Jessen Schiebout 
Marquette University
Milwaukee, WI
Faculty Mentor: Dr. Thomas Eddinger 

Sialastic cuff placement on the Rabbit Carotid Artery and Intimal Thickening: Intimal thickening, hyperplasia of an artery, usually progresses to further health problems. Intimal thickening, in part, is the migration of subendothelial smooth muscle cells past the intima and into the lumen, where they begin to grow and divide. Continued growth slowly decreases the diameter of the artery, occludes blood flow, and leads to arteriosclerosis. The exact causes of intimal thickening in nature have yet to be determined. Consequently, intimal thickening is studied so that we may learn its causes and methods of prevention.

Other laboratories have reported that placement of a silicone collar around the carotid artery of a rabbit leads to significant intimal thickening. My initial goal is to verify and reproduce these results so we have a reliable method. Then it will be possible to investigate the intimal smooth muscle cells and determine potential causes and prevention. The silicone collar method is preferable to balloon catheterization and electrical shock methods because it avoids direct injury to the vessel wall. The cuff placement procedure is also beneficial because it causes relatively fast changes.

New Zealand White rabbits between 1.8 and 2.6 Kg had both right and left carotid arteries equally exposed and manipulated. Silastic tubing with a 1.6 mm inner diameter and 1.5 cm long was placed around the left carotid arteries. The animals were sacrificed 14 days later and the carotid arteries were removed, frozen, and thin slices were mounted on microscope slides. The slides were stained and viewed microscopically.

Six of nine rabbits displayed some degree of intimal thickening after the cuff placement procedure. To objectify and normalize the carotid results, a ratio of the area of intimal thickening to the area of the media was taken. The ratios of intimal thickening range from 0.112 to 0.303

In conclusion, intimal thickening was induced. However, there seems to be no relation of intimal thickening to size of the rabbit, artery manipulation, sex, or ties on the cuff. 66% of the rabbits showed intimal thickening and 33% showed a nearly 0.2 or higher intimal thickening to media ratio. This study corroborates previous findings and confirms that insertion of a silicone cuff, along with the vascular damage from the procedure, is sufficient to induce intimal thickening in rabbit carotid arteries. This method of inducing intimal thickening can be very useful for the study of intimal smooth muscle cells.

Smooth Muscle Cell Lengths in the Rat: Smooth muscle cell lengths were measured to determine whether all smooth muscle cell sizes are similar. Smooth muscle cells from the rat were removed and were macerated. Smooth muscle cells were obtained, photographed, and measured. The average length of Aorta smooth muscle cells is 97 microns. The average length for the carotid is 101 microns. However, all of the other cell lengths are about 250 microns or more. The undistended antrum, bladder, body, and fundus were shorter on average than the distended. Therefore, the distended lengths are probably a more accurate measurement for in vivo cell lengths. Different groups of smooth muscle cells differ in function. Vascular cells maintain a relatively isometric length; however, bladder and stomach cells contract and stretch over a greater length. This led to the hypothesis that different smooth muscle cells would have different in vivo lengths. The vascular smooth muscle cells are significantly shorter than the gastrointestinal and bladder cells. All smooth muscle cells are not the same, as to be expected due to the different functions of each cell type.