Search

The conventional radiotherapy protocol to treat head-and-neck cancer is usually followed by tooth-decay onset. Radiation impact on mineralized tooth structures is not well-understood. This systematic review aimed to collect the recorded effects of therapeutic radiation on tooth chemical, structural and mechanical properties, in relation with their means of investigation.Systematic search (January 01 2012 - September 30 2021) terms were "Radiotherapy", "Radiation effects", "Dental enamel", "Dentin", "Human" and "Radiotherapy" NOT "Laser".PubMed, DOSS and Embase databases were searched.Selected studies compared dental enamel, coronal and root dentin properties before and after in vitro or in vivo irradiation up to 80 Gy.The systematic search identified 353 different articles, with 28 satisfying inclusion criteria. Their reference lists provided two more. Twenty-two studies evaluated dental enamel evolution, nine assessed coronal dentin and eight concerned root dentin. Coronal and root dentin results indicate a major impact of the radiation on their organic matrix. Dental enamel's chemical properties are less modified. Enamel and root dentin's hardness are decreased by therapeutic radiation, but no consensus arises for coronal dentin.Our findings revealed some interesting information about enzymatic degradation mechanisms of dentin organic matrix and highlighted that dental hard-tissue characterization requires highly specific expertise in materials science. That scientific knowledge is necessary to design suitable protocols, adequately analyze the obtained data, and, thus, provide relevant conclusions.Better knowledge and understanding of the mechanisms involved in the degradation of enamel and dentin would enable development of new preventive and therapeutic methods for improved medical care of patients undergoing radiotherapy.

Nanohydroxyapatite (nanoHA) is the major mineral component of bone. It is highly biocompatible, osteoconductive, and forms strong bonds with native bone, making it an excellent material for bone regeneration. However, enhanced mechanical properties and biological activity for nanoHA can be achieved through enrichment with strontium ions. Here, nanoHA and nanoHA with a substitution degree of 50 and 100% of calcium with strontium ions (Sr-nanoHA_50 and Sr-nanoHA_100, respectively) were produced via wet chemical precipitation using calcium, strontium, and phosphorous salts as starting materials. The materials were evaluated for their cytotoxicity and osteogenic potential in direct contact with MC3T3-E1 pre-osteoblastic cells. All three nanoHA-based materials were cytocompatible, featured needle-shaped nanocrystals, and had enhanced osteogenic activity in vitro. The Sr-nanoHA_100 indicated a significant increase in the alkaline phosphatase activity at day 14 compared to the control. All three compositions revealed significantly higher calcium and collagen production up to 21 days in culture compared to the control. Gene expression analysis exhibited, for all three nanoHA compositions, a significant upregulation of osteonectin and osteocalcin on day 14 and of osteopontin on day 7 compared to the control. The highest osteocalcin levels were found for both Sr-substituted compounds on day 14. These results demonstrate the great osteoinductive potential of the produced compounds, which can be exploited to treat bone disease.

To evaluate in vitro the mechanical, biological, and polymerization behavior of a flowable bulk-fill composite with fibers as a dispersed phase.EverX Flow™ (GC Corporation) (EXF), one conventional bulk-fill composite (Filtek™ Bulk Fill Posterior Restorative, 3 M (FBF)), and one flowable bulk composite without fibers (SDR® flow+, Dentsply (SDR)) were tested. Samples were characterized in terms of flexural strength (ISO 4049), fracture toughness (ISO 20795-1), and Vickers hardness. Polymerization stress and volumetric shrinkage were evaluated. The in vitro biological assessment was achieved on cultured primary Human Gingival Fibroblast cells (HGF). The cell metabolic activity was evaluated using Alamar Blue assay at 1, 3, and 5 days of contact to the 3 tested composite extracts (ISO 10993) and cell morphology was evaluated by confocal microscopy. Data were submitted to One-Way analysis of variance (ANOVA) and independent t-test (α = 0.05).FBF showed statistically higher Vickers hardness and flexural modulus than EXF and SDR. However, EXF showed statistically higher KEXF had a significantly higher fracture toughness validating its potential use as a restorative material in stress bearing areas. EXF showed higher shrinkage stress values, and less cytotoxic effect. Fiber reinforced flowable composite is mainly indicated for deep and large cavities, signifying the importance for assessing its shrinkage stress and biological behavior.

While dental composite long-term aging has already been studied in the past, no data exist about the early aging while it might be detrimental regarding the composites' longevity. This study aims to better understand the effects of early water exposure on dental composites. Dental resin composites with different fillers ratio were subjected to water exposure during 24 h, 1 week, or 1 month. After photopolymerization, the samples were stored at different conditions, whether in wet or dry condition (W, D, respectively) and in wet conditions after a first 24 h storage in dry conditions (DW). Three-point bending tests were performed to measure the flexural modulus. The samples were then subjected to a sorption/desorption protocol. While the matrix alone did not undergo any mechanical degradation with exposure time, the composites matrices presented a decrease in elastic modulus. This decrease was the highest for the matrix with nonsilanized fillers. Interestingly, the DW condition was detrimental for all the samples. Regarding the sample with nonsilanized fillers in DW for 1 month presented an elastic modulus lower than the matrix alone. These results were assigned to the sorption capacity of the polymer matrix, suggesting that the diffusion mechanisms and the nature of water molecules are determinant in the composite degradation. This study showed that dental composite early degradation mechanisms after water exposure are involved in the polymer matrix postpolymerization process as soon as after 24 h. Such mechanisms are detrimental in terms of the dental composite efficiency and have to be understood.

To develop durable bone healing strategies through improved control of bone repair, it is of critical importance to understand the mechanisms of bone mechanical integrity when in contact with biomaterials and implants. Bone mechanical integrity is defined here as the adaptation of structural properties of remodeled bone in regard to an applied mechanical loading. Accordingly, the authors present why future investigations in bone repair and regeneration should emphasize osteocytes that surround matrices. Osteocytes are mechanosensitive cells considered as the orchestrators of bone remodeling, which is the biological process involved in bone homeostasis. These bone cells are trapped in an interconnected porous network, the lacunocanalicular network, which is embedded in a bone mineralized extracellular matrix. As a consequence of an applied mechanical loading, the bone deformation results in the deformation of this lacunocanalicular network inducing a shift in interstitial fluid pressure and velocity, thus resulting in osteocyte stimulation. The material environment surrounding each osteocyte, the so called perilacunar and pericellular matrices properties, define its mechanosensitivity. While this mechanical stimulation pathway is well known, the laws used to predict bone remodeling are based on strains developing at a tissue scale, suggesting that these strains are related to the shift in fluid pressure and velocity at the lacunocanalicular scale. While this relationship has been validated through observation in healthy bone, the fluid behavior at the bone-implant interface is more complex. The presence of the implant modifies fluid behavior, so that for the same strain at a tissue scale, the shift in fluid pressure and velocity will be different than in a healthy bone tissue. In that context, new markers for bone mechanical integrity, considering fluid behavior, have to be defined. The viewpoint exposed by the authors indicates that the properties of the pericellular and the perilacunar matrices have to be systematically investigated and used as structural markers of fluid behavior in the course of bone biomaterial development.

Different kinds of interactions between the restorative material and mineralized dental tissues result in secondary caries around dental composites. Of these, the mechanical interactions have to be carefully investigated. Due to the elastic mismatch between dental tissues and the composite restoration, complex stresses and strains develop at their interface. This complex mechanical environment disturbs the demineralization-remineralization equilibrium of dental hard tissues. The fluid flow both over and within enamel and dentin, associated with their complex ultrastructure and mechanical behavior, is a key factor. It is known that external mechanical loading can indirectly promote the dissolution of enamel and dentin through a pumping action of cariogenic fluids in and out of microgaps at the interface between mineralized tissues and composite. Mechanical loading can also directly influence the physicochemical behavior of dental hard tissues by inducing complex strain and stress fields on the crystal scale. It is important to consider both the direct and indirect paths by which mechanical loading can influence the apatite dissolution kinetics. Therefore, a system atic approach should be used to investigate the mechanism of secondary caries formation considering the tooth-composite interface as a unique complex in which each element has an influence on the other.

International audience; Human cortical bone fracture toughness depends on the anatomical locations under quasi-static loading. Recent results also showed that under fall-like loading, cortical bone fracture toughness is similar at different anatomical locations in the same donor. While cortical bone toughening mechanisms are known to be dependent on the tissue architecture under quasi-static loading, the fracture mechanisms during a fall are less studied. In the current study, the structural parameters of eight paired femoral diaphyses, femoral necks and radial diaphyses were mechanically tested under quasi-static and fall-like loading conditions (female donors, 70 ± 14 y.o., [50–91 y.o.]). Synchrotron radiation micro-CT imaging was used to quantify the amount of micro-cracks formed during loading. The volume fraction of these micro-cracks was significantly higher within the specimens loaded under a quasi-static condition than under a loading representative of a fall. Under fall-like loading, there was no difference in crack volume fraction between the different paired anatomical locations. This result shows that the micro-cracking toughening mechanism depends both on the anatomical location and on the loading condition.

International audience; Background: The toxicological risk of Co-Cr dental alloys is actually a sensitive subject with the European regulatory changes, namely regulation (EU) 2017/745 and annex VI to the CLP regulation (EC) 1972/2008.Objectives: The objective of this review is to conduct a rigorous analysis of the cytocompatibility of cobalt–chromium (Co-Cr) dental alloys. Considering various parameters such as cytotoxicity, type IV hypersensitivity reaction, sensitization, and irritation, we investigated evidence of toxicity of Co-Cr in human dental applications.Data sources: Specific search strategies were performed in three electronic databases, namely Medline, Embase, and Web of Science, using a main restriction in the search regarding the publication date (1995–2022).Study selection: Out of a total of 836 articles, only 21 studies were selected and analyzed according to PRISMA methodology.Results: Among them, 10 in vitro studies using human samples and 11 in vivo studies on human patients were distinguished. Most of the in vitro studies confirmed that Co-Cr alloys have a good cytocompatibility compared to Ni alloys. Regarding the in vivo studies, it appeared that Co-Cr could rarely cause sensitization, irritation, and allergic reactions. Reactions were mainly observed for people allergic to Co or Cr. Nevertheless, titanium-based materials showed better results.Conclusions: This study proposes a new state of the art on Co-Cr dental alloys and will thus be very useful for carrying out additional studies.Relevance: This review will help practitioners in their daily clinical choice

International audience; The periodontal biomechanical environment is very difficult to investigate. By the complex geometry and composition of the periodontal ligament, its mechanical behavior is very dependent on the type of loading (compressive vs. tensile loading; static vs. cyclic loading; uniaxial vs. multiaxial) and the location around the root (cervical, middle, or apical). These different aspects of the periodontal ligament make it difficult to develop a functional biomaterial to treat periodontal attachment due to periodontal diseases. This review aims to describe the structural and biomechanical properties of the periodontal ligament. Particular importance is placed in the close interrelationship that exists between structure and biomechanics: the periodontal ligament structural organization is specific to its biomechanical environment, and its biomechanical properties are specific to its structural arrangement. This balance between structure and biomechanics can be explained by a mechanosensitive periodontal cellular activity. These specifications have to be considered in the further tissue engineering strategies for the development of an efficient biomaterial for periodontal tissues regeneration.

The strong dependence between cortical bone elasticity at the millimetre-scale (mesoscale) and cortical porosity has been evidenced by previous studies. However, bone is an anisotropic composite material made by mineral, proteins and water assembled in a hierarchical structure. Whether the variations of structural and compositional properties of bone affect the different elastic coefficients at the mesoscale is not clear. Aiming to understand the relationships between bone elastic properties and compositions and microstructure, we applied state-of-the-art experimental modalities to assess these aspects of bone characteristics. All elastic coefficients (stiffness tensor of the transverse isotropic bone material), structure of the vascular pore network, collagen and mineral properties were measured in 52 specimens from the femoral diaphysis of 26 elderly donors. Statistical analyses and micromechanical modeling showed that vascular pore volume fraction and the degree of mineralization of bone are the most important determinants of cortical bone anisotropic mesoscopic elasticity. Though significant correlations were observed between collagen properties and elasticity, their effects in bone mesoscopic elasticity were minor in our data. This work also provides a unique set of data exhibiting a range of variations of compositional and microstructural cortical bone properties in the elderly and gives strong experimental evidence and basis for further development of biomechanical models for human cortical bone. STATEMENT OF SIGNIFICANCE: This study reports the relationships between microstructure, composition and the mesoscale anisotropic elastic properties of human femoral cortical bone in elderly. For the first time, we provide data covering the complete anisotropic elastic tensor, the microstructure of cortical vascular porosity, mineral and collagen characteristics obtained from the same or adjacent samples in each donor. The results revealed that cortical vascular porosity and degree of mineralization of bone are the most important determinants of bone anisotropic stiffness at the mesoscale. The presented data gives strong experimental evidence and basis for further development of biomechanical models for human cortical bone.

International audience; Human cortical bone has a complex hierarchical structure that is periodically remodelled throughout a lifetime. This microstructure dictates the mechanical response of the tissue under a critical load. If only some structural features, such as the different porosities observed in bone, are primarily studied, then investigations may not fully consider the osteonal systems in three-dimensions (3D). Currently, it is difficult to differentiate osteons from interstitial tissue using standard 3D characterization methods. Synchrotron radiation micro-computed tomography (SR-μCT) in the phase contrast mode is a promising method for the investigation of osteons. In the current study, SR-μCT imaging was performed on cortical bone samples harvested from eight human radii (female, 50–91 y.o.). The images were segmented to identify Haversian canals, osteocyte lacunae, micro-cracks, as well as osteons. The significant correlation between osteonal and Haversian canal volume fraction highlights the role of the canals as sites where bone remodelling is initiated. The results showed that osteocyte lacunae morphometric parameters depend on their distance to cement lines, strongly suggesting the evolution of biological activity from the beginning to the end of the remodelling process. Thus, the current study provides new data on 3D osteonal morphometric parameters and their relationships with other structural features in humans.

Human bone is known to adapt to its mechanical environment in a living body. Both its architecture and microstructure may differ between weight-bearing and non-weight-bearing bones. The aim of the current study was to analyze in three dimensions, the morphology of the multi-scale porosities on human cortical bone at different locations. Eight paired femoral diaphyses, femoral necks, and radial diaphyses were imaged using Synchrotron Radiation µCT with a 0.7 µm isotropic voxel size. The spatial resolution facilitates the investigation of the multiscale porosities of cortical bone, from the osteonal canals system down to the osteocyte lacunar system. Our results showed significant differences in the microstructural properties, regarding both osteonal canals and osteocytes lacunae, between the different anatomical locations. The radius presents significantly lower osteonal canal volume fraction and smaller osteonal canals than the femoral diaphysis or neck. Osteocytes lacunae observed in the radius are significantly different in shape than in the femur, and lacunar density is higher in the femoral neck. These results show that the radius, a non-weight-bearing bone, is significantly different in terms of its microstructure from a weight-bearing bone such as the femur. This implies that the cortical bone properties evaluated on the femoral diaphysis, the main location studied within the literature, cannot be generalized to other anatomical locations.

Objectives The purpose of this work is a proof of concept to introduce a new quantitative 3D-analysis of dental erosion obtained by focused ion beam (FIB) tomography associated with silver nitrate penetration into porosities in etched enamel. Methods One sample selected was sound enamel after removal of the aprismatic surface. The other was studied after applying an additional attack with orthophosphoric acid. Both surfaces were infiltrated with silver nitrate via immersion. After dehydration, samples were observed in a dual column FIB/SEM station. Serial FIB sectioning was conducted with a current of 3 nA at 30 keV and an increment step of 20 nm for the healthy enamel and of 40 nm for the etched one. 3D analysis was performed with Fiji software and BoneJ plugin and several parameters were obtained to characterize the tissue: non-mineralized phase content (NMP), connected porosity fraction (CPF) and degree of anisotropy (DA) of the NMP. Results Healthy enamel showed an NMP content of 0.5 vol.%, with a bimodal distribution of non-mineralized regions, inside the prisms and between the prisms. No silver penetration was noticed in the healthy enamel, demonstrating the absence of open porosity. In contrast, silver nitrate penetration after acidic exposure was observed, up to a depth of 12 μm, which allowed the calculation of an interconnected porosity volume fraction (CPF) of 3.1 vol.%, mostly between the prisms. Values for DA of 0.56 for sound enamel and 0.81 for acid-etched surface were determined, highlighting a higher degree of anisotropy in the latter. Significance Quantitative analysis of FIB tomography using NMP, CPF and DA should contribute to a better understanding and follow up of dental erosion, correlation between erosion and attrition or abrasion process, and the ability to develop enamel remineralization procedures.

EuroMech Colloquium 594 - Bone remodeling: multiscale mechanical models and multiphysical aspects, NANCY, FRANCE, 15-/05/2018 - 19/05/2018

42e Congrès de la Société de Biomécanique, Reims, France, 02-/11/2017 - 02/11/2017; Bone quality and fracture prediction are dependent topics that have long been blurry, quite unreachable links to establish. The International Osteoporosis Foundation expects an increase of nearly three times more hip fractures in the population by 2050. Regarding this expectation, the MULTIPS project aims to predict the bone fracture risk by quantifying the bone quality using different methods. One of them is the Degree of Mineralization of the Bone (DMB (g.cm?3)) analysis by X-ray scanning of a 100 ± 1 ?m thick section of embedded bone. The aim of the present study is to assess the effect of bone mineralization (DMB) on the toughness of the bone which is the propensity to resist to fracture.

Bone properties at all length scales have a major impact on the fracture risk in disease such as osteoporosis. However, quantitative 3D data on bone tissue at the cellular scale are still rare. Here we propose to use magnified X-ray phase nano-CT to quantify bone ultra-structure in human bone, on the new setup developed on the beamline ID16A at the ESRF, Grenoble. Obtaining 3D images requires the application of phase retrieval prior to tomographic reconstruction. Phase retrieval is an ill-posed problem for which various approaches have been developed. Since image quality has a strong impact on the further quantification of bone tissue, our aim here is to evaluate different phase retrieval methods for imaging bone samples at the cellular scale. Samples from femurs of female donors were scanned using magnified phase nano-CT at voxel sizes of 120 and 30 nm with an energy of 33 keV. Four CT scans at varying sample-to-detector distances were acquired for each sample. We evaluated three phase retrieval methods adapted to these conditions: Paganin’s method at single distance, Paganin’s method extended to multiple distances, and the contrast transfer function (CTF) approach for pure phase objects. These methods were used as initialization to an iterative refinement step. Our results based on visual and quantitative assessment show that the use of several distances (as opposed to single one) clearly improves image quality and the two multi-distance phase retrieval methods give similar results. First results on the segmentation of osteocyte lacunae and canaliculi from such images are presented.

Bone quality encompasses bone properties that contribute to fracture risk, such as bone stiffness, microstructure, matrix constituents or tissue material properties. These aspects cannot be quantified in-vivo except for stiffness, a surrogate biomarker of strength, which can be assessed using quantitative ultrasound techniques. To better predict bone fracture risk, investigating the relationships between stiffness and other bone quality factors is important. Toward this goal, our group adapted resonant ultrasound spectroscopy (RUS) to precisely measure the whole set of stiffness coefficients of cortical bone by improving the signal processing and automatizing the inversion procedure based on a Bayesian framework. In this work, we present the relationships between bone quality biomarkers including stiffness, fracture toughness, microstructure, mineralization, cross-links and collagen.

22nd Congress of the European Society of Biomechanics, SEVILLE, ESPAGNE, 10-/07/2017 - 13/07/2017; A recent study showed that human cortical bone fracture toughness is higher at the radial diaphysis compared to the femoral diaphysis or femoral neck when loaded under quasi-static rate. Radius seems to be able to undergo more plastic mechanisms that slow down crack propagation. It has also been shown that the ratio between mature and immature enzymatic crosslinks (called CX) may have an influence on the non-linear behavior of human cortical bone. The aim of this study is to investigate the relationships between toughness and the ratio CX of human cortical bones.

21st International Bone Densitometry Workshop & 7th European Symposium on Ultrasonic Characterization of Bone, KLOSTER BANZ, ALLEMAGNE, 26-/06/2017 - 30/06/2017; This study aims at investigating the relationship between different aspects of bone quality and understanding how bone quality may affect stiffness at the mm-scale and toughness. The transverse isotropic effective stiffness tensor was measured by resonant ultrasound spectroscopy (RUS) and the vascular porosity was estimated from synchrotron radiation micro-computed tomography (SR-¼CT) images. A cross-section at the mid-diaphysis was sectioned from the left femur of 27 human cadavers. Then, a set of 54 parallelepiped-shape samples (size 3x4x5 mm3) was prepared for RUS measurements and SR-¼CT imaging at ERSF (voxel size 6.5 µm). Another set of adjacent 54 samples (size 3x4x25 mm3) was harvested for mechanical testing and the remaining material was used for cross-links and collagen quantification. These last samples were divided into two samples (1x2x25 mm3) then notched (1 mm length) in their middle, in the transverse direction. Three-point bending tests were conducted at two strain rates 10-4 s-1 and 10-1 s-1 to measure toughness (quasi-static KJcStat and dynamic KJcDyn). Specimen dimensions are defined by the anatomical shape of femoral diaphysis: radial (axis 1), circumferential (axis 2) and axial direction (axis 3). Immature and mature collagen crosslinks were separated by reversed-phase HPLC method and quantified using fluorescence and mass spectrometry detection. Relationships between variables were investigated with Spearman's rank correlation coefficients. The bone-quality markers analysed here seem to differently affect toughness and stiffness. Indeed, markers that showed an effect in toughness did not in stiffness. Vascular porosity was significantly correlated with all stiffness coefficients but not with toughness. Enzymatic immature cross-links significantly correlated with stiffness coefficients, while only the non-enzymatic cross link pentosidine significantly affected toughness. Finally, the existing correlations between elastic parameters and toughness are shown in Table 1. Knowing the effects of these markers in the mechanical properties of bone may provide a more precise estimate for the fracture risk.

44th European Calcified Tissue Society congress, SALZBOURG, AUTRICHE, 13-/05/2017 - 16/05/2017; X-Ray CT imaging is a choice technique to analyze bone tissue at different scales. X-ray CT at the microscopic scale (µCT) has become a standard technique for the three-dimensional (3D) investigation of bone micro-architecture. However, the three dimensional observation of bone micro-damage remains challenging due to the small size of the damage relative to the attainable spatial resolution

Bone fracture is a major health issue worldwide and consequently there have been extensive investigations into the fracture behavior of human cortical bone. However, the fracture properties of human cortical bone under fall-like loading conditions remains poorly documented. Further, most published research has been performed on femoral diaphyseal bone, whereas it is known that the femoral neck and the radius are the most vulnerable sites to fracture. Hence, the aim of this study is to provide information on human cortical bone fracture behavior by comparing different anatomical sites including the radius and the femoral neck acquired from 32 elderly subjects (50 – 98 y.o.). In order to investigate the intrinsic fracture behavior of human cortical bone, toughness experiments were performed at two different strain rates: standard quasi-static conditions, and a higher strain rate representative of a fall from a standing position. The tests were performed on paired femoral neck, femoral, tibial and radius diaphyseal samples. Linear elastic fracture toughness and the non-linear J-integral method were used to take into account both the elastic and non-elastic behavior of cortical bone. Under quasi-static conditions, the radius presents a significantly higher toughness than the other sites. At the higher strain rate, all sites showed a significantly lower toughness. Also, at the high strain rate, there is no significant difference in fracture properties between the four anatomical sites. These results suggest that regardless of the anatomical site (femur, femoral neck, tibia and radius), the bone has the same fracture properties under fall loading conditions. This should be considered in biomechanical models under fall-like loading conditions.

21st International Bone Densitometry Workshop & 7th European Symposium on Ultrasonic Characterization of Bone, KLOSTER BANZ, ALLEMAGNE, 26-/06/2017 - 30/06/2017; The comprehension of crack propagation mechanisms in human cortical bone is of great importance for the improvement of fracture risk prediction. It is known that crack advance can be slowed down by toughening mechanisms, such as micro-damage formation near the crack tip. These mechanisms are thought to be related to bone microstructure. Recent results showed that under low loading rate, the radius diaphysis resisted better to crack propagation than the femoral diaphysis or neck (Gauthier et al., JMBBM, 2017). X-Ray CT imaging at the microscopic scale (µCT) is a standard method for the assessment of human cortical bone architecture but the assessment of micro-damage requires sub-micrometric spatial resolution. The aim of the current study is to investigate the microstructure and micro-damages of paired anatomical locations subjected to toughness experiments. We assessed the microstructure of human cortical bone of 8 paired radius diaphysis, femoral diaphysis and femoral necks (female, 50 - 91 y.o.) using Synchrotron Radiation (SR)-µCT in absorption and phase modes (voxel size of 0.7 µm). Image acquisition was performed on two different volumes of interest in each sample: the first one corresponds to a region where no particular mechanical stress was applied, in order to investigate structural differences between the locations; the second one, to a damaged region where three-point bending toughness tests were performed under a quasi-static strain rate (10-4 s-1), to evaluate structural changes, as micro-damages formation, due to crack propagation. Phase µCT allows the enhancement of the visibility of osteons, that might play a major role in crack propagation mechanisms as illustrated on Figure 1. After acquisition, we designed an image processing workflow to extract quantitative information on bone structural elements, such as Haversian canals, osteons or lacunae. Cracks and micro-damages were also segmented and quantified to investigate their relationships with human cortical bone toughness.

2016 IEEE International Ultrasonics Symposium, TOURS, FRANCE, 18-/09/2016 - 21/09/2016; Key factors of fracture risk, such as cortical bone thinning and porosity increase, are imperfectly captured with currently available X-ray densitometry techniques. A presentation at this symposium (IUS2015) evidenced the feasibility of analyzing the waveguide response of ex vivo long bones using axial transmission (AT), but has shown mixed results for porosity estimates, caused by non-unicity of the inverse problem solution. Our goal was to extend our previous study, first by increasing significantly the number of specimens investigated and second by incorporating some prior knowledge on the cortical thickness in the inverse problem.

22d congress of the European Society of Biomechanics (ESB), LYON, FRANCE, 10-/07/2016 - 13/07/2016; Cortical microstructure (porosity and thickness) is a major determinant of fragility fracture risk across life in human. Age-related alterations in bone remodeling result in a thinner and more porous cortex, traits that are both associated with higher risk for non-vertebral fracture. However, whether these age-related alterations impact similarly loaded and non-loaded bones is not known. We hypothesized that the cortical thickness and porosity are age-dependent and could match between loaded (Tibia) and non-loaded bones (Radius).

International audience; Most of the fractures occur at the radius or at the femoral neck after a fall, involving high strain rate (10-1.s-1) [1]. Cortical bone toughness is usually measured under quasi-static loading condition even though it is known to have viscoelastic properties [2]. A recent study on one subject actually showed that the toughness of femoral shaft specimens is lower at a strain rate representative of a fall [3]. We hypothesize this effect could be the same whatever the anatomical location. The aim of this study is thus to quantify human cortical bone toughness using paired radii and femurs (neck and shaft) considering two strain rates (quasi-static and representative of a fall).

22d congress of the European Society of Biomechanics, LYON, FRANCE, 10-/07/2016 - 13/07/2016; Cortical bone plays a major role in fracture of long bones. Cortical bone thickness and its porosity are supposed to be ones of the determinants of the bone strength. Such parameters can be assessed ex vivo by X-ray microcomputed tomography. The aim of this study is to investigate the link between human tibial strength and its cortical thickness and porosity.

International audience; In the world, a bone fracture due to osteoporosis occurs every 3 seconds (International Osteoporosis Foundation). Thus, it is obvious that bone fracture is a major concern. In clinics the assessment of the risk of fracture is based on the measurement of the bone mineral density (i.e. bone quantity in gram per cm²). Even if this method is currently the gold standard it is not sufficiently discriminant. Indeed, 50% of the patients having a fracture were diagnosed as non-osteoporotic (Siris et al., 2004). To overcome this limitation finite element models have been proposed. Such models can accurately predict the bone strength (e.g. (Duchemin et al., 2008; van Rietbergen and Ito, 2015) but there is no clear evidence that these models can better predict the fracture risk (van Rietbergen and Ito, 2015). Currently these models consider quasi-static loadings. However among elderly bone fractures occur during a fall. In case of a fall from a standing height people will hit the floor at an average speed of 2 m/s (Tan et al., 2006) and a corresponding strain rate of 0.1/s (Földhazy et al., 2005). We made the assumption that this loading speed should be considered in the bone loading.Bone structures (e.g. the femur or the radius) are made of two materials: cortical bone and cancellous bone. It was shown that bone strength of the femur is mainly due to the cortical bone (Holzer et al., 2009).speed related to a fall. Thus, the goal of our current research is to assess the cortical bone toughness under a strain rate of 0.1/s, representing a fall, and to compare, on paired samples, cortical bone toughness under a quasi-static loading configuration (considered in a wide majority of the studies in the literature e.g. (Bonfield and Datta, 1976; Nalla et al., 2004)).Our presentation will be dedicated to the presentation of our latest results regarding speed effect on human cortical bone toughness through biomechanical experiments and 3D imaging at the nanoscale.AcknowledgmentsThis work was performed within the framework of the LABEX PRIMES (ANR-11-LABX-0063) of Université de Lyon, within the program "Investissements d'Avenir" (ANR-11-IDEX-0007) operated by the French National Research Agency (ANR). Rémy Gauthier is supported by a grant from the Région Rhône-Alpes.

International audience; The mechanisms of bone fragility in relation to diseases such as osteoporosis remain only partially understood. Extensive attention has been devoted to the osteocyte cell network, which plays a central role in bone remodeling, but for which observation remains challenging. To assess bone nano-structure, we propose to use a new 3D X-ray phase nano-CT setup developed at the ESRF (European Synchrotron Radiation Facility) in Grenoble, which targets to reach isotropic spatial resolution up to 20 nm. Images of cortical bone samples with isotropic voxel size of 120nm, 50nm and 30nm are presented.

Herein, we investigated the survival roles of Fak, Src, MEK/Erk, and PI3-K/Akt-1 in intestinal epithelial cancer cells (HCT116, HT29, and T84), in comparison to undifferentiated and differentiated intestinal epithelial cells (IECs). We report that: (1) cancer cells display striking anoikis resistance, as opposed to undifferentiated/differentiated IECs; (2) under anoikis conditions and consequent Fak down-activation, cancer cells nevertheless exhibit sustained Fak–Src interactions and Src/MEK/Erk activation, unlike undifferentiated/differentiated IECs; however, HCT116 and HT29 cells exhibit a PI3-K/Akt-1 down-activation, as undifferentiated/differentiated IECs, whereas T84 cells do not; (3) cancer cells require MEK/Erk for survival, as differentiated (but not undifferentiated) IECs; however, T84 cells do not require Fak and HCT116 cells do not require PI3-K/Akt-1, in contrast to the other cells studied; (4) Src acts as a cornerstone in Fak-mediated signaling to MEK/Erk and PI3-K/ Akt-1 in T84 cells, as in undifferentiated IECs, whereas PI3-K/Akt-1 is Src-independent in HCT116, HT29 cells, as in differentiated IECs; and (5) EGFR activity inhibition abrogates anoikis resistance in cancer cells through a loss of Fak–Src interactions and down-activation of Src/ MEK/Erk (T84, HCT116, HT29 cells) and PI3-K/Akt-1 (T84 cells). Hence, despite distinctions in signaling behavior not necessarily related to undifferentiated or differentiated IECs, intestinal epithelial cancer cells commonly display an EGFR-mediated sustained activation of Src under anoikis conditions. Furthermore, such sustained Src activation confers anoikis resistance at least in part through a consequent sustenance of Fak–Src interactions and MEK/Erk activation, thus not only overriding Fak-mediated signaling to MEK/Erk and/or PI3-K/Akt-1, but also the requirement of Fak and/or PI3-K/Akt-1 for survival. J. Cell. Biochem. 107: 639–654, 2009. 2009 Wiley-Liss, Inc.

The molecular determinants which dictate survival and apoptosis/anoikis in human intestinal crypt cells remain to be fully understood. To this effect, the roles of beta1 integrin/Fak/Src signaling to the PI3-K/Akt-1, MEK/Erk, and p38 pathways, were investigated. The regulation of six Bcl-2 homologs (Bcl-2, Mcl-1, Bcl-X(L), Bax, Bak, Bad) was likewise analyzed. We report that: (1) Anoikis causes a down-activation of Fak, Src, Akt-1 and Erk1/2, a loss of Fak-Src association, and a sustained/enhanced activation of p38beta, which is required as apoptosis/anoikis driver; (2) PI3-K/Akt-1 up-regulates the expression of Bcl-X(L) and Mcl-1, down-regulates Bax and Bak, drives Bad phosphorylation (both serine112/136 residues) and antagonizes p38beta activation; (3) MEK/Erk up-regulates Bcl-2, drives Bad phosphorylation (serine112 residue), but does not antagonize p38bactivation; (4) PI3-K/Akt-1 is required for survival, whereas MEK/Erk is not; (5) Src acts as a cornerstone in the engagement of both pathways by beta1 integrins/Fak, and is crucial for survival; and (6) beta1 integrins/Fak and/or Src regulate Bcl-2 homologs as both PI3-K/Atk-1 and MEK/Erk combined. Hence, beta1 integrin/Fak/Src signaling translates into integrated mediating functions of p38beta activation and regulation of Bcl-2 homologs by PI3-K/Akt-1 and MEK/Erk, consequently determining their requirement (or not) for survival.

Human intestinal epithelial cell survival and anoikis are distinctively regulated according to the state of differentiation. In the present study, we analyzed the roles of focal adhesion kinase (Fak)/Src signaling to the PI3-K/Akt-1 and mitogen-activated protein kinase (MEK)/extracellular regulated kinases (Erk) pathways, within the context of such differentiation-state distinctions. Anoikis was induced by inhibition of β1 integrins (antibody blocking), inhibition of Fak (pharmacologic inhibition or overexpression of dominant negative mutants), or by maintaining cells in suspension. Activation parameters of Fak, Src, Akt-1, and Erk1/2 were analyzed. Activities of Src, Akt-1, or Erk1/2 were also blocked by pharmacological inhibition or by overexpression of dominant-negative mutants. We report that: (1) the loss or inhibition of β1 integrin binding activity causes anoikis and results in a down-activation of Fak, Src, Akt-1, and Erk1/2 in both undifferentiated, and differentiated cells; (2) the inhibition of Fak likewise causes anoikis and a down-activation of Src, Akt-1, and Erk1/2, regardless of the differentiation state; (3) Src, PI3-K/Akt-1, and MEK/Erk contribute to the survival of differentiated cells, whereas MEK/Erk does not play a role in the survival of undifferentiated ones; (4) the inhibition/loss of β1 integrin binding and/or Fak activity results in a loss of Src engagement with Fak, regardless of the state of differentiation; and (5) Src contributes to the activation of both the PI3-K/Akt-1 and MEK/Erk pathways in undifferentiated cells, but does not influence PI3-K/Akt-1 in differentiated ones. Hence, Fak/Src signaling to the PI3-K/Akt-1 and MEK/Erk pathways undergoes a differentiation state-specific uncoupling which ultimately reflects upon the selective engagement of these same pathways in the mediation of intestinal epithelial cell survival. J. Cell. Physiol. 212:717–728, 2007. © 2007 Wiley-Liss, Inc.

International audience

Colloque avec actes et comité de lecture. Internationale.; International audience; L'ostéoporose cause environ 25 000 fractures par jour en Europe. Les méthodes utilisées en clinique pour établir son diagnostic sont basées sur des mesures densitométriques. Cependant, les résultats obtenus à l'aide de cette technique ne sont pas assez discriminant, 50% des femmes ayant subi une fracture ostéoporotique ne sont pas diagnostiquées comme atteintes d'ostéoporose selon les mesures densitométriques. Dans le but d'améliorer les prédictions sur le risque de fracture, de nouvelles méthodes sont envisagées, notamment le développement de modèles numériques simulant le comportement mécanique de l'os face à la fracture. Les données utilisées dans ces simulations ont été déterminées à partir d'essais mécaniques sous chargement quasi-statique. Or une fracture ostéoporotique est généralement la conséquence d'une chute du sujet, équivalent à un chargement rapide. L'os étant un matériau viscoélastique, l'objectif de cette étude est de mesurer la ténacité de l'os cortical humain sous chargement quasi-statique et sous chargement rapide pour simuler un cas de chute. Les résultats montrent que la ténacité de l'os cortical humain est plus faible pour une vitesse de chargement rapide.

The homeobox gene Cdx2 is involved in the regulation of the expression of intestine specific markers such as sucrase-isomaltase and lactase-phlorizin hydrolase. Previous studies performed with immortalized or transformed intestinal cell lines have provided evidence that Cdx2 can promote morphological and functional differentiation in these experimental models. However, no data exist concerning the implication of this factor in normal human intestinal cell physiology. In the present work, we have investigated the role of Cdx2 in normal human intestinal epithelial crypt (HIEC) cells that lack this transcription factor. The establishment of HIEC cells expressing Cdx2 in an inducible manner shows that forced expression of Cdx2 significantly alters the proliferation of intestinal crypt cells and stimulates dipeptidylpeptidase IV expression but is not sufficient to trigger intestinal terminal differentiation. These observations suggest that Cdx2 requires additional factors to activate the enterocyte differentiation program in normal undifferentiated cells.

Background Integrins are known to be important contributors to cancer progression. We have previously shown that the integrin β4 subunit is up-regulated in primary colon cancer. Its partner, the integrin α6 subunit, exists as two different mRNA splice variants, α6A and α6B, that differ in their cytoplasmic domains but evidence for distinct biological functions of these α6 splice variants is still lacking. Methods In this work, we first analyzed the expression of integrin α6A and α6B at the protein and transcript levels in normal human colonic cells as well as colorectal adenocarcinoma cells from both primary tumors and established cell lines. Then, using forced expression experiments, we investigated the effect of α6A and α6B on the regulation of cell proliferation in a colon cancer cell line. Results Using variant-specific antibodies, we observed that α6A and α6B are differentially expressed both within the normal adult colonic epithelium and between normal and diseased colonic tissues. Proliferative cells located in the lower half of the glands were found to predominantly express α6A, while the differentiated and quiescent colonocytes in the upper half of the glands and surface epithelium expressed α6B. A relative decrease of α6B expression was also identified in primary colon tumors and adenocarcinoma cell lines suggesting that the α6A/α6B ratios may be linked to the proliferative status of colonic cells. Additional studies in colon cancer cells showed that experimentally restoring the α6A/α6B balance in favor of α6B caused a decrease in cellular S-phase entry and repressed the activity of c-Myc. Conclusion The findings that the α6Bβ4 integrin is expressed in quiescent normal colonic cells and is significantly down-regulated in colon cancer cells relative to its α6Aβ4 counterpart are consistent with the anti-proliferative influence and inhibitory effect on c-Myc activity identified for this α6Bβ4 integrin. Taken together, these findings point out the importance of integrin variant expression in colon cancer cell biology.

The expression of the five laminin alpha-chains was analyzed in the developing and mature human small intestine at the protein and transcript levels in order to further delineate specific involvement of individual laminins in relation to the epithelial cell state as defined along the functional crypt-villus axis. The results show that all of the alpha-laminin transcripts are expressed in significant amounts in the small intestine relative to a panel of other tissues and organs. Further analysis of their expression by indirect immunofluorescence and semi-quantitative and quantitative RT-PCR demonstrates a close correlation between transcript and protein expression, distinct epithelial and mesenchymal origins, as well as differential occurrence in intestinal basement membranes according to developmental stage, along the crypt-villus axis and in compartment-related experimental intestinal cell models. Taken together, the data point out the prime importance of alpha2-, alpha3-, and alpha5-containing laminins for the development and maintenance of the functional human intestinal epithelium.

Background & Aims: Little is known of the signaling events implicated in the induction of human enterocytic anoikis. In the present study, we analyzed the role of the stress-activated protein kinase p38 in this process. Methods: Anoikis was induced in undifferentiated and differentiated enterocytes by inhibition of focal adhesion kinase (Fak; pharmacologic inhibition or overexpression of a dominant negative form) or β1 integrins (antibody blocking), or by maintaining cells in suspension. Expression/activation parameters of p38 (isoforms α, β, γ, δ) and of the Fak/phosphatidylinositol-3-kinase (PI3-K)/Akt anoikis-suppressing pathways were analyzed. Kinase activities of p38 isoforms also were blocked by pharmacologic inhibitors or by overexpression of dominant-negative forms. Results: (1) p38 activation is sustained transiently after induction of anoikis in both undifferentiated and differentiated enterocytes; (2) such sustenance of p38 activation is associated with a down-regulation of the Fak/PI3-K/Akt pathway; (3) distinct profiles of p38 isoform expression are exhibited by undifferentiated (α, β, γ) and differentiated (α, γ, δ) enterocytes; (4) none of the 4 known p38 isoforms was found to promote cell survival in either differentiation state; and (5) only p38β and p38δ are required specifically for anoikis in undifferentiated and differentiated cells, respectively. Conclusions: Distinct p38 isoforms play a major role in the induction of enterocytic anoikis and the regulation of such selective p38 isoform-mediated anoikis is linked with the state of cell differentiation. These data provide novel insights into the synchronized regulation of cell survival/death required in the epithelial renewal process along the human intestinal crypt-villus axis. GASTROENTEROLOGY 2002;123:1980-1991

Ultrasonics Symposium (IUS), 2017 IEEE International, WASHINGTON, ETATS-UNIS, 06-/09/2017 - 09/09/2017; Bone quality encompasses bone properties that contribute to fracture risk, such as bone stiffness, microstructure, matrix constituents or tissue material properties. These aspects cannot be quantified in-vivo except for stiffness, a surrogate biomarker of strength, which can be assessed using quantitative ultrasound techniques. To better predict bone fracturerisk, investigating the relationships between stiffness and other bone quality factors is important. Toward this goal, our group adapted resonant ultrasound spectroscopy (RUS) to precisely measure the whole set of stiffness coefficients of cortical bone by improving the signal processing and automatizing the inversion procedure based on a Bayesian framework. In this work, we present the relationships between bone quality biomarkers including stiffness, fracture toughness, microstructure, mineralization, cross-links and collagen.Statement of Contribution/MethodsFrom the mid-diaphysis of the femoral cortex of 27 human donors, 54 cuboid specimens (3x4x5 mm3, axis 1=radial; axis 2=circumferential; axis 3=axial) were prepared. The mesoscale transverse isotropic stiffness tensor Cij of the specimens was measured by RUS. The microstructure (i.e., vascular porosity) and degree of mineralization of bone (DMB)were estimated from synchrotron radiation micro-computed tomography (voxel size 6.5 ?m). Another set of 54 samples (3x4x25 mm3) which were adjacent to the previous ones, was harvested for mechanical testing. Each of them were divided into two samples (1x2x25 mm3) then notched (1 mm length) in their middle in the transverse direction. Three-pointbending tests were conducted at two strain rates 10-4 s-1 and 10-1 s-1 to measure the fracture toughness (quasi-static KJcStat and dynamic KjcDyn). Biochemical tests were conducted on small adjacent bone fragments to assess collagen quantity and cross-links.Results/DiscussionWhile all the stiffness coefficients significantly correlate with toughness (-0.35 < r < -0.53, p < 0.05) except for C33, different biomarkers seem to differently affect toughness and stiffness. Indeed, markers that showed an effect on toughness did not on stiffness (Table 1). This work demonstrates the correlations between cortical bone quality biomarkers and givesinsights for a better assessment of bone fracture risk using stiffness measured in-vivo.

8th World Congress of Biomechanics, DUBLIN, IRLANDE, 08-/07/2018 - 08/07/2018; Osteoporosis remains today a major health problem. Cortical bone fracture mechanisms are well documented under quasi - static loading condition. However the influence of strain rate on fracture needs to be better understood as bone fractures mainly occur after a fall from a standing height. The fracture process in human cortical bone is complex, and involves the overall organization of the tissue. Previous results showed that the whole porosity network, from the Haversian system to the lacunar network, as well as the collagen cross - links maturation, might be involved in the crack propagation mechanisms in cortical bone. Thus, the aim of the current study is to collect biomechanical, morphometric and biochemical parameters to make an overall characterization of human cortical bone crack propagation mechanisms considering two different loading conditions.

22nd Congress of the European Society of Biomechanics, SEVILLE, ESPAGNE, 02-/07/2017 - 05/07/2017; Bone mineral density (BMD) is not the sole factor accounting for the fracture risk. Fracture events encompass the initiation and growth of cracks. This makes the fracture toughness a critical aspect of bone's mechanical integrity. The novel generation of bone quantitative ultrasound devices has the ability to measure cortical bone millimeter-scale elasticity as a biomarker of bone health. While the different elastic coefficients are known to be strongly related to vascular porosity, the relationship between elasticity and toughness is poorly documented. This study aims at investigating the links between toughness, anisotropic elastic properties and vascular porosity of cortical bone assessed on the same femurs.

International audience; Cortical loss has been shown to play a key role in fracture risk [1], but it still imperfectly assessed in vivo using X-ray imaging techniques. To overcome this limitation, quantitative ultrasound guided waves are developed for their potential to probe material and structural properties of cortical bone. The purpose of this study is to assess the feasibility of estimating both cortical thickness (Ct.Th, mm) and porosity (Ct.P, %) using ultrasonic guided waves and to contrast the obtained values with reference values derived from X-ray microcomputed tomography.

25th Congress of the European Society of Biomechanics, VIENNE, AUTRICHE, 07-/07/2019 - 10/07/2019; The difficulty to predict human cortical bone fragility is partly due to its complex multiscale architecture1. In particular, osteons, considered as bone structural units arise through the remodeling process that occurs at the canals surface, and are assumed to play a major role in bone mechanical properties2. If 2D data can be found in the literature, there is, however, still few 3D quantitative data regarding bone osteonal systems3. This lack of data can be explained by the difficulty to distinguish the osteon from the interstitial tissue using standard 3D imaging techniques. However, due to its sensitivity, synchrotron radiation micro-computed tomography (SR-?CT) in the quantitative phase retrieval mode was shown to be a good candidate to enhance the contrast of the osteons4. The objective of the current study was to investigate morphometric parameters of osteons in human cortical bone and their relation with osteocyte lacunae and micro-cracks using SR quantitative phase ?CT.

12th International Congress of Vertebrate Morpholog - ICVM12-2019, PRAGUE, TCHÈQUE, RÉPUBLIQUE, 21-/07/2019 - 25/07/2019; Cortical bone plays a major role in case of fracture of long bones such as radius, femur and tibia. The mechanical properties of bones are related to their daily loadings. It is assumed that upper limbs (non-load-bearing bones) and lower limbs (load-bearing bones) in humans have different mechanical and structural properties. To have a deeper insight into the mechanical characteristics and structural features of human cortical bones, the goal of the present study was to consider paired anatomical specimens from upper and lower limbs.

Recherche en Imagerie et Technologies pour la Santé (RITS), LYON, FRANCE, 27-/03/2017 - 29/03/2017; In the world, a bone fracture due to osteoporosis occurs every 3 seconds (International Osteoporosis Foundation). Thus, it is obvious that bone fracture is a major concern. In clinics the assessment of the risk of fracture is based on the measurement of the bone mineral density (i.e. bone quantity in gram per cm²). Even if this method is currently the gold standard it is not sufficiently discriminant. Indeed, 50% of the patients having a fracture were diagnosed as non-osteoporotic (Siris et al., 2004). To overcome this limitation finite element models have been proposed. Such models can accurately predict the bone strength (e.g. (Duchemin et al., 2008; van Rietbergen and Ito, 2015) but there is no clear evidence that these models can better predict the fracture risk (van Rietbergen and Ito, 2015). Currently these models consider quasi-static loadings. However among elderly bone fractures occur during a fall. In case of a fall from a standing height people will hit the floor at an average speed of 2 m/s (Tan et al., 2006) and a corresponding strain rate of 0.1/s (Földhazy et al., 2005). We made the assumption that this loading speed should be considered in the bone loading. Bone structures (e.g. the femur or the radius) are made of two materials: cortical bone and cancellous bone. It was shown that bone strength of the femur is mainly due to the cortical bone (Holzer et al., 2009). In this context we assume that the behavior of cortical bone should be considered under a loading speed related to a fall. Thus, the goal of our current research is to assess the cortical bone toughness under a strain rate of 0.1/s, representing a fall.

Background Regulation of anoikis in human intestinal epithelial cells (IECs) implicates differentiation state-specific mechanisms. Human IECs express distinct repertoires of integrins according to their state of differentiation. Therefore, we investigated whether α2β1, α3β1, α5β1, and α6β4 integrins perform differentiation state-specific roles in the suppression of IEC anoikis. Results Human (HIEC, Caco-2/15) IECs were exposed to specific antibodies that block the binding activity of integrin subunits (α2, α3, α5, α6, β1 or β4) to verify whether or not their inhibition induced anoikis. The knockdown of α6 was also performed by shRNA. Additionally, apoptosis/anoikis was induced by pharmacological inhibition of Fak (PF573228) or Src (PP2). Anoikis/apoptosis was assayed by DNA laddering, ISEL, and/or caspase activity (CASP-8, -9, or -3). Activation levels of Fak and Src, as well as functional Fak-Src interactions, were also assessed. We report herein that differentiated IECs exhibit a greater sensitivity to anoikis than undifferentiated ones. This involves an earlier onset of anoikis when kept in suspension, as well as significantly greater contributions from β1 and β4 integrins in the suppression of anoikis in differentiated cells, and functional distinctions between β1 and β4 integrins in engaging both Fak and Src, or Src only, respectively. Likewise, Fak performs significantly greater contributions in the suppression of anoikis in differentiated cells. Additionally, we show that α2β1 and α5β1 suppress anoikis in undifferentiated cells, whereas α3β1 does so in differentiated ones. Furthermore, we provide evidence that α6β4 contributes to the suppression of anoikis in a primarily α6 subunit-dependent manner in undifferentiated cells, whereas this same integrin in differentiated cells performs significantly greater contributions in anoikis suppression than its undifferentiated state-counterpart, in addition to doing so through a dependence on both of its subunits. Conclusions Our findings indicate that the suppression of human IEC anoikis implicates differentiation state-selective repertoires of integrins, which in turn results into distinctions in anoikis regulation, and sensitivity, between undifferentiated and differentiated IECs. These data further the functional understanding of the concept that the suppression of anoikis is subjected to cell differentiation state-selective mechanisms.