Douglas G. Matsell

IGF-Binding Protein mRNAs in the Human Fetus: Tissue and Cellular Distribution of Developmental Expression

Insulin-like growth factors (IGF-I and IGF-II) are synthesized by most embryonic and fetal tissues, and regulate cellular growth and differentiation as autocrine/paracrine factors. A family of six IGF-binding proteins (IGFBPs) modulate IGF biological actions as both negative (inhibitory) and positive (potentiating) modulators. To determine the tissue distribution of IGFBP mRNA expression, we performed Northern blot analysis and in situ hybridization of human fetal tissues during gestational ages 10-16 weeks (n = 8). IGFBP-1 mRNA was expressed only in the liver, whereas other IGFBP mRNAs were expressed in variable abundance in every tissue examined. IGFBP-2 mRNA was expressed in moderate abundance in every tissue with the highest level observed in the liver; IGFBP-3 mRNA was expressed most abundantly in the skin, muscle and heart; IGFBP-4 mRNA was expressed in moderate abundance equally in all tissues; IGFBP-5 mRNA was expressed most abundantly in the skin, muscle and stomach, and IGFBP-6 mRNA was expressed in low abundance in all tissues. Notable exceptions were that liver expressed little or no IGFBP-4, -5 and -6 mRNAs, spleen and thymus expressed low levels of IGFBP-5 mRNA, and brain expressed little or no IGFBP-5 and IGFBP-6 mRNA. In situ hybridization of human fetal tissues showed IGFBP mRNAs were expressed in both epithelial and mesenchymal cells depending on the specific IGFBP and the stage of development. IGFBP-3, -4, and -5 mRNAs were localized mainly in the mesenchymal cells, and IGFBP-2 mRNA was localized predominantly in the epithelial cells. IGFBP-6 mRNA was localized in low abundance in both epithelial and mesenchymal cells. These studies indicate that IGFBPs are important paracrine modulators of IGF action on cellular growth and differentiation, by modulating IGF-dependent or IGF-independent actions.

Experimental models of fetal obstructive nephropathy

Abstract. Urinary tract obstruction in the developing human fetus is an important cause of postnatal kidney failure and is the most common cause of end-stage renal disease and chronic renal failure in boys less than 4 years of age. Although the pathogenesis of renal dysplasia resulting from urinary tract obstruction is not well defined, it is clear that the earlier the obstruction occurs during in utero nephrogenesis the more severe the histopathological changes. Efforts to intervene in the human fetus have been hampered by an inaccuracy of diagnosis and by a lack of validation of in utero features predictive of poor outcome. A number of experimental models of obstructive renal dysplasia have been developed, which result in the consistent histopathological features of tubular cell apoptosis, mesenchymal expansion with mesenchymal myocyte transformation, and decreased glomerular endowment and glomerular injury. Defining the optimal timing of release of obstruction and restoring normal developmental gene and protein patterns should guide future intervention in these processes. Experimental animal models that closely simulate human development and disease will, thus, be essential for exploring these questions, and for assessing novel fetal therapies for future human application.

Escherichia coli verotoxin binding to human paediatric glomerular mesangial cells

Haemolytic uraemic syndrome (HUS) remains the leading cause of acute renal failure in children. Although anEscherichia coli-produced verotoxin (VT) has been implicated in the pathogenesis of HUS, the precise mechanisms of disease are not well defined. We hypothesise that the pathogenesis of renal failure in HUS includes the binding ofE. coli VT to the glomerular mesangial cell, with consequent effects on renal function. Using human paediatric mesangial cells. we studied the binding and biological effects of the purified verotoxin VT-1. We isolated, purified and characterised paediatric glomerular mesangial cells. The mesangial cells were characterised by their immunoreactivity with both smooth muscle actin and vimentin antibodies, and lack of immunoreactivity with cytokeratin or factor VIII antibodies. Using an fluorescein isothiocyanate-conjugated VT (10−7–10−8 M), we demonstrated specific binding to the mesangial cell membrane by immunofluorescence microscopy. We also demonstrated a dose-dependent inhibition of mesangial cell mitogenesis at concentrations from 10−9 to 10−17 M. Our data demonstrate that VT-1 binds to paediatric human glomerular mesangial cells and this binding results in specific biological actions, including an inhibition of cell mitogenesis.

Arteriovenous fistula after biopsy of renal transplant kidney: diagnosis and treatment

An 11-year-old renal transplant recipient was noted to have a bruit over her transplant graft 26 months post transplant and 17 months following percutaneous renal biopsy during an episode of rejection. Diagnosis of an arteriovenous (AV) fistula was made by ultrasound examination with Doppler flow and was confirmed with arteriography. The AV fistula was occluded by transcatheter embolotherapy with placement of a steel coil into the fistula from the renal vein approach. This procedure allowed nonsurgical closure of the AV shunt without significant change in renal function.

Risk of hypertension and reduced kidney function after acute gastroenteritis from bacteria-contaminated drinking water

Background: The long-term health consequences of acute bacterial gastroenteritis remain uncertain. We studied the risk of hypertension and reduced kidney function after an outbreak of acute gastroenteritis due to contamination of a regional drinking water supply with Escherichia coli O157:H7 and Campylobacter species. Methods: A total of 1958 adults with no known history of hypertension or kidney disease before the outbreak participated in a long-term follow-up study. Of the participants, 675 had been asymptomatic during the outbreak, 909 had had moderate symptoms of acute self-limited gastroenteritis, and 374 had had severe symptoms that necessitated medical attention. The outcomes of interest were a diagnosis of hypertension or the presence of reduced kidney function and albuminuria during the follow-up period. Results: After a mean follow-up of 3.7 years after the outbreak, hypertension was diagnosed in 27.0% of participants who had been asymptomatic during the outbreak and in 32.3% and 35.9% of those who had had moderate and severe symptoms of acute gastroenteritis respectively (trend p = 0.009). Compared with the asymptomatic participants, those with moderate and severe symptoms of gastroenteritis had an adjusted relative risk of hypertension of 1.15 (95% confidence interval [CI] 0.97–1.35) and 1.28 (95% CI 1.04–1.56) respectively. A similar graded association was seen for reduced kidney function, defined as the presence of an estimated glomerular filtration rate below 60 mL/min per 1.73 m2 (trend p = 0.03). No association was observed between gastroenteritis and the subsequent risk of albuminuria. Interpretation: Acute bacterial gastroenteritis necessitating medical attention was associated with an increased risk of hypertension and reduced kidney function 4 years after infection. Maintaining safe drinking water remains essential to human health, as transient bacterial contaminations may have implications well beyond a period of acute self-limited illness.

Renal dysplasia: New approaches to an old problem

Renal dysplasia is a clinically important consequence of abnormal nephrogenesis. Various forms are encountered in clinical practice; however, renal dysplasia may represent the final common end point of defects in the normal cascade of fetal kidney development. Typical histopathologic changes characterize renal dysplasia, including architectural distortion, metaplasia, and primitive glomeruli and tubules. Cystic changes are not universal but can be found in most situations. The advent of recent molecular techniques, including gene targeting and positional cloning, has expanded our knowledge of the molecular control of normal mammalian nephrogenesis and with it our understanding of the pathogenesis of renal dysplasia. A defect in the ability of the branching ureteric duct and the undifferentiated metanephric blastema to communicate appears to be the basic underlying principle for the formation of dysplasia. Mutation, defective regulation of transcription, and alteration in spatial or temporal expression of a number of classes of genes, including growth factors, have been implicated in the development of renal dysplasia. Numerous examples, both experimental and in nature, highlight this point.

Plasma Terminal Complement Complexes in Acute Poststreptococcal Glomerulonephritis

In most instances of acute poststreptococcal glomerulonephritis (APSGN), activation of the complement system occurs, as reflected by decreased levels of the complement proteins C3, C5, and properdin (P). Recent studies implicate terminal complement complexes (TCC) in the pathogenesis of glomerular injury. The fluid phase TCC, SC5b-9, reflects the formation of membrane-bound C5b-9 and has been used as a clinical marker in various diseases. Plasma concentrations of SC5b-9 were measured with an enzyme immunoassay using a monoclonal antibody to a neoantigen expressed on the SC5b-9 complex in 13 children who presented with clinical and pathologic features of APSGN. SC5b-9 was significantly elevated in all plasmas obtained within 30 days after onset of clinical glomerulonephritis. Concentrations of SC5b-9 in acute plasmas were significantly higher than those of paired convalescent samples. For individual patients, as SC5b-9 concentration returned to normal there was a coincident decrease in serum creatinine concentration and urinary protein excretion, signifying clinical improvement in glomerulonephritis. Thus, TCC generation commonly occurs in the early stages of APSGN and may be of importance in the pathogenesis of the condition.

The Role of I and B in Peritonitis Associated with the Nephrotic Syndrome of Childhood

ABSTRACT: Children with nephrotic syndrome (NS) are susceptible to bacterial infections, including primary bacterial peritonitis. Immunologic abnormalities associated with NS include low serum levels of the complement proteins I and B of the alternative complement pathway. We developed a novel and highly sensitive enzyme immunoassay using murine MAb to I and B to quantitate urinary concentrations of these proteins. We studied 22 patients with minimal change NS, including seven with a history of peritonitis (1.6 ± 0.3 episodes, mean ± SEM) and 15 without such a history. The two groups did not differ significantly in age, sex, race, age at onset of disease, or duration of disease. Children with minimal change NS complicated by peritonitis had 1) increased urinary excretion of both I (p > < 0.05) and B (p < 0.05) in relapse versus remission, 2) greater excretion of I in both relapse (p < 0.01) and remission (p < 0.05) compared with patients without peritonitis, 3) greater excretion of B in relapse compared with patients without peritonitis (p < 0.05), and 4) decreased plasma levels of I compared with patients without peritonitis and controls (p < 0.01) and decreased plasma levels of B compared with controls. Increased urinary excretion of I correlated with decreased plasma levels of I (r = 0.88, p < 0.001). These data support our initial hypothesis that depressed plasma concentrations of these proteins of the alternative complement pathway may predispose patients with minimal change NS to peritonitis and that urinary loss of these proteins is a tenable mechanism.

Evaluation of metanephric maturation in a human fetal kidney explant model

SummaryWe have developed a unique human fetal kidney explant model to study the role of the insulinlike growth factor (IGF) system in metanephric development. Kidneys from 10–18 wk gestation human abortuses were maintained in serum-free conditions and defined medium, which was shown to support the induction and differentiation of the viable metanephric blastema. Histologically the tissue remained viable to 192 h of serum-free culture, while metanephric differentiation, reflected by a shrinking nephrogenic zone and the formation of maturing S-shape and glomerular forms, was accelerated and occurred between 48 and 96 h. In the nephrogenic zone, a significant decrease in IGF-II gene expression occurred, which reflected the differentiation of the metanephric blastema cell mass. IGF-II expression persisted, however, in the expanded interstitial mesenchyme. With differentiation over 48 h an increase in IGFBP-2 and WT1 gene expression by Northern blot analysis occurred, and was localized by in situ hybridization to the differentiating glomerular epithelial cell mass. Analysis of the explant-conditioned media by Western ligand blot demonstrated an increase in the rate of IGF binding protein (IGFBP)-2 peptide production by the differentiating explant, consistent with an increase in IGFBP-2 gene expression and with metanephric differentiation. This pattern of temporal and spatial gene expression closely approximates that of normal in vivo fetal renal development and of glomerular epithelial cell differentiation.

Terminal complement complexes in acute poststreptococcal glomerulonephritis

Activation of the complement cascade occurs in most cases of acute poststreptococcal glomerulonephritis (APSGN) and results in the formation of the terminal complement complexes (TCC). To examine the possible role of TCC in the pathogenesis of glomerular injury in APSGN, we studied 30 patients with the clinical diagnosis of APSGN. All patients had an elevated plasma SC5b-9 concentration at the onset of clinical nephritis. Serial plasma concentrations showed an inverse linear relationship with time after onset of clinical disease (r=−0.59,P=0.0008), while plasma C3 concentrations showed a positive linear relationship (r=0.78,P=0.0001). Renal biopsies of 5 patients demonstrated co-localization of C5b-9, S-protein, and C3 deposition in a glomerular capillary loop and mesangial distribution. Urinary excretion of TCC in the acute phase of APSGN was not elevated and was not a useful marker of disease activity. These data suggest that in APSGN with terminal complement pathway activation the local generation of TCC may contribute to the pathogenesis of the disease.