MicroRNA expression after ionizing radiation in human endothelial cells

<p>Abstract</p> <p>Background</p> <p>Endothelial cells (EC) in tumor and normal tissue constitute critical radiotherapy targets. MicroRNAs have emerged as master switchers of the cellular transcriptome. Here, we seek to investigate the role of miRNAs in primary human dermal microvascular endothelial cells (HDMEC) after ionizing radiation.</p> <p>Methods</p> <p>The microRNA status in HDMEC after 2 Gy radiation treatment was measured using oligo-microarrays covering 361 miRNAs. To functionally analyze the role of radiation-induced differentially regulated miRNAs, cells were transfected with miRNA precursor or inhibitor constructs. Clonogenic survival and proliferation assays were performed.</p> <p>Results</p> <p>Radiation up-regulated miRNA expression levels included let-7g, miR-16, miR-20a, miR-21 and miR-29c, while miR-18a, miR-125a, miR-127, miR-148b, miR-189 and miR-503 were down-regulated. We found that overexpression or inhibition of let-7g, miR-189, and miR-20a markedly influenced clonogenic survival and cell proliferation per se. Notably, the radiosensitivity of HDMEC was significantly influenced by differential expression of miR-125a, -127, -189, and let-7g. While miR-125a and miR-189 had a radioprotective effect, miR-127 and let-7g enhanced radiosensitivity in human endothelial cells.</p> <p>Conclusion</p> <p>Our data show that ionizing radiation changes microRNA levels in human endothelial cells and, moreover, exerts biological effects on cell growth and clonogenicity as validated in functional assays. The data also suggest that the miRNAs which are differentially expressed after radiation modulate the intrinsic radiosensitivity of endothelial cells in subsequent irradiations. This indicates that miRNAs are part of the innate response mechanism of the endothelium to radiation.</p

Strategic School Improvement Fund: updated 12 September 2017

<p><b>Comparison of MRI (A and B) with histological findings (C).</b> The lateral tibia plateau region of the sham knee joint of animal #8958 showed no salience neither in the sagittal MRI-scan (A) through the lateral compartment of the knee nor in the coronal MRI-scan (B) and was therefore rated as unchanged. The scale bars for A and B were determined with the program RadiAnt DICOM viewer (see caption <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0165897#pone.0165897.g001" target="_blank">Fig 1</a>). In contrast to the MRI results, the histological safranin-o staining (C) showed a moderate degeneration (Little-score: 10.5 points) with a fissure (1) in the cartilage and detachment of the topmost layer of the cartilage tissue. The histological finding and the MRI result did not concur.</p

Immunohistochemical staining.

<p>Results of the immunohistochemical staining of the examined regions of ACLR and sham operated knee joints with A) collagen II and B) collagen I. The score ranges from 0 (no staining) to 3 points. The results indicated no evident differences between the ACLR side and the sham side for neither Col II (A) nor Col I (B). This was in concurrence with our histological results (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0165897#pone.0165897.g002" target="_blank">Fig 2</a>). Sample of an immunhistological staining of collagen II (C) and collagen I (D) from the moderate degenerated (histological score: 9 points) sham operated side of the lateral tibia plateau of animal #8952 with an intense staining for collagen I (3 points) and a weak staining for collagen II (1 point).</p

Presence of the ligaments.

<p>The ACLR knee joint A) of animal #4085 showed only the <i>ligamentum cruciatum posterius</i> (arrow) whereas the sham knee joint B) of the same animal showed both cruciate ligaments were present (arrows). This showed that the operation of resecting the <i>ligamentum cruciatum anterius</i> was successful (A). A, B: The scale bars were determined with the program RadiAnt DICOM viewer (see caption <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0165897#pone.0165897.g001" target="_blank">Fig 1</a>).</p

Results of the histological scoring after consensus.

<p>The score for each area of interest–the medial/lateral condyle and the medial/lateral tibiaplateau of the ACLR and sham-operated knee joints- of eight Göttingen Minipigs are shown. The used score [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0165897#pone.0165897.ref035" target="_blank">35</a>] ranges from 0 points with no changes up to 25 points. As the results of the scoring showed, the sham knee joints were also affected with no significant differences between the ACLR and sham operated knee joints.</p

Macroscopic overview.

<p>A) The femoral condyles of the ACLR knee joint of animal #8952 showed no visible change/deterioration of the cartilage. B) The femoral condyles of the ACLR knee joint of animal #8955 showed different characteristics in form of a reduced cartilage coating (1) in the lateral condyle and even erosion of the cartilage (2) in the medial condyle. C) The lateral tibia plateau surface of the sham-operated knee joint of animal #8958 showed a slightly rough cartilage surface (arrow). A-C: The scale bars were determined with the corresponding x-ray images using the program RadiAnt DICOM viewer (build 3.4.1.13367, retrieved from <a href="http://www.radiantviewer.com/" target="_blank">http://www.radiantviewer.com</a>; October 12th 2016; Medixant (Poznan, Poland)).</p

Gene Expression.

<p>Normalized (ß-actin) gene expression for the evaluated genes from the examined regions of ACLR and sham knee joints. The results showed no evident differences between the ACLR and the sham operated side for the assessed genes A) <i>col1A1</i>, D) <i>mmp1</i>, E) <i>mmp3</i>, F) <i>mmp13</i>, H) <i>adamts5</i>, I) <i>il-1ß</i> and J) <i>vegf</i>. This would concur with the histological findings, where the sham operated group was as degenerated as the ACLR group and therefore not usable as a serious control group. The gene expressions of B) <i>col2</i>, C) <i>acan</i> and G) <i>adamts4</i> at first sight appeared to be differently expressed but as standard deviation was high, significant differences were not found. So no significant differences between the ACLR and sham sites were found in terms of gene expression in the end and therefore, no discrimination between an induced (ACLR) and spontaneous (sham) OA could be made.</p

MRI scoring.

<p>MRI scans of eight Göttingen Minipigs were scored according to an adapted WORMS-score. The score ranges from 0–22 points. The results showed that in the samples, either from ACLR or sham knee joints, no or only minor changes were visible in the MRI images.</p

Correlation gene expression vs histology.

<p>Correlation (r-values) of the gene expression findings with the scored histological findings.</p