Louise Crowe’s research while affiliated with National University of Ireland, Maynooth and other places

Clinical trials investigating the potential of mesenchymal stromal cells (MSCs) for the treatment of inflammatory diseases, such as acute respiratory distress syndrome (ARDS), have been disappointing, with less than 50% of patients responding to treatment. Licensed MSCs show enhanced therapeutic efficacy in response to cytokine-mediated activation signals. There are two distinct sub-phenotypes of ARDS: hypo- and hyper-inflammatory. We hypothesized that pre-licensing MSCs in a hyper-inflammatory ARDS environment would enhance their therapeutic efficacy in acute lung inflammation (ALI). Serum samples from patients with ARDS were segregated into hypo- and hyper-inflammatory categories based on interleukin (IL)-6 levels. MSCs were licensed with pooled serum from patients with hypo- or hyper-inflammatory ARDS or healthy serum controls. Our findings show that hyper-inflammatory ARDS pre-licensed MSC conditioned medium (MSC-CMHyper) led to a significant enrichment in tight junction expression and enhanced barrier integrity in lung epithelial cells in vitro and in vivo in a vascular endothelial growth factor (VEGF)-dependent manner. Importantly, while both MSC-CMHypo and MSC-CMHyper significantly reduced IL-6 and tumor necrosis factor alpha (TNF-α) levels in the bronchoalveolar lavage fluid (BALF) of lipopolysaccharide (LPS)-induced ALI mice, only MSC-CMHyper significantly reduced lung permeability and overall clinical outcomes including weight loss and clinical score. Thus, the hypo- and hyper-inflammatory ARDS environments may differentially influence MSC cytoprotective and immunomodulatory functions.

CO2 is produced during aerobic respiration. Normally, levels of CO2 in the blood are tightly regulated but pCO2 can rise (hypercapnia, pCO2 > 45 mmHg) in patients with lung diseases e.g. Chronic Obstructive Pulmonary Disease (COPD). Hypercapnia is a risk factor in COPD but may be of benefit in the context of destructive inflammation. The effects of CO2 per se, on transcription, independent of pH change are poorly understood and warrant further investigation. Here we elucidate the influence of hypercapnia on monocytes and macrophages through integration of state-of-the-art RNA-sequencing, metabolic and metabolomic approaches. THP-1 monocytes and IL4 polarised primary murine macrophages were exposed to 5% CO2 Vs 10% CO2 for up to 24 h in pH- buffered conditions. In hypercapnia, we identified ~370 differentially expressed genes (DEGs) under basal and ~1889 DEGs under LPS-stimulated conditions in monocytes. Transcripts relating to both mitochondrial and nuclear-encoded gene expression were enhanced in hypercapnia in basal and LPS-stimulated cells. Mitochondrial DNA content was not enhanced, but acylcarnitine species and genes associated with fatty acid metabolism were increased in hypercapnia. Primary macrophages exposed to hypercapnia also increased activation of genes associated with fatty acid metabolism and reduced activation of genes associated with glycolysis. Thus, hypercapnia elicits metabolic shifts in lipid metabolism in monocytes and macrophages under pH buffered conditions. These data indicate that CO2 is an important modulator of monocyte transcription that can influence immunometabolic signalling in immune cells in hypercapnia. These immunometabolic insights may be of benefit in the treatment of patients experiencing hypercapnia.