# 586 Monitoring Monocyte Anisocytosis Changes in Adult and Pediatric Burn Patients

## TL;DR

This study shows that Monocyte Distribution Width (MDW) can track immune responses in burn patients and that resolvin D2 may help reduce inflammation.

## Contribution

The novel finding is that resolvin D2 can decrease MDW in burn patients, suggesting a potential therapeutic application.

## Key findings

- MDW increases in adult burn patients post-injury and remains elevated in non-survivors.
- Resolvin D2 significantly reduces MDW in both healthy and burn patient blood samples.
- RNA sequencing reveals inflammation-related genes are modulated by LPS and RvD2 treatments.

## Abstract

Burn injuries trigger pathological immune responses. However, our ability to monitor these evolving responses is constrained by the intricate confluence of cellular, biochemical, and metabolic alterations that occur concurrently post-injury. In this study, we concentrate on monocytes, which serve as key mediators of burn-induced changes and as potential biomarkers for monitoring immune responses after injury.

We enrolled adult and pediatric patients with major burn injuries (>15%) and collected blood samples twice a week during the hospitalization. We measured Monocyte Distribution Width (MDW) using a Beckman-Coulter Unicel DxH900 analyzer. As a reference, we measured the MDW changes in the presence of pro-inflammatory stimuli, e.g., lipopolysaccharide (LPS), as well as lipid mediators of inflammation resolution, e.g., resolvin D2 (RvD2). We performed single-cell RNA sequencing to identify MDW-associated transcriptional signatures in monocytes following treatment with LPS and RvD2 using HIVE CLX.

We enrolled N = 11 adults and N = 3 pediatric patients with major burn injuries, from whom we collected and analyzed N = 80 blood samples from adults and N = 35 from pediatric patients. In adults, we observed that MDW increased during the first week post-burn injury (MDW = 24.1), exceeding the threshold for healthy individuals of comparable age (MDW = 20.0), and gradually decreased by discharge. In non-surviving, MDW continued to rise for approximately 10 days post-injury (MDW = 28.7) and remained elevated until death. In pediatric patients with 65% TBSA burns, MDW fluctuated but remained elevated (MDW = 23.08), above the healthy threshold. However, in pediatric patients with lower TBSA burns (e.g. 45%), MDW was initially very high during the first week (MDW = 46.42), then rapidly decreased in the following week (MDW = 27.3) and continued to decline thereafter.

In blood samples from healthy donors, we found that MDW increased upon LPS stimulation (104 EU/mL, MDW= 31.8), at the higher end of values measured in patients. The addition of RvD2 (5 µM) after LPS stimulation decreased MDW significantly (MDW = 20.1, One-way ANOVA, LPS vs. RvD2 +LPS, P = 0.0002), towards values measured in healthy donors. The ex vivo addition of RvD2 to blood samples from adult burn patients with high MDW restored normal MDW values (two-tailed test, p = 0.0457, N = 4 blood samples). RNA seq analysis reveals that genes encoding proteins involved in inflammation-responsive cytokines (e.g. SLAMF7 and IL family) were significantly expressed in LPS treated monocytes and decreased in LPS+RvD2 treated monocytes.

In patients with major burns, changes in MDW could serve as a biomarker to track inflammation and its resolution throughout the hospitalization. The ability of RvD2 to decrease MDW is novel and deserves further investigation.

MDW values can be useful for monitoring hospitalized adult and pediatric burn patients.

Shriners Children’s