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The ability of PGE2 to stimulate bone resorption in vitro and in vivo is well established but the effects of this compound on bone formation are still controversial. Recent clinical reports have suggested that long-term infusion of PGE in infants with cyanotic heart diseases led to a stimulation of periosteal bone formation and to hyperostosis. In the present report, we describe the effects of PGE2 (10(-5) M) in bone organ cultures on bone resorption, measured by the release of 45Calcium and the number of osteoclasts in sections of cultured bones, and bone volume, by measuring separately medullary and cortical areas. PGE2 induced a marked increase in 45Ca release and in cortical and medullary osteoclast numbers over 4 days in vitro; despite this increase in bone resorption, cortical bone volume remained constant, indicating a parallel increase in bone resorption and formation at this site. Morphological and quantitative data demonstrated a higher extent of osteoblastic surface along the periosteum of PGE2-treated bones when compared with control cultures. Medullary bone volume, on the other hand, decreased sharply during the culture period, demonstrating a lack of parallel increase in bone formation at this site. It is concluded that, under these experimental conditions, prostaglandin E2 stimulated both resorption and formation along the periosteum and only bone resorption along the endosteum of the cultured bones. The overall effect of PGE2 on bone as a whole, however, was net bone loss.
Anat Rec 1985 Jan
PMID:PGE2 stimulates both resorption and formation of bone in vitro: differential responses of the periosteum and the endosteum in fetal rat long bone cultures. 398 83

Nerves exhibiting substance P-like immunoreactivity were demonstrated in the human periosteum. A network of nerves showing substance P-like immunoreactivity was seen in the periosteum, while finer strands of immunoreactive nerve fibers were present immediately beneath the surface of the periosteum. Enkephalin-like immunoreactivity was also studied but could not be demonstrated. Substance P has previously been suggested to be involved in the mediation of the sensation of pain. The clinically observable marked pain sensitivity of periosteal tissue might be explained by the peptidergic nerves described in this paper.
Anat Rec 1984 Jul
PMID:Innervation of human bone periosteum by peptidergic nerves. 620 9

The kinetics of the bone remodeling sequence in the rat has been studied using a system in which well-synchronized remodeling units were induced along the periosteum of rat mandibles. Remodeling of the periosteal surface of the mandibles was induced according to Tran Van (1979) by extraction of the opposing row of teeth; namely, the right maxillary molars were extracted under light ether anesthesia, therefore allowing the right mandibular molars to egress; this, in turn, induced a wave of remodeling activity on the buccal side of the periosteal surface of the alveolar bone. The quantification of the different cellular activities involved in bone remodeling has been performed up to 16 days after induction. This allowed us to demonstrate the sequential activity of the different cell types involved in bone remodeling, to study the cellular kinetics of this sequence of events, and to directly measure the duration of each phase of the bone remodeling sequence. A single wave of osteoclasts appeared 3 days after induction, reached a peak of 4-5 days, and then decreased sharply. This was followed by a single wave of mononuclear cells (Baron et al., 1980) within remodeling sites during the reversal phase; they appeared 4 days after induction, reached a peak by day 7, and then decreased sharply. This reversal activity was then followed by osteoblasts forming new bone on top of a reversal cement line in the remodeling sites, starting 6 days after induction and increasing until the end of the experiment. In addition, the synchronization of the system used in this study allowed direct measurement of the duration of the successive steps of the remodeling sequence. The directly measured values have then been compared to previous data calculated from other systems.
Anat Rec 1982 Apr
PMID:Cellular kinetics of the bone remodeling sequence in the rat. 707 87

During growth the muscles of mastication alter their lines of action. Research on long bones indicates that the apparent migration of muscle attachments is due to the movement of the periosteum relative to the underlying bone. To assess whether the pig masseter muscle follows the periosteum during growth, implants of titanium granules in a gelatin matrix were placed simultaneously in various parts of the masseter muscle and its periosteal and bony attachments. Growth movements of these tissues were followed radiographically for 2 months. Granule position was verified histologically. Periosteal movement was the dominant growth process at the insertion of the masseter. All implants migrated caudally relative to the mandible. However, a strong position effect was seen dorsoventrally: implants placed high in the ascending ramus migrated dorsally as well as caudally; low implants migrated only caudally. This differential migration, ascribed to the influence of the condyle, accounts for the increasing horizontal orientation of dorsal fibers. A similar differential was seen along the rostrocaudal axis of the ramus. In contrast to the insertion, the origin of the masseter from the zygomatic arch shows no periosteal movement. Rather, the entire bone-muscle complex becomes displaced by sutural growth, leading to increasing vertical orientation of the masseter. Thus two different aspects of skull growth are responsible for the change in muscle anatomy.
Anat Rec 1993 Feb
PMID:Bone growth and periosteal migration control masseter muscle orientation in pigs (Sus scrofa). 842 Mar 91

Previous studies using light microscopy have revealed that histogenesis of deer pedicle and antler has four ossification stages. The first of these stages is the development of the permanent pedicle. Initial development of the pedicle is from the cellular layer cells of the antlerogenic periosteum and these cells have been termed initial antlerogenic cells (IACs). Apart from the IACs, it has also been shown that the cellular layer cells of the apical periosteum/perichondrium, the peripheral periosteum of pedicles or antlers, and the marginal periosteum surrounding the pedicles are also capable of either partially or fully generating a pedicle or an antler. Therefore, these cells can all be considered antlerogenic cells and called apical antlerogenic cells (AACs), peripheral antlerogenic cells (PACs), and marginal antlerogenic cells (MACs), respectively. The aim of this study was to examine the ultrastructure of these antlerogenic cells, and to determine whether there were ultrastructural correlates with the changes of these antlerogenic cells and ossification stages. The ultrastructure of each type of antlerogenic cells was systematically examined using transmission electron microscopy, at each stage of pedicle and first antler growth. At the first ossification stage, the IACs were spindle-shaped and inactive. The most obvious feature was the presence of abundant intracellular glycogen. The MACs were similar to the IACs. During the early second stage, most of the AACs changed in appearance from preosteoblasts to prechondroblasts. Much less heterochromatin was found in the AACs than in the IACs. The most striking attribute of the AACs was the existence of intracellular collagen fibers. The MACs showed abnormal dilation of the rough endoplasmic reticulum (RER). During the late second stage, the majority of the AACs were prechondroblasts. AAC nucleoli were clearly discernible and the cisternae of the RER were arranged in parallel. The MACs contained a greater proportion of abnormally-dilated RER. During the third stage, the AACs were all prechondroblasts. The Golgi apparatus in these cells was well developed. Many free ribosomes in rosettes were scattered in the cytoplasm. Most cytoplasm of the majority of the MACs was occupied by abnormally-dilated RER (the lumen of the RER was extremely dilated and appeared electron-lucent). During the fourth stage, the AACs were similar to their counterparts from the third stage, but the boundaries of some AACs were ill-defined. Some MACs were found to be undergoing apoptosis. The PACs were becoming less and less active from distal to proximal along the shaft of the antler. It is a novel finding that antlerogenic cells change in appearance and subcellular content from preosteoblasts to prechondroblasts prior to the transition from intramembranous to endochondral ossification during pedicle formation. Therefore, the differentiation process from antlerogenic cells to chondroblasts is a matter of maturation from prechondroblasts to chondroblasts. The fact that the antlerogenic cells are rich in glycogen makes them more like embryonic cells. The local membrane deficiency of some AACs at the fourth stage and the presence of mature collagen fibrils within the AACs may reflect the unusually high demand for collagen fibrils during the period of rapid antler growth.
Anat Rec 1998 12
PMID:Electron microscopic studies of antlerogenic cells from five developmental stages during pedicle and early antler formation in red deer (Cervus elaphus). 984 9

Our previous studies demonstrated that the octacalcium phosphate (OCP) causes new appositional bone formation on the OCP when implanted into the subperiosteal region of murine calvaria. The OCP may stimulate the cell population committed to the osteoblastic differentiation in the periosteum and have them express the phenotype. The present study was designed to investigate which periosteal cell population is involved in bone formation on the OCP with applying the OCP implants on top of and underneath the periosteum. The periosteum of the rat parietal bones was flapped and the OCP was implanted on top of or underneath the periosteum, in which the implantation sites were defined using the membrane filter. The histology was examined to see if new appositional bone formation occurs on the OCP implant under each condition. New bone was deposited on the OCP on the bone surface separated from the periosteum by the filter, whereas no bone was formed either under the periosteum separated from the bone surface by the filter or on the periosteum. The present study suggests that the OCP acts on osteoblasts, bone lining cells and/or their closely committed progenitors on the bone surface to express the phenotype and deposit new bone on the OCP implant.
Anat Rec 1999 09 01
PMID:Implanted octacalcium phosphate (OCP) stimulates osteogenesis by osteoblastic cells and/or committed osteoprogenitors in rat calvarial periosteum. 1045 79

Pluripotent cells from the periosteal layer adjacent to cortical bone attain an osteoblast-like phenotype in culture when reaching confluence in monolayer. It is unknown whether such newly differentiated osteoblast-like cells preserve the chondrogenic potential characteristics for stem cells derived from the periosteum. Primary osteoprogenitor cells derived from bovine metacarpal periosteum were differentiated into alkaline phosphatase-positive osteoblast-like cells by an established monolayer culture protocol. After transfer into suspension culture in agarose gels, the cells differentiated into chondrocytes demonstrated by the production of collagen II, but not of collagen I, as well as alkaline phosphatase activity was abated. Contrarily, with continuation of monolayer culture, the cells maintained their osteoblast-like phenotype and secreted large amounts of collagen I and a minor quantity of collagen III and V. The alkaline phosphatase activity steadily increased during the entire culture period of 2 weeks. Thus, our culture techniques can serve as useful tools to study mechanisms of differentiation by modulating the phenotypic potential of osteogenic cells. The results presented here support the notion that the extracellular environment strongly influences the cell type and its metabolism.
Anat Rec 2000 06 01
PMID:Periosteally derived osteoblast-like cells differentiate into chondrocytes in suspension culture in agarose. 1082 Mar 14

Lower numbers of neuropeptide-containing fibers in arthritic joints have been found as compared to control joints. This may be the result of fiber depletion, necrosis of fibers, or proliferation of soft tissues without neural sprouting. To discriminate between these possibilities, we studied the relationships between soft tissue proliferation, changes in vascularity of synovial tissues, and changes in joint innervation during arthritis. Arthritis was induced in the knee joint of mice by a single subpatellar injection of methylated bovine serum albumin after previous immunization. Antibodies to protein gene product 9.5, S-100, and growth-associated protein-43 (GAP-43) were used to study the general innervation pattern. Antibodies to calcitonin gene-related peptide (CGRP), vasointestinal polypeptide (VIP), substance P (SP), and tyrosine hydroxylase (TH) were used to localize sensory (SP, CGRP, VIP) and sympathetic (TH) fibers. Blood vessels of the joint were studied with ink perfusion, GAP-43, and a vascular marker (LF1). Directly after the induction of arthritis, the synovial cavity was enlarged and filled with leukocytes. From day 4 onward, small sprouting blood vessels penetrated the avascular mass of cells in the joint cavity. After 1 week, the vascular sprouting activity and GAP-43 immunoreactivity were maximal, and after 2 weeks, vascular sprouting activity diminished. In the subsequent period, the synovia slowly regained their prearthritic appearance and thickness. The most pronounced changes in the general staining pattern of CGRP, SP, VIP, and TH were found in the periosteum. From 2 days to 4 weeks after the induction of arthritis, the layer of SP, CGRP, and VIP fibers in the femoral periosteum was thicker and more irregular. GAP-43 staining showed many terminal varicosities, which suggested sprouting of nerve fibers. From 2 days to 2 weeks after the induction of arthritis, the SP and CGRP fibers in the periosteum showed gradual depletion. In the thickened subsynovial tissues that were revascularized, no ingrowth of neural elements was found. As the total number of nerve fibers in the synovial tissue did not change, large parts of the synovia directly facing the joint cavity were not innervated at 1 week after the induction of arthritis. These results strongly suggest that periosteal SP and CGRP fibers were depleted during arthritis. Synovial proliferation without concomitant fiber growth is the main cause of the reduced number of immunocytochemically detectable fibers in the mouse arthritic knee joint.
Anat Rec 2000 09 01
PMID:Neurovascular plasticity in the knee joint of an arthritic mouse model. 1096 36

The periosteum contains osteoprogenitors that differentiate to osteoblasts in bone growth or repair. Our previous studies suggested the hypothesis that the physical contact of the periosteum with the bone matrix is requisite for the differentiation of osteoblasts. To test the hypothesis, the present study was designed to investigate how the contact between the periosteum and the bone matrix influences the osteoblastic differentiation of periosteal cells with establishing a new experimental model in vivo. Differentiation of osteoblasts was assessed by gene expression of type I collagen, osteocalcin and bone sialoprotein using in situ hybridization. A barrier was designed to prevent periosteal cells from contacting the bone matrix using the membrane filter. The membrane filter was inserted surgically between the surface of rat parietal bone and the periosteum after being punched out with pin holes. Periosteal cells were allowed to contact with the bone surface only through the pin holes. The pin hole was filled with cells derived from the periosteum 1 week after inserting the filter. Differentiation of osteoblasts in week 2 and noticeable bone formation in week 3 were identified on the bone surface only under the pin hole but not under the filter. The present study demonstrated that the physical contact with the bone matrix promotes osteoblastic differentiation of periosteum-derived cells in vivo.
Anat Rec 2001 09 01
PMID:Osteoblastic differentiation of periosteum-derived cells is promoted by the physical contact with the bone matrix in vivo. 1150 73

Grafted periosteum is known to have potential for heterotopic bone formation by endochondral ossification. Although osteochondrogenic cells have been thought to originate from the osteogenic layer in grafted periosteum, no histological report has yet demonstrated this. The present study was designed to elucidate the origin of chondrogenesis preceding bone formation in grafted periosteum. Periostea harvested from young Japanese white rabbits' tibiae were grafted into suprahyoid muscles and examined radiographically and histologically at postoperative days 1, 7, 9, 14, 21, and 35. Normal periostea and tibial graft site were also examined. Surgical harvesting of the periosteum split and damaged its osteogenic layer but retained the fibrous layer intact. Most of the osteoblasts remained on the tibial bone surface, and only few cells of the osteogenic layer were present in grafted tissue. By the seventh day after grafting, the fibrous layer had thickened. The fibroblastic cells in the fibrous layer had significantly increased in number (P < 0.01) and were positively stained for proliferating cell nuclear antigen. These cells exhibited alkaline phosphatase activity at day 9. The differentiated chondrocytes had formed cartilage at postoperative day 14. Cells in the osteogenic layer appeared necrotic and subsequently disappeared. Following postoperative day 21, cartilage was replaced by trabecular bone. Bone formation was completed by 35 days. An X-ray analysis at this time also revealed new bone formation. These findings indicate that grafted periosteum forms bone by endochondral ossification and that the cells of the fibrous layer play essential roles in chondrogenesis that precedes such bone formation.
Anat Rec 2001 12 01
PMID:Cellular origin of endochondral ossification from grafted periosteum. 1174 90


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