Selective Inhibition of Angiogenesis in Small Blood Vessels and Decrease in Vessel Diameter throughout the Vascular Tree by Triamcinolone Acetonide

PURPOSE. To quantify the effects of the steroid triamcinolone acetonide (TA) on branching morphology within the angiogenic microvascular tree of the chorioallantoic membrane (CAM) of quail embryos. METHODS. Increasing concentrations of TA (0-16 ng/mL) were applied topically on embryonic day (E) 7 to the chorioallantoic membrane (CAM) of quail embryos cultured in petri dishes and incubated for an additional 24 or 48 hours until fixation. Binary (black/white) microscopic images of arterial end points were quantified by generational analysis of vessel branching (VESGEN) software to obtain major vascular parameters that include vessel diameter (D v ), fractal dimension (D f ), tortuosity (T v ), and densities of vessel area, length, number, and branch point (A v , L v , N v , and Br v ). For assessment of specific changes in vascular morphology induced by TA, the VESGEN software automatically segmented the vascular tree into branching generations (G 1 ...G 10 ) according to changes in vessel diameter and branching. RESULTS. Vessel density decreased significantly up to 34% as the function of increasing concentration of TA according to A v , L v , Br v , N v , and D f . TA selectively inhibited the growth of new, small vessels because L v decreased from 13.14 ± 0.61 cm/cm 2 for controls to 8.012 ± 0.82 cm/cm 2 at 16 ng TA/mL in smaller branching generations (G 7 -G 10 ) and for N v from 473.83 ± 29.85 cm -2 to 302.32 ± 33.09 cm -2 . In contrast, vessel diameter (D v ) decreased throughout the vascular tree (G 1 -G 10 ). CONCLUSIONS. By VESGEN analysis, TA selectively inhibited the angiogenesis of smaller blood vessels, but decreased the vessel diameter of all vessels within the vascular tree.