Renal Effect of Triolein in a Rat Model of Fat Embolism Syndrome (FES)
Ingrid Hsiung1, Chang Qin1, Alan Poisner2, Betty Herndon1, Timothy Quinn1, Agostino Molteni1
1UMKC School of Medicine, 2University of Kansas
RESULTS
INTRODUCTION
FES is a respiratory process which is observed after fractures of the long bones
or surgical procedures, such as repair of the spine, liposuction, or extensive
surgery in obese patients. The clinical process manifests itself as acute
respiratory distress syndrome (ARDS), pulmonary hypertension, presence of
petechial hemorrhages, and mental confusion.(1, 2)
We have previously reported in an experimental model of fat embolism
obtained by intravenous caudal injection of triolein, pulmonary vasculitis with
presence of fat in the lungs up to 10 weeks following triolein injection. Staining
of the lungs with trichrome and smooth muscle actin also evidenced severe
fibrosis.(2, 3, 4)
The process is not limited to the lungs and in a preliminary presentation,
we showed that damage is also observed in the renal arteries, with fat droplets
in the glomeruli, especially after 48h and 96h, and vasoconstriction of small
caliber arteries. Renin was also increased, particularly in the cells of the
juxtaglomerular apparatus (JGA) and in the renal tubules at the same interval
time. (5) (Figures 1, 2, 3).
The renin-angiotensin system (RAS) is involved in the pathogenesis of the
pulmonary damage since rats receiving the angiotensin 1 converting enzyme
(ACE) inhibitor, captopril, or the angiotensin 1 receptor blocker (ARB), losartan,
protects the organ from the fat-induced damage both in acute phrase or when
the pathological process persists up to 10 weeks. (7)
This study reports the renal damage occurring following triolein
administration in the kidneys of rats sacrificed a rather long time post-injection
(44 days).
A
B
Figure 1. Representative sample from the previous study (2) of kidneys
of the rats sacrificed at 48h. H&E (1A) and renin (1B) stains at 400x.
Hemorrhages and fat droplets are present in the glomeruli, while small caliber
arteries show significant thickening of the media, reduction of lumen patency,
and mild adventitial inflammation (1A, 1B). Renin is evident in the JGA (1B).
This study shows that triolein not only damages the lungs, but also the kidneys
up to six weeks post-embolization. Only lungs, however, had fat droplets at this
interval time. A slight, but not statistically significant, increase in renal damage
was observed in the kidneys of the rats receiving both triolein and LPS. LPS,
when given alone, did not produce damage, contrary to what we observed in
the pulmonary study. (6)
Whether the RAS role in pathogenesis of pulmonary hypertension
originates directly in this organ or it is consequent to the renal hypersecretion
renin, or both, is still an open question. (6)
The increased glomerular secretion of renin underlines its role in the
pathogenesis of FES, therefore suggesting that the renal damage should also be
taken into consideration when patients presenting this condition are clinically
evaluated.
REFERENCES
1. Roberts CS, Gleis GE, Seligson D. FES diagnosis and treatment of complications. In: Browner
Figure 2. Effect of Triolein on Patency of Renal Vessels.
Despite significant reduction in patency at 48h, a vascular return to
normal patency is seen at a late interval time (11days).
A
B
C
D
MATERIALS & METHODS
Unanaesthetized Sprague-Dawley rats (280-300g) supplied by Harlan
Laboratories, Indianapolis, IN, received a dose of 0.2mL of pure glyceryl
trioleate in the caudal vein (n=18). Controls (n=18) received 0.2mL of saline at
the same site. This dose was selected from results of previous experiments. (2)
Food and water were given ad libitum and the rats’ weight and behavior
checked weekly. The Animal Care Committee of our Institution approved the
above protocol. Six weeks post-injection, each of the groups received i.p. LPS
(3mg/kg) (n = 9) or saline (n = 9). Purpose of LPS treatment was to check if a
small second injury (2nd hit) could aggravate the damage inflicted to the
animals. Two days later at necropsy, kidneys were collected, weighed, fixed in
formalin, and stained for H&E and renin. The histological organ damage was
quantitatively scored and the lumen patency of the renal small-caliber cortical
arteries evaluated by measuring the ratio of the internal diameter divided by
the external diameter of the media.
Figure 4. Lumen patency of the cortical renal
arteries of the saline and the triolein treated
groups.
CONCLUSIONS
Figure 3. Representative samples of renal sections at 400x of
all the treatment groups and stained for renin: saline + saline
(3A), saline + LPS (3B) triolein + saline (3C) triolein + LPS (3D).
Figure 5. Percentage of glomeruli stained for
renin in the JGA of the various groups.
Triolein caused severe glomerular damage with
basal membrane thickening, and presence of
crescents and hemorrhages.
However, no fat globules were observed at
this time, contrary to the previous study where
fat droplets were present in the glomeruli up to
11 days.
Besides the increased frequency, the intensity
of the stain is more severe in the group of rats
receiving both triolein and LPS. Glomerular
crescents and thickening of the basal
membrane is also more severe in this group
(Figure 3).
Cortical artery vasculitis with reduced
lumen patency was prominent in both groups
of triolein-treated rats (Figure 4). Renin staining
was seen in 32% of glomeruli of rats receiving
saline, 53% of glomeruli of rats treated with
LPS, 54% of glomeruli of rats treated with
triolein alone, and 76% of those receiving both
triolein and LPS.
BD, Jupiter JB, Levine AM, Tafton PG, Krettek C, editors: Skeletal Trauma. 4th ed. Philadelphia,
PA: WB Saunders; 2009: 515-588.
2. Akhtar S. Fat embolism. Anesthesiol Clin. 2009; 27: 533-550.
3. McIff T, Poisner A, Herndon B, Lankachandra K, Schutt S, Molteni A. Fat Embolism:
evolution of histopathological changes in the rat lung. Journal of orthopaedic Research 2010;
28: 191-194.
4. Poisner A, Adler F, Uhal B, McIff T, Schroepper JP, Meher A, Herndon BL, Lankachandra KM,
and Molteni A. Persistent and progressive fibrotic changes in a model of fat embolism.
Journal of Trauma 2012; 72: 992-998.
5. Patel S, Adler F, McIff T, Poisner A, Herndon B, Quinn T, and Molteni A. Triolein-induced
renal arterial vasoconstriction and its reversal in a rat model. The FASEB Journal 2009; (17)5:
A-1199.
6. Poisner AM, Herndon B, Lankachandra K, Likitsup A, Al Hariri A, Kesh S, and Molteni A. Fat
embolism sensitizes rats to a “second hit” with LPS: an animal model of pulmonary fibrosis.
Journal of Trauma and Acute Surgical Care: in press 2014.
7. McIff T, Poisner A, Herndon B, Lankachandra K, Molteni A, Adler F. Mitigating effects of
captopril and losartan on lung histopathology in experimental fat embolism in the rat. Journal
of Trauma 2011; 70(5): 1186-191.
CREDITS/DISCLOSURE
The authors would like to thank the laboratory of histopathology at Truman Medical Center,
Mr. Joe Moran at the UMKC office of medical marketing, communications, and illustrations,
and the Geldmacher foundation (Dr. Gary Salzman) for the support of this project.