Quantification of the flux of tyrosine pathway metabolites during nitisinone treatment of Alkaptonuria.

Nitisinone decreases homogentisic acid (HGA) in Alkaptonuria (AKU) by inhibiting the tyrosine metabolic pathway in humans. The effect of different daily doses of nitisinone on circulating and 24 h urinary excretion of phenylalanine (PA), tyrosine (TYR), hydroxyphenylpyruvate (HPPA), hydroxyphenyllactate (HPLA) and HGA in patients with AKU was studied over a four week period. Forty AKU patients, randomised into five groups of eight patients, received doses of 1, 2, 4 or 8 mg of nitisinone daily, or no drug (control). Metabolites were analysed by tandem mass spectrometry in 24 h urine and serum samples collected before and after nitisinone. Serum metabolites were corrected for total body water and the sum of 24 hr urine plus total body water metabolites of PA, TYR, HPPA, HPLA and HGA were determined. Body weight and urine urea were used to check on stability of diet and metabolism over the 4 weeks of study. The sum of quantities of urine metabolites (PA, TYR, HPPA, HPLA and HGA) were similar pre- and post-nitisinone. The sum of total body water metabolites were significantly higher post-nitisinone (p < 0.0001) at all doses. Similarly, combined 24 hr urine:total body water ratios for all analytes were significantly higher post-nitisinone, compared with pre-nitisinone baseline for all doses (p = 0.0002 - p < 0.0001). Significantly higher concentrations of metabolites from the tyrosine metabolic pathway were observed in a dose dependant manner following treatment with nitisinone and we speculate that, for the first time, experimental evidence of the metabolite pool that would otherwise be directed towards pigment formation, has been unmasked.

Evaluation of cartilage, synovium and adipose tissue as cellular sources for osteochondral repair.

Osteochondral lesions are a major cause of pain and disability in several species including dogs, horses and human beings. The objective of this study was to assess three potential sources of canine cells for their osteochondral regenerative potential. Cartilage, synovium and adipose tissue cells were grown in pellet culture in chondrogenic or osteogenic media. Cartilage-derived pellets displayed the best chondrogenic differentiation as indicated by significantly higher COL2A1 and SOX9 mRNA expression, greater glycosaminoglycan content, and higher retention of Safranin-O stain compared to the synovium and adipose-derived cells. Following application of the osteogenic media, all three cell sources exhibited small areas of positive alizarin red staining. Poor intracellular alkaline phosphatase activity was found in all three cell types when stimulated although osteocalcin and RUNX2 expression were significantly increased. Cells isolated and cultured from canine articular cartilage retained their specific chondrocytic phenotype. Furthermore, canine adipocytes and synovial cells did not undergo chondrogenic differentiation and did not exhibit evidence of multipotency. Although osteogenic differentiation was initiated at a genomic level, phenotypic osteoblastic differentiation was not observed. The findings of this study suggest that cells isolated from canine adipose tissue and synovium are sub-optimal substitutes for chondrocytes when engineering articular cartilage in vitro.

Human clinical experience with adipose precursor cells seeded on hyaluronic acid-based spongy scaffolds.

Histioconductive approaches to soft-tissue defects use scaffolds seeded with lineage- and tissue-specific progenitors to generate tissue which should reside in equilibrium with adjacent tissue. Scaffolds guide histiogenesis by ensuring cell-cell and cell-matrix interactions. Hyaluronic acid-based (HA) preadipocyte-seeded scaffolds were evaluated for their adipo-conductive potential and efficacy in humans. Preadipocytes were isolated from lipoaspirate material and seeded on HA scaffolds. The cellular bio-hybrid (ADIPOGRAFT) and an acellular control scaffold (HYAFF11) were implanted subcutaneously. At specific time points (2, 8 and 16 weeks) explants were analyzed histopathologically with immunohistochemistry. No adverse tissue effects occurred. Volume loss and consistent degradation of the HYAFF11 scaffolds compared to the ADIPOGRAFT group indicated progressive tissue integration. No consistent histological differences between both groups were observed. By 8 weeks all void spaces within the scaffolds were filled with cells with pronounced matrix deposition in the ADIPOGRAFT bio-hybrids. Here we show that HA scaffolds were stable cell carriers and had the potential to generate volume-retaining tissue. However, no adipogenic differentiation was observed within the preadipocyte-seeded scaffolds.

Metabolic and histological analysis of mesenchymal stem cells grown in 3-D hyaluronan-based scaffolds.

Sheep mesenchymal stem cells (MSCs) were isolated and expanded using the principle of plastic adherence. Their identity as progenitor cells was confirmed by induction along the osteoblastic lineage using osteogenic supplements and observation of calcific deposits by von Kossa staining. MSCs were seeded onto two types of hyaluronan-based cylindrical scaffolds in high concentrations and cultured for varying time points up to three weeks. Culture medium was supplied using the following conditions: statically, on a shaker, by stirring with a magnetic stirrer or by perfusion in a tubular flow circuit. Total cell metabolism was assessed by MTT assay and the quality of cell coverage and matrix formation observed by SEM and histological analysis of thin sections of the constructs. Perfusion culture was established as the most appropriate culturing conditions, with cell metabolism increasing by approximately 300% over three weeks. The coverage of the scaffold surface was very good and the deposition of collagenous matrix was superior in these conditions compared to the, static and other dynamic culture conditions.

Heterogeneity in proliferative potential of ovine mesenchymal stem cell colonies.

Bone marrow biopsies were taken from the iliac crest of 28 individual sheep from three different breeds, ranging in age from 4 months to 8 years and mesenchymal stem cells (MSCs) isolated using selection due to plastic adherence. Cells were cultured in medium that had been selected for its effect on observed MSC proliferation, until populations of greater than 50 million had been obtained from each biopsy. The identity of the isolated cell populations as progenitors of the mesenchymal lineage was verified by deriving both osteoblastic and chondrocytic phenotypes when cultured in osteogenic and chondrogenic medium supplements, respectively. The rate of cell proliferation for each marrow biopsy was measured at each passage and the number of initial stem cells in each sample estimated. There was no statistically significant correlation between the age of the sheep and MSC proliferative potential, or age and estimated initial MSC number. There was no apparent significant difference between proliferation rate and sheep breed and colonies established from frozen cells grew at similar rates to pre-frozen cells. Counter intuitively, there appeared to be a negatively correlated trend between proliferation rate and MSC concentration in the samples. It is concluded that no initial descriptive statistics of the marrow biopsies can assist in estimating the proliferative potential, and therefore the timing of future surgeries, of MSCs sampled for the purposes of tissue engineering.

Stability of plasma-treated silicone rubber and its influence on the interfacial aspects of blood compatibility.

Medical-grade polydimethylsiloxane elastomer was subjected to low-powered plasma treatment in the presence of four different gases: O(2), Ar, N(2) and NH(3). Changes to the surface chemistry immediately after processing and the stability of the treatments following ageing in phosphate buffered saline or air for up to 1 month were investigated using X-ray photoelectron spectroscopy and dynamic contact angle analysis. Changes in surface morphology were assessed using optical microscopy and atomic force microscopy. All treatments resulted in an increase in wettability, attributed to major changes in chemistry combined with modest etching. Furthermore, the primary site of attack of the plasma species appeared to be dependent upon the feed gas implemented. The two main chemical changes observed after ageing were due to reactions with the storage media and relaxation processes resulting in further changes in wettability. The influence of the surface modifications on the blood compatibility of the materials was investigated by assessing contact phase activation using a partial thromboplastin time assay. It was demonstrated that the O(2) and Ar plasma treatments reduced the performance of the silicone but the N(2) and NH(3) treatments had a significantly beneficial effect on the activation of the coagulation cascade.

Surface properties and biocompatibility of solvent-cast poly[-caprolactone] films.

Poly(epsilon-caprolactone) (PCL) was dissolved in four solvent systems, chloroform, tetrahydrofuran, acetone and ethyl acetate, and cast onto glass Petri dishes. The surface properties of the resulting films were investigated. The extent to which their properties were determined by the solvent used in each case was quantified in terms of contact angle, surface morphology, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), and the adhesion and proliferation of fibroblasts by direct contact. The surface of the PCL film in contact with glass was denoted the SG surface, and the other, which was exposed to the gas phase, a mixture of air and residual solvent vapour, was denoted the SA surface. In the case of hydrophobic solvent systems, the advancing contact angle of the SG surface was always lower than that of the SA surface. With hydrophilic solvent systems, on the other hand, the advancing contact angle of the SG film surface was higher when the contact angle of the Petri dish was higher than that of the gaseous mixture of the air and solvent vapour, otherwise it was lower or equal to that of the surface on which it was cast. The surface morphology was dictated by the solubility of PCL in the respective solvent systems: high dissolution solvents such as chloroform and tetrahydrofuran produced films that comprised PCL aggregates, the particles being larger in the case of chloroform, whereas the less efficient solvents (acetone and ethyl acetate) resulted in a filamentous structure. The ATR-FTIR results confirmed that the chemistry of the SA surfaces differed according to the solvent system used. Preliminary cell culture experiments carried out with the PCL films established that murine (L929) fibroblasts grew well on all surfaces regardless of the solvent used, although the rates of adhesion and proliferation were not as great as on tissue culture plastic controls. Of all the surfaces examined in this study, the cells favoured the SG aspect of ethyl acetate cast PCL films, the surface of which had the finest pore size and relatively low contact angle.

Relationship between upregulated oestrogen receptors and expression of growth factors in cultured, human, prostatic stromal cells exposed to estradiol or dihydrotestosterone.

This study investigated the hypothesis that, in benign prostatic hyperplasia (BPH), upregulated oestrogen receptors (ER) and the action of androgens differentially regulate expression of stromal growth factors. Eight human prostatic stromal cell strains were subjected to a procedure to upregulate their ER by exposing them to 1 micromol 17beta-estradiol for 10 days followed by passage and growth in the absence of steroids. Four of the cell strains instead received 100 nmol dihydrotestosterone for 48 h. Immunoexpression of ERalpha, AR and six growth factors was quantified by flow cytometry in each case. Expression of ERalpha was significantly increased in six of eight cell strains. Expressions of six growth factors (FGF-2, FGF-7, IGF-1, TGF-beta1 NGF and e NOS) were elevated but only for FGF-7 was it significant. There was a significant positive correlation between the change in ERalpha and the change in FGF-2 and FGF-7, but not the other growth factors. Exposure to dihydrotestosterone reduced expression of ERalpha and all six growth factors, compared with oestrogen-treated cells but not significantly. It is concluded that upregulated ERalpha in prostatic stroma may have a greater modulating influence on synthesis of certain growth factors than the direct action of androgens and, by enhancing synthesis of FGF-2 and FGF-7, could play a significant role in the development of BPH.

Surface modification of a segmented polyetherurethane using a low-powered gas plasma and its influence on the activation of the coagulation system.

A medical grade segmented polyetherurethane (PEU) was treated with a low-powered gas plasma using O(2), Ar, N(2) and NH(3) as the treatment gases. Changes in the surface functional group chemistry were studied using X-ray photoelectron spectroscopy. The wettability of the surfaces was examined using dynamic contact angle measurements and the surface morphology was evaluated using atomic force microscopy. The influence of the surface modification to the polyurethane on the blood response to the polyetherurethane was investigated by measuring changes in the activation of the contact phase activation of the intrinsic coagulation cascade. The data demonstrate that the plasma treatment process caused surface modifications to the PEU that in all cases increased the polar nature of the surfaces. O(2) and Ar plasmas resulted in the incorporation of oxygen-containing groups that remained present following storage in an aqueous environment. N(2) and NH(3) plasmas resulted in the incorporation of nitrogen-containing groups but these were replaced with oxygen-containing groups following storage in the aqueous environment. In all plasma treatments there was a lowering of contact phase activation compared to the untreated surface, the N(2) and NH(3) treatments dramatically so.

Upregulation of estrogen and androgen receptors modulate expression of FGF-2 and FGF-7 in human, cultured, prostatic stromal cells exposed to high concentrations of estradiol.

This study was performed to develop an experimental model in which expression of estrogen receptors (ER) by human prostatic stromal cells could be reproducibly enhanced relative to similar cells with low ER expression. The second aim was to characterise changes in expression of ER, androgen receptor (AR), FGF-2 and FGF-7 in stromal cells exposed to high and low concentrations of estradiol and testosterone mimicking the different sex hormone levels between young and elderly men. Five strains of human prostatic stromal cells, isolated from BPH resections, were grown in steroid-free medium plus 1 micromol 17beta-estradiol. After 10 days, cells were passaged and grown in the same medium without estradiol until confluent. In a second study four cell strains were exposed to high and low concentrations of 17beta-estradiol and testosterone for 10 days. Cells were labelled with fluorescent antibodies to ERalpha, AR, FGF-2 and FGF-7 and the fluorescence intensity measured by flow cytometry. Following exposure to 1 micromol estradiol, stromal cells showed reduced expression of AR and ERalpha but after passage without estradiol they showed a 25% increase in both receptors over controls. Different combinations of sex hormones induced inconsistent changes with respect to expression of ER, AR and FGFs in the various cell-strains. However, there was a highly significant correlation between AR, ER and FGF-2 and FGF-7, which was cell strain-specific. Thus, changes in sex hormone balance per se may not be solely responsible for the observed increases in prostatic ER levels in BPH. Since expression of ER is correlated with synthesis of FGF-2 and FGF-7, it is likely that increases in stromal ER may mediate the synthesis of stromally-derived growth factors which contribute to the aetiopathogenesis of benign prostatic hyperplasia.

Influence of test protocol in determining the blood response to model polymers.

A multi-parametric, multi-center evaluation of three polymers was performed measuring their response to blood contact. The purpose of this study was to pinpoint differences in tests performed for assessing "basic" hemocompatibility on identical materials at different centers and attempt to rationalize. Assays for platelet adhesion, activation, aggregability and activation of the coagulation system in addition to an ex vivo patency assay were performed at four centers across Europe, using protocols favored by each center for determining the blood-contacting performance of a biomaterial. Three polymers were chosen for their expected blood response spanning the range of undesirable to desirable: ethylenevinylacetate (EVA), polyvinylchloride (PVC) and PVC modified with polyethylene oxide (PEO). The assays were ranked in terms of their efficacy compared to cost and simplicity. A correlation between assays was calculated, indicating the ability of one test to correctly determine the blood response compared to another. Some assays were unable to distinguish between materials, but of the assays which could, the materials were ranked in the following order: EVA; PVC; PVC-PEO, EVA producing the most undesirable response. It is concluded that many commonly used assays for determining hemocompatibility are inappropriate, but there are simple and reliable test methods available which correlate well with the more sophisticated protocols.

Modulating effect of estrogen and testosterone on prostatic stromal cell phenotype differentiation induced by noradrenaline and doxazosin.

BACKGROUND: Noradrenaline (NA) has been shown to enhance expression of the contractile phenotype of human prostatic stromal cells in tissue culture. This study examined the possibility that changing levels of sex hormones in elderly men with BPH may modulate the differentiating effect of NA and hence the efficacy of alpha(1)-adrenoceptor-blocking drugs. METHODS: Confluent, quiescent stromal cell cultures from 6 different patients were treated with combinations of 20 microM NA, 1 microM doxazosin, 0.1 microM beta-estradiol, and 0.1 microM testosterone, over a period of 10 days. Harvested cells were labelled with fluorescein-conjugated antisera to alpha-smooth muscle actin and myosin to identify cells of contractile phenotype which were thereafter analyzed flow-cytometrically. RESULTS: NA increased mean immunoexpression of both actin and myosin. Enhancement of myosin expression was highly significant (P

Influence of the alpha1-adrenergic antagonist, doxazosin, on noradrenaline-induced modulation of cytoskeletal proteins in cultured hyperplastic prostatic stromal cells.

BACKGROUND: Doxazosin, an alpha1-adrenergic antagonist, inhibits sympathetic contraction of prostatic stromal smooth muscle cells and is used in the relief of obstructive benign prostatic hyperplasia (BPH). In vitro application of noradrenaline stimulates expression of cytoskeletal filaments, particularly actin and myosin, by prostatic stromal cells, thus enhancing their differentiation towards smooth muscle cells. This study examined the possible role of doxazosin in reversing this phenotypic modulation as well as in inhibiting smooth muscle cell contraction. METHODS: Stromal cell tissue cultures derived from 10 human hyperplastic prostates were rendered quiescent by reduction of stripped fetal calf serum (FCS) to 1% (v/v) in the medium followed by treatment with 20 microM noradrenaline and/or 1 microM doxazosin for 10 days. Doxazosin, in 10-fold increments of concentration, was also added, separately, to two of these cell cultures, which were either quiescent or growing in 10% normal (unstripped) FCS. Harvested cells were labelled with fluorescein-labelled antisera to smooth muscle cytoskeletal filaments, and their individual fluorescence levels were analyzed flow-cytometrically. RESULTS: Noradrenaline increased expression of all cytoskeletal filaments studied. This effect was greatest for actin and myosin in proliferating cell cultures. Doxazosin largely reversed the increase in filament expression. This effect was most significant for actin and myosin and greatest in quiescent cultures. However, inhibition of the agonist effect of noradrenaline by doxazosin showed no clear dose-related response, in that expression of cytoskeletal filaments was differentially inhibited. CONCLUSIONS: The data suggest that doxazosin may inhibit not only stromal contraction of differentiated smooth muscle cells in BPH but also the phenotypic modulation of stromal smooth muscle cell differentiation induced by noradrenaline. These actions, together, may render prostatic stroma less contractile, and hence less able to respond to sympathetic stimulation, in patients with BPH. While effects on isolated stromal cells are of undoubted importance, failure to demonstrate a consistent dose-response relationship between expression of smooth muscle cell phenotype and inhibition by doxazosin suggests that additional influences, including humoral factors as well as the proximity of differentiated epithelium, are also likely to be involved in this interaction in the intact tissue.

Albumin-binding surfaces: in vitro activity.

Immobilized monoclonal antibodies (Mabs) have been used to attract specific molecules to a solid surface from complex mixtures such as blood, plasma or serum, thereby directing the response to the modified substrate, a key goal in rational biomaterial design. The nature of the Mab dictated the nature of the response: anti-albumin antibodies were used to prevent cell and platelet adhesion in vitro, whilst anti-fibronectin Mabs promoted attachment. Patterned surfaces could be formed, bearing Mabs that generated adhesive and non-adhesive regions. Fibrinogen adsorption from plasma showed a Vroman peak on unmodified control polymer, which was reduced by 64% in the presence of surface-bound anti-albumin Mab. Immobilization of a control Mab reduced fibrinogen adsorption only slightly, implying an albumin-mediated effect. In static tests, platelet adhesion from human platelet rich plasma was significantly reduced by the immobilization of anti-HSA Mab when compared to the untreated FEP surface (p < 0.0001). This effect was also seen with citrated blood flowing through Mab-treated polyurethane tubing at a shear rate of 132 s(-1) (p=0.034). Since platelets and proteins (as blood, plasma or serum) were introduced to the surface simultaneously, the generation of a defined protein film must have been sufficiently rapid as to shape the platelet or cell response.

Prostatic stromal cell phenotype is directly modulated by norepinephrine.

OBJECTIVES: To evaluate the response of prostatic stromal cells in vitro to the action of the agonist norepinephrine and to examine the role of cell density in this response. METHODS: Stromal cells isolated from transurethral chippings of patients with benign prostatic hyperplasia (BPH) were seeded onto tissue culture dishes either at high density (9 x 10(3) cells/cm2) or at low density (1.5 x 10(3) cells/cm2). Norepinephrine was added at concentrations in the range of 2.5 to 50 microM. Cells were harvested at the moment of confluence, labeled with monoclonal antibodies to four cytoskeletal proteins, and analyzed by flow cytometry. RESULTS: Sparsely plated stromal cells showed a consistent biphasic response in which a small fall in immunofluorescence occurred in the range of 5 to 15 microM norepinephrine but was thereafter followed by a progressive rise in fluorescence to 50 microM, indicating increased expression of smooth-muscle-associated cytoskeletal proteins. The shape of flow-cytometric frequency-distribution histograms for smooth-muscle myosin, desmin, and talin suggested that all mesenchymal cells in the stromal cultures were similarly modulated by norepinephrine. However, the effect on smooth-muscle actin was different in that a subpopulation of hyperreactive cells was identified. Densely plated stromal cells did not show a similar biphasic response to norepinephrine but instead demonstrated an overall downward trend, indicating a progressively diminished expression of these cytoskeletal proteins. CONCLUSIONS: Norepinephrine stimulation directly modulates BPH-derived prostatic stromal cells toward a differentiated smooth-muscle phenotype as evidenced by increased expression of cytoskeletal proteins. The effect of norepinephrine on cultures is cell-density-dependent, suggesting that intercellular communication is an important factor in coordinating the differentiation responses. This study has revealed a specific interaction between physical and humoral stimuli, which influences in part the phenotype of prostatic stromal cells. Such interaction is likely to determine the development of clinical BPH, and also the response of any individuals following therapeutic intervention using selective alpha-adrenergic blockade.

Sodium channel protein expression enhances the invasiveness of rat and human prostate cancer cells.

Expression of Na+ channel protein was analysed in established cell lines of rat and human prostatic carcinoma origin by flow cytometry using a fluorescein-labelled polyclonal antibody. In many cell lines examined, the obtained frequency distribution profiles were bimodal and identified a subpopulation of cells which expressed high levels of Na+ channel protein. A significant positive correlation was demonstrated between the proportion of channel-expressing cells and the functional ability of individual cell lines to invade a basement membrane matrix in vitro. In addition, two transfectant cell lines containing rat prostate cancer genomic DNA were found to express significantly elevated levels of Na+ channel protein when compared with the original benign recipient cell line. Enhanced Na+ channel expression by two metastatic derivatives of these transfectant cells directly correlated with increased invasiveness in vitro. These studies strongly support the hypothesis that expression of Na+ channel protein and the metastatic behaviour of prostatic carcinoma cells are functionally related, either by endowing the membranes of these cells with specialised electrophysiological properties (e.g. enhancing their motility and/or secretory activities) and/or by perturbing endogenous mechanisms regulating ionic homeostasis within the cells.

Haemocompatiblity of controlled release glass.

There are many medical applications which benefit from the use of soluble biomaterials, including the sustained release of drugs over a precise period of time, or temporary conduits for controlling nerve regrowth. We have manufactured a series of phosphate-based controlled release glasses (CRGs) in which the solubility could be controlled by varying the concentration of CaO and Na2O. Fibres of the CRG containing iron and cerium were placed into direct contact with human neutrophils and macrophages in tissue culture for 2.5 and 24 h respectively and the responses analysed by scanning electron microscopy (SEM) and confocal microscopy. The supernatants were analysed for the cytokine IL-1beta by enzyme-linked immunosorbent assay (ELISA). Disks of CRG of various compositions were placed in contact with whole blood for 30 min and platelet adhesion assessed by SEM. Activation of platelets, granulocytes and complement were quantified by ELISA for beta-thromboglobulin, elastase and iC3b. Intrinsic coagulation activation was measured by timing the clotting of recalcified plasma. Only the cerium fibre inhibited IL-1beta release from macrophages. No platelet adhesion was observed to any disk composition. Three compositions containing MgO inhibited plasma clotting and showed an insignificant level of complement activation. This study has demonstrated the development of a number of compositions of CRG, which have great potential in a wide variety of biomedical applications.

Platelet reactions to modified surfaces under dynamic conditions.

The influence of surfaces on the reactions of platelets in whole blood under laminar flow was investigated in a cone and plate viscometer. Citrated whole blood was exposed to steel, PMMA and PMMA modified with PEO at low (500 s(-1)) and high (4000 s(-1)) wall shear rates at room temperature for a period of 100 s. Treated blood samples were fixed with paraformaldehyde, stained with a monoclonal antibody for CD41 (platelet GPIIb/IIIa) conjugated with phycoerythrin and analyzed by flow cytometry. The reactions of platelets (microparticle generation and formation of platelet-platelet, platelet-red blood cell and red blood cell-microparticle aggregates) to these environments were quantified. Additionally, the size of platelet-platelet aggregates was assessed. The percentage platelet aggregation and numbers of microparticles generated were independent of surface type at any shear rate. The composition of the aggregates formed was influenced by the surface: at low and high shear rates PMMA caused the generation of platelet-platelet aggregates of the greatest size. The numbers of red blood cell-platelet and red blood cell-microparticle aggregates also varied depending on the surface. Fewer red blood cell-platelet aggregates were formed at higher shear rates, whereas the reverse was true for red blood cell-microparticle aggregates. It is concluded that these variations may help to explain the differential effects of surfaces to the induction of distant thrombotic events: microparticles may be protected from loss from the blood stream by their association with red blood cells at high shear rates.

The platelet antigens CD9, CD42 and integrin alpha IIb beta IIIa can be topographically associated and transduce functionally similar signals.

Investigation of the specific effects of different mAb known to stimulate platelets (agonist mAb) is complicated by interaction of the Fc portion of these mAb with the platelet Fc gamma RII. This has led to the conclusion that nearly all agonist-mAb-induced activation of platelets is mediated by this receptor. However, the target antigen-mediated signal can be analysed provided that the effects of Fc gamma RII engagement can either be reduced or eliminated. We have therefore blocked platelet Fc gamma RII with IV.3 Fab fragments (an anti-Fc gamma RII mAb), and stimulated the platelets by cross-linking intact agonist mAb with F(ab')2 fragments of an Fc-specific anti-mouse antibody. By analysing functional platelet responses and protein-tyrosine phosphorylation, we found that such non-Fc gamma RII-mediated cross-linking of CD9, CD42 and glycoprotein (gp) IIb/IIIa generates closely similar signals. Since this may indicate molecular associations, we analyzed the surface topography of platelets using the chemical cross-linking agent dithiobis(sulfosuccinimidyl propionate). We found that a proportion of CD9, gpIIb/IIIa and CD42 molecules associate with each other on the platelet surface membrane. Thus, our results suggest that these antigens are able to form a larger molecular complex and induce similar signals. Furthermore, cross-linking of CD9 and CD42 stimulated thrombasthenic platelets completely lacking gpIIb/IIIa. These data therefore indicate that CD9 and CD42 can signal independently of gpIIb/IIIa, and that signals generated by all these molecules may converge on a common pathway.

Macrophage subpopulation differentiation by stimulation with biomaterials.

Macrophages were elicited by the subcutaneous implantation of ultra high molecular weight polyethylene (UHMWPE) for periods of 2, 7, and 14 days in rats. Exudates of varying volumes were produced that was comprised of granulocytes, monocytes, immature and mature macrophages, and T-lymphocytes. No B-lymphocytes were observed at any time periods. Cell types were identified by their granularity and positivity to the following antibodies: leucocyte common antigen (LCA, pan leucocyte); CD11b/c (macrophage/monocyte); CD5 (T-lymphocyte); CD45RA (B-lymphocyte); HIS48 (granulocyte); ED2 (mature macrophage); and MCP-1 (monocyte chemoattractant protein 1). Monocytes isolated from control rat blood demonstrated a size slightly larger than that of granulocytes but with less granularity. Their size and granularity were followed over increasing time periods. The macrophages elicited by UHMWPE showed a similar pattern, with the exception of an apparently highly granular subpopulation with volumes similar to that of granulocytes but significantly more granular. The granular macrophage subset had a very high degree of ED2 and MCP-1 positivity, and their proportion, compared with other macrophages, was greatest at 2 days. The high MCP-1 expression was accounted for by MCP-1 molecules bound to the surface of a small proportion of macrophages that were activated. It is postulated that this subpopulation was responsible for the synthesis of the MCP-1 and could indicate a mechanism by which monocytes are attracted to the site of an implanted material.