Omentum facilitates liver regeneration.
OBJECTIVE
To investigate the mechanism of liver regeneration induced by fusing the omentum to a small traumatic injury created in the liver. We studied three groups of rats. In one group the rats were omentectomized; in another group the omentum was left in situ and was not activated, and in the third group the omentum was activated by polydextran particles.


METHODS
We pre-activated the omentum by injecting polydextran particles and then made a small wedge wound in the rat liver to allow the omentum to fuse to the wound. We monitored the regeneration of the liver by determining the ratio of liver weight/body weight, by histological evaluation (including immune staining for cytokeratin-19, an oval cell marker), and by testing for developmental gene activation using reverse transcription polymerase chain reaction (RT-PCR).


RESULTS
There was no liver regeneration in the omentectomized rats, nor was there significant regeneration when the omentum was not activated, even though in this instance the omentum had fused with the liver. In contrast, the liver in the rats with the activated omentum expanded to a size 50% greater than the original, and there was histologically an interlying tissue between the wounded liver and the activated omentum in which bile ducts, containing cytokeratin-19 positive oval cells, extended from the wound edge. In this interlying tissue, oval cells were abundant and appeared to proliferate to form new liver tissue. In rats pre-treated with drugs that inhibited hepatocyte growth, liver proliferation was ongoing, indicating that regeneration of the liver was the result of oval cell expansion.


CONCLUSIONS
Activated omentum facilitates liver regeneration following injury by a mechanism that depends largely on oval cell proliferation.
Singh
Ashok K
AK
Department of Medicine, Stroger Hospital of Cook County, 637 South Wood St, Durand Bldg 2nd Floor, Chicago IL 60612, United States. singhashok@comcast.net
Pancholi
Nishit
N
Patel
Jilpa
J
Litbarg
Natalia O
NO
Gudehithlu
Krishnamurthy P
KP
Sethupathi
Perianna
P
Kraus
Mark
M
Dunea
George
G
Arruda
Jose Al
JA
D000818:Animals; D001835:Body Weight; D017931:DNA Primers; D003911:Dextrans / Q000494:pharmacology; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D007700:Kinetics; D008099:Liver / Q000166:cytology / Q000293:injuries; D008115:Liver Regeneration / Q000502:physiology*; D008297:Male; D009852:Omentum / Q000187:drug effects / Q000502:physiology* / Q000601:surgery; D009929:Organ Size; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000509:alpha-Fetoproteins / Q000235:genetics
D017931:DNA Primers; D003911:Dextrans; D012333:RNA, Messenger; D000509:alpha-Fetoproteins