Fat Emboli in the Rat Aorta in a Model of Fat Embolism Syndrome

Introduction Fat embolism (FE) induced by intravenous Triolein (T) injection in an experimental rat model has been shown to result in severe pulmonary damage, septal arterial inflammation, and eventually fibrosis. This tissue response appears to be biphasic in nature with a peak at 48 hours. Fat droplets were also seen in the brains and the retina of the same rats. The current study was carried out to determine if FE in our model was also associated with fat droplets in the aorta at 48 hours. Materials and Methods 26 Sprague‐Dawley rats (250–330g) were divided into two groups (N=13 each) receiving either 0.2mg intravenous T (0.2 ml) or the same volume of saline. All animals were euthanized 48 hours later. Aortas were isolated, snap frozen and processed for cryosectioning. Sections were stained for Oil‐red‐O. Sections were imaged at 100× magnification and photographed by two pathologists unaware of their identity. Two photographs were taken for each aorta section. The fat droplets in each photograph were quantitatively evaluated by one independent observer and statistically compared utilizing a student T‐test. Results The aortas of the control group exhibited fat droplets in the media of 4 of the 8 vessels considered. These droplets were present in only limited sections of the vessels, were small in size, and close to the fat plaques of the nearby adventitia. The adventitia plaques were present in the aorta of all the rats including those without droplets in the media. Those fat droplets were mostly small and similar in their dimension. On the other hand, 7 of the 8 T treated rats exhibited a variable but usually large number of droplets, often involving the entire section of the aorta. Adventitia plaques were similar in number and shape to those of the control and were present in all the sections. Few large droplets mostly close to the media were also observed. The difference of droplets presence in the two groups was quantitatively significant with an average of 10.625 +/− 1.369 SEM for the T injected rats versus 2.500 +/− 0.7906 SEM for the controls (P < 0.0009). No statistically significant difference was seen for the adventitial plaques of the two groups. Conclusion While fat deposition is a nonspecific finding, the aorta sections of T injected rats showed an increased presence of fat in the media. Such an increase was also seen in lungs and brains. While FE appears to induce a marked inflammatory response within the lungs already at 48 hours, the aortas, like the brains do not seem to reciprocate such lung inflammatory developments. As the tissue reaction with the lungs is biphasic, the aorta reaction like that for the brain is markedly different with no signs of inflammation. Further studies are necessary to ascertain whether the inflammatory changes may appear in the aortas over a longer period of time. Support or Funding Information Catherine T Geldmacher Foundation, Saint Louis, MO. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .