In vitro, C5a transdifferentiated human pericytes in myofibroblasts, with increased αSMA expression in stress fibers, collagen I production, and decreased antifibrotic protein Id2. Treatment by C1-inhibitor (C1-INH) significantly preserved the phenotype of pericytes maintaining microvascular density and capillary lumen area at tubulointerstitial level. In addition, PMT was associated with significant reduction in peritubular capillary luminal diameter. Using a swine model of renal ischemia/reperfusion (I/R) injury, we found the occurrence of PMT after 24 h of I/R injury as demonstrated by reduction of PDGFRβ +/NG2 + cells with increase in myofibroblasts marker αSMA. Here, we investigated the role of complement in inducing PMT after transplantation. However, the modulation of pericyte-to-myofibroblast transdifferentiation (PMT) in the early phases of acute kidney injury is poorly understood. Pericytes are one of the principal sources of scar-forming myofibroblasts in chronic kidneys disease. This could lead to the decrease of extracellular matrix protein accumulation by perivascular pericytes (C5aR, complement component C5a Receptor 1 MAPK, mitogen-activated protein kinase, ERK, extracellular signal-regulated kinases SMAD, small mother against decapentaplegic). Blocking of pERK, by SC1 (Pluripotin) a dual kinase (ERK1, MAPK3) inhibitor of Thr-202/Tyr-204 phosphorylation could interferes with C5a-induced transcription of pro-inflammatory and with SMAD3 phosphorylation. As common downstream mechanisms, the C5a exposition led to transcription of profibrotic gene and proteinase for detachment. In addition, pERK could be involved in the activation of SMAD-dependent TGFβ pathway (canonical pathway, green arrow and factors) inducing the SMAD2/3 phosphorylation (red dotted arrow). Independently from TGFβ presence, C5a could activate SMAD-independent signaling leading to activation of profibrotic pathway. pERK activation is also one of the final effector factors of SMAD-independent TGFβ pathway (non-canonical pathway) that include various branches of MAP kinase pathways, Rho-like GTPase signaling pathways and phosphatidylinositol-3-kinase/AKT pathways ( not showed). C5aR, a G protein-coupled receptor for C5a anaphylotoxin, promotes the MAPK signaling activation (Ras/Raf/MEK), inducing the extracellular signal-regulated kinases (ERK) phosphorylation and transcription of pro-inflammatory and pro-fibrotic genes. Magnification, 50×.įigure S3: Schematic pathway showing the possible cross-talk between C5aR and TGFβ canonical and non-canonical pathway. Results are expressed as median ± interquartile range of the numbers of PDGFRβ +/C3 + cells/HPF of five independent pigs for each group (H). ![]() Isotype control staining was used as negative control (F). C1-INH treatment limited the C3 deposition (E). After 30 min of I/R injury, the number of PDGFRβ +/C3 + cells increased predominately at peritubular capillaries level. In T0, PDGFRβ +/C3 + perivascular cells were barely detectable (C). ![]() Immunofluorescence images showing interstitial peritubular capillaries pericytes co-labeled with PDGFRβ (green) and C3 (red). Results are expressed as mean ± SD of Casp3 + or Ki-67 + cells/high power fields (HPF). At different times from reperfusion, the Casp3 + and Ki-67 + were detected predominately at tubular level. ![]() Quantification of Casp3 + (A) and Ki-67 + (B) cells by IHC after I/R injury with distinction between tubular and perivascular cells. Figure S1: Ischemia/reperfusion (I/R) injury did not induce apoptosis or proliferation within perivascular compartment.
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