Initial bone regeneration around fenestrated implants in Beagle dogs using basic fibroblast growth factor–gelatin hydrogel complex with varying biodegradation rates

Stem-Cell Therapy: Filling Gaps in Oro-Maxillofacial Region

How do stem cells function? Why should we, as dentists, care about stem cells? How might dental procedures be substituted by stem cells? Are stem cells capable of regenerating a tooth or temporomandibular joint (TMJ)? Although the ability to regenerate a destroyed tissue has been known for a while, research into regenerative medicine and dentistry has made significant strides in molecular biology. A paradigm shift in the therapeutic toolbox for dental and oral diseases is likely to result from a growing understanding of biological concepts in the regeneration of oral/dental tissues along with stem cell research, leading to an intense search for "biological solutions to biological problems." Among other tissues, orofacial tissues effectively separate stem cells from human tissues. Because they can self-renew and produce different cell types, stem cells offer novel techniques for regenerating damaged tissues and curing illnesses. A number of significant milestone successes have shown their practical applicability, traditional biomaterial-based treatments in regenerative dentistry as therapeutic alternatives that offer regeneration of damaged oral tissues rather than merely "filling the gaps." In order to use these innovative accomplishments for patient well-being, the ultimate goal of this ground-breaking technology, well-designed clinical studies must be implemented as a crucial next step. The review's objective is to briefly synthesize the literature on stem cells in terms of their traits, subtypes, and uses for dental stem cells. It has been highlighted that stem cell therapy has the ability to treat craniofacial abnormalities and regenerate teeth in the oral and maxillofacial regions.

Development of a Novel Marine-Derived Tricomposite Biomaterial for Bone Regeneration

Bone tissue engineering is a promising treatment for bone loss that requires a combination of porous scaffold and osteogenic cells. The aim of this study was to evaluate and develop a tricomposite, biomimetic scaffold consisting of marine-derived biomaterials, namely, chitosan and fucoidan with hydroxyapatite (HA). The effects of chitosan, fucoidan and HA individually and in combination on the proliferation and differentiation of human mesenchymal stem cells (MSCs) were investigated. According to the SEM results, the tricomposite scaffold had a uniform porous structure, which is a key requirement for cell migration, proliferation and vascularisation. The presence of HA and fucoidan in the chitosan tricomposite scaffold was confirmed using FTIR, which showed a slight decrease in porosity and an increase in the density of the tricomposite scaffold compared to other formulations. Fucoidan was found to inhibit cell proliferation at higher concentrations and at earlier time points when applied as a single treatment, but this effect was lost at later time points. Similar results were observed with HA alone. However, both HA and fucoidan increased MSC mineralisation as measured by calcium deposition. Differentiation was significantly enhanced in MSCs cultured on the tricomposite, with increased alkaline phosphatase activity on days 17 and 25. In conclusion, the tricomposite is biocompatible, promotes osteogenesis, and has the structural and compositional properties required of a scaffold for bone tissue engineering. This biomaterial could provide an effective treatment for small bone defects as an alternative to autografts or be the basis for cell attachment and differentiation in ex vivo bone tissue engineering.

Applications of Hydrogels in Drug Delivery for Oral and Maxillofacial Diseases

Oral and maxillofacial diseases have an important impact on local function, facial appearance, and general health. As a multifunctional platform, hydrogels are widely used in the biomedical field due to their excellent physicochemical properties. In recent years, a large number of studies have been conducted to adapt hydrogels to the complex oral and maxillofacial environment by modulating their pore size, swelling, degradability, stimulus-response properties, etc. Meanwhile, many studies have attempted to use hydrogels as drug delivery carriers to load drugs, cytokines, and stem cells for antibacterial, anticancer, and tissue regeneration applications in oral and maxillofacial regions. This paper reviews the application and research progress of hydrogel-based drug delivery systems in the treatment of oral and maxillofacial diseases such as caries, endodontic diseases, periodontal diseases, maxillofacial bone diseases, mucosal diseases, oral cancer, etc. The characteristics and applications of hydrogels and drug-delivery systems employed for the treatment of different diseases are discussed in order to provide a reference for further research on hydrogel drug-delivery systems in the future.

Preparation of Collagen/Hydroxyapatite Composites Using the Alternate Immersion Method and Evaluation of the Cranial Bone-Forming Capability of Composites Complexed with Acidic Gelatin and b-FGF

Bone-substitute materials are essential in dental implantology. We prepared collagen (Col)/hydroxyapatite (Hap)/acidic gelatin (AG)/basic fibroblast growth factor (b-FGF) constructs with enhanced bone-forming capability. The Col/Hap apatite composites were prepared by immersing Col sponges alternately in calcium and phosphate ion solutions five times, for 20 and 60 min, respectively. Then, the sponges were heated to 56 °C for 48 h. Scanning electron microscopy/energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction analyses showed that the Col/Hap composites contained poorly crystalline Hap precipitates on the Col matrix. Col/Hap composite granules were infiltrated by AG, freeze-dried, and immersed in b-FGF solution. The wet quaternary constructs were implanted in rat cranial bone defects for 8 weeks, followed by soft X-ray measurements and histological analysis. Animal studies have shown that the constructs moderately increase bone formation in cranial bone defects. We found that an alternate immersion time of 20 min led to the greatest bone formation (p < 0.05). Constructs placed inside defects slightly extend the preexisting bone from the defect edges and lead to the formation of small island-like bones inside the defect, followed by disappearance of the constructs. The combined use of Col, Hap, AG, and b-FGF might bring about novel bone-forming biomaterials.

A Simple Preparation Method of Gelatin Hydrogels Incorporating Cisplatin for Sustained Release

The objective of this study was to develop a new preparation method for cisplatin (CDDP)-incorporated gelatin hydrogels without using chemical crosslinking nor a vacuum heating instrument for dehydrothermal crosslinking. By simply mixing CDDP and gelatin, CDDP-crosslinked gelatin hydrogels (CCGH) were prepared. CDDP functions as a crosslinking agent of gelatin to form the gelatin hydrogel. Simultaneously, CDDP is incorporated into the gelatin hydrogel as a controlled release carrier. CDDP's in vitro and in vivo anticancer efficacy after incorporation into CCGH was evaluated. In the in vitro system, the CDDP was released gradually due to CCGH degradation with an initial burst release of approximately 16%. CDDP metal-coordinated with the degraded fragment of gelatin was released from CCGH with maintaining the anticancer activity. After intraperitoneal administration of CCGH, CDDP was detected in the blood circulation while its toxicity was low. Following intraperitoneal administration of CCGH in a murine peritoneal dissemination model of human gastric cancer MKN45-Luc cell line, the survival time was significantly prolonged compared with free CDDP solution. It is concluded that CCGH prepared by the CDDP-based crosslinking of gelatin is an excellent sustained release system of CDDP to achieve superior anticancer effects with minimal side effects compared with free CDDP solution.

Three-Dimensional Culture System of Cancer Cells Combined with Biomaterials for Drug Screening

Simple Summary

For the research and development of drug discovery, it is of prime importance to construct the three-dimensional (3D) tissue models in vitro. To this end, the enhancement design of cell function and activity by making use of biomaterials is essential. In this review, 3D culture systems of cancer cells combined with several biomaterials for anticancer drug screening are introduced.

Abstract

Anticancer drug screening is one of the most important research and development processes to develop new drugs for cancer treatment. However, there is a problem resulting in gaps between the in vitro drug screening and preclinical or clinical study. This is mainly because the condition of cancer cell culture is quite different from that in vivo. As a trial to mimic the in vivo cancer environment, there has been some research on a three-dimensional (3D) culture system by making use of biomaterials. The 3D culture technologies enable us to give cancer cells an in vitro environment close to the in vivo condition. Cancer cells modified to replicate the in vivo cancer environment will promote the biological research or drug discovery of cancers. This review introduces the in vitro research of 3D cell culture systems with biomaterials in addition to a brief summary of the cancer environment.

A cancer invasion model of cancer-associated fibroblasts aggregates combined with TGF-β1 release system

Introduction

The objective of this study is to design a cancer invasion model where the cancer invasion rate can be regulated in vitro.

Methods

Cancer-associated fibroblasts (CAF) aggregates incorporating gelatin hydrogel microspheres (GM) containing various concentrations of transforming growth factor-β1 (TGF-β1) (CAF-GM-TGF-β1) were prepared. Alpha-smooth muscle actin (α-SMA) for the CAF aggregates was measured to investigate the CAF activation level by changing the concentration of TGF-β1. An invasion assay was performed to evaluate the cancer invasion rate by co-cultured of cancer cells with various CAF-GM-TGF-β1.

Results

The expression level of α-SMA for CAF increased with an increased in the TGF-β1 concentration. When co-cultured with various types of CAF-GM-TGF-β1, the cancer invasion rate was well correlated with the α-SMA level. It is conceivable that the TGF-β1 concentration could modify the level of CAF activation, leading to the invasion rate of cancer cells. In addition, at the high concentrations of TGF-β1, the effect of a matrix metalloproteinase (MMP) inhibitor on the cancer invasion rate was observed. The higher invasion rate would be achieved through the higher MMP production.

Conclusions

The present model is promising to realize the cancer invasion whose rate can be modified by changing the TGF-β1 concentration.

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This invasion model would be a promising tool for anti-cancer drug screening.

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TGF-β1 was controlled release from gelatin hydrogel microspheres.

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CAF were activated by increased TGF-β1 concentration.

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There was a good correlation between invasion rate and TGF-β1 concentration.

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Higher invasion rate would be achieved through matrix metalloproteinase production.

Stem Cells in Dentistry: Types of Intra- and Extraoral Tissue-Derived Stem Cells and Clinical Applications

Stem cells are undifferentiated cells, capable of renewing themselves, with the capacity to produce different cell types to regenerate missing tissues and treat diseases. Oral facial tissues have been identified as a source and therapeutic target for stem cells with clinical interest in dentistry. This narrative review report targets on the several extraoral- and intraoral-derived stem cells that can be applied in dentistry. In addition, stem cell origins are suggested in what concerns their ability to differentiate as well as their particular distinguishing quality of convenience and immunomodulatory for regenerative dentistry. The development of bioengineered teeth to replace the patient's missing teeth was also possible because of stem cell technologies. This review will also focus our attention on the clinical application of stem cells in dentistry. In recent years, a variety of articles reported the advantages of stem cell-based procedures in regenerative treatments. The regeneration of lost oral tissue is the target of stem cell research. Owing to the fact that bone imperfections that ensue after tooth loss can result in further bone loss which limit the success of dental implants and prosthodontic therapies, the rehabilitation of alveolar ridge height is prosthodontists' principal interest. The development of bioengineered teeth to replace the patient's missing teeth was also possible because of stem cell technologies. In addition, a “dental stem cell banking” is available for regenerative treatments in the future. The main features of stem cells in the future of dentistry should be understood by clinicians.

Journey into Bone Models: A Review

Bone is a complex tissue with a variety of functions, such as providing mechanical stability for locomotion, protection of the inner organs, mineral homeostasis and haematopoiesis. To fulfil these diverse roles in the human body, bone consists of a multitude of different cells and an extracellular matrix that is mechanically stable, yet flexible at the same time. Unlike most tissues, bone is under constant renewal facilitated by a coordinated interaction of bone-forming and bone-resorbing cells. It is thus challenging to recreate bone in its complexity in vitro and most current models rather focus on certain aspects of bone biology that are of relevance for the research question addressed. In addition, animal models are still regarded as the gold-standard in the context of bone biology and pathology, especially for the development of novel treatment strategies. However, species-specific differences impede the translation of findings from animal models to humans. The current review summarizes and discusses the latest developments in bone tissue engineering and organoid culture including suitable cell sources, extracellular matrices and microfluidic bioreactor systems. With available technology in mind, a best possible bone model will be hypothesized. Furthermore, the future need and application of such a complex model will be discussed.

Ridge preservation using basic fibroblast growth factor-2 and collagenated biphasic calcium phosphate in beagle dogs

Purpose

The aim of this study was to evaluate volumetric and histologic changes in edentulous alveolar ridge areas after ridge preservation using basic fibroblast growth factor-2 (bFGF-2) in combination with collagenated biphasic calcium phosphate (BCP).

Methods

The experiments were performed in 6 adult male beagle dogs. The following 3 groups were created: 1) ridge preservation with bFGF-2 and collagenated BCP (experimental group), 2) ridge preservation with collagenated BCP (positive control group), and 3) a negative control group in which no ridge preservation procedure was performed. Volumetric change analysis was performed using an optical scanner and casts. Histological observations were made using light microscopy.

Results

After the initial swelling subsided, the magnitude of the volumetric change in the experimental group and positive control group was smaller than in the negative control group. In the experimental group, a distinct trend was observed for the resorption of residual bone and collagen fibers at 4 weeks and for more mature bone and faster healing at 12 weeks.

Conclusions

Based on the findings of the present study, bFGF-2 may be considered for use as a therapeutic molecule in ridge preservation procedures.

Preparation of EpH4 and 3T3L1 cells aggregates incorporating gelatin hydrogel microspheres for a cell condition improvement

The objective of this study is to prepare three dimensional (3D) of mouse mammary epithelial EpH4 and mouse preadipocyte 3T3L1 cells in the presence of gelatin hydrogel microspheres (GM) and evaluate the effect of GM presence on the survival and functions of cells in the 3D cell aggregates. Gelatin was dehydrothermally crosslinked at 140 °C for 48 h in a water-in-oil emulsion state to obtain the GM with average diameters of 50 and 200 μm, followed by treatment with fibronectin (FN). EpH4 and/or 3T3L1 cells were cultured with or without the FN-treated GM in round U-bottom wells of 96-multiwell culture plates which had been coated with poly (vinyl alcohol) (PVA) to allow the cells to form their aggregates. On the other hand, EpH4 cells were precultured with the FN-treated GM, and then continued to culture with 3T3L1 cells in the same condition described above. The EpH4 cells attached onto the GM in the cell number dependent manner, irrespective of their size. When 3T3L1 cells were incubated with the original and GM-preincubated EpH4 cells in the presence of both the FN-treated GM, the number of alive cells in the aggregates was significantly high compared with that for the absence of FN-treated GM. In addition, higher β-casein expression level of EpH4 cells in EpH4/3T3L1 cells aggregates in the presence of FN-treated GM was observed than that of cells in the absence of FN-treated GM. Laminin secretion was also promoted for the cells aggregates cultured with FN-treated GM. It is concluded that the presence of FN-treated GM in the EpH4/3T3L1 cells aggregates gave a better condition to cells, resulting in an enhanced generation of β-casein from EpH4 cells in the aggregates.

Effect of locally applied bFGF on implant stability: biomechanical evaluation of 2 different implant surfaces in rabbits

OBJECTIVES

The aim of this study was to evaluate the implant stability with the addition of local application of basic fibroblast growth factor (bFGF) during the osseointegration of 2 different dental implant surfaces using rabbit tibia model.

MATERIALS AND METHODS

Fifty-six dental implants, 28 of hydrophilic surface (SLActive) and 28 of hydrophobic surface (OsseoSpeed), were placed in 14 mature New Zealand rabbits. The rabbits each received both SLActive and OsseoSpeed implants per tibia, and bFGF was applied locally on 1 randomly selected tibia. Half of the subjects were killed at the fourth week of healing period, and the other half were killed at the twelfth week. Stabilization was assessed using resonance frequency analysis (RFA) and removal torque value (RTV).

RESULTS

The local application of bFGF was found to enhance osseointegration, especially at the fourth week of healing period after application (P = 0.046). RFAs and RTVs were found to be higher in bFGF-treated implant with hydrophilic surfaces when compared with both bFGF-treated hydrophobic implants and nontreated hydrophilic controls.

CONCLUSION

Local application of bFGF seems to increase the stabilization values in implants with hydrophilic surfaces and those with hydrophobic surfaces.

Comparative study of BMP-2 alone and combined with VEGF carried by hydrogel for maxillary alveolar bone regeneration

The effect of vascular endothelial growth factor (VEGF) combined with bone morphogenetic protein-2 (BMP-2) for bone regeneration is still controversial as to whether or not VEGF has a synergistic or additive effect. This study attempted to evaluate the synergistic effect of VEGF and BMP-2 compared to BMP-2 alone for maxillary alveolar bone regeneration using collagen sponge/hydrogel complex sheets in a canine model. After mixing BMP-2 and VEGF with a hyaluronic acid-based hydrogel (HAH), the collagen sponge/hydrogel complex was transplanted into maxillary alveolar bone defects (n=14) after the extraction of canine upper first molars on both sides. Bone regeneration was evaluated in three groups (control group without growth factors, experimental groups I and II with BMP-2 alone and BMP-2 and VEGF, respectively) using micro-computed tomography and histological staining. The total amount of new bone formations and bone mineral density were significantly higher in the group with BMP-2 only and the group with BMP-2 combined with VEGF than it in the control group. The area with positive staining of von Willebrand factor bone defect was significantly greater in the group with BMP-2 only and with dual growth factors than the control. BMP-2 released from the HAH promoted new bone formation. However, the combination of BMP-2 and VEGF did not show a synergistic or additive effect on bone regeneration at canine maxillary alveolar bone defects.

Sustained delivery of biomolecules from gelatin carriers for applications in bone regeneration

Local delivery of therapeutic biomolecules to stimulate bone regeneration has matured considerably during the past decades, but control over the release of these biomolecules still remains a major challenge. To this end, suitable carriers that allow for tunable spatial and temporal delivery of biomolecules need to be developed. Gelatin is one of the most widely used natural polymers for the controlled and sustained delivery of biomolecules because of its biodegradability, biocompatibility, biosafety and cost–effectiveness. The current study reviews the applications of gelatin as carriers in form of bulk hydrogels, microspheres, nanospheres, colloidal gels and composites for the programmed delivery of commonly used biomolecules for applications in bone regeneration with a specific focus on the relationship between carrier properties and delivery characteristics.

Implementing tissue engineering and regenerative medicine solutions in medical implants

BACKGROUND

Surgical implants are widely used in the medical field but their long-term performance is limited due to failure of integration with tissues. This manuscript describes very well-known problems associated with implants and discusses novel solutions used in tissue engineering and regenerative medicine that can be implemented in this uncommonly discussed medical area.

SOURCES OF DATA

General and medical literature describing modifications of medical and surgical implants, biofunctionalization, tissue engineering and regenerative medicine.

AREAS OF AGREEMENT

Procedures for surgical implantation have grown substantially in the last few decades and provided improved quality of life for patients, regardless of area of implantation and device type and purpose.

AREAS OF CONTROVERSY

In general, implants fail because of lack of long-term integration with the surrounding tissues. Implant manufacturers have not addressed implant failure from the point of view of biointegration. In addition, some medical practitioners are inclined to treat implant failure by using anti-infection methods to prevent bacterial adhesion. However, both approaches are conceptually limited, as discussed in this manuscript.

GROWING POINTS

Implantation in the future will not be limited to medically needed procedures but also to a growing number of cosmetic body transformation procedures, which may include perceived 'improved implant functions' over natural tissues or organs. An additional trend is that implant procedures are being progressively performed in younger individuals.

AREAS TIMELY FOR DEVELOPING RESEARCH

Current implants generally do not allow the physician to have controlled long-term access to internal tissues in contact with the implants, for example to release specific compounds when medically needed to the problem area.

Hydrogels for tissue engineering and regenerative medicine

Injectable hydrogels have become an incredibly prolific area of research in the field of tissue engineering and regenerative medicine, because of their high water content, mechanical similarity to natural tissues, and ease of surgical implantation, hydrogels are at the forefront of biomedical scaffold and drug carrier design.

The effect of laminin-1-doped nanoroughened implant surfaces: gene expression and morphological evaluation

Aim. This study aimed to observe the morphological and molecular effect of laminin-1 doping to nanostructured implant surfaces in a rabbit model. Materials and Methods. Nanostructured implants were coated with laminin-1 (test; dilution, 100 μg/mL) and inserted into the rabbit tibiae. Noncoated implants were used as controls. After 2 weeks of healing, the implants were removed and subjected to morphological analysis using scanning electron microscopy (SEM) and gene expression analysis using the real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Results. SEM revealed bony tissue attachment for both control and test implants. Real-time RT-PCR analysis showed that the expression of osteoblast markers RUNX-2, osteocalcin, alkaline phosphatase, and collagen I was higher (1.62-fold, 1.53-fold, 1.97-fold, and 1.04-fold, resp.) for the implants modified by laminin-1 relative to the control. All osteoclast markers investigated in the study presented higher expression on the test implants than controls as follows: tartrate-resistant acid phosphatase (1.67-fold), calcitonin receptor (1.35-fold), and ATPase (1.25-fold). The test implants demonstrated higher expression of inflammatory markers interleukin-10 (1.53-fold) and tumour necrosis factor-α (1.61-fold) relative to controls. Conclusion. The protein-doped surface showed higher gene expression of typical genes involved in the osseointegration cascade than the control surface.

Stem cells in dentistry--Part II: Clinical applications

New technologies that facilitate solid alveolar ridge augmentation are receiving considerable attention in the field of prosthodontics because of the growing requirement for esthetic and functional reconstruction by dental implant treatments. Recently, several studies have demonstrated potential advantages for stem-cell-based therapies in regenerative treatments. Mesenchymal stem/stromal cells (MSCs) are now an excellent candidate for tissue replacement therapies, and tissue engineering approaches and chair-side cellular grafting approaches using autologous MSCs represent the clinical state of the art for stem-cell-based alveolar bone regeneration. Basic studies have revealed that crosstalk between implanted donor cells and recipient immune cells plays a key role in determining clinical success that may involve the recently observed immunomodulatory properties of MSCs. Part II of this review first overviews progress in regenerative dentistry to consider the implications of the stem cell technology in dentistry and then highlights cutting-edge stem-cell-based alveolar bone regenerative therapies. Factors that affect stem-cell-based bone regeneration as related to the local immune response are then discussed. Additionally, pre-clinical stem cell studies for the regeneration of teeth and other oral organs as well as possible applications of MSC-based immunotherapy in dentistry are outlined. Finally, the marketing of stem cell technology in dental stem cell banks with a view toward future regenerative therapies is introduced.

Influence of formalin fixation on the implant stability quotient and mechanical characteristics of bone

The implant stability quotient (ISQ) has been widely evaluated in clinical studies and animal experiments. However, accurate measurement is often difficult in animal models. In such cases, measurement of ISQ in bone is needed after formalin fixation. However, it is not yet clear how such fixation influences the measurement. The purpose of this study was to investigate the influence of formalin fixation on ISQ and the mechanical characteristics of bone. Fourteen tibias were harvested from rabbits; the samples from the left (length 60mm, control group) were soaked in saline and the samples from the right (length 60mm, fixation group) were fixed in 10% neutral-buffered formalin at 4°C for 4h. Three-point bending tests were done at 5mm/min to measure the maximum load and total absorbed energy. Twelve titanium implants (Brånemark System(®) Mk-III TiUnite, Nobel Biocare, Sweden) were placed into the edentulous molar site of the mandibles of 2 dogs and the ISQ was measured by Osstell(®) (control group) 3 months later. The implants involved in the bone block were then fixed for 4h (fixation group) and the ISQ measured. The maximum load values did not differ significantly between the control and fixation groups. Total absorbed energy was significantly higher in the control group than in the fixation group. ISQ did not differ significantly between the groups. These results suggest that formalin fixation of bone might affect some of the mechanical characteristics of bone, but not its ISQ.

Acceleration of segmental bone regeneration in a rabbit model by strontium-doped calcium polyphosphate scaffold through stimulating VEGF and bFGF secretion from osteoblasts

The development of suitable bioactive three-dimensional scaffold for the promotion of bone regeneration is critical in bone tissue engineering. The purpose of this study was to investigate in vivo osteogenesis of the porous strontium-doped calcium polyphosphate (SCPP) scaffolds for bone repair, as well as the relationship between osteogenic properties of SCPP scaffolds and the secretion of bFGF and VEGF from osteoblasts stimulated by SCPP. Besides, the advantages of scaffolds seeded with mesenchymal stem cells (MSCs) for bone repair were also studied. Firstly, the bone repair evaluation of scaffolds was performed on a rabbit segmental bony defects model over a period of 16 weeks by histology combined with X-ray microradiography. And then, in order to avoid the influence from the other factors such as hypoxia which emerge in vivo study and affect the secretion of VEGF and bFGF from host cells, human osteoblast-like cells (MG63) were seeded to SCPP, CPP and HA scaffolds in vitro to determine the ability of these scaffolds to stimulate the secretion of angiogenic growth factors (VEGF and bFGF) from MG63 and further explore the reason for the better osteogenic properties of SCPP scaffolds. The histological and X-ray microradiographic results showed that the SCPP scaffolds presented better osteogenic potential than CPP and HA scaffolds, when combined with MSCs, the SCPP scaffolds could further accelerate the bone repair. And the amounts of VEGF measured by ELISA assay in SCPP, CPP and HA groups after cultured for 7 days were about 364.989 pg/mL, 244.035 pg/mL and 232.785 pg/mL, respectively. Accordingly, the amounts of bFGF were about 27.085 pg/mL, 15.727 pg/mL and 8.326 pg/mL. The results revealed that the SCPP scaffolds significantly enhanced the bFGF and VEGF secretion compared with other scaffolds. The results presented in vivo and in vitro study demonstrated that the SCPP could accelerate bone formation through stimulating the secretion of VEGF and bFGF from osteoblasts, making it attractive for bone regeneration.

Effects of different growth factors and carriers on bone regeneration: a systematic review

OBJECTIVE

The application and subsequent investigations in the use of varied osteogenic growth factors in bone regeneration procedures have grown dramatically over the past several years. Owing to this rapid gain in popularity and documentation, a review was undertaken to evaluate the in vivo effects of growth factors on bone regeneration.

STUDY DESIGN

Using related key words, electronic databases (Medline, Embase, and Cochrane) were searched for articles published from 1999 to April 2010 to find growth factor application in bone regeneration in human or animal models.

RESULTS

A total of 63 articles were matched with the inclusion criteria of this study. Bone morphogenetic protein 2 (BMP-2) was the most studied growth factor. Carriers for the delivery, experimental sites, and methods of evaluation were different, and therefore articles did not come to a general agreement.

CONCLUSIONS

Within the limitations of this review, BMP-2 may be an appropriate growth factor for osteogenesis.

Stem cells in dentistry--part I: stem cell sources

Stem cells can self-renew and produce different cell types, thus providing new strategies to regenerate missing tissues and treat diseases. In the field of dentistry, adult mesenchymal stem/stromal cells (MSCs) have been identified in several oral and maxillofacial tissues, which suggests that the oral tissues are a rich source of stem cells, and oral stem and mucosal cells are expected to provide an ideal source for genetically reprogrammed cells such as induced pluripotent stem (iPS) cells. Furthermore, oral tissues are expected to be not only a source but also a therapeutic target for stem cells, as stem cell and tissue engineering therapies in dentistry continue to attract increasing clinical interest. Part I of this review outlines various types of intra- and extra-oral tissue-derived stem cells with regard to clinical availability and applications in dentistry. Additionally, appropriate sources of stem cells for regenerative dentistry are discussed with regard to differentiation capacity, accessibility and possible immunomodulatory properties.

Preparation and functional evaluation of cell aggregates incorporating gelatin microspheres with different degradabilities

The objective of this study was to investigate the viability and biological functions of cells in their aggregates incorporating gelatin microspheres with different degradabilities. After being prepared by a water-in-oil emulsion procedure, the gelatin microspheres were dehydrothermally crosslinked at 140°C for various time periods. In vitro degradation tests showed that the gelatin microspheres were slowly degraded slowly with an increase in the crosslinking time. When MC3T3-E1 cells were cultured with the gelatin hydrogel microspheres in the round U-bottom wells of 96-well microplates which had been coated with poly(vinyl alcohol), cell aggregates with homogeneously distributed gelatin microspheres were formed. A large amount of slowly degraded gelatin microspheres remained in the cell aggregates for long time periods, while a higher proliferation of MC3T3-E1 cells was observed. When evaluated as a measure of aerobic glycolysis, the ratio of l-lactic acid production:glucose consumption of MC3T3-E1 cells was lower for MC3T3-E1 cells in the cell aggregates incorporating slowly degraded gelatin microspheres than for aggregates incorporating rapidly degraded ones. The alkaline phosphatase activity and calcium content of MC3T3-E1 cells were higher for cell aggregates incorporating slowly degraded gelatin microspheres. It is possible that the incorporation of gelatin hydrogel microspheres with slow degradability enabled the permeation of oxygen and nutrients into the cell aggregates for longer time periods, resulting in better culture conditions for the survival, proliferation and differentiation of the cells.

COMPARATIVE MACROSCOPIC STUDY OF OSTEOCHONDRAL DEFECTS PRODUCED IN FEMURS OF RABBITS REPAIRED WITH BIOPOLYMER GEL CANE SUGAR

OBJECTIVE

To study the surface, coloring, consistency, continuity and healing of osteochondral defects produced in the femoral condyles of rabbits and filled with sugar cane biopolymer gel (SCBG), after 90, 120 and 180 days, and in comparison with a control group.

METHOD

Sixteen adult New Zealand white rabbits aged 6 to 7 months, weighing between 2 and 2.5 kg and without locomotor system abnormalities were studied. In all the animals, a defect was made in the femoral condyles of the right and left knees, measuring 3.2 mm in diameter and 4 mm in depth, using a trephine. The animals were divided into two groups: study group formed by the right knees, in which the medial and lateral condyles received implants of SCBG; and control group formed by the left knees, in which the medial and lateral condyles were allowed to heal naturally. The knees were assessed 90, 120 and 180 days after the operation. After the animals had been sacrificed, the anatomical specimens were resected and placed in Bouin's solution. They were then photographed with a Nikon Coolpix 5400(®) coupled to a Nikon SM2800(®) stereoscopic loupe, to analyze the surface, coloring, consistency, continuity and healing.

RESULTS

The results were evaluated using the chi-square test. There were no significant differences in the macroscopic assessments of healing between the study and control groups.

CONCLUSION

With regard to the surface, coloring, consistency, continuity and healing of the defects, the macroscopic appearance of the tissue repaired with SCBG was similar to that of the control group.

Preparation of stem cell aggregates with gelatin microspheres to enhance biological functions

The objective of this study is to improve the viability and osteogenic differentiation of cultured rat bone marrow-derived mesenchymal stem cells (MSC) by the use of gelatin hydrogel microspheres. Gelatin was dehydrothermally crosslinked at 140° C for 48 h in a water in oil emulsion state. When cultured with the gelatin hydrogel microspheres in round, U-bottomed wells of 96-well plates coated with poly(vinyl alcohol) MSC formed aggregates homogeneously incorporating the microspheres. The viability of the cell aggregates was significantly higher compared with that of aggregates formed without microspheres. MSC proliferation in the aggregates depended on the number and diameter of the incorporated microspheres. Higher MSC proliferation was observed for aggregates incorporating a greater number of larger gelatin microspheres. When evaluated as a measure of aerobic glycolysis the ratio of l-lactic acid production/glucose consumption in MSC was significantly lower for MSC cultured with gelatin microspheres than those without microspheres. MSC production of alkaline phosphatase (ALP) and sulfated glycosaminaglycan (sGAG) was examined to evaluate their potential osteogenic and chondrogenic differentiation. The amount of ALP produced was significantly higher for MSC aggregates cultured with gelatin microspheres than that of MSC cultured without microspheres. On the other hand, the amount of sGAG produced was significantly lower for MSC aggregates containing microspheres. It is concluded that the incorporation of gelatin hydrogel microspheres prevents the aggregated MSC suffering from a lack of oxygen, resulting in enhanced MSC aggregation and cell proliferation and osteogenic differentiation.

Mineralization of hydrogels for bone regeneration

Hydrogels are an important class of highly hydrated polymers that are widely investigated for potential use in soft tissue engineering. Generally, however, hydrogels lack the ability to mineralize, preventing the formation of chemical bonds with hard tissues such as bone. A recent trend in tissue engineering involves the development of hydrogels that possess the capacity to mineralize. The strategy that has attracted most interest has been the incorporation of inorganic phases such as calcium phosphate ceramics and bioglasses into hydrogel matrices. These inorganic particles act as nucleation sites that enable further mineralization, thus improving the mechanical properties of the composite material. A second route to create nucleation sites for calcification of hydrogels involves the use of features from the physiological mineralization process. Examples of these biomimetic mineralization strategies include (1) soaking of hydrogels in solutions that are saturated with respect to calcium phosphate, (2) incorporation of enzymes that catalyze deposition of bone mineral, and (3) incorporation of synthetic analogues to matrix vesicles that are the initial sites of biomineralization. Functionalization of the polymeric hydrogel backbone with negatively charged groups is a third mechanism to promote mineralization in otherwise inert hydrogels. This review summarizes the main strategies that have been developed in the past decade to calcify hydrogel matrices and render these hydrogels suitable for applications in bone regeneration.

Enhanced initial bone regeneration with inorganic polyphosphate-adsorbed hydroxyapatite

Inorganic polyphosphate (poly(P)) can promote binding between fibroblast growth factors and their receptors and enhance osteoblastic cell differentiation and calcification. This study evaluated the possibilities for poly(P) adsorbed onto interconnected porous calcium hydroxyapatite (IP-CHA) as a new bone regeneration material. Prepared 1%, 5%, 25% and 50% poly(P)/IP-CHA composites showed the elution peak of poly(P) between 15 and 20 min, respectively, with the highest value from 50% poly(P)/IP-CHA in vitro. Histologically, at 1 week of placement into the femur of rabbits, granulation tissue had penetrated into the pores in all composites and IP-CHA as a control. In contrast, at 2 weeks of placement, newly formed lamellar bone was found in all groups, although a higher amount of bone regeneration was obviously formed in the 25% and 50% poly(P)/IP-CHA with a significantly higher value of bone regeneration ratio of 50% poly(P)/IP-CHA. These results indicate that 25% and 50% poly(P)/IP-CHA composites may enhance initial bone regeneration.

The effect of a single remote injection of statin-impregnated poly (lactic-co-glycolic acid) microspheres on osteogenesis around titanium implants in rat tibia

The aim of this study was to evaluate the effects of newly developed injectable poly (lactic-co-glycolic acid) (PLGA) microspheres containing fluvastatin on osteogenesis around titanium implants in the rat tibia. After confirmation of the sustained-release profile of fluvastatin from the microspheres by an in vitro assay, the microspheres were administered to the back skin of the rats by a single transdermal injection. At 2 and 4 weeks after the implant surgery, the fluvastatin groups showed enhanced new bone formation around the titanium implants without any influence on the serum biochemistry. In addition, the fluvastatin groups showed increased three-point bending strengths of their femurs. The results of this study indicate that a single remote injection of PLGA/fluvastatin microspheres safely and successfully stimulated bone formation around titanium implants and increased the mechanical properties of bone.

Cell and biomolecule delivery for regenerative medicine

Regenerative medicine is an exciting field that aims to create regenerative alternatives to harvest tissues for transplantation. In this approach, the delivery of cells and biological molecules plays a central role. The scaffold (synthetic temporary extracellular matrix) delivers cells to the regenerative site and provides three-dimensional environments for the cells. To fulfil these functions, we design biodegradable polymer scaffolds with structural features on multiple size scales. To enhance positive cell-material interactions, we design nano-sized structural features in the scaffolds to mimic the natural extracellular matrix. We also integrate micro-sized pore networks to facilitate mass transport and neo tissue regeneration. We also design novel polymer devices and self-assembled nanospheres for biomolecule delivery to recapitulate key events in developmental and wound healing processes. Herein, we present recent work in biomedical polymer synthesis, novel processing techniques, surface engineering and biologic delivery. Examples of enhanced cellular/tissue function and regenerative outcomes of these approaches are discussed to demonstrate the excitement of the biomimetic scaffold design and biologic delivery in regenerative medicine.

Effect of combined application of bFGF and inorganic polyphosphate on bioactivities of osteoblasts and initial bone regeneration

Basic fibroblast growth factor (bFGF) and inorganic polyphosphate (poly(P)) have been recognized as therapeutic agents that enhance bone regeneration. It has also been shown that poly(P) may enhance the mitogenic activity of bFGF. The purpose of this study is to evaluate the combined effect of bFGF and poly(P) on bioactivities of osteoblasts and initial bone regeneration in vitro and in vivo. MC3T3-E1 cells were treated with bFGF, poly(P) or bFGF+poly(P), then subjected to cell proliferation assay, alkaline phosphatase (ALP) activity measurement, quantitative real-time reverse transcription-polymerase chain reaction and Alizarin S Red staining. In an in vivo study, bFGF-, poly(P)- and bFGF+poly(P)-modified interconnected porous hydroxyapatite (IPHA) complexes were fabricated, and placed into the femurs of rabbits to evaluate new bone formation histologically and histomorphometrically. The highest enhancement of cell proliferation were observed in those treated with bFGF+poly(P) on days 5 and 7. Cells treated with bFGF+poly(P) also exhibited increased ALP activity on days 5 and 10, up-regulated mRNA levels of osteocalcin and osteopontin, and enhanced calcification when compared to the non-treated cells. In vivo, the highest bone formation ratio was observed in bFGF+poly(P)-modified IPHA complexes. This study indicated that co-application of bFGF and poly(P) may provide enhanced bone formation by modulating cell proliferation and the mineralization process. It is anticipated that a combined application of bFGF and poly(P) can provide a novel method for bone regeneration in clinical use.

Basic fibroblast growth factor suspended in Matrigel improves titanium implant fixation in ovariectomized rats

Basic fibroblast growth factor (bFGF) has high potential for tissue regeneration; however, its in vivo effects are unpredictable due to the short-term survival. This study sought to evaluate the effects of bFGF suspended in Matrigel on the implant fixation in ovariectomized (OVX) rats. In vitro, the release kinetics of bFGF was tested using an immuno-ligand-assay. In vivo, eighty titanium implants were randomly divided into 4 groups and inserted in the tibiae of forty OVX rats: no treatment group, bFGF alone group, Matrigel alone group and bFGF+Matrigel group. At 3 months after implantation, tibiae were examined by histology, micro-CT and push-out test. We found that Matrigel could prolong the life span of bFGF in vitro with a sustained release during the 21 days. In vivo, bFGF or Matrigel alone had little effect on the fixation of implant in OVX rats, but bFGF suspended in Matrigel induced nearly 2-fold of peri-implant new bone formation and 4-fold of implant mechanical stability when compared to other 3 groups. The results of this study suggest that Matrigel could be used as a carrier of bFGF and prolonged its release around implant, which may improve implant fixation, especially in site of post-menopausal osteoporosis.