Publications by authors named "Guillaume Falgayrac"

Article Synopsis
  • Osteoarthritis (OA) is a joint disease characterized by calcification in cartilage, and this study seeks to understand the mechanisms behind this process to help develop new treatments.
  • Researchers stimulated chondrocytes with calciprotein particles to analyze changes in gene expression, identifying 1466 modulated genes and confirming 27 of them as relevant to OA from existing human data.
  • Key findings revealed two gene families influenced by calciprotein particles, including cytoskeletal and extracellular matrix genes, which could provide new therapeutic targets for treating OA.
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This study aimed to evaluate the correlation between BMAT and bone quality, describe the long-term effects of ovariectomy on bone, and investigate BMAT's spatial distribution. Fifteen-months-old female Sprague‒Dawley rats were studied, comparing ovariectomized (OVX, n = 22) and sham-operated (SHAM, n = 11) groups at 6 months. Tibias were analyzed for bone microarchitecture, BMAT (microcomputed tomography), mineral parameters (quantitative backscattered electron imaging), and bone composition (Raman microspectroscopy).

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Objective: Cartilage pathologic calcification is a hallmark of osteoarthritis (OA). Here, we aimed to describe a new ex vivo human model to study the progression of cartilage calcification.

Method: Cartilage explants (n = 11), as well as primary chondrocytes (n = 3), were obtained from OA patients undergoing knee replacement.

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Bone marrow adipocytes (BMAds) constitute the most abundant stromal component of adult human bone marrow. Two subtypes of BMAds have been described, the more labile regulated adipocytes (rBMAds) and the more stable constitutive adipocytes (cBMAds), which develop earlier in life and are more resilient to environmental and metabolic disruptions. , rBMAds are enriched in saturated fatty acids, contain smaller lipid droplets (LDs) and more readily provide hematopoietic support than their cBMAd counterparts.

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After death, diagenesis takes place. Numerous processes occur concomitantly, which makes it difficult to identify the diagenetic processes. The diagenetic processes refer to all processes (chemical or physical) that modify the skeletal remains.

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Article Synopsis
  • The study compared the mechanical and intrinsic properties of cortical (Ct) and trabecular (Tb) bone in iliac biopsies from untreated postmenopausal osteoporotic women to better understand their contributions to overall bone strength.* -
  • It was found that the indentation modulus (elasticity) and dissipated energy were higher in Ct bone compared to Tb, while hardness showed no significant difference; mineral and collagen maturity were also greater in Ct than in Tb.* -
  • Overall, while Ct and Tb bones exhibited distinct mechanical properties, the differences within the bone tissue types (osteonal vs. interstitial) were more pronounced than those between the two bone compartments.*
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Bone marrow adipocytes (BMAds) accrue in various states of osteoporosis and interfere with bone remodeling through the secretion of various factors. However, involvement of the extracellular matrix (ECM) produced by BMAds in the impairment of bone marrow mesenchymal stromal cell (BM-MSC) osteoblastogenesis has received little attention. In type 2 diabetes (T2D), skeletal fragility is associated with several changes in bone quality that are incompletely understood, and BMAd quantity increases in relationship to poor glycemic control.

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Anorexia nervosa is known to induce changes in bone parameters and an increase in bone marrow adiposity (BMA) that depend on the duration and seriousness of the disease. Previous studies have found that bone loss is associated with BMA accumulation. Sirtuin of type 1 (Sirt1), a histone deacetylase that is partly regulated by energy balance, was shown to have pro-osteoblastogenic and anti-adipogenic effects.

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The estimation of the postmortem interval (PMI) from skeletal remains represents a challenging task in forensic science. PMI is often influenced by extrinsic factors (humidity, dryness, scavengers, etc.) and intrinsic factors (age, sex, pathology, way of life, medical treatments, etc.

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Bone quality is altered mainly by osteoporosis, which is treated with modulators of bone quality. Knowledge of their mechanisms of action is crucial to understand their effects on bone quality. The goal of our study was to compare the action of alendronate (ALN) and strontium ranelate (SrRan) on the determinants of bone quality.

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The variable configuration of Raman spectroscopic platforms is one of the major obstacles in establishing Raman spectroscopy as a valuable physicochemical method within real-world scenarios such as clinical diagnostics. For such real world applications like diagnostic classification, the models should ideally be usable to predict data from different setups. Whether it is done by training a rugged model with data from many setups or by a primary-replica strategy where models are developed on a 'primary' setup and the test data are generated on 'replicate' setups, this is only possible if the Raman spectra from different setups are consistent, reproducible, and comparable.

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Background: Dual-energy computed tomography (DECT) is being considered as a non-invasive diagnostic and characterization tool in calcium crystal-associated arthropathies. Our objective was to assess the potential of DECT in distinguishing between basic calcium phosphate (BCP) and calcium pyrophosphate (CPP) crystal deposition in and around joints .

Methods: A total of 13 patients with calcific periarthritis and 11 patients with crystal-proven CPPD were recruited prospectively to undergo DECT scans.

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Owing to its antiresorptive properties, zoledronic acid (ZOL) is commonly used in the management of benign as well as malignant bone diseases. This molecule targets sites where bone is actively remodeling, and high concentrations have been reported in the jaw. The purpose of this study was to investigate whether treatment of male rats with ZOL, at a dosage equivalent to that used for antitumor treatment, impacts the short-term qualitative properties of mandibular bone independent of bone remodeling.

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Surface-enhanced Raman scattering (SERS) is a powerful and sensitive technique for the detection of fingerprint signals of molecules and for the investigation of a series of surface chemical reactions. Many studies introduced quantitative applications of SERS in various fields, and several SERS methods have been implemented for each specific application, ranging in performance characteristics, analytes used, instruments, and analytical matrices. In general, very few methods have been validated according to international guidelines.

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Osteoporosis is a disease that leads to a loss of bone mass and to alterations in the bone microarchitecture that occur in a site-specific manner; however it remains controversial in the jaw. The involvement of bone marrow adipose tissue (BMAT) in the bone metabolism has been suggested in several physiopathological contexts, such as in aging and osteoporosis. To test whether the BMAT content is related to mandibular bone loss, this study aimed to investigate the potential correlations between the trabecular bone microarchitecture on one hand and BMAT content and its spatial distribution in relation to bone surface on the other hand during aging and ovariectomy (OVX) during a long-term follow-up in a mature rat model.

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X-linked hypophosphatemia (XLH) is a skeletal disorder arising from mutations in the PHEX gene, transmitted in most cases as an X-linked dominant trait. PHEX deficiency leads to renal phosphate wasting and hypophosphatemia, as well as impaired mineralization of bone and dentin, resulting in severe skeletal and dental complications. Dentin mineralization defects appear as characteristic, large interglobular spaces resulting from the lack of fusion of calculospherites in the circumpulpal region during the mineralization process.

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Type 2 diabetes mellitus (T2DM) is a metabolic disorder associated with obesity and hyperglycemia. Roux-en-Y gastric bypass (RYGB) surgery is a common treatment for severely obese patients and T2DM. Both RYGB and T2DM are linked to increased skeletal fragility, though the exact mechanisms are poorly understood.

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The influence of six common substrates on the Raman imaging of micron-sized inorganic aerosol particles was examined. Laboratory-generated single-component particles of calcite (CaCO) and mixed particles of calcite (CaCO), nitratine (NaNO), hematite (FeO) and anglesite (PbSO) were deposited by cascade impaction on Ag, In, Si, SiO, microscope slide and TEM-grid substrates. The spectral contribution of substrates to Raman images of the deposited particles was evaluated by Multivariate Curve Resolution.

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Biological tissues have a complex and heterogeneous 3D structure, which is only partially revealed by standard histomorphometry in 2D. We here present a novel chemical compound for contrast-enhanced microfocus computed tomography (CE-CT), a Hafnium-based Wells-Dawson polyoxometalate (Hf-POM), which allows simultaneous 3D visualization of mineralized and non-mineralized skeletal tissues, such as mineralized bone and bone marrow vasculature and adipocytes. We validated the novel contrast agent, which has a neutral pH in solution, by detailed comparison with (immuno)histology on murine long bones as blueprint, and showed that Hf-POM-based CE-CT can be used for virtual 3D histology.

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X-linked hypophosphatemia (XLH) is a dento-osseous disorder caused by inactivating mutations in the PHEX gene, leading to renal phosphate wasting and hypophosphatemia, and impaired mineralization of bones and teeth. In the oral cavity, recent reports suggest a higher susceptibility of XLH patients to periodontitis, where patients present with impaired tooth cementum - a bone-like tissue involved in tooth attachment to the jaw bones and post-eruption tooth positioning - and a higher frequency of intrabony defects. In the present study, the pathobiology of alveolar bone and tooth cementum was investigated in the Hyp mouse, the murine analog of XLH.

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Non-traumatic osteonecrosis (ON) of the femoral head is a common disease affecting a young population as the peak age of diagnosis is in the 40 s. The natural history of non-traumatic ON leads to a collapse of the femoral head requiring prosthetic replacement in a 60% of cases. Although trabecular bone involvement in the collapse is suspected, the underlying modifications induced at a molecular level have not been explored in humans.

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Acellular extrinsic fiber cementum is a mineralized tissue that covers the cervical half of the tooth root surface. It contains mainly extrinsic or Sharpey's fibers that run perpendicular to the root surface to anchor the tooth via the periodontal ligament. Acellular cementum is continuously and slowly produced throughout life and exhibits an alternating bright and dark pattern under light microscopy.

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Due to their inhibitory effects on resorption, bisphosphonates are widely used in the treatment of diseases associated to an extensive bone loss. Yet, little is known about bisphosphonates effects on newly-formed bone quality. In the present study, adult male Sprague-Dawley rats (n=80) with a bone defect calvaria area were used and short-term effects of zoledronic acid (ZA) were studied on the healing bone area.

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