Surface Of Trabeculae Research Articles

Histochemical localization of alkaline phosphatase activity in decalcified bone and cartilage.

We have developed methodology that enables alkaline phosphatase (ALP) to be histochemically stained reproducibly in decalcified paraffin-embedded bone and cartilage of rodents. Proximal tibiae and fourth lumbar vertebrae were fixed in periodate-lysine-paraformaldehyde (PLP) fixative, decalcified in an EDTA-G solution, and embedded in paraffin. In the articular cartilage of the proximal tibia, ALP activity was localized to the hypertrophic chondrocytes and cartilage matrix of the deep zone and the maturing chondrocytes of the intermediate zone. The cells and matrix in the superficial zone did not exhibit any enzyme activity. In tibial and vertebral growth plates, a progressive increase in ALP expression was seen in chondrocytes and cartilage matrix, with activity being weakest in the proliferative zone, higher in the maturing zone, and highest in the hypertrophic zone. In bone tissue, ALP activity was detected widely in pre-osteoblasts, osteoblasts, lining cells on the surface of trabeculae, some newly embedded osteocytes, endosteal cells, and subperiosteal cells. In areas of new bone formation, ALP activity was detected in osteoid. In the bone marrow, about 20% of bone marrow cells expressed ALP activity. In adult rats, the thickness of the growth plates was less and ALP activity was enhanced in maturing and hypertrophic chondrocytes, cartilage matrix in the hypertrophic zone, and primary spongiosa. This is the first time that ALP activity has been successfully visualized histochemically in decalcified, paraffin-embedded mineralized tissues. This technique should prove to be a very convenient adjunct for studying the behavior of osteoblasts during osteogenesis.

Trabecular bone's mechanical properties are affected by its non-uniform mineral distribution

The bone remodeling process takes place at the surface of trabeculae and results in a non-uniform mineral distribution. This will affect the mechanical properties of cancellous bone, because the properties of bone tissue depend on its mineral content. We investigated how large this effect is by simulating several non-uniform mineral distributions in 3D finite element models of human trabecular bone and calculating the apparent stiffness of these models. In the ‘linear model’ we assumed a linear relation between mineral content and Young's modulus of the tissue. In the ‘exponential model’ we included an empirical exponential relation in the model. When the linear model was used the mineral distribution slightly changed the apparent stiffness, the difference varied between an 8% decrease and a 4% increase compared to the uniform model with the same BMD. The exponential model resulted in up to 20% increased apparent stiffness in the main load-bearing direction. A thin less mineralized surface layer (28 μm) and highly mineralized interstitial bone (mimicking mineralization resulting from anti-resorptive treatment) resulted in the highest stiffness. This could explain large reductions in fracture risk resulting from small increases in BMD. The non-uniform mineral distribution could also explain why bone tissue stiffness determined using nano-indentation is usually higher than finite element (FE)-determined stiffness. We conclude that the non-uniform mineral distribution in trabeculae does affect the mechanical properties of cancellous bone and that the tissue stiffness determined using FE-modeling could be improved by including detailed information about mineral distribution in trabeculae in the models.

Scanning Electron Microscopic Observation of Transverse (Harris) Lines in the Femur and Tibia of Anatomy Cadavers.

To investigate the occurrence of transverse lines in long bones of adults, we studied 27 cadavers (14 males and 13 females) used for teaching anatomy, and took a roentgenogram of the femur and tibia. After confirming the presence of a transverse line, a cross-sectional sample was examined macroscopically, and by soft X-ray and scanning electron microscopy. The following results were obtained: 1) According to roentgenograms, transverse (Harris') lines were observed in 40.7% of the distal half of the femur and in 29.6% of the proximal half of the tibia. These showed a strong tendency for bilateral symmetry as is characteristic of transverse lines and the frequency was much higher than previous reports suggested. 2) Macroscopic examination of the bone cross-sections at the level of the transverse line showed membranous structures of various morphologies, ranging from complete interruption of the medullary space to a washer-like appearance, or the structures were formed by joined trabeculae. The frequency of detection may vary according to the observation method. 3) In scanning electron micrographs, matrix fibers were observed on the surface of trabeculae. The transverse lines were clearly formed from osteoblasts. No marked difference in structure was observed between the transverse line trabeculae and the compact bone. 4) From these facts, we considered that further studies are necessary to examine the age-related changes of the transverse lines and the significance of their presence in adults.

Frequency dependence of ultrasonic backscatter from human trabecular bone: theory and experiment.

A model describing the frequency dependence of backscatter coefficient from trabecular bone is presented. Scattering is assumed to originate from the surfaces of trabeculae, which are modeled as long thin cylinders with radii small compared with the ultrasonic wavelength. Experimental ultrasonic measurements at 500 kHz, 1 MHz, and 2.25 MHz from a wire target and from trabecular bone samples from human calcaneus in vitro are reported. In both cases, measurements are in good agreement with theory. For mediolateral insonification of calcaneus at low frequencies, including the typical diagnostic range (near 500 kHz), backscatter coefficient is proportional to frequency cubed. At higher frequencies, the frequency response flattens out. The data also suggest that at diagnostic frequencies, multiple scattering effects on the average are relatively small for the samples investigated. Finally, at diagnostic frequencies, the data suggest that absorption is likely to be a larger component of attenuation than scattering.

Origin of bone‐forming cells in human osteosarcomas transplanted into nude mice—which cells produce bone, human or mouse?

Osteosarcomas are malignant tumours producing osteoid and/or bone. It is difficult to distinguish tumour bone formation from reactive, based on their morphological features alone. The objective of this study was two-fold: to clarify the origins of bone-forming cells in human osteosarcoma transplanted into nude mice; and to examine the role of bone morphogenetic proteins (BMPs) in the tumour-induced osteogenesis. DNA in situ hybridization was carried out with digoxigenin (DIG) polymerase chain reaction (PCR) labelled DNA probes for human-specific ‘Alu’ and mouse-specific ‘mouse L1 (m-L1)’ genes. Human osteosarcoma cells, established cell lines of NOS-1, NOS-2, and HuO9, were transplanted separately into nude mice. Bone-forming cells of the bone in the NOS-1 or NOS-2 tumours were positive for Alu, while they were negative for m-L1. The cells lining the surface of trabeculae in the HuO9 tumour were positive for Alu, but a few of them were also positive for m-L1. The m-L1-positive cells expressed mouse osteocalcin and type I collagen mRNAs. These facts suggest that the mouse cells were involved in osteoid synthesis of the HuO9 tumour. The NOS-1 or NOS-2 tumours expressed human BMP 2–7 mRNAs, whereas the HuO9 tumour expressed human BMPs 2, 4, 5, and 7. The osteogenetic potential of the tumours may depend on the expression patterns of BMPs. These results demonstrate two distinct types of bone formation, by tumour cells and by an admixture of tumour and non-tumour cells. The present study showed that the HuO9 tumour produces chimeric bone formation. This is the first report to demonstrate the relationships between tumour cells and non-tumour cells in bone formation, using genetic markers. © 1998 John Wiley & Sons, Ltd.

Origin of bone-forming cells in human osteosarcomas transplanted into nude mice--which cells produce bone, human or mouse?

Osteosarcomas are malignant tumours producing osteoid and/or bone. It is difficult to distinguish tumour bone formation from reactive, based on their morphological features alone. The objective of this study was two-fold: to clarify the origins of bone-forming cells in human osteosarcoma transplanted into nude mice; and to examine the role of bone morphogenetic proteins (BMPs) in the tumour-induced osteogenesis. DNA in situ hybridization was carried out with digoxigenin (DIG) polymerase chain reaction (PCR) labelled DNA probes for human-specific 'Alu' and mouse-specific 'mouse L1 (m-L1)' genes. Human osteosarcoma cells, established cell lines of NOS-1, NOS-2, and HuO9, were transplanted separately into nude mice. Bone-forming cells of the bone in the NOS-1 or NOS-2 tumours were positive for Alu, while they were negative for m-L1. The cells lining the surface of trabeculae in the HuO9 tumour were positive for Alu, but a few of them were also positive for m-L1. The m-L1-positive cells expressed mouse osteocalcin and type 1 collagen mRNAs. These facts suggest that the mouse cells were involved in osteoid synthesis of the HuO9 tumour. The NOS-1 or NOS-2 tumours expressed human BMP 2-7 mRNAs, whereas the HuO9 tumour expressed human BMPs 2, 4, 5, and 7. The osteogenetic potential of the tumours may depend on the expression patterns of BMPs. These results demonstrate two distinct types of bone formation, by tumour cells and by an admixture of tumour and non-tumour cells. The present study showed that the HuO9 tumour produces chimeric bone formation. This is the first report to demonstrate the relationships between tumour cells and non-tumour cells in bone formation, using genetic markers.

Histomorphometric study of intratrabecular osteons in the iliac bone in three metabolic bone diseases.

Full-thickness biopsy specimens of iliac bones were submitted to morphometric analysis of intratrabecular osteons to study whether and how much the number and density of osteons increase in some metabolic bone diseases such as osteomalacia (OM), primary hyperparathyroidism (PHPT) and renal osteodystrophy (ROD). The biopsies were taken from 16 patients with OM of various causes, 18 with PHPT, 12 with ROD, and from 41 control cases. All the specimens were methacrylate-embedded, sectioned undecalcified and stained with solochrome cyanine or HE. Morphometry included measurements of the density of osteons and the volume of bone and osteoid, partially assisted with a semiautomatic digital image analyzer. Intratrabecular osteons were found to be more numerous in patients with metabolic disorder than in control. It was shown by discriminant analysis that the elevated number of osteons/cm2 tissue area contributes to the differentiation of abnormal from normal bones. The presence of blood vessels in the osteons indicated the biological significance of osteon formation which extends the metabolic surface of trabeculae, providing a basis for trabecular hypertrophy.

Osteoclast counting in crista biopsies.

A description is given of a modified method of counting osteoclasts both per section area and also relative to the remaining trabeculae surface area in crista biopsies. The material consisted of normal individuals, patients with clinical osteoporosis, and patients with chronic renal failure undergoing haemodialysis. The number of osteoclasts in the biopsies from normal and osteoporotic individuals showed a normal distribution with the same mean. In the haemodialysis patients there was a marked skew distribution. In normal individuals, there was a significant decrease in the number of osteoclasts per section area with age, but this was not significant when calculated relative to the bone surface area.

The development and mature structure of dentine in the pike, Esox lucius, analyzed by bright field, phase and polarization microscopy

Examination of the development and adult structure of the tissues of the teeth of the Great Northern Pike ( Esox lucius) using thin (0·5-2 μ) sections of plastic-embedded material and bright field, phase, and polarization microscopes showed the following: Phase microscopic preparations demonstrated clearly that the primary fabric of the mature teeth consisted of coarse collagen fibre bundles (α fibres). Thin fibres in the pallial dentine coursed toward and joined in the pulp to form the cores of very large trabecular fibre bundles. A finer textured fibrous matrix (β matrix) was interspersed between the odontoblast processes and the coarse α fibres in the pallial dentine. Development of alpha matrix preceded β matrix and consisted of birefringent trabecular α fibres, longitudinally arranged in the dental papilla which are formed in association with pulpal cells. Odontoblasts then differentiated from papillary ectomesenchymal, neural crest cells and were located between the α fibres. The odontoblasts produced β fibre matrix which filled in the spaces between the odontoblast processes and the coarse α fibres. The odontoblasts retreated from the appositionally forming β matrix, leaving cytoplasmic processes behind in dentinal canals. The coarse α pulp fibres increased in diameter and length probably by activity of the pulp mesenchyme. Fusion of odontoblast processes occurred and the perikarya accumulated in crypts at the pallial-trabecular junction. Matrix formation continued on the surface of the pulp trabeculae. Spaces between the trabeculae were interconnected and contained central blood vessels. Flattened fibroblastic-like cells covered the surface of the trabeculae. A general hypothesis is proposed relating α and β fibre matrix content and distribution to the various forms of dentine found in vertebrates.