Osseous Cells Research Articles

Ultrastructural analyses of the attachment (bonding) zone between bone and implanted biomaterials.

This report presents transmission electron and high voltage transmission electron microscopic observations of bone and associated remodeling tissues directly interfacing with endosteal dental implants. Undecalcified interfacial tissues were serially sectioned from mandibular samples encasing 60 implants placed into 30 dogs. Two-dimensional ultrastructural analyses and three-dimensional stereology showed that osteogenesis adjacent to dental implants is a dynamic interaction of osseous cells and a collagenous fiber matrix. This study showed that the interfacial bone consists of a mineralized collagen fiber matrix associated with an inorganic (hydroxylapatite) matrix. This study suggested that an unmineralized collagen fiber matrix initially is laid down directly at the implant surface, and that this matrix then is mineralized. Osteoblasts interacted with this matrix, eventually becoming encased within developing lacunae during the remodeling process. This process formed the cellular (osteocyte) aspects of the developed bone. Osteocyte processes extended through canaliculi directly to the implant surface. Apparently, these processes also were entrapped within canaliculi during the mineralization events. At times, these processes paralleled the implant surface. The bone-implant interfacial zone was primarily fibrillar (both mineralized and unmineralized) in morphology, with an electron-dense, ruthenium positive deposition. This electron-dense material was approximately 20 to 50 nanometers in thickness, and only this thin layer separated the remodeled mineralized bone from the implant.

Expression of basic fibroblast growth factor and transforming growth factor β1 in the inner ear of the human fetus

The expression and localization of bFGF and TGF-β1 in the inner ear of ten 10-29 week human fetuses were studied using the LSAB immunohistochemical technique referred to the method of Shi. The bFGF was strongly expressed in Corti’s organs, vestibule macula and ampullar crista. The color of the upper cells of Corti’s anlage was a little deeper than that of the basal cells. The hair cells and supporting cells in the matured Corti’s organ continued to have distinct expression. Sites such as spiral ganglion (SG) neurons, stria vascularis (SV) had positive expression. Some cartilaginous cells and osseous cells in the developing osseous labyrinthus had light expression. TGF-β1 was expressed in the epithelium of Corti’s organ, vestibule macula, and ampullar crista. Hair cell color had a tendency to become weak with the maturity of the sensory epithelium, SG neurons, SV and spiral prominence (SP) had the TGF-β1 expression too. The results indicated that bFGF and TGF-β1 had participated in the course of inner ear development. The bFGF is a strong mitogen. However in this experiment it was found that it had the effect to promote differentiation. TGF-β1 had double effect of promotion and inhibition on the proliferation and differentiation of cells. The expression of bFGF and TGF-β1 in SG neurons indicated that both factors had participated in the development of the nervous system of the inner ear.

OR 64 Cytotoxic responses of osseous cells to root canal obturating materials: W. R. Patton*, G.S. Schuster, R. J. Loushine, R. N. Weller, D.W. Craft. USA Dental Activity, Fort Gordon, Georgia and Medical College of Georgia, Augusta, Georgia

OR 64 Cytotoxic responses of osseous cells to root canal obturating materials: W. R. Patton*, G.S. Schuster, R. J. Loushine, R. N. Weller, D.W. Craft. USA Dental Activity, Fort Gordon, Georgia and Medical College of Georgia, Augusta, Georgia

Nucleolar localization of parathyroid hormone-related peptide enhances survival of chondrocytes under conditions that promote apoptotic cell death.

Parathyroid hormone-related peptide (PTHrP) is a mediator of cellular growth and differentiation as well as a cause of malignancy-induced hypercalcemia. Most of the actions of PTHrP have been attributed to its interaction with a specific cell surface receptor that binds the N-terminal domain of the protein. Here we present evidence that PTHrP promotes some of its cellular effects by translocating to the nucleolus. Localization of transiently expressed PTHrP to the nucleolus was dependent on the presence of a highly basic region at the carboxyl terminus of the molecule that bears homology to nucleolar targeting sequences identified within human retroviral (human immunodeficiency virus type 1 and human T-cell leukemia virus type 1) regulatory proteins. Endogenous PTHrP also localized to the nucleolus in osseous cells in vitro and in vivo. Moreover, expression of PTHrP in chondrocytic cells (CFK2) delayed apoptosis induced by serum deprivation, and this effect depended on the presence of an intact nucleolar targeting signal. The present findings demonstrate a unique intracellular mode of PTHrP action and a novel mechanism by which this peptide growth factor may modulate programmed cell death.

Transmission electron and high-voltage electron microscopy of osteocyte cellular processes extending to the dental implant surface.

Examination of the morphology of osteocytes within the bone supporting endosteal dental implants was performed using conventional transmission and high-voltage transmission electron microscopy (HVEM). The in vivo dog model used 72 implants inserted into the premolar region of 18 experimental animals. Forty-eight implants in 12 dogs were used as anterior abutments for fixed bridges for periods up to 12 months. The mineralized matrix of the supporting bone was either directly apposed to the implant surface or was separated from the implant by a narrow region of unmineralized matrix. Osteocytes were routinely observed to be closely associated with the bone-implant interface, as well as at a distance from the implant. Osteocytes were found to extend cellular processes directly to the implant surface through canaliculi. The osteocyte processes contained microfilaments. The three-dimensional capabilities of HVEM elucidated the nature of these cell processes at the point of exit from the osteocyte, as the processes extended through the mineralized matrix, and as the processes terminated at the implant interface. This report suggests that avenues of communication may exist between the implant and the osseous cells, providing intriguing hypotheses regarding biomechanical forces and osteogenesis at the implant interface. Furthermore, an electron-dense deposit was observed upon the inner confines of the canalicular wall, upon the outer aspects of the osteocyte lacuna, and upon the outer aspect of the bone interfacing the implant.

Osteoblast Activity at the Dental Implant‐Bone Interface: Transmission Electron Microscopic and High Voltage Electron Microscopic Observations

The purpose of this report is to present transmission electron microscopic and high voltage transmission electron microscopic (HVEM) observations of a longitudinal investigation examining the activities of osteoblasts and associated tissues apposing titanium and alumina oxide ceramic endosteal dental implants. The HVEM permitted 3-dimensional stereologic observations. All observations were obtained from undecalcified interfacial tissues from this in vivo experimental dog model using commercially available implants placed into the mandible. Two similar implants were placed in both sides of the mandible, with implants in 12 of the 18 dogs supporting fixed bridges for either 6 or 12 months. From the study, we observed that a mineralized matrix exists in direct apposition to the implant. Since bone does not interface the entire length of the implant, other interfacial zones were found to exist which consisted of unmineralized tissues. In such zones, we observed that osteoblasts were routinely found directly at the implant interface to the mandibular bone. These interfacial tissues included unmineralized collagen fibers, proteinaceous material, a finely fibrillar matrix, and the osteoblasts. This study has reinforced the concept that the oral tissue-dental implant interface is a dynamic zone consisting of remodeling activities of the osseous cells and extracellular matrices.

Effect of protein and steroidal osteotropic agents on differentiation and epidermal growth factor-mediated growth of the CFK1 osseous cell line.

The effects of factors known to influence bone metabolism were examined using the osseous cell line CFK1. Parathyroid hormone (PTH) and dexamethasone (DEX) appeared to enhance the formation of cell foci of CFK1 cells in culture whereas retinoic acid (RA) caused a marked alteration in individual cell morphology. Bone morphogenetic protein (BMP-2) and PTH increased alkaline phosphatase activity, however, this index of differentiation was suppressed by epidermal growth factor (EGF), DEX, and RA. BMP-2 and EGF each stimulated DNA synthesis in a dose-dependent manner and enhanced cell numbers, but, no synergistic response of EGF and BMP-2 was observed. PTH and DEX failed to significantly alter cell number or EGF-stimulated DNA synthesis or cell proliferation. Although RA treatment of CFK1 cells resulted in a reduction in cell number compared to control, pretreatment with RA enhanced EGF-stimulated DNA synthesis and proliferative effects. At least part of this effect was by increasing the EGF receptor binding capacity of the cells. Furthermore, using cell cycle analysis, addition of EGF stimulated the progression of RA-treated cells into the DNA synthesis (S) phase with a reduced lag time. EGF and BMP-2, therefore, appear to exert a role in the expansion dynamics of the CFK1 population although BMP-2 may also enhance differentiation. PTH and DEX may act primarily to modulate the differentiated function of the CFK1 cells. RA inhibited cell proliferation and may mediate differentiation towards a less established cell population with upregulation of EGF receptors. The CFK1 cell model may, therefore, provide insight into microenvironmental control of growth and differentiation of precursor osseous cells.

局所自家骨小片移植に関する病理組織学的研究

The author performed enucleation of the tooth germ in the 4th premolar of mandible of young adult dogs and grafted local autogenous bone chips. Observations by tetracycline labelling and microradiogram were made of the changes in the grafted bones and the recipient bones. Pathohistological investigations were also made of the non-decalcified and decalcified stained specimens. The results were as follows : 1. In the decalcified stained specimens, the formation of trabeculae from the wall of the defect into the cavity was observed on the 5th day after grafting, and the defect was filled with the new bone to the 30th day. These findings were the same as the non-decalcified findings in the tetracycline labelling and the microradiogram. 2. A slight bone neogenesis was seen taking place in the peripheries of the transplanted bone chips on the 5th day after grafting. On the 10th day, tetracycline labelled layer was found in the peripheries of the little transplanted bone chips. In microradiographic findings, it was recognized to be radiopaque. The new bone in the peripheries of the transplanted bone chips was connected with the new bone from the wall of the defect on the 15th day and the defect space was filled with the retiform new bone. 3. The nuclei of the osseous cells of the transplanted bone chips began to atrophy and disappear on the 5th day, and the osseous cells decreased and disappeared gradually by the 20th day. On the 30th day, the small cavities of the transplanted bone chips were found to be vacant. 4. The fibrous connective tissues and capillaries invaded into the Haversian canal of the transplanted bone chips on about the 15th day. On the 20th day, a new formed trabeculae was formed in the Haversian canal. And the formation of the new bone started from inside the transplanted bone chips. 5. Repair of the newly formed bone began on about the 30th day, and the osseous cells were arranged regularly, and the width and calcification of the trabeculae increased. This repair continued to the 90th day. 6. In the present experiment, the transplanted bone chips did not show the capacity for osteogenesis, but had the capacity to stimulate the peripheral soft tissues to regenerate bone. And they seem to have some part in osteogenesis and in bone union with the recipient bone. The repair of the transplanted bone chips was mainly a latent displacement.

Cartilage and bone formation in arterial wall. 2. Ultrastructural patterns.

The ultrastructural aspects of cartilaginous and osseous foci developed in aorta of rabbits immunized against rat aorta homogenates was studied. Besides normal and modified smooth muscle cells, various types of transformed mediacytes were observed in and around these foci: some of them resembled connective and young mesenchymatous cells, others had the appearances of cartilaginous and osseous cells. The possible role of the modified (multipotential) smooth muscle cells in aortic chondro- and osteogenesis is considered in some cases. Following histogenetic pathway is suggested: s.m.c. leads to modified s.m.c. lead to young mesenchyme-like cells ("inducible osteogenic precursor cells") leads to "chondro-mediacytes", "osteomediacyte".

Generation of electric potentials by bone in response to mechanical stress.

The amplitude of electrical potentials generated in stressed bone is dependent upon the rate and magnitude of bony deformation, while polarity is determined by the direction of bending. Areas under compression develop negative potentials with respect to other areas. Similar results were obtained both in living and dead bone. Removal of the inorganic fraction from bone abolishes its ability to generate stress potentials. It is probable that these potentials influence the activity of osseous cells directly. Furthermore, it is conceivable that they may direct, in some manner, the aggregation pattern of the macromolecules of the extracellular matrix.

Chondromas and chondrosarcomas of the scapula and the innominate bone.

THE CHONDROMA in its pure form without any osseous cells may be one of the most troublesome of bone tumors. Because of its cellular nature, its occasional failure to be revealed in roentgenograms and its tendency to extend locally beyond borders which are at best not easily discerned on macroscopic inspection, it becomes a difficult tumor to handle surgically. Add to this the fact that at times some areas of these tumors may be undergoing malignant change while others appear benign and that there is a widespread belief that some of these tumors, apparently benign when first seen, may actually undergo malignant degeneration, and one has an even more serious problem. Coley1made a distinction in chondrosarcomas, classifying some as primary and others as secondary. The latter type results from a malignant alteration in the cells of a cartilaginous exostosis, a central chondroma or rarely in a patient who