Bone Response Research Articles

An effective model for cancellous bone with a viscous interstitial fluid *

We outline the mathematical model of the ultrasonic response of cancellous bone and its time harmonic formulation. In contrast to the Biot model, the fluid is not inviscid. Our fluid is viscous, but does not interact with the solid components.

Mechanosensitive miR-100 coordinates TGFβ and Wnt signaling in osteocytes during fluid shear stress.

Organism scale mechanical forces elicit cellular scale changes through coordinated regulation of multiple signaling pathways. The mechanisms by which cells integrate signaling to generate a unified biological response remains a major question in mechanobiology. For example, the mechanosensitive response of bone and other tissues requires coordinated signaling by the transforming growth factor beta (TGFβ) and Wnt pathways through mechanisms that are not well‐defined. Here we report a new microRNA‐dependent mechanism that mediates mechanosensitive crosstalk between TGFβ and Wnt signaling in osteocytes exposed to fluid shear stress (FSS). From 60 mechanosensitive microRNA (miRs) identified by small‐RNAseq, miR100 expression is suppressed by in vivo hindlimb loading in the murine tibia and by cellular scale FSS in OCY454 cells. Though FSS activates both TGFβ and Wnt signaling in osteocytes, only TGFβ represses miR‐100 expression. miR‐100, in turn, antagonizes Wnt signaling by targeting and inhibiting expression of Frizzled receptors (FZD5/FZD8). Accordingly, miR‐100 inhibition blunts FSS‐ and TGFβ‐inducible Wnt signaling. Therefore, our results identify FSS‐responsive miRNAs in osteocytes, including one that integrates the mechanosensitive function of two essential signaling pathways in the osteoanabolic response of bone to mechanical load.

Feeding intervention potentiates the effect of mechanical loading to induce new bone formation in mice.

The benefits of increased human lifespan depend upon duration of healthy, independent living; the healthspan. Bone-wasting disorders contribute significantly to loss of independence, frailty, and morbidity in older people. Therefore, there is an unmet need globally for lifestyle interventions to reduce the likelihood of bone fractures with age. Although many mechanisms are involved in disorders of bone loss, there is no single regulatory pathway and, therefore, there is no single treatment available to prevent their occurrence. Our aim in these studies was to determine whether fasting/feeding interventions alter the effect of mechanical loading on bone anabolic activities and increase bone mass. In young 17-week-old mice, 16-hour fasting period followed by reintroduction of food for 2hours increased markedly the potency of mechanical loading, that mimics the effect of exercise, to induce new cortical bone formation. Consistent with this finding, fasting and re-feeding increased the response of bone to a loading stimulus that, alone, does not stimulate new bone formation in ad-lib fed mice. Older mice (20months) experienced no potentiation of loading-induced bone formation with the same timing of feeding interventions. Interestingly, the pre-, prandial, and postprandial endocrine responses in older mice were different from those in young animals. The hormones that change in response to timing of feeding have osteogenic effects that interact with loading-mediated effects. Our findings indicate associations between timing of food ingestion and bone adaptation to loading. If translated to humans, such non-pharmacological lifestyle interventions may benefit skeletal health of humans throughout life-course and in older age.

Podoplanin is dispensable for mineralized tissue formation and maintenance in the Swiss outbred mouse background

Podoplanin, PDPN, is a mucin-type transmembrane glycoprotein widely expressed in many tissues, including lung, kidney, lymph nodes, and mineralized tissues. Its function is critical for lymphatic formation, differentiation of type I alveolar epithelial lung cells, and for bone response to biomechanical loading. It has previously been shown that Pdpn null mice die at birth due to respiratory failure emphasizing the importance of Pdpn in alveolar lung development. During the course of generation of Pdpn mutant mice, we found that most Pdpn null mice in the 129S6 and C57BL6/J mixed genetic background die at the perinatal stage, similar to previously published studies with Pdpn null mice, while all Pdpn null mice bred with Swiss outbred mice survived. Surviving mutant mice in the 129S6 and C57BL6/J mixed genetic background showed alterations in the osteocyte lacunocanalicular network, especially reduced osteocyte canaliculi in the tibial cortex with increased tibial trabecular bone. However, adult Pdpn null mice in the Swiss outbred background showed no overt differences in their osteocyte lacunocnalicular network, bone density, and no overt differences when challenged with exercise. Together, these data suggest that genetic variations present in the Swiss outbred mice compensate for the loss of function of PDPN in lung, kidney, and bone.

Development of a crushable foam model for human trabecular bone

Finite element (FE) simulations can be used to evaluate the mechanical behavior of human bone and allow for quantitative prediction of press-fit implant fixation. An adequate material model that captures post-yield behavior is essential for a realistic simulation. The crushable foam (CF) model is a constitutive model that has recently been proposed in this regard. Compression tests under uniaxial and confined loading conditions were performed on 59 human trabecular bone specimens. Three essential material parameters were obtained as a function of bone mineral density (BMD) to develop the isotropic CF model. The related constitutive rule was implemented in FE models and the results were compared to the experimental data. The CF model provided an accurate simulation of uniaxial compression tests and the post-yield behavior of the stress-strain was well-matched with the experimental results. The model was able to reproduce the confined response of the bone up to 15% of strain. This model allows for simulation of the mechanical behavior of the cellular structure of human bone and adequately predicts the post-yield response of trabecular bone, particularly under uniaxial loading conditions. The model can be further improved to simulate bone collapse due to local overload around orthopaedic implants.

Comparison of Bone Levels Around Immediately Loaded Single Implants Placed in Healed or Freshly Extracted Sites in the Esthetic Anterior Maxilla: A 10-Year Prospective Study.

To evaluate retrospectively at 10 years the marginal bone levels around implants located in healed ridges or in extraction sockets and loaded immediately with provisional crowns fixed in prefabricated abutments. Forty-two implants were placed in 36 patients needing single tooth replacement. Implants were inserted either in healed ridges (group 1) or in extraction sockets (group 2) and loaded immediately with prefabricated abutments. Two implants were lost during the healing period from group 2. The bone level around the implant shoulder was calculated mesially and distally on each implant using intraoral radiographs after crown cementation and 1, 3, 5, and 10 years following loading. On the 10-year follow-up report, 36 implants were available for the clinical and radiologic evaluation. Besides the two implants lost during the osseointegration period, no implant loss was documented over the 5- to 10-year observation period. The average bone loss after implant and crown cementation was 0.266 ± 0.176 mm for 1 year, 0.194 ± 0.172 mm for 5 years, and 0.198 ± 0.165 mm for 10 years in healed ridges and 0.267 ± 0.161 mm for 1 year, 0.213 ± 0.185 mm for 5 years, and 0.287 ± 0.194 mm for 10 years in extraction sockets. Three crowns (in group 1) and one crown (in group 2) were replaced for esthetic reasons. The outcome of this study revealed that in both groups, the responses of marginal bone were similar. Immediate placement of the definitive prefabricated abutment in an immediate loading protocol appears to conserve marginal bone around the implant neck.

Predicting bone remodeling using a mechano-biological mathematical model combined with a natural neighbor meshless method

Bone tissue perceives certain mechanical stimuli, adapting its structure to a loading scenario through bone remodeling. Thanks to this ability, bone's functions of support and protection are assured. The mechanical response of bone is computationally reproduced in this work with a new bone remodeling model. Through a mechanobiological approach, the model includes two types of bone cells (i.e. osteoclasts and osteoblasts), describing its functioning and interaction with new sets of parameters. Mechanical stimulation induces a response by bone cells that ultimately is translated into variations of bone's apparent density and other mechanical properties by applying a material phenomenological law. The new algorithm here proposed is for the first time combined with an estabilished meshless method (Natural Neighbor Radial Point Interpolation Method), taking advantage of its features for biomedical applications. As a preliminary study, a two-dimensional bone patch is analyzed. A first study is performed to find the best parameters of NNRPIM for this type of simulation. Then, starting from a uniform bone distribution, a well-defined loading regime is imposed to the bone patch. Results revealed the expected bone adaption, attaining an optimized trabecular structure that reflects the orientation of the applied loads.

Sclerostin and bone turnover markers response to cycling and running at the same moderate-to-vigorous exercise intensity in healthy men.

Recreational cycling is a popular activity which stimulates and improves cardiovascular fitness. The corresponding benefits for bone are unclear. This study examined the effect of running (high-impact) vs. cycling (low-impact), at the same moderate-to-vigorous exercise intensity, on markers of bone formation (N-terminal propeptide of type I collagen, PINP) and bone resorption (C-telopeptide of type I collagen, CTX-1), a non-collagenous bone remodeling marker (osteocalcin), as well as bone-modulating factors, including parathyroid hormone (PTH), irisin (myokine) and sclerostin (osteokine). Thirteen healthy men (23.7 ± 1.0 y) performed two progressive exercise tests to exhaustion (peak VO2) on a cycle ergometer (CE) and on a treadmill (TM). On subsequent separate days, in randomized order, participants performed 30-min continuous running or cycling at 70% heart rate reserve (HRR). Blood was drawn before, immediately post- and 1 h into recovery. PTH transiently increased (CE, 51.7%; TM, 50.6%) immediately after exercise in both exercise modes. Sclerostin levels increased following running only (27.7%). Irisin increased following both running and cycling. In both exercise modes, CTX-1 decreased immediately after exercise, with no significant change in PINP and osteocalcin. At the same moderate-to-vigorous exercise intensity, running appears to result in a greater transient sclerostin response compared with cycling, while the responses of bone markers, PTH and irisin are similar. The longer-term implications of this differential bone response need to be further examined.

Gender-Related Impact of Sclerostin Antibody on Bone in the Osteogenesis Imperfecta Mouse.

Osteogenesis imperfecta (OI), which is most often due to a collagen type 1 gene mutation, is characterized by low bone density and bone fragility. In OI patients, gender-related differences were reported, but data in the literature are not convergent. We previously observed that sclerostin antibody (Scl-Ab), which stimulates osteoblast Wnt pathway via sclerostin inactivation, improved spine and long-bone parameters and biomechanical strength in female oim/oim mice, a validated model of human type 3 OI. Here, we wanted to highlight the effect of Scl-Ab on male oim/oim bones in order to identify a possible distinct therapeutic effect from that observed in females. According to the same protocol as our previous study with female mice, male wild-type (Wt) and oim/oim mice received vehicle or Scl-Ab from 5 to 14 weeks of age. Clinimetric and quantitative bone parameters were studied using X-rays, peripheral quantitative computed tomography, microradiography, and dynamic histomorphometry and compared to those of females. Contrary to Wt mice, male oim/oim had significantly lower weight, snout–sacrum length, and bone mineral content than females at 5 weeks. No significant difference in these clinimetric parameters was observed at 14 weeks, whereas male oim showed significantly more long-bone fractures than females. Scl-Ab improved bone mineral density and bone volume/total volume ratio (BV/TV) of vertebral body in Wt and oim/oim, without significant difference between male and female at 14 weeks. Male vehicle oim/oim had a significantly lower cortical thickness (Ct.Th) and BV/TV of tibial diaphysis than female and showed a higher number of fractures at 14 weeks. Scl-Ab increased midshaft periosteal apposition rate in such a way that tibial Ct.Th of male oim/oim was not significantly different from the female one at 14 weeks. The number of fractures was lower in male than female oim/oim after 14 weeks of Scl-Ab treatment, but this difference was not significant. Nevertheless, Scl-Ab–treated oim/oim male and female mice remained smaller than the Wt ones. In conclusion, our results highlighted differences between male and female oim/oim at 4 and 14 weeks of age, as well as some male-specific response of cortical bone to Scl-Ab. These gender-related particularities of oim/oim should be considered when testing experimental treatments.

Anatomical variation in intracortical canal network microarchitecture and its influence on bone fracture risk

Intracortical canals are a major contributor to cortical bone porosity and influence its mechanical response. Canal networks act as stress concentrators and the magnitude of which depends on the size and spatial distribution of canals. In the present study, we investigated site-dependent variation in intracortical canal network morphological indices and their effect on the mechanical response of bone. For this, mid-diaphysis of rat tibia bones were scanned using high-resolution micro-CT and morphological indices were measured for four main anatomical sites-anterior, posterior, medial and lateral. Further, a micro-finite element (μFE) model was developed to quantify the stress concentration regions in different cortices. The fracture risk was assessed using an effective strain approach. Results show that canal porosity, canal orientation and canal length are site-dependent whereas canal diameter and canal number density are independent of the site. The lateral cortex has significantly higher porosity compared to the posterior cortex (p < 0.05). The orientation of canals is found significantly different between endosteal and periosteal regions for anterior and medial quadrants. Canals are inclined at higher angles with bone axis in the endosteal region as compare to the periosteal region. The μ-FE results show that the regions with higher effective strain are concentrated around the canals. Further, failed element volume per unit bone volume is found highest for medial cortex whereas lowest for posterior cortex. The higher failed volume is associated with more radial canals in the medial cortex as compare to other cortices. The linear regression analysis shows that the volume of overstrained elements strongly depends on canal orientation (R2 = 0.73, p < 0.0001) and canal porosity (R2 = 0.61, p < 0.0001). The findings from this study suggest that along with vascular canal porosity, canal orientation and canal diameter can further improve the bone fracture risk assessment.

Identification of Bone Density Changes Applying Impedance Spectroscopy with a Piezo-Device Coupled to a Human Tooth

Bone tissue is a calcium deposit and supporting structure of the human body, it is exposed to several pathologies that modify its mineral content. To determine these changes, different diagnostic procedures are performed with techniques using invasive ionizing radiation, which are limited by the negative effects in the long term on human health. A methodology is explored that could be applicable in the diagnosis of pathologic variations in bone mineral density, using structural monitoring tools. The proposed technique estimates changes in bone conditions by applying impedance spectroscopy with a tooth-borne piezo-device. Bone-tooth samples were prepared to simulate a section of maxillary bone and subsequently treated with chemical agents, simulating pathologic decalcification. The piezo-device is inserted in the slot of an orthodontic bracket, previously bonded to the crown of the tooth, in order to transmit vibration to surrounding bone. The variations in bone micro-architecture were computed by image processing analyzed with samples prepared in transparent resin, allowing the measurement of morphometry before and after the induced changes in mineral content. Using vibrational bone response, impedance measurements allowed to observe the variations in bone mass as the samples were progressively decalcified. In the 5-50kHz spectrum, it was demonstrated the sensitivity of the electro-mechanical impedance during the bone alteration procedure since the electrical resistance signals of the piezo-device consistently changed in the frequency spectrum (5-50kHz). The piezo-device shows to be sensitive to the changes produced by the bone alterations, which were caused by the stiffness variations made in the sample during the decalcifying. These changes were statistically correlated to demonstrate that in a less invasive way, bone alterations could be monitored from the teeth. This result opens the door to search for a new way to diagnose bone density changes in real applications.

Bone responsiveness to parathyroid hormone is negatively associated with parathyroid hormone-lowering drug use in patients undergoing hemodialysis: a cross-sectional study

BackgroundParathyroid hormone (PTH) acts on bone to indirectly increase the number and activity of osteoclasts. Thus, PTH has a stimulatory effect on bone resorption and upregulates bone turnover. However, the responsiveness of bone to PTH varies widely among patients receiving dialysis. In fact, relative to the serum PTH level, the level of serum tartrate-resistant acid phosphatase-5b (TRACP-5b), a bone resorption marker derived from osteoclasts, varies as well. This study aimed to examine factors related to bone responsiveness to PTH in patients undergoing chronic hemodialysis (HD).MethodsThis study included patients receiving chronic HD in Kawasaki Municipal Tama Hospital (Kanagawa, Japan) and Yonaha Medical Clinic (Okinawa, Japan) and excluded patients who received HD for less than 6 months, those who received a combination of HD and peritoneal dialysis, and those who had cancer bone metastases or myeloma. The TRACP-5b/intact PTH (iPTH) ratio was created as an index of bone responsiveness to PTH, categorized into tertiles (low, medium, and high), and a cross-sectional study was conducted. P < 0.05 indicated statistically significant differences.ResultsOne hundred and six patients were analyzed. Age (P = 0.010), body mass index (BMI) (P = 0.003), use of calcium-sensing receptor (CaSR) agonists (P = 0.008), use of vitamin D receptor activators (VDRAs) (P = 0.012), plasma iPTH level (P < 0.001), serum 1,25(OH)2D level (P = 0.003), and serum TRACP-5b level (P < 0.001) were significantly different among the three categories. In the single linear regression analysis, age (P = 0.016), corrected serum calcium level (P = 0.007), and ln [1,25(OH)2D] (P = 0.044) showed a significant positive correlation with ln [TRACP-5b/iPTH], whereas BMI (P = 0.026), use of CaSR agonists (P = 0.001), use of VDRAs (P = 0.009), and serum phosphorus level (P = 0.018) showed a significant negative correlation. Upon conducting multiple linear regression analysis incorporating significant variables in the single linear regression analysis, a significant negative correlation was observed between the TRACP-5b/iPTH ratio and intravenous administration of a CaSR agonist (etelcalcetide) and/or a VDRA (calcitriol or maxacalcitol) in all the adjusted models.ConclusionsBone responsiveness to PTH is negatively correlated with the intravenous administration of a CaSR agonist and/or a VDRA in patients undergoing chronic HD.

Osseointegration of Sandblasted and Acid-Etched Implant Surfaces. A Histological and Histomorphometric Study in the Rabbit.

Titanium surface is an important factor in achieving osseointegration during the early wound healing of dental implants in alveolar bone. The purpose of this study was to evaluate sandblasted-etched surface implants to investigate the osseointegration. In the present study, we used two different types of sandblasted-etched surface implants, an SLA™ surface and a Nanoblast Plus™ surface. Roughness and chemical composition were evaluated by a white light interferometer microscope and X-ray photoelectron spectroscopy, respectively. The SLA™ surface exhibited the higher values (Ra 3.05 μm) of rugosity compared to the Nanoblast Plus™ surface (Ra 1.78 μm). Both types of implants were inserted in the femoral condyles of ten New Zealand white rabbits. After 12 weeks, histological and histomorphometric analysis was performed. All the implants were osseointegrated and no signs of infection were observed. Histomorphometric analysis revealed that the bone–implant contact % (BIC) ratio was similar around the SLA™ implants (63.74 ± 13.61) than around the Nanoblast Plus™ implants (62.83 ± 9.91). Both implant surfaces demonstrated a favorable bone response, confirming the relevance of the sandblasted-etched surface on implant osseointegration.

Bone Response to Conventional Titanium Implants and New Zirconia Implants Produced by Additive Manufacturing.

The aim of the present study was to evaluate the in vivo bone response to an additively manufactured zirconia surface compared to osseointegration into titanium (Ti) surfaces. Scanning electron microscopy, confocal laser scanning microscopy, and electron spectroscopy for chemical analysis were performed to assess the surface characteristics of implant specimens. For the in vivo evaluation, eight Ti implants and eight 3D-printed zirconia implants were used. The surface of four Ti implants was sandblasted, large-grit, and acid-etched (Ti-SLA group), while those of the other four Ti implants were left untreated (Ti-turned group). The zirconia implants had no further surface modification. Implants were placed into the tibiae of four rabbits; two received the Ti-SLA and zirconia implants and the other two received Ti-turned and zirconia implants. The experimental animals were sacrificed after four weeks of surgery, and the undecalcified microscopic slides were prepared. The bone–implant interface was analyzed by histomorphometry to evaluate the bone response. The degree of surface roughness showed that Ti-SLA was the highest, followed by zirconia and Ti-turned surfaces. The 3D-printed zirconia surface showed similar bone-to-implant contact to the Ti-turned surface, and Ti-SLA had the most bone-to-implant contact. The additively manufactured zirconia implant surface is biocompatible with respect to osseointegration compared to the commercially pure Ti surface.

Comparative Evaluation of Two Glass Polyalkenoate Cements: An In Vivo Pilot Study Using a Sheep Model.

Poly(methyl methacrylate) (PMMA) is used to manage bone loss in revision total knee arthroplasty (rTKA). However, the application of PMMA has been associated with complications such as volumetric shrinkage, necrosis, wear debris, and loosening. Glass polyalkenoate cements (GPCs) have potential bone cementation applications. Unlike PMMA, GPC does not undergo volumetric shrinkage, adheres chemically to bone, and does not undergo an exothermic setting reaction. In this study, two different compositions of GPCs (GPCA and GPCB), based on the patented glass system SiO2-CaO-SrO-P2O5-Ta2O5, were investigated. Working and setting times, pH, ion release, compressive strength, and cytotoxicity of each composition were assessed, and based on the results of these tests, three sets of samples from GPCA were implanted into the distal femur and proximal tibia of three sheep (alongside PMMA as control). Clinical CT scans and micro-CT images obtained at 0, 6, and 12 weeks revealed the varied radiological responses of sheep bone to GPCA. One GPCA sample (implanted in the sheep for 12 weeks) was characterized with no bone resorption. Furthermore, a continuous bone–cement interface was observed in the CT images of this sample. The other implanted GPCA showed a thin radiolucent border at six weeks, indicating some bone resorption occurred. The third sample showed extensive bone resorption at both six and 12 weeks. Possible speculative factors that might be involved in the varied response can be: excessive Zn2+ ion release, low pH, mixing variability, and difficulty in inserting the samples into different parts of the sheep bone.

The Role of Biomaterials and Biocompatible Materials in Implant-Supported Dental Prosthesis.

The dental implant is one of the appropriate instances of the different dental materials and their application, which is the combined procedure of technology and science in physics, biomechanics, and surface chemistry from macroscale to nanoscale surface engineering and manufactured technologies. In recent decades, biomaterials in implant therapy promote bone response and biomechanical ability, which is long-term from surgical equipment to final prosthetic restoration. Biomaterials have a crucial role in rehabilitating the damaged structure of the tooth and supplying acceptable outcomes correlated with clinical performance. There are some challenges in implantation such as bleeding, mobility, peri-implant infections, and the solution associated with modern strategies which are regarded to biomaterials. Various materials have been known as promising candidates for coatings of dental implants which contain polyhydroxyalkanoates, calcium phosphate, carbon, bisphosphonates, hydroxyapatite, bone stimulating factors, bioactive glass, bioactive ceramics, collagen, chitosan, metal and their alloys, fluoride, and titanium/titanium nitride. It is pivotal that biomaterials should be biodegradable; for example, polyhydroxyalkanoates are biodegradable; also, they do not have bad effects on tissues and cells. Despite this, biomaterials have important roles in prosthetic conditions such as dental pulp regeneration, the healing process, and antibacterial and anti-inflammatory effects. In this review study, the role of biocompatible materials in dental implants is investigated in in vitro and in vivo studies.

Association Between DXA And HR-pQCT Measurements Of BMD In Active, Recruit-aged Men And Women

Dual-energy X-ray absorptiometry (DXA) areal bone mineral density (aBMD) measurements are routinely employed to assess fracture risk despite the limitations of a two-dimensional, estimated projection of bone volume. Conversely, high-resolution peripheral quantitative computed tomography (HR-pQCT) provides three-dimensional volumetric BMD (vBMD) measurements of total, trabecular, and cortical bone, offering better characterization of fracture risk. It remains unclear whether regional aBMD accurately reflects vBMD of specific bone compartments in the distal tibia, a common injury site for military personnel. PURPOSE: To determine if lower limb aBMD correlates with distal total (Tt), trabecular (Tb) and cortical (Ct) vBMD in healthy, recruit-aged men and women. METHODS: Seventy-six recreationally active men (n = 43;26.4 ± 0.8 yrs.), and women (n = 33;26.2 ± 4.7 yrs.), free of any musculoskeletal conditions that could influence BMD, completed two HR-pQCT (XtremeCT; Scanco Medical) and one total body DXA (Lunar iDXA; GE Healthcare) scans. Total body DXA and non-dominant tibial HR-pQCT scans at the metaphysis (4% site) and diaphysis (30% site) were obtained. Lower leg aBMD was assessed in DXA scans with custom region of interest (ROI) analysis between the ultradistal tibia and the tibial plateau. Associations between variables were analyzed with Pearson’s correlation coefficient (r2); alpha was set at p < 0.05. RESULTS: aBMD positively correlated with Tt vBMD at the 4% site for men (r2 = 0.42; p < 0.001) and women (r2 = 0.17; p = 0.016) but only in men at the 30% site (r2 = 0.16; p = 0.008). aBMD positively correlated with Tb vBMD at the 4% site for men (r2 = 0.35; p < 0.001) and women (r2 = 0.20; p = 0.010), but not at the 30% site for either sex. aBMD was not correlated with Ct vBMD at the 4% site for either sex but was positively correlated with Ct vBMD at the 30% site in men (r2 = 0.12; p = 0.032). CONCLUSIONS: There is poor to moderate association between lower limb aBMD and tibial vBMD at both sites, with greater association in men than in women. aBMD is unlikely to provide a suitable assessment of distal tibial bone health. aBMD and tibial vBMD should, therefore, not be used interchangeably to examine the bone response to interventions or for the prediction of fracture risk. Supported by UK Ministry of Defence (WGCC 5.5.6-Task 0107).

Corrosion behaviour of hydroxyapatite (HAP) coated AISI 316Ti austenitic biomaterial

HAP bioactive coatings are widely applied to improve the bone response in orthopedic and dental stainless steels implants. Mechanical properties of the metallic implant are preserved and moreover, HAP improves the corrosion resistance. This article deals with the corrosion resistance of AISI 316Ti austenitic biomaterial with electrochemically deposited HAP coating. Corrosion behaviour is evaluated on the bases of two independent methods-the electrochemical potentiodynamic polarization test and exposure immersion tests, both carried out in physiological solution (0.9 % NaCl) at the temperature 37 ± 0.5 °C. The microstructure and chemical composition of HAP coating is evaluated by SEM and EDX analysis. According to the results of the potentiodynamic test, the HAP coated biomaterial shows the considerably higher corrosion resistance compared to that without the HAP coating. However, the corrosion losses and SEM analysis after the exposure test revealed severe disruption of the HAP coating and the stainless steel substrate started to corrode.

Six-weeks Of Resistance Training Is Not Sufficient To Stimulate Bone Response In Older Adults

Aging presents a variety of challenges, ranging from loss of muscle mass, strength, and bone density to functional impairment, risk of fall and fracture. Resistance exercise is known to load the bone and enhance bone density and subsequently strength. However these adaptation typically occur over a long period of time (6+ months). PURPOSE: The purpose of this study was to evaluate whether either dumbbell or elastic band resistance training are beneficial in bone morphology of older adults over 6 weeks of training or a control period. METHODS: Fifty-seven males and females (mean ± SD; age = 66.5 ± 7.09 yrs; height = 165.2 ± 10.6 cm; body mass = 74.5 ± 14.6 kg) volunteered to participate in this study. Participants underwent a total body dual-energy x-ray absorptiometry (DXA) scan for segmental and total body bone mineral content (BMC) and bone mineral density (BMD). Participants were block randomized into one of three groups: elastic band resistance training (EBRT; n = 24), dumbbell resistance training (DBRT; n = 21), or control (CON; n = 12). EBRT and DBRT were asked to visit the laboratory twice weekly over 6-weeks while CON maintained their daily routine. Three-day dietary recalls were collected to ensure dietary maintenance throughout the intervention period. Data were analyzed using a two-way (time x treatment) repeated measures ANOVA and an alpha pre-determined at 0.05. RESULTS: Results indicated there was no two-way interaction for total body BMC (p = 0.164) nor was there a main effect for time (p = 0.39) or group (p = 0.40). Likewise, total body BMD indicated no 2-way interaction (p = 0.79) and no main effect for time (p = 0.753). However, there was a main effect for group where collapsed across time, DBRT had a higher BMD than CON (p = 0.05), but no other differences were observed. CONCLUSIONS: These data suggest that either the load provided throughout the training from DBRT and EBRT to stimulate change in bone over 6-weeks was insufficient or the duration was not long enough. Most previous research supports the latter as bone remodeling occurs in a throughout 4-8 month periods. Other factors that may impact the outcome of the stimuli include exogenous pharmacological treatment for bone loss and dietary factors.

Chitosan/hydroxyapatite nanocomposite scaffolds to modulate osteogenic and inflammatory response.

ABSTRACTConsiderable attention has been given to the use of chitosan (CS)‐based materials reinforced with inorganic bioactive signals such as hydroxyapatite (HA) to treat bone defects and tissue loss. It is well known that CS/HA based materials possess minimal foreign body reactions, good biocompatibility, controlled biodegradability and antibacterial property. Herein, the bioactivity of these composite systems was analyzed on in vitro bone cell models for their applications in the field of bone tissue engineering (BTE). The combination of sol–gel approach and freeze‐drying technology was used to obtain CS/HA scaffolds with three‐dimensional (3D) porous structure suitable for cell in‐growth. Specifically, our aim was to investigate the influence of bioactive composite scaffolds on cellular behavior in terms of osteoinductivity and anti‐inflammatory effects for treating bone defects. The results obtained have demonstrated that by increasing inorganic component concentration, CS/HA (60 and 70% v/v) scaffolds induced a good biological response in terms of osteogenic differentiation of human mesenchymal stem cells (hMSC) towards osteoblast phenotype. Furthermore, the scaffolds with higher concentration of inorganic fillers are able to modulate the production of pro‐inflammatory (TGF‐β) and anti‐inflammatory (IL‐4, IL‐10) cytokines. Our results highlight the possibility of achieving smart CS/HA based composites able to promote a great osteogenic differentiation of hMSC by increasing the amount of HA nanoparticles used as bioactive inorganic signal. Contemporarily, these materials allow avoiding the induction of a pro‐inflammatory response in bone implant site.