Kidney Week

Abstract: SA-PO226

Nephrin Is Necessary for Podocyte Recovery Following Injury in an Adult Mature Glomerulus

Session Information

• Glomerular: Cell Biology
  November 04, 2017 | Location: Hall H, Morial Convention Center
  Abstract Time: 10:00 AM - 10:00 AM

Category: Glomerular

• 1003 Glomerular: Cell Biology

Authors

• Verma, Rakesh, University of Michigan, Ann Arbor, Michigan, United States

Rakesh Verma,

• Venkatareddy, Madhusudan M., University of Michigan, Ann Arbor, Michigan, United States

Madhusudan M. Venkatareddy,

• Li, Theodore Zhuo, University of Michigan, Ann Arbor, Michigan, United States

Theodore Zhuo Li,

• Patel, Sanjeevkumar R., University of Michigan, Ann Arbor, Michigan, United States

Sanjeevkumar R. Patel,

• Garg, Puneet, University of Michigan, Ann Arbor, Michigan, United States

Puneet Garg,

Background

Nephrin (Nphs1) is an adhesion protein and is expressed at the podocyte intercellular junction in the glomerulus. Nphs1 mutations in humans or deletion in animal genetic models results in a developmental failure of foot process formation. Though nephrin is essential for foot process (FP) development, its role following development is not well defined. In order to understand the role of nephrin following developent we initially generated a nephrin flox mouse. Using this mouse we were able to delete nephrin in an inducible manner using tamoxifen (Nphs1^Tam-Cre) .

Methods

Mice with podocyte specific deletion of nephrin were generated by breeding Nphs1^fl/fl mice with NPHS2-Cre and tamoxifen-inducible (NPHS2-Cre) mice. We used biochemical and cell biology techniques to assess nephrin expression in the glomeurlus. Protamine sulfate (PS) and nephrotoxic serum (NTS) were used to study the role of nephrin following injury and in recovery.

Results

Deletion of nephrin using Nphs2-Cre resulted in FP spreading and proteinuria by 10-12 d following birth. Nephrin expression decreased by 85% at 10 days post-induction with tamoxifen. The Nphs1^Tam-Cre mice had normal FP ultrastructure and intact filtration barrier upto 4-6 weeks post-induction. Interestingly, nephrin expression persisted at the slit diaphragm upto 16-20 wks post-tamoxifen. Nphs1^Tam-Cre mice developed proteinuria 8 wks following induction along with FP structural changes. Nphs1^Tam-Cre mice 2 wks post induction subjected to PS model of podocyte injury, demonstrated failure of recovery following heparin sulfate. Similarly, Nphs1^Tam-Cre mice failed to recover following NTS with persistence of proteinuria and FP effacement.

Conclusion

As in development nephrin is necessary for maintenance of a healthy glomerular filter. Interestingly, nephrin expression persists for several months following deletion. The small fraction of nephrin that remains is relatively stable and is sufficient to maintain the junction for 4-6 wks. It is likely that some nephrin is either recycled continously at the membrane or is stably linked to actin. Following injury, recovery requires larger amount of nephrin as evident by failure of recovery following PS and NTS injury. This would suggest that induction or maintanence of nephrin expression would be benefical to prevent proteinuric kidney diseases.

Funding

• NIDDK Support