Immature Bone Formation Research Articles

Reconstruction of Rabbit Experimental Mandibular Defect with rhBMP-2 and Atelocollagen Gel-.MU.CT Observation in Vivo and Histological Examination-

A rabbit experimental mandibular defect was reconstructed with rhBMP-2 and atelocollagen gel, and examined using μCT (R_mCT, Rigaku Mechatronics, Tokyo) in vivo and histological techniques. Using eight rabbits, we made an experimental mandibular defect and filled it with 1% atelocollagen gel including rhBMP-2 10ig (Astellas Pharma Inc.). In μCT observation, the density was slightly elevated at the bone marrow side at one week, and the phenomenon gradually expanded during the course of this experiment. Histologically, mesenchymal cell proliferation and immature bone formation occurred at one week, and mature bone gradually increased and filled in at four weeks.

実験動物用マイクロＣＴを用いたｒｈＢＭＰ‐２・アテロコラーゲンゲルによるウサギの顎骨欠損部再建の経時的観察

A rabbit experimental mandibular defect was reconstructed with rhBMP-2 and atelocollagen gel, and examined using μCT (R_mCT, Rigaku mechatronics, Tokyo) in vivo and histological techniques. Using eight rabbits, we made an experimental mandibular defect and filled it with 1% atelocollagen gel including rhBMP-2 10μg (Astellas Pharma Inc.). In μCT observation, the density was slightly elevated at the bone marrow side at day 5, and the phenomenon gradually expanded during the course of this experiment. Histologically, mesenchymal cell proliferation and immature bone formation occurred at one week, and mature bone gradually increased and filled in at four weeks. The histological data suggests that atelocollagen gel is effective as carrier of rhBMP-2. The μCT observation is extremely useful for follow-up of such reconstruction of animal bone defect model.

In vivo mesenchymal cell recruitment by a scaffold loaded with transforming growth factor beta1 and the potential for in situ chondrogenesis.

The objectives of this study were (1) to develop a biphasic implant made of a bioresorbable polymeric scaffold in combination with TGF-beta1-loaded fibrin glue for tissue-engineering applications, and (2) to determine whether the implant made of a polycaprolactone (PCL) scaffold and TGF-beta1-loaded fibrin glue could recruit mesenchymal cells and induce the process of cartilage formation when implanted in ectopic sites. Twenty-four 6-month-old New Zealand White rabbits were used. Scaffolds loaded with various doses of TGF-beta1 in fibrin glue were implanted subcutaneously, intramuscularly, and subperiosteally. The rabbits were killed and implants were removed at 2, 4, and 6 weeks postoperatively. The specimens were subjected to various staining techniques for histological analysis. Light microscopic examination of all specimens revealed that the entire pore space of the scaffolds was filled with various tissues in each group. The entire volume of the scaffolds in the groups loaded with TGF-beta1 and implanted intramuscularly and subcutaneously was populated with mesenchymal cells surrounded with an abundant extracellular matrix and blood vessels. The scaffold loaded with TGF-beta1 and implanted subperiosteally was found to be richly populated with chondrocytes at 2 and 4 weeks and immature bone formation was identified at 6 weeks. We conclude that scaffolds loaded with TGF-beta1 can successfully recruit mesenchymal cells and that chondrogenesis occurred when this construct was implanted subperiosteally.

High-turnover periprosthetic bone remodeling and immature bone formation around loose cemented total hip joints.

Aseptic loosening and periprosthetic osteolysis are the major problems awaiting solution in total hip surgery. The clinical investigation focused on the analysis of periprosthetic bone remodeling to clarify one important key event in the cascade of periprosthetic connective tissue weakening and osteolysis around loose artificial hip joints. Twelve acetabular bone samples adjacent to granulomatous synovial-like membrane of loose hip prosthesis were retrieved at revision surgery and processed for Villanueva bone staining for morphological observation and bone histomorphometric analysis. Eight well-fixed bony samples were used as control. Although osteoclastic surface and eroded surface by osteoclasts were evident in the periprosthetic bone from loose hip joints (p = 0.003 and p = 0.027), increased osteoid/low-mineralized bone matrix (p < 0.001) and osteoid width (p < 0.001) also were significant findings in structural analysis. In addition, not only elevated mineral apposition rate (MAR; p = 0.044) but also increased mineralizing surface (p = 0.044) and bone formation rate (BFR; p = 0.002) in loose periprosthetic bones were shown in dynamic data analysis. These results were confirmed by precise morphological observation by confocal laser scanning microscopy. Active coupling of bone formation and resorption and increased osteocytes with abundant bone canalicular projections were found in combined with the presence of immature bone matrices (osteoid and low-mineralized bone areas) in periprosthetic bones from loose hip joints. These results indicated that active osteoclastic bone resorption and/or defective bone formation are coupled with monocyte/macrophage-mediated foreign body-type granuloma in the synovial-like interface membrane of loose hip joints. Thus, this unique high-turnover periprosthetic bone remodeling with bad bone quality probably is caused by the result of cellular host response combined with inappropriate cyclic mechanical loading. The fragile periprosthetic bone may contribute to hip prosthesis loosening.

Effect of a poly(propylene fumarate) foaming cement on the healing of bone defects.

Regeneration of skeletal tissues has been recognized as a new means for reconstruction of skeletal defects. We investigated the feasibility of an injectable and expandable porous implant system for in situ regeneration of bone. Therefore, a composite biodegradable foaming cement based on poly(propylene fumarate) was injected into a critical size defect made in the rat tibia. Animals were divided into two groups comparing the foam in the experimental group against sham-operated animals having a drill hole but no implant in the control group. Eight animals were included in each group. Animals were sacrificed at 1, 3, and 7 weeks postoperatively. Implantation sites were then evaluated with histologic and histomorphometric methods. Results of this study showed that defects did not heal in sham-operated animals. In the experimental group, metaphyseal and cortical defects healed within the first postoperative week by formation of immature woven bone. At the site of the cortical drill hole defect, healing was noted to progress to complete closure by formation of mature bone. Histomorphometry corroborated these findings and showed that metaphyseal bone remodeling peaked at 1 week postoperatively and then decreased as healing of the cortical defect progressed. This suggests that near-complete restoration of the original state of the tibial bone occurred in this animal model supporting the concept of in situ bone regeneration by application of engineered biodegradable porous scaffolds. () ()

THE ETIOLOGY OF KIENBÖCK'S DISEASE — A HISTOPATHOLOGICAL STUDY

The etiology of the necrosis of the lunate bone is still unclear. In today's theories, the necrosis is explained by impairment of the arterial bone circulation or fracture following mechanical overloading. In this study, six specimen in different stages of the disease were investigated histologically. In all the specimens, focal necrosis was detected, but also signs of regeneration, i.e. immature bone formation. No signs of fracture were seen in all stages of the disease. These findings are not compatible with sudden interruption of arterial blood supply or fracture of the lunate bone as a primary lesion. Comparable histological patterns are known in the necrosis of the femoral head. The etiological model of necrosis of the femoral head is well investigated and postulates primary marrow hypertension, induced by impairment of the venous drainage. Our results are contradictory to the etiological theories of fracture or breakdown of the arterial blood supply as a primary lesion in Kienböck's disease, and support the assumption that the model of intraosseous hypertension is transferable to the necrosis of the lunate bone.

Stereomorphologic observation of bone tissue response to hydroxyapatite using SEM with the EDTA-KOH method.

To obtain further information on the interaction of hydroxyapatite (HA) and the bony implantation bed, 20- to 40- mesh dense HA particles were implanted into the tibiae of dogs. Following healing periods of 2 weeks, 1 month, and 3 months, the specimens were retrieved and prepared by either conventional preparatory procedures for scanning electron microscopy (SEM) of the EDTA-KOH method. Under SEM observation, the interparticular osteogenesis among HA particles progressed in a programmed sequence. Ample blood supply and osteoblasts initially presented in the interparticular space. The secretion of bone matrix resulted in the formation of immature bone. This scaffold was then transformed into mature lamellar bone during the following bone remodeling process. The serial changes closely resembled the pattern viewed in controls that did not implant HA. A spatial relationship between bone cells and HA was clearly demonstrated. In particular, the osteoblasts displayed an extremely flat appearance with many microappendages. The microappendages anchored cells to the HA surface and fused with granular material covering the HA crystals. The more characteristic cellular morphology was revealed by the EDTA-KOH method. Microscopic pictures clearly identified the three-dimensional images of ruffled borders of osteoclasts and the slender cytoplasmic processes of osteocytes. This study provided further evidence for the favorable biological response of HA to bone cells as well as the value of the EDTA-KOH method in examining the stereomorphology of bone cells.

Reaction of Hydroxyapatite-Sol in Bone Marrow

Hydroxyapatite-sol was prepared by dispersing hydroxyapatite microcrystals into saline. The hydroxyapatite microcrystals were synthesized by neutralization reaction of calcium hydroxide suspension and phosphoric acid solution. Sizes of the hydroxyapatite microcrystals were less than 0.1 microns, and the mean value was 0.05 microm. The 0.2 ml hydroxyapatite-sol with a concentration of 14.8 mg/ml was injected into medullary cavities of rat femurs. Both sintered hydroxyapatite powder suspension and saline as comparative materials were injected into the medullary cavities in the same way. Reaction of the hydroxyapatite-sol in the bone medullary cavities was investigated histologically using light and transmission electron microscopes. After 3 days, new bone formation was observed by injection of hydroxyapatite-sol, while no bone formation was observed by injection of sintered hydroxyapatite powder and saline. Osteoblasts were observed endocytosing the hydroxyapatite-sol in the medullary cavities of the rats. Macrophages and undifferentiated osteoblasts were found around the hydroxyapatite-sol aggregation by transmission electron microscope. After 5 days, amounts of new bone increased and matured, forming trabeculae. Many osteoblasts were observed in a line along the surface of the bone. On the other hand, 5 days after injection of sintered hydroxyapatite powder and saline to bone formation was observed while at 10 days after injection, some immature new bone formation started to be observed. New bone increased and matured at 15 days postoperatively. From these results, it was concluded that hydroxyapatite-sol only quickly promotes the formation of new bone in bone marrow and can be used as injection liquid of new biomaterials for bone formation.

The Osteogenic Activity of Bone Removed From Healing Extraction Sockets in Humans

Cores of bone from healing extraction sites were studied at time intervals of 4, 6, 8, 10, 12 and 16 weeks. The results revealed that between 4 and 8 weeks proliferation of cellular and connective tissue elements occur within the healing socket. Islands of new bone with an osteoid seam surrounded by osteoblasts are present within the connective tissue. From 8 to 12 weeks the bone undergoes maturation and forms a trabecular pattern. Although less pronounced, and osteoid seam is still present and osteoblasts occur in fewer numbers. By 12 to 16 weeks the bony trabeculae are mature with very little osteoid and few osteoblasts. This bone resembles alveolar trabecular bone. Two phases of bony regeneration are apparent from the present study. From 4 to 8 weeks there is a progressive osteogenic phase with proliferation of osteogenic cells and immature bone formation. From 8 to 12 weeks the osteogenesis slows down and the trabeculae mature and increase in volume. From 12 to 16 weeks the bone appears to stabilize with an established alveolar trabecular bone being present. Very little osteogenesis occurs as evidenced by minimal or no osteoid seam with only occasional osteoblasts. It is apparent that in the period between 8 and 12 weeks a substantial quantity of relatively mature well formed bone is present which contains osteoblasts and an osteoid seam. This appears to be an optimal time period to secure bone from a healing extraction site for grafting purposes.

抜歯後における下がく骨の経時的変化

Histological changes in the mandibular tissue after tooth extraction was investigated to learn about the clinical application of the apatite ceramics mplant. The M1 M2 or P2 M1 M2 M3 from twenty adult monky mandibles were observed for 1 week to 2 years and 3 months. After 1 week, immature bone formation began already at the base of the socket and the surrounding marrow space. After 1 month, the new bone filled most of the socket at the same time the resorption of the new bone and socket wall occurred at the base of the socket. After 3 months, the bone condensed at the surface of the mandible forming the rudimentary cortex, but the resorption of the new bone and wall progressed so that the socket outline became indistinct. After 6 months, the bone at the surface had a more cortex-like appearance and most of the new bone and wall disappeared except for the thick bone of the original spongiosa which was resorbed leaving a few thin trabeculae inside the mandible 1 year after the tooth extraction. After 1 year, the bone formation at the surface ended, but it didn't reach the state of the original cortex. Thereafter, no changes occurred in both areas until 2 years and 3 months after the tooth extraction.

Biochemical changes in bone grafts stabilized with rigid plates. II. Cortical grafts.

The effect of rigid plate fixation on the chemical composition of cortical interposition grafts were studied in rabbit tibio-fibular bones. The concentration of hexosamines increased both in the graft and in the host bone during the first 6 weeks, but thereafter decreased. The concentrations of hydroxyproline and nitrogen increased throughout the experiment. The ratio of hexosamines to hydroxyproline increased in the graft for the first 6 weeks, indicating formation of immature osteoid and bone during this period, but thereafter decreased. The calcium concentration of the graft decreased significantly during the first 12 weeks and remained below normal (-10 to -19 per cent). The mineralization of the graft, assessed by the ratio of calcium to hydroxyproline, decreased continually. The results suggest that cortical bone grafts stabilized with rigid plates heal with only slight chemical signs of callus formation. The demineralization of the graft reflects the porotic changes that take place under the plate.

The postnatal development of the human temporomandibular joint

AbstractFifty‐one temporomandibular joints (24 male, 27 female) obtained at autopsy were used in the study. Forty‐four specimens were younger than ten years while others ranged to 21 years. These joints were radiographed, sectioned sagittally or frontally, and slide‐mounted as decalcified and undecalcified sections using conventional histologic techniques. The slides were examined microscopically in whole, polarized, and ultraviolet light. Two of the specimens surveyed exhibited fluorescent labeling as a consequence of therapeutic tetra cycline application.Throughout the postnatal developmental period the articular tissue and disc consist of fibrous connective tissue. Cartilage cells were not observed in these structures at any time during the twenty‐one year age‐span studied. At birth the disc is flat and develops an accentuated S‐shaped profile as the articular tubercle develops.The articular tubercle is only a small elevation at birth and is formed by a combination of endochondral, immature, and ordinary intramembranous bone formation. The characteristic profile of the temporal portion of the joint is achieved during the first two or three years of life, after which gradual enlargement and compaction of bony structures occur.While the mandibular condyle grows in a constant posterior, superior, and lateral direction, it does not attain its mature contour until the late mixed dentition age. Condylar growth cartilage is approximately 1.5 mm thick at birth but it thins down in a short time to about 0.5 mm. During the first two years of life the growth cartilage is penetrated by vascularized connective tissue septa whose function appears to be nourishment of the cartilage. The growth cartilage does not show the columnar arrangement of chondrocytes seen in epiphyses, nor are isogenous groups observed. At 16 to 17 years, the growth cartilage becomes thinner and a closing plate of bone is beginning to coalesce below it.

放射線照射下顎骨の即時再移植に関する研究 : 第 2 編 実験的研究

According to Hirakawa and his associates, the healthy bone chips obtaind from areas surrounding osseous lesion of the mandible and alveolar bone were used to fill defects following enucleation of bone lesions. But they didn't applied to malignant tumors because to be in danger of transportation and survival of tumorous cells. Author supposed to this unsolved problem that the transportation and survival of tumorous cells were suppressed by X-ray irradiation and tried follwing experimental research. Bone block and bone chips after 5000R single irradiation were immediately transplanted into the artificial bony cavity in dog's mandible. Author reported the roentogenologic and histopathological observation which revealed the process of the healing. The results were summarized as follows ; 1. From 7-10days to 20-30days after operation, resorption of implants was observed both in bone block group and bone chips group. Further atrophy and disappearance of osteocytes of the implant was more seen in irradiated case than control case. 2. Immature bone formation in bone chips group appeared at about 20days after operation and it was seen early in comparison with bone block group. Moreover vigorous neogenesis of bone fused and surrounded gradually the implants and led to the restoration of the bony defect. The bony healing carried out almost in 60days and accomplished perfectly in 120days after operation, but the healing process in irradiated case was late for time each steps compare with control case. 3. The healing process of the dog's retransplanted mandibular pieces after 5000R single irradiation showed to be similar to the findings of control case with slight delay for time. Author recognized that the irradiated mandibular pieces played the part of implant material finally.

The effect of hypovitaminosis a on bone healing and endochondral ossification in rats

The present study of bone behavior in vitamin A deficiency is based upon histologic and roentgenographic examination of the healing tooth sockets and the tibias of young male rats fed a purified diet deficient in vitamin A. After about thirty to thirty-five days on the experimental diet a clear-cut vitamin A deficiency was established and suboptimal maintenance does of vitamin A had to be administered in order to keep the animals alive. The main changes observed were as follows: 1. 1. Osteoblastic activity decreased, as evidenced by a considerable retardation of the formation of immature bone in the healing tooth socket. 2. 2. Ostcoclastic activity was suppressed or entirely about. This was clearly illustrated by the failure of remodeling resorption of the immature bone formed in the sockets of the deficient animals and by the failure of the remodeling of the tibial shaft. This lack of resorption was considered to be the mechanism responsible for the main changes in bones seen in vitamin A deficiency. 3. 3. The immature bone formed in the vitamin A-deficient rats contained more and larger osteocytes than the immature bone of the controls, and their cytoplasm and cell membrances were distinctly basophilic.