Osteochondral alterations in osteoarthritis.

Osteoarthritis (OA) is a major cause of pain and disability in the aging population, but its pathogenesis remains incompletely understood. Alterations beneath the articular cartilage at the osteochondral junction are attracting interest as possible mediators of pain and structural progression in OA. Osteochondral changes occur early during the development of OA and may aggravate pathology elsewhere in the joint. Loss of osteochondral integrity removes the barrier between intra-articular and subchondral compartments, exposing subchondral bone and its nerves to abnormal chemical and biomechanical influence. Osteochondral plasticity results in a merging of tissue compartments across the junction. Loss of the clearly differentiated demarcation between bone and articular cartilage is associated with invasion of articular cartilage by blood vessels and sensory nerves, and advancing endochondral ossification. Increased subchondral bone turnover is intimately associated with these alterations at the osteochondral junction. Cells signal across the osteochondral junction, and this cross-talk may be both a consequence of, and contribute to these pathological changes. Bone turnover, angiogenesis and nerve growth are also features of other diseases such as osteoporosis and cancers, for which therapeutic interventions are already advanced in their development. Here we review pathological changes at the osteochondral junction and explore their potential therapeutic implications for OA. This article is part of a Special Issue entitled "Osteoarthritis".

Quercetin and its principal metabolites, but not myricetin, oppose lipopolysaccharide-induced hyporesponsiveness of the porcine isolated coronary artery.

BACKGROUND AND PURPOSE: Quercetin is anti-inflammatory in macrophages by inhibiting lipopolysaccharide (LPS)-mediated increases in cytokine and nitric oxide production but there is little information regarding the corresponding effect on the vasculature. We have examined the effect of quercetin, and its principal human metabolites, on inflammatory changes in the porcine isolated coronary artery. EXPERIMENTAL APPROACH: Porcine coronary artery segments were incubated overnight at 37°C in modified Krebs-Henseleit solution with or without 1µg·mL(-1) LPS. Some segments were also co-incubated with quercetin-related flavonoids or Bay 11-7082, an inhibitor of NFκB. Changes in isometric tension of segments to vasoconstrictor and vasodilator agents were recorded. Nitrite content of the incubation solution was estimated using the Griess reaction, while inducible nitric oxide synthase was identified immunohistochemically. KEY RESULTS: Lipopolysaccharide reduced, by 35-50%, maximal contractions to KCl and U46619, thromboxane A(2) receptor agonist, and impaired endothelium-dependent relaxations to substance P. Nitrite content of the incubation medium increased 3- to 10-fold following exposure to LPS and inducible nitric oxide synthase was detected in the adventitia. Quercetin (0.1-10µM) opposed LPS-induced changes in vascular responses, nitrite production and expression of inducible nitric oxide synthase. Similarly, 10µM Bay 11-7082, 10µM quercetin 3'-sulphate and 10µM quercetin 3-glucuronide prevented LPS-induced changes, while myricetin (10µM) was inactive. Myricetin (10µM) prevented quercetin-induced modulation of LPS-mediated nitrite production. CONCLUSION AND IMPLICATIONS: Quercetin, quercetin 3'-suphate and quercetin 3-glucuronide, exerted anti-inflammatory effects on the vasculature, possibly through a mechanism involving inhibition of NFκB. Myricetin-induced antagonism of the effect of anti-inflammatory action of quercetin merits further investigation.

A comparative study of the effects of quercetin and its glucuronide and sulfate metabolites on human neutrophil function in vitro.

Exposure of neutrophils to either lipopolysaccharide (LPS) or N-formyl-methionyl-leucyl-phenylalanine (fMLP) is associated with changes in the expression of cell adhesion molecules and elevation of intracellular calcium ions. Although dietary flavonoids are reported to possess anti-inflammatory properties, little is known regarding the effect of their metabolites. We have investigated the effects of quercetin and its major metabolites on LPS and fMLP-stimulated human neutrophils using concentrations comparable to those reported in feeding studies on human volunteers. The metabolite quercetin 3-glucuronide caused a significant reduction in fMLP-evoked calcium influx in human neutrophils (approximately 35%), while neither quercetin 3'-sulfate nor quercetin produced a similar change. Acute exposure of human neutrophils to LPS altered cell shape and surface expression of CD16, but neither of these events were significantly altered by quercetin, quercetin 3-glucuronide nor quercetin 3'-sulfate. In addition, LPS caused a fivefold up-regulation in the expression of beta(2)-integrin (CD11b/Mac 1) and a concomitant 70% down-regulation of L-selectin (CD62L) adhesion molecule expression in human neutrophils. Neither effect was altered by quercetin, quercetin 3-glucuronide or quercetin 3'-sulfate. In conclusion, we found that acute exposure to quercetin and quercetin 3'-sulfate does not affect either expression of cell adhesion molecules or the elevation of intracellular calcium ions in response to LPS and fMLP in human neutrophils. However, quercetin 3-glucuronide reduced fMLP-evoked calcium responses. While this study highlights that metabolites of quercetin may possess different biological properties, dietary ingestion of quercetin is unlikely to exert a major effect on neutrophil function in vivo.

Comparative effects of quercetin and its predominant human metabolites on adhesion molecule expression in activated human vascular endothelial cells.

Adhesion of circulating monocytes to vascular endothelial cells, a critical step in both inflammation and atherosclerosis, is mediated by cross-linkage of adhesion molecules expressed on the surface of both cell types. Dietary flavonoids have been shown to have anti-inflammatory properties, decreasing the expression of cell adhesion molecules, such as vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) on endothelial cells. However, flavonoids are efficiently metabolised during absorption and the forms reaching the systemic circulation are glucuronidated, sulphated and methylated. Most previous in vitro studies of the effects of flavonoids have used the parent compounds at concentrations far higher than those physiologically achievable. We investigated the ability of quercetin and its human metabolites, at physiological concentrations (2 micromol/L and 10 micromol/L), to attenuate the inflammation-induced upregulated expression of VCAM-1, ICAM-1 and of the chemokine, monocyte chemoattractant protein-1 (MCP-1), in human umbilical vein endothelial cells (HUVECs), at the protein and transcript levels. Quercetin treatment reduced the inflammation-induced over-expression of VCAM-1 and ICAM-1 (protein and transcript) in HUVECs. Quercetin also inhibited MCP-1 gene expression. However, quercetin 3'-sulfate, quercetin 3-glucuronide and 3'-methylquercetin 3-glucuronide (isorhamnetin 3-glucuronide) generally exhibited either a reduced ability to inhibit the expression of these molecules compared with the parent aglycone or had no effect. However, all three metabolites inhibited VCAM-1 cell surface expression at 2 micromol/L. These results indicate that both quercetin and its metabolites, at physiological concentrations, can inhibit the expression of key molecules involved in monocyte recruitment during the early stages of atherosclerosis.

Neurovascular invasion at the osteochondral junction and in osteophytes in osteoarthritis.

BACKGROUND: Normal adult articular cartilage is thought to be avascular and aneural. OBJECTIVE: To describe neurovascular structures at the osteochondral junction and in osteophytes in tibiofemoral osteoarthritis (OA) displaying a range of severity of cartilage changes. METHODS: Articular surfaces were obtained from 40 patients at total knee joint replacement surgery for tibiofemoral OA (TKR) and seven patients post mortem (PM). Antibodies directed against CD34 (vascular endothelium), protein gene product 9.5 (pan-neuronal marker), substance P and calcitonin gene-related peptide (sensory nerves) and C-flanking peptide of neuropeptide Y (sympathetic nerves) were used to localise blood vessels and nerves by immunohistochemistry. Severity of OA cartilage changes was graded histologically. RESULTS: TKR and PM samples displayed a range of OA cartilage changes including tidemark breaching by vascular channels. Sympathetic and sensory nerves were both present within vascular channels in the articular cartilage, in both mild and severe OA. Perivascular and free nerve fibres, and nerve trunks were observed within the subchondral bone marrow and within the marrow cavities of osteophytes. Sensory and sympathetic nerves displayed similar distributions in each region studied. CONCLUSION: Vascularisation and the associated innervation of articular cartilage may contribute to tibiofemoral pain in OA across a wide range of structural disease severity.

IMPROVED ACCURACY RATES OF FNAC INTERPRETATION IN BENIGN BREAST LESIONS.

We carried out a retrospective study of 194 biopsy proved benign breast lesions comparing the fine needle aspiration cytology (FNAC) diagnosis offered earlier. We reviewed the cytology smears based on recently advocated criteria and offered our fresh diagnosis. It was observed that we still overdiagnosed five cases of fibroadenomas and underdiagnosed four cases of fibrocystic change. However the quantum of such discrepancies decreased considerably than seen earlier. We could correctly diagnose two tubular adenomas and two intraductal papillomas. We also reduced the number of nonspecific diagnosis of benign breast disease from 24 to 08. Hence we could register an overall improvement of accuracy rate to 84.5% as compared to 58.8% achieved earlier.