Biomedical subjects

Nicholas A Athanasou

Publications and source records attributed to Nicholas A Athanasou.

7 recordsLinked to original sources

PubMed2006

Hepatocyte growth factor can substitute for M-CSF to support osteoclastogenesis.

Osteopetrotic mice lacking functional macrophage-colony stimulating factor (M-CSF) recover with ageing, suggesting that alternative osteoclastogenesis pathways exist. Hepatocyte growth factor (HGF) and M-CSF signal through tyrosine kinase receptors and phosphorylate common transducers and effectors such as Src, Grb2, and PI3-Kinase. HGF is known to play a role in osteoclast formation, and in this study we have determined whether HGF could replace M-CSF to support human osteoclastogenesis. We found that the HGF receptor, c-Met, is expressed by the CD14(+) monocyte fraction of human peripheral blood mononuclear cells (PBMC). HGF was able to support monocyte-osteoclast differentiation in the presence of receptor activator for nuclear factor kappaB ligand as evidenced by the formation of numerous multinucleated tartrate-resistant acid phosphatase and vitronectin receptor positive cells which formed F-actin rings and were capable of lacunar resorption. The addition of a neutralising antibody to M-CSF did not inhibit osteoclast differentiation. HGF is a well-established survival factor and viability assays and live/dead staining showed that it promoted the survival and proliferation of monocytes and osteoclasts in a manner similar to M-CSF. Our findings indicate that HGF can substitute for M-CSF to support human osteoclast formation.

Adult↗

PubMed2006

Osteoclast differentiation and bone resorption in multicentric reticulohistiocytosis.

Multicentric reticulohistiocytosis (MR) is a systemic disease of unknown cause characterized by the presence of a heavy macrophage infiltrate in skin and synovial tissues and the development of an erosive polyarthritis. The synovial fluid in MR is known to contain numerous mononuclear cells. In this study, we have determined whether these cells contribute to joint destruction in MR by differentiating them into osteoclasts. Synovial fluid mononuclear cells were isolated from the knee joint of a 44-year-old male with MR. These cells were cultured with various combinations of macrophage-colony stimulating factor, receptor activator for nuclear factor kappaB ligand (RANKL), tumor necrosis factor alpha, interleukin-1alpha, osteoprotegerin, and zoledronate. Osteoclast differentiation was assessed by expression of tartrate-resistant acid phosphatase, vitronectin receptor, and the extent of lacunar resorption. Most MR synovial fluid mononuclear cells expressed a macrophage phenotype (CD14(+), CD68(+), HLA-DR(+), CD11b(+)). Extensive osteoclast formation and lacunar resorption were noted in macrophage-colony stimulating factor/RANKL-treated cell cultures. MR synovial fluid contained increased tumor necrosis factor alpha and decreased osteoprotegerin compared with osteoarthritis synovial fluid. Lacunar resorption was inhibited in cultures containing zoledronate. Pamidronate treatment of the patient also reduced the number of synovial fluid macrophages and resulted in less osteoclast formation and lacunar resorption. MR synovial fluid contains numerous macrophages that are capable of differentiating into osteoclasts by the RANKL signaling pathway. Inhibitors of osteoclast formation and resorption activity may be of use in preventing the severe joint destruction that commonly occurs in MR.

Adult↗

PubMed2006

Stimulation of osteoclast formation by inflammatory synovial fluid.

Peri-articular bone resorption is a feature of arthritis due to crystal deposition and rheumatoid disease. Under these conditions, the synovial fluid contains numerous inflammatory cells that produce cytokines and growth factors which promote osteoclast formation. The aim of this study was to determine whether inflammatory synovial fluid stimulates the formation of osteoclasts. Synovial fluid from rheumatoid arthritis (RA), pyrophosphate arthropathy (PPA) and osteoarthritis (OA) patients was added to cultures (n=8) of human peripheral blood mononuclear cells (PBMCs) in the presence and absence of macrophage colony-stimulating factor (M-CSF) and the receptor activator of NF-kappaB ligand (RANKL). Osteoclast formation was assessed by the formation of cells positive for tartrate-resistant acid phosphatase (TRAP) and vitronectin receptor (VNR) and the extent of lacunar resorption. The addition of 10% OA, RA and PPA synovial fluid to PBMC cultures resulted in the formation of numerous multinucleated or mononuclear TRAP(+) and VNR(+) cells which were capable of lacunar resorption. In contrast to PBMC cultures incubated with OA synovial fluid, there was marked stimulation of osteoclast formation and resorption in cultures containing inflammatory RA and PPA synovial fluid which contained high levels of tumour necrosis factor alpha, a factor which is known to stimulate RANKL-induced osteoclast formation.

Acid Phosphatase↗

PubMed2006

Staphylococcus aureus capsular material promotes osteoclast formation.

Osteomyelitis, which is most frequently due to infection by Staphylococcus aureus, commonly causes bone destruction. S. aureus is known to secrete a number of surface-associated proteins that are potent stimulators of bone resorption. The precise cellular and humoral mechanisms that mediate this stimulatory effect are uncertain. In this study, we have determined whether osteoclast formation and resorption is directly promoted by surface-associated proteins. Surface-associated material (SAM) obtained from a 24-hour culture of S. aureus was added to cultures of mouse and human monocytes. Human monocyte cultures were incubated in the presence and absence of a soluble receptor activator of nuclear factor kappa B ligand (RANKL) and macrophage colony stimulating factor (M-CSF). In cultures where M-CSF, RANKL, and SAM were added together, osteoclast formation did not exceed that seen in cultures with M-CSF and RANKL. In keeping with this finding, SAM did not increase osteoclast formation and resorption when mouse monocytes were cocultured with RANKL-expressing osteoblasts. In the absence of RANKL, however, SAM was capable of inducing osteoclast formation in cultures of human monocytes. This finding was evidenced by the generation of vitronectin receptor and tartrate-resistant acid phosphatasepositive multinucleated cells that were capable of lacunar resorption. Inhibitors of RANKL-dependent (RANK:Fc, OPG) and RANKL-independent (anti-TNF-alpha, gp130, IL-8, TGF-beta) osteoclast formation did not inhibit SAM-induced osteoclast formation. SAM did not stimulate mature osteoclast resorption activity. These findings indicate that RANKL, which is present in the circulation as a soluble factor, does not play a role in osteoclast formation in the presence of S. aureus SAM and that S. aureus SAM contains a soluble factor that promotes osteoclast formation by a RANKL-independent mechanism.

Animals↗

PubMed2004

Arthroplasty for ochronotic arthritis: no failure of 11 replacements in 3 patients followed 6-12 years.

BACKGROUND: Alkaptonuria is a rare single-gene disorder characterized by black pigmentation of cartilage and other connective tissues. Premature degenerative arthritis affects the large joints in many of these of patients. Medical treatment is limited to a protein-restricted diet (phenylalanine and tyrosine) with surgery reserved for end-stage joint disease. As in other metabolic bone diseases, there are concerns about the quality and strength of affected bones and therefore the suitability and longevity of replacement arthroplasty. The histopathology and outcome of joint replacement for alkaptonuric arthritis is unknown and limited to sporadic case reports. PATIENTS AND RESULTS: We describe 11 joint replacements in 3 patients with alkaptonuric polyarthropathy, including shoulder and elbow replacements not previously reported. No prosthetic failures occurred in up to 12 years of follow-up. INTERPRETATION: Total joint replacement is an acceptable treatment for degenerative joint disease in alkaptonuric patients, with implant survival comparable to that found in patients with osteoarthritis.

Aged↗

PubMed2004

Radial nerve palsy owing to localized hypertrophic neuropathy (intraneural perineurioma) in early childhood.

Localized hypertrophic neuropathy, also termed intraneural perineurioma, is a rare disorder of unknown etiology that produces a slowly progressive painless focal lesion of a peripheral nerve. It is characterized histologically by concentric whorls ("onion bulbs") of epithelial membrane antigen-reactive, S-100 protein-negative perineurial cells surrounding nerve fibers. We report a radial nerve palsy in a child aged 2 years in whom the diagnosis of localized hypertrophic neuropathy was made by biopsy. Resection of the affected nerve segment and sural nerve grafting produced no useful recovery after 3 years, probably because of the long duration of denervation. When this mononeuropathy presents in early childhood, uncertainty over the time of onset can lead to difficulty in distinguishing this potentially treatable lesion from congenital and other causes of nerve palsy.

Child, Preschool↗

PubMed2002

Proinflammatory cytokine (TNFalpha/IL-1alpha) induction of human osteoclast formation.

TNFalpha and IL-1alpha are potent stimulators of bone resorption in vivo and in vitro. Recently, it has been demonstrated that these two cytokines directly induce osteoclastogenesis in mouse marrow cultures. This study determined whether TNFalpha (+/- IL-1alpha) is also capable of inducing human osteoclastogenesis. The CD14(+) monocyte fraction of human peripheral mononuclear cells was cultured with TNFalpha +/- IL-1alpha in the presence of M-CSF. TNFalpha induced the formation of multinucleated cells (MNCs) which were positive for TRAP, VNR and cathepsin K and showed evidence of resorption pit formation. IL-1alpha stimulated TNFalpha-induced lacunar resorption two- to four-fold. Osteoprotegerin, the decoy receptor for RANKL, did not inhibit this process. Anti-human IL-1alpha neutralizing antibodies significantly inhibited resorption without inhibiting the formation of TRAP(+)/VNR(+) MNCs. These results suggest that, in the presence of M-CSF, TNFalpha is sufficient for inducing human osteoclast differentiation from circulating precursors by a process which is distinct from the RANK/RANKL signalling pathway.

Antibodies, Monoclonal↗