MicroRNA Expression for Early Prediction of Late Occurring Hematologic Acute Radiation Syndrome in Baboons

Abstract

For effective medical management of radiation-exposed persons after a radiological/nuclear event, blood-based screening measures in the first few days that could predict hematologic acute radiation syndrome (HARS) are needed. For HARS severity prediction, we used microRNA (miRNA) expression changes measured on days one and two after irradiation in a baboon model. Eighteen baboons underwent different patterns of partial or total body irradiation, corresponding to an equivalent dose of 2.5 or 5 Gy. According to changes in blood cell counts (BCC) the surviving baboons (n = 17) exhibited mild (H1-2, n = 4) or more severe (H2-3, n = 13) HARS. In a two Stage study design we screened 667 miRNAs using a quantitative real-time polymerase chain reaction (qRT-PCR) platform. In Stage II we validated candidates where miRNAs had to show a similar regulation (up- or down-regulated) and a significant 2-fold miRNA expression difference over H0. Seventy-two candidate miRNAs (42 for H1-2 and 30 for H2-3) were forwarded for validation. Forty-two of the H1-2 miRNA candidates from the screening phase entered the validation step and 20 of them showed a statistically significant 2–4 fold up-regulation relative to the unexposed reference (H0). Fifteen of the 30 H2-3 miRNAs were validated in Stage II. All miRNAs appeared 2–3 fold down-regulated over H0 and allowed an almost complete separation of HARS categories; the strongest candidate, miR-342-3p, showed a sustained and 10-fold down-regulation on both days 1 and 2. In summary, our data support the medical decision making of the HARS even within the first two days after exposure where diagnostic tools for early medical decision are required but so far missing. The miRNA species identified and in particular miR-342-3p add to the previously identified mRNAs and complete the portfolio of identified mRNA and miRNA transcripts for HARS prediction and medical management.

Pre-Exposure Gene Expression in Baboons with and without Pancytopenia after Radiation Exposure

“…That differs from previously published work of our group where we successfully predicted the late occurring HARS based on gene expression changes measured at the first and second day after exposure and not on pre-exposure samples [12,13]. …”

“…That from the statistical point of view is an objective parameter assuming an association. In previous work on this baboon model we already searched for gene expression changes associated with other endpoints [12,13]. Preliminary validation steps using in vivo irradiated human patient samples confirmed most of our potential gene targets.…”

Nonhuman primates as models for the discovery and development of radiation countermeasures

“…In an elegant study using baboons, miR-342-3p demonstrated a sustained and 10-fold down-regulation on d 1 and 2 after irradiation. [13]. In addition, recent studies showed that seven microRNAs are altered by irradiation in NHPs (mir-150, miR-215, miR-30A, miR-126, miR-133a, miR-375, and miR-133b) [123] Furthermore, the genomic studies revealed that there is a combination of seven transcription factors that are predicted to regulate these miRNAs in mice, NHPs, and humans.…”

“…In addition to rhesus and cynomolgus macaques, several studies have been conducted using baboons (Papio sp) to investigate radiation injuries resulting from exposure to X-rays [9], 60 Co γ-radiation [10,11], and mixed field (neutron and γ-photon) irradiation [12]. In recent years, various studies have reported significant biomarkers for radiation injuries using the baboon model [13–17]. Furthermore, a number of promising radiation countermeasures under development for H-ARS are being tested in NHPs for efficacy and pharmacokinetics/pharmacodynamics (Table 2).…”

Ionizing radiation-induced altered microRNA expression as biomarkers for assessing acute radiation injury

“…Another study using rhesus macaques also demonstrated the upregulation of miR-126–3p and downregulation of miR-150–5p [6]. In a study using the baboon model, unlike rhesus macaques, miR-342–3p was found to be most affected (10-fold sustained downregulation) at 24 and 48 h post-irradiation compared to samples collected from animals prior to irradiation [7]. …”