Role of progenitor cell marker CD133 in supporting diagnosis of collapsing glomerulopathy

Abstract

Purpose: A previous immunofluorescent study suggests that, in collapsing glomerulopathy, most hyperplastic podocytes that stained positively for a progenitor cell marker CD133 are derived from CD133 + parietal epithelial cells. In pathology practice, not all renal biopsies with collapsing glomerulopathy show the typical morphologic features for this entity, which include florid podocyte hyperplasia, collapsing glomerular capillary loops, and cystic tubular dilation. This study was made to determine if CD133 staining using an immunohistochemical method can be used to confirm hyperplastic podocytes and identify extensive acute tubular injury in collapsing glomerulopathy.

Methods: Twenty-one collapsing glomerulopathy biopsies were stained for CD133 and compared with 15 biopsies with focal segmental glomerulosclerosis, not otherwise specified (FSGS).

Results: All patients with collapsing glomerulopathy were of African American descent with prominent renal failure and nephrotic range proteinuria. In contrast, the FSGS group consisted of patients from a variety of ethnic backgrounds with nephrotic range proteinuria but relatively low serum creatinine. The striking finding was that all collapsing glomerulopathy cases showed positive CD133 staining in the clusters of hyperplastic podocytes. There was significantly higher CD133-positive staining rate for hyperplastic podocytes (38%) in the glomeruli of the collapsing glomerulopathy group when compared to small clusters of hyperplastic podocytes in the FSGS group (8%). In addition, when compared to the relatively weak CD133 staining in the proximal tubules of the FSGS group, the proximal tubules of the collapsing glomerulopathy group all showed diffuse and strong CD133 staining as a feature of severe acute tubular injury, which corresponded to the high serum creatinine levels in these patients.

Conclusion: Our data indicate that the combination of the distinctive mosaic CD133 staining in hyperplastic podocytes and the diffuse tubular CD133 staining is helpful in supporting a diagnosis of collapsing glomerulopathy.

Keywords: Acute tubular injury; CD133; Collapsing glomerulopathy; Focal segmental glomerulosclerosis; Parietal epithelium; Progenitor cells; Proliferative podocytes.

Fig. 1

CD133 expression in negative control, FSGS, and collapsing glomerulopathy. A CD133 was expressed in normal parietal epithelial cells along the Bowman’s capsule but not in podocytes. B In most FSGS, parietal epithelial cells also stained positive for CD133, but podocytes were negative for this staining. C Occasionally, CD133 were positive in a small cluster of immature podocytes of FSGS (white arrow). In collapsing glomerulopathy (D, E and F), there was a range of CD133-positive staining in the proliferative podocytes that was most characterized with a mosaic pattern intermingled with collapsed glomerular tufts (wide base blue arrows). Magnifications at × 600 in A–F

Fig. 2

CD133 and PAS dual stains in negative control, FSGS, and collapsing glomerulopathy. A PAS-stained delicate glomerular capillary loops with minimal mesangial cells. The parietal epithelium stained positively for CD133 while podocytes were negative for CD133 staining. B Occasional cluster of CD133-positive immature podocytes was seen in a few FSGS cases (white arrow). In collapsing glomerulopathy, CD133 highlighted florid immature podocytes in C and D (indicated by wide base blue arrows). Magnifications at × 600 in A–D

Fig. 3

Hematoxylin/eosin staining, and immune stains for Ki-67 (proliferative marker) and WT-1 (podocyte marker) in negative control glomeruli and glomeruli with hyperplastic podocytes. Negative control glomeruli with A hematoxylin/eosin staining, B negative Ki-67 staining and C positive WT-1 staining in podocytes. Hyperplastic podocytes with hematoxylin/eosin staining (D and G), positive Ki-67 staining (E and H) and negative WT-1 staining (F and I) from two collapsing glomerulopathy cases. Magnification × 600 in A–L

Fig. 4

CD133 in the normal proximal tubules and the proximal tubules with early tubular injury. A In normal proximal tubules, the CD133-positive progenitor cells were located at the niches of tubular turning segments (with PAS-positive tubular basement membranes showing invagination), which were not covered by PAS staining on their surfaces (green arrows). The remaining proximal tubular epithelial cells were negative for CD133 staining but were covered by PAS-positive brush borders. B At the early stage of acute tubular injury, CD133-positive cells extended the signals to the surrounding cells clustered in groups of two or three cells (orange arrows), which were also negative for dual-PAS staining on the surface. Magnifications at × 600 for A, B

Fig. 5

Grading CD133 and PAS in acute tubular injury. A CD133 staining was graded as 0 in normal proximal tubules with intact brush border staining by PAS. B Mild scattered CD133 staining was graded as 1 + with mild reduced PAS staining. C Darker CD133 staining in more proximal tubules was graded as 2 + . D Strong and diffuse CD133 staining in a collapsing glomerulopathy was graded as 3 + . Magnifications at × 600 for A–D

Fig. 6

Receiver operative characteristics (ROC) curve with analysis of area under the curve (AUC) for the performance of CD133 staining based on a range of serum creatinine levels in all three groups. The overall cases had an AUC of 0.93 (very good category)

Fig. 7

Schematic comparison of normal nephron and collapsing glomerulopathy. A Normal glomerulus have orange-colored CD133-positive parietal epithelial cells with CD133-negative podocytes and scattered CD133-positive progenitor cells at the tip of the less curvature of the turning proximal tubules. B In collapsing glomerulopathy, the orange-colored CD133-positive podocytes are clustered outside of the collapsed glomerular tufts and CD133 staining also shows diffuse expression in dilated and flat proximal tubular epithelial cells, indicating severe tubular injury