Effect of mesenchymal stem cells on the host response in severe community-acquired pneumonia

Abstract

Mesenchymal stem cells (MSC) have immune regulatory properties that may ameliorate pathophysiological processes in sepsis. We determined the effect of allogeneic adipose-derived MSCs (Cx611) on the host response during sepsis due to community-acquired bacterial pneumonia (CABP) by measuring 29 plasma biomarkers and blood transcriptomes at six time points in 82 patients randomised to two intravenous infusions of Cx611 or placebo. Cx611 treatment enhanced several endothelial cell and procoagulant response plasma biomarkers, and led to increased expression of pathways related to innate immunity, haemostasis and apoptosis. Cx611 infusion in sepsis due to CABP is associated with broad host response alterations.

Keywords: Critical Care; Pneumonia.

Figure 1. Overview of study design and effect of Cx611 treatment on plasma host response biomarkers stratified according to pathophysiological domains. (A) Overview of time points at which samples were collected for plasma protein and RNA biomarker analyses: within 18 hours of initiation of vasopressors and/or mechanical ventilation, prior to the initiation of treatment (screening/SCR), 8–12 hours following the initial infusion of Cx611 or placebo on day 1 (visit 1/V1), day 2 (V2), 8–12 hours following the second infusion of Cx611 or placebo on day 3 (V3), day 7 (V7) and day 14±2 (V9). Sample collection continued after intensive care unit (ICU) and hospital discharge. Number of samples available for plasma biomarker analyses listed to the right of each time point, Cx611-treated patients in orange, placebo-treated patients in blue/grey. (B) Heatmap showing the levels of each plasma protein host response biomarker, divided across five pathophysiological domains, for patients treated with Cx611 relative to patients treated with placebo at each time point after the initiation of treatment, expressed as an effect size (Hedges’ g, red indicates higher values and blue indicates lower values in Cx611-treated patients). For visual purposes, comparisons with a Hedges’ g >−0.2 and <0.2 (considered a negligible effect) are displayed as white tiles. To account for baseline variation in biomarker levels not attributable to treatment, we used the fold change from prior to treatment (screening/SCR time point) to each time point for each patient. The p values displayed to the right of heatmap are derived from a type II Wald test on linear mixed models for each individual biomarker (as described in the statistical analysis paragraph in the online supplemental methods), and indicate whether the overall effect of Cx611 on biomarker concentrations over all time points after initiation of treatment, adjusted for baseline variation in biomarker levels, is statistically significant. These p values were adjusted for multiple testing per domain using the Benjamini-Hochberg (BH) method. CCL, CC chemokine ligand; HGF, hepatocyte growth factor; IL-1RA, interleukin 1 receptor antagonist; MMP-8, matrix metalloproteinase 8; NGAL, neutrophil gelatinase-associated lipocalin; PAI-1, plasminogen activator inhibitor 1; TNF, tumour necrosis factor; TRAIL, TNF-related apoptosis-inducing ligand; TREM-1, triggering receptor expressed on myeloid cell 1; VCAM-1, vascular cell adhesion molecule 1.

Figure 2. Significant immune system pathways from gene set enrichment analysis of the blood transcriptome. Bubble plot displaying the effect of Cx611 treatment on transcriptional pathways related to the immune system (as obtained from the Reactome knowledgebase) for each time point after the initiation of treatment with Cx611 or placebo. To adjust for chance variation in baseline gene expression between groups, the differences in gene expression at each time point are derived from the interaction terms between Cx611 and time point in linear mixed models that included the SCR time point (prior to initiation as treatment) as the reference category, and can therefore be interpreted as the difference in gene expression levels between groups at each time point relative to the gene expression levels prior to initiation of treatment. The differences in expression of genes in the listed pathways are quantified as NES and reflected in the intensity of the colour: a red bubble means higher in the Cx611-treated group, a blue bubble means lower in the Cx611-treated group and a grey bubble indicates a negligible difference. The size of the bubble is proportional to the Benjamini-Hochberg (BH)-adjusted p value for that pathway. This figure only includes pathways in which a significant difference between groups was found at one or more time points; the full version of the figure including non-significant pathways can be found in online supplemental figure 7. CLEC7A, C-type lectin domain family 7 member A; Fc, fragment crystallisable region (of an antibody); FLT3, fms-related receptor tyrosine kinase 3; G-CSF, granulocyte colony-stimulating factor; GM-CSF, granulocyte-macrophage colony-stimulating factor; IFN, interferon; MAPK, mitogen-activated protein kinase; MHC, major histocompatibility complex; NF-κB, nuclear factor kappa-light-chain-enhancer of activated B cells; NIK, NF-κB-inducing kinase; NLR, nucleotide-binding domain leucine-rich repeat containing receptor; PD-1, programmed death 1; TCR, T cell receptor; TNF, tumour necrosis factor.