Prolonged Mechanical Ventilation Alters the Expression Pattern of Angio-neogenetic Factors in a Pre-Clinical Rat Model

OBJECTIVE: Mechanical ventilation (MV) is a life saving intervention for patients with respiratory failure. Even after 6 hours of MV, diaphragm atrophy and dysfunction (collectively referred to as ventilator-induced diaphragmatic dysfunction, VIDD) occurs in concert with a blunted blood flow and oxygen delivery. The regulation of hypoxia sensitive factors (i.e. hypoxia inducible factor 1α, 2α (HIF-1α,-2α), vascular endothelial growth factor (VEGF)) and angio-neogenetic factors (angiopoietin 1-3, Ang) might contribute to reactive and compensatory alterations in diaphragm muscle. METHODS: Male Wistar rats (n = 8) were ventilated for 24 hours or directly sacrificed (n = 8), diaphragm and mixed gastrocnemius muscle tissue was removed. Quantitative real time PCR and western blot analyses were performed to detect changes in angio-neogenetic factors and inflammatory markers. Tissues were stained using Isolectin (IB 4) to determine capillarity and calculate the capillary/fiber ratio. RESULTS: MV resulted in up-regulation of Ang 2 and HIF-1α mRNA in both diaphragm and gastrocnemius, while VEGF mRNA was down-regulated in both tissues. HIF-2α mRNA was reduced in both tissues, while GLUT 4 mRNA was increased in gastrocnemius and reduced in diaphragm samples. Protein levels of VEGF, HIF-1α, -2α and 4 did not change significantly. Additionally, inflammatory cytokine mRNA (Interleukin (IL)-6, IL-1β and TNF α) were elevated in diaphragm tissue. CONCLUSION: The results demonstrate that 24 hrs of MV and the associated limb disuse induce an up-regulation of angio-neogenetic factors that are connected to HIF-1α. Changes in HIF-1α expression may be due to several interactions occurring during MV

Prolonged mechanical ventilation alters the expression pattern of angio-neogenetic factors in a pre-clinical rat model

Mechanical ventilation (MV) is a life saving intervention for patients with respiratory failure. Even after 6 hours of MV, diaphragm atrophy and dysfunction (collectively referred to as ventilator-induced diaphragmatic dysfunction, VIDD) occurs in concert with a blunted blood flow and oxygen delivery. The regulation of hypoxia sensitive factors (i.e. hypoxia inducible factor 1α, 2α (HIF-1α,-2α), vascular endothelial growth factor (VEGF)) and angio-neogenetic factors (angiopoietin 1-3, Ang) might contribute to reactive and compensatory alterations in diaphragm muscle.status: publishe

mRNA relative expression of inflammatory cytokines in ventilated animals compared to controls.

<p>Panel (A) shows changes in diaphragm muscle tissue, panel (B) changes in gastrocnemius muscle tissue. * indicate p<0.05. IL  =  Interleukin TNF = Tumor necrosis factor. RQ relative quantity. Further explanation see text. The horizontal line, box, and whiskers of each box plot represent the median, the interquartile range, and the upper and lower range of the data, respectively. n = 8/per group.</p

Changes in capillary/ fiber ratio in both tissues.

<p>Panel (A) shows an example of the staining in diaphragmatic tissue, Panel (B) depicts the capillary/fiber ratio in both tissues. Red dots in the picture indicate capillaries, while blue ones are DAPI stained nuclei. n = 8/group, control diaphragm n = 7; * p<0.05.</p

mRNA relative expression of hypoxia regulated transcription factors in ventilated animals compared to controls.

<p>Panel (A) shows changes in diaphragm muscle tissue, panel (B) changes in gastrocnemius muscle tissue. ** indicate p<0.001, *** p<0.0001. HIF = hypoxia inducible factor, VEGF = vascular endothelial growth The horizontal line, box, and whiskers of each box plot represent the median, the interquartile range, and the upper and lower range of the data, respectively. n = 8/group.</p

mRNA relative expression of angio-neogenetic factors in ventilated animals compared to unventilated controls.

<p>Panel (A) shows changes in diaphragm muscle tissue, panel (B) changes in gastrocnemius muscle tissue. ** indicate p<0.001, *** p<0.0001. Ang = Angiopoietin, RQ relative quantity. Further explanation see text. The horizontal line, box, and whiskers of each box plot represent the median, the interquartile range, and the upper and lower range of the data, respectively. n = 8/per group.</p

p-values and fold-changes of mRNA expression in diaphragm and mixed gastrocnemius tissue of MV compared to control.

*<p>indicates significant change versus control.</p