The Importance of Sphingomyelin Phosphodiesterase Acid-Like 3b (SMPDL-3b) Levels in Kidney Biopsy Specimens of Children With Nephrotic Syndrome

Abstract

ObjectiveIt remains unclear whether the low amount of SMPDL-3b required for rituximab binding is the cause of treatment resistance in patients with treatment-resistant nephrotic syndrome with advanced podocyte injury. Given the limited number of studies on the relationship between rituximab and SMPDL-3b, this study was conducted to assess whether SMPDL-3b levels in pretreatment renal biopsy specimens can be used to predict the clinical effectiveness of immunosuppressive drugs, especially rituximab, in children with nephrotic syndrome.MethodsKidney biopsy specimens from 44 patients diagnosed with idiopatic nephrotic syndrome were analyzed using immunohistochemical staining with an anti-SMPDL-3b antibody and real-time polymerase chain reaction (PCR) for SMPDL-3b mRNA expression.ResultsWe showed that SMPDL-3b mRNA expression and anti-SMPDL-3b antibody staining did not differ significantly between the patient groups with different responses to immunosuppressive therapies.ConclusionOur results suggest that SMPDL-3b may actually be an indicator of disease progression rather than a marker for predicting response to a particular immunosuppressive agent.