Novel hiPSC-based tri-culture for pre-vascularization of calcium phosphate scaffold to enhance bone and vessel formation

Enhancing bone tissue engineering using iron nanoparticles and magnetic fields: A focus on cytomechanics and angiogenesis in the chicken egg chorioallantoic membrane model

AIM

To evaluate the potential of iron nanoparticles (FeNPs) in conjunction with magnetic fields (MFs) to enhance osteoblast cytomechanics, promote cell homing, bone development activity, and antibacterial capabilities, and to assess their in vivo angiogenic viability using the chicken egg chorioallantoic membrane (CAM) model.

SETTINGS AND DESIGN

Experimental study conducted in a laboratory setting to investigate the effects of FeNPs and MFs on osteoblast cells and angiogenesis using a custom titanium (Ti) substrate coated with FeNPs.

MATERIALS AND METHODS

A custom titanium (Ti) was coated with FeNPs. Evaluations were conducted to analyze the antibacterial properties, cell adhesion, durability, physical characteristics, and nanoparticle absorption associated with FeNPs. Cell physical characteristics were assessed using protein markers, and microscopy, CAM model, was used to quantify blood vessel formation and morphology to assess the FeNP-coated Ti's angiogenic potential. This in vivo study provided critical insights into tissue response and regenerative properties for biomedical applications.

STATISTICAL ANALYSIS

Statistical analysis was performed using appropriate tests to compare experimental groups and controls. Significance was determined at P < 0.05.

RESULTS

FeNPs and MFs notably improved osteoblast cell mechanical properties facilitated the growth and formation of new blood vessels and bone tissue and promoted cell migration to targeted sites. In the group treated with FeNPs and exposed to MFs, there was a significant increase in vessel percentage area (76.03%) compared to control groups (58.11%), along with enhanced mineralization and robust antibacterial effects (P < 0.05).

CONCLUSION

The study highlights the promising potential of FeNPs in fostering the growth of new blood vessels, promoting the formation of bone tissue, and facilitating targeted cell migration. These findings underscore the importance of further investigating the mechanical traits of FeNPs, as they could significantly advance the development of effective bone tissue engineering techniques, ultimately enhancing clinical outcomes in the field.

Cell-based mechanisms and strategies of co-culture system both in vivo and vitro for bone tissue engineering

The lack of a functional vascular supply has been identified as a major challenge limiting the clinical introduction of stem cell-based bone tissue engineering (BTE) for the repair of large-volume bone defects (LVBD). Various approaches have been explored to improve the vascular supply in tissue-engineered constructs, and the development of strategies that could effectively induce the establishment of a functional vascular supply has become a major goal of BTE research. One of the state-of-the-art methods is to incorporate both angiogenic and osteogenic cells in co-culture systems. This review clarifies the key concepts involved, summarises the cell types and models used to date, and systematically evaluates their performance. We also discuss the cell-to-cell communication between these two cell types and the strategies explored in BTE constructs with angiogenic and osteogenic cells to optimise their functions. In addition, we outline unresolved issues and remaining obstacles that need to be overcome for further development in this field and eventual successful repair of LVBD.

The Therapeutic Potential of Pericytes in Bone Tissue Regeneration

Pericytes, as perivascular cells, are present in all vascularized organs and tissues, and they actively interact with endothelial cells in capillaries and microvessels. Their involvement includes functions like blood pressure regulation, tissue regeneration, and scarring. Studies have confirmed that pericytes play a crucial role in bone tissue regeneration through direct osteodifferentiation processes, paracrine actions, and vascularization. Recent preclinical and clinical experiments have shown that combining perivascular cells with osteogenic factors and tissue-engineered scaffolds can be therapeutically effective in restoring bone defects. This approach holds promise for addressing bone-related medical conditions. In this review, we have emphasized the characteristics of pericytes and their involvement in angiogenesis and osteogenesis. Furthermore, we have explored recent advancements in the use of pericytes in preclinical and clinical investigations, indicating their potential as a therapeutic resource in clinical applications.

Hollow channels scaffold in bone regenerative: a review

Bone substitute materials have been extensively used for bone regeneration over the past 50 years. The development of novel materials, fabrication technologies and the incorporation and release of regenerative cytokines, growth factors, cells and antimicrobials has been driven by the rapid development in the field of additive manufacturing technology. There are still however, significant challenges that need addressing, including ways to better mediate the rapid vascularization of bone scaffolds to enhance subsequent regeneration and osteogenesis. Increasing construct porosity can accelerate the development of blood vessels in the scaffold, but doing so also weakens the constructs mechanical properties. A novel design for promoting rapid vascularization is to fabricate custom-made hollow channels as bone scaffolds. Summarized here are the current developments in hollow channels scaffold, including their biological attributes, physio-chemical properties, and effects on regeneration. An overview of recent developments in scaffold fabrication as they relate to hollow channel constructs and their structural features will be introduced with an emphasis on attributes that enhance new bone and vessel formation. Furthermore, the potential to enhance angiogenesis and osteogenesis by replicating the structure of real bone will be highlighted.

Effects of Metformin Delivery via Biomaterials on Bone and Dental Tissue Engineering

Bone tissue engineering is a promising approach that uses seed-cell-scaffold drug delivery systems to reconstruct bone defects caused by trauma, tumors, or other diseases (e.g., periodontitis). Metformin, a widely used medication for type II diabetes, has the ability to enhance osteogenesis and angiogenesis by promoting cell migration and differentiation. Metformin promotes osteogenic differentiation, mineralization, and bone defect regeneration via activation of the AMP-activated kinase (AMPK) signaling pathway. Bone tissue engineering depends highly on vascular networks for adequate oxygen and nutrition supply. Metformin also enhances vascular differentiation via the AMPK/mechanistic target of the rapamycin kinase (mTOR)/NLR family pyrin domain containing the 3 (NLRP3) inflammasome signaling axis. This is the first review article on the effects of metformin on stem cells and bone tissue engineering. In this paper, we review the cutting-edge research on the effects of metformin on bone tissue engineering. This includes metformin delivery via tissue engineering scaffolds, metformin-induced enhancement of various types of stem cells, and metformin-induced promotion of osteogenesis, angiogenesis, and its regulatory pathways. In addition, the dental, craniofacial, and orthopedic applications of metformin in bone repair and regeneration are also discussed.

Osteoporosis pathogenesis and treatment: existing and emerging avenues

Osteoporotic fractures lead to increased disability and mortality in the elderly population. With the rapid increase in the aging population around the globe, more effective treatments for osteoporosis and osteoporotic fractures are urgently required. The underlying molecular mechanisms of osteoporosis are believed to be due to the increased activity of osteoclasts, decreased activity of osteoblasts, or both, which leads to an imbalance in the bone remodeling process with accelerated bone resorption and attenuated bone formation. Currently, the available clinical treatments for osteoporosis have mostly focused on factors influencing bone remodeling; however, they have their own limitations and side effects. Recently, cytokine immunotherapy, gene therapy, and stem cell therapy have become new approaches for the treatment of various diseases. This article reviews the latest research on bone remodeling mechanisms, as well as how this underpins current and potential novel treatments for osteoporosis.

Biomimicking design of artificial periosteum for promoting bone healing

Background

Periosteum is a vascularized tissue membrane covering the bone surface and plays a decisive role in bone reconstruction process after fracture. Various artificial periosteum has been developed to assist the allografts or bionic bone scaffolds in accelerating bone healing. Recently, the biomimicking design of artificial periosteum has attracted increasing attention due to the recapitulation of the natural extracellular microenvironment of the periosteum and has presented unique capacity to modulate the cell fates and ultimately enhance the bone formation and improve neovascularization.

Methods

A systematic literature search is performed and relevant findings in biomimicking design of artificial periosteum have been reviewed and cited.

Results

We give a systematical overview of current development of biomimicking design of artificial periosteum. We first summarize the universal strategies for designing biomimicking artificial periosteum including biochemical biomimicry and biophysical biomimicry aspects. We then discuss three types of novel versatile biomimicking artificial periosteum including physical-chemical combined artificial periosteum, heterogeneous structured biomimicking periosteum, and healing phase-targeting biomimicking periosteum. Finally, we comment on the potential implications and prospects in the future design of biomimicking artificial periosteum.

Conclusion

This review summarizes the preparation strategies of biomimicking artificial periosteum in recent years with a discussion of material selection, animal model adoption, biophysical and biochemical cues to regulate the cell fates as well as three types of latest developed versatile biomimicking artificial periosteum. In future, integration of innervation, osteochondral regeneration, and osteoimmunomodulation, should be taken into consideration when fabricating multifunctional artificial periosteum.

The Translational Potential of this Article: This study provides a holistic view on the design strategy and the therapeutic potential of biomimicking artificial periosteum to promote bone healing. It is hoped to open a new avenue of artificial periosteum design with biomimicking considerations and reposition of the current strategy for accelerated bone healing.

Human Umbilical Cord Mesenchymal Stem Cells: Current Literature and Role in Periodontal Regeneration

Periodontal disease can cause irreversible damage to tooth-supporting tissues such as the root cementum, periodontal ligament, and alveolar bone, eventually leading to tooth loss. While standard periodontal treatments are usually helpful in reducing disease progression, they cannot repair or replace lost periodontal tissue. Periodontal regeneration has been demonstrated to be beneficial in treating intraosseous and furcation defects to varied degrees. Cell-based treatment for periodontal regeneration will become more efficient and predictable as tissue engineering and progenitor cell biology advance, surpassing the limitations of present therapeutic techniques. Stem cells are undifferentiated cells with the ability to self-renew and differentiate into several cell types when stimulated. Mesenchymal stem cells (MSCs) have been tested for periodontal regeneration in vitro and in humans, with promising results. Human umbilical cord mesenchymal stem cells (UC-MSCs) possess a great regenerative and therapeutic potential. Their added benefits comprise ease of collection, endless source of stem cells, less immunorejection, and affordability. Further, their collection does not include the concerns associated with human embryonic stem cells. The purpose of this review is to address the most recent findings about periodontal regenerative mechanisms, different stem cells accessible for periodontal regeneration, and UC-MSCs and their involvement in periodontal regeneration.

Recent Advances on Cell-Based Co-Culture Strategies for Prevascularization in Tissue Engineering

Currently, the fabrication of a functional vascular network to maintain the viability of engineered tissues is a major bottleneck in the way of developing a more advanced engineered construct. Inspired by vasculogenesis during the embryonic period, the in vitro prevascularization strategies have focused on optimizing communications and interactions of cells, biomaterial and culture conditions to develop a capillary-like network to tackle the aforementioned issue. Many of these studies employ a combination of endothelial lineage cells and supporting cells such as mesenchymal stem cells, fibroblasts, and perivascular cells to create a lumenized endothelial network. These supporting cells are necessary for the stabilization of the newly developed endothelial network. Moreover, to optimize endothelial network development without impairing biomechanical properties of scaffolds or differentiation of target tissue cells, several other factors, including target tissue, endothelial cell origins, the choice of supporting cell, culture condition, incorporated pro-angiogenic factors, and choice of biomaterial must be taken into account. The prevascularization method can also influence the endothelial lineage cell/supporting cell co-culture system to vascularize the bioengineered constructs. This review aims to investigate the recent advances on standard cells used in in vitro prevascularization methods, their co-culture systems, and conditions in which they form an organized and functional vascular network.

The effect of modifying the nanostructure of gelatin fiber scaffolds on early angiogenesisin vitroandin vivo

Early angiogenesis is one of the key challenges in tissue regeneration. Crosslinking mode and fiber diameter are critical factors to affect the adhesion and proliferation of cells. However, whether and how these two factors affect early angiogenesis remain largely unknown. To address the issue, the optimal crosslinking mode and fiber diameter of gelatin fiber membrane for early angiogenesisin vivoandin vitrowere explored in this work. Compared with the post crosslinked gelatin fiber membrane with the same fiber diameter, the 700 nm diameterin situcrosslinked gelatin fiber membrane was found to have smaller roughness (230.67 ± 19 nm) and stronger hydrophilicity (54.77° ± 1.2°), which were suitable for cell growth and adhesion. Moreover, thein situcrosslinked gelatin fiber membrane with a fiber diameter of 1000 nm had significant advantages in early angiogenesis over the two with fiber diameters of 500 and 700 nm by up-regulating the expression of Ang1, VEGF, and integrin-β1. Our findings indicated that thein situcrosslinked gelatin fiber membrane with a diameter of 1000 nm might solve the problem of insufficient blood supply in the early stage of soft tissue regeneration and has broad clinical application prospects in promoting tissue regeneration.

Human Periodontal Ligament Stem Cell and Umbilical Vein Endothelial Cell Co-Culture to Prevascularize Scaffolds for Angiogenic and Osteogenic Tissue Engineering

(1) Background: Vascularization remains a critical challenge in bone tissue engineering. The objective of this study was to prevascularize calcium phosphate cement (CPC) scaffold by co-culturing human periodontal ligament stem cells (hPDLSCs) and human umbilical vein endothelial cells (hUVECs) for the first time; (2) Methods: hPDLSCs and/or hUVECs were seeded on CPC scaffolds. Three groups were tested: (i) hUVEC group (hUVECs on CPC); (ii) hPDLSC group (hPDLSCs on CPC); (iii) co-culture group (hPDLSCs + hUVECs on CPC). Osteogenic differentiation, bone mineral synthesis, and microcapillary-like structures were evaluated; (3) Results: Angiogenic gene expressions of co-culture group were 6–9 fold those of monoculture. vWF expression of co-culture group was 3 times lower than hUVEC-monoculture group. Osteogenic expressions of co-culture group were 2–3 folds those of the hPDLSC-monoculture group. ALP activity and bone mineral synthesis of co-culture were much higher than hPDLSC-monoculture group. Co-culture group formed capillary-like structures at 14–21 days. Vessel length and junction numbers increased with time; (4) Conclusions: The hUVECs + hPDLSCs co-culture on CPC scaffold achieved excellent osteogenic and angiogenic capability in vitro for the first time, generating prevascularized networks. The hPDLSCs + hUVECs co-culture had much better osteogenesis and angiogenesis than monoculture. CPC scaffolds prevacularized via hPDLSCs + hUVECs are promising for dental, craniofacial, and orthopedic applications.

Regulating the mechanics of silk fibroin scaffolds promotes wound vascularization

Functional blood vessels are crucial to wound healing, and faster vascularization means faster tissue repair to some extent. Increasing numbers of pro-vascularization wound coverings are being developed and studied. Moreover, mechanical properties of the extracellular matrix can guide the behaviour of related cells to some degree. Studies have shown that the mechanical range of 1-7 kPa contributes to the differentiation of stem cells into endothelial cells and thus to the process of wound vascularization. Unfortunately, the regulatory mechanics of vascularizing wound coverings have been poorly studied. Silk fibroin (SF) has attracted much attention because of its good biocompatibility, degradability and adjustable mechanical properties. In this paper, silk scaffolds with mechanical properties of 2 kPa and 5.9 kPa were prepared by adjusting the mechanics of silk scaffolds in terms of freezing temperature and aligned structure. The mechanical properties of the 5.9 kPa aligned silk scaffold (ASS) showed good vascularization ability. By adjusting the intermediate conformation and physical structure of Silk fibroin (SF), the mechanical strength of the silk scaffold could be increased, enabling us to better understand the mechanical regulation mode. At the same time, the aligned structure of the aligned silk scaffold (ASS) promoted the migration and proliferation of cells related to wound repair to a certain extent. By adjusting the mechanical properties and physical structure of the material, an aligned silk scaffold with vascularization function was constructed, providing more possibilities for faster wound repair.

Strategies of Prevascularization in Tissue Engineering and Regeneration of Craniofacial Tissues

Craniofacial tissue defects caused by trauma, developmental malformation, or surgery are critical issues of high incidence, which are harmful to physical and psychological health. Transplantation of engineered tissues or biomaterials is a potential method to repair defects and regenerate the craniofacial tissues. Revascularization is essential to ensure the survival and regeneration of the grafts. Since microvessels play a critical role in blood circulation and substance exchange, the pre-establishment of the microvascular network in transplants provides a technical basis for the successful regeneration of the tissue defect. In this study, we reviewed the recent development of strategies and applications of prevascularization in tissue engineering and regeneration of craniofacial tissues. We focused on the cellular foundation of the in vitro prevascularized microvascular network, the cell source for prevascularization, and the strategies of prevascularization. Several key strategies, including coculture, microspheres, three-dimensional printing and microfluidics, and microscale technology, were summarized and the feasibility of these technologies in the clinical repair of craniofacial defects was discussed.

Facilitated self-assembly of a prevascularized dermal/epidermal collagen scaffold

Introduction: Resurfacing complex full thickness wounds requires free tissue transfer which creates donor site morbidity. We describe a method to fabricate a skin flap equivalent with a hierarchical microvascular network. Materials & methods: We fabricated a flap of skin-like tissue containing a hierarchical vascular network by sacrificing Pluronic^® F127 macrofibers and interwoven microfibers within collagen encapsulating human pericytes and fibroblasts. Channels were seeded with smooth muscle and endothelial cells. Constructs were topically seeded with keratinocytes. Results: After 28 days in culture, multiphoton microscopy revealed a hierarchical interconnected network of macro- and micro-vessels; larger vessels (>100 μm) were lined with a monolayer endothelial neointima and a subendothelial smooth muscle neomedia. Neoangiogenic sprouts formed in the collagen protodermis and pericytes self-assembled around both fabricated vessels and neoangiogenic sprouts. Conclusion: We fabricated a prevascularized scaffold containing a hierarchical 3D network of interconnected macro- and microchannels within a collagen protodermis subjacent to an overlying protoepidermis with the potential for recipient microvascular anastomosis.

Critical Considerations for Regeneration of Vascularized Composite Tissues

Effective vascularization is vital for survival and functionality of complex tissue-engineered organs. The formation of the microvasculature, composed of endothelial cells (ECs) alone, has been mostly used to restore the vascular networks in organs. However, recent heterocellular studies demonstrate that co-culturing is a more effective approach in revascularization of engineered organs. This review presents key considerations for manufacturing of artificial vascularized composite tissues. We summarize the importance of co-cultures and the multicellular interactions with ECs, as well as design and use of bioreactors, as critical considerations for tissue vascularization. In addition, as an emerging scaffolding technique, this review also highlights the current caveats and hurdles associated with three-dimensional bioprinting and discusses recent developments in bioprinting strategies such as four-dimensional bioprinting and its future outlook for manufacturing of vascularized tissue constructs. Finally, the review concludes with addressing the critical challenges in the regulatory pathway and clinical translation of artificial composite tissue grafts. Impact statement Regeneration of composite tissues is critical as biophysical and biochemical characteristics differ between various types of tissues. Engineering a vascularized composite tissue has remained unresolved and requires additional evaluations along with optimization of methodologies and standard operating procedures. To this end, the main hurdle is creating a viable vascular endothelium that remains functional for a longer duration postimplantation, and can be manufactured using clinically appropriate source of cell lines that are scalable in vitro for the fabrication of human-scale organs. This review presents key considerations for regeneration and manufacturing of vascularized composite tissues as the field advances.

Induced Pluripotent Stem Cells in Dental and Nondental Tissue Regeneration: A Review of an Unexploited Potential

Cell-based therapies currently represent the state of art for tissue regenerative treatment approaches for various diseases and disorders. Induced pluripotent stem cells (iPSCs), reprogrammed from adult somatic cells, using vectors carrying definite transcription factors, have manifested a breakthrough in regenerative medicine, relying on their pluripotent nature and ease of generation in large amounts from various dental and nondental tissues. In addition to their potential applications in regenerative medicine and dentistry, iPSCs can also be used in disease modeling and drug testing for personalized medicine. The current review discusses various techniques for the production of iPSC-derived osteogenic and odontogenic progenitors, the therapeutic applications of iPSCs, and their regenerative potential in vivo and in vitro. Through the present review, we aim to explore the potential applications of iPSCs in dental and nondental tissue regeneration and to highlight different protocols used for the generation of different tissues and cell lines from iPSCs.

Mesenchymal stem cell-based bone tissue engineering for veterinary practice

Bone tissue engineering has been widely studied and proposed as a promising platform for correcting the bone defects. The applications of mesenchymal stem cell (MSC)-based bone tissue engineering have been investigated in various in vitro and in vivo models. In this regard, the promising animal bone defect models have been employed for illustrating the bone regenerative capacity of MSC-based bone tissue engineering. However, most studies aimed for clinical applications in human. These evidences suggest a knowledge gap to fulfill the accomplishment for veterinary implementation. In this review, the fundamental concept, knowledge, and technology of MSC-based bone tissue engineering focusing on veterinary applications are summarized. In addition, the potential canine MSCs resources for veterinary bone tissue engineering are reviewed, including canine bone marrow-derived MSCs, canine adipose-derived MSCs, and canine dental tissue-derived MSCs. This review will provide a basic and current information for studies aiming for the utilization of MSC-based bone tissue engineering in veterinary practice.

Impact of Induced Pluripotent Stem Cells in Bone Repair and Regeneration

PURPOSE OF REVIEW

The main objective of this article is to investigate the current trends in the use of induced pluripotent stem cells (iPSCs) for bone tissue repair and regeneration.

RECENT FINDINGS

Pluripotent stem cell-based tissue engineering has extended innovative therapeutic approaches for regenerative medicine. iPSCs have shown osteogenic differentiation capabilities and would be an innovative resource of stem cells for bone tissue regenerative applications. This review recapitulates the current knowledge and recent progress regarding utilization of iPSCs for bone therapy. A review of current findings suggests that a combination of a three-dimensional scaffolding system with iPSC technology to mimic the physiological complexity of the native stem cell niche is highly favorable for bone tissue repair and regeneration.

Periodontal Bone-Ligament-Cementum Regeneration via Scaffolds and Stem Cells

Periodontitis is a prevalent infectious disease worldwide, causing the damage of periodontal support tissues, which can eventually lead to tooth loss. The goal of periodontal treatment is to control the infections and reconstruct the structure and function of periodontal tissues including cementum, periodontal ligament (PDL) fibers, and bone. The regeneration of these three types of tissues, including the re-formation of the oriented PDL fibers to be attached firmly to the new cementum and alveolar bone, remains a major challenge. This article represents the first systematic review on the cutting-edge researches on the regeneration of all three types of periodontal tissues and the simultaneous regeneration of the entire bone-PDL-cementum complex, via stem cells, bio-printing, gene therapy, and layered bio-mimetic technologies. This article primarily includes bone regeneration; PDL regeneration; cementum regeneration; endogenous cell-homing and host-mobilized stem cells; 3D bio-printing and generation of the oriented PDL fibers; gene therapy-based approaches for periodontal regeneration; regenerating the bone-PDL-cementum complex via layered materials and cells. These novel developments in stem cell technology and bioactive and bio-mimetic scaffolds are highly promising to substantially enhance the periodontal regeneration including both hard and soft tissues, with applicability to other therapies in the oral and maxillofacial region.

Calcium phosphate cement scaffold with stem cell co-culture and prevascularization for dental and craniofacial bone tissue engineering

OBJECTIVE

Calcium phosphate cements (CPCs) mimic nanostructured bone minerals and are promising for dental, craniofacial and orthopedic applications. Vascularization plays a critical role in bone regeneration. This article represents the first review on cutting-edge research on prevascularization of CPC scaffolds to enhance bone regeneration.

METHODS

This article first presented the prevascularization of CPC scaffolds. Then the co-culture of two cell types in CPC scaffolds was discussed. Subsequently, to further enhance the prevascularization efficacy, tri-culture of three different cell types in CPC scaffolds was presented.

RESULTS

(1) Arg-Gly-Asp (RGD) incorporation in CPC bone cement scaffold greatly enhanced cell affinity and bone prevascularization; (2) By introducing endothelial cells into the culture of osteogenic cells (co-culture of two different cell types, or bi-culture) in CPC scaffold, the bone defect area underwent much better angiogenic and osteogenic processes when compared to mono-culture; (3) Tri-culture with an additional cell type of perivascular cells (such as pericytes) resulted in a substantially enhanced prevascularization of CPC scaffolds in vitro and more new bone and blood vessels in vivo, compared to bi-culture. Furthermore, biological cell crosstalk and capillary-like structure formation made critical contributions to the bi-culture system. In addition, the pericytes in the tri-culture system substantially promoted stability and maturation of the primary vascular network.

SIGNIFICANCE

The novel approach of CPC scaffolds with stem cell bi-culture and tri-culture is of great significance in the regeneration of dental, craniofacial and orthopedic defects in clinical practice.

A Novel Biodegradable Multilayered Bioengineered Vascular Construct with a Curved Structure and Multi-Branches

Constructing tissue engineered vascular grafts (TEVG) is of great significance for cardiovascular research. However, most of the fabrication techniques are unable to construct TEVG with a bifurcated and curved structure. This paper presents multilayered biodegradable TEVGs with a curved structure and multi-branches. The technique combined 3D printed molds and casting hydrogel and sacrificial material to create vessel-mimicking constructs with customizable structural parameters. Compared with other fabrication methods, the proposed technique can create more native-like 3D geometries. The diameter and wall thickness of the fabricated constructs can be independently controlled, providing a feasible approach for TEVG construction. Enzymatically-crosslinked gelatin was used as the material of the constructs. The mechanical properties and thermostability of the constructs were evaluated. Fluid-structure interaction simulations were conducted to examine the displacement of the construct’s wall when blood flows through it. Human umbilical vein endothelial cells (HUVECs) were seeded on the inner channel of the constructs and cultured for 72 h. The cell morphology was assessed. The results showed that the proposed technique had good application potentials, and will hopefully provide a novel technological approach for constructing integrated vasculature for tissue engineering.

The Potential of Different Origin Stem Cells in Modulating Oral Bone Regeneration Processes

Tissue engineering has gained much momentum since the implementation of stem cell isolation and manipulation for regenerative purposes. Despite significant technical improvements, researchers still have to decide which strategy (which type of stem cell) is the most suitable for their specific purpose. Therefore, this short review discusses the advantages and disadvantages of the three main categories of stem cells: embryonic stem cells, mesenchymal stem cells and induced pluripotent stem cells in the context of bone regeneration for dentistry-associated conditions. Importantly, when deciding upon the right strategy, the selection needs to be made in concordance with the morbidity and the life-threatening level of the condition in discussion. Therefore, even when a specific type of stem cell holds several advantages over others, their availability, invasiveness of the collection method and ethical standards become deciding parameters.

Novel magnetic calcium phosphate-stem cell construct with magnetic field enhances osteogenic differentiation and bone tissue engineering

Superparamagnetic iron oxide nanoparticles (IONPs) are promising bioactive additives to fabricate magnetic scaffolds for bone tissue engineering. To date, there has been no report on osteoinductivity of IONP-incorporated calcium phosphate cement (IONP-CPC) scaffold on stem cells using an exterior static magnetic field (SMF). The objectives of this study were to: (1) develop a novel magnetic IONP-CPC construct for bone tissue engineering, and (2) investigate the effects of IONP-incorporation and SMF application on the proliferation, osteogenic differentiation and bone mineral synthesis of human dental pulp stem cells (hDPSCs) seeded on IONP-CPC scaffold for the first time. The novel magnetic IONP-CPC under SMF enhanced the cellular performance of hDPSCs, yielding greater alkaline phosphatase activities (about 3-fold), increased expressions of osteogenic marker genes, and more cell-synthesized bone minerals (about 2.5-fold), compared to CPC control and nonmagnetic IONP-CPC. In addition, IONP-CPC induced more active osteogenesis than CPC control in rat mandible defects. These results were consistent with the enhanced cellular performance by magnetic IONP in media under SMF. Moreover, nano-aggregates were detected inside the cells by transmission electron microscopy (TEM). Therefore, the enhanced cell performance was attributed to the physical forces generated by the magnetic field together with cell internalization of the released magnetic nanoparticles from IONP-CPC constructs.

Characterization and in ovo vascularization of a 3D-printed hydroxyapatite scaffold with different extracellular matrix coatings under perfusion culture

For the fabrication of appropriate bone tissue-engineered constructs several prerequisites should be fulfilled. They should offer long-term stability, allow proper cell attachment and proliferation and furthermore be osteoinductive and easy to be vascularized. Having these requirements as background, we fabricated a novel porous 3D-printed hydroxyapatite (HA) scaffold and treated it with oxygen plasma (OPT). MG-63 pre-osteoblast-seeded bone constructs allowed good cell attachment and proliferation, which was even better when cultivated in a perfusion flow bioreactor. Moreover, the deposition of extracellular matrix (ECM) on the otherwise inorganic surface changed the mechanical properties in a favourable manner: elasticity increased from 42.95±1.09 to 91.9±5.1 MPa (assessed by nanoindentation). Compared to static conditions, osteogenic differentiation was enhanced in the bioreactor, with upregulation of ALP, collagen I and osteocalcin gene expression. In parallel experiments, primary human bone marrow mesenchymal stromal cells (hBMSCs) were used and findings under dynamic conditions were similar; with a higher commitment towards osteoblasts compared to static conditions. In addition, angiogenic markers CD31, eNOS and VEGF were upregulated, especially when osteogenic medium was used rather than proliferative medium. To compare differently fabricated ECMs in terms of vascularization, decellularized constructs were tested in the chorioallantoic membrane (CAM) assay with subsequent assessment of the functional perfusion capacity by MRI in the living chick embryo. Here, vascularization induced by ECM from osteogenic medium led to a vessel distribution more homogenous throughout the construct, while ECM from proliferative medium enhanced vessel density at the interface and, to a lower extent, at the middle and top. We conclude that dynamic cultivation of a novel porous OPT HA scaffold with hBMSCs in osteogenic medium and subsequent decellularization provides a promising off-the-shelf bone tissue-engineered construct.

It Takes Two: Endothelial-Perivascular Cell Cross-Talk in Vascular Development and Disease

The formation of new blood vessels is a crucial step in the development of any new tissue both during embryogenesis and in vitro models as without sufficient perfusion the tissue will be unable to grow beyond the size where nutrition and oxygenation can be managed by diffusion alone. Endothelial cells are the primary building block of blood vessels and are capable of forming tube like structures independently however they are unable to independently form functional vasculature which is capable of conducting blood flow. This requires support from other structures including supporting perivascular cells and the extracellular matrix. The crosstalk between endothelial cells and perivascular cells is vital in regulating vasculogenesis and angiogenesis and the consequences when this is disrupted can be seen in a variety of congenital and acquired disease states. This review details the mechanisms of vasculogenesis in vivo during embryogenesis and compares this to currently employed in vitro techniques. It also highlights clinical consequences of defects in the endothelial cell-pericyte cross-talk and highlights therapies which are being developed to target this pathway. Improving the understanding of the intricacies of endothelial-pericyte signaling will inform pathophysiology of multiple vascular diseases and allow the development of effective in vitro models to guide drug development and assist with approaches in tissue engineering to develop functional vasculature for regenerative medicine applications.

Calcium phosphate cements for bone engineering and their biological properties

Calcium phosphate cements (CPCs) are frequently used to repair bone defects. Since their discovery in the 1980s, extensive research has been conducted to improve their properties, and emerging evidence supports their increased application in bone tissue engineering. Much effort has been made to enhance the biological performance of CPCs, including their biocompatibility, osteoconductivity, osteoinductivity, biodegradability, bioactivity, and interactions with cells. This review article focuses on the major recent developments in CPCs, including 3D printing, injectability, stem cell delivery, growth factor and drug delivery, and pre-vascularization of CPC scaffolds via co-culture and tri-culture techniques to enhance angiogenesis and osteogenesis.

Macro-mesoporous composites containing PEEK and mesoporous diopside as bone implants: characterization, in vitro mineralization, cytocompatibility, and vascularization potential and osteogenesis in vivo

Superior in vitro bioactivity, cytocompatibility, and in vivo osteogenesis and vascularization potential.