Laminin and beta1 integrin distribution in the early stages of human kidney development

Sortilin is a putative postendocytic receptor of thyroglobulin

The Vps10p family member sortilin is involved in various cell processes, including protein trafficking. Here we found that sortilin is expressed in thyroid epithelial cells (thyrocytes) in a TSH-dependent manner, that the hormone precursor thyroglobulin (Tg) is a high-affinity sortilin ligand, and that binding to sortilin occurs after Tg endocytosis, resulting in Tg recycling. Sortilin was found to be expressed intracellularly in thyrocytes, as observed in mouse, human, and rat thyroid as well as in FRTL-5 cells. Sortilin expression was demonstrated to be TSH dependent, both in FRTL-5 cells and in mice treated with methimazole and perchlorate. Plasmon resonance binding assays showed that Tg binds to sortilin in a concentration-dependent manner and with high affinity, with Kd values that paralleled the hormone content of Tg. In addition, we found that Tg and sortilin interact in vivo and in cultured cells, as observed by immunoprecipitation, in mouse thyroid extracts and in COS-7 cells transiently cotransfected with sortilin and Tg. After incubation of FRTL-5 cells with exogenous, labeled Tg, sortilin and Tg interacted intracellularly, presumably within the endocytic pathway, as observed by immunofluorescence and immunoelectron microscopy, the latter technique showing some degree of Tg recycling. This was confirmed in FRTL-5 cells in which Tg recycling was reduced by silencing of the sortilin gene and in CHO cells transfected with sortilin in which recycling was increased. Our findings provide a novel pathway of Tg trafficking and a novel function of sortilin in the thyroid gland, the functional impact of which remains to be established.

Interaction of human gingival fibroblasts with PVA/gelatine sponges

Tissue engineering scaffolds should be able to reproduce optimal microenvironments in order to support cell attachment, three-dimensional growth, migration and, regarding fibroblasts, must also promote extracellular matrix production. Various bioactive molecules are employed in the preparation of spongy scaffolds to obtain biomimetic matrices by either surface-coating or introducing them into the bulk composition of the biomaterial. The biomimetic properties of a spongy matrix composed of PVA combined with the natural component gelatine were evaluated by culturing human gingival fibroblasts on the scaffold. Cell adhesion, morphology and distribution within the scaffold were assessed by histology and electron microscopy; viability and metabolic activity as well as extracellular matrix production were analyzed by MTT assay, cytochemistry and immunocytochemistry. Fibroblasts interacted positively with PVA/gelatine. They adhered to the PVA/gelatine matrix in which they had good spreading activity and active metabolism; fibroblasts were also able to produce extracellular matrix molecules (type I collagen, fibronectin and laminin) compared to bi-dimensionally grown cells. The in situ creation of a biological matrix by human fibroblasts together with the ability to produce growth factor TGF-beta1 and the intracellular signal transduction molecule RhoA, suggests that this kind of PVA/gelatine sponge may represent a suitable support for in vitro extracellular matrix production and connective tissue regeneration.

Gelatine/PLLA sponge-like scaffolds: morphological and biological characterization

Biodegradable synthetic polymers such as poly(lactic acid) (PLA) are widely used to prepare scaffolds for cell transplantation and tissue growth, using different techniques set up for the purpose. However the poor hydrophilicity of these polymers represents the main limitation to their use as scaffolds because it causes a low affinity for the cells. An effective way to solve this problem could be represented by the addition of biopolymers that are in general highly hydrophilic. The present work concerns porous biodegradable sponge-like systems based on poly(L-lactic acid) (PLLA) and gelatine. Morphology and porosity characteristics of the sponges were studied by scanning electron microscopy and mercury intrusion porosimetry respectively. Blood compatibility was investigated by bovine plasma fibrinogen (BPF) adsorption test and platelet adhesion test (PAT). The cell culture method was used in order to evaluate the ability of the matrices to work as scaffolds for tissue regeneration. The obtained results indicate that the sponges have interesting porous characteristics, good blood compatibility and above all good ability to support cell adhesion and growth. In fact viable and metabolically active animal cells were found inside the sponges after 8 weeks in culture. On this basis the systems produced seem to be good candidates as scaffolds for tissue regeneration.

Gelatine/PLLA sponge-like scaffolds: morphological and biological characterization

Biodegradable synthetic polymers such as poly(lactic acid) are widely used to prepare scaffolds for cell transplantation and tissue growth, using different techniques set up for the purpose. However the poor hydrophilicity of these polymers represents the main limitation to their use as scaffolds because it causes a low affinity for the cells. An effective way to solve this problem could be represented by the addition of biopolymers that are in general highly hydrophilic. The present work concerns porous biodegradable sponge-like systems based on poly(L-lactic acid) and gelatine. Morphology and porosity characteristics of the sponges were studied by scanning electron microscopy and mercury intrusion porosimetry respectively. Blood compatibility was investigated by bovine plasma fibrinogen adsorption test and platelet adhesion test. The cell culture method was used in order to evaluate the ability of the matrices to work as scaffolds for tissue regeneration. The obtained results indicate that the sponges have interesting porous characteristics, good blood compatibility and above all good ability to support cell adhesion and growth. In fact viable and metabolically active animal cells were found inside the sponges after 8 weeks in culture. On this basis the systems produced seem to be good candidates as scaffolds for tissue regeneration.

TSH-Dependent expression of the LDL receptor-associated protein (RAP) in thyroid epithelial cells

The low density lipoprotein (LDL) receptor-associated protein (RAP) is an endoplasmic reticulum (ER)-resident molecular chaperone for several LDL receptor family members and it also binds to thyroglobulin (Tg), the thyroid hormone precursor. Disruption of the RAP gene in thyrocytes results in impaired Tg secretion. To gain further insights into the function of RAP in the thyroid, we investigated whether its expression in thyrocytes is regulated by thyroid-stimulating hormone (TSH), a feature common to all proteins involved in thyroid hormone secretion. We found by immunofluorescence that in FRTL-5 cells cultured in the presence of TSH, RAP is expressed intracellularly. The levels of expression increased after exposure to TSH, beginning at 48 hours, in a concentration-dependent manner as observed by immunofluorescence and Western blotting. Expression of RAP was also increased by TSH in primary cultures of human thyrocytes as observed by Western blotting. In hypothyroid mice with high serum TSH, RAP was markedly increased compared with euthyroid mice as observed by immunohistochemistry and Western blotting. Based on these findings, we concluded that RAP is expressed by thyrocytes in a TSH-dependent manner, both in cultured thyroid cells and in vivo.

Role of cyclooxygenase isoforms and nitric-oxide synthase in the modulation of tracheal motor responsiveness in normal and antigen-sensitized Guinea pigs

The effects of selective cyclooxygenase (COX) isoform (COX-1, COX-2) inhibition, alone or in combination with nitric-oxide synthase (NOS) blockade, on in vitro tracheal muscle responsiveness to histamine were investigated in healthy and ovalbumin (OVA)-sensitized guinea pigs. Immunohistochemistry showed that COX-1 and COX-2 are constitutively present in normal guinea pig trachea, particularly in the epithelial layer, and that COX-2 expression is enhanced in OVA-sensitized animals both in epithelial and subepithelial tissues. In normal guinea pigs, SC-560 [5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole] (COX-1 inhibitor) or DFU [5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl)phenyl-2(5H)-furanone] (COX-2 inhibitor) significantly increased the contractile response to histamine, these effects being not additive. NOS inhibition by l-N(G)-nitro-arginine methyl ester (l-NAME) did not affect histamine-induced contraction but reversed the increase caused by COX-1 blockade while not modifying the enhancement associated with COX-2 inhibition. In guinea pigs subjected to OVA sensitization and challenge, COX-2, but not COX-1, inhibition enhanced the motor responses to histamine without any influence by l-NAME. In normal, but not in sensitized animals, the removal of epithelial layer from tracheal preparations abolished the enhancing action of DFU on histamine-mediated contraction. A COX-2-dependent release of prostacyclin (PGI(2)), but not prostaglandin E(2), was observed in tracheal tissues from normal and OVA-sensitized guinea pigs. In conclusion, both COX-1 and COX-2 are constitutive in guinea pig trachea, and COX-2 expression is enhanced by OVA sensitization; in normal animals, epithelial COX-2 exerts a PGI(2)-dependent inhibitory control on tracheal contractility, and this isoform is subjected to upstream regulation by epithelial COX-1 and NOS through a complex interplay; and following antigen sensitization, the inhibitory control on tracheal contractility is maintained by COX-2 induced at subepithelial cell sites.

Constitutive expression of cyclooxygenase-2 in the neuromuscular compartment of normal human colon

Prostaglandins regulate various functions throughout the gastrointestinal system. Their biosynthesis depends on cyclooxygenase isoforms, named COX-1 and COX-2. The initial hypothesis that COX-2 is an inducible enzyme has been challenged and its constitutive expression in the stomach has been established. In this study, an immunohistochemical analysis was performed to evaluate the distribution and cellular localization of COX-2 in normal human colon. Colonic surgical specimens were processed for COX-2, protein HuC/HuD, neurofilament, S-100 protein and CD117/c-kit immunodetection. COX-2 protein was found to be constitutively expressed in the colonic wall: detectable amounts were localized in mucosal, submucosal and muscular layers, mainly in the neuromuscular compartment. In particular, COX-2 was expressed in muscularis mucosae, submucosal ganglia, longitudinal muscle layer and myenteric ganglia, the neurons of which displayed different degrees of immunostaining. Intramuscular interstitial cells of Cajal, regarded as important sites for the regulation of enteric neuromuscular activity, were also partly COX-2 immunoreactive. This study provides a detailed mapping of COX-2 expression in human colon, and allows better understanding of the roles played by this isoenzyme in gut physiology.

Differential role of cyclooxygenase 1 and 2 isoforms in the modulation of colonic neuromuscular function in experimental inflammation

This study examines the role played by cyclooxygenase (COX) isoforms (COX-1 and -2) in the regulation of colonic neuromuscular function in normal rats and after induction of colitis by 2,4-dinitrobenzenesulfonic acid (DNBS). The expression of COX-1 and COX-2 in the colonic neuromuscular layer was assessed by reverse transcription-polymerase chain reaction and immunohistochemistry. The effects of COX inhibitors on in vitro motility were evaluated by studying electrically induced and carbachol-induced contractions of the longitudinal muscle. Both COX isoforms were constitutively expressed in normal colon; COX-2 was up-regulated in the presence of colitis. In normal and inflamed colon, both COX isoforms were mainly localized in neurons of myenteric ganglia. In the normal colon, indomethacin (COX-1/COX-2 inhibitor), SC-560 [5-(4-chloro-phenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole] (COX-1 inhibitor), or DFU [5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5H)-furanone] (COX-2 inhibitor) enhanced atropine-sensitive electrically evoked contractions. The most prominent effects were observed with indomethacin or SC-560 plus DFU. In the inflamed colon, SC-560 lost its effect, whereas indomethacin and DFU maintained their enhancing actions. These results were more evident after blockade of noncholinergic pathways. In rats with colitis, in vivo treatment with superoxide dismutase or S-methylisothiourea (inhibitor of inducible nitric-oxide synthase) restored the enhancing motor effect of SC-560. COX inhibitors had no effect on carbachol-induced contractions in normal or DNBS-treated rats. In conclusion, in the normal colon, both COX isoforms act at the neuronal level to modulate the contractile activity driven by excitatory cholinergic pathways. In the presence of inflammation, COX-1 activity is hampered by oxidative stress, and COX-2 seems to play a predominant role in maintaining an inhibitory control of colonic neuromuscular function.

Morphological features of ovine embryonic lung fibroblasts cultured on different bioactive scaffolds

Tissue regeneration with autologous cell transplantation is one of the most important goals in clinical research. In this field, the development of bioactive materials that provide microenvironments for cell-matrix interactions mimicking biological conditions is required. In recent years, many synthetic materials have been developed as scaffolds and many procedures for the surface modification of these materials have been applied using biological molecules. In this study, we analyzed the morphology and the molecule production by ovine embryonic lung fibroblasts cultured on three different sponge-like matrices based on poly(L-lactic acid) (PLLA): agarose/PLLA, crosslinked and uncrosslinked gelatin/PLLA. The matrices were produced by using an emulsion freeze-drying method leading to the formation of sponge-like materials with high porosity and with interconnection between the pores. In vitro MTT test demonstrated that transplanted cells were viable and metabolically active. Morphological analysis revealed that fibroblasts adhered to and penetrated the polymeric structures. Moreover, all the different matrices supported fibroblast production of proteoglycans, glycoproteins, and matrix molecules such as elastin, collagen I, and fibronectin. These data suggest that the tested bioactive scaffolds may support the growth and extracellular matrix molecule production of fibroblasts allowing in vitro connective tissue regeneration.

Migration of human and mouse primordial germ cells and colonization of the developing ovary: An ultrastructural and cytochemical study

This review is an account of the origin and migratory events of primordial germ cells until their settlement in the gonad before sexual differentiation in the human as well as mice. In this context, the morphodynamic characteristics of the migration of the primordial germ cells, the macromolecular characteristics of the extracellular matrix of the migratory pathway, and the factors involved in the germ cell guidance have been analyzed and discussed in the light of recent advances in this field, by means of immunocytochemical procedures. The events prior to gonadal morphogenesis and the origin of the somatic cell content of the human gonadal primordium have been also analyzed. In particular, evidences are presented showing that cells derived from the coelomic epithelium and mesenchyme are at the origin of the somatic components of the gonadal primordium, and that a mesonephric cell contribution to the generation of somatic cell components of the genital ridge in humans should be discarded due to the morphological stability of the different nephric structures during the period preceding the sexual differentiation of the gonad.

Integrin-linked kinase mediates bone morphogenetic protein 7-dependent renal epithelial cell morphogenesis

Bone morphogenetic protein 7 (BMP7) stimulates renal branching morphogenesis via p38 mitogen-activated protein kinase (p38(MAPK)) and activating transcription factor 2 (ATF-2) (M. C. Hu, D. Wasserman, S. Hartwig, and N. D. Rosenblum, J. Biol. Chem. 279:12051-12059, 2004). Here, we demonstrate a novel role for integrin-linked kinase (ILK) in mediating renal epithelial cell morphogenesis in embryonic kidney explants and identify p38(MAPK) as a target of ILK signaling in a cell culture model of renal epithelial morphogenesis. The spatial and temporal expression of ILK in embryonic mouse kidney cells suggested a role in branching morphogenesis. Adenovirus-mediated expression of ILK stimulated and expression of a dominant negative ILK mutant inhibited ureteric bud branching in embryonic mouse kidney explants. BMP7 increased ILK kinase activity in inner medullary collecting duct 3 (IMCD-3) cells, and adenovirus-mediated expression of ILK increased IMCD-3 cell morphogenesis in a three-dimensional culture model. In contrast, treatment with a small molecule ILK inhibitor or expression of a dominant negative-acting ILK (ILK(E359K)) inhibited epithelial cell morphogenesis. Further, expression of ILK(E359K) abrogated BMP7-dependent stimulation. To investigate the role of ILK in BMP7 signaling, we showed that ILK overexpression increased basal and BMP7-induced levels of phospho-p38(MAPK) and phospho-ATF-2. Consistent with its inhibitory effects on IMCD-3 cell morphogenesis, expression of ILK(E359K) blocked BMP7-dependent increases in phospho-p38(MAPK) and phospho-ATF-2. Inhibition of p38(MAPK) activity with the specific inhibitor, SB203580, failed to inhibit BMP7-dependent stimulation of ILK activity, suggesting that ILK functions upstream of p38(MAPK) during BMP7 signaling. We conclude that ILK functions in a BMP7/p38(MAPK)/ATF-2 signaling pathway and stimulates epithelial cell morphogenesis.

Thyroid dysfunction in megalin deficient mice

Megalin mediates transcytosis of thyroglobulin (Tg), the thyroid hormone precursor, resulting in its passage into the bloodstream. The process involves especially hormone-poor Tg, which may favour hormone secretion by preventing competition with hormone-rich Tg for proteolytic degradation. To gain more insight into the role of megalin, here we studied thyroid function and histology in megalin deficient mice compared with WT mice. As expected from the knowledge that megalin mediates Tg transcytosis, serum Tg levels were significantly reduced in homozygous (megalin-/-) mice, which, more importantly, were found to be hypothyroid, as demonstrated by significantly reduced serum free thyroxine and significantly increased serum thyroid stimulating hormone (TSH) levels. In heterozygous (megalin+/-) mice, in which megalin expression was normal, thyroid function was unaffected. Although the serological phenotype in megalin-/- mice was not associated with histological alterations or goiter, our results support a major role of megalin in thyroid hormone secretion.

Kidney Expression of RhoA, TGF-β1, and Fibronectin in Human IgA Nephropathy

BACKGROUND

The Rho/transforming growth factor-beta (TGF-beta) system plays a crucial role in the progression of renal damage due to stimulation of extracellular matrix molecule deposition. In fact, the in vitro TGF-beta-mediated production of fibronectin, one of the major TGF-beta-regulated extracellular components, has recently been correlated with Rho protein signalling molecules. Although a close relationship between increased renal tissue levels of TGF-beta1 and fibronectin has been reported in IgA nephropathy, no data are available on renal tissue expression of Rho proteins.

METHODS

This study was designed to assess in IgA nephropathy patients the kidney tissue immunohistochemical expression of RhoA, TGF-beta1, and fibronectin, and the rate of immunoreactivity for each antigen by image analysis.

RESULTS

An increase in RhoA, TGF-beta1, and fibronectin expression was detected in tubulointerstitium and in glomeruli of IgA nephropathy compared to normal kidneys; in particular, RhoA was found also in proximal tubules, unlike control kidneys and mainly at the cell boundary level, which is in keeping with its activated form. The image analysis confirmed that the kidney tissue levels of RhoA, TGF-beta1, and fibronectin were significantly enhanced in the patients.

CONCLUSION

This study suggests that RhoA may represent a key molecule in the signalling transduction pathway of profibrotic signals in IgA nephropathy.

Cyclooxygenase-2 Inhibition Improves Vascular Endothelial Dysfunction in a Rat Model of Endotoxic Shock: Role of Inducible Nitric-Oxide Synthase and Oxidative Stress

We investigated whether cyclooxygenase (COX) isoforms (COX-1 and COX-2) and decreased NO availability contribute to endothelial dysfunction in endotoxemic rats. The involvement of reactive oxygen species (ROS) was also evaluated. Rats were injected with Salmonella-derived lipopolysaccharide or saline. After 6 h, endothelial function of mesenteric resistance arteries was evaluated. In controls, acetylcholine (ACh)-induced relaxation was inhibited by the nitric-oxide synthase inhibitor N(G)-monomethyl-l-arginine (l-NMMA) and unaffected by 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl)-phenyl-2(5H)-furanone (DFU) (COX-2 inhibitor). In lipopolysaccharide (LPS)-treated rats, the response to ACh was blunted compared with controls, less sensitive to l-NMMA, and enhanced by DFU. COX-2 blockade also improved the inhibitory effect of l-NMMA on cholinergic relaxation. SC-560 [5-(4-clorophenyl)-1-(4-metoxyphenyl)-3-trifluoromethylpirazole] (COX-1 inhibitor) did not modify the response to ACh in both groups. LPS-induced endothelial dysfunction was unaffected by the thromboxane A(2) (TxA(2)) receptor antagonist SQ-29548 (7-[3-[[2-[(phenylamino)carbonyl]hydrazino]methyl]-7-oxabicyclo[2.2.1] hept-2-yl]-[1S(1alpha,2alpha(Z),3alpha,4alpha)]-5-heptenoic acid). In vivo inducible nitric-oxide synthase (iNOS) inhibition by S-methylisothiourea partly attenuated LPS-induced endothelial dysfunction. The antioxidants ascorbic acid and superoxide dismutase normalized endothelium-dependent relaxation and restored the inhibitory action of l-NMMA on ACh. Responses to sodium nitroprusside were similar in both groups. In LPS-treated rats, reverse transcription-polymerase chain reaction showed a marked increase in mesenteric iNOS and COX-2 expressions, whereas endothelial nitric-oxide synthase and COX-1 were unchanged. LPS-induced COX-2 overexpression was reduced but not abrogated by S-methylisothiourea. LPS-induced COX-2 up-regulation was also documented by immunohistochemistry. In conclusion, mesenteric resistance vessels from endotoxemic rats show impaired endothelial function due to reduced NO availability, a condition that is partly ascribable to an iNOS-dependent enhanced COX-2 expression, whereas TxA(2) does not seem to be involved. Oxidative stress is the main mechanism responsible for reduced NO availability, and COX-2 might act as a source of ROS.

Expression of laminin and fibronectin in renal dysplasia

The pathogenesis of renal dysplasia is a matter of debate. Recent theories have conceptualized the role of extracellular matrix proteins in the genesis of renal dysplasia. During normal nephrogenesis, collagen type I and III and fibronectins are lost and laminin and syndecan appear once proper induction has occurred. Any deviation from the normal pattern is said to lead to dysplasia. In this study, the expressions of adhesive glycoproteins, laminin, and fibronectin were studied immunohistochemically in 25 autopsy cases of renal dysplasia and normal age-matched control cases. These cases of renal dysplasia were categorized into 3 groups based on the period of gestation: 20 to 26 weeks, 27 to 33 weeks, and 34 to 40 weeks. The immunohistochemical findings were graded from 0 to 4+ based on the visual intensity. Chi-square analysis was used to calculate the difference in expressions of laminin and fibronectin in cases and controls as a whole and within and between age groups. Immunostaining for laminin in all age groups showed a significant difference in expression between dysplastic kidneys (less expression) and normal controls (greater expression). In the case of fibronectin expression, all but 1 group showed a significant difference, with dysplastic kidneys showing more and normal controls showing less expression. The inference derived is that laminin expression decreases and fibronectin expression increases in renal dysplasia compared with normal nephrogenesis.

Immunohistochemical demonstration of the small GTPase RhoA on epoxy-resin embedded sections

The purpose of the present study was to establish a method for light microscopical immunohistochemical localization of the small G protein RhoA on specimens treated and embedded for routine transmission electron microscopy. There are advantages in antigen immunolocalization on resin semi-thin sections compared to cryostat or paraffin sections: the preservation of morphological details, the well-defined immunoprecipitate localization and the possibility to correlate the immunohistochemical results with those obtained by electron microscope on neighbouring sections. These advantages are particularly useful for the subcellular localization of low molecular weight proteins such as RhoA, a small G protein able to cycle from the inactive cytoplasmic form to the plasma membrane-bound active form.

Cellular and subcellular localization of the small G protein RhoA in the human and rat embryonic and adult kidney

Rho proteins, a subgroup of the Ras GTPase superfamily, control many cellular processes and morphogenetic events by acting as signaling molecules in the transduction pathways of various receptors. Among the "Rho-dependent" receptors are the extracellular matrix- and growth factor-binding sites; these are particularly involved in the modulation of renal development since they control the epithelial-mesenchymal interactions that drive kidney organogenesis. The present study has addressed the immunohistochemical localization of RhoA in developing and adult kidneys of rats and humans because: a) Rho proteins are known to have a morphogenetic role, b) data in the literature on expression of Rho GTPases during mammalian histogenesis and organogenesis are scarce, and c) their involvement in the transduction pathways of receptors is implicated in kidney development. In particular, RhoA peptide was found to be localized in the mesonephric duct and vesicles in both rats and humans; metanephric anlagen were mainly stained in ampullar-derived cells. Periglomerular tubules of fetal and adult kidneys as well as collecting ducts of adult kidneys showed intense staining. Therefore, the present study provides new information on the distribution patterns of RhoA during early stages of mammalian kidney development suggesting that this signaling molecule may take part in epithelial-mesenchymal induction processes that control kidney organogenesis. RhoA expression in adult structures may be linked with renewal of renal epithelial cells and the maintenance of their morphology and polarity.

Immunohistochemical distribution of laminin-5 gamma2 chain and its developmental change in human embryonic and foetal tissues

Immunohistochemical distribution of laminin gamma2 chain, a subunit of the basement membrane protein laminin-5, was examined in 19 cases of human embryos and foetuses ranging from 4 to 25 weeks of gestation. Laminin gamma2 was first detected in the basement membranes underlying ectodermal epithelial tissues, such as the skin and tooth, as early as 5-6 weeks of gestation. Between 6-7 and 12-13 weeks, laminin gamma2 was detected in the basement membranes of various endodermal epithelial tissues, such as the bronchus, oesophagus, stomach, intestines, urinary bladder, gallbladder and hepatopancreatic duct. The deposition of laminin gamma2 in basement membrane was associated with the process of morphogenesis. In the small intestine, laminin gamma2 first appeared in the basement membrane of the primitive short villi, and its level gradually increased in the villus region but decreased in the cryptic region during the maturation of the organ. In addition, non-basement membrane immunoreactivity for laminin gamma2 was detected in some mesoderm-derived tissues, such as the cartilage and skeletal and smooth muscle fibres. These results suggest a common role of laminin-5 and some specific roles of its gamma2 chain in the morphogenesis of human tissues.

TGF-alpha mRNA expression in renal organogenesis: a study in rat and human embryos

The peptides belonging to the epidermal growth factor (EGF) family play a significant role in kidney development by binding the EGF receptor. Transforming growth factor-alpha (TGF alpha), a member of this family, is thought to be the fetal ligand of the EGF receptor. The present study aims to localize the TGF alpha transcripts in rat and human embryonic kidneys using a nonradioactive in situ hybridization method on paraffin-embedded embryonic samples. The results obtained in this study, beside demonstrating the usefulness of the nonradioactive technique for the detection of TGF alpha mRNA in paraffin sections, allowed TGF alpha-producing cells to be seen in developing kidneys. TGF alpha mRNA and its respective peptide were found in the primitive mesonephric structures and within metanephric blastema and ureteric bud cells. The presence of the TGF alpha gene transcript in the developing rat and human kidney suggests that the TGF alpha peptide is of embryonic origin and that it may contribute to renal organogenetic processes together with other growth factors.