Intense vascular sprouting from rat femoral vein induced by prostaglandins E1 and E2

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Abstract
The formation of new capillaries from the rat femoral vein was specifically explored to assess whether venous vessels of this caliber may participate in the process of angiogenesis. Prostaglandins of the E series (PGE1 and PGE2) were administered into the soft connective tissue surrounding the rat femoral vessels as angiogenic inducers. In these conditions, between 2 and 7 days, a great number of new capillaries were observed in the media of the femoral vein, arising from the endothelial cells (EC) in the intima. The events of the capillary growth from the femoral vein included EC activation, local degradation of the basal membrane followed by migration and proliferation of EC, solid sprout formation with posterior canalization, development of a new basal membrane, and appearance of pericytes around the new capillary. Although numerous vascular buds were also observed arising from the small venules and capillaries in the periadventitial tissues, they were separated at first from those in the media of the femoral vein by the venous adventitia. Later, connections were observed between both newly formed microcirculations. The present study shows the capacity of PGE1 and PGE2 in the extravascular position of inducing capillary sprouting from veins. Furthermore, the observations provide greater evidence that vessels with characteristics similar to those of the rat femoral vein may contribute to angiogenesis, on occasion with an intense neovascularization. This fact may be of interest for the establishment of a functional circulation after angiogenesis by anastomoses of the new capillaries with those arising from pre-existing vessels of greater caliber than the venules.