Function and structure of pressurized and perfused porcine carotid arteries: effects of in vitro balloon angioplasty

Abstract

In this report we describe the application of an in vitro pressure-perfusion system for study of functional/structural changes after in vitro balloon dilation injury. Pig carotid arteries were perfused at P = 100 mm Hg and Q = 100 ml/min, balloon angioplastied (BA), and cultured under these hemodynamic conditions for 4 or 8 days (n = 5 BA and 6 controls for each time point). To assess endothelial function, outer diameter changes in response to bradykinin (BK) were measured daily. Remodeling was determined from the shift in pressure-passive diameter relation, as obtained after papaverine addition. Arterial samples were processed for histology. Control arteries showed spontaneous tone, BK-induced relaxation, and inward remodeling that was more pronounced at day 8 (ratio end-to-start passive diameter at P = 100 mm Hg, 0.69 +/- 0.04; P < 0.001) than at day 4 (0.85 +/- 0.03, P = 0.03). Intimal hyperplasia was detectable in these control vessels at day 8 with accumulation of alpha-smooth muscle actin-positive cells around the lumen. Angioplasty caused ruptures and dissections and abolished tone that returned after 5 days of perfusion along with BK-dependent relaxation. No significant inward remodeling or intimal hyperplasia was observed at day 8 after angioplasty. Thus, BA inhibits remodeling, which occurs after in vitro perfusion of conductance arteries.

Figure 1.

A: Photograph of culture chamber with pig carotid artery dilated at day 1 and perfused until day 8. Note the balloon-dilated part in the middle of the arterial segment (bracket). B: Scheme of perfusion system; arrows indicate the direction of flow as set by the pump (Q). Pressure is imposed at P. The whole setup was placed in an incubator at 37°C.

Figure 2.

The active diameter, normalized to the diameter during papaverin addition as a function of day number. Results are shown for the 8-day group, results for the 4-day group are comparable for relevant time points. Pre-PAP, active diameter before relaxation with papaverin; post-PAP, passive diameter after relaxation with papaverin. At all time points after BA, the diameter in the BA group was significantly greater than diameters in the control group: *, P < 0.05 control versus BA.

Figure 3.

Normalized relaxation as a function of number of days of perfusion. Data are superimposed on those of Figure 2 ▶ . In the control group significant changes in diameter after BK were measured at all time points. In the BA group, significant changes were found only at days 1 (immediately before BA), 7, and 8. Furthermore, at all time points after BA, a significant difference between groups was found: *, P < 0.05 control versus BA relaxation. Error bars refer to relaxation data.

Figure 4.

Pressure-passive diameter relationship at start (day 1), and after 4 or 8 days of perfusion. Top, control; bottom, BA. #, P < 0.05 day 1 versus day 4; *, P < 0.05 day 1 versus day 8.

Figure 5.

Normalized passive and active diameter at day 8 of culture versus DR in the BA group.

Figure 6.

Photomicrographs of histological sections: A and B, control day 4; C and D, control day 8; E and F, BA day 4; G and H, BA day 8 (all H&E); I: control day 4, anti-α-SMA. Inset in D: Corresponding EvG stain. Boxed areas in A, C, E, and G refer to magnifications in B, D, F, and H. Scale bars: 500 μm (A, C, E, G); 50 μm (B, D, F, H); 100 μm (I). Note the IH in D and the damage induced by BA in E (both indicated by arrows).

Figure 7.

IH (top) and medial (middle) and adventitial (bottom) thickness lumen ratios of perfused arteries for both groups and time points: *, P < 0.05 BA versus control.