TuBaFrost 2: Standardising tissue collection and quality control procedures for a European virtual frozen tissue bank network

Tumour Bank Networking presents a great challenge for oncological research as in order to carry out large-scale, multi-centre studies with minimal intrinsic bias, each tumour bank in the network must have some fundamental similarities and be using the same standardised and validated procedures. The European Human Frozen Tumour Tissue Bank (TuBaFrost) has responded to this need by the promotion of an integrated platform of tumour banks in Europe. The operational framework for TuBaFrost has drawn upon the best practice of standard workflows and operating procedures employed by members of the TuBaFrost project and key initiatives worldwide.     

TuBaFrost 4: access rules and incentives for a European tumour bank

When designing infrastructure for a networked virtual tumour bank (samples remain at the collector institutes and sample data are collected in a searchable central database), it is apparent that this can only function properly after developing an adequate set of rules for use and access. These rules must include sufficient incentives for the tissue sample collectors to remain active within the network and maintain sufficient sample levels in the local bank. These requirements resulted in a key TuBaFrost rule, stating that the custodianship of the samples remains under the authority of the local collector. As a consequence, the samples and the decision to issue the samples to a requestor are not transferred to a large organisation but instead remain with the collector, thus allowing autonomous negotiation between collector and requestor, potential co-authorship in publications or compensation for collection and processing costs. Furthermore, it realises a streamlined cost effective network, ensuring tissue visibility and accessibility thereby improving the availability of large amounts of samples of highly specific or rare tumour types as well as providing contact opportunities for collaboration between scientists with cutting edge technology and tissue collectors. With this general purpose in mind, the rules and responsibilities for collectors, requestors and central office were generated.     

The pathogenic antigen of Heymann nephritis is a membrane glycoprotein of the renal proximal tubule brush border.

Purified brush border fractions prepared from rat kidneys were solubilized in detergent, iodinated, and subjected to immunoprecipitation to identify the pathogenic antigen present in brush border membranes that is responsible for the production of Heymann nephritis (HN). Purified IgG prepared from the sera of rabbits or rats immunized with a crude cortical preparation, known as Fx1A, precipitated multiple peptides, whereas IgG eluted from glomeruli of rats with active or passive HN specifically immunoprecipitated a single large glycoprotein (Mr = 330,000). This protein (gp330) was subsequently purified by gel filtration and lentil lectin affinity chromatography from detergent-solubilized brush border membranes. When rats were immunized with purified gp330, they developed anti-brush border antibodies and active HN. IgG prepared from the serum of rats with active HN caused passive HN when injected into normal recipients. Rats immunized against brush border membrane proteins depleted of gp330 developed anti-brush border antibodies but did not develop HN. Further analysis of gp330 indicated that it is solubilized by detergent treatment of isolated brush border microvilli, and its antigenic component is released from intact microvilli by trypsin. By immunoperoxidase staining it was localized to the luminal side of the brush border membranes. These results indicate that (i) gp330 is the pathogenic antigen of HN; (ii) the antigen is a glycoprotein of the brush border membrane; and (iii) it is disposed with its pathogenic domain(s) facing the tubule lumen.     

Podocyte flattening and disorder of glomerular basement membrane are associated with splitting of dystroglycan-matrix interaction

The transmembrane component of the dystroglycan complex, a heterodimer of alpha- and beta-dystroglycan, was recently localized at the basal cell membrane domain of podocytes, and it was speculated that it serves as a device of the podocyte for maintaining the complex podocyte foot process architecture, and for regulating the exact position of its ligands, the matrix proteins laminin and agrin, in the glomerular basement membrane (GBM). The redistribution of dystroglycan in two experimental rat models of foot process flattening and proteinuria-i.e., podocyte damage induced by polycationic protamine sulfate perfusion, and reactive oxygen species (ROS)-associated puromycin aminonucleoside nephrosis-was examined. In both experimental diseases, aggregation and reduced density of alpha-dystroglycan by endocytosis by podocytes was observed. In in vitro solid-phase binding assays, protamine and ROS competed with the binding of alpha-dystroglycan with purified laminin and a recombinant C-terminal fragment of agrin that contains the dystroglycan-binding domain. These changes were associated with disorder of the fibrillar components of the lamina rara externa of the GBM, as confirmed quantitatively by fractal analysis. These results indicate that both polycation and ROS induce similar changes in the distribution of podocyte alpha-dystroglycan that involve competitive disruption of alpha-dystroglycan/matrix protein complexes, endocytosis of the liberated receptor by podocytes, and disorganization of the matrix protein arrangement in the lamina rara externa. This links functional damage of the dystroglycan complex with structural changes in the GBM.     

Pathogenetic concepts of membranous glomerulopathy (MGN)

Membranous glomerulopathy (MGN) is a frequent cause for nephrotic syndrome in adults. In this overview, the basic pathogenic features of Heymann nephritis, a "classical" model of MGN in rats, are compared with those of human MGN. While the pathogenic antigen(s) of rat Heymann nephritis (the polyspecific receptor protein gp330/megalin), and that of human MGN (unknown) are obvioulsy different, the results indicate that the molecular mechanisms of proteinuria may be similar in both instances and involve the formation of lipid peroxidation adducts in the glomerular capillary filter. As a consequence, probucol - an efficient inhibitor of lipid peroxidation - drastically reduces proteinuria both in Heymann nephritis and in a large proportion of human patients with MGN.