Lauren S Kelly, MD
Jennifer A. Munley, MD
Erick E. Pons, BS
Preston S. Coldwell, BS
Kolenkode B. Kannan, PhD
Hari K. Parvataneni, MD
Jennifer E. Hagen, MD
Philip A. Efron, MD
Alicia M. Mohr, MD
University of Florida Department of Surgery, University of Florida Department of Orthopedic Surgery
Keywords: microRNA, bone marrow, trauma, humans, inflammation
Synopsis: Severe trauma is associated with hemorrhagic shock, tissue injury, systemic inflammation, and subsequent bone marrow dysfunction. MicroRNA (miRNA) are small, noncoding RNA segments that act as transcription factors and post-transcriptional modulators. The dysregulation of miRNAs has been shown to be associated with disease severity and therapeutic outcomes. We hypothesized that following trauma, patients would experience widespread inflammatory activation and disruption of erythropoietic pathways within the bone marrow.
Purpose: The aim of this study was to characterize the differential expression of miRNA in human bone marrow following severe trauma.
Methods: In a prospective observational cohort study at a Level I trauma center, bone marrow aspirates were obtained from severely injured trauma patients with hemorrhagic shock on arrival with a concurrent pelvic or lower extremity long bone fracture (n=24), operative controls undergoing elective total hip replacement (THR) (n=20) and healthy nonoperative controls (n=6). RNA was isolated from bulk bone marrow using a Purelink RNA mini kit. Genome-wide miRNA expression patterns were assayed using an Affymetrix GeneChip miRNA 4.0 array to look for over 30,000 mature miRNA sequences and 24,000 hairpin sequences. Differential miRNA expression was analyzed using BRBArrayTools with significance set at p < 0.01, looking only at those miRNA with differential expression of at least twofold.
Results: Average age for trauma patients, THR operative controls, and healthy nonoperative controls was 47, 65, and 27 years, respectively. 58% of trauma patients were male, compared to 40% in THR operative controls and 67% in nonoperative healthy controls. Average injury severity score (ISS) among trauma patients was 25. Compared with elective hip replacement patients, 69 differentially expressed miRNAs were identified (Figure). Among the 30 upregulated miRNAs following trauma, many were involved in cell cycle regulation, inhibition of tissue angiogenesis, and promotion of proinflammatory processes (e.g., miR-32-5p, miR-16-2-3p, miR-455-3p, miR-3613-5p, miR-6886-3p, miR-4674). The 39 downregulated miRNA following trauma were involved in erythropoiesis, angiogenesis, anti-inflammatory regulation, and important adhesion molecules for stem cell self-renewal (e.g., miR-125b-5p, miR-181b-5p, miR-181a-5p, miR-223-3p, miR-145-5p, miR-354-5p, miR-342-5p). Within the trauma cohort, there were no differentially expressed miRNA when grouped by ISS or age.
Conclusions: There is a differential bone marrow miRNA expression following severe trauma compared to elective hip replacement patients and healthy controls. These proinflammatory, anti-erythropoietic, and anti-angiogenic miRNA trends are consistent with broader gene expression patterns postinjury and are likely linked to the bone marrow dysfunction seen following severe trauma.