Mesoporous silicon microparticles for oral drug delivery: Loading and release of five model drugs

Mesoporous silicon (PSi) microparticles were produced using thermal carbonization (TCPSi) or thermal oxidation (TOPSi) to obtain surfaces suitable for oral drug administration applications. The loading of five model drugs (antipyrine, ibuprofen, griseofulvin, ranitidine and furosemide) into the microparticles and their subsequent release behaviour were studied. Loading of drugs into TCPSi and TOPSi microparticles showed, that in addition to effects regarding the stability of the particles in the presence of aqueous or organic solvents, surface properties will affect compound affinity towards the particle. In addition to the surface properties, the chemical nature of the drug and the loading solution seems to be critical to the loading process. This was reflected in the obtained loading efficiencies, which varied between 9% and 45% with TCPSi particles. The release rate of a loaded drug from TCPSi microparticles was found to depend on the characteristic dissolution behaviour of the drug substance. When the dissolution rate of the free/unloaded drug was high, the microparticles caused a delayed release. However, with poorly dissolving drugs, the loading into the mesoporous microparticles clearly improved dissolution. In addition, pH dependency of the dissolution was reduced when the drug substance was loaded into the microparticles.

Griffonia simplicifolia lectins bind specifically to endothelial cells and some epithelial cells in mouse tissues

The binding of Griffonia simplicifolia agglutinin-I (GSA-I) and the isolectins GSA-I-AB3 and GSA-I-B4, having affinity for some alpha-D-galactosyl and N-acetyl galactosaminyl residues was studied in different mouse tissues. In brain, cardiac muscle and skeletal muscle, the GSA-I-lectin conjugates showed prominent binding only to blood vessel endothelia. Similarly, in the liver and kidney cortex the GSA-I-conjugates selectively reacted with endothelial cells of the sinusoids and with intertubular and glomerular capillaries, respectively. However, a strong reactivity with the GSA-I-conjugates was additionally seen in the acinar cells of the pancreas, in the stratified squamous epithelia of skin and tongue, and in transitional epithelium. SDS-PAGE electrophoresis combined with the lectin-blotting technique indicated that a similar set of glycoproteins are responsible for the GSA-I binding, even in different tissues. Another lectin with specificity for alpha-D-galactose, the Maclura pomifera agglutinin, displayed a distinctly different distribution of binding sites, mainly in the basement membranes, of all mouse tissues studied. The results suggest that some alpha-D-galactosyl residues, recognized by the binding of GSA-I lectins, are preferentially expressed in endothelial cells of mouse tissues, and also provide further evidence that endothelial cells can present a highly specific surface glycosylation pattern.

The alpha 1-alpha 6 subunits of integrins are characteristically expressed in distinct segments of developing and adult human nephron

We studied the distribution of the alpha 1-alpha 6 subunits of beta 1 integrins in developing and adult human kidney using a panel of mAbs in indirect immunofluorescence microscopy. Uninduced mesenchyme displayed a diffuse immunoreactivity for only the alpha 1 integrin subunit. At the S-shaped body stage of nephron development, several of the alpha subunits were characteristically expressed in distinct fetal nephron segments, and the pattern was retained also in the adult nephron. Thus, the alpha 1 subunit was characteristically expressed in mesangial and endothelial cells, the alpha 2 in glomerular endothelium and distal tubules, the alpha 3 in podocytes, Bowman's capsule, and distal tubules, and the alpha 6 subunit basally in all tubules, and only transiently in podocytes during development. Unlike the alpha 3 and alpha 6 subunits, the alpha 2 subunit displayed an overall cell surface distribution in distal tubules. It was also distinctly expressed in glomerular endothelia during glomerulogenesis. The beta 4 subunit was expressed only in fetal collecting ducts, and hence the alpha 6 subunit seems to be complexed with the beta 1 rather than beta 4 subunit in human kidney. Of the two fibronectin receptor alpha subunits, alpha 4 and alpha 5, only the latter was expressed, confined to endothelia of developing and adult blood vessels, suggesting that these receptor complexes play a minor role during nephrogenesis. The present results suggest that distinct integrins play a role during differentiation of specific nephron segments. They also indicate that alpha 3 beta 1 and alpha 6 beta 1 integrin complexes may function as basement membrane receptors in podocytes and tubular epithelial cells.

Differential expression of the ED sequence-containing form of cellular fibronectin in embryonic and adult human tissues

Monoclonal mouse hybridoma antibodies were obtained for secreted cellular fibronectin (cFn) from A8387 fibrosarcoma cells. One of them, 52-DH1 (DH), reacted exclusively with cFns but not with plasma Fns (pFns) in immunoblotting and solid-phase EIA. The DH antibody also recognized thermolysin cFn fragments and beta-galactosidase-Fn fusion protein which contained the ED sequence specific to at least some forms of cFns. On the other hand, the DH antibody failed to recognize a fusion protein that was otherwise identical but lacked the ED sequence. Thus, the antigenic determinant for the DH antibody was located to the ED sequence. The DH antibody was then used to study the expression of ED sequence containing cFn (EcFn). For comparisons, another monoclonal antibody, 52BF12 (BF), recognizing equally well both pFns and cFns, was used. Immunoblotting of pFn fragments indicated that this antibody had the antigenic determinant at or close to the cell-binding site of Fn. EcFn was revealed by the DH antibody in embryonic and adult fibroblasts and in a variety of other cultured normal and malignant human cells. In embryonic tissues EcFn was abundant in developing basement membranes, as shown in foetal kidney and muscle, while in adult tissues it was confined only to endothelia of larger blood vessels. Furthermore, in embryonic tissues the capillaries showed bright EcFn-positivity not found any more in adult tissues. Human plasma contained a small quantity of EcFn, which may hence have an endothelial origin. EcFn was also prominent in the stroma of malignant tumours as well as in reactive benign conditions, such as granulation tissue and decidual cells. The results suggest that EcFn is a form of the protein which may have a particular role in developing and reactive tissues in embryos and adults.

Changes in the glycosylation pattern during embryonic development of mouse kidney as revealed with lectin conjugates

Distribution of lectin-binding sites in adult and developing mouse kidney was studied with fluorochrome- and peroxidase-coupled lectins. Effects of fixation methods on lectin-binding patterns were also compared. Un-induced mesenchymal cells and ureter bud of the early metanephros reacted with Concanavalin A, Lens culinaris, Ricinus communis I, and wheat germ agglutinins, whereas binding sites for both soybean and peanut (PNA) agglutinins were seen only in ureter bud tissue. On induction, PNA positivity rapidly appeared in the induced, condensed areas of the metanephrogenic mesenchyme. Early glomeruli expressed heterogeneously terminal galactosyl and N-acetylgalactosaminyl moieties in the podocytes. Later, these sites disappeared and were apparently covered by sialic acids. Endothelia also displayed a comparable sialylation of terminal saccharide moieties during maturation. Binding sites for many of the above lectins were also found in the developing proximal and distal tubules. Terminal fucosyl residues, characteristic of mature proximal tubules, appeared during day 13 of development. Dolichos biflorus agglutinin reactivity, typically seen in the collecting ducts, appeared by day 13. Griffonia simplicifolia-I-B4 isolectin reactivity was exclusively localized to endothelial in adult kidney cortex, but in embryonic kidneys reactivity with collecting duct and podocytes was also seen. These results suggest that the compartmentalized expression of cell glycoconjugates in adult mouse kidney is acquired in a sequential manner during development. Such sequential appearance of the mature glycosylation pattern probably reflects functional maturation of the nephron.

Mesoporous silica material TUD-1 as a drug delivery system

For the first time the feasibility of siliceous mesoporous material TUD-1 (Technische Universiteit Delft) for drug delivery was studied. Model drug, ibuprofen, was adsorbed into TUD-1 mesopores via a soaking procedure. Characterizations with nitrogen adsorption, XRD, TG, HPLC and DSC demonstrated the successful inclusion of ibuprofen into TUD-1 host. The amount of ibuprofen adsorbed into the nanoreservoir of TUD-1 material was higher than reported for other mesoporous silica drug carriers (drug/carrier 49.5 wt.%). Drug release studies in vitro (HBSS buffer pH 5.5) demonstrated a fast and unrestricted liberation of ibuprofen, with 96% released at 210 min of the dissolution assay. The drug dissolution profile of TUD-1 material with the random, foam-like three-dimensional mesopore network and high accessibility to the dissolution medium was found to be much faster (kinetic constant k = 10.7) and more diffusion based (release constant n = 0.64) compared to a mesoporous MCM-41 material with smaller, unidirectional mesopore channels (k = 4.7, n = 0.71). Also, the mesoporous carriers were found to significantly increase the dissolution rate of ibuprofen, when compared to the pure crystalline form of the drug (k = 0.6, n = 0.96). TUD-1 was constituted as a potential drug delivery device with fast release property, with prospective applications in the formulation of poorly soluble drug compounds.

Evaluation of mesoporous TCPSi, MCM-41, SBA-15, and TUD-1 materials as API carriers for oral drug delivery

The feasibility of four mesoporous materials composed of biocompatible Si (TCPSi) or SiO(2) (MCM-41, SBA-15, and TUD-1) were evaluated for oral drug delivery applications. The main focus was to study the effect of the materials different pore systems (unidirectional/2D/3D) and their pore diameters, pore size distributions, pore volumes on the maximal drug load capacity, and release profiles of a loaded active pharmaceutical ingredient. Ibuprofen was used as the model drug. The total pore volume of the mesoporous solid was the main factor limiting the maximum drug load capacity, with SBA-15 reaching a very high drug load of 1:1 in weight due to its high pore volume. Dissolution experiments were performed in HBSS buffers of pH 5.5, 6.8, and 7.4 to mimic the conditions in the small intestine. At pH 5.5 the dissolution rate of ibuprofen released from the mesoporous carriers was significantly faster compared with the standard bulk ibuprofen (86-63% versus 25% released at 45 min), with the fastest release observed from the 3D pore network of TUD-1 carrier. The utilization of mesoporous carriers diminished the pH dependency of ibuprofen dissolution (pK(a) = 4.42), providing an interesting prospect for the formulation of poorly soluble drug compounds.

Permeability characteristics and membrane affinity of flavonoids and alkyl gallates in Caco-2 cells and in phospholipid vesicles

Biomembrane interactions of flavonoids and alkyl gallates were investigated using transport studies on Caco-2 cells and membrane affinity experiments in phospholipid vesicles. Flavone was rapidly absorbed across the cell monolayer (P(app),380 x 10(-6) cm/s), whereas efficient uptake but no apical to basolateral transport was observed with the flavonoids with higher degree of hydroxylation (e.g., quercetin and luteolin). The transport of alkyl gallates was governed by the length of the alkyl chain, i.e., methyl and propyl gallate were absorbed while octyl gallate showed cellular uptake but no transport. Flavonoids with several hydroxyl groups exhibited highest affinity for vesicle membranes, partition coefficients being 7.1 and 7.5 microM for luteolin and quercetin, respectively. In conclusion, the degree of hydroxylation, molecular configuration, and length of the side chain of flavonoids and alkyl gallates seem to have a highly important impact on their membrane affinity as well as on their permeability characteristics in Caco-2 cells.

Metabolism of amprenavir in liver microsomes: role of CYP3A4 inhibition for drug interactions

Amprenavir (141W94, VX-478, KVX-478) is metabolized primarily by CYP3A4 (cytochrome P450 3A4) in recombinant systems and human liver microsomes (HLM). The effects of ketoconazole, terfenadine, astemizole, rifampicin, methadone, and rifabutin upon amprenavir metabolism were examined in vitro using HLM. Ketoconazole, terfenadine, and astemizole were observed to inhibit amprenavir depletion, consistent with their known specificity for CYP3A4. The HIV protease inhibitors, indinavir, saquinavir, ritonavir, and nelfinavir, were included in incubations containing amprenavir to examine the interactions of HIV protease inhibitors in vitro. The order of amprenavir metabolism inhibition in human liver microsomes was observed to be: ritonavir > indinavir > nelfinavir > saquinavir. The Ki value for amprenavir-mediated inhibition of testosterone hydroxylation in human liver microsomes was found to be approximately 0.5 microM. Studies suggest that amprenavir inhibits CYP3A4 to a greater extent than saquinavir, and to a much lesser extent than ritonavir. Amprenavir, nelfinavir, and indinavir appear to inhibit CYP3A4 to a moderate extent, suggesting a selected number of coadministration restrictions.

Enhanced in vitro permeation of furosemide loaded into thermally carbonized mesoporous silicon (TCPSi) microparticles

The combined release and permeation behavior of furosemide loaded into thermally carbonized mesoporous silicon (TCPSi) microparticles was studied in order to evaluate the potential of TCPSi-loading to improve permeation of furosemide, a BCS class IV compound. Permeation was studied across Caco-2 monolayers at pH 5.5, 6.8 and 7.4 from drug solutions and TCPSi particles. TCPSi-loaded furosemide (39% w/w) exhibited improved dissolution from the microparticles with greatly diminished pH dependence. At pH 5.5, where furosemide solubility restricted the amount that could be dissolved in the control solution to less than 30% of the dose contained in the TCPSi particles, the flux of TCPSi-loaded furosemide across Caco-2 monolayers was over fivefold compared to pre-dissolved furosemide. The improved permeation could be confirmed also from dose-corrected (% dose-permeated) results. At pH 6.8 and pH 7.4, where corresponding doses could be used in control solutions, more than fourfold permeability values were obtained with TCPSi-loaded furosemide. Effects on transepithelial electrical resistance (TEER) and mannitol permeability were monitored and suggest that monolayer integrity was not compromised by the drug-loaded TCPSi microparticles. The improved permeation observed from furosemide-loaded TCPSi particles suggests that the high local concentrations provided by the enhanced dissolution properties of TCPSi-loaded furosemide could prove beneficial for absorption.

Preclinical evaluation of rapeseed, raspberry, and pine bark phenolics for health related effects

Rapeseed, raspberry, and pine bark are promising bioactive sources of plant phenolics selected from among ca. 100 previously screened plant materials for in vitro preclinical evaluation of health related effects. Phenolic extracts and isolated fractions of the selected materials were investigated for antioxidant, antimicrobial, antiinflammatory, and antimutagenic properties as well as for cell permeability. It was shown that rapeseed and pine bark phenolics and raspberry anthocyanins were good or excellent antioxidants toward oxidation of phosphatidylcholine membrane (liposomes), rapeseed oil (crude) phenolics were effective radical scavengers (DPPH test), and both raspberry and pine bark phenolics inhibited LDL oxidation. Rapeseed oil phenolics, principally vinylsyringol, raspberry anthocyanins, and pinoresinol and matairesinol, the principal components of pine bark phenolic isolate, were effective against formation of the proinflammatory mediator, prostaglandin E(2). Raspberry ellagitannins inhibited the growth of Proteus mirabilis and Klebsiella oxytoca. Pine bark and rapeseed had minor effects on the permeability of model drugs in Caco-2 experiments. None of the tested extracts were mutagenic nor toxic to Caco-2 cells or macrophages. Thus, phenolic isolates from rapeseed, raspberry, and pine bark and are safe and bioactive for possible food applications including functional foods intended for health benefit.

Development of LC/MS/MS Methods for Cocktail Dosed Caco-2 Samples Using Atmospheric Pressure Photoionization and Electrospray Ionization

Good reliability of Caco-2 permeability studies requires competent sampling and analytical methods to ensure the comparability of day-to-day experiments. In this work, two n-in-one LC/MS/MS methods based on two different ionization techniques were developed and validated for a group of reference compounds; eight of them are recommended by the Food and Drug Administration (FDA) for the evaluation of oral drug permeability. The performance of a new ionization technique, atmospheric pressure photoionization (APPI), as an interface for quantitative LC/MS analysis was evaluated in comparison to the electrospray ionization (ESI). Generally, the validation parameters, including sensitivity, accuracy, and repeatability, were comparable for the APPI and ESI methods. The main difference was that the linear quantitative range of APPI was 3-4 orders of magnitude (r(2) >/= 0.998) whereas in ESI it was typically 2-3 orders of magnitude (r(2) >/= 0.990). By the APPI and ESI methods, the simultaneous analysis of nine highly heterogeneous compounds was achieved within 5.5-7 min, which leads to significant savings in time and cost of the analyses. The successful validation data indicate the usefulness of both the methods for the rapid and sensitive (LOD values typically </=5 nM) testing of drug transport across the Caco-2 monolayers, and after case-specific modification, the methods enable the permeability screening of new drug candidates. The applicability and reliability of both methods was demonstrated with a real batch of Caco-2 samples, each providing similar values of apparent permeability (P(app)). In addition, the individual permeabilities of the compounds in the cocktail experiments correlated closely to the ones obtained from single-compound experiments.

Surface chemistry and pore size affect carrier properties of mesoporous silicon microparticles

Six different types of mesoporous silicon microparticles were prepared to evaluate the effect of surface treatment and pore sizes on their properties as drug carriers. The studied porous silicon particles were as-anodized, thermally carbonized (TCPSi) and thermally oxidized (TOPSi) in addition to three novel ones: annealed TCPSi, annealed TOPSi and thermally hydrocarbonized porous silicon (THCPSi). Drug dissolution at pH 5.5 and physical and chemical stabilities after 3 months of storage were used as experimental models to investigate the loaded particles. Loading degrees of ibuprofen in the particles were determined by several methods before and after storage, and the results were in good agreement with each other. Loading improved the dissolution rate of ibuprofen in all the studied cases, while the hydrophilic TCPSi material resulted in the fastest dissolution and the most stable mesoporous microparticles. The release profiles of ibuprofen did not change markedly during storage. The effect of storage on the loading degrees of the other PSi microparticles than the unstable (easily oxidized) as-anodized porous silicon was not notable.

Anchoring complex components laminin-5 and type VII collagen in intestine: association with migrating and differentiating enterocytes

Anchoring complex component laminin-5 and its subunits laminin (Ln)-alpha3 and Ln-beta3 chains, Type VII collagen, and integrin chains alpha3, alpha6, and beta4 were studied in developing and adult human intestine and compared with findings on Ln-alpha1 and Ln-alpha2 chains. In adult human duodenum, jejunum, and ileum, Ln-5 detected with a polyclonal antiserum and Ln-alpha3 and Ln-beta3 chains, detected with monoclonal antibodies (MAbs), were restricted to the epithelial basement membranes (BMs) of villi, whereas Ln-alpha2 chain was seen only focally in crypt bottoms. In double labeling experiments, the stretch of crypt BM corresponding to the proliferative cell compartment was found to be devoid of both Ln-alpha3 and Ln-alpha2 chains. Double labeling for Ln-5 and proliferating cell nuclear antigen also showed an abrupt onset of Ln-5 expression exactly at the upper edge of the proliferative cell compartment. Type VII collagen was negligible in duodenum and showed a rising duodenal-ileal gradient localizing to villar BMs. Double labeling for Ln-5 and Type VII collagen, however, indicated only partial co-distribution in the intestine. Electron microscopy of ileum revealed both anchoring filaments and anchoring fibrils but no hemidesmosomal plaques. Our results demonstrate the expression of Ln-5 in BMs outside of stratified epithelia and indicate that Ln-5 in the intestine is associated with the compartment of migrating and differentiating enterocytes. Absence of hemidesmosomes and the presence of other anchoring complex components, such as Ln-5, Type VII collagen, and integrin chains alpha3, alpha6, and beta4, suggests unique properties for epithelial cell attachment in the intestine.

Differential expression of laminin polypeptides in developing and adult human kidney

We studied the expression of laminin chains in embryonic and adult human kidney by indirect immunofluorescence with monoclonal antibodies (MAbs). In embryonic human kidney, immunoreactivity for laminin alpha 1, beta 1, and gamma 1 chains was found in basement membranes (BMs) of primary vesicles, in comma- and S-shaped bodies, and in more mature stages of glomeruli and in tubules. The beta 2 chain of laminin was absent in the early glomerular structures but was prominent in BMs of maturing glomeruli (GBMs) and Bowman's capsule (BCBMs) and was also detectable in some tubules. Both the beta 2 and alpha 2 chains were variably seen in medullary tubule BMs. In adult human kidney, laminin alpha 1 chain was seen in GBMs and all tubule BMs (TBMs) as well as in arterial smooth muscle BMs (SMBMs). Laminin beta 1 chain reactivity was found in all TBMs, but not in GBMs or SMBMs. In the glomerulus, a distinct mesangial type of reaction was revealed with the MAbs to beta 1 and alpha 2 chains. The GBMs and SMBMs reacted with MAbs to the beta 2 chain, but reactivity was lacking in BCBMs. Laminin gamma 1 chain immunoreactivity was weakly present in BCBMs, GBMs, and SMBMs. The alpha 3 and beta 3 chains could not be detected in developing or adult human nephron. The results show that during development the BMs in human nephron undergo distinct changes, laminin beta 1 chain being transiently co-expressed with alpha 1 chain during early glomerular development and then becoming replaced by the beta 2 chain, which, on the other hand, disappears from the BCBMs on maturation. The alpha 2 chain appears to emerge in the mesangium late during development.

Effects of detraining subsequent to strength training on neuromuscular function in patients with inflammatory arthritis

The effects of detraining subsequent to strength training on neuromuscular function were examined in 39 recent-onset rheumatoid arthritis (RA) patients. Eighteen age- and sex-matched healthy people (H) served as controls. Patients were randomly allocated either to the experimental group (PE), who carried out progressive strength training for 6 months, or to the control group (PC), who maintained only their habitual physical activities. After 6 months, PE returned to their earlier physical activities and strength training was terminated. At baseline, the maximal strength of the trunk extensors (not significant), grip strength and maximal dynamic strength and the shape of the force-time curve of the knee extensors were lower in PE and PC (P < 0.05-0.001) than in H. Strength training in PE led to remarkable increases (P < 0.05-0.001) in the maximal strength of all muscle groups without changes in the shape of the force-time curve. The increases in muscle strength in PE obtained by strength training were lost to a great degree during the detraining period for the isometric trunk extension (P < 0.01) and flexion (P < 0.01) strength and for the dynamic knee extension strength (P < 0.05), but not for the grip strength. In PC, trunk extension and flexion strength decreased significantly throughout the study period. At the post-test, all the strength values in both patient groups were much lower than in H. RA is a chronic disease which seems to need continuous physical exercise with sufficient intensity to minimize/prevent the loss of muscle strength and functional capacity.

Effect of cell differentiation and passage number on the expression of efflux proteins in wild type and vinblastine-induced Caco-2 cell lines

The mRNA level expression of MDR1, MRP1-6, BCRP and CYP3A4 was determined by quantitative PCR in wild type (Caco-2WT) and vinblastine-treated (Caco-2VBL) Caco-2 cells at different passage levels (32-53). Differentiation increased the mRNA levels of MDR1, BCRP and all the MRPs except MRP4. Corresponding mRNA levels were observed in Caco-2WT and Caco-2VBL, except that the expression of MRD1 was higher in Caco-2VBL than in Caco-2WT cells. CYP3A4 was barely detected in either cell line. MDR1 functionality was studied using rhodamine123 and verapamil as a substrate-inhibitor pair. Corresponding to the observed differences in mRNA levels, MDR1 activity was higher in the Caco-2VBL cells. In Caco-2WT, MDR1 functionality was elevated at low passage numbers (32-35) compared to higher ones (49-53). Verapamil inhibited MDR1 efflux except at higher passage Caco-2WT cells, where no MDR1 activity could be observed. The results support the use of Caco-2VBL cells in MDR1 screening. The functional expression is higher than in Caco-2WT and remains consistent across the studied passages without major differences in mRNA levels of other efflux proteins. As both the passage number and the level of cell differentiation affect the expression profile of efflux proteins, short-term cell growth protocols should be evaluated accordingly.

Longitudinal myelotomy in the treatment of spasticity of the legs

✓ Longitudinal myelotomy at the level of the conus medullaris relieved severe spasticity in eight of nine patients. There was some recurrence of spasticity attributed to inadequate myelotomy. Sensation was impaired by the myelotomy in some patients. Bladder function was temporarily worse in all patients, but in all but one was eventually equal to, or better than, that before surgery.

Integrins in human cells and tumors

We have studied the distribution of the alpha- and beta-subunits of integrins in developing and adult human kidney as well as in selected other tissues and cultured cells. In cultured cells some of the integrin subunits (beta 1, alpha 1, alpha 2 and alpha 5) colocalize with talin at focal adhesions when plated on an appropriate ligand. Similarly, in tissues the polarization of beta 1-integrins in colocalization with talin appears to indicate adhesive complexes, as demonstrated in adult glomeruli. In human kidney, the alpha subunits of integrins were seen to be segment-specifically expressed already in fetal tissues. In glomeruli the integrin alpha 1 subunit characterized mesangial cells while the alpha 2 and alpha 3 subunits showed immunoreactivity in endothelial cells and podocytes, respectively. In renal tubuli, the alpha 6 subunit, complexed with the beta 1 subunit, showed a typical polarized distribution coaligning with the tubular basement membrane while the alpha 3 and alpha 2 subunits were expressed in distal tubular cells. These results suggested that in kidney the alpha 2 beta 1, alpha 3 beta 1, and alpha 6 beta 1 integrins can function as basement membrane receptors. The alpha 5 subunit was nearly lacking in the kidney and it appears to be mainly expressed in some smooth muscle cells. In other tissues distinct patterns in the expression of integrins were found. Thus, in many glandular epithelial cells the alpha 3 beta 1 integrin appeared to function as a basement membrane receptor while in various stratified epithelia and in the breast such a polarized localization could be found for the alpha 6 beta 4 integrin. Finally, although presenting a clearly polarized distribution for beta 1 integrins, none of the alpha subunits could be found in cardiac or skeletal muscle cells and none of the integrins could be revealed in neuronal cells of human developing and adult cerebrum or cerebellum, although neurons in peripheral tissues contained abundantly the alpha 6 beta 1 integrin complex. In human tumors, the tumor cells, including also metastastatic tumors, generally presented the same integrins as their tissues of origin. In some poorly differentiated tumors both a population heterogeneity and even a lack of expression or a disorganization of basement membrane receptor integrins was obvious.

Expression of E- and N-cadherin in renal cell carcinomas, in renal cell carcinoma cell lines in vitro and in their xenografts

E- and N-cadherins are proteins involved in intercellular adhesion and are localized, e.g., in the adherens junctions of epithelial cells. Kidney tubules express these molecules in a distinctive pattern, the expression of N-cadherin being restricted to proximal tubules and that of E-cadherin to distal tubules and collecting ducts. Renal cell carcinomas (RCCs) and oncocytomas are considered to originate from these tubular epithelia. To find out whether cadherins could serve as markers for a cellular origin of these tumors, we studied the expression of E- and N-cadherins in RCCs and oncocytomas, in cell lines derived from RCCs as well as in tumors grown in nude mice. Most RCCs co-expressed E- and N-cadherins, as did 2 of the 4 cell lines studied. The expression pattern did not correlate with the histological grade of the tumors, and even the least differentiated tumors, as well as metastases, showed expression of cadherins. Renal oncocytomas expressed E-cadherin but not N-cadherin, which is in line with previous studies that have proposed a collecting duct origin for these tumors. Papillary renal neoplasms, a separate entity usually not classified as RCC, expressed neither of the cadherins studied despite the abundant expression of beta-catenin. Our results suggest that most RCCs co-express the characteristic adhesion molecules of both proximal and distal tubules, which makes it questionable whether the origin of these tumors can be reliably located to any distinct part of the renal tubule. Our results also suggest that in RCCs the increased histological grade is not directly associated with changes in the expression of either of the cadherins, indicating other mechanisms underlying the deficient capacity to form polarized tubular structures.