Alterations of bone material properties in adult patients with X-linked hypophosphatemia (XLH).

X-linked hypophosphatemia (XLH) caused by PHEX mutations results in elevated serum FGF23 levels, renal phosphate wasting and low 1,25-dihydroxyvitamin D. The glycophosphoprotein osteopontin, a potent inhibitor of mineralization normally degraded by PHEX, accumulates within the bone matrix. Conventional therapy consisting of supplementation with phosphate and vitamin D analogs is burdensome and the effects on bone material poorly characterized. We analyzed transiliac bone biopsies from four adult patients, two of them severely affected due to no diagnosis and no treatment until adulthood. We used light microscopy, qBEI and FTIRI to study histology, histomorphometry, bone mineralization density distribution, properties of the organic matrix and size of hypomineralized periosteocytic lesions. Non-treatment resulted in severe osteomalacia, twice the amount of mineralized trabecular volume, multiple osteon-like perforations, continuity of lamellae from mineralized to unmineralized areas and distinctive patches of woven bone. Periosteocytic lesions were larger than in treated patients. The latter had nearly normal osteoid thicknesses, although surface was still elevated. The median calcium content of the matrix was always within normal range, although the percentage of lowly mineralized bone areas was highly increased in non-treated patients, resulting in a marked heterogeneity in mineralization. Divalent collagen cross-links were evident independently of the mineral content of the matrix. Broad osteoid seams lacked measurable pyridinoline, a mature trivalent cross-link and exhibited considerable acidic lipid content, typically found in matrix vesicles. Based on our results, we propose a model that possibly integrates the relationship between the observed mineralization disturbances, FGF23 secretion and the known osteopontin accumulation in XLH.

Multimodal X-ray imaging of nanocontainer-treated macrophages and calcium distribution in the perilacunar bone matrix.

Studies of biological systems typically require the application of several complementary methods able to yield statistically-relevant results at a unique level of sensitivity. Combined X-ray fluorescence and ptychography offer excellent elemental and structural imaging contrasts at the nanoscale. They enable a robust correlation of elemental distributions with respect to the cellular morphology. Here we extend the applicability of the two modalities to higher X-ray excitation energies, permitting iron mapping. Using a long-range scanning setup, we applied the method to two vital biomedical cases. We quantified the iron distributions in a population of macrophages treated with Mycobacterium-tuberculosis-targeting iron-oxide nanocontainers. Our work allowed to visualize the internalization of the nanocontainer agglomerates in the cytosol. From the iron areal mass maps, we obtained a distribution of antibiotic load per agglomerate and an average areal concentration of nanocontainers in the agglomerates. In the second application we mapped the calcium content in a human bone matrix in close proximity to osteocyte lacunae (perilacunar matrix). A concurrently acquired ptychographic image was used to remove the mass-thickness effect from the raw calcium map. The resulting ptychography-enhanced calcium distribution allowed then to observe a locally lower degree of mineralization of the perilacunar matrix.

Osteoblasts are "educated" by crosstalk with metastatic breast cancer cells in the bone tumor microenvironment.

INTRODUCTION: In a cancer-free environment in the adult, the skeleton continuously undergoes remodeling. Bone-resorbing osteoclasts excavate erosion cavities, and bone-depositing osteoblasts synthesize osteoid matrix that forms new bone, with no net bone gain or loss. When metastatic breast cancer cells invade the bone, this balance is disrupted. Patients with bone metastatic breast cancer frequently suffer from osteolytic bone lesions that elicit severe bone pain and fractures. Bisphosphonate treatments are not curative. Under ideal circumstances, osteoblasts would synthesize new matrix to fill in erosion cavities caused by osteoclasts, but this is not what occurs. Our prior evidence demonstrated that osteoblasts are diverted from laying down bone matrix to producing cytokines that facilitate breast cancer cell maintenance in late-stage disease. Here, we have new evidence to suggest that there are subpopulations of osteoblasts in the tumor niche as evidenced by their protein marker expression that have distinct roles in tumor progression in the bone. METHODS: Tumor-bearing tibia of mice was interrogated by immunofluorescent staining for the presence of osteoblasts and alterations in niche protein expression. De-identified tissue from patients with bone metastatic breast cancer was analyzed for osteoblast subpopulations via multi-plex immunofluorescent staining. Effects of breast cancer cells on osteoblasts were recapitulated in vitro by osteoblast exposure to breast cancer-conditioned medium. Triple-negative and estrogen receptor-positive breast cancer proliferation, cell cycle, and p21 expression were assessed upon contact with "educated" osteoblasts. RESULTS: A subpopulation of osteoblasts was identified in the bone tumor microenvironment in vivo of both humans and mice with bone metastatic breast cancer that express RUNX2/OCN/OPN but is negative for IL-6 and alpha-smooth muscle actin. These tumor "educated" osteoblasts (EOs) have altered properties compared to "uneducated" osteoblasts and suppress both triple-negative and estrogen receptor-positive breast cancer cell proliferation and increase cancer cell p21 expression. EO effects on breast cancer proliferation were mediated by NOV and decorin. Importantly, the presence of EO cells in the tibia of mice bearing tumors led to increased amounts of alkaline phosphatase and suppressed the expression of inflammatory cytokines in vivo. CONCLUSIONS: Our work reveals that there is a subpopulation of osteoblasts in the bone tumor microenvironment that demonstrate a functional role in retarding breast cancer cell growth.

Metaplastic woven bone in bone metastases: A Fourier-transform infrared analysis and imaging of bone quality (FTIR).

Most osteolytic tumors are in fact mixed and contain an osteoblastic component associated with the predominant osteolytic areas. This metaplastic woven bone is always evidenced by histological analysis even in the absence of radiological expression. Metaplastic bone formation reflects the activation of new osteoblasts coming from the stimulation of the dormant lining cells. Twelve patients with secondary metastases of the iliac crest evidenced by hot spots on a 99Tc-MBP san were diagnosed by histomorphometry on bone biopsies. Fourier Transformed InfraRed analysis and Imaging (FTIRI) was used on 4µm thick sections of undecalcified bone. The mineralization degree, carbonate substitution, crystallinity and the cross-links ratio of collagen (1660/1690cm-1 bands) were determined. The matrix characteristics were analyzed and imaged in the pre-existing residual bone and in the metaplastic woven bone in the vicinity of the tumor cells. FTIRI provided images of the phosphate, amide and combination of peak ratio after having selected the peaks of interest. In addition, the matrix properties can be measured and compared between the old and newly-formed bones. Woven bone appeared poorly calcified with a low phosphate/amide ratio (P=0.03) crystallinity (P<0.0001) and carbonate substitution (P=0.003). Collagen was less mature as evidenced by lower cross-links (P=0.01). Woven bone associated with bone metastasis appears poorly mineralized and rapidly elaborated by osteoblasts. The collagenous phase of the bone matrix has a low level of reticulation. FTIRI is a powerful tool to measure and visualize the various components of the bone matrix in human diseases.

Cortical Matrix Mineral Density Measured Noninvasively in Pre- and Postmenopausal Women and a Woman With Vitamin D-Dependent Rickets.

Reduced bone mineral density (BMD) may be due to reduced mineralized bone matrix volume, incomplete secondary mineralization, or reduced primary mineralization. Because bone biopsy is invasive, we hypothesized that noninvasive image acquisition at high resolution can accurately quantify matrix mineral density (MMD). Quantification of MMD was confined to voxels attenuation photons above 80% of that produced by fully mineralized bone matrix because attenuation at this level is due to variation in mineralization, not porosity. To assess accuracy, 9 cadaveric distal radii were imaged at a voxel size of 82 microns using high-resolution peripheral quantitative computed tomography (HR-pQCT; XtremeCT, Scanco Medical AG, Bruttisellen, Switzerland) and compared with VivaCT 40 (µCT) at 19-micron voxel size. Associations between MMD and porosity were studied in 94 healthy vitamin D-replete premenopausal women, 77 postmenopausal women, and in a 27-year-old woman with vitamin D-dependent rickets (VDDR). Microstructure and MMD were quantified using StrAx (StraxCorp, Melbourne, Australia). MMD measured by HR-pQCT and µCT correlated (R = 0.87; p < 0.0001). The precision error for MMD was 2.43%. Cortical porosity and MMD were associated with age (r2 = 0.5 and -0.4, respectively) and correlated inversely in pre- and postmenopausal women (both r2 = 0.9, all p < 0.001). Porosity was higher, and MMD was lower, in post- than in premenopausal women (porosity 40.3% ± 7.0 versus 34.7% ± 3.5, respectively; MMD 65.4% ± 1.8 versus 66.6% ± 1.4, respectively, both p < 0.001). In the woman with VDDR, MMD was 5.6 SD lower and porosity was 5.6 SD higher than the respective trait means in premenopausal women. BMD was reduced (Z-scores femoral neck -4.3 SD, lumbar spine -3.8 SD). Low-radiation HR-pQCT may facilitate noninvasive quantification of bone's MMD and microstructure in health, disease, and during treatment. © 2018 American Society for Bone and Mineral Research.

Bone matrix microdamage and vascular changes characterize bone marrow lesions in the subchondral bone of knee osteoarthritis.

INTRODUCTION: Bone marrow lesions (BMLs) in the subchondral bone in osteoarthritis (OA) are suggested to be multifactorial, although the pathogenic mechanisms are unknown. Bone metabolism and cardiovascular risk factors associate with BML in epidemiologic studies. However, there are no studies at the tissue level investigating the relationship between these processes and BML. The aim of this study was to investigate the relationship between BMLs in the tibial plateau (TP) of knee OA and bone matrix microdamage, osteocyte density and vascular changes. METHODS: TP were obtained from 73 patients at total knee replacement surgery and BMLs were identified ex vivo in TP tissue using MRI. Comparator 'No BML' tissue was from matched anatomical sites to the BMLs. Quantitative assessment was made of subchondral bone microdamage, bone resorption indices, osteocyte cellularity, and vascular features. RESULTS: Several key parameters were different between BML and No BML tissue. These included increased microcrack burden (p = .01, p = .0001), which associated positively with bone resorption and negatively with cartilage volume, and greater osteocyte numerical density (p = .02, p = .01), in the subchondral bone plate and subchondral trabeculae, respectively. The marrow tissue within BML zones contained increased arteriolar density (p = .04, p = .0006), and altered vascular characteristics, in particular increased wall thickness (p = .007) and wall:lumen ratio (wall thickness over internal lumen area) (p = .001), compared with No BML bone. CONCLUSIONS: Increased bone matrix microdamage and altered vasculature in the subchondral bone of BMLs is consistent with overloading and vascular contributions to the formation of these lesions. Given the important role of BMLs in knee OA, these contributing factors offer potential targets for the treatment and prevention of knee OA.

Newly Formed Bone Induced by Recombinant Human Bone Morphogenetic Protein-2: A Histological Observation.

PURPOSE: To observe, histologically, bone induced by recombinant human bone morphogenetic protein-2 (rhBMP-2) in onlay grafted and sinus lifted alveolaris. MATERIAL AND METHODS: Eighteen patients were treated with rhBMP-2 at concentration 1.5 mg/mL with an absorbable collagen sponge (ACS). The treated bone was harvested with small trephine bur at 5 or 7 months after surgery for the micro Computer Scanning (CT) and light microscopic observation. RESULTS: Micro CT showed clearly 3-dimensional trabecular bone structure. New bone formation and bone marrow structure were observed in the observed area. Osteoblastic cells existed along the new bone, and osteopontin was localized in the bone matrix weakly. In the connective tissue around the new bone, many CD34-positive blood vessel cells were present. Some tartrate-resistant acid phosphatase (TRAP)-positive osteoclastic cells were observed around bone at this stage. CONCLUSION: The application of rhBMP-2 with ACS induced a new bone accompanied by blood vessels in atrophied alveolaris. This suggests that rhBMP-2 is capable of osteoinductivity in human jaw.

Differences in bone remodeling using demineralized bone matrix in bilateral sagittal split ramus osteotomy: a study on volumetric analysis using three-dimensional cone-beam computed tomography.

PURPOSE: The aim of this study was to examine the effects of demineralized bone matrix (DBM) grafts on bone remodeling during sagittal split ramus osteotomy by measuring 3-dimensional (3D) reconstructed images. PATIENTS AND METHODS: Forty-eight patients were selected for this study. In the control group, no grafts were performed. In the DBM group, DBX grafts were placed between the proximal and distal segments. Three-dimensional cone-beam computerized tomographic (3D-CBCT) images were obtained within 1 week, after 3 months (T2), and after 6 months (T3) postoperatively. By measuring the total skeletal volume from the right condylar head to the right mandibular first molar, the volume of the graft site was measured indirectly. Using the data thus obtained, a volume-increasing ratio (percentage) was computed. SimPlant analytical software was used to analyze the 3D reconstructed volumes. RESULTS: The 2 groups showed a significant increase in volume. However, in the same period, the volume-increasing ratios of the 2 groups showed significant differences. In the control group, a significant increase in volume was seen until T2, after which a negligible increase was seen. Conversely, in the DBM group, a significant volume increase continued until T3. CONCLUSION: In orthognathic surgeries, grafting using DBM is a favorable procedure that accelerates bone formation. Therefore, in cases with inevitable large bony gaps, DBM grafts can play a positive role in the stable healing of segments and the prevention of postoperative complications. Moreover, because volumetric analysis using 3D-CBCT analyzing software is a fast and simple method, future studies using this technique are expected to increase.

3D osteocyte lacunar morphometric properties and distributions in human femoral cortical bone using synchrotron radiation micro-CT images.

Osteocytes, the most numerous bone cells, are thought to be actively involved in the bone modeling and remodeling processes. The morphology of osteocyte is hypothesized to adapt according to the physiological mechanical loading. Three-dimensional micro-CT has recently been used to study osteocyte lacunae. In this work, we proposed a computationally efficient and validated automated image analysis method to quantify the 3D shape descriptors of osteocyte lacunae and their distribution in human femurs. Thirteen samples were imaged using Synchrotron Radiation (SR) micro-CT at ID19 of the ESRF with 1.4µm isotropic voxel resolution. With a field of view of about 2.9×2.9×1.4mm(3), the 3D images include several tens of thousands of osteocyte lacunae. We designed an automated quantification method to segment and extract 3D cell descriptors from osteocyte lacunae. An image moment-based approach was used to calculate the volume, length, width, height and anisotropy of each osteocyte lacuna. We employed a fast algorithm to further efficiently calculate the surface area, the Euler number and the structure model index (SMI) of each lacuna. We also introduced the 3D lacunar density map to directly visualize the lacunar density variation over a large field of view. We reported the lacunar morphometric properties and distributions as well as cortical bone histomorphometric indices on the 13 bone samples. The mean volume and surface were found to be 409.5±149.7µm(3) and 336.2±94.5µm(2). The average dimensions were of 18.9±4.9µm in length, 9.2±2.1µm in width and 4.8±1.1µm in depth. We found lacunar number density and six osteocyte lacunar descriptors, three axis lengths, two anisotropy ratios and SMI, that are significantly correlated to bone porosity at a same local region. The proposed method allowed an automatic and efficient direct 3D analysis of a large population of bone cells and is expected to provide reliable biological information for better understanding the bone quality and diseases at cellular level.

Bone repair is influenced by different particle sizes of anorganic bovine bone matrix: a histologic and radiographic study in vivo.

PURPOSE: The aim of this study was to analyze histologically and radiographically the influence of particle size of anorganic bovine bone matrix (ABBM) on bone repair. MATERIALS AND METHODS: Four calvarial defects of 8 mm each were prepared in 18 adult New Zealand rabbits. The defects were then filled with either particulate autogenous bone (control group) or ABBM of large, medium, and small size granules. The animals were sacrificed at 15, 30, and 60 days after surgery. The samples were radiographically examined before being submitted to histological processing. RESULTS: Autogenous bone showed a slight radiopacity at the beginning, which was increased at the final period, being very similar to the adjacent bone tissue. The large and medium size ABBM particles maintained the same radiographic behavior, showing a radiolucent area in the central portion of the defect at 60 days. ABBM of small size granules showed a slight radiolucity at the initial period, which was increased at the subsequent periods. More intense bone formation occurred in the control group (autogenous bone). All 3 particle sizes of the biomaterial resulted in inflammatory infiltration at 15 and 30 days. ABBM of small size granules lead to a greater amount of osteoid tissue, and the particles were almost totally reabsorbed within 60 days of implantation. CONCLUSIONS: Autogenous bone graft lead to the best result in terms of bone defect repair; ABBM of large and medium size granules are not totally reabsorbed at the observed period; ABBM of small size granules was more intensively reabsorbed and led to a greater osteoid tissue formation when compared to the medium and large ABBM granules.

Equine-derived bone mineral matrix for maxillary sinus floor augmentation: a clinical, radiographic, histologic, and histomorphometric case series.

The objective of this proof-of-principle multicenter case series was to examine the bone regenerative potential of a newly introduced equine-derived bone mineral matrix (Equimatrix) to provide human sinus augmentation for the purpose of implant placement in the posterior maxilla. There were 10 patients requiring 12 maxillary sinus augmentations enrolled in this study. Histologic results at 6 months demonstrated abundant amounts of vital new bone in intimate contact with residual graft particles. Active bridging between residual graft particles with newly regenerated bone was routinely observed in intact core specimens. A mean value of 23.4% vital bone formation was observed at 6 months. This compared favorably with previous results using xenografts to produce bone in the maxillary sinus for the purpose of dental implant placement. Both the qualitative and quantitative results of this case series suggest comparable bone regenerative results at 6 months to bovine-derived xenografts.

The animal experiment of a new optimised distraction implant.

Our aim was to evaluate the function of a new optimised distraction implant. Six dogs with alveolar bone defects had a total of 18 distraction, and 6 normal, implants inserted into edentulous mandibular ridges after osteotomy. Five days after insertion the distraction implants were activated at a rate of 1 mm/2 days to achieve a distraction height of 6mm. Radiographs were taken at 0, 1, 2, and 3 months after distraction. Two dogs were killed after 1, 2, and 3 months, respectively, and 12 distraction implants taken from the different time points were evaluated by microcomputed tomographic (MicroCT) scanning and histological examination. The other 6 distraction, and the 6 normal, implants were compared after osseointegration with a fatigue test. The results showed that all the distraction implants had successfully distracted the bone to the anticipated height. Radiographs showed that the density of the regenerated bone increased steadily during the consolidation period. MicroCT showed that the regenerated bone was comparable with the native bone 3 months after distraction. Both native and regenerated bone had osseointegrated histologically by 1 month and 3 months after distraction. The experiment successfully confirmed the usefulness and feasibility of this new distraction implant, and suggests interesting clinical uses.

Three-dimensional volumetric analysis after sinus grafts.

PURPOSE: The purpose of this study was to evaluate the augmentation volume of a sinus graft according to the time and graft materials based on cone-beam computed tomography (CBCT) scans and to assess efficacy of a bioabsorbable membrane. METHODS: Fourteen patients were investigated, and volumetric analysis was performed using OnDemand 3DTM software (Cybermed, Seoul, Korea). CBCT scans were performed on patients before surgery, immediately after surgery, 6 months after surgery, and 1 year after surgery. Following this analysis, the volumetric data were compared with the actual grafted volumes. Bioabsorbable membranes were used in all patients to promote the protection of sinus membranes and to guide bone regeneration. RESULTS: Overall, the average percent volume of graft material that remained 6 months after implantation was 82.0%, and the average percent volume of graft material that remained 1 year after surgery was 60.4%. These reductions in the volume of graft material from immediately after surgery until 6 months or 1 year after surgery were shown to be statistically significant (P = 0.002 and P < 0.001, respectively). CONCLUSION: The slight differences observed among the data indicate that volumetric analysis performed using CBCT can provide highly accurate data. A significant difference was observed in volumetric change over time, but no significant differences were observed between materials. No significant relationship was observed between the resorption of grafted bone and the success rate.

Minimally invasive ridge augmentation using xenogenous bone blocks in an atrophied posterior mandible: a clinical and histological study.

PURPOSE: Although various techniques for the treatment of an atrophic alveolar ridge have been described in the literature, these procedures have increased the morbidity and discomfort for the patient. The purpose of this study was to evaluate histological and clinical results in 9 patients who underwent a subperiosteal tunneling procedure with a Bio-Oss block onlay graft in an atrophic area of the mandible. PATIENTS AND METHODS: Nine months after grafting, at the time of dental implantation, biopsy samples were taken from the grafted areas of 9 patients and were analyzed histologically. RESULTS: New bone formation through the bovine bone block was observed consistently in the 9 cases. There was direct deposition of bone on the surface of the graft material. CONCLUSION: The results of this study indicated that ridge augmentation using a subperiosteal tunneling procedure with Bio-Oss bone blocks might be useful for implant placement in the atrophic alveolar ridges.

Clinical-radiographic and histological evaluation of two hydroxyapatites in human extraction sockets: a pilot study.

After tooth extraction the healing process involves bone resorption and soft tissue contraction, events that can compromise the ideal implant placement with functional and aesthetic limitations. Following tooth extraction, a socket preservation technique can limit bone resorption. This study evaluated two different types of hydroxyapatite (HA) grafting materials placed into fresh extraction sockets, 6 months after tooth extraction, histologically, clinically and radiographically. Ten extraction sockets from 10 patients were divided in two groups: 5 sockets received a biomimetic HA and 5 received nanocrystalline HA. After 6 months, before implant placement, samples from the grafted area were harvested and evaluated clinically, radiographically and histologically. The percentages of bone, osteoid areas and residual material in the two groups were not statistically different. All samples showed great variability with extensive bone formation and total material resorption or amounts of osteoid tissue that filled the spaces between the residual material particles. The authors did not find any differences between biomimetic and nanocrystalline HA and assume that, within the limits of this study, both these materials could be applied into fresh extraction sockets to limit bone resorption. A control material and a much larger sample size are needed to confirm these findings.

Evaluation of osteoinduction properties of the demineralized bovine foetal growth plate powder as a new xenogenic biomaterial in rat.

The aim of this study was evaluation of osteoinductive properties of demineralized bovine foetal growth plate in submuscular transplantation (ectopic osteoinduction) as a new xenogenic biomaterial in rat model. Demineralized bovine foetal growth plate was ectopically implanted in 18 male Sprague-Dawley rats. In 18 of the animals under aseptic conditions two submuscular pouches were created between external and internal oblique abdominal muscles in the two flanks: the right was left empty (sham) and the left was filled with 20mg of demineralized bovine foetal growth plate powder. Radiographs were taken in 2, 4 and 6 weeks after the surgery, then six animals were pharmacologically euthanized after 2, 4 and 6 weeks for histopathological evaluation. Results showed: (1) osteoinductivity of xenogenic demineralized bovine foetal growth plate powder, and (2) earlier mineralization of ectopically implanted demineralized bovine foetal growth plate in the submuscular implanted area. Our results show that submuscular implantation of xenogenic demineralized bovine foetal growth plate has osteoinductive properties in a rat model.

Increased matrix mineralization in the immature femoral head following ischemic osteonecrosis.

Traditionally, it is believed that structural failure of the ischemic epiphysis as well as changes in radiodensity seen in the early stage of Legg-Calvé-Perthes disease is due to the repair process. However, little is known if matrix properties are altered following ischemic injury of the juvenile femoral head. The purpose of this study was to determine the matrix mineralization density, an important determinant of material quality and strength, of the proximal femoral epiphysis in an experimental animal model of Perthes disease. Ten piglets were surgically induced with femoral head ischemia and euthanized at 4 and 8 weeks following surgery. Contralateral, unoperated femoral heads were used as controls. Bone and calcified cartilage mineralization density distribution parameters were determined using quantitative backscattered electron imaging (qBEI) in the epiphyseal calcified articular cartilage, subchondral bone and central trabecular bone region. Histological as well as radiographic assessment was also performed. In the necrotic calcified epiphyseal cartilage matrix, a significant increase in the mean degree of mineralization (CaMean: +24%, p<0.0001) as well as the homogeneity of mineralization (CaWidth: -21%, p<0.05) and a significantly reduced amount of low mineralized matrix (CaLow: -49%, p<0.0001) were already present at 4 weeks post-ischemia induction. Similar changes, but more moderate, were also seen in the subchondral bone region. In contrast, in the necrotic central trabecular region, significant changes in matrix mineralization were found at 8 weeks (CaMean: +4%, p<0.05; CaWidth: -22%, p<0.05; CaLow: -8%, p<0.05) but not at 4 weeks post-ischemia induction. Our findings indicate that the process of matrix mineralization continues in necrotic calcified articular cartilage and bone following femoral head ischemia, which leads to a higher and more homogenous mineralized tissue matrix altering its intrinsic material properties. This may also explain the increased radiodensity seen in the early stage of Perthes disease prior to the initiation of the repair process.

Cancellous bone properties and matrix content of TGF-beta2 and IGF-I in human tibia: a pilot study.

Transforming and insulin-like growth factors are important in regulating bone mass. Thus, one would anticipate correlations between matrix concentrations of growth factors and functional properties of bone. We therefore investigated the relationships of (1) TGF-beta2 and (2) IGF-I matrix concentrations with the trabecular microstructure, stress distribution, and mechanical properties of tibial cancellous bone from six male human cadavers. Trabecular stress amplification (VMExp/sigma(app)) and variability (VMCOV) were calculated using microcomputed tomography (muCT)-based finite element simulations. Bone volume fraction (BV/TV), surface/volume ratio (BS/BV), trabecular thickness (Tb.Th), number (Tb.N) and separation (Tb.Sp), connectivity (Eu.N), and anisotropy (DA) were measured using 3-D morphometry. Bone stiffness and strength were measured by mechanical testing. Matrix concentrations of TGF-beta2 and IGF-I were measured by ELISA. We found higher matrix concentrations of TGF-beta2 were associated with higher Tb.Sp and VMExp/sigma(app) for pooled data and within subjects. Similarly, a higher matrix concentration of IGF-I was associated with lower stiffness, strength, BV/TV and Tb.Th and with higher BS/BV, Tb.Sp, VMExp/sigma(app) and VMCOV for pooled data and within subjects. IGF-I and Tb.N were negatively associated within subjects. It appears variations of the stress distribution in cancellous bone correlate with the variation of the concentrations of TGF-beta2 and IGF-I in bone matrix: increased local matrix concentrations of growth factors are associated with poor biomechanical and architectural properties of tibial cancellous bone.

Fibrogenesis imperfecta ossium: MR imaging of the axial and appendicular skeleton and correlation with a unique radiographic appearance.

We describe a distinctly unusual MR appearance of the cancellous bone never before described in a patient with biopsy-proven fibrogenesis imperfecta ossium.

Augmentation of demineralized bone matrix (DBM) mineralization by a synthetic growth factor mimetic.

These studies evaluated whether F2A4-K-NS, a peptide mimetic of FGF-2, could augment ectopic bone production following the subcutaneous implant of human demineralized bone matrix (DBM). DBM was formulated into a gel with and without F2A4-K-NS, and injected subcutaneously into athymic rats. After 28 days the resultant tissue was excised and fixed. The tissue was examined with soft X-rays and microcomputerized tomography (micro-CT), and by histological methods. Inclusion of F2A4-K-NS with DBM resulted in an increased mineral deposition as determined by soft X-ray and micro-CT analysis and von Kossa staining. DBM-containing tissues showed extensive mineralization compared to the carrier alone, which was poorly mineralized. The mineralization was qualitatively and quantitatively the most extensive in the samples containing F2A4-K-NS plus DBM. Additionally, the highest amount of von Kossa staining for calcium was observed in tissues from animals that had received DBM plus F2A4-K-NS. In these studies, 100 ng of peptide per 0.2 mL of injectable DBM gel generated the most optimal results. The synthetic peptide F2A4-K-NS augmented DBM-induced ectopic mineralization in athymic animals.