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

Abstract

IntroductionFat embolism (FE) resulting from intravenous triolein (T) injection in an experimental rat model has been shown to result in severe pulmonary damage, septal and arterial inflammation, and eventually fibrosis. This tissue response appears to be biphasic in nature with a peak at 48 hours. Fat droplets have previously been reported in the brains of patients suffering severe fat embolism syndrome (FES). The current study was carried out to determine if FE in our model was also associated with fat droplets in the brain at 48 hours.Materials and Methods26 Sprague‐Dawley rats (250–330g) were divided into two groups (N=13 each) receiving either 0.2 mg intravenous T or normal saline. All animals were euthanized under isoflurane anesthesia 48 hours later. Lungs and brains were isolated, snap‐frozen, and processed for cryosectioning. Sections were stained for oil red o and hematoxylin and eosin. Sections were imaged at 400x magnification and counted by two pathologists blinded to section identity. These counts were decoded by an independent observer and statistically compared utilizing a student's T‐test.ResultsThe brains of the control group exhibited fat droplets in 3 of the 12 brains considered. These droplets were small in size and primarily localized to the cerebral cortex with minimal associated parenchymal reaction. 10 of the 12 brains observed in the experimental group demonstrated fat droplets which were localized to the cerebral cortex, cortical arteries, and especially the meningeal arteries. These droplets were much larger and were associated with an appreciable vascular thickening within affected vessels. Lungs of the control group featured a small amount of small scattered fat droplets in the same 3 subjects while the lungs of the experimental group all featured large fat droplets with the expected septal and associated arterial damage pattern previously published.ConclusionsWhile fat deposition is a non‐specific finding, the difference in tissue response demonstrated in rat lungs and brains is evident. While FE appears to provoke a marked inflammatory response within the lungs even at 48 hours the brain does not appear to reciprocate this change. While the droplets noted within the experimental group are larger and more associated with a mild vessel response the parenchyma of the brain appears much less affected compared to the lungs within the same animal. As the tissue reaction within the lungs is biphasic and the observed changes within the brain differ significantly further studies are necessary to ascertain if said changes might not evolve over a longer period of time.Support or Funding InformationSupported by the 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.