Abstract
The pathological diagnosis of renal needle biopsy specimens requires the use of various analytical methods, including the use of various special stains, immunofluorescence, immunohistochemistry, and transmission electron microscopy (TEM). Inevitably, there are many cases wherein it is difficult to make a definitive diagnosis because of insufficient materials, especially for TEM. To compensate for this, low-vacuum scanning electron microscopy (LVSEM) imaging using formalin-fixed paraffin-embedded (FFPE) specimens is being tested as a possible diagnostic tool for kidney biopsy. Here, we report a new LVSEM imaging technique using metal-sensitized immunohistochemistry. We performed immunohistochemistry on FFPE samples of kidney tissue to detect CD31 and CD34, which are used as vascular endothelial markers. We then sensitized 3,3'-diaminobenzidine (DAB) with AuCl. We also performed platinum blue and thiosemicarbazide-periodic acid-methenamine silver (TSC-PAM) staining for the control of LVSEM imaging as previously reported. LVSEM imaging of CD31 and CD34 clearly visualized glomerular endothelial cells (GECs), the peritubular capillary network, and small arteries, which are difficult to identify in the case of platinum blue or TSC-PAM staining, suggesting that LVSEM imaging can be useful in the assessment of inflammatory disease and tumor invasion. In conclusion, we established a new LVSEM imaging technique for kidney endothelium, and the AuCl sensitization of DAB can be applied to any type of immunohistochemistry to observe microstructures as well as to confirm the deposition of immune complexes in renal biopsy specimens.
