Kidney Week

Abstract: FR-PO845

Proteomics of Microdissected Glomeruli and Tubulointerstitium Reveals Compartment-Specific Alterations in the Extracellular Matrix of Kidney Allografts with Antibody-Mediated Rejection

Session Information

• Transplantation: Basic
  October 26, 2018 | Location: Exhibit Hall, San Diego Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Transplantation

• 1801 Transplantation: Basic

Authors

• Clotet-Freixas, Sergi, University Health Network, Toronto, Toronto, Ontario, Canada

Sergi Clotet-Freixas,

• McEvoy, Caitriona M., University Health Network, Toronto, Toronto, Ontario, Canada

Caitriona M. McEvoy,

• Batruch, Ihor, Mount Sinai Hospital, Toronto, Ontario, Canada

Ihor Batruch,

• Kotlyar, Max, University Health Network, Toronto, Toronto, Ontario, Canada

Max Kotlyar,

• Pastrello, Chiara, University Health Network, Toronto, Toronto, Ontario, Canada

Chiara Pastrello,

• Van, Julie Anh Dung, University of Toronto, Toronto, Ontario, Canada

Julie Anh Dung Van,

• Bozovic, Andrea, University Health Network, Toronto, Toronto, Ontario, Canada

Andrea Bozovic,

• Kulasingam, Vathany, University Health Network, Toronto, Toronto, Ontario, Canada

Vathany Kulasingam,

• Chruscinski, Andrzej, University Health Network, Toronto, Toronto, Ontario, Canada

Andrzej Chruscinski,

• John, Rohan, University Health Network, Toronto, Toronto, Ontario, Canada

Rohan John,

• Konvalinka, Ana, University Health Network, Toronto, Toronto, Ontario, Canada

Ana Konvalinka,

Background

Kidney transplantation is the optimal treatment for end-stage kidney disease, but most grafts fail prematurely. Antibody-mediated rejection (AMR) is responsible for >50% of graft loss. AMR is caused by antibodies against HLA and non-HLA antigens, which are directed against proteins in the two main compartments of the kidney: glomeruli and tubulointerstitium (TI). We hypothesized that renal AMR is associated with compartment-specific proteome alterations that may uncover the mechanisms of early antibody-mediated injury.

Methods

We performed laser capture-microdissection to isolate glomeruli and TI from paraffin-embedded kidney biopsies, and subjected samples to proteome analysis on Q-Exactive mass spectrometer. We compared 8 biopsies with pure AMR with 23 matched ‘non-AMR’ biopsies with cellular rejection (ACR) or acute tubular necrosis (ATN). Biopsies were for-cause and scored using Banff criteria-2017.

Results

Biopsies were performed early post-transplant; none of them had marked fibrosis. AMR biopsies were C4d+ and had no chronic lesions. We identified 2026 proteins in glomeruli and 2426 in TI. Podocyte-specific proteins were exclusively found in the glomeruli (NPHS1, PTPRO), and tubular proteins were found only in TI (CUBN, UMOD), indicating compartment-specific enrichment. 141 proteins were differentially expressed in AMR vs. non-AMR glomeruli (73 up- and 68 downregulated) and 123 in TI (15 up- and 108 downregulated). Proteins involved in HLA-mediated antigen presentation were increased in both AMR compartments. Interestingly, proteins significantly decreased in both compartments in AMR (e.g.LAMC1, COL1A1, NID1) belong to basement membranes and processes such as integrin signaling, collagen, extracellular matrix (ECM) and cytoskeleton. Levels of collagens, laminins, and other ECM proteins directly correlated (R>0.7; p<0.05), suggesting co-regulation in renal AMR.

Conclusion

Basement membranes are often remodeled in late chronic AMR and are the targets of non-HLA antibodies, suggesting that these proteomic changes may represent early, important alterations in AMR. Targeting early ECM remodeling in AMR may represent a new therapeutic opportunity.