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PubMed2003

[About remodelling in connection with two cases of bone substitution].

Numerous possibilities are available for the reconstruction of facial bone defects. The materials utilized to fill such defects must satisfy various requirements. One of the most important being that they must undergo transformation into autologous bone tissue in the process of remodelling. A report is given of the long-term results of augmentations performed with different bone-substitute materials in two patients. In one case, augmentation was carried out with beta-tricalcium phosphate following the removal of a fibromyxoma. In the second case, three large cystic lesions in the mandible of a patient with Gorlin-Goltz syndrome were filled with beta-tricalcium phosphate, with a mixture of beta-tricalcium phosphate and platelet concentrate, or with hydroxyapatite of algal origin respectively. The process of ossification was checked at 6-months intervals by means of clinical and radiological (orthopantomogramms and 2D and 3D computertomogramms) methods. One year after the intervention, the site of the augmentation was in all cases occupied by hard tissue of good quality. With the given imaging procedures, it was difficult to distinguish between the original bone and the region filled with bone-substitute material. The 3D computertomogramm images indicated that the contours and quality of the new bone corresponded to the physiological and anatomical conditions. The bone-substitute materials applied in these cases fully satisfied the demands of transformation into bone (remodelling).

Adolescent↗
PubMed2003

Modelling by percolation theory of the behaviour of natural coral used as bone substitute.

We investigate the relevance of site-bond percolation theory to model the resorption and ossification of natural coral implanted in bones. The first step of the process is the vascularization of the implant seen here as a percolation threshold. The resorption and ossification can thus take place by activation of unoccupied sites. We compare our results with previously obtained experimental data on implants in porcine cortical bones. Very encouraging results are obtained.

Absorption↗
PubMed2006

Modified keratin sponge: binding of bone morphogenetic protein-2 and osteoblast differentiation.

A keratin sponge was chemically modified to obtain carboxyl and amino sponges by the alkylation of a large amount of active SH group on keratin proteins with iodoacetic acid and 2-bromoethylamine, respectively. The carboxyl sponge having a large amount of carboxyl group was a scaffold that could bind significant amounts of basic bioactive proteins, such as lysozyme and bone morphogenetic protein (BMP)-2, and drugs. Lysozyme (maximum 3.7 mg), a model of basic cytokines such as BMP-2, was absorbed by the carboxyl sponge (4.8 mg), but not by the amino sponge. The lysozyme was rapidly released from the carboxyl sponge in a buffer containing at a concentration higher than 0.5 M, but at 0.15 M, near the physiological ionic strength, after initial burst (only 11%), no significant release was observed (15%, 48 h). BMP-2 also bound the carboxyl sponge. The preosteoblast cells grown inside the BMP-2-loaded sponge differentiated, whereas those grown outside the sponge did not, suggesting that no significant amount of BMP-2 leaked into the surrounding media. The effects of BMP-2 were confined inside modified keratin sponge. Therefore, using in vivo, we expect that only internal osteogenesis will be induced and that no external heterotopis ossification will be induced.

Alkaline Phosphatase↗
PubMed1998

Cathepsin K mRNA detection is restricted to osteoclasts during fetal mouse development.

We recently identified a novel cysteine protease, cathepsin K, by random sequencing of an osteoclast cDNA library, and in situ hybridization studies in adult human tissues demonstrated high and specific expression in osteoclasts. To determine whether the expression of cathepsin K mRNA during mouse embryogenesis was more widespread, cryostat sections of early (day 11-13) and late (day 15-17) mouse fetuses were analyzed by in situ hybridization. Serial cross-sections were collected through each fetus, and co-reacted for tartrate-resistant acid phosphatase (TRAP) and nonspecific esterase (NSE), selective markers for the osteoclast, and precursor cells derived from the macrophage/monocyte lineage, respectively. In the 11-13 day fetuses, cathepsin K mRNA was not expressed in any extraskeletal tissue; at this stage of embryogenesis, no osteoclasts are present. However, in the 15-17 day fetuses, a distinctive, developmental stage-dependent pattern of cathepsin K expression was observed in osteoclasts and preosteoclasts at sites of cartilage and bone modeling. Cathepsin K positive osteoclasts differentiated within a peripheral zone of the osteogenic stacked cell layer of the cartilage rudiments (prior to ossification), migrated and/or resorbed the bone collar, and invaded the cartilage core. Furthermore, following the invasive penetration of vasculature into the degenerating cartilage core, the calcified cartilage was resorbed by cathepsin K positive mononuclear osteoclast precursors (NSE+ve, negligible TRAP); cells positive for both enzymes were identified indicative of osteoclast differentiation. The deposition of bone by osteoblasts onto the cartilage remnants is followed by mononucleated and multinucleated osteoclastic resorption; these osteoclasts demonstrated intense cathepsin K expression. Similar expression patterns were observed at sites of intramembranous ossification. No expression was observed in chondrocytes, osteoblasts, marrow, or in any other nonskeletal tissue at these time points. These data indicated that cathepsin K expression during embryogenesis occurred only following the onset of osteoclast differentiation.

Acid Phosphatase↗
PubMed1995

Immunolocalization and expression of bone morphogenetic proteins 2 and 4 in fracture healing.

Recently, it has become increasingly evident that fracture healing involves a complex interaction of many local and systemic regulatory factors. The roles of some of these growth factors have been described; however, little is understood about the presence of the bone morphogenetic proteins in fracture repair, despite the fact that they are the most potent osteoinductive proteins known. This study defines and characterizes the physiologic presence, localization, and chronology of the bone morphogenetic proteins in fracture healing with an established rat fracture healing model. With use of a recently developed monoclonal antibody against bone morphogenetic proteins 2 and 4 developed with standard avidin-biotin complex/immunoperoxidase protocols, frozen undecalcified fracture calluses were analyzed semiquantitatively for the percentage of various types of fracture cells staining positively. During the early stages of fracture healing, only a minimum number of primitive cells stained positively in the fracture callus. As the process of endochondral ossification proceeded, the presence of bone morphogenetic proteins 2 and 4 increased dramatically, especially in the primitive mesenchymal and chondrocytic cells. While the cartilaginous component of the callus matured with a concomitant decrease in the number of primitive cells, there was a concomitant decrease in both the intensity and the number of positively staining cells. As osteoblasts started to lay down woven bone on the chondroid matrix, these osteoblastic cells exhibited strong positive staining. The intensity of this staining decreased, however, as lamellar bone replaced the primitive woven bone. A similar observation was noted for the areas of the callus undergoing intramembranous ossification. Initially, within several days after the fracture, periosteal cells and osteoblasts exhibited intense staining for bone morphogenetic proteins 2 and 4. As the woven bone was replaced with mature lamellar bone, this staining decreased. These data, and the awareness of the strong osteoinductive capacities of bone morphogenetic protein, suggest that bone morphogenetic proteins 2 and 4 are important regulators of cell differentiation during fracture repair.

Animals↗
PubMed1992

Aneurysmal bone cysts treated by superselective embolization.

A series of 7 cases of aneurysmal bone cysts (ABC), all but 1 located in the pelvic bones, which were treated by transcatheter embolization is presented. Five embolizations were performed for primary treatment, while in 2 patients they were performed preoperatively. In all patients a definite histological diagnosis was established by open biopsy, and plain radiographs as well as computerized tomography (CT) were applied for evaluation of the results. The embolizing materials were tissue adhesive for permanent, and Gelfoam for preoperative vessel occlusions. Of 5 lesions treated for the purpose of definitive embolization, 3 (all located in the superior pubic ramus) showed complete ossification; in one, partial remineralization and progression occurred. In a further patient with a secondary ABC, partial reconstitution was recorded. Both preoperative embolizations resulted in successful en bloc resection with minimal blood loss. Transcatheter embolization is the treatment of choice for the highly vascular ABC in unfavorable anatomical locations.

Adolescent↗
PubMedDate not supplied

[Development and growth of the epiphysis].

Most long bones end near the joint in a separate epiphysis which at first consists of cartilage and is later ossified. This epiphysis becomes fused with the shaft of the bone, in most cases only towards the end of puberty. The process is regulated by a number of parallel systemic, cellular and mechanical feedback controls, the complexity of which accounts for its liability to become disordered. The stress acting on the cartilaginous epiphysis is comparable to that in the adult. The relative differences may be attributed to variations in the mechanical relationship and to the hormonal control of the body's growth. The individual epiphyses undergo a characteristic series of events; central calcification, absorption of cartilage and endochondral ossification, the further course of which is definitely determined by the degree of local distortion. This applies to the general shape of the epiphysis as well as to its internal structure. The composition and thickness of the remaining articular cartilage are controlled by these feedback mechanisms throughout the whole of life.

Adolescent↗
PubMed1992

Modified tetrachrome method for osteoid and defectively mineralized bone in paraffin sections.

A new modification of the tetrachrome method for bone osteoid in paraffin sections has been designed. The modified tetrachrome method suitable for routine use in any histology laboratory retains the simplicity of the original method and gives good results on the freshly fixed, decalcified, paraffin embedded material. Osteoid tissue is stained deep blue and normally mineralized bone is stained red. Defectively mineralized bone stains pale blue or pink and the cellular population is clearly identifiable. The ability to distinguish the osteoid tissue from mineralized bone and connective tissue and cartilage makes diagnosis of osteomalacia or osteoid producing tumors or assessment of ossification process straightforward, without the need for undecalcified sections. By displaying simultaneously irregularities in the mineralized matrix and morphology of bone cells, the method also permits the diagnosis of conditions recently described in patients with osteoporotic fractures, such as osteocytic degeneration and bone tissue defects.

Aged↗
PubMedDate not supplied

Clinical and radiographic appearance of congenital talipes equinovarus after successful nonoperative treatment.

Thirty-one children with 49 feet after successful nonoperative treatment for congenital talipes equinovarus (CTEV) by redressements, hypoallergic adhesive bands, and plaster casts underwent follow-up. At the follow-up, the patients ranged in age from 4.2 years to 12.3 years (average, 8.3 years). The initial type of the deformity was as follows: type I (mild), 18 feet; type II (intermediate), 29 feet; type III (severe), two feet. Mild supination of the forefoot in five feet, isolated excavation in three, and adduction greater than physiological in two feet were the only persistent elements of the deformity. The lack or restriction of the dorsal flexion in the ankle were noted in 22 feet. In only three feet was the Beatson-Pearson index was < 40 degrees. In 17 feet, the radiographs revealed full talonavicular reduction in sagittal and horizontal planes. The average value of the talometatarsal first and tibiocalcaneal angles as in accordance with the standard. The most characteristic osseous disturbances concerned the tarsal navicular (22 feet) and consisted of the decrease of the ossification center, its flattening, fragmentation, cystic-like changes, and wedging.

Casts, Surgical↗
PubMed1985

Abnormal bone formation induced by implantation of osteosarcoma-derived bone-inducing substance in the X-linked hypophosphatemic mouse.

The X-linked hypophosphatemic mouse (Hyp) has been proposed as a model for the human familial hypophosphatemia (the most common form of vitamin D-resistant rickets). An osteosarcoma-derived bone-inducing substance was subcutaneously implanted into the Hyp mouse. The implant was consistently replaced by cartilage tissue at 2 weeks after implantation. The cartilage matrix seemed to be normal, according to the histological examination, and 35sulphur (35S) uptake was also normal. Up to 4 weeks after implantation the cartilage matrix was completely replaced by unmineralized bone matrix and hematopoietic bone marrow. Osteoid tissue arising from the implantation of bone inducing substance in the Hyp mouse showed no radiologic or histologic sign of calcification. These findings suggest that the abnormalities of endochondral ossification in the Hyp mouse might be characterized by the failure of mineralization in cartilage and bone matrix. Analysis of the effects of bone-inducing substance on the Hyp mouse may help to give greater insight into the mechanism and treatment of human familial hypophosphatemia.

Animals↗
PubMed1995

Distribution and expression of cartilage oligomeric matrix protein and bone sialoprotein show marked changes during rat femoral head development.

Distribution and sites of synthesis of a cartilage extracellular matrix protein, cartilage oligomeric matrix protein (COMP), and of a bone extracellular matrix protein, bone sialoprotein (BSP), were studied in the femoral head of growing Wistar rats from day 14 to day 60 by immunocytochemistry and in situ hybridization. This period includes formation of the secondary ossification center and differentiation of articular cartilage. At early stages, immunoreactivity for COMP was pronounced throughout the cartilage. The localization of COMP was predominantly territorial in the center of the immature femoral head and in the growth plate at all ages studied. In the superficial parts, a shift from a uniform extracellular matrix staining at day 14 to an interterritorial localization at day 33 to day 60 was seen, apparently concurrent with formation of articular cartilage. COMP staining, representing cartilage remnants, also extended into the center of the trabecular bone in the primary spongiosa. In the secondary ossification center, the staining for COMP decreased at the onset of calcification. The protein was only synthesized by chondrocytes, as shown by in situ hybridization. The highest level of COMP mRNA was detected in chondrocytes in the central region of the growth plate. In the layer corresponding to the articular cartilage of the femoral head, mRNA levels for COMP were low from day 14 to day 33 but were increased on day 60. This shows substantial synthesis in the developing articular cartilage. Immunoreactivity for BSP was detected in bone trabeculae of primary spongiosa. In situ hybridization showed the highest levels of BSP mRNA in regions of newly formed bone. BSP mRNA was detected in hypertrophic chondrocytes in the secondary ossification center as early as day 18, well before the appearance of immunochemically detectable BSP. Interestingly, simultaneous expression of COMP and BSP mRNA was seen after day 18 in hypertrophic chondrocytes of the growth plate and later also in hypertrophic chondrocytes close to the mineralization zone of the articular cartilage.

Animals↗
PubMed1986

[Lesions of the hip in congenital myxedema in children].

A series of 51 cases of congenital myxoedemia in children was analyzed to determine incidence of associated hip lesions. Mechanisms of epiphysial and articular cartilage growth are reviewed and events summarized that occur normally in the "growing hip": the upper femoral nucleus, and orientations of femoral neck and their physiologic variations. The role of thyroid hormones in bone growth is also discussed. Reviewed in greater detail are the myxedematous hips in children, or epiphysial dysgenesis, the causes of delay in bone maturation, the effect of substitutive therapy and mineralization disorders. In contrast to the richness of radiographic data, often very disturbing, restriction or even absence of functional signs is almost a constant feature, enabling a diagnosis of Legg-Perthes-Calvet's disease to be rejected, certain radiologic images being considered wrongly as comparable. Radiography provides images varying from delayed ossification of a sometimes very long upper femoral nucleus, termed "joint emptiness", to "pseudo-fragmentations" that are frequently encountered and are actually progressive ossifications. These sometimes progress towards deformity of femoral head in coxa plana but are usually well adapted to the acetabulum, reducing initial fears. Different parameters studied in the 51 patients are analyzed and an optimistic conclusion given, since neonatal screening for congenital myxedema and subsequent therapy should eliminate skeletal complications, particularly in the hip.

Adolescent↗
PubMed1966

Protein-polysaccharide loss during endochondral ossification: immunochemical evidence.

Fluorescein labeled antibodies to protein- polysaccharides from rat and calf cartilage were used for the histochemical localization of protein- poly saccharide in epiphyseal cartilage. There was less protein- polysaccharide in the zone of provisional calcification than in the proliferating and maturing zones, and none was demonstrable in the metaphysis. During or just preceding cal cification, protein- polysaccharide or its protein component is lost or drastically altered.

Animals↗
PubMed2003

Short-term glucocorticoid treatment of piglets causes changes in growth plate morphology and angiogenesis.

OBJECTIVE: Glucocorticoid treatment of children often leads to growth retardation, and the precise target(s) in the growth plate responsible for this effect are unknown. Angiogenesis is an important part of the endochondral ossification process, and VEGF expressed in the growth plate is essential for proper angiogenesis to occur. Since glucocorticoid treatment down-regulates VEGF expression in cultured chondrocytes, we hypothesized that in vivo glucocorticoid treatment could result in VEGF down-regulation in the growth plate and disturbed angiogenesis, thus contributing to the growth retardation. DESIGN: We treated 6-week-old prepubertal piglets (10 kg) for 5 days with prednisolone (50 mg/day). Tibial growth plate sections were studied for apoptosis and the expression of VEGF protein and mRNA and MMP-9 protein. Capillaries in the metaphysis were visualized by CD31 immunostaining. Growth plate morphology (width of various zones) was determined by interactive measurements on hematoxylin/eosin stained sections and apoptotic cells were detected by TUNEL assay. RESULTS: In the prednisolone-treated animals, the total width of the growth plate decreased to 81% of controls (P<0.02), which was explained by a decrease of the width of the proliferative zone to 73% (P<0.05). The treatment had no effect on the orderly organization of the chondrocyte columns. In the growth plates of control animals, apoptosis was shown in 5.8% of the hypertrophic chondrocytes and was limited to the terminal hypertrophic chondrocytes. In prednisolone-treated animals, 40.5% of the hypertrophic chondrocytes was apoptotic (P<0.02), with apoptotic chondrocytes also appearing higher in the hypertrophic zone. We observed fewer capillaries and loss of their parallel organization in the metaphysis in the prednisolone-treated animals. The capillaries were shorter and chaotic in appearance. In contrast to controls, in prednisolone-treated animals VEGF mRNA and protein could not be detected in the hypertrophic zone of the growth plate. Trabecular bone length in the primary spongiosa was also diminished by the treatment. No changes were observed in the expression pattern of MMP-9, a matrix metalloproteinase, which is also important for angiogenesis and bone formation. CONCLUSIONS: These results indicate that short-term glucocorticoid treatment of growing piglets severely disturbs the width of the growth plate, apoptosis of chondrocytes, VEGF expression by hypertrophic chondrocytes, the normal invasion of blood vessels from the metaphysis to the growth plate and bone formation at the chondro-osseous junction. These effects could alter the dynamics of endochondral ossification and thus contribute to glucocorticoid-induced growth retardation.

Animals↗
PubMed1998

Callotasis in nonvascularized periosteal bone grafts and the role of periosteum: a new contribution to the concept of distraction osteogenesis.

Bone lengthening by slow, progressive distraction has gained widespread acceptance. In this study we investigated the possibility of distraction osteogenesis in nonvascularized periosteal bone grafts, and assessed callus formation and callotasis by means of radiological and histological examination with the aim of determining the role of the periosteum. The process of distraction osteogenesis in nonvascularized bone grafts was studied histologically and radiologically in 22 growing rabbits. The metatarsal bone grafts taken from the rabbits were divided into two groups. Group 1 contained 15 bone grafts covered with periosteum and group 2 (the control group) contained 7 bone grafts without periosteum. These grafts were subjected to osteotomy and then placed in the lumbar pocket. After 10 days, distraction was started and continued at 0.5 mm per day for 10 days. Thus an elongation of 4 to 6 mm was achieved in both groups. Radiological examination was performed postoperatively and after 10, 15, 20, and 30 days of starting the distraction. Histological examination was performed after 15, 20, and 30 days. Radiologically, progressive calcification and, histologically, both intramembranous and endochondral ossification were detected in group 1. However, in the control group (group 2), bone lengthening failed. Our study demonstrated the possibility of distraction osteogenesis in periosteal bone grafts, and provides information regarding the importance of periosteum as well as its osteogenic capacity.

Animals↗
PubMed1977

The role of bone remodelling in the healing of extraction socket in rats.

Bone remodelling of post-extraction socket was studied in the past by various methods. In the present work, the process was studied with the scanning electron microscope (SEM). The SEM is essential for a three-dimensional description, particularly when hard tissues are involved. Initiation of healing on the first week was characterized by formation of delicate spongy bone. The trabeculae were distributed in a centrifugal pattern around the interradicular bone. Socket healing on the second week consisted of thickened, regularly distributed trabeculae. This was accompanied by resorption and flattening of the peri-socket sharp ridges. The third and fourth weeks were characterized by small bone marrow spaces and a gradual transformation of the trabecular bone to one of cortical-compact nature. The typical characteristics of resorbing, resting and forming surfaces were detected in all phases of socket healing. Two major patterns of ossification could be shown: Firstly, calcification of collagen bundles in osteoblastic lacunae. Concentrations of such lacunae were related to periosteal activity and were also found in areas most probably occupied previously by blood vessels. Another pattern of mineralization was in the form of globular calcospherites and is reminiscent of calcification of ground substance.

Alveolar Process↗
PubMed2004

Repair of bony defect with combination biomaterials.

BACKGROUND: Numerous possibilities are available for the reconstruction of facial bone defects. The materials used to fill such defects must satisfy various requirements. One of the most important is that they must undergo transformation into autologous bone tissue in the process of remodeling. AIM: A report is given of the long-term results of augmentations of large bone defects performed with different bone-substitute materials in two patients. PATIENTS AND METHODS: In one case, augmentation was carried out with beta-tricalcium phosphate after the removal of a fibromyxoma. In the second case, three large cystic lesions in the mandible of a patient with Gorlin-Goltz syndrome were filled with beta-tricalcium phosphate, with a mixture of beta-tricalcium phosphate and platelet concentrate, or with hydroxyapatite of algal origin. The process of ossification was checked at 6-month intervals by means of clinical, radiologic (orthopantomograms and two-dimensional and three-dimensional computer tomograms), and histologic methods. RESULTS: At 1 year after the intervention, the site of the augmentation was in all cases occupied by hard tissue of good quality. With the given imaging procedures, it was difficult to distinguish between the original bone and the region filled with bone-substitute material. The three-dimensional computer tomogram images indicated that the contours and quality of the new bone corresponded with the physiologic and anatomical conditions. The histologic examinations show the remodeling of the bone-substitute materials. DISCUSSION: The bone-substitute materials applied in these cases fully satisfied the demands of transformation into bone (remodeling). The speed of remodeling seemed to be the fastest when the mixture of beta-tricalcium phosphate and platelet concentrate was used.

Adolescent↗