|
Participation of angiogenesis from rat femoral veins in the neovascularization
of adjacent occluded arteries
J.F. Madrid1, L. Díaz-Flores2, R. Gutiérrez2,
H. Varela2, F. Valladares2, N. Rancel2 and F. Rodríguez2
1Department of Cell Biology and Morphological Sciences,
School of Medicine and Dentistry, University of the Basque Country, Leioa,
Vizcaya and 2Department of Anatomy and Pathology, Faculty of Medicine, University
of La Laguna, Tenerife, Canary Islands, Spain
Offprint requests to: Prof.
Lucio Díaz-Flores, C/ Emilio Serra y Fernández Moratín,
16, Santa Cruz de Tenerife, Islas Canarias, Spain
Summary. The neovascularization
of the arterial wall in human and experimental pathology has been demonstrated.
The occlusion of the of the rat femoral artery is a suitable model for the
study of these angiogenesis processes. Newly formed capillaries growing
into the arterial wall have been described in this model. The origin of
these ingrowing capillaries has been attribute to the preformed surrounding
venules and capillaries. The contribution of the adjacent femoral vein with
a supplementary population of vascular sprouts could also be possible. To
test this hypothesis in half of the occluded arteries, the adventitia was
removed from the side facing the femoral vein. Between 1 and 3 days after
surgery several alterations were found both in the endothelial cells and
the smooth muscle cells of the tunica media. Between 3 and 6 days, solid
or canalized endothelial sprouts were observed arising from the femoral
vein. By days 4 and 6, newly formed capillaries grew into the adventitia
and tunica media of the femoral artery. Some of them, penetrated the internal
elastic lamina. This microvascular penetration from the femoral vein was
more prominent in the area of the ostium of the collateral and when the
adventitia was removed. Some ingrowing capillaries were in continuity with
the endothelial cells of the arterial neointima. At days 7 and 8, regressing
capillaries were observed in the neomicro-vasculature network between artery
and vein, with a selective loss of the smaller vessels. From day 9 onwards,
fewer and larger vascular channels were present between the femoral vein
and the femoral artery. An arterial neolumen contained what appeared to
be circulating "fresh" blood. Quantitatively, the venous neocapillary
density increased from days 4 to 6 and then declined significantly by day
8. The arterial neocapillary density increased form days 4 to 8 and declined
significantly by day 12. Moreover, both densities were significantly greater
when the arterial adventitia was removed. The perfusion with barium solution
showed the presence of the contrast material in the newly formed vessels,
the lumen of the femoral vein, and the neolumen of the occluded arterial
segment. The present findings indicate that putative angiogenic molecules
released form the occluded arterial segment may reach the adjacent wall
of the vein inducing neovascularization from it. The vein vascular sprouts
are connected to the ingrowing capillaries in the occluded arterial wall
and to the neocapillaries form the preexisting pericytic microvasculature.
When the arterial adventitia were removed up to 2 times greater vein neocapillary's
density was observed suggesting an easily access of the putative angiogenic
factors to the vein. Histol Histopathol 13, 1-11 (1998)
Key words: Angiogenesis, Microcirculation,
Neo-vascularization, Arterial intimal thickening, Veins, Endothelial cells,
Smooth muscle cells, Pericytes
DOI: 10.14670/HH-13.1
|