Ultrasound-guided percutaneous delivery of tissue-engineered endothelial cells to the adventitia of stented arteries controls the response to vascular injury in a porcine model

Abstract

Objective: High restenosis rates are a limitation of peripheral vascular interventions. Previous studies have shown that surgical implantation of a tissue-engineered endothelium onto the adventitia surface of injured vessels regulates vascular repair. In the present study, we developed a particulate formulation of tissue-engineered endothelium and a method to deliver the formulation perivascular to injured blood vessels using a percutaneous, minimally invasive technique.

Methods: Stainless steel stents were implanted in 18 balloon-injured femoral arteries of nine domestic swine, followed by ultrasound-guided percutaneous perivascular injection of gelatin particles containing cultured allogeneic porcine aortic endothelial cells (PAE). Controls received injections of empty particles (matrix) or no perivascular injection (sham) after stent deployment. Animals were sacrificed after 90 days.

Results: Angiographic analysis revealed a significantly greater lumen diameter in the stented segments of arteries treated with PAE/matrix (4.72 ± 0.12 mm) compared with matrix (4.01 ± 0.20 mm) or sham (4.03 ± 0.16 mm) controls (P < .05). Similarly, histologic analysis revealed that PAE/matrix-treated arteries had the greatest lumen area (20.4 ± 0.7 mm(2); P < .05) compared with controls (16.1 ± 0.9 mm(2) and 17.1 ± 1.0 mm(2) for sham and matrix controls, respectively) and the smallest intimal area (3.3 ± 0.4 mm(2); P < .05) compared with controls (6.2 ± 0.5 mm(2) and 4.4 ± 0.5 mm(2) for sham and matrix controls, respectively). Overall, PAE-treated arteries had a 33% to 50% decrease in percent occlusion (P < .05) compared with controls. Histopathological analysis revealed fewer leukocytes present in the intima in the PAE/matrix group compared with control groups, suggesting that the biological effects were in part due to inhibition of the inflammatory phase of the vascular response to injury.

Conclusions: Minimally invasive, perivascular delivery of PAE/matrix to stented arteries was performed safely using ultrasound-guided percutaneous injections and significantly decreased stenosis. Application at the time of or subsequent to peripheral interventions may decrease clinical restenosis rates.

Fig 1

Characterization of porcine aortic endothelial cells (PAE) on gelatin particles. A, PAE cultured on particles followed a growth pattern similar to cells grown on sponges or standard tissue culture plastic. B, The preservation of endothelial cell integrity was determined by platelet endothelial cell adhesion molecule (PECAM) staining. Green cells indicate positive PECAM staining; blue indicates nuclei. C, Suppression of platelet factor-4 (PF-4) induced inflammatory and thrombotic gene expression on human aortic endothelial cells (HAE) by PAE/matrix-conditioned media. ICAM-1, Intercellular adhesion molecule-1; IL-8, interleukin-8; TF, tissue factor; VCAM-1, vascular cell adhesion molecule-1. *P < .05 compared with PF-4 and control media.

Fig 2

Images depict ultrasound-guided percutaneous delivery of porcine aortic endothelial cells (PAE)/matrix adjacent to perivascular tissue of femoral arteries (A) at the time of injection and (B) postinjection. C and D, Delivery site adjacent to the femoral artery was confirmed after femoral cutdown. Stent struts are visible within the artery, which is encapsulated with injected methyl blue-stained gelatin particles. E, Histologic section of unstented femoral artery stained with Mayer's hematoxylin solution confirms delivery of particles adjacent to perivascular tissue. F and G, Sections of unstented femoral arteries stained with CD31 identifies retention of PAE within the particles after percutaneous injection adjacent to the perivascular tissue.

Fig 3

Representative day-90 angiograms (A) and photomicrographs of Verhoeff's elastin-stained arterial cross-sections (B). Comparison of the angiograms shows an increase in stenosis in the stented region of control arteries (left and middle panels, black arrows) compared with arteries treated with porcine aortic endothelial cells (PAE)/matrix (right panel). Histologic sections show significantly greater intimal area in control sham (left panel) and matrix (middle panel) arteries compared with arteries treated with perivascular PAE/matrix. I, Intima; L, lumen; M, media.

Fig 4

Bar graphs of tissue plane analysis. (A) Lumen area, *P< .05 compared with sham andmatrix control groups; (B) intimal area; (C) % occlusion; and (D) intimal thickness, §P < .05 compared with sham control group. There was no statistical difference between the sham and matrix control groups when comparing the proximal, mid, or distal planes. PAE, Porcine aortic endothelial cells.

Fig 5

Representative photomicrographs of hematoxylin and eosin-stained arterial cross-sections depict (A) stent endothelialization (arrows), (B) reduced hypocellularity in porcine aortic endothelial cells (PAE)/matrix group (dashed circle) compared with (C) control matrix group (dashed brackets), (D) minimal inflammation associated with stent struts (arrow) in PAE/matrix group. E, Representative photomicrographs of CD45-stained arterial cross-sections depict no positive staining in the intima of PAE/matrix arteries (top panel) and moderate positive staining in the control matrix (middle panel) and sham (bottom panel) groups. Arrows point to positive CD45 staining. F, Bar graph demonstrates fewer CD45-positive leukocytes (severity score = 0 ± 0) present in the intima of day 90 PAE/matrix animals compared with control matrix (severity score = 1 ± 0) and sham (severity score = 2 ± 0.8) groups.