Omentum facilitates liver regeneration.
ABSTRACT 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.
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).
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.
Activated omentum facilitates liver regeneration following injury by a mechanism that depends largely on oval cell proliferation.
- SourceAvailable from: dunkanesthesia.infoNew England Journal of Medicine 05/2007; 356(15):1545-59. · 51.66 Impact Factor
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ABSTRACT: A lipid material extracted from the omentum has previously been shown to contain a potent angiogenetic activator (20), capable of creating intense vasoproliferation in traumatized tissues (19). This study was undertaken to analyze the efficacy of local administration of this omental lipid fraction on osseous vascularization and bone repair. An osteoperiosteal segmental femoral defect in the rat was replaced by a demineralized allogenic bone graft exposed to continuous local delivery of omental lipid via an implanted miniosmotic pump. Saline solution delivered in the same way served as a control. Neovascularization and bone formation in the transplant were quantitatively evaluated by means of dynamic radioisotopic bone imaging, radiographic photodensitometry, microangiography, and biomechanical testing. Compared with the control group, the omental lipid angiogenic fraction-treated specimens showed an 80% overall increase (p less than 0.001) in bone density as well as a twofold increase (p less than 0.001) in regional blood perfusion, maximal at 2 weeks following surgery. At 12 weeks, biomechanical testing demonstrated significantly higher union rate (p less than 0.05) and strength (p less than 0.01) in the treated specimens as compared with the controls. These data demonstrate that the omental lipid fraction factor has potent angiogenic properties that enhance bone blood perfusion and bone regeneration.Journal of Orthopaedic Research 02/1989; 7(2):157-69. · 2.88 Impact Factor
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ABSTRACT: The concept that the liver contains epithelial cells that share some of the major properties of stem cells of the well-characterized, stem cell-fed lineages found in bone marrow, intestinal epithelium, and epidermis is now well supported. Nevertheless, the population dynamics of the major types of liver epithelial cells, hepatocytes, and bile epithelia display a striking difference from the population dynamics of the classic stem cell systems. The focus of this review is on recent studies of the activation and expansion of liver stem cells in vivo and the role these cells may play in regeneration of the liver. The requirement for a selective and sustained expression of growth factors during the early stages of stem cell activation is highlighted. In addition, results are presented supporting the hypothesis that after loss of liver mass, both the quiescent stem cells as well as the residual differentiated hepatocytes and bile duct epithelial cells are activated to proliferate. However, significant contribution of the stem cells to the regeneration process only occurs under circumstances in which the residual differentiated cells are functionally compromised and/or cannot proliferate.The FASEB Journal 10/1996; 10(11):1249-56. · 5.70 Impact Factor