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Analysis of osteoblast activity at biomaterial-bone interfaces by in situ hybridization.

To investigate the effects of bioactive materials on bone formation in vivo, a new experimental model using in situ hybridization has been developed. A hole was drilled bilaterally in the distal epiphysis of rabbit femurs with subsequent implantations of beta-tricalcium phosphate (beta-TCP) cylinders in a press-fit manner. Specimens were collected at 3, 7, 14, and 28 days after operation. Femurs with empty drilling holes, and normal distal femurs without operation were used as controls. All specimens were decalcified and hybridized with a procollagen alpha 1(I) complementary RNA probe labeled with digoxygenin. In normal-bone sections, procollagen alpha 1(I) RNA was clearly demonstrated in periosteal osteoblasts, in osteoblasts in the mineralizing zone adjacent to growth plates, and in osteoblasts lining remodeling canals. As for beta-TCP, labeled osteoblasts around the material were not found at day 3, whereas they were most intensively observed at day 7 and a little less at day 14, in accordance with new-bone formation around the material. Weaker signals were also detected in fibroblasts at day 7. At day 28, osteoblasts lining the surface of newly formed bone were mainly negative, whereas those adjacent to the resorption sites of the beta-TCP showed positive signals, demonstrating an active remodeling at the material surface. The temporal expression of procollagen alpha 1(I) RNA in the beta-TCP specimens was fundamentally the same as that in the empty-hole specimens, suggesting no remarkable acceleration or suppression of bone-forming activity of osteoblasts by beta-TCP, which is consistent with osteoconductive bone formation. This in situ hybridization method was suggested to be a powerful tool in analyzing the biological effects of bioactive materials.

Animals↗

Osteoblast reaction at the interface between surface-active materials and bone in vivo: a study using in situ hybridization.

Osteoblast activation after implantation of two kinds of surface-active material in bone was investigated chronologically using in situ hybridization with digoxygenin-labeled procollagen alpha 1(I) complementary RNA probe. The bioactive materials used were hydroxyapatite (HA) and apatite- and wollastonite-containing glass-ceramic (A-W GC). A hole was drilled bilaterally in the distal epiphysis of rabbit femurs with subsequent implantation of HA or A-W GC cylinders in a press-fit manner. Specimens were collected at 3, 7, 14, and 28 days after operation and decalcified. Then the undecalcified implant cores were pushed out of the hole without causing damage to the bony side of the interface. In situ hybridization documented no qualitative differences in the expression of procollagen alpha 1(I) RNA between HA and A-W GC. Few osteoblasts at the bone-material interface showed a specific signal at day 3, whereas many osteoblasts were positive around the materials at days 7 and 14, indicative of active new bone formation. The positive osteoblasts seemed to originate from preexisting trabeculae and lined the trabeculae, newly formed bone, and material surface. At day 28, many osteoblasts lining material-surrounding bone were negative, whereas those in remodeling canals were positive, suggesting that the bone was in the remodeling stage after bone formation. These findings were comparable to those with beta-tricalcium phosphate in a previous study, thus suggesting osteoconductive bone formation on HA and A-W GC.

Animals↗

Expression of meltrin-alpha mRNA is not restricted to fusagenic cells.

Meltrin-alpha is a myoblast gene product reported to be required for cell fusion [Yagami-Hiromasa et al. (1995): Nature 377:652-656]. Because Northern blots revealed expression only in muscle and bone, the suggestion was made that meltrin-alpha is expressed exclusively by fusagenic cells in these tissues (myoblast and osteoclast). We studied expression of meltrin-alpha mRNA in a panel of tissues and cell lines using the polymerase chain reaction and found it widely expressed. Meltrin-alpha mRNA was readily detected in the osteoblast, the most abundant cell type in bone. In situ hybridization analysis on sections of neonatal mice revealed high levels of expression in the trabecular meshwork of long bones, the basal regions of the dermis and its underlying mesenchyme. We conclude that expression of meltrin-alpha mRNA is not restricted to fusagenic cells and that, in bone, the osteoblast is the major source.

ADAM Proteins↗

Coexpression of the mRNAs encoding retinol dehydrogenase isozymes and cellular retinol-binding protein.

We used in situ hybridization of adult rat tissue to show that mRNAs encoding cellular retinol-binding protein (CRBP) and retinol dehydrogenase (RoDH) isozymes I/III and II were expressed in hepatocytes uniformly throughout the liver lobule, but were absent from Kupffer cells and endothelial cells of blood vessels and bile ducts. In kidney, CRBP, RoDH(I), and RoDH(II) were found in the proximal tubules of the cortex. Distal tubules, Henle's loops, collecting ducts, and glomeruli showed little, if any, expression. In testis, CRBP, RoDH(I), and RoDH(II) were found in Sertoli cells. Expression, albeit weaker, also occurred in spermatogonia and primary spermatocytes. Peritubular cells and other germ cells had even weaker expression. Only CRBP and RoDH(II) mRNA were detected in interstitial cells. In lung CRBP, RoDH(I) and RoDH(II) were expressed most intensely in the epithelium of the bronchi and bronchioli, but also occurred in the simple columnar epithelial cells of the alveolar duct and in alveolar type II cells. These data are consistent with the hypothesis that holo-CRBP serves as substrate for retinoic acid biosynthesis because they show that the substrate and the enzyme occur in the same cellular loci in vivo. These data also indicate that multiple cellular sites of retinoic acid biosynthesis occur throughout tissues. Also, the general concordance between mRNA localization and CRBP expression patterns, revealed by previous immunocytochemistry studies, supports and extends the conclusion that CRBP mRNA expression correlates with CRBP expression, based earlier on comparing RNA assays with radioimmunoassays.

Alcohol Oxidoreductases↗

Dopamine D3 receptor antisense administration reduces basal c-fos and NGFI-B mRNA levels in the rat forebrain.

The physiological role of the dopamine D3 receptor is still unclear. The absence of selective pharmacological tools that can discriminate D3 over D2 receptor subtype activity is a major drawback in the elucidation of D3-mediated functions. In order to study D3 receptor actions in rat brain, we have developed an antisense strategy, using oligodeoxynucleotide (ODN) directed against the mRNA of the D3 receptor. Dopamine D2-like agents induce a cascade of events that affect numerous genes in the CNS. Transcription factors are among the most dramatically affected. Using the antisense strategy, we explored the involvement of the D3 receptor on the expression of two classes of transcription factors, the c-fos and NGFI-B. Intracerebroventricular injections of ODNs were made into the lateral ventricle (8 microg/hour, for 5 days). The effect of antisense administration on dopamine D1, D2, and D3 receptor binding was measured by means of receptor autoradiography, whereas transcription factor mRNA levels (c-fos and NGFI-B) were evaluated by in situ hybridization using specific complementary RNA probes. Dopamine D3 receptor levels were significantly decreased in the shell of nucleus accumbens of rats that received the D3 antisense ODN, whereas dopamine D1 and D2 receptor levels were not affected. Basal c-fos mRNA levels were concomitantly reduced in both cingulate and medial prefrontal cortices. Basal NGFI-B mRNA levels were also reduced in the cingulate cortex, shell of nucleus accumbens, and in the dorsomedial striatum, whereas the core of nucleus accumbens and the dorsolateral striatum were not affected after D3 antisense ODN treatments. Our results suggest that D3 receptors may tonically regulate transcription factor expression in rat forebrain. This supports the hypothesis of a constitutive activity of the D3 receptor in vivo.

Animals↗

Autoantibodies detected to expressed K+ channels are implicated in neuromyotonia.

Antibody-mediated autoimmunity underlies a diverse range of disorders, particularly in the nervous system where the extracellular domains of ion channels and receptors are especially vulnerable targets. We present here a novel means of detecting autoantibodies where the genes of the suspected target proteins are known, and use it to detect specific autoantibodies in acquired neuromyotonia (Isaacs' syndrome), a disorder characterized by hyperexcitable motor nerves and sometimes by central abnormalities. We expressed different human brain voltage-gated potassium channels in Xenopus oocytes by injecting the relevant alpha-subunit complementary RNA, and detected antibody binding by immunohistochemistry on frozen sections. Antibodies were detected to one or more human brain voltage-gated potassium channel in 12 of 12 neuromyotonia patients and none of 18 control subjects. The results establish neuromyotonia as a new antibody-mediated channelopathy and indicate the investigative potential of this molecular immunohistochemical assay.

Autoantibodies↗

Silencing of retroviral vector transduced LacZ reporter gene by frameshift mutation.

Moloney murine leukemia virus-based vector expressing Escherichia coli beta-galactosidase (lacZ) as reporter gene and the transposon Tn5 neomycin resistance (neo) gene was transduced at low-multiplicity of infections into NIH 3T3 cells. Geneticin (G418)-resistant cells were recloned and cell lines containing beta-galactosidase positive or beta-galactosidase negative cells were obtained. Both positive and negative cell lines contained a single proviral copy at distinct integration sites. RNA complementary to lacZ was detected in beta-galactosidase positive as well as in one of three investigated beta-galactosidase negative cell lines. DNA sequence analysis of proviral LacZ gene in beta-galactosidase negative cell line C6 showed a single nucleotide insertion at position 1567 resulting in reading frame shift and translational stop codon at position 1629. This mutation explains the enzyme inactivation. The absence of beta-galactosidase after retroviral transduction of LacZ reproter gene may be a consequence of definite mutation but not a consequence of ineffective transduction or transcriptional inactivation of transgene.

3T3 Cells↗

Activation of prostanoid EP(3) and EP(4) receptor mRNA-expressing neurons in the rat parabrachial nucleus by intravenous injection of bacterial wall lipopolysaccharide.

Systemic inflammation activates central autonomic circuits, such as neurons in the pontine parabrachial nucleus. This activation may be the result of afferent signaling through the vagus nerve, but it may also depend on central prostaglandin-mediated mechanisms. Recently, we have shown that neurons in the parts of the parabrachial nucleus that are activated by immune challenge express prostaglandin receptors of the EP(3) and EP(4) subtypes, but it remains to be determined if the prostaglandin receptor-expressing neurons are identical to those that respond to immune stimuli. In the present study, bacterial wall lipopolysaccharide was injected intravenously in adult male rats and the expression of c-fos mRNA and of EP(3) and EP(4) receptor mRNA was examined with complementary RNA probes labeled with digoxigenin and radioisotopes, respectively. Large numbers of neurons in the external lateral parabrachial subnucleus, a major target of vagal-solitary tract efferents, expressed c-fos mRNA. Quantitative analysis showed that about 60% (range 40%-79%) of these neurons also expressed EP(3) receptor mRNA. Conversely, slightly more than 50% (range 48%-63%) of the EP(3) receptor-expressing neurons in the same subnucleus coexpressed c-fos mRNA. In contrast, few EP(4) receptor-expressing neurons were c-fos positive, with the exception of a small population located in the superior lateral and dorsal lateral subnuclei. These findings show that immune challenge activates central autonomic neurons that could be the target of centrally produced prostaglandin E(2), suggesting that synaptic signaling and paracrine mechanisms may interact on these neurons.

Acute-Phase Reaction↗

Neuropeptide Y Y1 receptor mRNA in rodent brain: distribution and colocalization with melanocortin-4 receptor.

The central neuropeptide Y (NPY) Y1 receptor (Y1-R) system has been implicated in feeding, endocrine, and autonomic regulation. In the present study, we systematically examined the brain distribution of Y1-R mRNA in rodents by using radioisotopic in situ hybridization histochemistry (ISHH) with a novel sensitive cRNA probe. Within the rat hypothalamus, Y1-R-specific hybridization was observed in the anteroventral periventricular, ventromedial preoptic, suprachiasmatic, paraventricular (PVH), dorsomedial, ventromedial, arcuate, and mamillary nuclei. In the rat, Y1-R mRNA expression was also seen in the subfornical organ, anterior hypothalamic area, dorsal hypothalamic area, and in the lateral hypothalamic area. In addition, Y1-R hybridization was evident in several extrahypothalamic forebrain and hindbrain sites involved in feeding and/or autonomic regulation in the rat. A similar distribution pattern of Y1-R mRNA was observed in the mouse brain. Moreover, by using a transgenic mouse line expressing green fluorescent protein under the control of the melanocortin-4 receptor (MC4-R) promoter, we observed Y1-R mRNA expression in MC4-R-positive cells in several brain sites such as the PVH and central nucleus of the amygdala. Additionally, dual-label ISHH demonstrated that hypophysiotropic PVH cells coexpress Y1-R and pro-thyrotropin-releasing hormone mRNAs in the rat. These observations are consistent with the proposed roles of the central NPY/Y1-R system in energy homeostasis.

Animals↗

BOC, brother of CDO, is a dorsoventral axon-guidance molecule in the embryonic vertebrate brain.

The early axon scaffolding in the embryonic vertebrate brain consists of a series of ventrally projecting axon tracts that grow into a single major longitudinal pathway connected across the midline by commissures. We have investigated the role of Brother of CDO (BOC), an immunoglobulin (Ig) superfamily member distantly related to the Roundabout (Robo) family of axon-guidance receptors, in the development of this embryonic template of axon tracts in the zebrafish brain. A zebrafish homologue of BOC was isolated and shown to be expressed predominantly in the developing neural plate and later in the neural tube and developing brain. Zebrafish boc was initially highly localized to discrete bands in the mid- and hindbrain, but, as the major brain subdivisions emerged, it became more evenly expressed along the rostrocaudal axis, particularly in dorsal regions. The function of zebrafish boc was examined by a loss-of-function approach. Analysis of embryos injected with antisense morpholinos designed against boc revealed highly selective defects in the development of dorsoventrally projecting axon tracts. Loss of boc caused ventrally projecting axons, particularly those arising from the presumptive telencephalon, to follow aberrant trajectories. These data indicate that boc is an axon-guidance molecule playing a fundamental role in pathfinding during the early patterning of the axon scaffold in the embryonic vertebrate brain.

Animals↗

Differential expression of GABAA/benzodiazepine receptor beta 1, beta 2, and beta 3 subunit mRNAs in the developing mouse cerebellum.

Gamma aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian cerebellum. Cerebellar granule, Purkinje, and deep nuclear neurons are known to receive GABAergic afferents. Since GABA exerts its inhibitory effects via GABA receptors, it is of interest to determine the temporal relationship between the formation of GABAergic synapses and the expression of genes coding for the GABA receptor. In a previous study, we have examined the developmental expression of binding sites for [3H]muscimol, which binds with high affinity to the beta subunits of the GABAA/benzodiazepine (GABAA/BZ) receptor. In the present study, [35S]cRNA probes were used to examine the appearance and distribution of GABAA/BZ beta 1, beta 2, and beta 3 subunit mRNAs in the developing C57BL/6 mouse cerebellum by in situ hybridization. In the adult cerebellum, the distribution of the three subunit mRNAs was clearly different, despite considerable overlap, and their temporal expression differed throughout postnatal development. The beta 1 hybridization signal appeared within the cerebellar cortex during the second postnatal week as a discrete band at the interface of the molecular and granule cell layers. Grains were distributed diffusely over small densely staining cells surrounding the Purkinje cells; relatively few grains were visible over Purkinje cell bodies themselves. This distribution may reflect an association with Bergmann glia or basket cells. The beta 2 and beta 3 hybridization signals were present considerably earlier than that of the beta 1 mRNA. The beta 2 signal was present at birth in the molecular/Purkinje cell layer; as development progressed, the signal became increasingly intense over both granule and Purkinje cells. At birth, the beta 3 subunit mRNA was present in the external germinal and molecular layers, later becoming largely localized within the granule cell layer. Dense beta 2 and beta 3 cRNA probe labeling was present over the adult granule cell layer. Moderate levels of beta 2 signal were seen over Purkinje cell bodies; considerably less labeling was observed with the beta 3 probe. The adult distribution of beta 2 and beta 3 cRNA probes showed good spatial correspondence with the known GABAA receptor beta subunit markers, [3H]-muscimol and the mAb 62-3G1 antibody, each being present within the granule cell layer. Our results indicate that the temporal expression of GABAA/BZ receptor beta subunit messages within a given cell type may be independently regulated, and that acquisition of the beta 2 and beta 3 mRNAs occurs before these cells become integrated into mature synaptic circuits.

Animals↗

D1 and D2 dopamine receptor gene expression in the rat striatum: sensitive cRNA probes demonstrate prominent segregation of D1 and D2 mRNAs in distinct neuronal populations of the dorsal and ventral striatum.

The postsynaptic effects of dopamine in the striatum are mediated mainly by receptors encoded by D1, D2, and D3 dopamine receptor genes. The D1 and D2 genes are the most widely expressed in the caudate-putamen, the accumbens nucleus, and the olfactory tubercle. Several anatomical studies, including studies using in situ hybridization with oligonucleotide and cDNA probes, have suggested that D1 and D2 receptors are segregated into distinct efferent neuronal populations of the striatum: D1 in substance P striatonigral neurons and D2 in enkephalin striatopallidal neurons. In contrast, on the basis of several in vivo and in vitro studies, other authors have suggested the existence of an extensive colocalization of D1 and D2 in the same striatal neurons. Our study was undertaken in order to analyze in detail the expression of the D1 and D2 receptor genes in the efferent striatal populations, with special reference to the various striatal areas, and to yield insights into the question about D1 and D2 mRNA localization in the striatum. We have, therefore, used highly sensitive digoxigenin- and 35S-labeled cRNA probes to address this question. The present results demonstrate that the D1 and D2 receptor mRNAs are segregated, respectively, in substance P and enkephalin neurons in the caudate-putamen and accumbens nucleus (shell and core) and in the olfactory tubercle (for their largest part). A very small percentage of neurons may coexpress both genes. These results confirm that the D1 and D2 receptor genes are expressed in distinct populations of striatal efferent neurons in the normal adult rat.

Animals↗

Developmental changes in the expression of gamma-aminobutyric acidA/benzodiazepine receptor subunit mRNAs in the murine inferior olivary complex.

The pharmacological and physiological properties of ligand-gated ion channels are dependent on their subunit composition; spontaneously occurring changes in subunit composition during neuronal development may result in dramatic functional differences between embryonic and adult forms of the receptor complex. In the present study, in situ hybridization with antisense cRNA probes was used to examine the subunit composition of the gamma-aminobutyric acidA/benzodiazepine (GABAA/BZ) receptor in the developing inferior olivary complex. This receptor is thought to be a pentameric chloride channel comprised of selected alpha, beta, gamma, delta, and rho subunits, the majority of which have several isoforms: alpha 1-6, beta 1-4, gamma 1-4, and rho 1,2. Among the 13 subunit variants present in the mammalian central nervous system, alpha 2-5, beta 3, and gamma 1,2 mRNAs are expressed at significant levels in the inferior olivary complex. Two clearly different temporal patterns of GABAA/BZ receptor subunit mRNA expression were observed: The expression of alpha 3, alpha 5, beta 3, and gamma 2 mRNAs was at a peak during embryonic and early postnatal development followed by rapid down-regulation thereafter. Conversely, alpha 2, alpha 4, and gamma 1 mRNA expression was very low or absent during early development, and a pronounced increase was observed at the end of postnatal week 1. These studies suggest that there are developmental changes in the subunit composition of the GABAA/BZ receptor in inferior olivary neurons. These changes in subunit expression, which occur during a period of major alterations in afferent and efferent synaptic connections, may subserve a change in the role of GABA from its function as a neurotrophic factor to that of an inhibitory neurotransmitter.

Animals↗

Laminar patterns of expression of GABA-A receptor subunit mRNAs in monkey sensory motor cortex.

Radioactive complementary RNA probes, made from monkey-specific cDNAs specific for the alpha 1, alpha 2, alpha 4, alpha 5, beta 1, beta 2, and gamma 2 subunits of the gamma-aminobutyric acid A (GABAA) receptor were used for in situ hybridization histochemistry of the primary motor, somatosensory, and anterior parietal areas of the cerebral cortex in macaque monkeys. mRNAs for the alpha 1, beta 2, and gamma 2 subunit polypeptides, which form receptors with the full range of classical properties, are expressed at much higher levels in all areas and show laminar- and sublaminar-specific concentrations. alpha 2, alpha 4, alpha 5, and beta 1 subunit transcripts are expressed at much lower levels but also display individual, laminar-specific concentrations; alpha 5 expression, in particular, is highly expressed in layer IV in the somatosensory and parietal areas and in a layer IV-like band in the motor cortex. In layers in which expression of a particular transcript is high, all neurons may express the gene, but in layers in which expression is moderate, it is possible to detect differences in the degree of labeling of individual neurons for a particular mRNA, and some neurons may not express certain subunit transcripts in detectable amounts. These findings indicate the variability in expression of different GABAA receptor subunits in the cerebral cortex. Laminar differences may indicate the assembly of functional receptors from different arrangements of available subunits in different classes of cells.

Animals↗

Slow and fast fiber isoform gene expression is systematically altered in skeletal muscle of the Sox6 mutant, p100H.

We have previously demonstrated that p100H mutant mice, which lack a functional Sox6 gene, exhibit skeletal and cardiac muscle degeneration and develop cardiac conduction abnormalities soon after birth. To understand the role of Sox6 in skeletal muscle development, we identified muscle-specific genes differentially expressed between wild-type and p100H mutant skeletal muscles and investigated their temporal expression in the mutant muscle. We found that, in the mutant skeletal muscle, slow fiber and cardiac isoform genes are expressed at significantly higher levels, whereas fast fiber isoform genes are expressed at significantly lower levels than wild-type. Onset of this aberrant fiber type-specific gene expression in the mutant coincides with the beginning of the secondary myotube formation, at embryonic day 15-16 in mice. Together with our earlier report, demonstrating early postnatal muscle defects in the Sox6 null-p100H mutant, the present results suggest that Sox6 likely plays an important role in muscle development.

Animals↗

Enhanced hepatic collagen type I mRNA expression into fat-storing cells in a rodent model of hemochromatosis.

In recent years, identifying the hepatic cell type responsible for collagen synthesis in experimental models of postnecrotic or inflammatory fibrosis has been the subject of active investigation. In primary iron overload states, however, hepatic fibrosis and cirrhosis occur without accompanying necroinflammatory phenomena. In this study, we combined morphological, immunological, cell isolation and purification and molecular biological techniques to identify the hepatic cell responsible for enhanced collagen type I gene expression during chronic enteral iron overload in the rat. Ultrastructural analysis of liver tissue sections from iron-loaded rats specifically revealed an altered appearance of fat-storing cells, which showed few if any fat droplets left and increased rough endoplasmic reticulum. In situ hybridization analysis with specific complementary RNA probes identified enhanced signal for collagen type I into nonparenchymal cells in zones 1 and 2, without signal over the background onto iron-laden hepatocytes. Immunocytochemistry with desmin antibodies combined with in situ hybridization on the same tissue sections identified the cells expressing high level of collagen type I transcripts as fat-storing cells. Northern-blot analysis on RNA extracted from various purified cell isolates, confirmed the presence of collagen type I mRNA signal only into the fat-storing cells isolate. Our study shows that in an experimental model of metabolic fibrosis in which the hepatotoxin selectively accumulates into parenchymal cells, fat-storing cells are the main source of enhanced collagen type I gene expression.

Animals↗

High tumor tissue concentration of urokinase plasminogen activator receptor is associated with good prognosis in patients with ovarian cancer.

The urokinase plasminogen activator (uPA) system is involved in tumor growth and metastasis. We assayed the components of the uPA system in homogenates of 64 primary epithelial ovarian tumors and 5 metastases and evaluated the association of these parameters to prognosis in the 51 malignant cases. The levels of uPA, PAI-2 and the uPA:PAI-1 complex increased with progressive loss of histological differentiation (p(trend) <0.001, <0.05 and <0.001). The level of PAI-1 was higher in poorly than in well/moderately differentiated tumors (p = 0.03). The content of uPAR was lower in benign tumors as compared to borderline malignancies (p = 0.002), invasive primary tumors (p < 0.001), and metastases (p = 0.002). Surprisingly, the level of uPAR was lower in poorly differentiated as compared to both borderline (p = 0.01) and well differentiated malignant tumors (p = 0.005). Also, the level of uPAR was lower in advanced as compared to early stages of the disease (p(trend) = 0.002). The median follow-up time for patients was 5.8 years. High tumor tissue levels of uPAR were associated with longer postoperative survival (HR = 0.4, 95% CI = 0.2-0.8, p = 0.01). In contrast, shorter survival was evident in patients with high tumor levels of uPA from 2 years on after operation (HR = 4.6, 95% CI = 1.2-17, p = 0.02). High tPA levels tended to be associated with shorter overall survival after 2 years (HR = 2.9, 95% 95% CI = 0.9-9.8, p = 0.08). Although high tumor tissue content of uPAR was associated with a less aggressive phenotype characterized by well differentiated histology and longer survival, low content of uPAR in the poorly differentiated tumors and metastases presumably results from increased elimination of uPAR.

Adenocarcinoma, Clear Cell↗

Dedifferentiation of serous ovarian cancer from cystic to solid tumors is associated with increased expression of mRNA for urokinase plasminogen activator (uPA), its receptor (uPAR) and its inhibitor (PAI-1).

The plasminogen activating system is involved in tumor growth and metastasis by degradation of extracellular matrix, and modulation of cell adhesion and migration. Benign and well-differentiated malignant ovarian tumors present as cystic lesions with preserved glandular morphology, whereas poorly differentiated tumors and metastases are solid with characteristic absence of glandular morphology. We analyzed the mRNAs for urokinase plasminogen activator (uPA), its receptor (uPAR), and inhibitor (PAI-1) in serous ovarian tumors by in situ hybridization and by densitometric scanning of Northern blots prepared from tissue extracts. The mRNA expressing cells in the in situ hybridization sections were evaluated and counted by two different observers. The number of mRNA expressing cells for uPA, uPAR and PAI-1 were all significantly increased in solid as compared with cystic malignant tumors. The increased expression of all three mRNA species was mainly located in the stroma of poorly differentiated tumors and metastases. Apart from being expressed in the stroma of these tumors, uPAR mRNA was also expressed by tumor cells located along the stromal/epithelial boarder. In addition, the tumor tissue content of uPA, uPAR and PAI-1 mRNAs as measured by Northern blots were higher in the solid as compared with the cystic tumors. Increased expression of uPA, uPAR and PAI-1 genes in the solid tumors suggest a correlation with a more aggressive phenotype.

Blotting, Northern↗