Daniel Chappard

Bio: Daniel Chappard is an academic researcher from French Institute of Health and Medical Research. The author has contributed to research in topics: Osteoporosis & Bone remodeling. The author has an hindex of 56, co-authored 230 publications receiving 9506 citations.

2-Hydroxyethyl Methacrylate (HEMA): Chemical Properties and Applications in Biomedical Fields

Abstract: 2-Hydroxyethyl methacrylate is a monomer with numerous applications. More than 1500 publications have been devoted to this product since 1967,2000 publications or patents mention the corresponding polymer, and a greater number of works involve copolymers incorporating this monomer.

Trabecular Bone Microarchitecture, Bone Mineral Density, and Vertebral Fractures in Male Osteoporosis

Abstract: Some studies have indicated that the risk of fragility fractures in men increases as bone mineral levels decrease, but there is an overlap in the bone mineral density (BMD) measurements between patients with or without fractures. Furthermore, it has been suggested that the biomechanical competence of trabecular bone is dependent not only on the absolute amount of bone present but also on the trabecular microarchitecture. In the present study, 108 men (mean age 52.1 years) with lumbar osteopenia (T score < -2.5) were recruited to examine the relationships between BMD, architectural changes in trabecular bone, and the presence of vertebral fractures. Lumbar BMD was assessed from L2 to L4 in the anteroposterior view with dual-energy X-ray absorptiometry. At the upper left femur, hip BMD was measured at the transcervical site. Spinal X-ray films were analyzed independently by two trained investigators, and vertebral fracture was defined as a reduction of at least 20% in the anterior, middle, or posterior vertebral height. Transiliac bone biopsy specimens were obtained for all patients. Histomorphometric studies were performed on an image analyzer, and the following parameters were determined: trabecular bone volume (BV/TV), trabecular thickness (Tb.Th), number (Tb.N), and separation (Tb.Sp), interconnectivity index (ICI), characterization of the trabecular network (node count and strut analysis), and star volume of the marrow spaces. Spinal radiographs evidenced at least one vertebral crush fracture in 62 patients (group II) and none in 46 patients (group I). After adjusting for age, body mass index, and BMD, there were no significant differences between the two groups in BV/TV, Tb.Th, or star volume. In contrast, the mean values of ICI, free end-to-free end struts (FF/TSL), and Tb.Sp were significantly higher, whereas Tb.N and node-to-node struts (NN/TSL) were lower in patients with at least one vertebral fracture. Logistic regression analysis showed that only ICI, FF/TSL, NN/TSL, and Tb.N were significant predictors of the presence of vertebral fracture: odds ratios for an alteration of 1 SD ranged from 1.7 (1.0-3.2) for NN/TSL to 3.2 (1.1-10.1) for ICI. Patients with at least three vertebral fractures (n = 23) were categorized as "multiple fractures." The results of logistic regression showed that spine BMD, BV/TV, and all architectural parameters were significant predictors of multiple vertebral fractures: odds ratios for an alteration of 1 SD ranged from 2.2 (1.1-4.6) for star volume to 3.7 (1.4-9.7) for ICI. These results strongly suggest that bone trabecular microarchitecture is a major and independent determinant of vertebral fractures in middle-aged men with osteopenia.

Effects of roughness, fibronectin and vitronectin on attachment, spreading, and proliferation of human osteoblast-like cells (Saos-2) on titanium surfaces.

Abstract: The influence of surface roughness and the presence of adhesion molecules in the culture medium were studied regarding cell adhesion, shape, and proliferation of osteoblast-like cells grown on two types of titanium disk. Type I disks were acid etched and type II disks were sandblasted and acid etched. Surface roughness was determined by contact profilometry and scanning electron microscopy. Chemical composition and oxide thickness of the superficial titanium layer were established with energy dispersive X-ray spectrometry, electron spectroscopy for chemical analysis and auger electron spectroscopy. Titanium release in the culture medium was assessed by inductively coupled plasma-optical emission spectrometry. Osteoblast-like cells (Saos-2) were cultured on both types of titanium disks (1) in standard conditions (DMEM culture medium supplemented with fetal calf serum), (FCS), (2) with the culture medium alone (DMEM alone), (3) in the presence of fibronectin or vitronectin (DMEM supplemented with fibronectin or vitronectin). Cultures were also performed in the presence of monoclonal anti-integrin (beta1, alphav) to test the cell adhesion molecules involved in the cell binding to the titanium surface. We found that sandblasting does not modify the chemical surface composition and that titanium represents only 5-6% (in the atom percentage) of surface elements. Release of titanium in the culture medium was found to increase from 24 to 72 hours. In the absence of FCS, fibronectin, or vitronectin, cells appeared scanty and packed in clusters. On the contrary, cells cultured in the presence of FCS, fibronectin, or vitronectin were flattened with large and thin cytoplasmic expansions. The addition of anti beta1 or alphav integrin subunit monoclonal antibody in the culture medium decreased adhesion and spreading of cells, particularly in the presence of fibronectin. Cell proliferation was significantly higher on culture plastic than on both types of disks, but was increased on rough but not on smooth surfaces. These results indicate that a high surface roughness and presence of fibronectin or vitronectin are critical elements for adhesion, spreading, and proliferation of cells on titanium surfaces.

Recruitment of new osteoblasts and osteoclasts is the earliest critical event in the pathogenesis of human multiple myeloma.

Abstract: Considering the special relation of human multiple myeloma (MM) to bones, it is of importance to clarify the early steps of bone involvement in this disease. In this work, using bone histomorphometry (including histoenzymologic and kinetic studies for the first time), we have evaluated the bone remodeling (i.e., bone resorption and bone formation rates) of 16 individuals with early MM in comparison with that of 10 with benign monoclonal gammopathy (BMG) and that of 17 patients with previously untreated overt MM. A significantly increased osteoblastic recruitment was observed in the individuals with early MM when compared with those with BMG (P less than 0.01). A significant (P less than 0.01) increased bone resorption (i.e., eroded surfaces, osteoclast numbers and surfaces) was observed from the early stage of MM in comparison with the BMG status where bone resorption remained within the normal range. At the tissue level, there was no difference in terms of bone resorption between early and overt MM. On the other hand, osteoblast activity was significantly reduced in patients with overt MM (P less than 0.05 by comparison with those with early MM). A significant enhancement of osteoblastic recruitment with an increased generation of new osteoclasts is an early critical event in the pathogenesis of human MM. Of particular importance is the early stimulation of osteoblasts, since these cells produce high amounts of IL-6, a potent myeloma cell growth factor and a critical cytokine for the formation of osteoclasts in the bone marrow.

Mechanisms of bone destruction in multiple myeloma: the importance of an unbalanced process in determining the severity of lytic bone disease.

Abstract: In order to clarify the mechanisms involved in the occurrence of lytic bone lesions (BL) in multiple myeloma (MM), we have compared the presenting myeloma-induced histological bone changes of 14 previously untreated MM patients with lytic BL with those of seven MM patients lacking lytic BL at presentation despite similar myeloma cell mass. A major unbalanced bone remodeling (increased bone resorption with normal to low bone formation) was the characteristic feature of patients presenting lytic BL. Furthermore, this unbalanced process was associated with a significant reduction of bone mass. Unexpectedly, a balanced bone remodeling (increase of both bone resorption and bone formation, without bone mass reduction) rather than a true lack of an excessive bone resorption was the usual feature of patients lacking lytic BL. Our current work clearly shows that a majority (72%) of patients with MM present an important unbalanced bone remodeling at diagnosis, leading to bone mass reduction and bone destruction (un...

Guidelines for assessment of bone microstructure in rodents using micro–computed tomography

Abstract: Use of high-resolution micro-computed tomography (microCT) imaging to assess trabecular and cortical bone morphology has grown immensely. There are several commercially available microCT systems, each with different approaches to image acquisition, evaluation, and reporting of outcomes. This lack of consistency makes it difficult to interpret reported results and to compare findings across different studies. This article addresses this critical need for standardized terminology and consistent reporting of parameters related to image acquisition and analysis, and key outcome assessments, particularly with respect to ex vivo analysis of rodent specimens. Thus the guidelines herein provide recommendations regarding (1) standardized terminology and units, (2) information to be included in describing the methods for a given experiment, and (3) a minimal set of outcome variables that should be reported. Whereas the specific research objective will determine the experimental design, these guidelines are intended to ensure accurate and consistent reporting of microCT-derived bone morphometry and density measurements. In particular, the methods section for papers that present microCT-based outcomes must include details of the following scan aspects: (1) image acquisition, including the scanning medium, X-ray tube potential, and voxel size, as well as clear descriptions of the size and location of the volume of interest and the method used to delineate trabecular and cortical bone regions, and (2) image processing, including the algorithms used for image filtration and the approach used for image segmentation. Morphometric analyses should be based on 3D algorithms that do not rely on assumptions about the underlying structure whenever possible. When reporting microCT results, the minimal set of variables that should be used to describe trabecular bone morphometry includes bone volume fraction and trabecular number, thickness, and separation. The minimal set of variables that should be used to describe cortical bone morphometry includes total cross-sectional area, cortical bone area, cortical bone area fraction, and cortical thickness. Other variables also may be appropriate depending on the research question and technical quality of the scan. Standard nomenclature, outlined in this article, should be followed for reporting of results.

Surface modification of titanium, titanium alloys, and related materials for biomedical applications

Abstract: Titanium and titanium alloys are widely used in biomedical devices and components, especially as hard tissue replacements as well as in cardiac and cardiovascular applications, because of their desirable properties, such as relatively low modulus, good fatigue strength, formability, machinability, corrosion resistance, and biocompatibility. However, titanium and its alloys cannot meet all of the clinical requirements. Therefore, in order to improve the biological, chemical, and mechanical properties, surface modification is often performed. This article reviews the various surface modification technologies pertaining to titanium and titanium alloys including mechanical treatment, thermal spraying, sol–gel, chemical and electrochemical treatment, and ion implantation from the perspective of biomedical engineering. Recent work has shown that the wear resistance, corrosion resistance, and biological properties of titanium and titanium alloys can be improved selectively using the appropriate surface treatment techniques while the desirable bulk attributes of the materials are retained. The proper surface treatment expands the use of titanium and titanium alloys in the biomedical fields. Some of the recent applications are also discussed in this paper.

Mechanisms of bone metastasis.

Abstract: Extract: Cancer frequently spreads to bone, a process termed bone metastasis. Up to 70% of patients with breast cancer or prostate cancer, and 15 to 30% of patients with lung, colon, bladder or kidney cancer develop bone metastasis. Once tumors go to bone, such as in patients with breast cancer or prostate cancer, they are incurable, and only 20% of patients with breast cancer are still alive five years after they are found to have bone metastasis. It is estimated that about 350,000 people die with bone metastasis each year in the United States. Bone metastasis causes severe bone pain and can result in fractures without any injury, as well as other life-threatening conditions. There are two major types of bone metastasis, one in which bone destruction is the predominant feature and the other one in which new bone formation is predominant. Bone metastasis where bone destruction is the predominant feature is known as osteolytic, and that in which new bone formation is the primary feature is called osteoblastic. This classification for metastasis is really two extremes of a continuum because many patients can have both osteolytic and osteoblastic or mixtures of both in their bone metastasis. In fact, patients with prostate cancer who usually have bone metastasis that shows increased new bone formation also have increased bone destruction in the same lesions.