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

ABSTRACT

OBJECTIVE: It 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. METHODS: Kidney 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. RESULTS: We 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. CONCLUSION: Our 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.