Podocyte Injury Markers And Coagulation Dysfunction In Primary Focal Segmental Glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS), one of the common causes in nephrotic syndrome, is a typical podocytopathy. FSGS is clinically characterized by massive proteinuria, complicated by acute kidney injury and venous thromboembolism, most steroid resistant, progressive renal dysfunction to end stage renal disease. Family FSGS attributes to mutation of genes encoding the molecules of podocyte. However, the pathogenesis of podocyte injury in sporadic FSGS is not yet clear. In addition, hypercoagulability is a risk factor of thrombosis in nephrotic syndrome. Prophylactic anticoagulation in FSGS is a clinical conundrum. Thus, we designed the study in two parts:Part One:Expression of calcineurin in glomeruli of adult patients with primary focal segmental glomerulosclerosisObjective:Calcineurin mediates dephosphorylation of synaptopodin, contributes to disorders of podocyte cytoskeleton, and is probably invovled in the podocyte jury of FSGS. It’s not yet clear whether calcineurin expresses in the glomeruli of human FSGS. This study aimed to observe glumerular expression of calcineurin, which gave us new insights into the pathogenesis of FSGS. Methods:We studied calcineurin expression in renal biopsies with collapsing (COLL, n=6), celluar (CELL, n=13), tip lesion (TIP, n=8), perihilar (HILAR, n=8) and not other specified (NOS, n=11) FSGS variants. Minimal change disesase (n=20) and samples from kidney donor or nephrectomy (n=10) served as normal controls. The correlations between podocyte calcineurin A a isoform (CnAa) expression and the clinicopathological parameters in the FSGS subjects were analyzed. Results:Increased CnAa expression was observed in the podocytes of33FSGS patients and4MCD cases (P<0.05), campared with normal control kidneys. Pocdocyte-specific CnAa scores in the FSGS subgroups and MCD group were NOS2.13(1.25,3.56), CELL1.67(0,3.38), TIP0.58(0,1.92), HILAR0(0,0.75), NOS0.62(0,1.45) and MCD0(0,0.8), respectively. In the FSGS group, podocyte CnAa expression was signifcantly correlated with the degree of proteinuria (rs=0.348, P<0.05). Among nine cases treated with FK506as the second-line therapy, podocyte CnAa staining were positive in six responders but neagative in three nonresponders.Conclusions:Differential CnAa expression in podocytes between FSGS and MCD patients suggests different pathological mechanism between them. Increased CnAa expression in FSGS may be involved in the the development of proteinuria. For FSGS patients with steroid resistance or dependence, positive staining of CnAa in podocytes may be a possible theragnostic marker to use calcineurin inhibitors.Part Two:Differential antithrombin Ⅲ levels in adult focal segmental glomerulosclerosis and membranous nephropathyObjective:To compare plasma and urine antithrombin Ⅲ levels and related facotrs in adult FSGS and membranous nephropathy (MN).Methods:Thirty-three FSGS and thirty-two MN were enrolled. Seventy healthy adult volunteers served as normal controls. Samples were collected before renal biopsy. Plasma and urine ATⅢ concentration were detected by immune rate nephelometry. Plasma ATⅢ activity were determined by chomogenic assay. Factors related to ATⅢ level were analyzed by Person or Spearman methods, followed by multi-linear regression. Results:Proteinuria, serum albumin, creatinine, total cholesterol, urine rentinol binding protein at biopsy in the FSGS group were significantly different from those in the MN group. Compared to the normal controls, plasma ATⅢ concentration and activity in the FSGS group were significantly lower, whereas those in the MN group were not significantly different. Aquired ATⅢ deficiency in concentration and activity were seen in33(90.9%) and25(75.75%) FSGS cases, respectively. Urine ATⅢ concentration increased (>5mg/dl) in8FSGS patients. In the FSGS group, plasma ATⅢ concentration correlated possitively with serum albumin (r=0.735, P<0.01) and negatively with proteinuria (r=-0.533,P<0.01); plasma ATⅢ activity was positively related to serum albumin (r=0.622, P<0.01). Multi-linear regression showed that serum albumin was an independent factor of plasma ATⅢ concentration deficiency in the FSGS group (R2=0.561, P<0.01)Conclusions:Plasma ATⅢ levels in patients nephrotic syndrome was related to the underlying renal diseases. Differential plasma and urinary ATⅢ levels between FSGS and MN patients suggests that the injury mechanism of gomeurlar filtration barrier and renal tubules in FSGS is probably different from that in MN. ATⅢ activity may be helpful to the individual anticoagulation of FSGS patients.