Effect of data binning and frame averaging for micro-CT image acquisition on the morphometric outcome of bone repair assessment.

Despite the current advances in micro-CT analysis, the influence of some image acquisition parameters on the morphometric assessment outcome have not been fully elucidated. The aim of this study was to determine whether data binning and frame averaging affect the morphometric outcome of bone repair assessment using micro-CT. Four Wistar rats' tibiae with a surgically created bone defect were imaged with micro-CT six times each, frame averaging set to 1 and 2, and data binning set to 1, 2 and 4, for each of the averaging values. Two-way ANOVA followed by Bonferroni tests assessed the significance of frame averaging and data binning on a set of morphometric parameters assessed in the image volumes (p < 0.01). The effect of frame averaging was not significant for any of the assessed parameters. Increased data binning led to larger trabecular thickness. In contrast, smaller bone volume fraction and bone volume were found as data binning increased. Trabeculae number and trabecular separation were not influenced by any of the parameters. In conclusion, the morphometric outcome of bone repair assessment in micro-CT demonstrated dependency upon data binning, but not frame averaging. Therefore, image acquisition of small anatomical structures (e.g., rat trabeculae) should be performed without data binning.

Assessment of human ovarian follicular fluid derived mesenchymal stem cells in chitosan/PCL/Zn scaffold for bone tissue regeneration.

Bone tissue engineering compasses the use of mesenchymal stem cells (MSCs) along with engineered biomaterial construct to augment bone regeneration. Till now, MSCs were isolated from various sources and used in cellular constructs. For the first time, in this study, MSCs were isolated from human Ovarian Follicular Fluid (OFF) and characterized by CD 44+ and CD 105+ markers via confocal microscopy and flow cytometry. Additionally, MSCs stemness, proliferation and colony-forming unit ability, multi-lineage differentiation potential were also studied. To test its suitability for bone tissue engineering applications, we grew the MSCs with the conditioned medium obtained from biocomposite scaffold by fusing a natural polymer, Chitosan (CS) and a synthetic polymer, Polycaprolactone (PCL) and the scaffold were coated with Zinc divalent ions to impart osteogenic properties. The physico-chemical characterization of scaffold, such as FTIR, XRD, and SEM studies was carried out. The biological characterization showed that the scaffolds were compatible with MSCs and promoted osteoblast differentiation which was confirmed at both cellular and molecular levels. The cellular construct increased calcium deposition, analyzed by alizarin red staining and ALP activity at cellular level. At the molecular level, the osteoblast markers expression such as Runx2 and type 1 collagen mRNAs, and osteonectin (ON) and osteocalcin (OC) secretory proteins were increased in the presence of scaffold. Overall, the current study recommends that MSCs can be easily obtained from human waste OFF, and grown in standard in vitro conditions. Successful growth of such MSCs with CS/PCL/Zn scaffold opens new avenues in utilizing the cell source for bone tissue engineering.

Quantitative assessment of acetabular bone defects: A study of 50 computed tomography data sets.

OBJECTIVES: Acetabular bone defect quantification and classification is still challenging. The objectives of this study were to suggest and define parameters for the quantification of acetabular bone defects, to analyze 50 bone defects and to present the results and correlations between the defined parameters. METHODS: The analysis was based on CT-data of pelvises with acetabular bone defects and their reconstruction via a statistical shape model. Based on this data, bone volume loss and new bone formation were analyzed in four sectors (cranial roof, anterior column, posterior column, and medial wall). In addition, ovality of the acetabulum, lateral center-edge angle, implant migration, and presence of wall defects were analyzed and correlations between the different parameters were assessed. RESULTS: Bone volume loss was found in all sectors and was multidirectional in most cases. Highest relative bone volume loss was found in the medial wall with median and [25, 75]-percentile values of 72.8 [50.6, 95.0] %. Ovality, given as the length to width ratio of the acetabulum, was 1.3 [1.1, 1.4] with a maximum of 2.0, which indicated an oval shape of the defect acetabulum. Lateral center-edge angle was 30.4° [21.5°, 40.4°], which indicated a wide range of roof coverage in the defect acetabulum. Total implant migration was 25.3 [14.8, 32.7] mm, whereby cranial was the most common direction. 49/50 cases showed a wall defect in at least one sector. It was observed that implant migration in cranial direction was associated with relative bone volume loss in cranial roof (R = 0.74) and ovality (R = 0.67). CONCLUSION: Within this study, 50 pelvises with acetabular bone defects were successfully analyzed using six parameters. This could provide the basis for a novel classification concept which would represent a quantitative, objective, unambiguous, and reproducible classification approach for acetabular bone defects.

Calvarial Model of Bone Augmentation in Rabbit for Assessment of Bone Growth and Neovascularization in Bone Substitution Materials.

The basic principle of the rabbit calvarial model is to grow new bone tissue vertically on top of the cortical part of the skull. This model allows assessment of bone substitution materials for oral and craniofacial bone regeneration in terms of bone growth and neovascularization support. Once animals are anesthetized and ventilated (endotracheal intubation), four cylinders made of polyether ether ketone (PEEK) are screwed onto the skull, on both sides of the median and coronal sutures. Five intramedullary holes are drilled within the bone area delimited by each cylinder, allowing influx of bone marrow cells. The material samples are placed into the cylinders which are then closed. Finally, the surgical site is sutured, and animals are awaken. Bone growth may be assessed on live animals by using microtomography. Once animals are euthanized, bone growth and neovascularization may be evaluated by using microtomography, immune-histology and immunofluorescence. As the evaluation of a material requires maximum standardization and calibration, the calvarial model appears ideal. Access is very easy, calibration and standardization are facilitated by the use of defined cylinders and four samples may be assessed simultaneously. Furthermore, live tomography may be used and ultimately a large decrease in animals to be euthanized may be anticipated.

Assessment of Hedgehog Signaling Pathway Activation for Craniofacial Bone Regeneration in a Critical-Sized Rat Mandibular Defect.

IMPORTANCE: Osseous craniofacial defects are currently reconstructed with bone grafting, rigid fixation, free tissue transfer, and/or recombinant human bone morphogenetic protein 2. Although these treatment options often have good outcomes, they are associated with substantial morbidity, and many patients are not candidates for free tissue transfer. OBJECTIVE: To assess whether polysaccharide-based scaffold (PS) constructs that are cross-linked with smoothened agonist (SAG), vascular endothelial growth factor (VEGF), and bone morphogenetic protein 6 (BMP-6) would substantially increase bone regeneration. DESIGN, SETTING, AND PARTICIPANTS: This animal model study was conducted at the University of Virginia School of Medicine Cui Laboratory from March 1, 2017, to June 30, 2017. Thirty-three 10-week-old female Lewis rats were acquired for the study. Bilateral nonsegmental critical-sized defects were created in the angle of rat mandibles. The defects were either left untreated or filled with 1 of the 9 PSs. The rats were killed after 8 weeks, and bone regeneration was evaluated using microcomputed tomographic imaging and mechanical testing. Analysis of variance testing was used to compare the treatment groups. MAIN OUTCOMES AND MEASURES: Blinded analysis and computer analysis of the microcomputed tomographic images were used to assess bone regeneration. RESULTS: In the 33 female Lewis rats, minimal healing was observed in the untreated mandibles. Addition of SAG was associated with increases in bone regeneration and bone density in all treatment groups, and maximum bone healing was seen in the group with BMP-6, VEGF, and SAG cross-linked to PS. For each of the 5 no scaffold group vs BMP-6, VEGF, and SAG cross-linked to PS group comparisons, mean defect bone regeneration was 4.14% (95% CI, 0.94%-7.33%) vs 66.19% (95% CI, 54.47%-77.90%); mean bone volume, 14.52 mm3 (95% CI, 13.07-15.97 mm3) vs 20.87 mm3 (95% CI, 14.73- 27.01 mm3); mean bone surface, 68.97 mm2 (95% CI, 60.08-77.85 mm2) vs 96.77 mm2 (95% CI, 76.11-117.43 mm2); mean ratio of bone volume to total volume, 0.11 (95% CI, 0.10-0.11) vs 0.15 (95% CI, 0.10-0.19); and mean connectivity density 0.03 (95% CI, 0.02-0.05) vs 0.32 (95% CI, 0.25-0.38). On mechanical testing, mandibles with untreated defects broke with less force than control mandibles in which no defect was made, although this force did not reach statistical significance. No significant difference in force to fracture was observed among the treatment groups. CONCLUSIONS AND RELEVANCE: In this rat model study, activation of the hedgehog signaling pathway using smoothened agonist was associated with increased craniofacial bone regeneration compared with growth factors alone, including US Food and Drug Administration-approved recombinant human bone morphogenetic protein 2. Pharmaceuticals that target this pathway may offer a new reconstructive option for bony craniofacial defects as well as nonunion and delayed healing fractures. LEVEL OF EVIDENCE: NA.

Quality assessment of systematic reviews on vertical bone regeneration.

The aim of this study was to evaluate and compare the quality of systematic reviews of vertical bone regeneration techniques, using two quality-assessment tools (AMSTAR and ROBIS). An electronic literature search was conducted to identify systematic reviews or meta-analyses that would evaluate at least one of the following outcomes: implant survival, success rates, complications or bone gain after vertical ridge augmentation. Methodological quality assessment was performed by two independent evaluators. Results were compared between reviewers, and reliability measures were calculated using the Holsti's method® and Cohen's kappa. Seventeen systematic reviews were included, of which seven presented meta-analysis. Mean ±95% confidence interval AMSTAR score was 6.35 [4.74;7.97], with higher scores being correlated with a smaller risk of bias (Pearson's correlation coefficient=-0.84; P<0.01). Cohen's inter-examiner kappa showed substantial agreement for both checklists. From the available evidence, we ascertained that, regardless of the technique used, it is possible to obtain vertical bone gains. Implant success in regenerated areas was similar to implants placed in pristine bone with results equating between 61.5% and 100% with guided bone regeneration being considered the most predictable technique regarding bone stability, while distraction osteogenesis achieved the biggest bone gains with the highest risk of possible complications.

Brillouin spectroscopy and radiography for assessment of viscoelastic and regenerative properties of mammalian bones.

Biomechanical properties of mammalian bones, such as strength, toughness, and plasticity, are essential for understanding how microscopic-scale mechanical features can link to macroscale bones' strength and fracture resistance. We employ Brillouin light scattering (BLS) microspectroscopy for local assessment of elastic properties of bones under compression and the efficacy of the tissue engineering approach based on heparin-conjugated fibrin (HCF) hydrogels, bone morphogenic proteins, and osteogenic stem cells in the regeneration of the bone tissues. BLS is noninvasive and label-free modality for probing viscoelastic properties of tissues that can give information on structure-function properties of normal and pathological tissues. Results showed that MCS and BPMs are critically important for regeneration of elastic and viscous properties, respectively, HCF gels containing combination of all factors had the best effect with complete defect regeneration at week nine after the implantation of bone grafts and that the bones with fully consolidated fractures have higher values of elastic moduli compared with defective bones.

Bioactive glass added to autogenous bone graft in maxillary sinus augmentation: a prospective histomorphometric, immunohistochemical, and bone graft resorption assessment.

OBJECTIVE: The aim of this study was to compare the bone resorption rate, histomorphometry and immunohistochemical findings of bioactive glass (Biogran; Biomet, Warsaw, IN, USA) mixed with autogenous bone grafts (1:1) and autogenous bone graft isolate in maxillary sinus elevation surgery. MATERIAL AND METHODS: A total of 9 maxillary sinuses were grafted with Biogran with autogenous bone graft (group 1) and 12 were mixed with autogenous bone graft (group 2). Postoperative cone beam computed tomography (CBCT) was used to measure the initial graft volume after 15 days (T1), and 6 months later, another CBCT scan was performed to evaluate the final graft volume (T2) and determine the graft resorption rate. The resorption outcomes were 37.9%±18.9% in group 1 and 45.7%±18.5% in group 2 (P=0.82). After 6 months, biopsies were obtained concurrent with the placement of dental implants; these implants were subjected to histomorphometric analysis and immunohistochemical analysis for tartrate-resistant acid phosphatase (TRAP). RESULTS: The average bone formation in group 1 was 36.6%±12.9 in the pristine bone region, 33.2%±13.3 in the intermediate region, and 45.8%±13.8 in the apical region; in group 2, the values were 34.4%±14.4, 35.0%±13.9, and 42.0%±16.6 of new bone formation in the pristine bone, intermediate, and apical regions, respectively. Immunostaining for TRAP showed poor clastic activity in both groups, which can indicate that those were in the remodeling phase. CONCLUSIONS: The similarity between the groups in the formation and maintenance of the graft volume after 6 months suggests that the bioactive glass mixed with autogenous bone (1:1) can be used safely as a bone substitute for the maxillary sinus lift.

Assessment of Reamer Irrigator Aspirator System (RIA) filtrate for its osteoinductive potential in a validated animal model.

PURPOSE: Previous studies indicate that Reamer Irrigator Aspirator (RIA) filtrate contains proteins that have the potential to stimulate bone healing. This study aimed to determine the osteoinductive capabilities of RIA filtrate in a validated in vivo model. METHODS: With Institutional Review Board approval, RIA filtrates from 9 patients were collected. The filtrate was processed to remove cells and inorganic particles. A portion of each sample was set aside for protein analysis while the remainder was lyophilized and prepared for implantation. With Animal Care and Use Committee approval, athymic mice (n = 16; 32 hind limbs) were randomly assigned to 1 of 4 groups (n = 8 limbs per group) for percutaneous gastrocnemius muscle injection of demineralized bone matrix (DBM) (10 mg), lyophilized RIA powder (10 mg), RIA liquid (10 mg of lyophilized RIA powder in 100ul phosphate buffered saline (PBS)), or DBM (10 mg) + RIA liquid (10 mg in 100ul PBS). Radiographs were obtained 2, 4, and 8 weeks after injection. At 8 weeks, mice were sacrificed and the entire gastrocnemius muscle from each hind limb was collected and processed for histologic examination. Histological sections and radiographs were assessed for ossification/calcification. Data were compared for statistically significant (p < 0.05) differences among groups and strong (R > 0.7) correlations between outcome measures. RESULTS: The protein composition of RIA filtrates was consistent among patients and matched previous data. For all groups, radiographic scores were significantly (p < 0.014) higher (more calcification/ossification) at 8 weeks compared to 2 weeks. Radiographic scores for the DBM and DBM + RIA liquid groups were significantly higher than RIA liquid and RIA powder at 4 weeks and 8 weeks (p < 0.019 and p < 0.049, respectively). Histologic scores were significantly (p = 0.004) higher in the DBM + RIA liquid group compared to the RIA liquid group at 8 weeks. Histologic scores showed strong correlations (r > 0.77) to radiographic scores for all groups. CONCLUSION: RIA filtrate liquid and powder were osteoinductive in vivo with new bone formation being most abundant using a combination of DBM and RIA filtrate in this validated animal model. RIA filtrate has potential for clinical use in augmenting bone healing treatments.

Bioactive glass added to autogenous bone graft in maxillary sinus augmentation: a prospective histomorphometric, immunohistochemical, and bone graft resorption assessment

Abstract Objective The aim of this study was to compare the bone resorption rate, histomorphometry and immunohistochemical findings of bioactive glass (Biogran; Biomet, Warsaw, IN, USA) mixed with autogenous bone grafts (1:1) and autogenous bone graft isolate in maxillary sinus elevation surgery. Material and Methods A total of 9 maxillary sinuses were grafted with Biogran with autogenous bone graft (group 1) and 12 were mixed with autogenous bone graft (group 2). Postoperative cone beam computed tomography (CBCT) was used to measure the initial graft volume after 15 days (T1), and 6 months later, another CBCT scan was performed to evaluate the final graft volume (T2) and determine the graft resorption rate. The resorption outcomes were 37.9%±18.9% in group 1 and 45.7%±18.5% in group 2 (P=0.82). After 6 months, biopsies were obtained concurrent with the placement of dental implants; these implants were subjected to histomorphometric analysis and immunohistochemical analysis for tartrate-resistant acid phosphatase (TRAP). Results The average bone formation in group 1 was 36.6%±12.9 in the pristine bone region, 33.2%±13.3 in the intermediate region, and 45.8%±13.8 in the apical region; in group 2, the values were 34.4%±14.4, 35.0%±13.9, and 42.0%±16.6 of new bone formation in the pristine bone, intermediate, and apical regions, respectively. Immunostaining for TRAP showed poor clastic activity in both groups, which can indicate that those were in the remodeling phase. Conclusions The similarity between the groups in the formation and maintenance of the graft volume after 6 months suggests that the bioactive glass mixed with autogenous bone (1:1) can be used safely as a bone substitute for the maxillary sinus lift.

Quantitative assessment of the regenerative and mineralogenic performances of the zebrafish caudal fin.

The ability of zebrafish to fully regenerate its caudal fin has been explored to better understand the mechanisms underlying de novo bone formation and to develop screening methods towards the discovery of compounds with therapeutic potential. Quantifying caudal fin regeneration largely depends on successfully measuring new tissue formation through methods that require optimization and standardization. Here, we present an improved methodology to characterize and analyse overall caudal fin and bone regeneration in adult zebrafish. First, regenerated and mineralized areas are evaluated through broad, rapid and specific chronological and morphometric analysis in alizarin red stained fins. Then, following a more refined strategy, the intensity of the staining within a 2D longitudinal plane is determined through pixel intensity analysis, as an indicator of density or thickness/volume. The applicability of this methodology on live specimens, to reduce animal experimentation and provide a tool for in vivo tracking of the regenerative process, was successfully demonstrated. Finally, the methodology was validated on retinoic acid- and warfarin-treated specimens, and further confirmed by micro-computed tomography. Because it is easily implementable, accurate and does not require sophisticated equipment, the present methodology will certainly provide valuable technical standardization for research in tissue engineering, regenerative medicine and skeletal biology.

Use of a formwork in the induced membrane technique: Relevance and technical note.

The induced membrane technique is used for bone reconstruction. It is based on the osteoinductive properties of a membrane induced by the insertion of a PMMA cement spacer. We will describe a simple, cost-effective method in which the body of a syringe is used to facilitate the cement introduction, allow insertion of a regular spacer, contain the cement volume in the extension of the diaphysis and protect the underlying tissues from the exothermic reaction during PMMA polymerisation.

Assessment of bone healing ability of calcium phosphate cements loaded with platelet lysate in rat calvarial defects.

Injectable calcium phosphate cements have been used as a valid alternative to autologous bone grafts for bone augmentation with the additional advantage of enabling minimally invasive implantation procedures and for perfectly fitting the tissue defect. Nevertheless, they have low biodegradability and lack adequate biochemical signaling to promote bone healing and remodeling. In previous in vitro studies, we observed that the incorporation of platelet lysate directly into the cement paste or loaded in hyaluronic acid microspheres allowed to modulate the cement degradation and the in vitro expression of osteogenic markers in seeded human adipose derived stem cells. The present study aimed at investigating the possible effect of this system in new bone formation when implanted in calvarial bilateral defects in rats. Different formulations were assessed, namely plain calcium phosphate cements, calcium phosphate cements loaded with human platelet lysate, hybrid injectable formulations composed of the calcium phosphate cement incorporating hyaluronin acid non-loaded microparticles (20% hyaluronin acid) or with particles loaded with platelet lysate. The degradability and new bone regrowth were evaluated in terms of mineral volume in the defect, measured by micro-computed tomography and histomorphometric analysis upon 4, 8 and 12 weeks of implantation. We observed that the incorporation of hyaluronin acid microspheres induced an overly rapid cement degradation, impairing the osteoconductive properties of the cement composites. Moreover, the incorporation of platelet lysate induced higher bone healing than the materials without platelet lysate, up to four weeks after surgery. Nevertheless, this effect was not found to be significant when compared to the one observed in the sham-treated group.

Assessment of Bone Regeneration Using Adipose-Derived Stem Cells in Critical-Size Alveolar Ridge Defects: An Experimental Study in a Dog Model.

PURPOSE: To assess bone regeneration potential of a fibronectin- and adipose-derived stem cell-covered ceramic biomaterial in three-wall critical-size alveolar ridge defects. MATERIALS AND METHODS: In 18 dogs, four dehiscence-type and critical-size defects were created surgically in the edentulous alveolar ridge. Defects were randomly regenerated using biomaterials coated with particulate ß-tricalcium phosphate (ß-TCP), ß-TCP with fibronectin (Fn) (ß-TCP-Fn), and ß-TCP with a combination of Fn and autologous adipose-derived stem cells (ADSCs) (ß-TCP-Fn-ADSCs), leaving one defect as control. The animals were divided into three groups according to the time of euthanasia (1, 2, or 3 months of healing). RESULTS: At the time of sacrifice, statistically significant differences between the four types of defects in the total area of bone regeneration, percentage of neoformed bone matrix, medullary space, or contact between particulate biomaterial and neoformed bone matrix were not found. All defects showed a significant increase in neoformed bone matrix as sacrifice was delayed, but a uniform pattern was not followed. Only defects treated with ß-TCP-Fn-ADSCs showed a significant increase in the bone regeneration area when animals sacrificed at 3 months were compared to those sacrificed at 1 month (P = .006). CONCLUSION: The use of ADSCs in bone regeneration processes of critical-size defects of the alveolar ridge did not entail an advantage regarding greater bone regeneration as compared with other biomaterials. However, the use of ß-TCP coated with a combination of Fn and ADSCs appeared to favor stabilization of the regenerated area, allowing a more efficient maintenance of the space at 3 months of healing.

Proceedings of the American Association of Oral and Maxillofacial Surgeons 2015 Research Summit.

The Fifth Biennial Research Summit of the American Association of Oral and Maxillofacial Surgeons and its Committee on Research Planning and Technology Assessment was held in Rosemont, Illinois on May 6 and 7, 2015. The goal of the symposium is to provide a forum for the most recent clinical and scientific advances to be brought to the specialty. The proceedings of the events of that summit are presented in this report.

Impact of surgical innovation on tissue repair in the surgical patient.

BACKGROUND: Throughout history, surgeons have been prolific innovators, which is hardly surprising as most surgeons innovate daily, tailoring their intervention to the intrinsic uniqueness of each operation, each patient and each disease. Innovation can be defined as the application of better solutions that meet new requirements, unarticulated needs or existing market needs. In the past two decades, surgical innovation has significantly improved patient outcomes, complication rates and length of hospital stay. There is one key area that has great potential to change the face of surgical practice and which is still in its infancy: the realm of regenerative medicine and tissue engineering. METHODS: A literature review was performed using PubMed; peer-reviewed publications were screened for relevance in order to identify key surgical innovations influencing regenerative medicine, with a focus on osseous, cutaneous and soft tissue reconstruction. RESULTS: This review describes recent advances in regenerative medicine, documenting key innovations in osseous, cutaneous and soft tissue regeneration that have brought regenerative medicine to the forefront of the surgical imagination. CONCLUSION: Surgical innovation in the emerging field of regenerative medicine has the ability to make a major impact on surgery on a daily basis.

Assessment of bone healing in rabbit calvaria grafted with three different biomaterials.

This study evaluated the bone regeneration process in rabbit calvaria induced by three types of biomaterials: two xenogenous, consisting of deproteinized bovine bone, while the other was alloplastic, based on biphasic calcium phosphate. Five New Zealand white rabbits weighing between 2,900 and 3,500 g were submitted to four standard 8 mm-diameter perforations at the parietal bone. Three perforations were filled with three grafts and biomaterials, two of them received bovine Bio-Oss® and Endobon® Xenograft Granules, and the other consisted of fully alloplastic Straumann® Bone Ceramic. The fourth remaining cavity was used as control with coagulum. After eight weeks, the animals were sacrificed, and the samples were prepared for morphometric and qualitative analysis. The cavities filled with alloplastic biomaterials showed higher percentages of newly formed bone (p<0.05), while the cavities with xenogenous biomaterials showed higher amount of residual graft (p<0.05). Although the results showed greater bone formation with Straumann® Bone Ceramic, further studies are required to prove which is the more effective biomaterial for bone induction process.

Path to the clinic: assessment of iPSC-based cell therapies in vivo in a nonhuman primate model.

Induced pluripotent stem cell (iPSC)-based cell therapies have great potential for regenerative medicine but are also potentially associated with tumorigenic risks. Current rodent models are not optimal predictors of efficiency and safety for clinical application. Therefore, we developed a clinically relevant nonhuman primate model to assess the tumorigenic potential and in vivo efficacy of both undifferentiated and differentiated iPSCs in autologous settings without immunosuppression. Undifferentiated autologous iPSCs indeed form mature teratomas in a dose-dependent manner. However, tumor formation is accompanied by an inflammatory reaction. On the other hand, iPSC-derived mesodermal stromal-like cells form new bone in vivo without any evidence of teratoma formation. We therefore show in a large animal model that closely resembles human physiology that undifferentiated autologous iPSCs form teratomas, and that iPSC-derived progenitor cells can give rise to a functional tissue in vivo.

In vitro and in vivo bioactivity assessment of a polylactic acid/hydroxyapatite composite for bone regeneration.

Synthetic bone graft substitutes based on composites consisting of a polymer and a calcium-phosphate (CaP) ceramic are developed with the aim to satisfy both mechanical and bioactivity requirements for successful bone regeneration. In the present study, we have employed extrusion to produce a composite consisting of 50 wt.% poly(D,L-lactic acid) (PLA) and 50 wt.% nano-sized hydroxyapatite (HA) powder, achieving homogeneous distribution of the ceramic within the polymeric phase. In vitro, in both a simulated physiological saline (SPS) and a simulated body fluid (SBF), a greater weight loss was observed for PLA/HA than for PLA particles upon 12-week immersion. Furthermore, in SPS, a continuous release of calcium and phosphate from the composite was measured, whereas in SBF, decrease of the amount of the two ions in the solution was observed both for PLA and PLA/HA accompanied with the formation of a CaP layer on the surface. In vitro characterization of the composite bioactivity was performed by culturing human mesenchymal stromal cells (hMSCs) and assessing proliferation and osteogenic differentiation, with PLA as a control. Both PLA/HA composite and PLA control were shown to support hMSCs proliferation over a period of two weeks. In addition, the composite significantly enhanced alkaline phosphatase (ALP) activity of hMSCs in osteogenic medium as compared with the polymer control. A novel implant design was employed to develop implants from dense, extruded materials, suitable for testing osteoinductivity in vivo. In a preliminary study in dogs, PLA/HA composite implants induced heterotopic bone formation upon 12-week intramuscular implantation in all animals, in contrast to PLA control, which was not osteoinductive. Unlike in vitro, a more pronounced degradation of PLA was observed in vivo as compared with PLA/HA composite.

Assessment of the regenerative potential of allogeneic periodontal ligament stem cells in a rodent periodontal defect model.

BACKGROUND AND OBJECTIVE: The complex microenvironment of the periodontal wound creates many challenges associated with multitissue regeneration of periodontal lesions. Recent characterization of mesenchymal stem cell-like populations residing in periodontal ligament tissues has shown that these cells exhibit features of postnatal stem cells. Despite these advances, a lack of consistency in design of preclinical studies and a limited study of allogeneic transplantation applications has restricted our understanding of their clinical utility in the treatment of periodontal disease. The aim of this study was to assess the regenerative potential of allogeneic periodontal ligament stem cells (PDLSCs) in a rat periodontal fenestration defect mode and to identify an optimal end time-point suitable for quantitative assessment of tissue regeneration. MATERIAL AND METHODS: Periodontal fenestration defects, created in Sprague Dawley rats, were treated with allogeneic PDLSCs seeded onto Gelfoam(®) (Absorbable gelatin sponge; Pharmacia Corporation, Kalamazoo, MI, USA) or with Gelfoam(®) alone, or remained untreated. Experimental rats were killed at 7, 14, 21 or 28 d after surgery and the tissues were processed for immunohistochemical and histomorphometric examination. RESULTS: Defects treated with PDLSCs showed significantly greater percentage bone fill and length of new bone bridge compared with the untreated group or the group treated with Gelfoam(®) alone on days 14 and 21. Similarly, a statistically significant difference was achieved within specimens retrieved on day 21 for analysis of regeneration of cementum/periodontal ligament (PDL)-like structures. CONCLUSION: The present investigation shows that allogeneic PDLSCs have a marked ability to repair periodontal defects by forming bone, PDL and cementum-like tissue in vivo. The results suggest that treatment periods of 14 and 21 d are optimal end time-points for quantitative assessment of periodontal regeneration within the rodent fenestration-defect model utilized in the present study.