Rigid internal fixation with titanium versus bioresorbable miniplates in the repair of mandibular fractures in rabbits

The purpose of this study was to compare by qualitative histology the efficacy of rigid internal fixation with titanium system and the Lacto Sorb® system in mandibular fractures in rabbits. Thirty male adult rabbits Oryctolagus cuniculus were used. Unilateral mandibular osteotomies were performed between the canine and first premolar. The animals were divided into two groups: for Group I - rigid internal fixation was performed with titanium system 1.5 mm (Synthes, Oberdorf, Switzerland), with two screws of 6 mm (bicortical) on each side of the osteotomy. For Group II-rigid internal fixation was performed with PLLA/PGA system 1.5 mm (Lacto Sorb®, WLorenz, Jacksonville, FL, USA). The histological analysis evaluated the presence of inflammatory reaction, degree of bone healing and degree of resorption of the Lacto Sorb® screws. The results of both fixation systems were similar, only with a small difference after 15 and 30 days. In Group I a faster bony healing was noted. But after 60 days, bony healing was similar in both groups. It is concluded that both PLLA/PGA and titanium plates and screws provide sufficient strength to permit mandibular bone healing. The resorption process of PLLA/PGA osteosynthesis material did not cause acute or chronic inflammatory reaction or foreign body reaction during the studied period. © 2004 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Thermoanalytical study of praziquantel-loaded PLGA nanoparticles

Polymeric nanoparticles have received great attention as potential controlled drug delivery systems. Biodegradable polymers has been extensively used in the development of these drug carriers, and the polyesters such as polylactic acid, polyglycolic acid and their copolymers as poly-lactide-co- glycolide are the most used, considering its biocompatibility and biodegradability. Thermal analysis techniques have been used for pharmaceutical substances for more than 30 years and are routine methods for screening drug-excipient interactions. The aim of this work is to use thermal analysis to characterize PLGA nanoparticles containing a hydrophobic drug, praziquantel. The results show that the drug is in an amorphous state or in disordered crystalline phase of molecular dispersion in the PLGA polymeric matrix and that the microencapsulation process did not interfere with the chemical structure of the polymer, mantaining the structural drug integrity.

Avaliação do copolímero de ácido polilático e poliglicólico associado ao vidro bioativo no processo de regeneração óssea: análise histomorfométrica e imunoistoquímica em ratos

Pós-graduação em Odontologia - FOA

Cultura de condrócitos para o uso terapêutico: reconstituição de cartilagem

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Avaliação da interface osso/implante após o uso do copolímero de PLA/PGA associado a osso autógeno em coelhos: estudo biomecânico e imunohistoquímico

Pós-graduação em Odontologia - FOA

O efeito da BMP-2 sobre as propriedades osteocondutoras do beta-tricálcio fosfato em defeitos de calvária de ratos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Uso do copolímero de PLA/PGA no processo de reparo de defeitos ósseos em tíbia de coelhos: análise histomorfométrica

Pós-graduação em Odontologia - FOA

Comparison of the capacity of enamel matrix derivative gel and enamel matrix derivative in liquid formulation to adsorb to bone grafting materials.

BACKGROUND The use of an enamel matrix derivative (EMD) has been shown to enhance periodontal regeneration (e.g., formation of root cementum, periodontal ligament, and alveolar bone). However, in certain clinical situations, the use of EMD alone may not be sufficient to prevent flap collapse or provide sufficient stability of the blood clot. Data from clinical and preclinical studies have demonstrated controversial results after application of EMD combined with different types of bone grafting materials in periodontal regenerative procedures. The aim of the present study is to investigate the adsorption properties of enamel matrix proteins to bone grafts after surface coating with either EMD (as a liquid formulation) or EMD (as a gel formulation). METHODS Three different types of grafting materials, including a natural bone mineral (NBM), demineralized freeze-dried bone allograft (DFDBA), or a calcium phosphate (CaP), were coated with either EMD liquid or EMD gel. Samples were analyzed by scanning electron microscopy or transmission electron microscopy (TEM) using an immunostaining assay with gold-conjugated anti-EMD antibody. Total protein adsorption to bone grafting material was quantified using an enzyme-linked immunosorbent assay (ELISA) kit for amelogenin. RESULTS The adsorption of amelogenin to the surface of grafting material varied substantially based on the carrier system used. EMD gel adsorbed less protein to the surface of grafting particles, which easily dissociated from the graft surface after phosphate-buffered saline rinsing. Analyses by TEM revealed that adsorption of amelogenin proteins were significantly farther from the grafting material surface, likely a result of the thick polyglycolic acid gel carrier. ELISA protein quantification assay demonstrated that the combination of EMD liquid + NBM and EMD liquid + DFDBA adsorbed higher amounts of amelogenin than all other treatment modalities. Furthermore, amelogenin proteins delivered by EMD liquid were able to penetrate the porous surface structure of NBM and DFDBA and adsorb to the interior of bone grafting particles. Grafting materials coated with EMD gel adsorbed more frequently to the exterior of grafting particles with little interior penetration. CONCLUSIONS The present study demonstrates a large variability of adsorbed amelogenin to the surface of bone grafting materials when enamel matrix proteins were delivered in either a liquid formulation or gel carrier. Furthermore, differences in amelogenin adsorption were observed among NBM, DFDBA, and biphasic CaP particles. Thus, the potential for a liquid carrier system for EMD, used to coat EMD, may be advantageous for better surface coating.

Tissue engineering of cartilage in space

Tissue engineering of cartilage, i.e., the in vitro cultivation of cartilage cells on synthetic polymer scaffolds, was studied on the Mir Space Station and on Earth. Specifically, three-dimensional cell-polymer constructs consisting of bovine articular chondrocytes and polyglycolic acid scaffolds were grown in rotating bioreactors, first for 3 months on Earth and then for an additional 4 months on either Mir (10−4–10−6 g) or Earth (1 g). This mission provided a unique opportunity to study the feasibility of long-term cell culture flight experiments and to assess the effects of spaceflight on the growth and function of a model musculoskeletal tissue. Both environments yielded cartilaginous constructs, each weighing between 0.3 and 0.4 g and consisting of viable, differentiated cells that synthesized proteoglycan and type II collagen. Compared with the Earth group, Mir-grown constructs were more spherical, smaller, and mechanically inferior. The same bioreactor system can be used for a variety of controlled microgravity studies of cartilage and other tissues. These results may have implications for human spaceflight, e.g., a Mars mission, and clinical medicine, e.g., improved understanding of the effects of pseudo-weightlessness in prolonged immobilization, hydrotherapy, and intrauterine development.

Tissue-engineered cells producing complex recombinant proteins inhibit ovarian cancer in vivo

Techniques of tissue engineering and cell and molecular biology were used to create a biodegradable scaffold for transfected cells to produce complex proteins. Mullerian Inhibiting Substance (MIS) causes regression of Mullerian ducts in the mammalian embryo. MIS also causes regression in vitro of ovarian tumor cell lines and primary cells from ovarian carcinomas, which derive from Mullerian structures. In a strategy to circumvent the complicated purification protocols for MIS, Chinese hamster ovary cells transfected with the human MIS gene were seeded onto biodegradable polymers of polyglycolic acid fibers and secretion of MIS confirmed. The polymer-cell graft was implanted into the right ovarian pedicle of severe combined immunodeficient mice. Serum MIS in the mice rose to supraphysiologic levels over time. One week after implantation of the polymer-cell graft, IGROV-1 human tumors were implanted under the renal capsule of the left kidney. Growth of the IGROV-1 tumors was significantly inhibited in the animals with a polymer-cell graft of MIS-producing cells, compared with controls. This novel MIS delivery system could have broader applications for other inhibitory agents not amenable to efficient purification and provides in vivo evidence for a role of MIS in the treatment of ovarian cancer.

Dog peritoneal and pleural cavities as bioreactors to grow autologous vascular grafts

Objective: The purpose of this study was to grow artificial blood vessels for autologous transplantation as arterial interposition grafts in a large animal model (dog). Method and results: Tubing up to 250 mm long, either bare or wrapped in biodegradable polyglycolic acid (Dexon) or nonbiodegradable polypropylene (Prolene) mesh, was inserted in the peritoneal or pleural cavity of dogs, using minimally invasive techniques, and tethered at one end to the wall with a loose suture. After 3 weeks the tubes and their tissue capsules were harvested, and the inert tubing was discarded. The wall of living tissue was uniformly 1-1.5 mm thick throughout its length, and consisted of multiple layers of myofibroblasts and matrix overlaid with a single layer of mesothelium. The myofibroblasts stained for a-smooth muscle actin, vimentin, and desmin. The bursting strength of tissue tubes with no biodegradable mesh scaffolds was in excess of 2500 mm Hg, and the suture holding strength was 11.5 N, both similar to that in dog carotid and femoral arteries. Eleven tissue tubes were transplanted as interposition grafts into the femoral artery of the same dog in which they were grown, and were harvested after 3 to 6.5 months. Eight remained patent during this time. At harvest, their lumens were lined with endothelium-like cells, and wall cells stained for alpha-actin, smooth muscle myosin, desmin and smoothelin; there was also a thick adventitia containing vasa vasorum. Conclusion: Peritoneal and pleural cavities of large animals can function as bioreactors to grow myofibroblast tubes for use as autologous vascular grafts.

Establishment of metanephros transplantation in mice highlights contributions by both nephrectomy and pregnancy to developmental progression

Background: It has been demonstrated that embryonic kidneys (metanephroi) xenotransplanted into the omentum of adult recipients continue to develop and display immune protection due to their more nave immune presentation. To date, this has been achieved using rat, pig and human metanephroi, with unilateral nephrectomy (UNX) of recipient rats a requisite of renal development. The aim of this study was to adapt this approach for use in mice and examine the parameters affecting successful onward development in this species. Methods: Metanephroi at embryonic age (E) 13.5 were transplanted either onto the body wall, abdominal fat pads or omentum of recipient isogenic C57/Bl6 mice using either sutures or polyglycolic acid mesh. Having established greatest success with polyglycolic acid mesh on the body wall, E12.5 and 15.5 days metanephroi from C57/Bl6 mice were then transplanted onto the body wall of control (non-pregnant non-UNX), UNX or 12.5 days post-coitum pregnant isogenic recipients. After 7 days, implanted tissue was harvested and examined using histology and immunohistochemistry for markers of renal maturation. The mean number of S-shaped bodies and glomeruli per section were recorded and statistically analysed for significant differences between all recipient groups and untransplanted metanephroi. The degree of development was scored qualitatively. Results: Transplanted E12.5 metanephroi developed S-shaped bodies and glomeruli in all recipient groups, although there were statistically higher numbers of S-shaped bodies in UNX (n = 2) and pregnant recipients (n = 9) than in control recipients (n = 4). Continued development, as indicated by mature vascularized glomeruli, was only observed in those E15.5 metanephroi transplanted into pregnant recipients (n = 11) with a 15.5-fold increase in S-shaped bodies and 4-fold increase in glomeruli compared with control transplants (n = 12). Conclusions: We have successfully established metanephros transplantation in mice and demonstrated enhancement of onward development of E12.5 metanephroi in response to both pregnancy and UNX. Using E15.5 metanephroi, continued development only occurred in pregnant recipients, implying pregnancy provides an environment conducive to continued organogenesis. This murine assay, when coupled with transgenically-tagged strains of mice, will allow the investigation of the relative contribution of donor and recipient cells to this process. Copyright (C) 2005 S. Karger AG, Basel.

Characterization of engineered human lung tissue

Characterizing engineered human lung tissue is an important step in developing a functional tissue replacement for lung tissue repair and in vitro analysis. Small tissue constructs were grown by seeding IMR-90 fetal lung fibroblasts and adult microvascular endothelial cells onto a Polyglycolic acid (PGA) polymer template. Introducing the constructs to dynamic culture conditions inside a bioreactor facilitated three-dimensional growth seen in scanning electron microscopy images (SEM). Characterization of the resultant tissue samples was done using SEM imagery, tensile tests, and biochemical assays to quantify extra-cellular matrix (ECM) composition. Tensile tests of the engineered samples indicated an increase in the mechanical properties when compared with blank constructs. Elastin and collagen content was found to average 3.19% and 15.49% respectively in relation to total mass of the tissue samples. The presence of elastin and collagen within the constructs most likely explains the mechanical differences that we noted. These findings suggest that the necessary ECM can be established in engineered tissue constructs and that optimization of this procedure has the capacity to generate the load bearing elements required for construction of a functional lung tissue equivalent.

Chitosan fibrous scaffolds for cartilage tissue engineering

The biocompatibility of chitosan and its similarity with glycosaminoglycans make it attractive for cartilage engineering despite its limited cell adhesion properties. Structural and chemical characteristics of chitosan scaffolds may be improved for cartilage engineering application. We planned to evaluate chitosan meshes produced by a novel technique and the effect of chitosan structure on mesenchymal stem cells (MSCs) chondrogenesis. Another objective was to improve cell adhesion and chondrogenesis on chitosan by modifying the chemical composition of the scaffold (reacetylation, collagen II, or hyaluronic acid (HA) coating). A replica molding technique was developed to produce chitosan meshes of different fiber-width. A polyglycolic acid (PGA) mesh served as a reference. Constructs were analyzed at two and 21 days after seeding chondrocytes with confocal microscopy, scanning electron microscopy, histology, and quantitative analysis (weights, DNA, glycosaminoglycans, collagen II). Chondrocytes maintained their phenotypic appearance and a high viability but attached preferentially to PGA. Matrix production per chondrocyte was superior on chitosan. Chitosan meshes and sponges were analyzed after seeding and culture of MSCs under chondrogenic condition for 21 days. The cellularity was similar between groups but matrix production was greater on meshes. Chitosan and reacetylated-chitosan scaffolds were coated with collagen II or HA. Scaffolds were characterized prior to seeding MSCs. Chitosan meshes were then coated with collagen at two densities. PGA served as a reference. Constructs were evaluated after seeding or culture of MSCs for 21 days in chondrogenic medium. MSCs adhered less to reacetylated-chitosan despite collagen coating. HA did not affect cell adhesion. The cell attachment on chitosan correlated with collagen density. The cell number and matrix production were improved after culture in collagen coated meshes. The differences between PGA and chitosan are likely to result from the chemical composition. Chondrogenesis is superior on chitosan meshes compared to sponges. Collagen II coating is an efficient way to overcome poor cell adhesion on chitosan. These findings encourage the use of chitosan meshes coated with collagen II and confirm the importance of biomimetic scaffolds for tissue engineering. The decreased cell adhesion on reacetylated chitosan and the poor mechanical stability of PGA limit their use for tissue engineering.

The Crosslinking Degree Controls The Mechanical, Rheological, And Swelling Properties Of Hyaluronic Acid Microparticles.

Viscosupplements, used for treating joint and cartilage diseases, restore the rheological properties of synovial fluid, regulate joint homeostasis and act as scaffolds for cell growth and tissue regeneration. Most viscosupplements are hydrogels composed of hyaluronic acid (HA) microparticles suspended in fluid HA. These microparticles are crosslinked with chemicals to assure their stability against enzyme degradation and to prolong the action of the viscosupplement. However, the crosslinking also modifies the mechanical, swelling and rheological properties of the HA microparticle hydrogels, with consequences on the effectiveness of the application. The aim of this study is to correlate the crosslinking degree (CD) with these properties to achieve modulation of HA/DVS microparticles through CD control. Because divinyl sulfone (DVS) is the usual crosslinker of HA in viscosupplements, we examined the effects of CD by preparing HA microparticles at 1:1, 2:1, 3:1, and 5:1 HA/DVS mass ratios. The CD was calculated from inductively coupled plasma spectrometry data. HA microparticles were previously sized to a mean diameter of 87.5 µm. Higher CD increased the viscoelasticity and the extrusion force and reduced the swelling of the HA microparticle hydrogels, which also showed Newtonian pseudoplastic behavior and were classified as covalent weak. The hydrogels were not cytotoxic to fibroblasts according to an MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2014.