Local Medial Microenvironment Directs Phenotypic Modulation of Smooth Muscle Cells After Experimental Renal Transplantation

Abstract

Smooth muscle cells (SMCs) play a key role in the pathogenesis of occlusive vascular diseases, including transplant vasculopathy. Neointimal SMCs in experimental renal transplant vasculopathy are graft-derived. We propose that neointimal SMCs in renal allografts are derived from the vascular media resulting from a transplantation-induced phenotypic switch. We examined the molecular changes in the medial microenvironment that lead to phenotypic modulation of SMCs in rat renal allograft arteries with neointimal lesions. Dark Agouti donor kidneys were transplanted into Wistar Furth recipients and recovered at day 56. Neointimal and medial layers were isolated using laser microdissection. Gene expression was analyzed using low-density arrays and confirmed by immunostaining. In allografts, neointimal SMCs expressed increased levels of Tgf b1 and Pdgfb. In medial allograft SMCs, gene expression of Ctgf, Tgf b1 and Pdgfrb was upregulated. Gene expression of Klf4 was upregulated as well, while expression of Sm22a was downregulated. Finally, PDGF-BB-stimulated phenotypically modulated SMCs, as evidenced by reduced contractile function in vitro which was accompanied by increased Klf4 and Col1a1, and reduced a-Sma and Sm22a expression. In transplant vasculopathy, neointimal PDGF-BB induces phenotypic modulation of medial SMCs, through upregulation of KLF4 in the media to contribute to (further) expansion of the neointima.

Incipient renal transplant dysfunction associates with tubular syndecan-1 expression and shedding

“…This animal experiment was approved by the local ethical committee on animal experimentation of the State University of Groningen and was in compliance with Directive 2010/63/EU of the European Parliament. Details on the transplantation procedure and followup of the rats have been previously described (8,22,39). Nine weeks after transplantation, rats were euthanized, and kidneys were cryopreserved for mRNA isolation and immunohistology.…”

“…We have previously described the dark agouti to Wistar Furth rat renal transplantation model (8,22,39). This model is characterized by progressive worsening of renal function and the development of interstitial fibrosis, tubular atrophy, and transplant vasculopthy.…”

Renal Allograft Fibrosis: Biology and Therapeutic Targets

“…Experimental data also suggest that PDGFs are differentially induced by cyclosporine and tacrolimus, in particular in macrophages, and that this may be related to the lower fibrogenic potential of tacrolimus compared to cyclosporine (305). In addition, neointimal PDGF-B and -D as well as b-receptor also contribute to transplant vasculopathy by inducing phenotypic modulation of vascular smooth muscle cells (306)(307)(308). Few intervention studies with inhibitors of the PDGF system have been performed in the renal transplant setting.…”

Increased migration of antigen presenting cells to newly-formed lymphatic vessels in transplanted kidneys by glycol-split heparin

“…RNA isolation and quantitative RT-PCR were performed essentially according to Asgeirsdottir et al [26]. Experimental details are described elsewhere [27]. Gene expression was analyzed with a custom made microfluidic card-based low density array (Applied Biosystems, Nieuwerkerk a/d IJssel, the Netherlands) using the ABI Prism 7900HT Sequence Detection System (Applied Biosystems, Nieuwerkerk a/d IJssel, the Netherlands).…”