic search of English-language literature from 2012 to October 2022 was conducted in PubMed, Scopus, ScienceDirect, and Google Scholar online databases according to the PRISMA 2020 guidelines. The quality of animal studies was evaluated through the SYRCLE's risk of bias tool.

RESULTS

A total of 77 studies were sought for retrieval, and 39 studies met the inclusion criteria. According to the synthesis results, most bilayers had a dense barrier layer that prevented connective tissue penetration and a loose osteogenic layer that supported cell migration and osteogenesis. PLGA, PCL, and chitosan were the most common polymers in the barrier layers, while the most utilized polymers in osteogenic layers were PLGA and gelatin. Electrospinning and solvent casting were the most common fabrication methods to design the bilayer structures. Many studies reported higher biological results for bilayers compared to their single layers. Also, fabricated bilayers' in vitro osteogenesis and in vivo new bone formation were significantly superior or at least comparable to the frequently used commercial membranes.

CONCLUSION

1) Bilayers with two distinct layers and different materials, porosities, mechanical properties, and biological behavior can significantly improve heterogeneous bone regeneration; 2) the addition of ceramics and/or drugs to the osteogenic layer enhances the osteogenic properties of the bilayers; 3) fabrication method and pore size of the layers play an important role in determining the mechanical and biological behavior of them.

CAM Model: Intriguing Natural Bioreactor for Sustainable Research and Reliable/Versatile Testing

We are witnessing the revival of the CAM model, which has already used been in the past by several researchers studying angiogenesis and anti-cancer drugs and now offers a refined model to fill, in the translational meaning, the gap between in vitro and in vivo studies. It can be used for a wide range of purposes, from testing cytotoxicity, pharmacokinetics, tumorigenesis, and invasion to the action mechanisms of molecules and validation of new materials from tissue engineering research. The CAM model is easy to use, with a fast outcome, and makes experimental research more sustainable since it allows us to replace, reduce, and refine pre-clinical experimentation ("3Rs" rules). This review aims to highlight some unique potential that the CAM-assay presents; in particular, the authors intend to use the CAM model in the future to verify, in a microenvironment comparable to in vivo conditions, albeit simplified, the angiogenic ability of functionalized 3D constructs to be used in regenerative medicine strategies in the recovery of skeletal injuries of critical size (CSD) that do not repair spontaneously. For this purpose, organotypic cultures will be planned on several CAMs set up in temporal sequences, and a sort of organ model for assessing CSD will be utilized in the CAM bioreactor rather than in vivo.

Integrating physicomechanical and biological strategies for BTE: biomaterials-induced osteogenic differentiation of MSCs

Large bone defects are a major global health concern. Bone tissue engineering (BTE) is the most promising alternative to avoid the drawbacks of autograft and allograft bone. Nevertheless, how to precisely control stem cell osteogenic differentiation has been a long-standing puzzle. Compared with biochemical cues, physicomechanical stimuli have been widely studied for their biosafety and stability. The mechanical properties of various biomaterials (polymers, bioceramics, metal and alloys) become the main source of physicomechanical stimuli. By altering the stiffness, viscoelasticity, and topography of materials, mechanical stimuli with different strengths transmit into precise signals that mediate osteogenic differentiation. In addition, externally mechanical forces also play a critical role in promoting osteogenesis, such as compression stress, tensile stress, fluid shear stress and vibration, etc. When exposed to mechanical forces, mesenchymal stem cells (MSCs) differentiate into osteogenic lineages by sensing mechanical stimuli through mechanical sensors, including integrin and focal adhesions (FAs), cytoskeleton, primary cilium, ions channels, gap junction, and activating osteogenic-related mechanotransduction pathways, such as yes associated proteins (YAP)/TAZ, MAPK, Rho-GTPases, Wnt/β-catenin, TGFβ superfamily, Notch signaling. This review summarizes various biomaterials that transmit mechanical signals, physicomechanical stimuli that directly regulate MSCs differentiation, and the mechanical transduction mechanisms of MSCs. This review provides a deep and broad understanding of mechanical transduction mechanisms and discusses the challenges that remained in clinical translocation as well as the outlook for the future improvements.

Development of a Scaffold-on-a-Chip Platform to Evaluate Cell Infiltration and Osteogenesis on the 3D-Printed Scaffold for Bone Regeneration

Developing a scaffold for efficient and functional bone regeneration remains challenging. To accomplish this goal, a "scaffold-on-a-chip" device was developed as a platform to aid with the evaluation process. The device mimics a microenvironment experienced by a transplanted bone scaffold. The device contains a circular space at the center for scaffold insert and microfluidic channel that encloses the space. Such a design allows for monitoring of cell behavior at the blood-scaffold interphase. MC3T3-E1 cells were cultured with three different types of scaffold inserts to test its capability as an evaluation platform. Cellular behaviors, including migration, morphology, and osteogenesis with each scaffold, were analyzed through fluorescence images of live/dead assay and immunocytochemistry. Cellular behaviors, such as migration, morphology, and osteogenesis, were evaluated. The results revealed that our platform could effectively evaluate the osteoconductivity and osteoinductivity of scaffolds with various properties. In conclusion, our proposed platform is expected to replace current in vivo animal models as a highly relevant in vitro platform and can contribute to the fundamental study of bone regeneration.

Macropore Regulation of Hydroxyapatite Osteoinduction via Microfluidic Pathway

Macroporous characteristics have been shown to play a key role in the osteoinductivity of hydroxyapatite ceramics, but the physics underlying the new bone formation and distribution in such scaffolds still remain elusive. The work here has emphasized the osteoinductive capacity of porous hydroxyapatite scaffolds containing different macroporous sizes (200–400 μm, 1200–1500 μm) and geometries (star shape, spherical shape). The assumption is that both the size and shape of a macropore structure may affect the microfluidic pathways in the scaffolds, which results in the different bone formations and distribution. Herein, a mathematical model and an animal experiment were proposed to support this hypothesis. The results showed that the porous scaffolds with the spherical macropores and large pore sizes (1200–1500 μm) had higher new bone production and more uniform new bone distribution than others. A finite element analysis suggested that the macropore shape affected the distribution of the medium–high velocity flow field, while the macropore size effected microfluid speed and the value of the shear stress in the scaffolds. Additionally, the result of scaffolds implanted into the dorsal muscle having a higher new bone mass than the abdominal cavity suggested that the mechanical load of the host tissue could play a key role in the microfluidic pathway mechanism. All these findings suggested that the osteoinduction of these scaffolds depends on both the microfluid velocity and shear stress generated by the macropore size and shape. This study, therefore, provides new insights into the inherent osteoinductive mechanisms of bioceramics, and may offer clues toward a rational design of bioceramic scaffolds with improved osteoinductivity.

Biomaterials for Tissue Engineering Applications and Current Updates in the Field: A Comprehensive Review

Tissue engineering has emerged as an interesting field nowadays; it focuses on accelerating the auto-healing mechanism of tissues rather than organ transplantation. It involves implanting an In Vitro cultured initiative tissue or a scaffold loaded with tissue regenerating ingredients at the damaged area. Both techniques are based on the use of biodegradable, biocompatible polymers as scaffolding materials which are either derived from natural (e.g. alginates, celluloses, and zein) or synthetic sources (e.g. PLGA, PCL, and PLA). This review discusses in detail the recent applications of different biomaterials in tissue engineering highlighting the targeted tissues besides the in vitro and in vivo key findings. As well, smart biomaterials (e.g. chitosan) are fascinating candidates in the field as they are capable of elucidating a chemical or physical transformation as response to external stimuli (e.g. temperature, pH, magnetic or electric fields). Recent trends in tissue engineering are summarized in this review highlighting the use of stem cells, 3D printing techniques, and the most recent 4D printing approach which relies on the use of smart biomaterials to produce a dynamic scaffold resembling the natural tissue. Furthermore, the application of advanced tissue engineering techniques provides hope for the researchers to recognize COVID-19/host interaction, also, it presents a promising solution to rejuvenate the destroyed lung tissues.