Mineralized Tissue Changes Within the Anterior Cruciate Ligament Entheses Following a Tear

Background: Thirty-percent of patients under 20 years of age suffer a primary ACL graft failure. Young patients show significant bone loss at the femoral ACL-bone insertion site (enthesis). We hypothesize that active bone resorption during ACL graft fixation contributes to poor graft survival in the young. We investigated distal femoral and entheseal bone morphology changes after injury in a novel mouse model to determine if previously reported post-injury patient condition anti-translates to the mouse. Confirmation of a similar condition across species will allow us to use this model to spatially and temporally track physiologic processes within this critical region. Methods: We induced an in vivo ACL rupture in 24 10-week C57BL/6J female mice and sacrificed them at 7 and 28 post-injury. Both loaded ipsilateral and non-loaded contralateral knees were 3D imaged and distal femoral and ACL entheseal cortical regions have begun being analyzed. Traits analyzed include 1) cortical (Ct.) mean gray-value density, area (Ar.), thickness (Th.), and bone volume fraction (BV/TV) Statistics: two-way ANOVA and Tukey posthoc. Results: So far, mice are temporally demonstrating bone differences between injured and non-injured knees similar to that of patients at the time of ACL reconstructive surgery. By 7 days there is a steep decline in whole distal femoral epiphysis and ACL femoral entheseal Ct.Ar (-19.84% and -11.46%, respectively) and Ct.Th (-8.09% and -3.52%, respectively). The trend in Ct.Ar loss holds at 28 days (-40.95% and -8.32%, respectively), but not in Ct.Th, which substantially increases (6.26% and 11.05%, respectively). Conclusion: It appears bone loss is rapid following injury, and that by 28 days there is increased porosity within the cortex with new periosteal/endosteal bone formation counteracting this. If true, particularly within the entheseal region, this may prove problematic for long-term graft outcomes when surgery is performed at the time of significant macrophagic activity.

The Balance between Orthodontic Force and Radiation in the Jawbone: Microstructural, Histological, and Molecular Study in a Rat Model

Irradiation of facial bones is associated with a lifelong risk of osteonecrosis. In a rat model, maxillae were exposed to a single 5 Gy dose of external beam radiation and orthodontic force was applied for 2 weeks on the first maxillary molar; control rats were treated identically without radiation. Tooth movement in irradiated jaws was 30% less than in controls, representing radiation-related damage. Micro-CT, histological, and molecular outcomes of orthodontic tooth movement were studied. Microstructurally, bone parameters (trabecular thickness, bone volume fraction, bone mineral density) were significantly affected by orthodontic force but not by radiation. Histological parameters were influenced only by orthodontic force, especially by an increase in osteoclasts. A molecular study revealed a differential distribution of cells expressing pre-osteoclast markers (RANK+—majority, CD11b+, CD14+—minority), with changes being influenced by orthodontic force (increased CD11b+ and CD14+ cells) and also by radiation (decreased RANK+ cells). The activation status of osteoclasts (TRAP staining) showed an orthodontic-force-related increase, which probably could not fully compensate for the radiation-associated impairment. The overall balance showed that orthodontic force had elicited a substantial microstructural, histological, and functional normalization process in irradiated maxillae but a radiation-induced impact was still conspicuous. Additional studies are needed to validate these findings.

Generation of Vertebra Micro-CT-like Image from MDCT: A Deep-Learning-Based Image Enhancement Approach

This paper proposes a deep-learning-based image enhancement approach that can generate high-resolution micro-CT-like images from multidetector computed tomography (MDCT). A total of 12,500 MDCT and micro-CT image pairs were obtained from 25 vertebral specimens. Then, a pix2pixHD model was trained and evaluated using the structural similarity index measure (SSIM) and Fréchet inception distance (FID). We performed subjective assessments of the micro-CT-like images based on five aspects. Micro-CT and micro-CT-like image-derived trabecular bone microstructures were compared, and the underlying correlations were analyzed. The results showed that the pix2pixHD method (SSIM, 0.804 ± 0.037 and FID, 43.598 ± 9.108) outperformed the two control methods (pix2pix and CRN) in enhancing MDCT images (p < 0.05). According to the subjective assessment, the pix2pixHD-derived micro-CT-like images showed no significant difference from the micro-CT images in terms of contrast and shadow (p > 0.05) but demonstrated slightly lower noise, sharpness and trabecular bone texture (p < 0.05). Compared with the trabecular microstructure parameters of micro-CT images, those of pix2pixHD-derived micro-CT-like images showed no significant differences in bone volume fraction (BV/TV) (p > 0.05) and significant correlations in trabecular thickness (Tb.Th) and trabecular spacing (Tb.Sp) (Tb.Th, R = 0.90, p < 0.05; Tb.Sp, R = 0.88, p < 0.05). The proposed method can enhance the resolution of MDCT and obtain micro-CT-like images, which may provide new diagnostic criteria and a predictive basis for osteoporosis and related fractures.

Osteocyte Apoptosis Contributes to Cold Exposure-induced Bone Loss

Emerging evidence indicates that bone mass is regulated by systemic energy balance. Temperature variations have profound effects on energy metabolism in animals, which will affect bone remodeling. But the mechanism remains unclear. 2-month-old C57BL/6J male mice were exposed to cold (4°C) and normal (23°C) temperatures for 28 days and the effects of cold exposure on bone mass was investigated. Micro-computed tomography results showed that bone volume fraction was significantly reduced after 14 days of exposure to cold temperature, and it was recovered after 28 days. Ploton silver staining and immunohistochemical results further revealed that exposure to cold decreased canalicular length, number of E11-and MMP13-positive osteocytes after 14 days, but they returned to the baseline levels after 28 days, different from the normal temperature control group. In addition, change of Caspase-3 indicated that exposure to cold temperature augmented apoptosis of osteocytes. In vitro results confirmed the positive effect of brown adipocytes on osteocyte‘s dendrites and E11 expression. In conclusion, our findings indicate that cold exposure can influence bone mass in a time-dependent manner, with bone mass decreasing and recovering at 2 and 4 weeks respectively. The change of bone mass may be caused by the apoptosis osteocytes. Brown adipocyte tissue could influence bone remodeling through affecting osteocyte.

Bone Remodeling Model Integrating the Biological Function and Damage Influences for the Cortical-Trabecular Interface

Bone remodeling process has been widely investigated in literature from an experimental and theoretical viewpoint. Indeed, the biological process of bone remodeling allows a continuous renewal of the microstructure over time and thus, it contributes to decrease the bone damage by repairing it. This research work aims to study the biological function’s (fbio) effects on the bone remodeling process trough bone density evolution. Parameter fbio is one of the important parameters that controls bone volume variation. The biological bone remodeling process is modeled in terms of equations describing the activity of the Basic Multi-cellular Units (BMU). We use a mathematical model to simulate damage repair, based on Garcia Aznar’s model. The results of simulation show a good match with experimental and clinical data: bone porosity decreases over time and decreases also as the biological factors increase. In the same view, the apparent density (ρa) decreases with bone volume fraction increases. We note that the governance of the evolution of bone density leads to consider the evolution of bone volume during youthful and the maturation phase with their saturation zone for adult in terms of growth.

Novel Preosteoclast Populations in Obesity-Associated Periodontal Disease

Although there is a clear relationship between the degree of obesity and periodontal disease incidence, the mechanisms that underpin the links between these conditions are not completely understood. Understanding that myeloid-derived suppressor cells (MDSCs) are expanded during obesity and operate in a context-defined manner, we addressed the potential role of MDSCs to contribute toward obesity-associated periodontal disease. Flow cytometry revealed that in the spleen of mice fed a high-fat diet (HFD), expansion in monocytic MDSCs (M-MDSCs) significantly increased when compared with mice fed a low-fat diet (LFD). In the osteoclast differentiation assay, M-MDSCs isolated from the bone marrow of HFD-fed mice showed a larger number and area of osteoclasts with a greater number of nuclei. In the M-MDSCs of HFD-fed mice, several osteoclast-related genes were significantly elevated when compared with LFD-fed mice according to a focused transcriptomic platform. In experimental periodontitis, the number and percentage of M-MDSCs were greater, with a significantly larger increase in HFD-fed mice versus LFD-fed mice. In the spleen, the percentage of M-MDSCs was significantly higher in HFD-fed periodontitis-induced (PI) mice than in LFD-PI mice. Alveolar bone volume fraction was significantly reduced in experimental periodontitis and was further decreased in HFD-PI mice as compared with LFD-PI mice. The inflammation score was significantly higher in HFD-PI mice versus LFD-PI mice, with a concomitant increase in TRAP staining for osteoclast number and area in HFD-PI mice over LFD-PI mice. These data support the concept that M-MDSC expansion during obesity to become osteoclasts during periodontitis is related to increased alveolar bone destruction, providing a more detailed mechanistic appreciation of the interconnection between obesity and periodontitis.

Growth and development of trabecular structure in the calcaneus of Japanese macaques (Macaca fuscata) reflects locomotor behavior, life-history, and neuromuscular development.

We aim to broaden the analysis of bone structure by suggesting a new way to incorporate the interactions between behavior, neuromuscular development, and life-history. We examine the associations between these variables and age-related variation in trabecular structure in the calcaneus of Japanese macaques (Macaca fuscata). If skeletal markers linking these variables can be established, our inferences of the biology and behavior of fossil species would be significantly improved. We μCT scanned the calcaneus in a cross-sectional sample of 36 juveniles aged between 0 and 7 years old and 5 adults at the Primate Research Institute, Japan. We calculated whole bone averages of standard trabecular properties and generated whole-bone morphometric maps of bone volume fraction and Youngs modulus. Trabecular structure is increasingly heterogeneous in older individuals. BV/TV decreases during the first month of life and increases afterwards, coinciding with the onset of independent locomotion. At birth, primary Youngs modulus is oriented orthogonal to the ossification center, but after locomotor onset bone structure becomes stiffest in the direction of joint surfaces and muscle attachments. Age-related variation in bone volume fraction is best predicted by an interaction between neuromaturation, body mass, and locomotor independence. Results support the common assumption that trabecular structure dynamically adapts to novel joint loading conditions during ontogeny. The timing of independent locomotion, body size, and neuromuscular development, are all correlated to age-related variation in the trabecular structure of the macaque calcaneus. The causal mechanisms behind the observed patterns cannot be directly inferred from our cross-sectional study. If the model presented in this paper holds up under longitudinal experimental conditions, trabecular structure can be used both to infer behavior from fossil morphology and to serve as a valuable proxy for neuromuscular maturation and life history events like locomotor onset and the achievement of an adult-like gait.

Pancreas deficiency modifies bone development in the ovine fetus near term

Hormones have an important role in the regulation of fetal growth and development, especially in response to nutrient availability in utero. Using micro-computed tomography and an electromagnetic 3-point bend test, this study examined the effect of pancreas removal at 0.8 fraction of gestation on the developing bone structure and mechanical strength in fetal sheep. When fetuses were studied at 10 and 25 days after surgery, pancreatectomy caused hypoinsulinaemia, hyperglycaemia and growth retardation which was associated with low plasma concentrations of leptin and a marker of osteoclast activity and collagen degradation. In pancreatectomised fetuses compared to control fetuses, limb lengths were shorter and trabecular bone in the metatarsi showed greater bone volume fraction, trabecular thickness, degree of anisotropy and porosity, and lower fractional bone surface area and trabecular spacing. Mechanical strength testing showed that pancreas deficiency was associated with increased stiffness and a greater maximal weight load at fracture in a subset of fetuses studied near term. Overall, pancreas deficiency in utero slowed growth of the fetal skeleton and adapted the developing bone to generate a more compact and connected structure. Maintenance of bone strength in growth-retarded limbs is especially important in a precocial species in preparation for skeletal loading and locomotion at birth.

Effect of Curcumin on Alterations of Alveolar Bone Remodeling and Expression of Receptor Activator of Nuclear Factor-κ B Ligand in Rat Tooth During Tooth Movement

Objective: To evaluate the effect of Curcumin on Alterations of Alveolar Bone Remodeling and Expression of RANKL in Rat Tooth during Tooth Movement. Methods: 64 SD rats were randomly divided into 4 groups, Model, Adrb2, Cur and Cur + Pro groups. The rat orthodontic teeth movement models were established.The rats were injected corresponding reagents according to weight and were sacrificed on day 0, 7, 14 and 21. The movement distance of first molar of rats was measured by Vernier caliper.The numbers of osteoclasts were observed through TRAP staining. The change of micro-structure of alveolar bone was evaluated by Micro-CT. Results: The trends of the distance of teeth movement and numbers of osteoclast were the same: Cur group β Adrb2 group > Model groups Cur+Pro group (P < 0.05). Micro-CT scan showed that curcumin could reduce the bone volume fraction (BV/TV), bone trabecular density (MTPD), and increase the trabecular resolution (TB. SP). When propranolol was given at the same time, the effect of curcumin disappeared. Conclusion: Curcumin could promote the resorption of alveolar bone at the pressure side and increase the osteoclast numbers so that the alveolar bone became looser which was beneficial to the movement of orthodontic tooth.

Study on the Mechanism of Qigu Capsule in Upregulating NF-κB/HIF-1α Pathway to Improve the Quality of Bone Callus in Mice at Different Stages of Osteoporotic Fracture Healing

Objective. The present study intends to investigate the effects and underlying molecular mechanism of Qigu Capsule (QG) on fracture healing in mice with osteoporosis. Methods. Ten-week-old female C57BL/6 mice were ovariectomized and three weeks later were evaluated for successful modeling. Then, all mice were prepared into models of transverse fracture in the right middle femoral shaft. Mice were treated daily using a gavage with normal saline (the NS group), Qigu Capsule (the QG group), or alendronate (the ALN group) postoperatively. Fracture callus tissues were collected and analyzed by X-ray, micro-CT, western blot (WB), and transmission electron microscope (TEM) on postoperation Day 14 (POD14), POD28, and POD42. Results. (1) X-ray results showed that on POD14, the QG group had the fracture healing score significantly higher than the NS and ALN groups, and on POD28, it had the fracture healing score higher than the NS group, suggesting that QG could promote fracture healing. (2) Micro-CT results showed that on POD14, the QG group had tissue bone density (TMD) significantly higher than the NS and ALN groups, and on POD28 and POD42, it had bone volume fraction, trabecular number, and TMD significantly higher than the NS group. (3) WB results showed that, compared with the NS group, the QG group had significantly increased expression of nuclear factor kappa-B (NF-κB), hypoxia-inducible factor-1α (HIF-1α), bone alkaline phosphatase (BALP), runt-related transcription factor 2 (Runx2), bone Gla protein (BGP) and collagen Iα1 (COLIα1) on POD14, significantly increased expression of NF-κB, HIF-1α, BALP and COLIα1 on POD28, and significantly increased expression of NF-κB, HIF-1α, and Runx2 on POD42. (4) TEM scanning results showed that, compared with the NS and ALN groups, the QG group had significantly increased numbers of autophagic vacuoles (AVs) in osteocytes on POD14, POD28, and POD42. Conclusion. QG could accelerate osteoporotic fracture healing by promoting bone formation and osteocyte autophagy, possibly through upregulating the NF-κB/HIF-1α signaling pathway.