Histochemical study for apolipoprotein abnormalities in lipoprotein glomerulopathy

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We clarified using immunoelectron microscopy and serial observations with electron microscopy and lipid stain as well as routine histology that specific apolipoprotein (apo) E variants are involved in the formation of intraglomerular lipoprotein thrombi in cases of lipoprotein glomerulopathy (LPG) and its experimental model. In addition, we investigated the relationship between sizes of particles in lipoprotein thrombi and lipoprotein profile in plasma.1. We use biopsy specimens from cases of LPG having apoE-Sendai(Arg145Pro), apoE with 18 amino acid deletion and apoE-Tokyo with 3 amino acid deletion, respectively. We also investigated histochemistry of a LPG model induced by the injection of apoE-Sendai virus into apoE-deficient mice.2. We applied immunoperoxidase study with anti-human apoE antibody to snap-frozen sections of biopsy specimens and mouse kidney portions, and embedded the sections in Epon 812 by the handstand-embedding method for electron microscopic observation. Positive stain of apoE were seen around lipid granules in the intraglomerular lipoprotein thrombi of both human and experimental LPG.3. To define the characteristics of particles in lipoprotein thrombi, serial sections of Epon-embedded blocks were observed with electron microscopy and Sudan-IV stain. The results showed that lipoprotein thrombi mainly included triglycerides, which were composed of unsaturated fatty acids. The findings in experimental LPG were enhanced by incubation in p-phenylenediamine during Epon-embedding.4. We examined the mean diameters of intraglomerular lipid particles under electron microscopy and compared with lipoprotein profile in plasma. The diameters were significantly correlated with triglycerides/cholesterol ratios in whole plasma and in HDL fraction (r=-0.80, p<0.01) but not in VLDL or LDL.In addition, the cases showing smaller lipid granules and higher TG/Chol ratios in plasma and in HDL were nephrotic or became nephrotic within 6 months.