Abstract
BackgroundPodocytes can be the primary site of injury or secondarily involved in various protienuric states. Cross talk between adjacent foot processes and with basement membrane is important for slit diaphragm function. Does expression of podocyte associated proteins in kidney biopsies alter with site/type of primary injury? Genetic mutations of podocin result in steroid resistant FSGS. Can protein expression of podocin predict resistant cases to initiate further genetic evaluation?MethodsAdult patients (n-88) with protienuria- minimal change disease(MCD)-22, focal segmental glomerulosclerosis(FSGS)-21,membranous glomerulonephritis(MGN)-25 and IgA nephropathy(IgAN)-20 were selected for immunohistochemistry with podocin and beta dystroglycan . Results were graded (0 - 3+scale )and compared with control biopsies and internal control. Treatment and follow up (6 months -2 ½ years) of FSGS and MCD cases were collected.ResultsThere was intense to moderate staining of the podocytes with podocin and β dystroglycan in the glomeruli in all cases (MCD, FSGS, IgAN and MGN) except for weak staining with β dystroglycan in 3 cases of MCD. There was loss of immunostains in areas of segmental/global sclerosis. There was no significant difference in the staining pattern between the groups. In primary podocytopathies, staining pattern did not differ between steroid resistant, sensitive or dependent cases.ConclusionsImmunohistochemical expression of podocin and β dystroglycan does not differ in nephropathies which have different site of injury depending on absence (MCD and FSGS) or presence of immune deposits and their localization (MGN and IgAN). Podocin and β dystroglycan staining did not differentiate steroid sensitive and resistant cases, hence, does not give clue to initiate genetic studies. However, analysis of bigger cohort may be required.SummaryPodocin and β dystroglycan immunohistochemistry was done to analyze podocyte - podocyte and podocyte -basement membrane matrix connections in adult protienuric states. Primary podocytopathies i.e. MCD and FSGS and secondary podocytopathy due to immune complex deposition i.e. MGN (subepithelial) and IgAN (mesangial) were analyzed. There was no difference in staining patterns between primary and secondary podocytopathies or between steroid sensitive, resistant and dependent cases of FSGS and MCD.Virtual slidesThe virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/2258608781052786
Highlights
Podocytes can be the primary site of injury or secondarily involved in various protienuric states
Podocyturia as a marker of disease activity has been reported in various protienuric states including focal segmental glomerulosclerosis (FSGS), IgA nephropathy (IgAN) and Membranous glomerulonephritis (MGN) using various podocyte specific proteins [3] but not in Minimal change disease (MCD) [4]
Integrins including α and β dystroglycan which determine the attachment of podocytes to basement membranes have been shown to be reduced in steroid sensitive MCD and suggested to be useful in distinguishing FSGS, MCD and unrepresented FSGS [5,6,7,8]
Summary
Podocytes can be the primary site of injury or secondarily involved in various protienuric states. Does expression of podocyte associated proteins in kidney biopsies alter with site/type of primary injury? Podocytes can be secondarily involved and contribute to protienuria in diseases where primary site of injury is not podocyte e.g. membranous with sub epithelial immune complex deposits and IgAN with dominant mesangial immune deposits [1,2]. Podocyturia as a marker of disease activity has been reported in various protienuric states including FSGS, IgAN and MGN using various podocyte specific proteins [3] but not in MCD [4]. Podocin being specific marker to identify podocytes in studies conducted for podocyturia, it might be worthwhile to study its expression in kidney biopsy in these protienuric states
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