The influence of electrospun fibre scaffold orientation and nano-hydroxyapatite content on the development of tooth bud stem cells in vitro

Engineered organoids in oral and maxillofacial regeneration

Oral and maxillofacial organoids, as three-dimensional study models of organs, have attracted increasing attention in tissue regeneration and disease modeling. However, traditional strategies for organoid construction still fail to precisely recapitulate the key characteristics of real organs, due to the difficulty in controlling the self-organization of cells in vitro. This review aims to summarize the recent progress of novel approaches to engineering oral and maxillofacial organoids. First, we introduced the necessary components and their roles in forming oral and maxillofacial organoids. Besides, we discussed cutting-edge technology in advancing the architecture and function of organoids, especially focusing on oral and maxillofacial tissue regeneration via novel strategy with designed cell-signal scaffold compounds. Finally, current limitations and future prospects of oral and maxillofacial organoids were represented to provide guidance for further disciplinary progression and clinical application to achieve organ regeneration.

Synthetic materials in craniofacial regenerative medicine: A comprehensive overview

The state-of-the-art approach to regenerating different tissues and organs is tissue engineering which includes the three parts of stem cells (SCs), scaffolds, and growth factors. Cellular behaviors such as propagation, differentiation, and assembling the extracellular matrix (ECM) are influenced by the cell's microenvironment. Imitating the cell's natural environment, such as scaffolds, is vital to create appropriate tissue. Craniofacial tissue engineering refers to regenerating tissues found in the brain and the face parts such as bone, muscle, and artery. More biocompatible and biodegradable scaffolds are more commensurate with tissue remodeling and more appropriate for cell culture, signaling, and adhesion. Synthetic materials play significant roles and have become more prevalent in medical applications. They have also been used in different forms for producing a microenvironment as ECM for cells. Synthetic scaffolds may be comprised of polymers, bioceramics, or hybrids of natural/synthetic materials. Synthetic scaffolds have produced ECM-like materials that can properly mimic and regulate the tissue microenvironment's physical, mechanical, chemical, and biological properties, manage adherence of biomolecules and adjust the material's degradability. The present review article is focused on synthetic materials used in craniofacial tissue engineering in recent decades.

Scaffold-based developmental tissue engineering strategies for ectodermal organ regeneration

Tissue engineering (TE) is a multidisciplinary research field aiming at the regeneration, restoration, or replacement of damaged tissues and organs. Classical TE approaches combine scaffolds, cells and soluble factors to fabricate constructs mimicking the native tissue to be regenerated. However, to date, limited success in clinical translations has been achieved by classical TE approaches, because of the lack of satisfactory biomorphological and biofunctional features of the obtained constructs. Developmental TE has emerged as a novel TE paradigm to obtain tissues and organs with correct biomorphology and biofunctionality by mimicking the morphogenetic processes leading to the tissue/organ generation in the embryo. Ectodermal appendages, for instance, develop in vivo by sequential interactions between epithelium and mesenchyme, in a process known as secondary induction. A fine artificial replication of these complex interactions can potentially lead to the fabrication of the tissues/organs to be regenerated. Successful developmental TE applications have been reported, in vitro and in vivo, for ectodermal appendages such as teeth, hair follicles and glands. Developmental TE strategies require an accurate selection of cell sources, scaffolds and cell culture configurations to allow for the correct replication of the in vivo morphogenetic cues. Herein, we describe and discuss the emergence of this TE paradigm by reviewing the achievements obtained so far in developmental TE 3D scaffolds for teeth, hair follicles, and salivary and lacrimal glands, with particular focus on the selection of biomaterials and cell culture configurations.

Advanced technologies in periodontal tissue regeneration based on stem cells: Current status and future perspectives

Periodontitis is a progressive inflammation disease, the clinical management of which remains a challenge. The traditional management may control periodontal inflammation, but failed to regenerate functional periodontium. This review summarizes the most advancing regenerative techniques regarding stem cell culture and scaffold fabrication, such as cell sheeting, spheroid culture, electrospinning and 3D printing. The applications of different techniques manifest tremendous potential of regenerating the complete and functional periodontium. Albeit promising, new technologies have met with their own drawbacks such as insufficient vascularization and precision, which necessitate deeper modification. Thus, this review also points out the potential perspectives and methods aiming at their disadvantages, illuminating the directions of future researches to successful clinical scenarios.

Microwave-assisted synthesis and evaluation of type 1 collagen-apatite composites for dental tissue regeneration

The aim was to develop an economical and biocompatible collagen-based bioactive composite for tooth regeneration. Acid-soluble collagen was extracted and purified from fish scales. The design was innovated to molecularly tailor the surface charge sites of the nano-apatite providing chemical bonds with the collagen matrix via microwave irradiation technique. The obtained collagen was identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis. The composites were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis/differential scanning calorimetry, and scanning electron microscopy. MC3T3-E1 cell lines were used to assess the biological effects of these materials by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetra zolium bromide (MTT) assay. Indirect contact test was performed by extracting representative elutes in cell culture media and sulforhodamine B analysis was performed. Chorioallantoic membrane assay was conducted to define the new vessels formation behavior. The purity of collagen extracts was determined and showed two α-chains, i.e. the characteristic of type I collagen. Fourier transform infrared spectroscopy showed the characteristic peaks for amide I, I, III, and phosphate for collagen and composites. Scanning electron microscopy images showed three-dimensional mesh of collagen/apatite nano-fibers. Nontoxic behavior of composites was observed and there were graded and dose-related effects on experimental compounds. The angiogenesis and vessels formation behavior were observed in bioactive collagen composite. The obtained composites have potential to be used for tooth structure regeneration.

Novel Biomimetic Microphysiological Systems for Tissue Regeneration and Disease Modeling

Biomaterials engineered to closely mimic morphology, architecture, and nanofeatures of naturally occurring in vivo extracellular matrices (ECM) have gained much interest in regenerative medicine and in vitro biomimetic platforms. Similarly, microphysiological systems (MPS), such as lab-chip, have drummed up momentum for recapitulating precise biomechanical conditions to model the in vivo microtissue environment. However, porosity of in vivo scaffolds regulating barrier and interface functions is generally absent in lab-chip systems, or otherwise introduces considerable cost, complexity, and an unrealistic uniformity in pore geometry. We address this by integrating electrospun nanofibrous porous scaffolds in MPS to develop the lab-on-a-brane (LOB) MPS for more effectively modeling transport, air-liquid interface, and tumor progression and for personalized medicine applications.

Advances and perspectives in tooth tissue engineering

Bio-engineered teeth that can grow and remodel in a manner similar to that of natural teeth have the potential to serve as permanent replacements to the currently used prosthetic teeth, such as dental implants. A major challenge in designing functional bio-engineered teeth is to mimic both the structural and anisotropic mechanical characteristics of the native tooth. Therefore, the field of dental and whole tooth regeneration has advanced towards the molecular and nanoscale design of bio-active, biomimetic systems, using biomaterials, drug delivery systems and stem cells. The focus of this review is to discuss recent advances in tooth tissue engineering, using biomimetic scaffolds that provide proper architectural cues, exhibit the capacity to support dental stem cell proliferation and differentiation and sequester and release bio-active agents, such as growth factors and nucleic acids, in a spatiotemporal controlled manner. Although many in vitro and in vivo studies on tooth regeneration appear promising, before tooth tissue engineering becomes a reality for humans, additional research is needed to perfect methods that use adult human dental stem cells, as opposed to embryonic dental stem cells, and to devise the means to generate bio-engineered teeth of predetermined size and shape. Copyright © 2016 John Wiley & Sons, Ltd.

Influence of highly porous electrospun PLGA/PCL/nHA fibrous scaffolds on the differentiation of tooth bud cells in vitro

In this study, we investigated the use of three-dimensional electrospun poly(lactic-co-glycolic acid)/poly(ε-caprolactone) (PLGA/PCL) scaffolds seeded and cultured with postnatal dental cells, for improved dental tissue regeneration. Wet-electrospinning combined with ultrasonic treatment was studied as a method to enhance scaffold porosity and to promote cell-cell interactions. We also investigated whether nano-hydroxyapatite (nHA) incorporation could enhance dental cell differentiation. All scaffolds were seeded with human tooth pulp-derived dental mesenchymal (hDM) cells, or a combination of hDM and pig dental epithelial (pDE) cells, cultured for up to 28 days. Developmentally staged samples were assessed using scanning electron microscopy, histological, immunohistochemical, DNA and alkaline phosphatase activity assays, and quantitative-PCR for ameloblastic, odontoblastic, and osteogenic related gene expression. Results showed that electrospun scaffolds exhibited sufficient porosity to support robust cell ingrowth. Additional ultrasonic treatment led to a less homogeneous scaffold porosity, resulting in evident cell clustering and enhanced hDM-pDE cell-cell interactions. Finally, nHA incorporation was found to enhance dental cell differentiation. However, it also resulted in smaller fiber diameter and reduced scaffold porosity, and inhibited cell ingrowth and proliferation. In conclusion, ultrasonically treated wet-electrospun PLGA/PCL scaffolds are a suitable material for dental tissue engineering, and support future in vivo evaluations of this model. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2597-2607, 2017.

Hydrogel fibers encapsulating human stem cells in an injectable calcium phosphate scaffold for bone tissue engineering

Human induced pluripotent stem cells (hiPSCs), human embryonic stem cells (hESCs) and human umbilical cord mesenchymal stem cells (hUCMSCs) are exciting cell sources for use in regenerative medicine. There have been no reports on long hydrogel fibers encapsulating stem cells inside an injectable calcium phosphate cement (CPC) scaffold for bone tissue engineering. The objectives of this study were: (1) to develop a novel injectable CPC construct containing hydrogel fibers encapsulating cells for bone engineering, and (2) to investigate and compare cell viability, proliferation and osteogenic differentiation of hiPSC-MSCs, hESC-MSCs and hUCMSCs in injectable CPC. The pastes encapsulating the stem cells were fully injectable under a small injection force, and the injection did not harm the cells, compared with non-injected cells (p  >  0.1). The mechanical properties of the stem cell-CPC construct were much better than those of previous injectable polymers and hydrogels for cell delivery. The hiPSC-MSCs, hESC-MSCs and hUCMSCs in hydrogel fibers in CPC had excellent proliferation and osteogenic differentiation. All three cell types yielded high alkaline phosphatase, runt-related transcription factor, collagen I and osteocalcin expression (mean  ±  SD; n  =  6). Cell-synthesized minerals increased substantially with time (p  <  0.05), with no significant difference among the three types of cells (p  >  0.1). Mineralization by hiPSC-MSCs, hESC-MSCs and hUCMSCs in CPC at 14 d was 13-fold that at 1 d. In conclusion, all three types of cells (hiPSC-MSCs, hESC-MSCs and hUCMSCs) in a CPC scaffold showed high potential for bone tissue engineering, and the novel injectable CPC construct with cell-encapsulating hydrogel fibers is promising for enhancing bone regeneration in dental, craniofacial and orthopedic applications.

The Possible Roles of Biological Bone Constructed with Peripheral Blood Derived EPCs and BMSCs in Osteogenesis and Angiogenesis

This study aimed to determine the possible potential of partially deproteinized biologic bone (PDPBB) seeded with bone marrow stromal cells (BMSCs) and endothelial progenitor cells (EPCs) in osteogenesis and angiogenesis. BMSCs and EPCs were isolated, identified, and cocultured in vitro, followed by seeding on the PDPBB. Expression of osteogenesis and vascularization markers was quantified by immunofluorescence (IF) staining, immunohistochemistry (IHC), and quantitive real-time polymerase chain reaction (qRT-PCR). Scanning electron microscope (SEM) was also employed to further evaluate the morphologic alterations of cocultured cells in the biologic bone. Results demonstrated that the coculture system combined with BMSCs and EPCs had significant advantages of (i) upregulating the mRNA expression of VEGF, Osteonectin, Osteopontin, and Collagen Type I and (ii) increasing ALP and OC staining compared to the BMSCs or EPCs only group. Moreover, IHC staining for CD105, CD34, and ZO-1 increased significantly in the implanted PDPBB seeded with coculture system, compared to that of BMSCs or EPCs only, respectively. Summarily, the present data provided evidence that PDPBB seeded with cocultured system possessed favorable cytocompatibility, provided suitable circumstances for different cell growth, and had the potential to provide reconstruction for cases with bone defection by promoting osteogenesis and angiogenesis.

Combination of aligned PLGA/Gelatin electrospun sheets, native dental pulp extracellular matrix and treated dentin matrix as substrates for tooth root regeneration

In tissue engineering, scaffold materials provide effective structural support to promote the repair of damaged tissues or organs through simulating the extracellular matrix (ECM) microenvironments for stem cells. This study hypothesized that simulating the ECM microenvironments of periodontium and dental pulp/dentin complexes would contribute to the regeneration of tooth root. Here, aligned PLGA/Gelatin electrospun sheet (APES), treated dentin matrix (TDM) and native dental pulp extracellular matrix (DPEM) were fabricated and combined into APES/TDM and DPEM/TDM for periodontium and dental pulp regeneration, respectively. This study firstly examined the physicochemical properties and biocompatibilities of both APES and DPEM in vitro, and further investigated the degradation of APES and revascularization of DPEM in vivo. Then, the potency of APES/TDM and DPEM/TDM in odontogenic induction was evaluated via co-culture with dental stem cells. Finally, we verified the periodontium and dental pulp/dentin complex regeneration in the jaw of miniature swine. Results showed that APES possessed aligned fiber orientation which guided cell proliferation while DPEM preserved the intrinsic fiber structure and ECM proteins. Importantly, both APES/TDM and DPEM/TDM facilitated the odontogenic differentiation of dental stem cells in vitro. Seeded with stem cells, the sandwich composites (APES/TDM/DPEM) generated tooth root-like tissues after being transplanted in porcine jaws for 12 w. In dental pulp/dentin complex-like tissues, columnar odontoblasts-like layer arranged along the interface between newly-formed predentin matrix and dental pulp-like tissues in which blood vessels could be found; in periodontium complex-like tissues, cellular cementum and periodontal ligament (PDL)-like tissues were generated on the TDM surface. Thus, above results suggest that APES and DPEM exhibiting appropriate physicochemical properties and well biocompatibilities, in accompany with TDM, could make up an ECM microenvironment for tooth root regeneration, which also offers a strategy for complex tissue or organ regeneration.

Porous deproteinized bovine bone scaffold with three-dimensional localized drug delivery system using chitosan microspheres

BACKGROUND

Bone substation grafts, such as hydroxyapatite (HA) and tricalciumphosphate (TCP), have been extensively used in clinical applications, but evidence suggests that they offer poor osteoinductive properties compared to allografts and autografts. In order to increase bone growth with such grafts, Bone Morphogenetic Protein 2 (BMP-2) was incorporated into a three dimensional reservoir. The purpose of the present study was to develop a novel drug delivery system which is capable of controlled release of BMP-2.

METHODS

DBB were prepared from bovine cancellous bone harvested from fetal bovine femur or tibia and then sinting at 1000°C. BMP-2-loaded chitosan (CS) microspheres were fabricated by cross-linking. Then the treated DBB powders were blended with chitosan microspheres solution. Finally, the composites were lyophilized with a freeze dryer to obtain the DBB/CMs scaffolds. X-ray diffractor (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) were used to characterize the sample. The quantification of the delivery profile of BMP-2 was determined using an enzyme-linked immunosorbent assay (ELISA) kit. The in vitro assays were to characterize the biocompatibility of this composite.

RESULTS

In this study, BMP-2/Chitosan (CS) microspheres were successively loaded onto a deproteinized bovine bone (DBB) scaffold. The release profile of BMP-2 indicated an initial burst release followed by a more even sustained release. An in vitro bioactivity assay revealed that the encapsulated growth factor was biologically active.

CONCLUSIONS

The cell culture assay suggest that the excellent biocompatibility of the DBB- BMP-2/CS. Therefore, this novel microsphere scaffold system can be effectively used in current tissue engineering applications.

Current Uses of Poly(lactic-co-glycolic acid) in the Dental Field: A Comprehensive Review

Poly(lactic-co-glycolic acid) or PLGA is a biodegradable polymer used in a wide range of medical applications. Specifically PLGA materials are also developed for the dental field in the form of scaffolds, films, membranes, microparticles, or nanoparticles. PLGA membranes have been studied with promising results, either alone or combined with other materials in bone healing procedures. PLGA scaffolds have been used to regenerate damaged tissues together with stem cell-based therapy. There is solid evidence that the development of PLGA microparticles and nanoparticles may be beneficial to a wide range of dental fields such as endodontic therapy, dental caries, dental surgery, dental implants, or periodontology. The aim of the current paper was to review the recent advances in PLGA materials and their potential uses in the dental field.

Application of Stem Cell Technology in Dental Regenerative Medicine

SIGNIFICANCE

In this review, we summarize the current literature regarding the isolation and characterization of dental tissue-derived stem cells and address the potential of these cell types for use in regenerative cell transplantation therapy.

RECENT ADVANCES

Looking forward, platforms for the delivery of stem cells via scaffolds and the use of growth factors and cytokines for enhancing dental stem cell self-renewal and differentiation are discussed.

CRITICAL ISSUES

We aim to understand the developmental origins of dental tissues in an effort to elucidate the molecular pathways governing the genesis of somatic dental stem cells. The advantages and disadvantages of several dental stem cells are discussed, including the developmental stage and specific locations from which these cells can be purified. In particular, stem cells from human exfoliated deciduous teeth may act as a very practical and easily accessibly reservoir for autologous stem cells and hold the most value in stem cell therapy. Dental pulp stem cells and periodontal ligament stem cells should also be considered for their triple lineage differentiation ability and relative ease of isolation. Further, we address the potentials and limitations of induced pluripotent stem cells as a cell source in dental regenerative.

FUTURE DIRECTIONS

From an economical and a practical standpoint, dental stem cell therapy would be most easily applied in the prevention of periodontal ligament detachment and bone atrophy, as well as in the regeneration of dentin-pulp complex. In contrast, cell-based tooth replacement due to decay or other oral pathology seems, at the current time, an untenable approach.