J Korean Soc Pediatr Nephrol.  2010 Oct;14(2):143-153.

The Changes of Slit Diaphragm Molecules After Using Sirolimus

• Choi JY
• Han GD
• Kim YJ
• Park YH

Abstract

PURPOSE
Recently, massive proteinuria has been observed in some transplant patients after switching cyclosporine A (CsA) to sirolimus. To evaluate the pathogenesis of sirolimus-associated proteinuria, we investigated the early changes in slit diaphragm molecules by various administrative conditions of sirolimus and CsA.
METHODS
In vitro-Mouse podocytes were incubated with buffer (C), sirolimus (10 microg/mL) after CsA (10 microg/mL) (C-S), sirolimus only (S) and CsA and sirolimus simultaneously (C+S) for 12, 24, and 48 hours. In vivo-twenty four SPF female Wistar rats were divided into 4 groups buffer (C), sirolimus after 2 weeks of CsA (C-S), sirolimus only (S) and CsA and sirolimus simultaneously (C+S). All groups were treated by intraperitoneal injection every other day for 4 weeks (CsA: 25 mg/kg, sirolimus: 0.5 mg/kg). The changes in mRNA of slit diaphragm molecules were examined by RT-PCR.
RESULTS
The mRNA of nephrin was significantly decreased in group C-S and C+S in vitro. In vivo, the mRNA of nephrin in all groups using sirolimus and the mRNA of podocin in group C-S and C+S were decreased. Microscopically, group C-S and C+S showed small vacuolization and calcification in proximal tubular epithelial cells. Immunohistochemistry using nephrin and podocin antibodies did not show remarkable decrease of staining along the glomerular capillaries. Electron-microscopically, focal fusion of foot processes was seen in group C-S and C+S.
CONCLUSION
This study suggests the decrease of slit diaphragm molecules (nephrin and podocin) in podocyte may be one of the causes of sirolimus associated proteinuria, and podocyte injury by sirolimus may need a primary hit by CsA to develop the proteinuria.

Keyword

Sirolimus; Proteinuria; Cyclosporine; Nephrin

MeSH Terms

Antibodies
Capillaries
Cyclosporine
Diaphragm
Epithelial Cells
Female
Foot
Humans
Immunohistochemistry
Injections, Intraperitoneal
Intracellular Signaling Peptides and Proteins
Membrane Proteins
Podocytes
Proteinuria
Rats, Wistar
RNA, Messenger
Sirolimus
Transplants
Antibodies
Cyclosporine
Intracellular Signaling Peptides and Proteins
Membrane Proteins
RNA, Messenger
Sirolimus