Resorption lacunae (RL) are discussed as stressors that can increase the risk of mechanical failure in a trabecular network. Quantification of RL has previously been described through the parameter eroded surface/bone surface (ES/BS) as established by light microscopy (LM) analysis, but the results have been inconsistent and contradictory. Using scanning electron microscopy (SEM), a new study design for quantitative evaluation is introduced. To test its applicability a pilot study was executed with trabecular bone dissected from a femoral head of 28 autopsy subjects (14 female and 14 male). A 2.4 x 2.8 x 1.0 mm sample was excised 1.5 cm below the joint surface of each specimen in coronal medial slices of the femoral head and examined. A virtual grid with 1050 squares superimposed over the generated SEM image allowed determination of the ratio of squares containing RL to squares with an unaffected trabecular surface (RL/U). Classical ES/BS was assessed in parallel sections of the samples. The SEM, and to a lesser extent the qualitative different LM analysis, indicated a gender independent predominance of RL in subjects older than 50 years. This pilot study suggests that the new study design could be useful for acquiring quantitative RL data.

Giant cell tumor (GCT) offers a unique model for the hematopoietic–stromal cell interaction in human bone marrow. Evidence has been presented that GCT stromal cells (GCTSCs) promote accumulation, size and activity of the giant cells. Although GCTSCs are considered the neoplastic component of GCT, little is known about their genetic basis and, to date, a tumor-specific gene expression pattern has not been characterized. Mesenchymal stem cells (MSCs) have been identified as the origin of the GCT neoplastic stromal cell. Using state of the art array technology, expression profiling was applied to enriched stromal cell populations from five different GCTs and two primary MSCs as controls. Of the 29 differentially expressed genes found, 25 showed an increased expression. Differential mRNA expression was verified by real-time polymerase chain reaction analysis of 10 selected genes, supporting the validity of cDNA arrays as a tool to identify tumor-related genes in GCTSCs. Increased expression of two oncogenes, JUN and NME2, was substantiated at the protein level, utilizing immunohistochemical evaluation of GCT sections and Western-blot analysis. Increased phosphorylation of JUN Ser-63 was also found.

In the present study a novel systematic distribution scheme of resorption lacunae (RL) was applied using scanning electron microscopy. RL, classified as either reticulate patch resorption lacunae (RPR) or as longitudinally extended resorption lacunae (LER) [11, were analyzed and quantified according to their localizations on rods (middle, nodes or both) and plates (central or peripheral) in standardized segments from the femoral head of 24 Caucasian subjects without bone disease. Age and gender variations were explored. No clear gender-related distribution pattern could be detected on plates. On rods of males, however, the distribution of RL tended to be higher at the nodes, but seemed to be more prevalent in the middle or extended from the middle to the nodes of rods in females. Certain other non-conclusive tendencies in relation to age, gender, type of RL and localization were observed.

Growth factors, hormones, and matrix proteins regulate osteoblast proliferation and differentiation, acting through cognate receptors. Since each of the receptors are coupled to a variety of distinct signal transduction pathways, in this report we evaluated whether there is a common convergent intermediate step that allows cross-talk among the various pathways. Since extracellular signal-regulated kinases 1 and 2 (Erk1/2) play a role in mitogenesis and differentiation processes, we evaluated the effects of various osteotrophic factors on Erk1/2 phosphorylation in osteoblasts. Osteoblasts isolated from the metaphyseal marrow (MM) and diaphyseal marrow (DM) of 4-6 week old male rat longitudinal bones were grown to confluency and Erk1/2-phosphorylation was evaluated using antibodies that recognized either the total or the phosphorylated form of the kinase. There was very little Erk1/2 phosphorylation in cells kept in suspension. Both MM and DM cells attached to fibronectin (FN), demonstrated Erk1/2 phosphorylation that persisted for at least up to 8h. Platelet-derived growth factor AB (PDGF-AB) induced a transient and robust Erk1/2 phosphorylation that was attenuated by 2h. Studies with specific inhibitors indicated that the effects of these factors were mediated by protein kinase C, by receptor tyrosine kinase, as well as by protein phosphatases. Parathyroid hormone (PTH 1-34), a bone anabolic agent however, caused a down-regulation of FN stimulated Erk1/2 phosphorylation in MM derived cells. The inhibitory effect of PTH was mediated through cAMP-dependent protein kinase A (PKA) activation. The data collectively suggest that a combination of diverse extracellular stimuli regulates Erk1/2 phosphorylation that may ultimately influence osteoblast proliferation and/or differentiation.

Resorption lacunae and perforation types mirror resorptional activity of osteoclasts and are important for the integrity of bone architecture. In the present study, distinctive microstructural features of cancellous bone dissected from femoral heads of 28 autopsy subjects (14 females and 14 males) were defined and evaluated by light microscopic (LM) histology and scanning electron microscopy (SEM). The work differentiates two types of resorption lacunae in trabecular bone: the longitudinally extended resorption lacunae (LER) and the reticulate patch resorption lacunae (RPR). Further, two types of perforations are distinguished: the lacunar perforation (LP) and the tunneling perforation (TP), which are differentiated from potential blood vessel canals (BC). Evidence is presented that the spatial distribution on rods or plates is highly correlated with the resorption type. The RPR type was more frequently seen and was primarily localized at the nodes of rods, in the middle regions of rods, and in the center region of plates as compared to the LER type. The presented evaluation scheme of resorption and perforation types could prove useful in future studies for systematically investigating potential microstructural changes associated with disturbed bone turnover.

Fibroblastlike stromal cells, which are always present as a component of giant cell tumor of bone (GCT), can be observed in both in vivo and cultured cell samples. Although they are assumed to trigger the cancer process in GCT, the histogenesis of GCT stromal cells is poorly understood. It is known that mesenchymal stem cells (MSCs) can develop to osteoblasts. Evidence has been presented that GCT stromal cells can also develop to osteoblasts. A connection between MSCs and GCT stromal cells was sought by using 2 different laboratory approaches. First, immunohistological analyses revealed that some of the same markers, detected by the SH2, SH3, and SH4 antibodies and the CD166 antigen, were found in GCT stromal cells as in the first developmental stages of osteoblast differentiation from the initial MSCs. These immunohistological findings could be confirmed by reverse transcriptase polymerase chain reaction. Second, cellular differentiation by morphology and lineage-specific staining offered evidence that not only osteoblasts, but also chondroblasts and adipocytes, could be cultured from stromal cells. The presented double approach indicates that GCT stromal cells can originate from MSCs.

AIMS:Expression analysis of the protein tyrosine kinases, focal adhesion kinase (FAK) and proline-rich tyrosine kinase2 (Pyk2) in high grade osteosarcomas.MATERIALS AND METHODS:Expression of the kinases was evaluated qualitatively by immunohistochemical staining and quantitatively by real-time PCR.RESULTS:Osteoblastic cells of high grade osteosarcomas show a distinct FAK expression but an overexpression at the transcriptional level could not be detected. The Pyk2-mRNA expression was decreased in osteosarcomas.CONCLUSION:An altered relationship of FAK and Pyk2 was observed for different tumors and could also be important for osteosarcoma development.

FACTS:Aseptic loosening of hip arthroplasties are the main reason for revision operations. Basic research indicates a significant relevance of the interface membrane formed between the implant an the surrounding bone. Their cellular composition and the influence of various factors on the process of aseptic loosening has attracted scientific interest. Cytokines are essential for intracellular communication. QUESTION:Is it possible to reveal differences in the expression profile of cytokines between well-fixed and failed hip arthroplasties using the cDNA array approach? AIM. Generation of a cytokine expression profile characteristic for failed hip arthroplasty. METHODS AND RESULTS:Radioactively labeled cDNA probes were synthesised from mRNA isolated from the interface membrane of six patients with aseptic loosened hip arthroplasty. Using a phosphorimager the analysis of the cDNA arrays revealed nine cytokines which were overexpressed compared with the reference tissue (Calgranulin A, Calgranulin B, IL-10, MCP-1, RANTES, TFDG1, TNFR2, RAI, THYB10). CONCLUSION:In this study four out of these nine cytokines were found to be connected with the process of aseptic loosening for the first time.

Stand des Wissens. Die aseptische Lockerung von Endoprothesen ist die Hauptursache für den Wechsel von Endoprothesen. Die Grundlagenforschung brachte Hinweise auf die Bedeutung der zwischen Implantat und angrenzendem Knochengewebe ausgebildeten Interfacemembran. Ihre zelluläre Zusammensetzung und der Einfluss verschiedenartigster Faktoren auf den Lockerungsprozess rückten ins wissenschaftliche Interesse. Zytokine sind für die intrazelluläre Kommunikation unerlässlich.

OBJECTIVE To examine the durability of the Stentor and Vanguard endovascular devices in human implants. METHODS The textile covering, the polypropylene ligatures and the stent metal of 34 devices (25 Stentor, 9 Vanguard) with a mean duration of implantation of 28.8 +/- 16 months was examined by means of stereomicroscopy and scanning electron microscopy. RESULTS The polyester textile covering showed gaps along the sutured seam and isolated holes in the fabric. All of the examined polypropylene ligatures were worn, some ruptured. Four different types of stent corrosion were classified--pits (100%), bizarre craters (68%), large deficiencies (14%) and fractures (32%). CONCLUSION Holes in the polyester fabric and frame dislocations are specific for the design of Stentor and Vanguard grafts. The early corrosion of the stent metal Nitinol in these devices is surprising. Until more experience is gained with other devices, we have to be reminded, that the "gold standard" for the long-term durability of artificial vascular grafts is still "today's" conventional graft.

Neue Untersuchungen des Riesenzelltumors beschreiben die Sekretion zahlreicher Zytokine und Wachstumsfaktoren, unter anderem MCP-1, ODF und M-CSF, von den Stromazellen. Diese Faktoren sind an der Chemotaxis von Monozyten und der Differenzierung von Osteoklasten beteiligt. Somit scheinen die Stromazellen die Migration von Monozyten aus dem Blut in das Tumorgewebe und die dortige Fusion in osteoklastenähnliche, mehrkernige Riesenzellen zu induzieren. Die mehrkernigen Riesenzellen entsprechen in ihrer Eigenschaft als knochenresorbierende Zellen den normalen Osteoklasten und sind für die Osteolyse des Riesenzelltumors verantwortlich. Dieses neue Modell für die Entstehung des Riesenzelltumors unterstützt die Hypothese, dass es sich bei den Stromazellen um die neoplastische Komponente des Riesenzelltumors handelt, wohingegen die Monozyten und die mehrkernigen Riesenzellen nur als reaktive Komponenten im Tumorgewebe vorliegen. In Bezug auf diese Daten sollte die Nomenklatur des sog. "Riesenzelltumors" überdacht werden.

Stand der Forschung. Lichtmikroskopische Untersuchungen an histologischen- und Schliffpräparaten ließen strukturelle Unterschiede bei Resorptionslakunen und Perforationen erahnen.

Intermittent administration of parathyroid hormone (PTH) activates new sites of bone formation by stimulating osteoblast differentiation and function resulting in an increase in bone mass. Because integrins have been shown to play a crucial role in osteoblast differentiation and bone formation, in the present study, we evaluated whether human PTH (1-34) upon administration to rats, influenced integrin expression in osteoblastic cells isolated from the metaphysis and the diaphysis of rat long bones. Initial immunohistochemical evaluation of bone sections demonstrated that the osteoblasts expressed at least alpha (v), alpha (2), alpha (3), and alpha (5)beta (1) integrins. Immunocolocalization studies for integrins and vinculin established that alpha (v), alpha (2), and alpha (5)beta (1), but not alpha (3) integrins were present in the focal adhesion sites of osteoblasts attached to IFN coated surfaces. Osteoprogenitor cells isolated from metaphyseal (but not diaphyseal) marrow of rats injected with intermittent PTH (1-34) exhibited greater alpha (v) and reduced alpha (2) levels, with no apparent changes in alpha (3), and alpha (5)beta (1) integrin levels, as assessed by immunohistochemistry, Northern, and Western blot analyses. However, these changes were not observed on the same cells treated with PTH in vitro. These observations suggest that integrin modulation by PTH is likely to be indirect and that selective phenotypic expression of integrin subtypes is part of te cascade of events that lead to PTH (1-34) mediated osteoblast differentiation. (C) 2001 Wiley-Liss, Inc.

Giant cell tumor of bone (GCT) is a locally osteolytic tumor with variable aggressiveness. In rare cases, pulmonary metastasis can be observed. The lesion most frequently occurs in the epiphysis of long tubular bones of the knee region, predominantly affecting young adults after closure of the growth plate. The characteristic histological appearance of GCT displays a high number of osteoclast-like multinucleated giant cells, which resulted in the classification "osteoclastoma" or "giant cell tumor". Apart from the multinucleated giant cells, there are two mononuclear cell types in GCT. The first one has a round morphology and resembles monocytes. The second cell type is the spindle-shaped, fibroblast-like stromal cell. Cell culture experiments with GCT cells revealed the stromal cell to be the proliferating component of the GCT. The other two cell types, the monocyte and the multinucleated giant cell, were lost after a few cell culture passages. Furthermore, latest results from GCT reveal that the stromal cells secrete a variety of cytokines and differentiation factors, including MCP1, ODF, and M-CSF. These molecules are monocyte chemoattractants and are essential for osteoclast differentiation, suggesting that the stromal cell stimulates blood monocyte immigration into tumor tissue and enhances their fusion into osteoclast-like, multinucleated giant cells. The multinucleated giant cell itself resembles a normal osteoclast that is able to resorb bone leading to extended osteolysis. This new model of GCT genesis supports the hypothesis that the stromal cell is the neoplastic component whilst the monocytes and the multinucleated giant cells are just reactive components of this tumor. Taking this into consideration, the nomenclature of the "giant cell tumor" needs to be reconsidered.

A series of nine cases with monostotic fibrous dysplasia (FD) and five cases of fibrous dysplasia-like low-grade central osteosarcoma (fd-like lgcOSA) were applied in a mutational analysis. Restriction digestion analysis, single-stranded conformational polymorphism (SSCP) analysis, and repeated sequencing demonstrated a R201H mutation in six cases and a R201C mutation in three cases of patients with monostotic FD. These results demonstrate that the presence of Gsα gene mutations is a constant finding in monostotic FD. To our knowledge, this is the first report in the literature investigating Gsα gene mutations in lgcOSA, which is one of the most important differential diagnoses of FD because of its low-grade malignant behavior. In four of five cases of fd-like lgcOSA, no mutation has been detected. In one case of this tumor, a R201C mutation could be demonstrated. Because our results demonstrate a low prevalence of Gsα gene mutations in this tumor in contrast to monostotic FD, mutational analysis may be an additional helpful parameter in individual cases for the differential diagnosis of FD and fd-like lgcOSA.

Chloride channels play important roles in the plasma membrane and in intracellular organelles. Mice deficient for the ubiquitously expressed ClC-7 Cl(-) channel show severe osteopetrosis and retinal degeneration. Although osteoclasts are present in normal numbers, they fail to resorb bone because they cannot acidify the extracellular resorption lacuna. ClC-7 resides in late endosomal and lysosomal compartments. In osteoclasts, it is highly expressed in the ruffled membrane, formed by the fusion of H(+)-ATPase-containing vesicles, that secretes protons into the lacuna. We also identified CLCN7 mutations in a patient with human infantile malignant osteopetrosis. We conclude that ClC-7 provides the chloride conductance required for an efficient proton pumping by the H(+)-ATPase of the osteoclast ruffled membrane.

Purpose: To analyze surface alterations and fractures observed in the nitinol stent wires of explanted endovascular grafts used for treatment of abdominal aortic aneurysm. Methods: Twenty-one explanted Stentor devices and 1 Cragg stent were received from investigators in Germany and France. After macroscopy and photography, the explants were cleaned and the polyester coating removed. The frame was examined completely by stereomicroscopy, and irregularities were assayed by scanning electron microscopy and energy dispersive x-ray analysis (EDAX). The observed alterations were classified according to stereomicroscopic and electron microscopic morphology. Results: The mean implantation interval for the endografts was 29.1 ± 13.2 months (range 5–46). All examined explants, even those retrieved after only a few months in situ, showed pitlike surface damage 10–25 µm in diameter. Larger, irregularly shaped surface alterations were observed in ∼70% of the explants. Older explants (age >32 months) presented vast regions of decay, with bending of the wire and stress cracks in some areas. EDAX examination revealed decreased nickel concentration in the corroded regions. Conclusions: Corrosion of the nitinol wire in endovascular grafts is confirmed. Presumably, the observed pitting and irregularly shaped corrosion defects are the precursors of material failure. They weaken the thin wire, which leads to stress cracks and eventually fracture of the stent wire under circulatory pulsation. Cell-induced electrochemical corrosion and active cellular destruction of surfaces are well-known mechanisms that must be investigated for their possible roles in the corrosion of stent metals.