D 16 + monocytes with smooth muscle cell characteristics are educed in human renal chronic transplant dysfunction

In chronic transplant dysfunction (CTD), persistent (allo)immune-mediated inflammation eventually leads to tissue remodeling including neointima formation in intragraft arteries. We previously showed that recipient-derived neointimal -SMA+ smooth muscle-like cells are present in human renal allografts with CTD. Human PBMC contain myeloid cells capable of differentiating into -SMA+ cells in vitro; the phenotype of the ancestral subset is as yet unknown. This study aimed to investigate whether monocyte subsets contain cells with smooth muscle-like cell differentiation capacity and whether CTD in renal transplant recipients is associated with a shift in these monocyte subsets. To accomplish this goal, monocyte subsets from healthy controls were sorted based on CD14 and CD16 expression to investigate gene expression levels of mesenchymal markers -SMA and SM22 . CD14+/CD16++ monocytes displayed increased -SMA and SM22 mRNA expression compared with CD14++/CD16− monocytes, suggesting increased differentiation potential toward smooth muscle-like cells. Flow cytometry revealed that in nonCTD transplant recipients the percentage of CD14+/CD16++ monocytes was reduced, with an even further reduction in patients with CTD. To determine a potential correlation between CD14+/CD16++ monocytes and -SMA+ cell outgrowth potential in vitro, PBMC of healthy controls and transplant recipients with and without CTD were cultured under fibrotic culture conditions, and indeed a significant correlation (p = 0.0002, r = 0.62) was observed. Finally, double staining for -SMA and CD16 revealed presence of -SMA+CD16+ cells in kidney explants from CTD patients, albeit at very low numbers. Our data represent evidence that, compared to CD14++CD16− monocytes, CD14+CD16++ monocytes have an increased expression of smooth muscle cell-associated genes. This monocyte subpopulation is reduced in renal transplant patients with CTD, possibly due to selective migration into the allograft. © 2014 Elsevier GmbH. All rights reserved. Abbreviations: -SMA, -Smooth muscle actin; CTD, chronic transplant dysunction; ECM, extracellular matrix; IF/TA, interstitial fibrosis and tubular atrophy; BMC, peripheral blood mononuclear cells; SMC, smooth muscle cell; TGF1, transorming growth factor1. ∗ Corresponding author at: Department of Pathology & Medical Biology, Division f Medical Biology (HPC: EA11), University of Groningen, University Medical Center roningen, Hanzeplein 1, PO Box 30.001, NL-9700 RB Groningen, The Netherlands. el. : +31 50 3615878; fax: +31 50 3619911. E-mail address: m.boersema@umcg.nl (M. Boersema). 1 Share senior authorship. ttp://dx.doi. org/10.1016/j.imbio. 2014.11. 011 171-2985/© 2014 Elsevier GmbH. All rights reserved. Introduction Chronic renal transplant dysfunction (CTD), clinically evidenced by a gradual decline in kidney function and proteinuria, is histologically characterized by chronic transplant glomerulopathy, interstitial fibrosis and tubular atrophy (IF/TA), and transplant vasculopathy (TV) (Chapman et al. 2005; El-Zoghby et al. 2009; Solez et al. 2007). TGF1 is recognized as a strong inducer of tubulointerstitial fibrosis in CKD (Lopez-Hernandez and Lopez-Novoa 2012), including renal CTD (Djamali and Samaniego 2009). Furthermore, TGF1 serum levels have been associated with development of end-stage renal disease (Suthanthiran et al. 1998), and renal transplant recipients with CTD were shown to have increased TGF1