Quantitative Analysis of Glomerular Type IV Collagen Alpha3–5 Chain Expression in Children with Thin Basement Membrane Disease

Abstract

Thin basement membrane disease (TBMD) and Alport syndrome, two forms of childhood nephritis, have generally been considered to be hereditary diseases. In Alport syndrome, several reports have demonstrated pathogenic mutations of the genes encoding type IV collagen α3, 4 and/or 5 chain [α3, 4 and/or 5(IV)]. Previous immunohistochemical studies indicated that these antigens were absent from the glomerular basement membrane (GBM) in Alport syndrome, whilst a normal labeling pattern was maintained in TBMD. In order to understand the role of the α3, 4 and/or 5(IV) antigens in TBMD, we used confocal laser scanning microscopy (CLSM) to examine cryosections of renal biopsies from 12 children with TBMD and 11 control children with IgA nephropathy (IgAN) without proteinuria. All tissue sections were stained with a mixture of FITC-conjugated rat monoclonal antibodies directed against human α3(IV), α4(IV) or α5(IV) and a Texas red-conjugated rat monoclonal antibody raised against human α2(IV). CLSM was performed and quantitative analysis of the ratio of the staining signal for α3(IV), α4(IV) or α5(IV) to α2(IV) [α3(IV), α4(IV) or α5(IV)/α2(IV)] along the GBM was determined. The average number of pixels for α3(IV), α4(IV) or α5(IV)/α2(IV) was 3.52 ± 1.49, 3.54 ± 1.25 and 1.09 ± 0.49 in TBMD and 3.62 ± 1.46, 3.99 ± 1.53 and 1.77 ± 0.47 in control subjects, respectively. Statistical analysis indicated that α5(IV)/α2(IV) ratio was significantly lower (p < 0.01) in children with TBMD compared to controls. These findings raise the possibility that TBMD might be caused by an abnormality of the α5(IV) antigen along the GBM.

Progress in Pathogenesis of Proteinuria

“…If the gene encoding α 4 chain is mutated, “thin basement membrane disease” can occur, which is characterized by hematuria under the microscope and is also known as “benign familial hematuria.” When autologous antibodies are present in the NCI structural region of the anticollagen type IV α 3 chain, the GBM mechanical barrier is disrupted and produces massive proteinuria. This is clinically referred to as “Goodpasture syndrome” [14–16]. …”

Difficulties in differentiating thin basement membrane disease from Alport syndrome

“…In some cases of thin basement membrane disease, ontheotherhand,theremayoccuralooseningofthe structureandevenaduplicationofthelaminadensa. Theaboveexamplesshowthatthedifferentiation ofthesetwodiseasescanbedifficult.Thisdifficulty wasoneofthereasonstostartlookingfordifferences in genetic research [9,10,11,12,13,14,15,16,17,18,19]. The first were Habib et al [9].…”

“…The first were Habib et al [9]. They werefollowedbyotherresearchers:Aaronset al [10], Langet al [11],Lamprechtet al [12],Lemminket al [13],Pigneraset al [14],andothers [15,16,17,18,19,20,21,22,23,24].Itwasestablishedthatboth diseases are accompanied by mutations in the CO-L4A3/COL4A4genes.However,basedontheavailable results of the research on the mutations in the COL4A3/COL4A4genes,nocleardiagnosticcriteria could be defined in order to distinguish thin basementmembranedisease,autosomaldominantAlport syndromeandautosomalrecessiveAlportsyndrome. Ofdiagnosticimportanceisthelackofreactionwith anti chains α3, α4 and α5 collagen type IV in the basementmembranesofrenalglomeruliandtubules (and the lack of reaction from the anti-α5 chain in theskin).…”

Discordance between skin biopsy and kidney biopsy in an X-linked carrier of Alport syndrome

“…Immunofluorescence staining of the α3(IV) and α5(IV) chains in the kidney biopsy showed continuous basement membrane staining, but α5(IV) staining was weaker than usual (Fig. 1c,d), which has been shown in TBMN [8]. After a careful review, subtle foci of diminished staining for α5(IV) were seen in the GBM and Bowman's capsule (Fig.…”