Relation of peritubular capillary features to class of lupus nephritis

BACKGROUND Experimental studies have linked peritubular capillary (PTC) loss with progression of chronic kidney disease. Minimal information on PTC in lupus nephritis (LN) has been reported. We therefore evaluated the PTC area in different classes of LN and determined if specific clinical characteristics correlated with PTC changes. METHODS Renal biopsies of 253 subjects with LN (categorized using the ISN/RPS 2003 classification) and 13 normal renal donors (the controls) were retrospectively evaluated for PTC morphology by staining for CD31 with immunohistochemistry method. The percent positive area of PTC (% PTC) was correlated with serum and urinary measures of renal function and renal pathology. RESULTS Significant PTC loss was observed in all classes of LN compared to controls. The % PTC area was highest in controls (7.64±1.48 %) with levels of 1.95±1.50, 4.16±3.85, 4.19±4.45, 5.02±1.79, and 4.45±3.75 in classes II, III, IV, IV combined with V and V, respectively (all p values < 0.05). The lowest PTC density was observed in class II LN, but this may be because some cases with worse classes of LN showed increased PTC density due to abnormally dilated capillaries associated with acute inflammation and angiogenesis. %PTC was increased in those with hematuria (5.8±5.2 vs. 3.6±3.4 %, red blood cells 3-10 vs. < 3 cells/high power field, p < 0.05) and was reduced in those with a moderately declined renal function (3.29±3.40 vs. 4.42±4.12, eGFR 15-59 vs. ≥ 60 ml/min/1.73 m2, p < 0.05). Nephrotic-range proteinuria also trended to be associated with lower PTC density although it did not reach statistical significance (3.1±2.6 vs. 4.9±4.5, p= 0.067). CONCLUSIONS LN is associated with PTC loss and the severity correlates with reduced renal function. Further studies are needed to investigate whether a loss of PTC can predict long term renal outcomes in LN.