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Biomedical subjects

G Daculsi

Publications and source records attributed to G Daculsi.

At least 19 recordsLinked to original sources

Engineering cartilage with human nasal chondrocytes and a silanized hydroxypropyl methylcellulose hydrogel.

Tissue engineering strategies, based on developing three-dimensional scaffolds capable of transferring autologous chondrogenic cells, holds promise for the restoration of damaged cartilage. In this study, the authors aimed at determining whether a recently developed silanized hydroxypropyl methylcellulose (Si-HPMC) hydrogel can be a suitable scaffold for human nasal chondrocytes (HNC)-based cartilage engineering. Methyltetrazolium salt assay and cell counting experiments first revealed that Si-HPMC enabled the proliferation of HNC. Cell tracker green staining further demonstrated that HNC were able to form nodular structures in this three-dimensional scaffold. HNC phenotype was then assessed by RT-PCR analysis of type II collagen and aggrecan expression as well as alcian blue staining of extracellular matrix. Our data indicated that Si-HPMC allowed the maintenance and the recovery of a chondrocytic phenotype. The ability of constructs HNC/Si-HPMC to form a cartilaginous tissue in vivo was finally investigated after 3 weeks of implantation in subcutaneous pockets of nude mice. Histological examination of the engineered constructs revealed the formation of a cartilage-like tissue with an extracellular matrix containing glycosaminoglycans and type II collagen. The whole of these results demonstrate that Si-HPMC hydrogel associated to HNC is a convenient approach for cartilage tissue engineering.

Aggrecans↗

Injectable bone substitute to preserve alveolar ridge resorption after tooth extraction: a study in dog.

The aim of the present study was to assess the efficacy of a ready-to-use injectable bone substitute on the prevention of alveolar ridge resorption after tooth extraction. Maxillary and mandibular premolars were extracted from 3 Beagle dogs with preservation of alveolar bone. Thereafter, distal sockets were filled with an injectable bone substitute (IBS), obtained by combining a polymer solution and granules of a biphasic calcium phosphate (BCP) ceramic. As a control, the mesial sockets were left unfilled. After a 3 months healing period, specimens were removed and prepared for histomorphometric evaluation with image analysis. Histomorphometric study allowed to measure the mean and the maximal heights of alveolar crest modifications. Results always showed an alveolar bone resorption in unfilled sockets. Resorption in filled maxillary sites was significantly lower than in control sites. Interestingly, an alveolar ridge augmentation was measured in mandibular filled sockets including 30% of newly-formed bone. It was concluded that an injectable bone substitute composed of a polymeric carrier and calcium phosphate can significantly increase alveolar ridge preservation after tooth extraction.

Alveolar Process↗

Evaluation of an injectable bone substitute (betaTCP/hydroxyapatite/hydroxy-propyl-methyl-cellulose) in severely osteopenic and aged rats.

The use of injectable biomaterials is of interest in osteoporotic patients to locally restore bone mass in sites at risk of fracture. An injectable bone substitute (IBS1 made of betaTCP/hydroxyapatite as a calcium phosphate substitute and hydroxy-propyl-methyl-cellulose as a polymer carrier) was used in a severely osteopenic rat model obtained by combining orchidectomy (ORX) and disuse (paralysis induced by botulinum toxin - BTX). Fifty-six aged male rats were randomized into three groups: 18 were SHAM operated; 38 were ORX and BTX injected in the right hindlimb; they constituted the OP (osteoporotic) group. One month after ORX-BTX surgery, 20 of these OP rats received a IBS1 injection in the right femur (OP-IBS1 rats). Animals were studied at the time of IBS1 injection 1 month post ORX-BTX (M1), 1 month (M2) and 2 months (M3) after IBS1 injection. Bone mass (BV/TV) and microarchitectural parameters were measured by microCT. BV/TV was decreased after ORX-BTX; ORX and BTX had cumulative effects on bone loss (differences maximized on the right femur). BV/TV (combining the volume of both bone and material in OP-IBS1 rats) was elevated at M1 but decreased at M2. Marked bone formation was found onto the biomaterial granules but bone had a woven texture. A marked increase in the number of nonosteoclastic TRAcP+ cells was found in the implanted area. IBS1 induced new bone formation shortly after implantation but both IBS1 and woven bone were resorbed without inducing lamellar bone. Biomaterial trials must be conducted with long-term implantation periods, in aged osteoporotic animals.

Aging↗

[Experimental evaluation of microscan assessment of bone fusion].

PURPOSE OF THE STUDY: Certain confirmation of bone fusion remains difficult to obtain after arthrodesis despite progress in imaging techniques. Microscanning enables both qualitative and quantitative analysis of the bone microarchitecture. The purpose of this study was to evaluate this technique using a cervical arthrodesis with an intersomatic cage on an animal model and to validate results with histological analysis and electron scan microscopy (SEM). MATERIAL AND METHODS: C3-C4 discectomy was performed in 8 goats divided into two groups. In group 1 (3 animals), PEEK cages were inserted without bone graft. In group 2 (5 goats) the same cage was inserted and filled with an autologous iliac graft. The animals were sacrificed at six months. The instrumented levels were analyzed with a microscan. Histological slides were obtained and SEM performed. RESULTS: Nonunion was observed in the three animals with an empty cage (group 1) while only one animal in group 2 presented nonunion. Histology and SEM confirmed the diagnosis established with the microscan which also enabled a 3D analysis of the sample and study of the trabecular architecture of the intersomatic graft. DISCUSSION: The microscan enabled a micrometric analysis of the sample. This is the only technique enabling 3D analysis (slices can be obtained in the three planes for 3D reconstruction) for both qualitative and quantitative assessment. Analysis of the trabecular microstructure constitutes a major progress in evaluating the mechanical value of the fusion. The sample is not destroyed and can be studied further with other biomechanical techniques. CONCLUSION: Microscanning is an important technical advancement for the analysis of bone fusion. Future applications will undoubtedly be numerous (follow-up after arthrodesis, analysis of the mechanical quality of a graft). In vivo applications will probably be adapted soon.

Animals↗

Cartilage and bone tissue engineering using hydrogels.

Tissue engineering is an emerging field of regenerative medicine which holds promise for the restoration of tissues and organs affected by chronic diseases, age-linked degeneration, congenital deformity and trauma. During the past decade, tissue engineering has evolved from the use of naked biomaterials, which may just replace small area of damaged tissue, to the use of controlled three-dimensional scaffolds in which cells can be seeded before implantation. These cellularized constructs aims at being functionally equal to the unaffected tissue and could make possible the regeneration of large tissue defects. Among the recently developed scaffolds for tissue engineering, polymeric hydrogels have proven satisfactory in cartilage and bone repair. Major technological progress and advances in basic knowledge (physiology and developmental biology) are today necessary to bring this proof of concept to clinical reality. The present review focuses on the recent advances in hydrogel-based tissue engineered constructs potentially utilizable in bone and cartilage regenerative medicine.

Animals↗

Small-animal models for testing macroporous ceramic bone substitutes.

The aim of this study was to compare the bone colonization of a macroporous biphasic calcium phosphate (MBCP) ceramic in different sites (femur, tibia, and calvaria) in two animal species (rats and rabbits). A critical size defect model was used in all cases with implantation for 21 days. Bone colonization in the empty and MBCP-filled defects was measured with the use of backscattered electron microscopy (BSEM). In the empty cavities, bone healing remained on the edges, and did not bridge the critical size defects. Bone growth was observed in all the implantation sites in rats (approximately 13.6-36.6% of the total defect area, with ceramic ranging from 46.1 to 51.9%). The bone colonization appeared statistically higher in the femur of rabbits (48.5%) than in the tibia (12.6%) and calvaria (22.9%) sites. This slightly higher degree of bone healing was related to differences in the bone architecture of the implantation sites. Concerning the comparison between animal species, bone colonization appeared greater in rabbits than in rats for the femoral site (48.5% vs. 29.6%). For the other two sites (the tibia and calvaria), there was no statistically significant difference. The increased bone ingrowth observed in rabbit femurs might be due to the large bone surface area in contact with the MBCP ceramics. The femoral epiphysis of rabbits is therefore a favorable model for testing the bone-bonding capacity of materials, but a comparison with other implantation sites is subject to bias. This study shows that well-conducted and fully validated models with the use of small animals are essential in the development of new bone substitutes.

Animals↗

A comparative study of biphasic calcium phosphate ceramics for human mesenchymal stem-cell-induced bone formation.

For the repair of bone defects, a tissue engineering approach would be to combine cells capable of osteogenic (i.e. bone-forming) activity with an appropriate scaffolding material to stimulate bone regeneration and repair. Human mesenchymal stem cells (hMSCs), when combined with hydroxyapatite/beta-tricalcium phosphate (HA/TCP) ceramic scaffolds of the composition 60% HA/40% TCP (in weight %), have been shown to induce bone formation in large, long bone defects. However, full repair or function of the long bone could be limited due to the poor remodeling of the HA/TCP material. We conducted a study designed to determine the optimum ratio of HA to TCP that promoted hMSC induced bone formation yet be fully degradable. In a mouse ectopic model, by altering the composition of HA/TCP to 20% HA/80% TCP, hMSC bone induction occurred at the fastest rate in vivo over the other formulations of the more stable 100% HA, HA/TCP (76/24, 63/37, 56/44), and the fully degradable, 100% TCP. In vitro studies also demonstrated that 20/80 HA/TCP stimulated the osteogenic differentiation of hMSCs as determined by the expression of osteocalcin.

Animals↗

A silanized hydroxypropyl methylcellulose hydrogel for the three-dimensional culture of chondrocytes.

Articular cartilage has limited intrinsic repair capacity. In order to promote cartilage repair, the amplification and transfer of autologous chondrocytes using three-dimensional scaffolds have been proposed. We have developed an injectable and self-setting hydrogel consisting of hydroxypropyl methylcellulose grafted with silanol groups (Si-HPMC). The aim of the present work is to assess both the in vitro cytocompatibility of this hydrogel and its ability to maintain a chondrocyte-specific phenotype. Primary chondrocytes isolated from rabbit articular cartilage (RAC) and two human chondrocytic cell lines (SW1353 and C28/I2) were cultured into the hydrogel. Methyl tetrazolium salt (MTS) assay and cell counting indicated that Si-HPMC hydrogel did not affect respectively chondrocyte viability and proliferation. Fluorescent microscopic observations of RAC and C28/I2 chondrocytes double-labeled with cell tracker green and ethidium homodimer-1 revealed that chondrocytes proliferated within Si-HPMC. Phenotypic analysis (RT-PCR and Alcian blue staining) indicates that chondrocytes, when three-dimensionnally cultured within Si-HPMC, expressed transcripts encoding type II collagen and aggrecan and produced sulfated glycosaminoglycans. These results show that Si-HPMC allows the growth of differentiated chondrocytes. Si-HPMC therefore appears as a potential scaffold for three-dimensional amplification and transfer of chondrocytes in cartilage tissue engineering.

Animals↗

A review of bioceramics and fibrin sealant.

This review focuses on bone substitute composites made by mixing ceramic biomaterials with fibrin sealants. Different biomaterials such as coral, bone-derived materials, bioactive glass ceramics, and synthetic calcium phosphate have been mixed with fibrin sealant, resulting in a combination of the biological properties of the two components. This type of association has not produced identical results in all studies. In the past for some, the addition of fibrin sealant to the biomaterial failed to produce any significant, positive effect on osteointegration, whereas others found a positive impact on bone colonization. Despite the negative biological effects reported previously, bioceramic-fibrin composites have been widely used in various types of bone surgery because they are easy to manipulate. In particular, the intra-operative preparation of these composites makes it possible to add bone growth factors or autologous osteoprogenitor cells prior to bone reconstruction. The bone growth factors and autologous osteoprogenitor cells associated with the bioceramic-fibrin composites should provide surgeons with tissue engineered grafts with enhanced osteointegrative properties. This review discusses both the advantages and disadvantages, as well as the future perspectives, of using bioceramic-fibrin composites in various clinical indications.

Animals↗

Development of an odontoblast in vitro model to study dentin mineralization.

The aim of the present work was to characterize the odontoblastic proliferation, differentiation, and matrix mineralization in culture of the recently established M2H4 rat cell line. Proliferation was assessed by cell counts, differentiation by RT-PCR analysis, and mineralization by alizarin red staining, atomic absorption spectrometry, and FTIR microspectroscopy. The results showed that M2H4 cell behavior closely mimics in vivo odontoblast differentiation, with, in particular, temporally regulated expression of DMP-1 and DSPP. Moreover, the mineral phase formed by M2H4 cells was similar to that in dentin from rat incisors. Finally, because in mice, transforming growth factor (TGF)-beta1 over-expression in vivo leads to an hypomineralization similar to that observed in dentinogenesis imperfecta type II, effects of TGF-beta1 on mineralization in M2H4 cell culture were studied. Treatment with TGF-beta1 dramatically reduced mineralization, whereas positive control treatment with bone morphogenetic protein-4 enhanced it, suggesting that M2H4 cell line is a promising tool to explore the mineralization mechanisms in physiopathologic conditions.

Animals↗

Noninvasive bone replacement with a new injectable calcium phosphate biomaterial.

The use of injectable calcium phosphate (CaP) biomaterials in noninvasive surgery should provide efficient bone colonization and implantation. Two different kinds of injectable biomaterials are presently under development: ionic hydraulic bone cements that harden in vivo after injection, and an association of biphasic calcium phosphate (BCP) ceramic granules and a water-soluble polymer vehicle (a technique particularly investigated by our group), providing an injectable CaP bone substitute (IBS). In our study, we compared these two approaches, using physicochemical characterizations and in vivo evaluations in light microscopy, scanning electron microscopy, and three-dimensional microtomography with synchrotron technology. Three weeks after implantation in rabbit bone, both biomaterials showed perfect biocompatibility and bioactivity, but new bone formation and degradation of the biomaterial were significantly greater for BCP granules than for ionic cement. Newly formed bone developed, binding the BCP granules together, whereas new bone grew only on the surface of the cement, which remained dense, with no obvious degradation 3 weeks after implantation. This study confirms that BCP granules carried by a cellulosic polymer conserve bioactivity and are conducive to earlier and more extensive bone substitution than a carbonated-hydroxyapatite bone cement. The presence of intergranular spaces in the BCP preparation, as shown on microtomography imaging, seems particularly favorable, allowing body fluids to reach each BCP granule immediately after implantation. Thus, the IBS functions as a completely interconnected ceramic with total open macroporosity. This new bone replacement approach should facilitate microinvasive bone surgery and local delivery of bone therapy agents.

Animals↗

Calcium-deficient apatite: a first in vivo study concerning bone ingrowth.

Biphasic calcium phosphate (BCP) materials are increasingly used to restore bone loss in surgery. Calcium-deficient apatites (CDA), the precursors of BCP, are closer in structure to biological apatites and can be associated with therapeutic agents to form drug-delivery systems. The purpose of this first in vivo study of CDA was to evaluate the osteoconductive properties of two composites, consisting of 40-80 microm granules carried by a cellulose-derived polymer, used to fill critical size bone defects in rabbit femoral ends. Animals were sacrificed 2 or 3 weeks after implantation. Histomorphometric analysis of scanning electron microscopy implant surface files was performed using gray level threshold that distinguish between bone or materials (white) and noncalcified tissue (black). Quantitative results for new bone formation showed no significant differences between the composites or the implantation periods. However, nearly all of the CDA disappeared early while supporting more extensive bone colonization than biphasic calcium phosphates implanted in the same conditions.

Animals↗

Compactibility study of calcium phosphate biomaterials.

This study investigated the micromechanism responsible for the densification and consolidation of powders during dynamic compaction, an experimental process in which ceramic is formed without heating. Three calcium-deficient apatites (CDA: two powders and a fibrous compound) and a biphasic calcium phosphate (BCP) were studied to determine their aptitude (rheological and physical properties) for compactibility under various dynamic compaction pressures. Powders were investigated for their physicochemistry, particle size, and flow time, and compacts for their compaction rate, density, specific area, mechanical characteristics, and disintegration time. Powder particles showed different morphological features depending on the synthesis protocol used, specific area and rheological behaviour. Compacts were not obtained with BCP, regardless of the gas pressure used, whereas CDA produced compacts with good mechanical properties (high hardness and compression stress), particularly for the fibrous compound. The poor compressibility and compactibility of BCP powders were confirmed, whereas fibrous CDA powders showed good compactibility conducive to high-quality filling of biomaterials.

Biocompatible Materials↗

Vancomycin encapsulation in biodegradable poly(epsilon-caprolactone) microparticles for bone implantation. Influence of the formulation process on size, drug loading, in vitro release and cytocompatibility.

Vancomycin encapsulation in biodegradable poly(epsilon-caprolactone) microparticles (200 microm mean diameter) was most efficient with a simple emulsion technique that dispersed 122.5 mg/g of polymer. Scanning electron micrographs showed smooth or pitted particles. Dissolution studies were correlated with microparticle morphology, indicating higher release with pitted particles when vancomycin was encapsulated in a dissolved state. The cytocompatibility of these poly(epsilon-caprolactone) microparticles was demonstrated by a direct contact cytotoxic assay. This material can be considered as an efficient drug delivery system for bone implantation.

Absorbable Implants↗

Calcium-deficient apatite: influence of granule size and consolidation mode on release and in vitro activity of vancomycin.

The use of dynamic compaction and isostatic compression to consolidate calcium phosphate powder loaded with a therapeutic agent avoids a sintering step that could destroy the drug. The present study applied these consolidation methods to vancomycin-loaded calcium-deficient apatite powder, using three granulometric fractions (40-80, 80-200 and 200-500 micrometer). In vitro release profiles were determined via an original system derived from low-pressure liquid chromatography. The biological activity of vancomycin was measured by an in vitro standardized bacteriologic assay, which showed that the drug is completely active after association with calcium phosphate. Regardless of the consolidation method and granulometric fraction used, release profiles were not significantly different and therefore adaptable to injectable suspensions.

Anti-Bacterial Agents↗

Synchrotron X-ray microtomography (on a micron scale) provides three-dimensional imaging representation of bone ingrowth in calcium phosphate biomaterials.

This study used synchrotron X-ray microtomography on a micron scale to compare three-dimensional (3D) bone ingrowth after implantation of various calcium phosphate bone substitutes in a rabbit model. The advantage of using this new method for the study of biomaterials was then compared with histomorphometry for analysis of interconnection and bone ingrowth. The study focused on the newly formed bone-biomaterial interface. Macroporous Biphasic Calcium Phosphate (MBCP) ceramic blocks and two different injectable calcium phosphate biomaterials [an injectable bone substitute (IBS) consisting of a biphasic calcium phosphate granule suspension in hydrosoluble polymer and a calcium phosphate cement material (CPC)] were studied after in vivo implantation. Absorption or phase-contrast microtomography was performed with the dedicated set-up at beamline ID22. Experimental spatial resolution was between 1 and 1.4 microm, depending on experimental radiation. All calcium phosphates tested showed osteoconduction. IBS observations after 3D reconstruction showed interconnected bioactive biomaterial with total open macroporosity and complete bone ingrowth as early as 3 weeks after implantation. This experimentation was consistent with two-dimensional histomorphometric analysis, which confirmed its suitability for biomaterials. This 3D study relates the different types of bone substitution to biomaterial architecture. As porosity and interconnection increase, bone ingrowth becomes greater at the expense of the bone substitute: IBS>MBCP>CPC.

Animals↗

Modification of gene expression induced in human osteogenic and osteosarcoma cells by culture on a biphasic calcium phosphate bone substitute.

Bone hybrids made of bioceramics seeded with mesenchymal or osteoblastic cells are very promising alternatives to autologous bone graft. Along this line, the development of in vitro models, dedicated to analyze the influence of these biomaterials on osteogenic cells, will help to improve the performance of these bone substitutes. In the present work we analyzed the effects of a macroporous biphasic calcium phosphate ceramic (BCP, Triosite) on three different human osteosarcoma cell lines and on human primary osteogenic cells and compared this culture substratum to traditional culture on plastic. We showed that all these osteoblastic cells adhere and proliferate on the trabecular BCP blocks, with a different spatial organization for osteosarcoma cells compared to normal osteogenic cells. We also demonstrated that osteoblastic marker genes such as Cbfa1, type I collagen, osteonectin, osteopontin, and osteocalcin were expressed at similar levels by these cells cultured on either substratum, suggesting that adhesion to BCP does maintain the osteoblastic phenotype of these cells. Next, we provided the first evidence of differences of cytokine expression profiles revealed on this Ca-P ceramic as compared to expression in classical culture. These modifications affected the expression of cytokines such as TGF-beta1, G-CSF, and IL-3 and were quantitatively different between osteosarcoma cells and normal osteogenic cells. Given the role of these cytokines in bone biology and in hematopoiesis, these results obtained in vitro suggest that the BCP ceramic studied here could stimulate osteogenesis in vivo by activating cellular processes during bone formation and healing. This study highlights the notion that the nature of the culture substratum must be taken into account when studying bone cell biology in vitro. Owing to the nature and spatial organization of the BCP, our hypothesis is that culture on BCP is closer to the physiological situation than culture on plastic.

Adolescent↗

Micro macroporous biphasic ceramics and fibrin sealant as a moldable material for bone reconstruction in chronic otitis media surgery. A 15 years experience.

Bone reconstruction is still a matter of concern in middle ear surgery despite the large number of surgical techniques proposed. Combination of biphasic calcium phosphate bioceramics with human fibrin sealant forms a moldable material easy to apply for bone reconstruction. Since 1986, we have been using this composite for reconstruction of mastoid cavities during chronic otitis media surgery. Granules of ceramic provide immediate mechanical stability and later on, promote osseoinduction when fibrin sealant forms a strong bond between granules enhancing the wound healing process. After checking feasibility, efficacy and tolerance through a controlled study on dogs by filling mastoid cavities, we started a clinical series comprising yet 66 mastoid reconstructions. A retrospective data analysis on 63 patients with an average follow up of 42 months including 12 histological controls confirms the stability of bone reconstruction with a remarkable tolerance of the skin in contact. Biopsies confirmed progressive replacement of material by lamellar newly formed bone. Mastoid cavities have a randomed shape making complex bone reconstruction procedure and their filling by the composite constitutes an easy way and represents a highly satisfactory procedure. The authors considered that this should be explored in other indications of bone surgery.

Journal Article↗