Stem cell regenerative therapy in alveolar cleft reconstruction

Stem Cell-Based Tissue Engineering for Cleft Defects: Systematic Review and Meta-Analysis

This study aimed to analyze the efficacy of stem cell-based tissue engineering for the treatment of alveolar cleft (AC) and cleft palate (CP) defects in animal models.

Systematic review and meta-analysis.

Preclinical studies on alveolar cleft repair in maxillofacial practice.

Electronic search was performed using PubMed, Embase, and Cochrane databases. Pre-clinical studies, where stem cell-based tissue engineering was used in the reconstruction of AC and CP in animal models were included. Quality of the selected articles was evaluated using SYRCLE (SYstematic Review Centre for Laboratory animal Experimentation).

Review of alveolar cleft bone augmentation interventions in preclinical models.

Outcome parameters registered were new bone formation (NBF) and/or bone mineral density (BMD).

Thirteen large and twelve small animal studies on AC (21) and CP (4) reconstructions were included. Studies had an unclear-to-high risk of bias. Bone marrow mesenchymal stem cells were the most widely used cell source. Meta-analyses for AC indicated non-significant benefits in favor of: (1) scaffold + cells over scaffold-only (NBF P = .13); and (2) scaffold + cells over empty control (NBF P = .66; BMD P = .31). Interestingly, dog studies using regenerative grafts showed similar to superior bone formation compared to autografts. Meta analysis for the CP group was not possible.

AC and CP reconstructions are enhanced by addition of osteogenic cells to biomaterials. Directions and estimates of treatment effect are useful to predict therapeutic efficacy and guide future clinical trials of bone tissue engineering.

Revisiting Recent Tissue Engineering Technologies in Alveolar Cleft Reconstruction

Tissue engineering and regenerative medicine have received significant attention in treating degenerative disorders and presented unique opportunities for researchers. The latest research on tissue engineering and regenerative medicine to reconstruct the alveolar cleft has been reviewed in this study. Three approaches have been used to reconstruct alveolar cleft: Studies that used only stem cells or biomaterials and studies that reconstructed alveolar defects by tissue engineering using a combination of stem cells and biomaterials. Stem cells, biomaterials, and tissue-engineered constructs have shown promising results in the reconstruction of alveolar defects. However, some contrary issues, including stem cell durability and scaffold stability, were also observed. It seems that more prospective and comprehensive studies should be conducted to fully clarify the exact dimensions of the stem cells and tissue engineering reconstruction method in the therapy of alveolar cleft.

Bone Tissue Engineering Strategies for Alveolar Cleft: Review of Preclinical Results and Guidelines for Future Studies

The current standard of care for an alveolar cleft defect is an autogenous bone graft, typically from the iliac crest. Given the limitations of alveolar bone graft surgery, such as limited supply, donor site morbidity, graft failure, and need for secondary surgery, there has been growing interest in regenerative medicine strategies to supplement and replace traditional alveolar bone grafts. Though there have been preliminary clinical studies investigating bone tissue engineering methods in human subjects, lack of consistent results as well as limitations in study design make it difficult to determine the efficacy of these interventions. As the field of bone tissue engineering is rapidly advancing, reconstructive surgeons should be aware of the preclinical studies informing these regenerative strategies. We review preclinical studies investigating bone tissue engineering strategies in large animal maxillary or mandibular defects and provide an overview of scaffolds, stem cells, and osteogenic agents applicable to tissue engineering of the alveolar cleft. An electronic search conducted in the PubMed database up to December 2021 resulted in 35 studies for inclusion in our review. Most studies showed increased bone growth with a tissue engineering construct compared to negative control. However, heterogeneity in the length of follow up, method of bone growth analysis, and inconsistent use of positive control groups make comparisons across studies difficult. Future studies should incorporate a pediatric study model specific to alveolar cleft with long-term follow up to fully characterize volumetric defect filling, cellular ingrowth, bone strength, tooth movement, and implant support.

Development of root resorption during orthodontic tooth movement after cleft repair using different grafting materials in rats

OBJECTIVE

The aim of the present study was to investigate the influence of three grafting materials for cleft repair on orthodontic tooth movement in rats.

MATERIALS AND METHODS

Artificial alveolar clefts were created in 21 Wistar rats and were repaired 4 weeks later using autografts, human xenografts and synthetic bone substitute (beta-tricalcium phosphate/hydroxyapatite [β-TCP/HA]). A further 4 weeks later, the first molar was moved into the reconstructed maxilla. Microfocus computed tomography (μCT) was performed six times (T0-T5) to assess the tooth movement and root resorption. After 8 weeks, the affected reconstructed jaw was resected for histopathological investigation.

RESULTS

Total distances reached ranged from 0.82 ± 0.72 mm (β-TCP/HA) to 0.67 ± 0.27 mm (autograft). The resorption was particularly determined at the mesiobuccal root. Descriptive tooth movement slowed and root resorption increased slightly. However, neither the radiological changes during tooth movement (µCT T1 vs. µCT T5: autograft 1.85 ± 0.39 mm³ vs. 2.38 ± 0.35 mm³, p = 0.30; human xenograft 1.75 ± 0.45 mm³ vs. 2.17 ± 0.26 mm³, p = 0.54; β-TCP/HA: 1.52 ± 0.42 mm³ vs. 1.88 ± 0.41 mm³, p = 0.60) nor the histological differences after tooth movement (human xenograft: 0.078 ± 0.05 mm²; β-TCP/HA: 0.067 ± 0.049 mm²; autograft: 0.048 ± 0.015 mm²) were statistically significant.

CONCLUSION

The autografts, human xenografts or synthetic bone substitute used for cleft repair seem to have a similar effect on the subsequent orthodontic tooth movement and the associated root resorptions.

CLINICAL RELEVANCE

Development of root resorptions seems to have a secondary role in choosing a suitable grafting material for cleft repair.

Advances in Tissue Engineering and Implications for Oral and Maxillofacial Reconstruction

BACKGROUND

Reconstructive surgery in the oral and maxillofacial region poses many challenges due to the complexity of the facial skeleton and the presence of composite defects involving soft tissue, bone and nerve defects.

METHODS

Current methods of reconstruction include autologous grafting techniques with local or regional rotational flaps or microvascular free flaps, allografts, xenografts and prosthetic devices.

RESULTS

Tissue engineering therapies utilizing stem cells provide promise for enhancing the current reconstructive options.

CONCLUSIONS

This article is a review on tissue engineering strategies applicable to specialists who treat oral and maxillofacial defects.

PRACTICAL IMPLICATIONS

We review advancements in hard tissue regeneration for dental rehabilitation, soft tissue engineering, nerve regeneration and innovative strategies for reconstruction of major defects.

A Chemotactic Functional Scaffold with VEGF-Releasing Peptide Amphiphiles Facilitates Bone Regeneration by BMP-2 in a Large-Scale Rodent Cranial Defect Model

BACKGROUND

Current common techniques for repairing calvarial defects by autologous bone grafting and alloplastic implants have significant limitations. In this study, the authors investigated a novel alternative approach to bone repair based on peptide amphiphile nanofiber gels that are engineered to control the release of vascular endothelial growth factor (VEGF) to recruit circulating stem cells to a site of bone regeneration and facilitate bone healing by bone morphogenetic protein-2 (BMP-2).

METHODS

VEGF release kinetics from peptide amphiphile gels were evaluated. Chemotactic functional scaffolds were fabricated by combining collagen sponges with peptide amphiphile gels containing VEGF. The in vitro and in vivo chemotactic activities of the scaffolds were evaluated by measuring mesenchymal stem cell migration, and angiogenic capability of the scaffolds was also evaluated. Large-scale rodent cranial bone defects were created to evaluate bone regeneration after implanting the scaffolds and other control materials.

RESULTS

VEGF was released from peptide amphiphile in a controlled-release manner. In vitro migration of mesenchymal stem cells was significantly greater when exposed to chemotactic functional scaffolds compared to control scaffolds. In vivo chemotaxis was evidenced by migration of tracer-labeled mesenchymal stem cells to the chemotactic functional scaffolds. Chemotactic functional scaffolds showed significantly increased angiogenesis in vivo. Successful bone regeneration was noted in the defects treated with chemotactic functional scaffolds and BMP-2.

CONCLUSIONS

The authors' observations suggest that this bioengineered construct successfully acts as a chemoattractant for circulating mesenchymal stem cells because of controlled release of VEGF from the peptide amphiphile gels. The chemotactic functional scaffolds may play a role in the future design of clinically relevant bone graft substitutes for large-scale bone defects.

Evaluation of different grafting materials for alveolar cleft repair in the context of orthodontic tooth movement in rats

To minimize the postoperative risks posed by grafting autologous transplants for cleft repair, efforts are being made to improve grafting materials for use as potential alternatives. The aim of this study was to compare the bone graft quality of different bone substitutes including the gold standard autografts during the healing processes after cleft repair in the context of orthodontic treatment. In 21 Wistar rats, a complete, continuity-interrupting cleft was created. After 4 weeks, cleft repair was performed using autografts from the hips’ ischial tuberosity, human xenografts, or synthetic bone substitutes [beta-tricalcium phosphate (β-TCP)/hydroxyapatite (HA)]. After another 4 weeks, the first molar movement was initiated in the reconstructed jaw for 8 weeks. The bone remodeling was analyzed in vivo using micro-computed tomography (bone mineral density and bone volume fraction) and histology (new bone formation). All the grafting materials were statistically different in bone morphology, which changed during the treatment period. The β-TCP/HA substitute demonstrated less resorption compared to the autologous and xenogeneic/human bone, and the autografts led to a stronger reaction in the surrounding bone. Histologically, the highest level of new bone formation was found in the human xenografts, and the lowest was found in the β-TCP/HA substitute. The differences between the two bone groups and the synthetic materials were statistically significant. Autografts were confirmed to be the gold standard in cleft repair with regard to graft integration. However, parts of the human xenograft seemed comparable to the autografts. Thus, this substitute could perhaps be used as an alternative after additional tissue-engineered modification.

Comparative evaluation of osteogenic differentiation potential of stem cells derived from dental pulp and exfoliated deciduous teeth cultured over granular hydroxyapatite based scaffold

BACKGROUND

Mesenchymal stem cells isolated from the dental pulp of primary and permanent teeth can be differentiated into different cell types including osteoblasts. This study was conducted to compare the morphology and osteogenic potential of stem cells from exfoliated deciduous teeth (SHED) and dental pulp stem cells (DPSC) in granular hydroxyapatite scaffold (gHA). Preosteoblast cells (MC3T3-E1) were used as a control group.

METHODOLOGY

The expression of stemness markers for DPSC and SHED was evaluated using reverse transcriptase-polymerase chain reaction (RT-PCR). Alkaline phosphatase assay was used to compare the osteoblastic differentiation of these cells (2D culture). Then, cells were seeded on the scaffold and incubated for 21 days. Morphology assessment using field emission scanning electron microscopy (FESEM) was done while osteogenic differentiation was detected using ALP assay (3D culture).

RESULTS

The morphology of cells was mononucleated, fibroblast-like shaped cells with extended cytoplasmic projection. In RT-PCR study, DPSC and SHED expressed GAPDH, CD73, CD105, and CD146 while negatively expressed CD11b, CD34 and CD45. FESEM results showed that by day 21, dental stem cells have a round like morphology which is the morphology of osteoblast as compared to day 7. The osteogenic potential using ALP assay was significantly increased (p < 0.01) in SHED as compared to DPSC and MC3T3-E1 in 2D and 3D cultures.

CONCLUSION

gHA scaffold is an optimal scaffold as it induced osteogenesis in vitro. Besides, SHED had the highest osteogenic potential making them a preferred candidate for tissue engineering in comparison with DPSC.

Stem Cells Regenerating the Craniofacial Skeleton: Current State-Of-The-Art and Future Directions

The craniofacial region comprises the most complex and intricate anatomical structures in the human body. As a result of developmental defects, traumatic injury, or neoplastic tissue formation, the functional and aesthetic intricacies of the face and cranium are often disrupted. While reconstructive techniques have long been innovated in this field, there are crucial limitations to the surgical restoration of craniomaxillofacial form and function. Fortunately, the rise of regenerative medicine and surgery has expanded the possibilities for patients affected with hard and soft tissue deficits, allowing for the controlled engineering and regeneration of patient-specific defects. In particular, stem cell therapy has emerged in recent years as an adjuvant treatment for the targeted regeneration of craniomaxillofacial structures. This review outlines the current state of the art in stem cell therapies utilized for the engineered restoration and regeneration of skeletal defects in the craniofacial region.

Innovative Molecular and Cellular Therapeutics in Cleft Palate Tissue Engineering

Clefts of the lip and/or palate are the most prevalent orofacial birth defects occurring in about 1:700 live human births worldwide. Early postnatal surgical interventions are extensive and staged to bring about optimal growth and fusion of palatal shelves. Severe cleft defects pose a challenge to correct with surgery alone, resulting in complications and sequelae requiring life-long, multidisciplinary care. Advances made in materials science innovation, including scaffold-based delivery systems for precision tissue engineering, now offer new avenues for stimulating bone formation at the site of surgical correction for palatal clefts. In this study, we review the present scientific literature on key developmental events that can go awry in palate development and the common surgical practices and challenges faced in correcting cleft defects. How key osteoinductive pathways implicated in palatogenesis inform the design and optimization of constructs for cleft palate correction is discussed within the context of translation to humans. Finally, we highlight new osteogenic agents and innovative delivery systems with the potential to be adopted in engineering-based therapeutic approaches for the correction of palatal defects. Impact statement Tissue-engineered scaffolds supplemented with osteogenic growth factors have attractive, largely unexplored possibilities to modulate molecular signaling networks relevant to driving palatogenesis in the context of congenital anomalies (e.g., cleft palate). Constructs that address this need may obviate current use of autologous bone grafts, thereby avoiding donor-site morbidity and other regenerative challenges in patients afflicted with palatal clefts. Combinations of biomaterials and drug delivery of diverse regenerative cues and biologics are currently transforming strategies exploited by engineers, scientists, and clinicians for palatal cleft repair.

Functional Validation of a New Alginate-based Hydrogel Scaffold Combined with Mesenchymal Stem Cells in a Rat Hard Palate Cleft Model

Background:

One of the major difficulties in cleft palate repair is the requirement for several surgical procedures and autologous bone grafting to form a bony bridge across the cleft defect. Engineered tissue, composed of a biomaterial scaffold and multipotent stem cells, may be a useful alternative for minimizing the non-negligible risk of donor site morbidity. The present study was designed to confirm the healing and osteogenic properties of a novel alginate-based hydrogel in palate repair.

Methods:

Matrix constructs, seeded with allogeneic bone marrow–derived mesenchymal stem cells (BM-MSCs) or not, were incorporated into a surgically created, critical-sized cleft palate defect in the rat. Control with no scaffold was also tested. Bone formation was assessed using microcomputed tomography at weeks 2, 4, 8, and 12 and a histologic analysis at week 12.

Results:

At 12 weeks, the proportion of bone filling associated with the use of hydrogel scaffold alone did not differ significantly from the values observed in the scaffold-free experiment (61.01% ± 5.288% versus 36.91% ± 5.132%; p = 0.1620). The addition of BM-MSCs stimulated bone formation not only at the margin of the defect but also in the center of the implant.

Conclusions:

In a relevant in vivo model of cleft palate in the rat, we confirmed the alginate-based hydrogel’s biocompatibility and real advantages for tissue healing. Addition of BM-MSCs stimulated bone formation in the center of the implant, demonstrating the new biomaterial’s potential for use as a bone substitute grafting material for cleft palate repair.

Extracellular Matrix Composition and Remodeling: Current Perspectives on Secondary Palate Formation, Cleft Lip/Palate, and Palatal Reconstruction

Craniofacial development comprises a complex process in humans in which failures or disturbances frequently lead to congenital anomalies. Cleft lip with/without palate (CL/P) is a common congenital anomaly that occurs due to variations in craniofacial development genes, and may occur as part of a syndrome, or more commonly in isolated forms (non-syndromic). The etiology of CL/P is multifactorial with genes, environmental factors, and their potential interactions contributing to the condition. Rehabilitation of CL/P patients requires a multidisciplinary team to perform the multiple surgical, dental, and psychological interventions required throughout the patient's life. Despite progress, lip/palatal reconstruction is still a major treatment challenge. Genetic mutations and polymorphisms in several genes, including extracellular matrix (ECM) genes, soluble factors, and enzymes responsible for ECM remodeling (e.g., metalloproteinases), have been suggested to play a role in the etiology of CL/P; hence, these may be considered likely targets for the development of new preventive and/or therapeutic strategies. In this context, investigations are being conducted on new therapeutic approaches based on tissue bioengineering, associating stem cells with biomaterials, signaling molecules, and innovative technologies. In this review, we discuss the role of genes involved in ECM composition and remodeling during secondary palate formation and pathogenesis and genetic etiology of CL/P. We also discuss potential therapeutic approaches using bioactive molecules and principles of tissue bioengineering for state-of-the-art CL/P repair and palatal reconstruction.

Importance of Stem Cell Transplantation in Cleft Lip and Palate Surgical Treatment Protocol

Cleft lip and palate is a congenital malformation that requires a multidisciplinary treatment that evolves pediatrician, obstetrics, fetal medicine, genetics, plastic surgery, orthodontics, speech therapist, nursery, and psychology. Actually, the authors believe that it could be possible to ad protocols to use stem cells.The intrauterine diagnosis leads to preborn parental orientation and better parental collaboration to accept a precocious multidisciplinary treatment. After birth the authors' protocol is: orthodontic devices, phonoaudiology, and surgical procedures.The authors' cleft lip and palate reconstructive surgery protocol demands several steps and begins at 4 to 6-month old with rhinocheiloplasty and soft palate closure at the same moment. The treatment sequence involves the hard palate surgery (8-18 months after the first surgical step), alveoloplasty (after 10 years old), and secondary rhinoplasty (after 14 years old).New ideas to use stem cells and blood from the umbilical cord and also blood from placenta are discussed to improve final surgical results. Maternal stem cells are easy to collect, there are no damage to the patient and mother, it is autologous and it could be very useful in the authors' protocol.Nine patients with clef lip and palate were operated and had stem cells from umbilical cord blood and placenta blood injected into the bone and soft tissue during the primary procedure (rhinocheiloplasty).The stem cells activity into soft tissue and bone were evaluated. Preliminary results have shown no adverse results and improvement at the inflammatory response. A treatment protocol with stem cells was developed. It had a long time follow-up of 10 years.

Volumetric comparison of autogenous bone and tissue-engineered bone replacement materials in alveolar cleft repair: a systematic review and meta-analysis

The goal of reconstruction of the alveolar cleft in patients with cleft lip and palate is to improve the quality of tissue, the structural stability, and increase the volume of bone. This study is a systematic review with meta-analysis of volumetric bony filling using autogenous bone and various tissue-engineered bone substitutes. We made an electronic search on MEDLINE, EMBASE, SCOPUS, WEB OF SCIENCE, "grey" publications (materials and research produced by organisations outside traditional channels for commercial or academic publishing and distribution), and relevant cross references according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies that reported the outcomes of volumetric grafting were included in the meta-analysis. Of 1276 studies, 26 were included in the meta-analysis. Pooled analysis of 25 studies that used autogenous bone showed a significant reduction in the volume of the cleft equivalent to 62.0% bone fill (95% CI 54.3 to 69.6), in contrast to 10 studies that used a tissue-engineered material and reported bone filling of 68.7% (95% CI 54.5 to 82.8). The estimated sizes of pooled effects across studies showed that there was no significant difference between the two major intervention groups (p value 0.901). Our statistical analysis showed that autogenous bone grafts did not differ significantly from tissue-engineered materials in their ability to fill clefts. Systematic review registration: International Prospective Register of Systematic Reviews, PROSPERO (CRD42017065045).

Evaluation of the Different Biomaterials Used in Alveolar Cleft Defects in Children

The aim of this study was to use a literature review to evaluate and compare the different biomaterials used in surgeries for the closure of the palatal and alveolar clefts as alternatives to isolated autografting. For the search strategy, the PubMed and Medline databases were used with the indexing terms "'cleft palate' (Mesh), 'biocompatible materials' (Mesh), and 'dentistry' (Mesh)." There was no restriction on language or publication time. After the research, 26 articles were found, and then, only the filter for clinical trials was selected. With this methodology, five articles were selected. The full texts have been carefully evaluated. The main issue among the five selected articles was the closure of a cleft palate and/or alveolar bone with the use of different types of biomaterials (e.g. autogenous bone from the iliac crest and chin, deproteinized bovine bone (DBB), β-tricalcium phosphate (β-TCP), synthetic resorption based on calcium sulfate, and the engineering of bone tissue); they evaluated preoperative and postoperative clinically and through imaging tests. The autogenous bone associated with DBB or β-TCP significantly reduces the amount of autogenous bone harvested from the iliac crest, morbidity, and the hospitalization of the patient, and the isolated use of bovine hydroxyapatite resulted in lower bone density compared to that from autogenous bone.

Bone regeneration using composite non-demineralized xenogenic dentin with beta-tricalcium phosphate in experimental alveolar cleft repair in a rabbit model

Background

Alveolar cleft repair is performed via bone grafting procedure to restore the dental arch continuity. A suitable bone substitute materials should possess osteoinductive and osteoconductive properties, to promote new bone formation, along with a slowly resorbable scaffold that is subsequently replaced with functionally viable bone. Calcium phosphate biomaterials have long proved their efficacy as bone replacement materials. Dentin in several forms has also demonstrated its possibility to be used as bone graft replacement material in several studies. The purpose of this study was to evaluate bone regeneration pattern and quantify bone formation after grafting pre-established experimental alveolar clefts defects model in rabbits using composite xenogenic dentin and β-TCP in comparison to β-TCP alone.

Methods

Unilateral alveolar cleft defects were created in 16 New Zealand rabbits according to previously described methodology. Alveolar clefts were allowed 8 weeks healing period. 8 defects were filled with β-TCP, whereas 8 defects filled with composite xenogenic dentin with β-TCP. Bone regeneration of the healed defects was compared at the 8 weeks after intervention. Quantification of bone formation was analyzed using micro-computed tomography (µCT) and histomorphometric analysis.

Results

µCT and histomorphometric analysis revealed that defects filled with composite dentin/β-TCP showed statistically higher bone volume fraction, bone mineral density and percentage residual graft volume when compared to β-TCP alone. An improved surgical handling of the composite dentin/β-TCP graft was also noted.

Conclusions

Composite xenogenic dentin/β-TCP putty expresses enhanced bone regeneration compared to β-TCP alone in the reconstruction of rabbit alveolar clefts defects.

Peroxisome Proliferator-Activated Receptor-γ Coactivator-1α (PGC-1α) Regulates the Expression of B-Cell Lymphoma/Leukemia-2 (Bcl-2) and Promotes the Survival of Mesenchymal Stem Cells (MSCs) via PGC-1α/ERRα Interaction in the Absence of Serum, Hypoxia, and High Glucose Conditions

BACKGROUND To study the effect of estrogen-related receptor α (ERRα) and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) on mesenchymal stem cells (MSCs) apoptosis, and further investigated its detailed molecular mechanisms in the absence of serum, hypoxia, and high glucose conditions. MATERIAL AND METHODS In our study, we first evaluated the expression rates of CD14, CD34, CD45, CD44, CD29, and Sca-1 surface markers on MSCs by flow cytometry. Then, the ability of osteogenic and fatty differentiation of MSCs was determined by osteogenic differentiation and adipogenesis reagent kit. Next, Annexin V-APC/7-AAD apoptosis kit was used for detecting the apoptosis rate of MSCs. RT-PCR and Western blotting were used for detection of mRNA expression and proteins expression, respectively. RESULTS Our data showed that the MSCs used in our study were capable of self-renewal and differentiating into many cell lineages, such as osteogenic differentiation and adipogenesis. Our results further showed that over-expression of PGC-1α could protect MSCs from apoptosis induced by rotenone. We also found that PGC-1α over-expression could enhance the expression of anti-apoptotic gene Bcl-2, and inhibit the expression of pro-apoptotic gene Bax in MSCs. In addition, our data demonstrated that PGC-1α could induce upregulation of Bcl-2 and further promote the survival of MSCs by interacting with ERRα. CONCLUSIONS In the absence of serum, hypoxia and high glucose conditions, PGC-1α can regulate the expression of Bcl-2 and promote the survival of MSCs via PGC-1α/ERRα interaction.

Odontogenic differentiation potential of human dental pulp cells cultured on a calcium-aluminate enriched chitosan-collagen scaffold

OBJECTIVE

The study aims to evaluate the odontogenic potential of human dental pulp cells (HDPCs) in contact with an experimental porous chitosan-collagen scaffold (CHC) enriched or not with a mineral phase of calcium-aluminate (CHC-CA).

MATERIAL AND METHODS

To assess the chemotactic effect of the materials, we placed HDPCs seeded on transwell membranes in intimate contact with the CHC or CHC-CA surface, and the cell migration was monitored for 48 h. Additionally, cells were seeded onto the material surface, and the viability and proliferation were evaluated at several time points. To assess the odontoblastic differentiation, we evaluated ALP activity, DSPP/DMP-1 gene expression, and mineralized matrix deposition. HDPCs cultured onto a polystyrene surface (monolayer) were used as negative control group.

RESULTS

The experimental CHC-CA scaffold induced intense migration of HDPCs through transwell membranes, with cells attaching to and spreading on the material surface after 24-h incubation. Also, the HDPCs seeded onto the CHC-CA scaffold were capable of migrating inside it, remaining viable and featuring a proliferative rate more rapid than that of CHC and control groups at 7 and 14 days of cell culture. At long-term culture, cells in the CHC-CA scaffold featured the highest deposition of mineralized matrix and expression of odontoblastic markers (ALP activity and DSPP/DMP-1 gene expression).

CONCLUSIONS

According to the results, the CHC-CA scaffold is a bioactive and cytocompatible material capable of increasing the odontogenic potential of human pulp cells. Based on analysis of the positive data obtained in this study, one can suggest that the CHC-CA scaffold is an interesting future candidate for the treatment of exposed pulps.

CLINICAL RELEVANCE

The experimental scaffold composed by a chitosan-collagen matrix mineralized with calcium aluminate seems to be an interesting candidate for in vivo application as a cell-free approach to dentin tissue engineering, which may open a new perspective for the treatment of exposed pulp tissue.

A rabbit model for experimental alveolar cleft grafting

Objectives

The purpose of the present study was to develop an animal model for creating alveolar cleft defects with properly simulated clinical defect environment for tissue-engineered bone-substitute materials testing without compromising the health of the animal. Cleft creation surgery was aimed at creating a complete alveolar cleft with a wide bone defect with an epithelial lining (oral mucosa) overlying the cleft defect.

Methods

A postmortem skull of a New Zealand White (NZW) rabbit skull (Oryctolagus cuniculus) underwent an osteological and imaging survey. A pilot postmortem surgery was conducted to confirm the feasability of a surgical procedure and the defect was also radiologically confirmed and illustrated with micro-computed tomography. Then, a surgical in vivo model was tested and evaluated in 16 (n = 16) 8-week-old NZW rabbits to create in vivo alveolar cleft creation surgery.

Results

Clinical examination and imaging analysis 8 weeks after cleft creation surgery revealed the establishment of a wide skeletal defect extending to the nasal mucosa simulating alveolar clefts in all of the rabbits.

Conclusions

Our surgical technique was successful in creating a sizable and predictable model for bone grafting material testing. The model allows for simulating the cleft site environment and can be used to evaluate various bone grafting materials in regard to efficacy of osteogenesis and healing potential without compromising the health of the animal.

Application of tissue-engineered bone grafts for alveolar cleft osteoplasty in a rodent model

OBJECTIVES

The clinical standard for alveolar cleft osteoplasty is augmentation with autologous bone being available in limited amounts and might be associated with donor site morbidity. The aim of the present study was the creation of tissue-engineered bone grafts and their in vivo evaluation regarding their potential to promote osteogenesis in an alveolar cleft model.

MATERIALS AND METHODS

Artificial bone defects with a diameter of 3.3 mm were created surgically in the palate of 84 adult Lewis rats. Four experimental groups (n = 21) were examined: bovine hydroxyl apatite/collagen (bHA) without cells, bHA with undifferentiated mesenchymal stromal cells (MSC), bHA with osteogenically differentiated MSC. In a control group, the defect remained empty. After 6, 9 and 12 weeks, the remaining defect volume was assessed by cone beam computed tomography. Histologically, the remaining defect width and percentage of bone formation was quantified.

RESULTS

After 12 weeks, the remaining defect width was 60.1% for bHA, 74.7% for bHA with undifferentiated MSC and 81.8% for bHA with osteogenically differentiated MSC. For the control group, the remaining defect width measured 46.2% which was a statistically significant difference (p < 0.001).

CONCLUSIONS

The study design was suitable to evaluate tissue-engineered bone grafts prior to a clinical application. In this experimental set-up with the described maxillary defect, no promoting influence on bone formation of bone grafts containing bHA could be confirmed.

CLINICAL RELEVANCE

The creation of a sufficient tissue-engineered bone graft for alveolar cleft osteoplasty could preserve patients from donor site morbidity.

Corrosion resistance characteristics of a Ti-6Al-4V alloy scaffold that is fabricated by electron beam melting and selective laser melting for implantation in vivo

The purpose of this study is to determine the corrosion resistance of Ti-6Al-4V alloy fabricated with electron beam melting and selective laser melting for implantation in vivo. Ti-6Al-4V alloy specimens were fabricated with electron beam melting (EBM) and selective laser melting (SLM). A wrought form of Ti-6Al-4V alloy was used as a control. Surface morphology observation, component analysis, corrosion resistance experimental results, electrochemical impedance spectroscopy, crevice corrosion resistance experimental results, immersion test and metal ions precipitation analysis were processed, respectively. The thermal stability of EBM specimen was the worst, based on the result of open circuit potential (OCP) result. The result of electrochemical impedance spectroscopy indicated that the corrosion resistance of the SLM specimen was the best under the low electric potential. The result of potentiodynamic polarization suggested that the corrosion resistance of the SLM specimen was the best under the low electric potential (<1.5V) and EBM specimen was the best under the high electric potential (>1.5V).The crevice corrosion resistance of the EBM specimen was the best. The corrosion resistance of SLM specimen was the best, based on the result of immersion test. The content of Ti, Al and V ions of EBM, SLM and wrought specimens was very low. In general, the scaffolds that were fabricated with EBM and SLM had good corrosion resistance, and were suitable for implantation in vivo.