Angiogenic factor: a possible mechanism for neovascularization produced by omental pedicles.

To determine possible mechanisms by which omental pedicles protect bronchial anastomoses from ischemia, we studied the angiogenic potential of a lipid extract of omentum. A rabbit cornea model was used to quantify neovascularization produced by methanol-chloroform extract of homogenized autologous omentum or perirenal fat. In 22 anesthetized rabbits, 10 microliters of omental lipid extract was injected into the cornea. In each animal the opposite eye was used as a control and was injected with a similar volume of extract prepared from perirenal fat. The side of injection of autologous omental fat was randomized and was not known to the investigator who assessed neovascularization on days 4, 7, 14, and 21 after injection. Neovascularization was recorded on microphotography and quantified by a point-counting method. Four days after injection, neovascularization in corneas injected with autologous omental fat was significantly (p less than 0.05) greater than in control corneas for all indices of neovascularization including total point count, which was three times greater than control. The angiogenic effect diminished with time, and by 21 days after injection corneal neovascularization was comparable for the two groups. Our results suggest that the lipid fraction of omentum has angiogenic activity that may stimulate neovascularization in ischemic tissues. Lack of sustained activity may be due to washout by neovessels or local tissue metabolism.