Human mesenchymal stromal cells broadly modulate high glucose-induced inflammatory responses of renal proximal tubular cell monolayers

BACKGROUND: Renal proximal tubular epithelial cells (RPTEC) are dysfunctional in diabetic kidney disease (DKD). Mesenchymal stromal cells (MSC) may modulate DKD pathogenesis through anti-inflammatory mediators. This study aimed to investigate the pro-inflammatory effect of extended exposure to high glucose (HG) concentration on stable RPTEC monolayers and the influence of MSC on this response. METHODS: Morphologically stable human RPTEC/TERT1 cell monolayers were exposed to 5 mM and 30 mM (HG) D-glucose or to 5 mM D-glucose + 25 mM D-mannitol (MAN) for 5 days with sequential immunoassays of supernatants and end-point transcriptomic analysis by RNA sequencing. Under the same conditions, MSC-conditioned media (MSC-CM) or MSC-containing transwells were added for days 4–5. Effects of CM from HG- and MAN-exposed RPTEC/MSC co-cultures on cytokine secretion by monocyte-derived macrophages were determined. RESULTS: After 72–80 h, HG resulted in increased RPTEC/TERT1 release of interleukin (IL)-6, IL-8, monocyte chemoattractant protein (MCP)-1 and neutrophil gelatinase-associated lipocalin (NGAL). The HG pro-inflammatory effect was attenuated by concentrated (10×) MSC-CM and, to a greater extent, by MSC transwell co-culture. Bioinformatics analysis of RNA sequencing data confirmed a predominant effect of HG on inflammation-related mediators and biological processes/KEGG pathways in RPTEC/TERT1 stable monolayers as well as the non-contact-dependent anti-inflammatory effect of MSC. Finally, CM from HG-exposed RPTEC/MSC transwell co-cultures was associated with attenuated secretion of inflammatory mediators by macrophages compared to CM from HG-stimulated RPTEC alone. CONCLUSIONS: Stable RPTEC monolayers demonstrate delayed pro-inflammatory response to HG that is attenuated by close proximity to human MSC. In DKD, this MSC effect has potential to modulate hyperglycemia-associated RPTEC/macrophage cross-talk.