Pathological and sonographic review of early isolated severe lower urinary tract obstruction and implications for prenatal treatment.

OBJECTIVE: To identify favorable renal histology in fetuses with early severe lower urinary tract obstruction (LUTO) and determine the best timing and selection criteria for prenatal surgery. METHODS: This multicenter, retrospective study included male fetuses with severe LUTO which died before 24 weeks of gestation during the period January 2000 to December 2018. Age-matched controls were used as reference standard for renal histology. Prenatal ultrasound features and fetal serum and/or urine ß2microglobulin level were retrieved and kidney histology slides (hematein-eosin-safran and α-smooth-muscle-actin (αSMA) immunostaining) were prepared and reviewed. αSMA-positive staining of the blastema is due to its aberrant differentiation into myofibroblastic cells. Cases were sorted into histopathologic groups (favorable or unfavorable) according to the blastema's morphology and αSMA labeling and the data of these groups were compared. RESULTS: Included in the study were 74 fetuses with a median gestational age at outcome of 17 + 6 (range, 13 + 0 to 23 + 5) weeks. Parenchymal organization was preserved in 48% of the kidneys. A blastema was present in 90% of the kidneys, but it was morphologically normal in only 9% and αSMA-negative in only 1% of them. Most (82%) fetuses had an unfavorable prognosis, and 36% of fetuses died ≤ 18 weeks and had severe renal lesions detected on histology (early unfavorable prognosis). A favorable renal prognosis was associated with an earlier gestational age (P = 0.001). Fetuses with LUTO had a significantly lower number of mature glomeruli (P < 0.001) compared with controls. However, there was no significant difference in the number of glomeruli generations between the early-unfavorable-prognosis group (≤ 18 weeks) and the group with a favorable prognosis (P = 0.19). A comparison of prenatal ultrasound features and biochemical markers between groups could not identify any prenatal selection criteria. CONCLUSIONS: Before 18 weeks, around 30% of fetuses with severe LUTO still have potential for kidney development. Identification of these cases would enable them to be targeted for prenatal therapy. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

NPHS2, encoding the glomerular protein podocin, is mutated in autosomal recessive steroid-resistant nephrotic syndrome.

Familial idiopathic nephrotic syndromes represent a heterogeneous group of kidney disorders, and include autosomal recessive steroid-resistant nephrotic syndrome, which is characterized by early childhood onset of proteinuria, rapid progression to end-stage renal disease and focal segmental glomerulosclerosis. A causative gene for this disease, NPHS2, was mapped to 1q25-31 and we report here its identification by positional cloning. NPHS2 is almost exclusively expressed in the podocytes of fetal and mature kidney glomeruli, and encodes a new integral membrane protein, podocin, belonging to the stomatin protein family. We found ten different NPHS2 mutations, comprising nonsense, frameshift and missense mutations, to segregate with the disease, demonstrating a crucial role for podocin in the function of the glomerular filtration barrier.

Identification of mutations in the alpha 3(IV) and alpha 4(IV) collagen genes in autosomal recessive Alport syndrome.

Alport syndrome (AS) is an hereditary disease of basement membranes characterized by progressive renal failure and deafness. Changes in the glomerular basement membrane (GBM) in AS suggest that the type IV collagen matrix, the major structural component of GBM, is disrupted. We recently isolated the genes for two type IV collagens, alpha 3(IV) and alpha 4(IV), that are encoded head-to-head on human chromosome 2. These chains are abundant in normal GBM but are sometimes absent in AS. We screened for mutations in families in which consanguinity suggested autosomal recessive inheritance. Homozygous mutations were found in alpha 3(IV) in two families and in alpha 4(IV) in two others, demonstrating that these chains are important in the structural integrity of the GBM and that there is an autosomal form of AS in addition to the previously-defined X-linked form.

Donor splice-site mutations in WT1 are responsible for Frasier syndrome.

Frasier syndrome (FS) is a rare disease defined by male pseudo-hermaphroditism and progressive glomerulopathy. Patients present with normal female external genitalia, streak gonads and XY karyotype and frequently develop gonadoblastoma. Glomerular symptoms consist of childhood proteinuria and nephrotic syndrome, characterized by unspecific focal and segmental glomerular sclerosis, progressing to end-stage renal failure in adolescence or early adulthood. No case of Wilms' tumour has been reported, even in patients with extended follow-up. In contrast with FS patients, most individuals with Denys-Drash syndrome (DDS; refs 6,7) have ambiguous genitalia or a female phenotype, an XY karyotype and dysgenetic gonads. Renal symptoms are characterized by diffuse mesangial sclerosis, usually before the age of one year, and patients frequently develop Wilms' tumour. Mutations of the Wilms'-tumour gene, WT1, cause different pathologies of the urogenital system, including DDS. WT1 is composed of ten exons and encodes a protein with four zinc-finger motifs and transcriptional and tumour-suppressor activities. Alternative splicing generates four isoforms: the fifth exon may or may not be present, and an alternative splice site in intron 9 allows the addition of three amino acids (KTS) between the third and fourth zinc fingers of WT1 (ref. 17). Here we demonstrate that FS is caused by mutations in the donor splice site in intron 9 of WT1, with the predicted loss of the +KTS isoform. Examination of WT1 transcripts indeed showed a diminution of the +KTS/-KTS isoform ratio in patients with FS.

A missense mutation in podocin leads to early and severe renal disease in mice.

Mutations in the NPHS2 gene, encoding podocin, are responsible for familial autosomal recessive and sporadic cases of steroid-resistant nephrotic syndrome. We have successfully generated a mouse model in which the common p.R138Q mutation found in nephrotic patients is expressed in the kidney. Homozygous mice express the mutant protein, which is mislocated to the cytoplasm, along with a portion of the nephrin pool. These mice die within the first month of life, but their survival depends on the genetic background. Albuminuria manifests early and leads to progressive renal insufficiency, characterized histologically by diffuse mesangiolysis and mesangial sclerosis, endothelial lesions along with podocyte abnormalities such as widespread foot process effacement. Gene expression profiling revealed marked differences between these and the podocin-null mice, including significant perturbations of podocyte-expressed genes such as Cd2ap, Vegfa and the transcription factors Lmx1b and Zhx2. Upregulation of Serpine1 and Tgfb1 implicates these as potential mediators of disease progression in these mice. This mouse model of nephrotic syndrome may serve as a valuable tool in studies of in vivo intracellular protein trafficking of podocyte proteins, as well as testing therapeutic modalities aimed at correcting the targeting of mutant proteins.

Renin biosynthesis by human tumoral juxtaglomerular cells. Evidences for a renin precursor.

Renin biosynthesis was studied in a juxtaglomerular cell tumor. The tumoral tissue had a high renin content (180 Goldblatt Units/g of tissue), was heavily stained by immunofluorescence using human renin antiserum, and exhibited numerous characteristic secretory granules by electron microscopy. In one series of experiments, renin biosynthesis was studied in tissue slices, by following the incorporation of radiolabeled amino acids into specific immunoprecipitable renin. Time course studies showed that renin was first synthesized in a high molecular weight form, 55,000 mol wt, i.e., 10,000 mol wt higher than that of active renin, and was then converted into a 44,000-mol wt form. In a second series of experiments renin tumoral cells were cultured. Small, round, birefringent cells obtained after collagenase digestion produced renin in both primary culture and subculture media. After 5 d most of the renin found in the culture medium was inactive, but could be activated by trypsin treatment. The tumoral tissue exhibited a strong renin immunofluorescence and numerous secretory granules were observed by electron microscopy. In contrast, the renin-producing cells isolated from this tumor and grown in culture showed little renin immunofluorescence and no secretory granule could be observed. The renin-producing cells in primary culture and subculture were pulsed with radiolabeled amino acids, and immunoprecipitable radiolabeled renin was found in the culture media, thus demonstrating the actual biosynthesis of the enzyme. This renin was not stored inside cultured cells but was rapidly released into the medium and had a molecular weight of 55,000. No conversion of this inactive high molecular weight renin into the active, 44,000 mol wt form of renin was observed. We postulate the existence of two pathways for the processing, packaging, and secretion of renin in the tumoral cells: in juxtaglomerular cells of tumoral tissue renin is synthesized as a preprorenin and rapidly converted into prorenin (55,000 mol wt), which is in turn packaged in secretory granules where it is processed into active renin (44,000 mol wt) and finally secreted; in the cultured tumoral cells renin is still biosynthesized as a preprorenin molecule and then converted into prorenin, but is neither stored as granules nor processed into active renin. In this case the renin is released in an inactive form.

[Renal tubular dysgenesis and mutation in the renin gene]. / Dysgénésie tubulaire proximale et mutation du gène de la rénine.

Renal tubular dysgenesis is a severe and rare disorder of the renal development characterized by fetal anuria, oligohydramnios and early death from pulmonary hypoplasia and refractory arterial hypotension. We report on a female patient who presented with anuria in the neonatal period, requiring peritoneal dialysis until 5 months of age with unexpected diuresis recovery at 2 months of age. Clinical, histological and pathophysiological issues are discussed for this disease related to a mutation in the renin gene.

[Autosomal recessive renal tubular dysgenesis: morphologic and genetic study of 2 cases]. / Dysgénésie tubulaire rénale autosomique récessive: étude morphologique et génétique de 2 nouveaux cas.

Renal tubular dysgenesis (RTD) is a rare and severe nephropathy characterized by persistent fetal anuria leading to oligohydramnios with the Potter sequence, and perinatal death. The diagnosis is based on the histological finding of absence or paucity of proximal tubules. A consanguineous family is described in which 2 siblings, born after pregnancies complicated by oligohydramnios were affected with RTD. Patients were small for gestational age at birth. The first patient died after a few hours, the second after a few days of life, with persistent anuria unresponsive to treatment. Histologically, there was marked reduction in the number of proximal tubule sections and no renin was detected by immunohistochemistry. An homozygous mutation of the gene encoding renin was identified in both patients. This study underlines the interest of the histological examination of the kidney for the diagnostic of RTD in anuric fetuses and newborns, and the possibility of mutation analysis of RAS genes for genetic counselling and early prenatal diagnosis.

Familial juvenile nephronophthisis.

Familial juvenile nephronophthisis (NPH) is an autosomal recessive interstitial nephritis leading to terminal renal failure around puberty. Associations with extrarenal symptoms have been reported, mainly with Leber amaurosis (termed Senior-Løken syndrome). By means of linkage analysis a gene NPH1 for the purely renal form of NPH has been localized to chromosome 2. Genetic heterogeneity has been shown between NPH and Senior-Løken syndrome and also within the group of isolated NPH cases. Further characterization of the NPH1 region led to the isolation of large homozygous deletions in approximately 70% of patients with NPH. The detection of these deletions by PCR represents a simple noninvasive method for precise diagnosis in the majority of patients suspected of having NPH.

[Immunohistochemistry contribution in Alport syndrome diagnosis]. / Apport de l'immunohistochimie dans le diagnostic du syndrome d'Alport.

UNLABELLED: Alport syndrome (AS) is an hereditary disease characterised by the association of progressive hematuria nephritis. The diagnosis is based on clinical genetic and ultrastructural findings. Nowadays, immunohistochemical technique is of great interest. It enables us to analyze the distribution of the different chains of the type IV collagen in renal basement membrane (RBM) and epidermal basement membrane (EBM) which appeared to be abnormal in 70% of cases. METHODS: We report a prospective study of five families affected with AS. Six patients were investigated by immunohistochemical studies of kidney (3 cases) and skin (6 cases) frozen specimens. Monoclonal antibodies recognizing the collagenous domain of alpha1 (MAB1), alpha3 (MAB3) and alpha5 (MAB5) chains of type IV collagen were used. Two methods were performed: direct immunofluorescence and immunohistochemical (ultravision) analysis. RESULTS: The different chains distribution of type IV collagen in the EBM and RBM was normal in four cases (4 men), abnormal in two patients (1 man and woman). Based on the clinical, genetical and immunohistochemical findings we established three transmission modes: autosomal recessive in two families, dominant X linked in two other familiales, and autosomal dominant in one family. CONCLUSION: Immunohistochemical studies is a simple technique of an easy interpretation accomplished on kidney frozen specimen, or even on a simple cutaneous biopsy. It could be very useful for the diagnosis and enables us in addition to determine the mode of transmission of AS.

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.

PAX2 mutations in renal-coloboma syndrome: mutational hotspot and germline mosaicism.

The renal-coloboma syndrome (RCS, MIM 120330) is an autosomal dominant disorder caused by PAX2 gene mutations. We screened the entire coding sequence of the PAX2 gene for mutations in nine patients with RCS. We found five heterozygous PAX2 gene mutations: a dinucleotide insertion (2G) at position 619 in one sporadic RCS case, a single nucleotide insertion (619 + G) in three unrelated cases, and a single nucleotide deletion in a familial case. In this familial case, three affected sibs showed a striking ocular phenotypic variability. Each of the sibs carried a 619insG mutation, whilst unaffected parents did not, suggesting the presence of germline mosaicism. Interestingly, the 619insG mutation has been previously reported in several patients and is also responsible for the Pax21Neu mouse mutant, an animal model of human RCS. This study confirms the critical role of the PAX2 gene in human renal and ocular development. In addition, it emphasises the high variability of ocular defects associated with PAX2 mutations ranging from subtle optic disc anomalies to microphthalmia. Finally, the presence of PAX2 germline mosaicism highlights the difficulties associated with genetic counselling for PAX2 mutations.

Dark cells of cystinosis: occurrence in renal allografts.

Twenty-four biopsies of renal allografts, generally cadaveric, from 20 patients with cystinosis were examined by light, polarization, phase contrast, and electron microscopy. The unusual dark cells previously reported in the native kidneys and livers of patients with cystinosis were observed in 12 of the 24 biopsies. The cells were present in the interstitium in all of these 12 biopsies, in glomeruli in one biopsy, and in the tubular lumen in two biopsies. They were evident by light and electron microscopy in stained and unstained ultrathin sections, and could be discerned solely in Epon sections. The dark appearance resulted from the presence of dark, fine granular material in the cytoplasm and nucleus and in cytoplasmic inclusions. The cells were judged to be macrophages. They were present as early as 3 months following transplantation and bore no relationship to interstitial crystals or inflammation. The dark cells have two important implications: cystine storage may not be limited to lysosomes, and dark cells are a morphologic alternative to the traditional identifying configuration of cystine in tissues, namely crystals.

Adverse effect of proteins on remnant kidney: dissociation from that of other nutrients.

Several experiments have shown that deterioration of renal parenchyma after reduction of functional mass is affected by the protein content of the diet. The respective role of proteins and that of other nutrients that vary with proteins were never clearly separated. Three groups of 9 uremic rats received diets differing exclusively in protein (casein) content, which was 8% (group 1), 16% (group 2), and 32% (group 3). Energy and minerals were maintained identical. Food intake was similar in groups 1 and 2 and was lower in group 3. Mortality rate remained closely related to protein intake. Of group 3 rats, 78% died within 10 weeks and 100% within 15 weeks. Of group 2 rats, 56% were dead at week 15, and 100% at week 30. Mortality occurred significantly later in group-1 rats fed the lowest protein diet. Histology of remnant kidneys showed severe glomerular and tubular damage, with no or little calcium deposits despite normal phosphorus diet and frequent hyperphosphatemia. These data suggest that protein intake, independent of any other nutrient, influences survival by accelerating the renal damage in rats with reduced kidney mass.

A specific glomerular lesion of the graft: allograft glomerulopathy.

During the period from January 1973 to December 1970, 774 renal transplantations in 698 children have been performed in our Renal Unit. A total of 540 grafts have been examined both by light and immunofluorescence microscopy at least once. Recurrent glomerulonephritis was diagnosed in 62 grafts, de novo glomerulonephritis in 68 and allograft glomerulopathy (AGP) in 38. AGP was defined as a lesion affecting all glomeruli and characterized by widespread reduplication of the GBM with widening of the subendothelial space and interposition of mesangial matrix and without significant deposits by immunofluorescence. The aim of the current study is to describe the natural history of AGP and to delinate its clinical significance. At time of biopsy, an increase in serum creatinine was present in 30 patients associated with a proteinuria > or = 1 g/day in 21. During the post-transplantation course, proteinuria was present in 29 patients and associated with a nephrotic syndrome in 10 of them. With a mean follow-up of eight years seven months, two patients died, 23 lost their grafts and 13 have a functioning graft. The lesions of AGP recurred in three of the nine children who received a second graft. Thirteen of the 33 patients in whom earlier biopsies were performed showed a different pattern of involvement characterized by a prominent swelling of active endothelial and mesangial cells and a hypercellularity related to the presence of mononuclear cells both in the lumens and in the mesangial areas.(ABSTRACT TRUNCATED AT 250 WORDS)

Alport's syndrome: experience at Hôpital Necker.

We review the characteristic morphologic features identifiable by electron microscopy that have been described in patients presenting with Alport's syndrome. They are diffuse thickening and splitting of the glomerular basement membrane (GBM), which are either isolated or associated with thinning. In occasional cases, only diffuse thinning can be seen. Our study of 100 families followed in Necker's hospital, of which 60 patients have had electron microscopic examination of their renal parenchyma, demonstrates that these GBM changes are highly suggestive of Alport's syndrome. All the patients included in the study fulfilled the following clinical criteria: familial incidence, nerve deafness in the propositus or in another member of the family, renal disease with progression to renal failure in the proband or in another member of the kindred. Although a failure in the proband or in another member of the kindred. Although a normal GBM was found in five patients, the GBM changes should be one of the criteria for the definition of the syndrome. Results dealing with a few other problems raised by this syndrome are reported. They concern the antigenicity and the biochemical composition of the GBM, the incidence of macular and perimacular changes, and the genetic transmission of the disease. It is concluded that Alport's syndrome is genetically heterogeneous and that the GBM ultrastructural changes are observed in most patients whatever the type of genetic transmission.

Renal allografts in cystinosis and mesangial demography.

Twenty-four biopsies of generally cadaveric renal allografts from 20 patients with cystinosis were examined by light, polarization, phase contrast and electron microscopy. Cystine crystals, or cytoplasmic crystalline spaces compatible with cystine, were observed in interstitial cells in 23 of the 24 biopsies and in glomeruli in six. Among the six, crystalline spaces were identified by electron microscopy in cells compatible with macrophages in the mesangium in two, and, in one of the latter, dark, presumably cystine-containing cells were also present in the mesangium. On the premise that cystine-containing cells derive from the host, these findings support the thesis that in man cells of the mononuclear phagocyte system of extrarenal origin may exist in the mesangium. However, in comparison with infiltration of the interstitium, infiltration of the glomerulus by macrophages from extrarenal sources is scant, as studied under conditions of renal transplantation.

The significance of pure diffuse mesangial proliferation in idiopathic nephrotic syndrome.

The prognostic significance of the finding of diffuse mesangial proliferation (DMP) in patients presenting with idiopathic nephrotic syndrome (INS) has not been well established. The clinical course, therapeutic response and final outcome of 38 patients in whom renal biopsy showed DMP are reported. They have been subdivided into 2 groups according to the absence (18 patients: group I) or presence (20 patients: group II) of superimposed lesions of focal and segmental sclerosis and/or hyalinosis (FSS/H). Clinical presentation was similar in both groups although patients in group I were less severely affected. Non of the patients of group II responded to corticosteroids, whereas in group I 2/16 responded and 2 infants remitted without treatment. At the latest assessment, 5/18 patients in group I and 10/20 in group II had progressed to terminal renal failure or had impaired renal function. Five patients in group I and 3 in group II were in clinical remission. Eight of 11 repeat biopsies performed in patients of group I showed the development of FSS/H. Thus patients with DMP seem prone to develop lesions of FSS/H. Their course if often worse than that of minimal change with FSS/H since 7 of the 10 patients who developed renal failure did so within 3 years of onset. The finding of DMP in a patient with idiopathic nephrotic syndrome is usually but not invariably an ominous feature.

De novo membranous glomerulonephritis in renal allografts in children.

The incidence of de novo membranous glomerulonephritis (MGN) in transplanted kidneys is around 1 to 2%. In our series, of the 310 grafts that were examined by immunofluorescence microscopy (IF), 29 (9.3%) showed subepithelial IgG deposits, a pattern consistent with the diagnosis of MGN. Transplant biopsy had been performed because of the occurrence of proteinuria in 8 patients (pts), for suspected rejection in 16 and systematically in the remaining 9 who had no proteinuria and a normal renal function. In all cases the lesions were identified by IF and were confirmed by electron microscopy (EM) in 14 pts. Granular deposits of IgG were diffuse in 22 cases and segmental in 7. Sequential specimens were available in 17 pts and showed the persistence or the increase of the IgG deposits in all patients but one in whom they had disappeared. Age at transplantation (Tx) ranged from 2 years 3 months to 16 years. Grafts were from cadaveric donors in 27 pts and from living related donors in 2 pts. In none of the recipients was MGN the nephropathy of the native kidneys. With a follow-up of 18 to 74 months, 6 pts never developed a proteinuria. In the remaining 23, proteinuria developed 1 to 70 months after Tx, associated with a nephrotic syndrome (NS) in 6 pts.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term (15-25 years) outcome of childhood hemolytic-uremic syndrome.

The short-term prognosis of the "typical", "post-enteropathic" form of infantile HUS is usually good, with a complete recovery of renal function. However, the extent of the renal damage observed on some biopsies may raise concern for the long-term prognosis. Therefore, we studied the outcome of 29 patients affected with classical HUS in infancy or early childhood and followed-up for 15-28 years (m = 18 yrs). Initial renal symptoms ranged from a moderate renal failure with normal diuresis to a 12-day anuria: 21 children had to be treated by peritoneal dialysis. Twenty-five patients underwent a renal biopsy shortly after recovery: lesions of glomerular thrombotic microangiopathy (TMA) were found in 14 patients, and patchy cortical necrosis was diagnosed in the other 11. At latest examination 10 patients had no renal abnormality, 12 had residual renal symptoms (hypertension in 7, proteinuria in 4 and midly reduced GFR in 1), 3 were in chronic renal failure (CRF), and 4 had reached end-stage renal failure (ESRF) 16-24 years after onset; 2 of these latter 4 had a normal GFR at 10-year examination. The long-term evolution was not correlated with the initial clinical severity but appeared well correlated with the extent of the histological damage: 10 of the 11 patients with cortical necrosis have either ESRF (4), CRF (3) or renal sequelae (3), and 4 of the 5 patients with TMA involving more than 50% of glomeruli present with moderate sequelae, whereas the 9 patients with TMA involving less than 50% of glomeruli are symptom-free or have mild sequelae. Thus, the risk of renal failure 20 years after a seemingly cured childhood HUS is not negligible, and renal histology is the best indicator of long-term prognosis.