Abstract Number: PB2003
Meeting: ISTH 2020 Congress
Background: Sepsis is a complex life-threatening inflammatory reaction. In bacterial sepsis, lipopolysaccharide (LPS) enters the patients’ blood circulation. However, it is unknown whether LPS can reach the bone marrow and stimulate resident megakaryocytes. In our proof-of-principle study, we particularly focus on interleukin 6 (IL6), a severity marker for sepsis, as a representative gene.
Aims: To assess if megakaryocytes are exposed and respond to LPS during bacterial sepsis.
Methods: We used human cord blood-derived megakaryocytes to study changes in mRNA expression with RNA sequencing and to assess IL6 secretion with ELISA. Megakaryocyte-specific IL6 protein expression was tested with immunocytochemistry. Plasma of septic patients and healthy donors were subjected to multiplex cytokine analysis. A murine polymicrobial sepsis model (cecal ligation and puncture; CLP) was used to examine IL6 mRNA expression in sorted bone marrow megakaryocytes by qPCR. LPS levels were measured by chromogenic endotoxin quantitation.
Results: In human megakaryocytes, 192 transcripts were regulated (LPS vs. PBS, n=3; Padj < 0.05). IL6 was among the most upregulated cytokines (Padj=4.1E-12) and was secreted into the supernatant. Human megakaryocytes co-stained for CD41 and IL6 suggesting megakaryocyte-specific expression. IL6 was elevated in plasma of septic patients compared to healthy controls (n≥8; Padj < 0.01). LPS levels were increased in plasma and bone marrow suspensions of CLP mice compared to non-treated controls (n≥10; P < 0.001). IL6 mRNA was upregulated in megakaryocytes from CLP mice compared to non-treated mice (2.2-fold; n≥3; P < 0.05).
Conclusions: We demonstrate both in vitro and in vivo that LPS reaches the bone marrow and changes the gene expression profile of megakaryocytes in bacterial sepsis. We hypothesize direct consequences in the bone marrow milieu which could become impactful in disease.
To cite this abstract in AMA style:Krauel K, Campbell R, Middleton E, Rondina M, Guo L, Bhatlekar S, Montenont E, Blair A, Weyrich A. Megakaryocytes Are Reprogrammed by Lipopolysaccharide Exposure during Bacterial Sepsis [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/megakaryocytes-are-reprogrammed-by-lipopolysaccharide-exposure-during-bacterial-sepsis/. Accessed November 30, 2021.
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