Plasminogen Activator Inhibitor-1 (PAI-1) Affects Parietal Epithelial Cell (PECs) Transition
Guohui Ren, Mohammed Khusheim, Haichun Yang, Agnes B Fogo. Vanderbilt University, Nashville, TN
Background: Glomerular PECs may migrate to the glomerular tuft and serve as potential podocyte stem cells, expressing some podocyte markers. However, whether such visceral location PECs can be functional podocytes or are more mesenchymal and profibrotic is not established. Our previous data show that PAI-1-/- mice are protected against development of sclerosis and podocyte injury. In this study, we explored whether the transition of PECs is modulated by the expression of PAI-1.
Design: We studied NEP25 mice, in which selective podocyte injury can be induced by injection of the toxin LMB2, that were bred to PAI-1-/- mice (NEP25xPAI-1-/-, n=10) and compared to toxin injury in mice with intact PAI-1 (NEP25xWT, n=6). At day 20 after LMB2 injection mice were sacrificed and renal changes were analyzed. Mouse PECs were cultured and injured with angiotensin II (Ang II), or exposed to supernatant from intact or toxin-injured NEP25 podocytes.
Results: At day 20 after LMB2 injection, NEP25xPAI-1-/- mice had significantly attenuated glomerulosclerosis compared to NEP25xWT mice (sclerosis index 1.73± 0.09 vs. 2.14±0.18, 0-4 scale, p<0.05). Synaptopodin positive cells were increased in NEP25xPAI-1-/- vs. NEP25xWT mice (15.1±1.8 vs. 6.7±1.0 /glomerulus, p<0.01). Glomerular visceral epithelial location cells co-expressing CD44 and synaptopodin were significantly increased in NEP25xPAI-1-/- mice compared to NEP25xWT mice (4.8±0.4 vs. 0.9±0.1/glomerulus, p<0.001). However, NEP25xWT mice had significantly more glomerular CD44 positive cells than NEP25xPAI-1-/- mice (14.3±1.0 vs. 21.5±2.9/glomerulus, p<0.05), suggesting that more PECs were activated and transdifferentiated to mesenchymal type cells. Cultured mouse PECs expressed similar PAI-1 protein at baseline and after Ang II. Treatment with a dominant negative PAI-1 mutant protein (without proteolytic inhibition activity but with intact VN binding) reduced PEC expression of PAI-1 26.5% (P<0.05), inhibited PEC migration and abolished Ang II-accelerated PEC migration. When PECs were treated with supernatant from LMB2-injured primary cultured NEP25 mouse podocytes, the expression of CD44, a marker of activated PECs, was increased 26.4%.
Conclusions: PAI-1 deficiency in PECs inhibits PEC migration in vitro. However, in vivo NEP25xPAI-1-/- mice had more parietal podocytes and less sclerosis compared to NEP25xWT mice. These results support that systemic PAI-1 deficiency promotes PEC transition with associated less sclerosis, perhaps by promoting more functional podocyte-like rather than profibrotic type transition of PECS.
Category: Kidney (does not include tumors)
Tuesday, March 5, 2013 9:15 AM
Proffered Papers: Section H, Tuesday Morning