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 58,342 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recent data suggests that induction of prostaglandin endoperoxide H synthase-2 (PGHS-2) is critical for the anabolic response of lamellar bone elicited by mechanical strain in vivo. The aim of the present study was to localise PGHS-1 and PGHS-2 in rat tibiae following four-point bending in vivo. Right tibiae of 19 adult female rats were subjected to 300 cycles of bending or sham loading at 2.0 Hz with an applied load of 65 N. At 0, 6, and 24 hr postloading, rats were anaesthetised and perfused with Bouin's fixative. Left and right tibiae were dissected, postfixed for 4 hr at 4 degrees C, decalcified in EDTA, and embedded in paraffin. Serial 5 pM sections were stained for PGHS-1 and PGHS-2 using standard immunoperoxidase procedures. For the first time, immunoreactivity for both PGHS-1 and PGHS-2 was localised in bone cells in situ, in the rat tibia. PGHS-1 was distributed widely in all tibiae, while PGHS-2 showed sparse localisation. At the endocortical surfaces (EcS), osteoblasts, lining cells, and osteocytes close to the surface reacted strongly for PGHS-1, as did intracortical osteocytes. At the periosteal surface (PsS), osteoblasts and cells of the osteogenic region were immunopositive. Immediately after loading, the numerical density (n.mm(-2)) of osteocytes labeled with PGHS-1 was significantly greater in loaded tibiae compared to controls. This increase was not seen after sham loading. At 6 and 24 hr postloading, this difference was no longer evident. Staining for PGHS-2 was sparse compared to PGHS-1. Light to moderate reactivity was observed in osteocytes and canaliculae, but the numerical density of labeled cells was significantly less than that for PGHS-1. Moderate staining was seen in lining cells and osteoblasts at the EcS and PsS of some tibiae. Osteoclasts at the PsS reacted strongly for both PGHS-1 and PGHS-2. There was a similar load-related increase in the density of PGHS-2-labeled osteocytes 0 hr postloading. The labeled osteocyte density had decreased at 6 hr, but remained significantly greater in loaded bones. These results show that both forms of PGHS can be localised in bone cells, with PGHS-1 expressed to a greater extent than PGHS-2. The data also suggest that both PGHS-1 and PGHS-2 may play important roles in the early response of bone to mechanical loading in vivo.
Anat Rec 1998 12
PMID:Localisation of prostaglandin endoperoxide H synthase (PGHS)-1 and PGHS-2 in bone following mechanical loading in vivo. 984 8

Capillary invasion is a vital regulatory signal during bone morphogenesis that is influenced by angiogenic molecules such as fibroblast growth factor (FGF) and some members of the transforming growth factor-beta (TGF-beta) superfamily, including TGF-betas themselves. Bone morphogenetic proteins (BMPs), which are members of the TGF-beta superfamily, have previously not been shown to possess direct angiogenic properties. Osteogenic protein-1 (OP-1; BMP-7) is a potent regulator of cartilage and bone differentiation in vivo. The osteogenic and angiogenic properties of OP-1 at both ortho- and heterotopic sites in adult chacma baboons (Papio ursinus) are enhanced synergistically by the simultaneous application of relatively low doses of TGF-beta1. The single application of relatively high doses of TGF-beta1 (20 ng), and bFGF (500 ng) or relatively low (100 ng) and high (1,000 ng) doses of OP-1 in the chick chorioallantoic membrane (CAM) assay elicited a prominent and (for OP-1) dose-dependent angiogenic response. The binary application of a relatively low dose of OP-1 (100 ng) with a relatively low dose of bFGF (100 ng) or with a relatively low (5 ng) or high (20 ng) dose of TGF-beta1 resulted in a synergistic enhancement of the angiogenic response. The angiogenic effect of the relatively low doses of the combined morphogens was distinctly more pronounced than that of the single application of the relatively high doses of the respective factors. The present findings suggest that these morphogens may be deployed in binary combination in order to accentuate experimental angiogenesis. The cooperative interaction of the different morphogens in the CAM assay may provide important biological clues towards the control of clinical angiogenesis.
Anat Rec 2000 05 01
PMID:Osteogenic protein-1, a bone morphogenetic protein, induces angiogenesis in the chick chorioallantoic membrane and synergizes with basic fibroblast growth factor and transforming growth factor-beta1. 1076 Jul 48

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

Regeneration of damaged periodontal tissues is mediated by periodontal cells, but a major sub-population comprises highly differentiated cells that do not renew. To overcome the loss of specialized cell types caused by disease, various therapeutic approaches including cell transplants have been developed to promote cell re-population in periodontal tissues. As previous transplantation studies used unlabeled cells, that are indistinguishable from host cells, it has been difficult to assess the contributions of transplanted cells to the healing processes. To track the fate and differentiation of rat periodontal cells transplanted into periodontal wounds, we used collagen-coated fluorescent beads as a permanent endocytosed marker, or cells constitutively expressing beta-galactosidase. We assessed osteogenic cell differentiation with immunohistochemical staining for osteopontin and bone sialoprotein. Cells were transplanted into periodontal wounds created in Sprague--Dawley male rats that are null for beta-galactosidase. Defects were allowed to heal spontaneously (controls), or were closed with collagen implants mixed with beta-galactosidase-positive (Lac-Z) periodontal cells, or closed with collagen implants mixed with periodontal cells loaded with fluorescent beads. Animals were killed at 1 and 2 weeks after surgery and tissues were prepared for morphometric assessment and immunostaining for osteopontin (OPN) and bone sialoprotein (BSP). Transplanted cells were easily distinguished by fluorescent beads or by beta-galactosidase-positive expression and were distributed throughout the regenerating periodontal ligament (PL) and alveolar bone. At 1 week after wounding, animals treated with beta-galactosidase-positive cells exhibited a slightly higher percentage of labeled cells in the PL compared with the fluorescent bead-labeled cell implant group (2% vs. 1% respectively; P > 0.2). At Week 2 percentages of labeled cells were slightly increased in the regenerating PL (approximately 3% for both groups, P > 0.2). In regenerating alveolar bone at 1 week, animals that were treated with beta-galactosidase-positive cells and fluorescent bead-loaded cells exhibited approximately 30% and 25% of labeled cells respectively. At 2 weeks after wounding there was an increase in the percentage of transplanted beta-galactosidase-positive cells (approximately 39% at week 2; P < 0.05), but not of transplanted cells with fluorescent beads (approximately 25% at week 2). In sites with transplanted cells there were higher percentages of OPN positive and BSP positive cells in nascent bone and more newly formed bone than in controls (>40%; P < 0.05). Transplantation of beta-galactosidase-positive cells or cells loaded with fluorescent beads is a useful method for assessing the fate and differentiation of periodontal cells in vivo. Fluorescent beads, however, are diluted at mitosis and this method underestimates the percentage of transplanted cells. As transplanted periodontal cells in both groups promoted regeneration of alveolar bone, cell transplantation could improve the restoration of periodontium destroyed by periodontitis.
Anat Rec 2001 02 01
PMID:Transplantation of labeled periodontal ligament cells promotes regeneration of alveolar bone. 1116 14

This study details the profile of 13 cell surface cluster differentiation markers on human reserve stem cells derived from connective tissues. Stem cells were isolated from the connective tissues of dermis and skeletal muscle derived from fetal, mature, and geriatric humans. An insulin/dexamethasone phenotypic bioassay was used to determine the identity of the stem cells from each population. All populations contained lineage-committed myogenic, adipogenic, chondrogenic, and osteogenic progenitor stem cells as well as lineage-uncommitted pluripotent stem cells capable of forming muscle, adipocytes, cartilage, bone, fibroblasts, and endothelial cells. Flow cytometric analysis of adult stem cell populations revealed positive staining for CD34 and CD90 and negative staining for CD3, CD4, CD8, CD11c, CD33, CD36, CD38, CD45, CD117, Glycophorin-A, and HLA DR-II.
Anat Rec 2001 09 01
PMID:Human reserve pluripotent mesenchymal stem cells are present in the connective tissues of skeletal muscle and dermis derived from fetal, adult, and geriatric donors. 1150 71

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

The purpose of the present study was to examine the process of bone formation in the regenerating cranial appendages of roe deer (Capreolus capreolus) and fallow deer (Dama dama) during the early postcasting period. After the antlers are cast, osteoclastic and osteoblastic activities lead to a smoothing of the pedicle's separation surface, a strengthening of the pedicle bone, and a partial restoration of the distal pedicle portion that was lost along with the cast antler. Initially, bone formation occurs by intramembranous ossification, but early during the regeneration process cartilage is formed at the tips of the cranial appendages, and is subsequently replaced by bone in a process of endochodral ossification. Shortly after the antlers are cast, the cambium layer of the periosteum in the distal pedicle is markedly enlarged, which suggests that the periosteum serves as a cell source for the bone-forming tissue covering the exposed pedicle bone. The histological findings of our study are consistent with the view that the bony component of the regenerating cranial appendages of deer is largely derived from the pedicle periosteum. Based on findings in other bone systems, we speculate that stem cells that can undergo both osteogenic and chondrogenic differentiation are present in the pedicle periosteum. The early onset of chondrogenesis in the regeneration process is regarded as an adaptation to the necessity of producing a huge volume of bone within a short period. This parallels the situation in other cases of chondrogenesis in membrane bones.
Anat Rec A Discov Mol Cell Evol Biol 2003 Aug
PMID:Histological studies of bone formation during pedicle restoration and early antler regeneration in roe deer and fallow deer. 1284 10

Bone regenerates following amputation through the level of the nail, but bone is capped following amputation through more proximal levels. Because osteogenesis requires an ample blood supply, we postulated that a restricted vascular supply might be correlated with restricted regenerative ability at proximal levels. More than 40 rats and mice were injected with ink or resin to visualize vascular supplies of intact, regenerating, and nonregenerating rat and mouse digits. Ink-injected specimens were viewed as histological sections or cleared whole mounts. Partially digested resin casts were viewed using scanning electron microscopy. Contrary to our hypothesis, prior to amputation, proximal sites are more vascular than distal sites. At both proximal and distal levels, endosteal and periosteal vascular systems are evident. However, in proximal phalanges, additional subcutaneous and dermal layers encircle the bone. Beneath the distal nail, these layers are absent, and a single layer of vessels provides both periosteal and cutaneous supplies. After amputation at both levels, new vessels sprout profusely in osteogenic areas of both endosteum and periosteum. However, at proximal levels, the additional hypodermal and dermal vessels contribute to a vascular plexus that, paradoxically, may impair bone regrowth by contributing to the formation of dermal scar rather than bone.
Anat Rec A Discov Mol Cell Evol Biol 2004 May
PMID:Vascular supplies differ in regenerating and nonregenerating amputated rodent digits. 1510 39

The present ultrastructural investigation into osteocyte dendrogenesis represents a continuation of a previous study (Ferretti et al., Anat. Embryol., 2002; 206:21-29), in which we pointed out that, during intramembranous ossification, the well-known dynamic bone formation (DBF), performed by migrating osteoblast laminae, is preceded by static bone formation (SBF), in which cords of stationary osteoblasts transform into osteocytes in the same site where they differentiated. The research was carried out on the perichondral center of ossification surrounding the mid shaft level of various long bones of chick embryos and newborn rabbits. Transmission electron microscope observations showed that the formation of osteocyte dendrites is quite different in the two types of osteogenesis, mainly depending on whether or not osteoblast movement occurs. In DBF, osteoblasts transform into small ovoidal/ellipsoidal osteocytes and their dendrites form in an asynchronous and asymmetrical manner in concomitance with, and depending on, the advancing mineralizing surface and the receding osteogenic laminae. In SBF, stationary osteoblasts give rise to big globous osteocytes, located inside confluent lacunae, with short and symmetrical dendrites that can radiate simultaneously all around their cell body because they are completely surrounded by unmineralized matrix. Contacts and gap junctions were observed between all osteocytes (both SBF- and DBF-derived) and between osteocytes and osteoblasts. Finally, a continuous osteocyte network extends throughout the bone, regardless of its static or dynamic origin. This network has the characteristic of a functional syncytium, potentially capable of modulating, by wiring transmission, the cells of the osteogenic lineage covering the bone surfaces.
Anat Rec A Discov Mol Cell Evol Biol 2004 May
PMID:Osteocyte dendrogenesis in static and dynamic bone formation: an ultrastructural study. 1510 43

The knee menisci are wedge-shaped semilunar fibrocartilaginous structures that reside between the femur and tibia and function to transmit and distribute load. These structures have characteristics of both fibrous and cartilaginous tissues. The cartilage-like inner region and the fibrous vascularized outer region each has a distinct extracellular matrix, and resident meniscal fibrochondrocytes (MFCs) with distinct morphologies dependent on their location. Damage to the meniscus is common, and disruption of tissue structure and function result in erosion of the underlying articular cartilage. It has been observed that damage in the vascular periphery undergoes spontaneous repair, whereas damage of the inner region does not heal. While vascularity of the peripheral region plays a role in healing, recent findings have also suggested that local cellular composition influences local healing capacity. This study examined the variation in multipotential characteristics of cell populations isolated from different regions of the bovine meniscus. MFCs were isolated from the outer (vascular), inner (avascular), and horn (mixed) regions and induced toward chondrogenic, adipogenic, and osteogenic lineages. The results of this study suggest that MFCs from all regions of the meniscus possess a multilineage differentiation capability, particularly toward chondrogenesis and adipogenesis. MFCs from the outer region were most plastic, differentiating along all three mesenchymal lineages. These findings may underlie the experimental observation of improved integration of meniscus grafts from the outer zone and may have implications for developing strategies of cell-based meniscus repair.
Anat Rec (Hoboken) 2007 Jan
PMID:Regional multilineage differentiation potential of meniscal fibrochondrocytes: implications for meniscus repair. 1744 Nov 97


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