The Architecture of the Adhesive Apparatus of Cultured Osteoclasts: From Podosome Formation to Sealing Zone Assembly

BACKGROUND: Osteoclasts are bone-degrading cells, which play a central role in physiological bone remodeling. Unbalanced osteoclast activity is largely responsible for pathological conditions such as osteoporosis. Osteoclasts develop specialized adhesion structures, the so-called podosomes, which subsequently undergo dramatic reorganization into sealing zones. These ring-like adhesion structures, which delimit the resorption site, effectively seal the cell to the substrate forming a diffusion barrier. The structural integrity of the sealing zone is essential for the cell ability to degrade bone, yet its structural organization is poorly understood. PRINCIPAL FINDINGS: Combining high-resolution scanning electron microscopy with fluorescence microscopy performed on the same sample, we mapped the molecular architecture of the osteoclast resorptive apparatus from individual podosomes to the sealing zone, at an unprecedented resolution. Podosomes are composed of an actin-bundle core, flanked by a ring containing adhesion proteins connected to the core via dome-like radial actin fibers. The sealing zone, hallmark of bone-resorbing osteoclasts, consists of a dense array of podosomes communicating through a network of actin filaments, parallel to the substrate and anchored to the adhesive plaque domain via radial actin fibers. SIGNIFICANCE: The sealing zone of osteoclasts cultured on bone is made of structural units clearly related to individual podosomes. It differs from individual or clustered podosomes in the higher density and degree of inter-connectivity of its building blocks, thus forming a unique continuous functional structure connecting the cell to its extracellular milieu. Through this continuous structure, signals reporting on the substrate condition may be transmitted to the whole cell, modulating the cell response under physiological and pathological conditions

Prospective evaluation of calcium and estrogen administration on bone mass and metabolism after ovariectomy.

We evaluated the effects of low-dose ethinylestradiol administration in the prevention of the rapid bone loss that follows ovariectomy in women. After 10-30 days from surgery, patients received either a sole calcium supplementation 500 mg/day (n = 20) or ethinylestradiol 20 micrograms/day in addition to the same daily calcium supplement (n = 21), for 12 months. In the control group, urinary hydroxyproline excretion, serum alkaline phosphatase and plasma bone Gla protein levels presented a substantial (p < 0.05) increase, while radial bone density significantly (p < 0.05) decreased 6 months after surgery. In the ethinylestradiol-treated group, the patterns of biochemical markers indicated that ethinylestradiol can restrain the bone remodelling processes. Radial bone density showed no significant modification during the 12 months' study period. In conclusions, these results demonstrate that the administration of 20 micrograms/day of ethinylestradiol can prevent the rapid bone loss that follows ovariectom

Brain recurrences in patients with ovarian cancer: report of 12 cases and review of the literature

The aim of the investigation was to assess 12 cases of brain recurrences among ovarian cancer patients who had undergone surgery followed by platinum-based chemotherapy. Brain lesions were the first recurrence in 4 (33%) patients, the second recurrence in 7 (58%), and the fourth recurrence in one patient. The median time from ovarian cancer diagnosis to brain metastasis detection was 33.5 months (range, 13.5-86.5 months), brain metastases were multiple in 6 (50%) cases, and extra-cranial disease was present in 7 (58%) cases. Brain recurrence was symptomatic in 10 patients and the clinical presentation included impaired deambulation, extremity weakness, seizure, headache, nausea/vomiting and visual disturbance. Out of the 6 patients with single brain metastases, one underwent surgery, one had surgical excision followed by whole brain irradiation, 3 patients received stereotactic radiotherapy (followed by chemotherapy for coexistent extra-abdominal recurrence in one), and one had only symptomatic treatment. Out of the 6 patients with multiple brain metastases, four received whole brain irradiation (followed by chemotherapy for concomitant extra-cranial recurrence in one case), one patient had gamma-knife irradiation of three cerebral lesions (followed by chemotherapy for concurrent abdominal recurrence), and one patient had only symptomatic treatment. The median overall survival from diagnosis of brain metastasis was 8.3 months (range, 1-28 months), and it was not related to the number of brain metastases (multiple versus single), presence or absence of extra-cranial disease, or interval between ovarian cancer diagnosis and brain metastasis detection ( or =33.5 months). In conclusion, brain metastasis from ovarian cancer can represent a late manifestation of the disease, associated with a very poor prognosis

Yeast killer toxin-like candidacidal Ab6 antibodies elicited through the manipulation of the idiotypic cascade

A mouse anti-anti-anti-idiotypic (Id) IgM monoclonal antibody (mAb K20, Ab4), functionally mimicking a Wyckerhamomyces anomalus (Pichia anomala) killer toxin (KT) characterized by fungicidal activity against yeasts presenting specific cell wall receptors (KTR) mainly constituted by beta-1,3-glucan, was produced from animals presenting anti-KT Abs (Ab3) following immunization with a rat IgM anti-Id KT-like mAb (mAb K10, Ab2). MAb K10 was produced by immunization with a KTneutralizing mAb (mAb KT4, Ab1) bearing the internal image of KTR. MAb K20, likewise mAb K10, proved to be fungicidal in vitro against KT-sensitive Candida albicans cells, an activity neutralized by mAb KT4, and was capable of binding to beta-1,3- glucan. MAb K20 and mAb K10 competed with each other and with KT for binding to C. albicans KTR. MAb K20 was used to identify peptide mimics of KTR by the selection of phage clones from random peptide phage display libraries. Using this strategy, four peptides (TK 1-4) were selected and used as immunogen in mice in the form of either keyhole limpet hemocyanin (KLH) conjugates or peptide-encoding minigenes. Peptide and DNA immunization could induce serum Abs characterized by candidacidal activity, which was inhibited by laminarin, a soluble beta-1,3-glucan, but not by pustulan, a beta-1,6- glucan. These findings show that the idiotypic cascade can not only overcome the barrier of animal species but also the nature of immunogens and the type of technology adopted

Post-yield and failure properties of cortical bone

Ageing and associated skeletal diseases pose a significant challenge for health care systems worldwide. Age-related fractures have a serious impact on personal, social and economic wellbeing. A significant proportion of physiological loading is carried by the cortical shell. Its role in the fracture resistance and strength of whole bones in the ageing skeleton is of utmost importance. Even though a large body of knowledge has been accumulated on this topic on the macroscale, the underlying micromechanical material behaviour and the scale transition of bone's mechanical properties are yet to be uncovered. Therefore, this review aims at providing an overview of the state-of-the-art of the post-yield and failure properties of cortical bone at the extracellular matrix and the tissue level