The assay of laminin fragments in serum and urine as an indicator of renal damage induced by toxins

Serum laminin as a marker of diabetic retinopathy development: a 4-year follow-up study

PURPOSE

The usefulness of laminin as a serum marker of diabetic retinopathy is a topic that generates conflicting views. The aim of the present study was to investigate the effect of diabetic retinopathy on serum laminin-P1, the larger pepsin resistant fragment of laminin, and to elucidate whether serum laminin-P1 could be an indicator of the risk for development of diabetic retinopathy.

METHODS

In a prospective study, 97 consecutive diabetic patients (35 type 1 and 62 type 2) without diabetic retinopathy and a urinary albumin excretion rate lower than 20 microg per minute were enrolled in a 4-year follow-up study. Patients who developed microalbuminuria during the study were excluded in order to avoid the influence of diabetic nephropathy on serum laminin-P1. At the end of follow-up, data from ophthalmologic studies and serum laminin-P1 were evaluated in the 66 normoalbuminuric diabetic patients who completed the study.

RESULTS

No statistical differences were observed in baseline laminin-P1 serum concentrations between patients who developed diabetic retinopathy (n = 15) and patients who remained without it during follow-up (n = 51). However, serum laminin-P1 levels obtained at the end of the study were significantly higher in patients who developed diabetic retinopathy (1.75 +/- 0.33 U/ml versus 1.47 +/- 0. 27 U/ml; P =.002). Furthermore, statistical difference was observed when initial and final values of serum laminin-P1 were compared in patients who developed diabetic retinopathy (1.56 +/- 0.27 U/ml versus 1.75 +/- 0.33 U/ml; P =.001). Remarkably, an increase in serum laminin-P1 concentration was detected in all but two of the patients who developed diabetic retinopathy. The relative risk of development of diabetic retinopathy in patients who showed an increase in serum laminin-P1 during follow-up was 5.4 (95% confidence interval, 1.32 to 22.13).

CONCLUSIONS

Serum laminin-P1 is a marker and a risk indicator of diabetic retinopathy but is not an early predictor of its development.

Presence of laminin fragments in cyst fluid from patients with autosomal dominant polycystic kidney disease (ADPKD): role in proliferation of tubular epithelial cells

Cyst fluid samples obtained from eight patients with autosomal dominant polycystic kidney disease (ADPKD) were analysed for the presence of the basement membrane component laminin and its breakdown products, using ELISA and immunoblotting techniques. Whole laminin was not detected, whereas laminin fragments of 270, 155, 87, 56, and 14 kDa were detected at a mean total value of approximately 0.5 microgram/ml. The laminin fragments were assessed for their effect on cultured normal and ADPKD epithelial cells. Both cell types showed accelerated growth under these conditions. These findings suggest that basement membrane degradative fragments present in cyst fluid may contribute to cystic epithelial cell proliferation and may therefore be important in the pathogenesis of ADPKD.

A rapid and sensitive enzyme linked immunofilter assay (ELIFA) for whole bacterial cells

An improved method is described for the detection of Escherichia coli by an enzyme linked immunofilter assay (ELIFA) using nitrocellulose membrane sandwiched between two 96-well plates. The incorporation of a pumping system permits a continuous flow of reagents and/or wash fluids through the membrane and provides an assay procedure capable of detecting 10(3) bacteria per well within 40 min. Quantitative bacterial detection was based on precipitated chromogen determined by scanning densitometry. The procedure represents a significant improvement in assay time and/or sensitivity over previously described ELIFA and ELISA methods for whole bacterial cells.

Isolation of pepsin-resistant laminin fragments from human placenta: effect on epithelial cells cultured from the kidneys of patients with autosomal dominant polycystic kidney disease (ADPKD)

Laminin isolated from human placenta was subjected to prolonged pepsin digestion. Seven peptide fragments (designated N1 to N7) were separated by ion-exchange chromatography and gel filtration and characterised by SDS-polyacrylamide gel electrophoresis and immunoblotting. The molecular size of the laminin fragments varied from approx. 900,000 (N1) to 28,000 (N7). Epithelial cells obtained from normal kidneys and patients with autosomal dominant polycystic kidney disease (ADPKD) were cultured. The incorporation of [3H]thymidine was measured over 96 h to determine the effect of the addition of the different fragments and whole laminin from EHS tumour to the cells. The rate of growth of both normal and polycystic cells was increased in the presence of the laminin fragments but this effect was more pronounced in the ADPKD cells.