[Dephosphorelation of Bad and upregulation of Bcl-2 in hippocampus of rats following limbic seizure induced by kainic acid injection into amygdaloid nucleus]

The purpose of the present study was to explore the seizure-induced changes in Bad (Bcl-2-associated death protein), 14-3-3, phosphoBad, Bcl-2 and Bcl-XL expression in the rat model of focal limbic seizure. Unilateral intra-amygdaloid injection of kainic acid (KA) was made to induce seizure. Electroencephalogram (EEG) and regional cerebral flow (r-CBF) were monitored continuously. Diazepam (30 mg/kg) was administered to terminate the seizure. The apoptotic and surviving neurons in the hippocampus were observed by terminal deoxynucleotidyl transferrase-mediated dUTP nick end labeling (TUNEL) and cresyl violet staining, the expression of Bad, 14-3-3, phosphoBad, Bcl-2 and Bcl-XL were detected with immunofluorescence, Western blot and immunoprecipitation. The results showed that TUNEL-positive neurons appeared at 8 h and reached maximum at 24 h following seizure cessation within the ipsilateral CA3 subfield of the hippocampus. Seizure induced the dephosphorylation of Bad and the dissociation of Bad from its chaperone protein 14-3-3 and subsequent dimerization of Bad with Bcl-XL. The expression of phosphoBad decreased and Bcl-2 increased. There was little change in r-CBF after the seizure. These results suggest that seizure leads to a dephosphorylation of Bad and an upregulation of Bcl-2. Dephosphorylation of Bad may be injurious while the upregulation of Bcl-2 may be protective to the brain damage induced by seizures, but not related with r-CBF.

[The expression of Smac and XIAP in rat hippocampus following limbic seizure induced by kainic acid injection into amygdaloid nucleus]

To determine whether Smac/DIABLO (second mitochondrial activator of caspases/direct inhibitor of apoptosis protein-binding protein of low isoelectric point [PI]) and XIAP (X-chromosome-linked inhibitor of apoptosis protein) serve to regulate neuronal apoptosis following seizures, we investigated seizure-induced changes in caspase-9, Smac/DIABLO and XIAP protein expression and the in vivo effect of caspase-9 inhibition. Animals received unilateral intra-amygdaloid injection of kainic acid (0.5 microg) to induce seizures for 1 h. The seizures were then terminated by diazepam (30 mg/kg). Animals were killed 0, 2, 4, 8, 24 or 72 h following diazepam administration. The apoptotic and surviving neurons in hippocampus were observed by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and cresyl violet staining, the expression of Smac/DIABLO, XIAP and caspase-9 was detected with immunofluorescence and western blot. The results showed that the levels of XIAP and the 46-kDa proenzyme form of caspase-9 were unaffected by the seizures. The expression of Smac increased at 2 h and the 37-kD cleaved fragment of caspase-9 was detected at 4 h, TUNEL-positive neurons appeared at 8 h and reached maximal at 24 h following seizure cessation within the ipsilateral (the same side as the intra-amygdaloid injection of kainic acid) CA3 subfield of the hippocampus. Intracerebroventricular infusion of caspase-9 inhibitor z-LEHD-fluoromethyl ketone (z-LEHD-fmk) significantly decreased TUNEL-positive neurons and increased the number of surviving cells. Caspase-9 immunoreactivity increased and Smac/DIABLO, XIAP immunoreactivity became extensive within the ipsilateral CA3 neurons. TUNEL-positive neurons and the alterations of the expression of Smac/DIABLO and XIAP within the ipsilateral CA3 were not detected within the contralateral hippocampus. These results suggest that seizures lead the translocation of Smac/DIABLO into the cytosol, the activation of caspase-9 and the change of subcellular locoalization of XIAP. These changes may play a role in the brain damage induced by seizures. Caspase-9 is possibly a potential therapeutic target in the treatment of brain injury associated with seizures.

Imbalance of RANKL/RANK/OPG system in interface tissue in loosening of total hip replacement

In the differentiation of osteoclasts the differentiation factor (RANKL) interacts with the receptor activator of NF-κB (RANK) in a direct cell-to-cell contact between osteoblast and (pre)osteoclast. This is inhibited by soluble osteoprotegerin (OPG). The mRNA levels of both RANKL (p < 0.01) and RANK (p < 0.05) were high in peri-implant tissue and RANKL+ and RANK+ cells were found in such tissue. Double labelling also disclosed soluble RANKL bound to RANK+ cells. We were unable to stimulate fibroblasts to express RANKL in vitro, but monocyte activation with LPS gave a fivefold increase in RANK mRNA levels. In contrast to RANKL and RANK expression in peri-implant tissue, expression of OPG was restricted to vascular endothelium. Endothelial cell OPG mRNA levels were regulated by TNF-α and VEGF, but not by hypoxia. It is concluded that activated cells in the interface tissue overproduce both RANKL and RANK and they can interact without interference by OPG.

Salivary gland scintigraphy in Sjögren's syndrome and patients with sicca symptoms but without Sjögren's syndrome: the psychological profiles and predictors for salivary gland dysfunction

OBJECTIVE

To characterise the psychological profiles of Sjögren's syndrome (SS) and patients with sicca symptoms but without SS; to find predictors for salivary gland function; to evaluate salivary scintigraphy as a method to differentiate between SS and patients with sicca symptoms but without SS.

PATIENTS AND METHODS

Psychological tests (Medical Outcomes Study Short Form General Health Survey (SF-36), Jenkins Activity Survey, Toronto Alexithymia Scale, and Maastricht Questionnaire for vital exhaustion) were performed and assessment of the function of the salivary glands made in 26 patients with primary SS, 8 with secondary SS, and 9 with sicca symptoms but without SS. Data were analysed with BMDP new system version 1.0 statistical program.

RESULTS

Psychological profiles were similar in all groups. Hb, RF, ANA, and SSA differentiated between the groups. Results of salivary scintigraphy were predicted to 51% by ANA, SSA, SSB, IgG, IgA, diagnosis, vitality, and role limitations due to emotional problems. No predictors were found for the resting salivary flow. Salivary scintigraphy was pathological in 21/26 (81%) and in 8/8 (100%) patients with secondary SS, but only in 2/9 (22%) patients with sicca symptoms without SS (p=0.002) (sensitivity 85.3%, specificity 77.8%).

CONCLUSIONS

Patients with sicca symptoms but without SS have sickness behaviour similar to that of patients with SS. The results of salivary scintigraphy can be predicted by diagnosis and autoimmune findings; psychological characteristics added 20% to this predictive value. Distinction between SS and patients with sicca symptoms but without SS is difficult, but in addition to autoantibodies, salivary scintigraphy can be used for this purpose.

Complete nucleotide sequence and genome organization of a Chinese isolate of tobacco bushy top virus

The complete nucleotide sequence of a Chinese isolate of tobacco bushy top virus (TBTV), designated TBTV-Ch, was determined from cDNA generated from double-stranded RNA extracted from diseased tobacco. The genome is 4152 nucleotides (nt) in size, contains four putative open reading frames (ORFs) and untranslated regions of 10 nt and 645 nt at the 5' and 3' ends, respectively. In genome organization and in the amino acid sequence of its potential products, the RNA of TBTV-Ch is similar to other umbraviruses sequenced to date. The results suggested that TBTV should be regarded as a definitive species of the genus Umbravirus.

Expression of caspase-1 in synovial membrane-like interface tissue around loosened hip prostheses

Caspase-1 expression in synovial membrane-like interface tissue (SMLIT) around loosened hip prostheses and osteoarthritic synovial samples was studied. Caspase-1 mRNA was found in SMLIT and synovial tissue. There is no difference in the copy numbers of caspase-1 mRNA between these samples. Both precursor and active forms of caspase-1 proteins appeared in these samples, but the number of positive cells was higher in SMLIT than in synovial tissue. Double labeling revealed that most caspase-1-positive cells were macrophages and fibroblasts. In the lining-like layers and deep stroma of SMLIT, many cells were double positive for active caspase-1 and interleukin-1 beta (IL-1beta). In contrast, the number of active caspase-1/IL-18 double-positive cells was very low. We conclude that caspase-1 synthesis is increased in SMLIT. Caspase-1 can be involved in implant loosening by processing IL-1beta precursor into its mature form, which is a potent osteoclast-activating factor and a major proinflammatory mediator.

Interleukin-6 in aseptic loosening of total hip replacement prostheses

OBJECTIVE

To investigate the level of interleukin-6 (IL-6) expression in the synovial-like interface membrane (SLIM) and in the pseudosynovial tissue surrounding the artificial hip joints, as well as in the pseudosynovial fluid from aseptically loosened total hip replacement (THR) prostheses.

METHODS

A series of methods were used in this study including immunohistochemical staining, double immunofluorescence labeling, enzyme-linked immunosorbent assay (ELISA), and reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTS

IL-6 was found in all SLIM and the pseudosynovial tissue samples from aseptic loosening of THR. Semi-quantitative morphometry showed that IL-6 containing cells were more numerous in the SLIM (911 +/- 197; p < 0.01) and the pseudosynovial tissue samples (883 +/- 310; p < 0.01) than in the control synovial tissue (291 +/- 184). Double labeling confirmed that macrophages and fibroblasts were the predominant cell types expressing IL-6. These findings were confirmed by RT-PCR. ELISA revealed no difference in the IL-6 concentration between the pseudosynovial fluid and the control synovial fluid obtained from the patients undergoing hip arthroscopy.

CONCLUSIONS

IL-6 locally produced in SLIM may in a paracrine manner contribute to periprosthetic osteolysis of the nearby bone. In contrast, fluid phase IL-6 does not seem to contribute to this end.

Dendritic cells in rheumatoid synovial membrane after total removal of the hyaline articular cartilage

OBJECTIVE

To investigate the effect of total removal of the hyaline articular cartilage on dendritic cells in synovial membrane in rheumatoid arthritis (RA) or ankylosing spondylitis (AS).

PATIENTS AND METHODS

Immunohistochemical staining for two dendritic cell markers, CD35 and RFD1, was carried out on synovial membrane specimens from arthritis patients undergoing primary (n=10) or revision (n=8) total hip replacement (THR). The results are expressed as the number (mean+/-standard deviation) of positive cells per 1000 total cells.

RESULTS

CD35-(112+/-9) and RFD1-(27+/-5) positive cells were found in all primary RA synovial membrane, while only two out of eight synovial membrane samples from revision THR contained CD35-positive follicular dendritic cells (nine and 12 cells), and no revision samples contained any RFD1-positive interdigitating dendritic cells.

CONCLUSION

Removal of the hyaline articular cartilage reduces the infiltration and functional differentiation of dendritic cells in synovial membrane. Our findings suggest that the antigen driving chronic arthritis/synovitis is contained in the hyaline articular cartilage.

Expression of parathyroid hormone related protein in the tissue around loosened hip prostheses

OBJECTIVE

To investigate the eventual presence and cellular source ofparathyroid hormone related protein (PTHrP) in the synovial-like interface membrane from aseptic loosening of total hip replacement (THR).

METHODS

A polyclonal rabbit antiserum to the amino-terminal peptide of human PTHrP was used to stain 10 interface membrane samples from loose THR and 10 synovial tissue samples from hip osteoarthritis (OA). Quantitative microscopic assessment was done with a computer-assisted image analysis system. Western blotting was applied to verify the presence of PTHrP in both tissue samples. Double immunofluorescence labelling aimed to reveal the cellular sources of PTHrP.

RESULTS

Immunoreactive PTHrP was found in all interface membrane and OA synovial tissue samples. The number of PTHrP positive cells in interface membrane was much higher than in OA synovial tissue. Positive cells were most commonly seen in the lining-like layers and sublining area of interface membrane. Double immunofluorescence labelling showed that most macrophages and fibroblasts in interface membrane were PTHrP positive. Western blotting revealed the 24-25 KD bands in both tissue samples.

CONCLUSIONS

PTHrP expression is upregulated in interface membrane around loosened hip prostheses. Locally accumulated PTHrP may contribute to periprosthetic osteolysis and aseptic loosening of THR through its direct effects on bone, or indirectly via the induction of inflammatory mediators.

Acid attack and cathepsin K in bone resorption around total hip replacement prosthesis

Normal bone remodeling and pathological bone destruction have been considered to be osteoclast-driven. Osteoclasts are able to attach to bare bone surface and produce an acidic subcellular space. This leads to acid dissolution of hydroxyapatite, allowing cathepsin K to degrade the organic type I collagen-rich osteoid matrix under the acidic condition prevailing in Howship lacunae. Using a sting pH electrode, the interface membrane around a loosened total hip replacement prosthesis was found to be acidic. Confocal laser scanning disclosed irregular demineralization of the bone surface in contact with the acidic interface. Cathepsin K, an acidic collagenolytic enzyme, was found in interface tissue macrophages/giant cells and pseudosynovial fluid. Tissue extracts contained high levels of cathepsin K messenger RNA (mRNA) and protein. These observations suggest the presence of an acid- and cathepsin K-driven pathological mechanism of bone resorption, mediated not by osteoclasts in subosteoclastic space, but rather by the uncontrolled activity of macrophages in extracellular space.

Removal of hyaline articular cartilage reduces lymphocyte infiltration and activation in rheumatoid synovial membrane

OBJECTIVE

To analyze the effect of removal of hyaline articular cartilage on synovial membrane pathology in chronic arthritis.

METHODS

Synovial membrane samples were obtained from patients with rheumatoid arthritis or ankylosing spondylitis in association with total hip arthroplasty, either primary or revision surgery. Synovial membrane histopathology was assessed by immunochemical staining and morphometry.

RESULTS

CD68 positive macrophages were common in revision synovial membranes. In contrast, T lymphocytes were much more common in primary rheumatoid synovial membranes (p < 0.001). Many T lymphocytes in primary synovial membrane were HLA-D/DR positive (p < 0.001) and interleukin 2 receptor (IL-2R) positive (p < 0.001) and contained interferon-gamma(IFN-gamma; p < 0.001) and tumor necrosis factor-beta (TNF-beta; p < 0.001). In contrast, revision synovial membranes from patients with chronic arthritis contained only a few HLA-D/DR positive T cells and practically no IL-2R, IFN-gamma, or TNF-beta positive activated T lymphocytes.

CONCLUSION

The components of hyaline articular cartilage may be the source of autoantigen responsible for perpetuation of chronic arthritides.

Hyaluronan synthases, hyaluronan, and its CD44 receptor in tissue around loosened total hip prostheses

Aseptic loosening of prosthetic components, the most common long-term complication after total hip replacement (THR), is characterized by the formation of a synovial membrane-like interface tissue (SMLIT). It was hypothesized that the hyaluronan synthase (HAS)/hyaluronan (HA)/HA receptor CD44 signalling system is responsible for the synovial-like differentiation of the interface membrane. SMLIT was therefore compared with osteoarthritis (OA) synovial membrane by using reverse transcriptase polymerase chain reaction (RT-PCR) of HAS 1, 2 and 3, histochemical HA assay, and immunohistochemistry of CD44 and its non-HA ligands. All three isoforms of HAS were found in these samples. HA and CD44 were most abundant in the lining, but the signal was actually stronger in aseptic loosening than in OA (p<0.01). The non-HA CD44 ligands, collagen type VI, fibronectin, osteopontin, and MCP-1, had a similar distribution pattern in both tissues. These results confirm the synovial-like structure of the interface tissue lining. The pressure waves and movement of the HA-rich pseudosynovial fluid seem to drive HA into the implant-to-host interface, which itself also produces HA. HA may be responsible for the induction of a synovial-like lining at the interface through HA-CD44 signalling.

No lymphokines in T-cells around loosened hip prostheses

Research results have been contradictory about the role of lymphocytes and immune response in aseptic loosening of total hip replacement (THR). Conclusive evidence is still lacking in spite of extensive in vivo and in vitro studies. Our study was designed to check whether T-cells were activated and if they produced lymphokines in synovial membrane-like interface tissue around loosened THRs. Tissue sections were stabilized and permeabilized to allow the cytokine-specific antibodies to penetrate through the cell membrane and the membranes of intracellular organelles. This technique, combined with computer-assisted image analysis, permits the detection and quantitation of lymphokine-producing cells. We found that the number of T-cells was low, and none of the T-cells was activated, as shown by the absence of interleukin-2 receptor (IL-2R) immunoreactivity. There was no cell producing lymphokines, such as interleukin-2 (IL-2), interferon-gamma (IFN-gamma), and tumor necrosis factor-beta (TNF-beta). Our results suggest that T-cell-mediated immune response is not actively involved in aseptic loosening of THR.

Distribution of tenascin-X in different synovial samples and synovial membrane-like interface tissue from aseptic loosening of total hip replacement

The distribution of tenascin-X (Tn-X) was investigated in synovial samples from rheumatoid arthritis (RA), osteoarthritis (OA) and knee injuries, and in synovial membrane-like interface tissue (SMLIT) from aseptic loosening of total hip replacement (THR). An affinity purified rabbit antiserum against Tn-X was applied in avidin-biotin-peroxidase complex method. Double immunofluorescence labeling was used to assess the spatial relationship of Tn-X and Tn-C. All samples showed Tn-X immunoreactivity. Strong staining appeared in the lining and lining-like layers of RA and SMLIT samples, respectively. An intensive immunoreactivity was also found in pannus tissue in RA, and around multinucleate giant cells and polyethylene wear debris in SMLIT. Staining intensity/extent varied significantly in different samples in the following rank order: SMLIT, RA, OA, knee synovium membrane. Double labeling revealed two patterns of Tn-X/Tn-C distribution, reciprocal and co-localization. Our results suggest that Tn-X is an essential component of normal synovial membrane, and that inflammatory mediators may increase local Tn-X production. Tn-X distribution is not always reciprocal to that of Tn-C.

Increased interleukin-8 (IL-8) expression is related to aseptic loosening of total hip replacement

Aseptic loosening is an increasing problem in total hip replacement (THR). Chronic inflammatory reaction against implant wear particle results in collageno- and osteolysis, leading to loosening of the implant. Cytokines are known to play a major role in this particular inflammatory process. The aim of the present study was to examine interleukin-8 (IL-8) in the synovial-like interface membrane (SLIM) and pseudocapsular tissue of THRs and to compare it to normal knee synovial membrane. Eleven patients suffering from aseptically loosened THRs were included. All the SLIM and pseudocapsular tissue samples were obtained during revision operations. Ten control samples of normal synovium were collected per arthroscopy from the superior recessus of the knee. For immunohistochemical IL-8 detection, polyclonal mouse anti-human immunoglobulin (Ig)G1 IL-8-primary antibody was used with the alkaline phosphatase anti-alkaline phosphatase (APAAP) method. Results were quantitated using the Vidas image analysis system. The highest count levels (mean +/- SEM) were detected in SLIM tissue (386+/-82 cells/mm2). The difference was statistically significant compared with pseudocapsular tissue (193+/-36 cells/mm2) and control samples (18+/-5 cells/mm2). Count levels in control tissue were on average 5% of the SLIM tissues values. The present study determines for the first time the cellular origin of IL-8 in aseptically loosened THRs and also quantitates the IL-8-producing cells in the periprosthetic tissue. The results reveal a high rise in IL-8 concentration in SLIM and in synovial tissues. This finding moves us one step forward in solving the complex network of multiple factors affecting loosening of hip implants.

Expression of epidermal growth factor and transforming growth factor alpha in interfacial membranes retrieved at revision total hip arthroplasty

BACKGROUND

The interfacial membrane between bone and implant has been shown to be a key tissue in the process of aseptic loosening of total hip arthroplasty. The cells within the interfacial membrane produce numerous inflammatory mediators which, through complex mechanisms, cause periprosthetic osteolysis and aseptic loosening. Both epidermal growth factor (EGF) and transforming growth factor alpha (TGFalpha) have similar biological functions. They have been found to stimulate bone resorption.

OBJECTIVE

To investigate the presence, cellular localisation, and extent of expression of EGF and TGFalpha in interfacial membrane retrieved from revision total hip arthroplasty and compare it with that in synovial membrane from primary total hip arthroplasty.

METHODS

Ten interfacial membranes and 10 synovial membranes were stained with avidin-biotin-peroxidase complex for EGF and TGFalpha. The staining process was done using the Lab Vision Autostainer. The results were measured by a semiautomatic VIDAS image analysis system.

RESULTS

Immunoreactivity for both EGF and TGFalpha was found in the endothelial cells of blood vessels, macrophages, and fibroblasts, both in interfacial membranes and synovial membranes. However, the number of EGF (980 (370)) and TGFalpha (1070 (360)) positive cells per mm(2) was greater in interfacial membranes than in the synovial membranes (220 (200), 270 (100); p<0.01).

CONCLUSION

It is suggested that owing to their increased expression in interfacial membrane, EGF and TGFalpha may have an important pathogenetic role in stimulating periprosthetic bone resorption in aseptic loosening of total hip arthroplasty.

Distribution of fibronectins and their integrin receptors in interface tissue from aseptic loosening of hip prostheses

OBJECTIVES

To assess the distribution of fibronectins (FNs) and their integrin (Int) receptors in synovial membrane-like interface tissue (SMLIT) from aseptic loosening of total hip replacement (THR), and potential role of FN-Int interaction in the loosening process.

METHODS

The alkaline phosphatase anti-alkaline phosphatase (APAAP) method was used to detect the distribution of FNs and their Int receptors in SMLIT and control samples. Double immunofluorescence labeling was used to reveal the different co-localizations.

RESULTS

Intensive FN staining appeared in the lining layers, sublining area, and vascular endothelium, while immunoreactivities for Int alpha 4, alpha 5, beta 1 subunits were detected in the lining and endothelial cells of SMLIT. Immunofluorescence labeling revealed Int alpha 5 and collagenase-1/collagenase-3 double positive cells in lining layers and sublining area of SMLIT.

CONCLUSION

Increased expression of FNs, Int alpha 4 beta 1 and alpha 5 beta 1 appeared in SMLIT compared with that in OA synovial membrane. FN-Int interactions may play a role in local collagenase production.

Expression of vitronectin and its integrin receptors in the synovial membrane-like interface tissue from aseptic loosening of total hip replacement

OBJECTIVE

To investigate expression of vitronectin (VN) and its integrin (Int) receptors in synovial membrane-like interface tissue (SMLIT) in aseptic loosening of total hip replacement (THR), and the potential role of VN-Int interaction in production of collagenase-3.

METHODS

Avidin-biotin-peroxidase complex (ABC) staining was used to detect distribution of VN and Int alphaV, beta3, and beta5 subunits. Immunofluorescence labeling with FITC and TRITC conjugated IgG was used to localize Int beta3 subunit and matrix metalloproteinase (MMP-13) double positive cells in SMLIT.

RESULTS

Intensive VN immunoreactivity was found in the lining-like layers, sublining area, and endothelium of SMLIT. Statistical analysis of the VN staining score revealed a significant difference between SMLIT and control synovial membrane. All 3 Int subunits appeared in the lining-like layers and sublining area. The Int beta3 subunit was also detected in giant cells of SMLIT. Int beta5 subunit staining was relatively weak and rarely found in vascular endothelium. Immunofluorescence labeling showed many double positive cells in the lining-like layer and sublining area of SMLIT.

CONCLUSION

Expressions of VN and Int alphaVbeta3 and alphaVbeta5 are increased in SMLIT compared with that in OA synovial membrane. Int alphaVbeta3 engagement with VN might play a potential role in local MMP-13 production in SMLIT.

Increased expression of extracellular matrix metalloproteinase inducer in rheumatoid synovium

OBJECTIVE

To investigate the expression of extracellular matrix metalloproteinase inducer (EMMPRIN) in the synovial membrane of patients with rheumatoid arthritis (RA) and osteoarthritis (OA).

METHODS

Mouse monoclonal antibody against human EMMPRIN was applied according to an avidin-biotin-peroxidase complex method to reveal EMMPRIN expression. Western blotting and reverse transcriptase-polymerase chain reaction (RT-PCR) were performed to check for the presence of EMMPRIN protein and messenger RNA (mRNA).

RESULTS

EMMPRIN immunoreactivity was more intense in RA than in OA synovial membrane (P < 0.01). EMMPRIN staining was more widespread in RA than in OA, especially in association with macrophage infiltrates. RT-PCR of synovial membrane samples disclosed the presence of EMMPRIN mRNA. Nucleotide sequencing of the PCR amplification products confirmed the identity of the amplified bands. Immunoblot analysis revealed 55-kd glycosylated EMMPRIN bands, which were particularly prominent in RA samples.

CONCLUSION

The expression of EMMPRIN is upregulated in the rheumatoid synovial membrane. EMMPRIN can induce local production of at least MMPs 1, 2, and 3, and can thereby play a role in joint destruction in RA.

Fibroblast biology. Signals targeting the synovial fibroblast in arthritis

Fibroblast-like cells in the synovial lining (type B lining cells), stroma and pannus tissue are targeted by many signals, such as the following: ligands binding to cell surface receptors; lipid soluble, small molecular weight mediators (eg nitric oxide [NO], prostaglandins, carbon monoxide); extracellular matrix (ECM)-cell interactions; and direct cell-cell contacts, including gap junctional intercellular communication. Joints are subjected to cyclic mechanical loading and shear forces. Adherence and mechanical forces affect fibroblasts via the ECM (including the hyaluronan fluid phase matrix) and the pericellular matrix (eg extracellular matrix metalloproteinase inducer [EMMPRIN]) matrices, thus modulating fibroblast migration, adherence, proliferation, programmed cell death (including anoikis), synthesis or degradation of ECM, and production of various cytokines and other mediators [1]. Aggressive, transformed or transfected mesenchymal cells containing proto-oncogenes can act in the absence of lymphocytes, but whether these cells represent regressed fibroblasts, chondrocytes or bone marrow stem cells is unclear.

Transforming and epidermal growth factors in degenerated intervertebral discs

We studied the presence of anabolic growth factors in human herniated intervertebral discs (IVD) using a reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry. Messenger RNA (mRNA) was isolated from the nucleus pulposus using oligo (dT)25 superparamagnetic beads and probing with gene-specific primers in RT-PCR. mRNA coding for TGF-alpha (3/10), EGF (0/10), TGF-beta1 (0/10) and TGF-beta3 (2/10) or the EGF receptor (EGF-R; 0/10) and TGF-beta type-II receptor (0/10) was found only occasionally. Beta-actin was always present and positive sample controls confirmed the validity of the RT-PCR assay. These RT-PCR findings were confirmed using immunohistochemical staining of EGF and TFG-beta, whereas TGF-alpha protein was always found associated with discocytes. We conclude that the nucleus pulposus of the herniated IVD is vulnerable to proteolytic degradation and depletion of proteoglycans due to the lack and/or low production of anabolic growth factors/receptors which could increase the local synthesis of the extracellular matrix.

Expression of laminins and their integrin receptors in different conditions of synovial membrane and synovial membrane-like interface tissue

OBJECTIVE

To demonstrate the expression of laminins (Lns) and their integrin (Int) receptors in different synovial samples and synovial membrane-like interface tissues from well fixed and aseptically loosened total hip replacement (THR), and the potential role of Ln-Int interaction in the production of collagenases and cytokines.

METHODS

Immunohistochemical staining was done to detect the distribution of EHS Ln, Ln alpha2, alpha3, alpha5, beta1, beta2 chains and Int alpha1, alpha2, alpha3, alpha6, beta1, beta4 subunits in different samples. Double immunofluorescence labelling was used to find colocalisation of Int alpha6 subunit and collagenase-1/collagenase-3/TNFalpha/IL6.

RESULTS

General Ln immunoreactivity was detected in all specimens. Ln alpha5, beta1 and beta2, but not alpha2 and alpha3 chains were seen in the synovial lining and the basement membrane of blood vessels with the intensity/extent of labelling in the following rank order: rheumatoid arthritis (RA) loosened prostheses, osteoarthritis, well fixed prostheses, traumatic knees. Among Int subunits, staining for beta1 was usually the strongest, followed by staining for Int alpha6, alpha1, alpha3, and alpha2 subunits, with the same rank order for overall expression of Lns. Int beta4 subunit was not detectable in most of the specimens. Double labelling focused on Int alpha6 subunit disclosed its frequent colocalisation with collagenases 1 and 3 and with tumour necrosis factor alpha and interleukin 6 in synovial lining.

CONCLUSION

Synovial lining contains Ln-10, Ln-11, and Int alpha6beta1 and alpha1beta1 receptors. In aseptic loosening of THR, interface tissue has a similar Ln subtype and Int receptor composition as RA synovium, which confirms its "lining-like" phenotype. Synovial lining does not contain Ln-5 (alpha3beta3gamma2) or Int alpha6beta4, which are components of epithelial hemidesmosomes. The expression of Lns and their Int receptors is upregulated in inflammation. The close spatial relation between Ln and its Int receptors in synovial lining cells containing proteinases and cytokines suggests a potential role in joint destruction and prosthetic loosening.

Increased expression of EMMPRIN in the tissue around loosened hip prostheses

Matrix metalloproteinases (MMPs) have been shown to play a role in aseptic loosening of total hip replacement (THR). Extracellular matrix metalloproteinase inducer (EMMPRIN) can upregulate expression of several MMPs but has little effect on their tissue inhibitor (TIMP). Using the avidin-biotin-peroxidase complex immunostaining method, we detected strong immunoreactivity of EMMPRIN in the lining-like layers, sublining area and vascular endothelium of synovial membrane-like interface tissue around loosened prostheses. In contrast, EMMPRIN staining was very weak in the synovial samples from patients with hip arthrosis. Double immunofluorescence labeling revealed EMMPRIN/MMP-1 double-positive cells in lining-like layers and the sublining area of interface tissue. Our findings indicate that EMMPRIN expression is upregulated in interface tissue, and that locally accumulated EMMPRIN may modulate MMP-1 expression. An imbalance in the activity of MMPs and TIMP may lead to tissue destruction and periprosthetic osteolysis. These biological responses, combined with mechanical stress caused by micromotion and oscillating fluid pressure, may eventually cause aseptic loosening of THR.

T(H)1 cytokines are produced in labial salivary glands in Sjögren's syndrome, but also in healthy individuals

The aim of the present study was to assess the T cell cytokines IFN-gamma, IL-2, IL-4 and IL-5 in labial salivary glands (LSG) in Sjögren's syndrome (SS) and healthy controls using RT-PCR and immunohistochemistry. IFN-gamma is always or almost always produced in SS and in healthy controls. IL-2 was also found in some samples, but IL-4 and IL-5 were not. Less than 2% of all inflammatory mononuclear cells contained immuoreactive IFN-gamma or IL-2. Cytokine mRNA profile in LSGs in SS is skewed towards a T(H)1 pattern. The classical T(H)1 cytokines are also produced in normal glands, even in the absence of foci. T(H)1 type response may play an active role as part of the mucosal associated lymphoid tissue/responses, perhaps in prevention of reactivation of latent viruses. This may also make the exocrine glands a locus minoris resistentiae when the self tolerance is broken.

Cathepsin G in degenerating and healthy discal tissue

OBJECTIVES

To assess the eventual presence, tissue localization, molecular forms, amount and activity of cathepsin G in the annulus fibrosus.

METHODS

Normal non-autolytic disc tissue was collected from cadavers within six hours after death. Degenerate disc samples were collected from low back pain patients undergoing anterior interbody fusion due to severe, discographically verified and painful disc degeneration, and from the posterior parts of intervertebral discs from 10 patients undergoing microscopic discoidectomy because of intervertebral herniation. Avidin-biotinperxidase complex staining of cathepsin G was quantitated by morphometry. Cellular localization was analyzed using double immunofluorescence staining of cathepsin G and CD68, proline 4-hydroxylase or von Willebrand factor. Neutral salt extracts were analyzed by using synthetic cathepsin G substrate in spectrophotometry, dot-immunoblotting and Western blotting.

RESULTS

Histological and morphometric image analysis showed increased cellularity, increased numbers of cathepsin G positive cells and neovascularization in degenerated discs compared to control discs. Neutral salt extract of disc tissue, degenerated or normal, in contrast to control material from synovial capsular tissue, did not contain measurable cathepsin G activity, although immunoreactive enzyme was detected in dot-immunoblotting. Western blotting demonstrated that the discal cathepsin G had an apparent molecular weight of 27 kDa.

CONCLUSION

Due to its properties and localization in normal and pathologically altered tissue, cathepsin G probably plays both a direct and an indirect role in extracellular matrix degradation in the annulus fibrosus. Extracted cationic cathepsin G was immunoreactive, but was functionally inhibited by serpins or, more likely, by polyanionic proteoglycans and saccharins derived from the connective tissue matrix of the annulus fibrosus.