Spatiotemporal expression of molecules associated with junctional complexes during the in vivo maturation of renal podocytes.

Epithelial glomerular cells differentiate from mesenchymal cells of the metanephrogenic blastema. During the first stages of glomerulogenesis, the cells acquire the morphological features of epithelial cells. Then, podocytes lose these characteristics at the maturing glomerular stage. We have studied the molecules associated with junctional complexes during glomerular differentiation in human and pig fetal kidneys. We show for the first time the expression of P-cadherin in renal cells. Epithelial cells of ureteral buds and ampullae display all the molecules associated with junctional complexes and coexpress E- and P-cadherin. However, P-cadherin, plakoglobin and vinculin are the only markers detected in future glomerular cells. We have established a spatiotemporal correlation between the time of appearance and disappearance of junctional complexes as previously described (Saxén and Wartiovaara, Int. J. Cancer 1:271-290, 1966; Saxén et al., Adv. Morphog. 7:251-293, 1968; Reeves et al., Lab. Invest. 39:90-100, 1978), and the expression of their associated molecules. Epithelial cells with stable, typical junctional complexes strongly express the molecules associated with junctions, whereas cells endowed with transient, atypical junctional complexes express low amounts of components associated with junctions. These observations suggest a correlation between the level of expression of these components and an authentic, stable epithelial phenotype.

Membranous glomerulonephritis associated with anti-tubular and anti-alveolar basement membrane antibodies.

The renal biopsy of a 3-year old boy with complete Fanconi syndrome showed the association of a membranous glomerulonephritis with severe tubulointerstial changes. Immunofluorescence microscopy disclosed linear and granular deposits of Ig along tubular basement membranes. The presence of anti-tubular basement membrane antibodies in the patient's serum was demonstrated by indirect immunofluorescence and radioimmunoassay. The child also developed pulmonary involvement associated with episodes of acute anemia. Anti-alveolar basement membrane antibodies were detected by indirect immunofluorescence. The present case is the first reported example of auto-immune disease characterized by the presence of anti-tubular and alveolar basement membrane antibodies associated with an immune complex glomerulonephritis.

Recurrence of de novo membranous glomerulonephritis on renal grafts.

An updated study of the glomerular lesions found in renal grafts in children showed 3 features of interest. 1) In our experience, the incidence of the occurrence of de novo membranous glomerulonephritis (MGN) remains around 9% (48 of 530 grafts). 2) Of the 29 patients we reported in a previous study [Antignac et al. 1988], 18 lost their grafts and 7 received a second graft. Four of these 7 patients recurred de novo MGN on their second graft. Their clinical course is reported in detail. 3) In our population of transplanted children, of the 55 patients who received a second graft, the only recipients who developed a de novo MGN were the 4 patients who had already developed de novo MGN on their first graft. The various factors possibly involved in the pathogenesis of de novo MGN are reviewed. The high incidence of recurrence of de novo MGN indicates that host factors play a major role in the development of this nephropathy.

[Course of renal lesions in disseminated lupus erythematosus]. / Evolution des lésions rénales du lupus érythémateux disséminé.

Clinical and biological features, histologic findings, and outcome were studied in 32 children with systemic lupus erythematosus who underwent at least two renal biopsies during the course of their disease. Results showed that renal biopsy was a useful aid for therapy in that it demonstrated the presence or absence of disease activity, but was unhelpful for predicting the long term outcome. Repeat renal biopsies proved an excellent means for monitoring the course of the nephropathy. This study showed that the various patterns of glomerulonephritis seen in SLE may exhibit changes over time, with either improvement or progression. Regression of lesions was seen mainly after treatment, whereas progression was associated with renal or extrarenal exacerbations of the disease. The absence of clinical improvement may reflect transformation to histologic forms which are unresponsive to therapy.

Distribution of alpha-integrin subunits in fetal polycystic kidney diseases.

An alteration in cell/matrix interactions is one of the suggested mechanisms leading to cyst formation in polycystic kidney diseases. Most of these interactions are mediated by beta 1-integrins, a subfamily of integrin receptors, formed by the association of the beta 1-chain with different alpha-subunits. To date, no study on alpha-integrin subunit distribution during the early stages of cyst development has been reported. Using immunofluorescence, we analyzed the distribution of alpha-integrin subunits (alpha 1, alpha 2, alpha 3, alpha 5, and alpha 6) and basement membrane proteins in kidneys of fetuses with autosomal dominant (ADPKD) or autosomal recessive polycystic kidney disease (ARPKD). The distribution was compared with that observed in normal fetal and post-natal kidneys, and in fetal cystic dysplasia and Meckel syndrome. Marked increase in alpha 1-integrin staining was observed in normal and cystic collecting duct cells of both polycystic diseases (PKD), compared with normal and cystic controls. The distribution of integrin subunits alpha 2, alpha 3, and alpha 6 was irregular in cyst epithelial cells of PKD and cystic controls. The increased expression of the alpha 1-subunit specifically observed in PKD collecting duct cells may be an early consequence of the genetic defect in ARPKD. In ADPKD it parallels the reported expression of polycystin, the protein product of PKD1. The irregular expression of alpha 2, alpha 3, and alpha 6 integrin subunits observed in all types of cysts suggests that cell/matrix interactions are altered early and may participate in the development of cysts, perhaps by contributing to the deregulation of cell survival in cystic diseases.

[Renal involvement in autoimmune enteropathies]. / Atteinte rénale des entéropathies auto-immunes.

The authors report on a infant who presented with an auto-immune enteropathy characterized by the association of a protracted diarrhea, a neonatal insulin-dependent diabetes, and a dermatitis and who developed a nephrotic syndrome at 4 months of age. A renal biopsy showed a membranous glomerulonephritis (MGN) with IgG linear deposits along the tubular basement membranes (TMB). By indirect immunofluorescence anti-enterocyte antibodies together with anti-TMB antibodies and anti-renal brush border (BB) antibodies were found in the serum of the patient. The patient received various immunosuppressive drugs that failed to improve the disease. In the course of the disease the anti-TBM antibodies disappeared progressively but the BB antibodies persisted. A review of the literature indicates that renal involvement is not uncommon in auto-immune enteropathy and in 5 cases it has been reported as being characterized by a nephrotic syndrome related to the presence of a MGN. In 4 of these cases MGN was associated with the presence of anti-TBM antibodies and in the remaining one with anti-BB antibodies. This case report shows that in human pathology, auto-antibodies to BB proteins may, as well as in experimental models, be responsible for the development of a MGN. It suggests a close relationship (probably a common epitope) between the renal BB proteins and the proteins of the gut epithelium.

Collagen distribution in human membranous glomerulonephritis.

In membranous glomerulonephritis (MGN), thickening of the glomerular basement membrane (GBM) is partly due to the accumulation of basement membrane material between and around immune deposits located on the epithelial aspect of the GBM. We investigated the distribution of type IV collagen chains (alpha 1/alpha 2, alpha 3, alpha 4, alpha 5, alpha 6) and of types I, III, V, and VI collagen in the glomeruli from 16 patients, by indirect immunofluorescence in 13 and the high-resolution immunogold technique in 6. No changes were detected in stage I MGN. The spiky projections of the GBM in stage II MGN and the basement membrane layers encircling immune deposits in stage III contained the alpha 3, alpha 4, and alpha 5 chains of type IV collagen. In contrast, the alpha 1/alpha 2 chains of type IV, as well as type VI collagen accumulated in the subendothelial aspect of the GBM. No significant staining for types I, III, and V collagens or for the alpha 6 chain of type IV collagen was detected. The results show that, as in the normal glomeruli, the different chains of type IV collagen are not co-distributed in the glomerular extracellular matrix in MGN. They also indicate that type IV collagen chains and type IV collagen play an important role in the thickening of the GBM in human MGN.

Collagen distribution in focal and segmental glomerulosclerosis: an immunofluorescence and ultrastructural immunogold study.

Focal and segmental glomerulosclerosis (FSGS) is a non-specific scarring process of the glomerulus, initially described in idiopathic nephrotic syndrome. The distribution of types I, III, IV, V, and VI collagen and of the alpha 1, alpha 3, alpha 4, alpha 5, and alpha 6 chains of type IV collagen was studied by immunohistochemistry in sclerotic lesions of nine nephrotic children. Dual immunofluorescence and high-resolution immunogold labelling were used to determine the precise distribution of the antigens. No changes were detected in normal glomeruli of patients compared with controls. In FSGS, type IV collagen [alpha 1(IV)2 alpha 2(IV)], and to a lesser degree type VI, accumulates in the two components of the lesion: the enlarged mesangial matrix and the material deposited between the pushed-out podocytes and the alpha 3-alpha 5(IV)-positive glomerular basement membrane. Staining for alpha 6(IV) and types I, III, and V collagen was practically negative. These results suggest that the matrix components of the sclerotic lesion are produced solely by glomerular cells. Changes in the relative distribution of type IV collagen chains, characterized by the presence of collagen [alpha 1(IV)2 alpha 2(IV)] in close contact with the podocytes, strongly suggest a switch in the podocyte programme of collagen synthesis.

Ontogenesis of the glomerular C3b receptor (CR1) in fetal human kidney.

Ontogenesis of the glomerular C3b receptor (CR1) was studied in kidneys from 16 fetuses aged from 9 to 32 weeks, using immunohistochemical techniques and the F(ab')2 fragment of a monospecific rabbit antibody to CR1, and adherence of C3b-coated sheep erythrocytes. By indirect immunofluoresence, anti-CR1 stained presumptive glomerular epithelium from the end of the S-body stage of nephron differentiation. Staining increased with visceral epithelial cell proliferation and with differentiation of the nephron from the subcortical to the juxtamedullary part of the fetal kidney. Using electron microscopy and an indirect immunoperoxidase technique, CR1 antigen was detected on the plasma membrane in the basolateral part of primitive podocytes from the late S-body stage, following the acquisition by podocytes of the capacity to synthetize a basal lamina. Endothelial cells and mesangial cells did not stain for CR1 antigen. CR1 antigen was expressed by podocytes from the same stage of glomerular differentiation as was the CALLA antigen. Glomerular expression of CR1 on podocytes preceded that of Ia on glomerular endothelial cells. C3b-bearing sheep erythrocytes only adhered to clover-like lobulated glomeruli at a late stage of glomerular differentiation. Glomerular CR1, a specific marker of glomerular capillary epithelial cells is one of the earliest markers expressed by resident glomerular cells during renal ontogenesis.

Autosomal recessive Alport syndrome: immunohistochemical study of type IV collagen chain distribution.

Alport syndrome (AS) is an hereditary disease of basement membrane collagen. It is mainly transmitted as a dominant X-linked trait and caused by mutations in the COL4A5 gene encoding the alpha 5 chain of type IV collagen. However, autosomal recessive AS due to mutations in the COL4A3 or COL4A4 genes could represent up to 15% of AS. Using the immunofluorescence technique, we analyzed the distribution of the different chains of type IV collagen in renal (12 specimens) and skin (4 specimens) basement membranes of 12 AS patients belonging to 11 unrelated kindreds in which autosomal recessive inheritance had been demonstrated (3 kindreds) or was suggested by clinical and genealogic data (8 kindreds). The renal and skin distribution was normal in one patient with COL4A4 mutations. A peculiar pattern of distribution of the alpha 3-alpha 5(IV) chains was observed in the other patients. It was characterized the co-absence of the alpha 3(IV), alpha 4(IV) and alpha 5(IV) chains in the glomerular basement membrane, and the presence of the alpha 5(IV) chain in a series of extraglomerular basement membranes including capsular, collecting ducts and epidermal basement membranes, a combination never observed in X-linked AS. This immunohistochemical pattern is correlated with the specific distribution of the alpha 3-alpha 5 chains of type IV collagen chains within extraglomerular basement membranes. It could be a useful marker for the identification of autosomal recessive AS.

Development of human fetal kidney in obstructive uropathy: correlations with ultrasonography and urine biochemistry.

In utero urethral obstruction results in bilateral hydronephrosis and severe fetal and post-natal morbidity and mortality. Obstetrical management depends on the indirect evaluation of fetal renal function by ultrasonography and biochemical analysis. No direct evaluation of the severity and possible reversibility of renal lesions is available. In this paper we analyzed kidneys from 34 fetuses (14 to 37 gestational weeks) in which (1) isolated bilateral urinary tract obstruction had been detected in utero by sonography, and (2) the severity of sonographic and biochemical prognostic indicators led to the indication of termination of pregnancy or to perinatal death. Pure hydronephrosis was observed in two young fetuses [14 and 20 gestational weeks (GW)] and was associated with regressive changes in two others. In contrast, a wide spectrum of dysplastic renal lesions was present in 30 fetuses and was classified into four subgroups according to the association of dysplasia, hypoplasia and cysts. They had the following characteristics in common: (1) premature cessation of nephrogenesis assessed by the medullary ray counting method; (2) early disappearance or myofibroblastic differentiation of metanephric blastema; (3) early increase in interstitial mesenchyme with widespread expression of alpha-smooth muscle actin by mesenchymal cells; (4) frequent absence of classical criteria of dysplasia (nests of cartilage were observed in only 5 fetuses); (5) an identification, based upon the detection of alpha-smooth muscle actin expression, of the muscular phenotype of mesenchymal cells encircling primitive ducts. In conclusion, (1) the value of prognostic markers in fetuses less than 20 GW should be reconsidered; (2) after 20 GW there is a good correlation between markers predicting poor prognosis and the severity of renal lesions; (3) hypoplasia with disappearance of blastema cells, dysplasia and early interstitial fibrosis are evidence of the irreversibility of renal lesions and preclude any possibility of new nephron formation; (4) these findings suggest that most surgical in utero procedures are performed when irreversible renal lesions have developed.

Glomerular extracellular matrix and growth factors in diffuse mesangial sclerosis.

UNLABELLED: Diffuse mesangial sclerosis, isolated (IDMS) or observed in the context of Denys-Drash syndrome (DDS) due to WT1 mutation, is characterized by early onset nephrotic syndrome progressing to renal failure. A striking morphological feature is the rapid development of glomerulosclerosis. THE AIMS OF OUR STUDY WERE: (1) to analyze the glomerular distribution of extracellular matrix (ECM) antigens at the early stage of DMS, (2) to determine the composition of the ECM accumulated within the mesangial areas and leading to glomerular sclerosis, and (3) to analyze the expression of growth factors, transforming growth factor-beta 1 (TGF beta 1) and platelet-derived growth factor A (PDGFA). In glomeruli of patients with IDMS and DDS, the glomerular basement membrane (GBM) expression of the heparan sulfate chain of heparan sulfate proteoglycan (HSPG) was decreased from the early stage of DMS, at a time when ECM proteins retained a normal distribution. In fully developed lesions, mesangial and subendothelial accumulation of collagenous and noncollagenous glycoproteins normally expressed in the mesangial area (types IV [alpha 1(IV)2 alpha 2(IV)] and VI collagen, beta 1 laminin, fibronectin, tenascin, and perlecan) increased with progression of mesangial sclerosis. This was associated with mesangial expression of proteins normally restricted to the GBM (agrin, alpha 1/alpha 5, beta 2, and gamma 1 laminin chains) and with accumulation of chondroitin sulfate proteoglycan. The distribution of the alpha 3-alpha 5 chains of type IV collagen was normal. Focal accumulation of types I, III, and V collagen was seen only in severely sclerotic glomeruli. Expression of growth factors TGF beta 1 and PDGFA was increased in 9 of 10 and 5 of 10 patients, respectively. Early decreased GBM expression of the heparan sulfate chain of HSPG could play a role in the proteinuria of DMS patients. Changes in the composition of the ECM accumulated within the mesangial areas are not specific. We speculate that deregulation of the expression of growth factors normally downregulated by WT1, is one of the factors responsible for the rapid and massive mesangial deposition of basement membrane material in DDS.

Diffuse leiomyomatosis associated with X-linked Alport syndrome: extracellular matrix study using immunohistochemistry and in situ hybridization.

Inherited diffuse esophageal leiomyomatosis a benign tumor involving smooth muscle cells of the whole esophagus, is frequently associated with X-linked Alport syndrome, a hereditary disease of type IV collagen. Families with this condition are consistently found to have deletions encompassing the 5' ends of both the alpha 5 chain of type IV collagen (COL4A5) and the alpha 6 chain of type IV collagen (COL4A6) genes, always limited in COL4A6 to exons 1', 1, and 2. On the contrary, patients with COL4A5/COL4A6 deletions extending further into COL4A6 display no such tumors. Despite the deletion, a COL4A6 transcript including exon 4, but not exon 3, was found in a tumor sample, raising the possibility of the involvement of a truncated alpha 6(IV) chain in the tumorous process. Using immunohistochemistry and in situ hybridization methods, we analyzed the expression and distribution of the alpha 6 chain of type IV collagen in tumors in comparison with that of normal, fetal, and mature esophagus. We also studied associated changes in tumor basement membrane composition and in tumor-cell integrin subunit distribution. No labeling with alpha 6(IV) antibodies was detected in tumors, ruling out the hypothesis of a stably integrated truncated alpha 6(IV) chain in tumor basement membranes. In contrast, despite the deletions of the first two exons of the gene and its 5' end, a COL4A6 transcript is clearly expressed by tumor cells. This finding raises the question of a potential role for this RNA in the tumor process. The absence of the alpha 6(IV) chain is associated with the absence of the alpha 5(IV) chain, as was suggested by the COL4A5 deletion. An additional striking feature is the absence of the beta 1 chain of laminin in tumor basement membranes and the lack of or uneven expression of the alpha 5 integrin subunit. These findings show that dramatic changes in the composition of the matrix and the expression of integrin receptors also occur in this benign tumorous process.