male sprague - dawley rats weighing 550 - 600 g are purchased from harlan ( indianapolis , in , usa ) .
house rats under conventional conditions , fed standard rat chow and water ad libitum .  
anesthetize rat with isoflurane ( 2% ) and ketamine ( 25 mg / kg ) . under microscopic view , perform an upper median mini - laparotomy to expose the infrarenal aorta .  
dissect the abdominal aorta from the surrounding tissue , from the level of the renal arteries down to the bifurcation .
open the aorta with a small transverse incision and flush the aorta with heparin ( 200 units ) .
the aortic endothelium is denuded by the passage of a 2-french fogarty arterial embolectomy catheter ( baxter healthcare , deerfield , il , usa ) .  
use any human stent size between 8 mm and 12 mm in length , and 2.5mm-3 mm in diameter .
caution : the diameter of the stent should not exceed the vessel diameter by more than 10% to avoid pre- and post - stent stenosis .
the small aortic incision is closed with 9 - 0 prolene sutures ( ethicon , norderstedt , germany ) .
close the abdominal incision in layers with 4 - 0 vicryl running sutures ( ethicon , norderstedt , germany ) .
the skin sutures should still be removed within 7 - 14 days even when viacryl is used .
animals received carprofen ( 6mg / kg ) intraoperatively , and metamizol for 7 more days in the drinking water .
oct images are obtained with the m2 oct imaging system ( lightlab imaging , inc . ,
imagewire is an imaging probe to deliver the light to the tissue and collect the signals .
the imagewire consists of 0.006"(0.15 mm ) fiber - optic core , inside a sheath with a maximum o.d . of 0.019 " ( 0.48 mm ) .  
anesthetize rat with isoflurane ( 2% ) and ketamine ( 25 mg / kg ) . under microscopic view , perform a median redo laparotomy to expose the infrarenal aorta .  
perform a transverse arteriotomy at the distal end of the aorta , flush with 1ml pbs using a 28 g catheter and insert the oct catheter and forward it into the aorta .  
motorized pullback oct imaging is performed at a pullback rate of 1.0 mm per second .  
acquire images at 15 frames per second ; images are displayed with a color look - up table and digitally archived .  
close the abdominal and incisions with 4 - 0 vicryl running sutures ( ethicon , norderstedt , germany ) .
the skin sutures should still be removed within 7 - 14 days even when viacryl is used .  
oct measurements are performed using the lightlab oct imaging proprietary software with a rat - based interface .  
calibrate the system to the reflection of the oct imaging wire , which is the standard calibration technique for this system .
trace lumen and stent cross sectional areas ( csa ) manually at each 1.0 mm intervals .   calculate plaque cross sectional area as stent csa subtracted from the lumen csa . calculate percent plaque area as plaque csa divided by stent csa ( % ) .
histology reveals intimal hyperplasia with high density of spindle - shaped cells and only few mononuclear inflammation cells .
after 6 weeks , stents are completely covered with neointimal granulation tissue and the plaque csa measures 1.30.4 mm in a 2.5 mm stent .
figure 1 : oct ( a ) and histological ( b ; magnification 16x ) images of the stent 6 weeks after deployment .
male sprague - dawley rats weighing 550 - 600 g are purchased from harlan ( indianapolis , in , usa ) .
house rats under conventional conditions , fed standard rat chow and water ad libitum .  
anesthetize rat with isoflurane ( 2% ) and ketamine ( 25 mg / kg ) . under microscopic view , perform an upper median mini - laparotomy to expose the infrarenal aorta .  
dissect the abdominal aorta from the surrounding tissue , from the level of the renal arteries down to the bifurcation .
open the aorta with a small transverse incision and flush the aorta with heparin ( 200 units ) .
the aortic endothelium is denuded by the passage of a 2-french fogarty arterial embolectomy catheter ( baxter healthcare , deerfield , il , usa ) .  
use any human stent size between 8 mm and 12 mm in length , and 2.5mm-3 mm in diameter .
caution : the diameter of the stent should not exceed the vessel diameter by more than 10% to avoid pre- and post - stent stenosis .
the small aortic incision is closed with 9 - 0 prolene sutures ( ethicon , norderstedt , germany ) .
close the abdominal incision in layers with 4 - 0 vicryl running sutures ( ethicon , norderstedt , germany ) .
the skin sutures should still be removed within 7 - 14 days even when viacryl is used .
animals received carprofen ( 6mg / kg ) intraoperatively , and metamizol for 7 more days in the drinking water .
oct images are obtained with the m2 oct imaging system ( lightlab imaging , inc . , westford , ma , usa ) .
imagewire is an imaging probe to deliver the light to the tissue and collect the signals .
the imagewire consists of 0.006"(0.15 mm ) fiber - optic core , inside a sheath with a maximum o.d . of 0.019 " ( 0.48 mm ) .  
anesthetize rat with isoflurane ( 2% ) and ketamine ( 25 mg / kg ) . under microscopic view , perform a median redo laparotomy to expose the infrarenal aorta .  
perform a transverse arteriotomy at the distal end of the aorta , flush with 1ml pbs using a 28 g catheter and insert the oct catheter and forward it into the aorta .  
motorized pullback oct imaging is performed at a pullback rate of 1.0 mm per second .  
acquire images at 15 frames per second ; images are displayed with a color look - up table and digitally archived .  
close the abdominal and incisions with 4 - 0 vicryl running sutures ( ethicon , norderstedt , germany ) .
the skin sutures should still be removed within 7 - 14 days even when viacryl is used .  
oct measurements are performed using the lightlab oct imaging proprietary software with a rat - based interface .  
calibrate the system to the reflection of the oct imaging wire , which is the standard calibration technique for this system .
trace lumen and stent cross sectional areas ( csa ) manually at each 1.0 mm intervals .   calculate plaque cross sectional area as stent csa subtracted from the lumen csa . calculate percent plaque area as plaque csa divided by stent csa ( % ) . calculate average percent plaque areas .
histology reveals intimal hyperplasia with high density of spindle - shaped cells and only few mononuclear inflammation cells .
after 6 weeks , stents are completely covered with neointimal granulation tissue and the plaque csa measures 1.30.4 mm in a 2.5 mm stent .
figure 1 : oct ( a ) and histological ( b ; magnification 16x ) images of the stent 6 weeks after deployment .
although the rabbit iliac artery and the pig coronary artery models are the most frequently used for stent placement , a combination of radiological and surgical equipment is required , animal housing capacity is limited , and the costs of purchase are high . limitations of the rat stent model is the necessary use of specifically designed stents for rats , the metal - to - artery ratio resulting in more vascular injury , and the artificially high incidence of thrombosis .
the rat stenting model is a simple , inexpensive , rapid , and accurate preclinical model .
after the initial report of direct stenting of the rat aorta by lowe et al . , feasibility and suitability of this model for the evaluation of the pathophysiology of in - stent restenosis has been thoroughly shown .
the diameter of the rat aorta is adequate to allow expansion of commercially available stents without disruption of the physiologic vessel architecture .
it has been shown that pathophysiological mechanisms , such as thrombus formation , inflammation , and smc proliferation , develop in these rat models as they do in the rabbit and pig
the penetration depth is only 1.5 - 2 mm , but its resolution is an order of magnitude greater than that of intravascular ultrasound ( ivus ) .
multiple studies comparing oct with ivus conclude that oct is currently the preferred technique to evaluate neointimal hyperplasia after stent implantation . especially in small animals with small vessel diameters ,
the high resolution of oct renders it the best imaging modality for the evaluation of restenosis . in summary
, this video shows that ( 1 ) rat aortic stenting is easily feasible , ( 2 ) rat abdominal aorta stenting is suitable for testing commercially manufactured stents and ( 3 ) oct imaging is an accurate and elegant technique for longitudinal monitoring of in - stent restenosis .
all rats were housed in the animal care facility at stanford university medical center ( stanford , ca ) , under standard temperature , humidity , and lighting conditions , and were provided rat chow and water ad libitum .
the investigation conformed to the guide for the care and use of laboratory animals published by the us national institutes of health ( nih publication no .
the study protocol was approved by the administrative panel on laboratory animal care , stanford university .
 preclinical models of restenosis are essential to unravel the pathophysiological processes that lead to in - stent restenosis and to optimize existing and future drug - eluting stents.a variety of antibodies and transgenic and knockout strains are available in rats . 
 consequently , a model for in - stent restenosis in the rat would be convenient for pathobiological and pathophysiological studies . in this video , 
 we present the full procedure and pit - falls of a rat stent model suitable for high throughput stent research . 
 we will show the surgical procedure of stent deployment , and the assessment of in - stent restenosis using the most elegant technique of oct ( optical coherence tomography ) . 
 this technique provides high accuracy in assessing plaque csas ( cross section areas ) and correlates well with histological sections , which require special and time consuming embedding and sectioning techniques . 
 oct imaging further allows longitudinal monitoring of the development of in - stent restenosis within the same animal compared to one - time snapshots using histology . 
Protocol
Aortic Stent Deployment
Optical Coherence Tomography (OCT) Imaging
Analyzing OCT images
Validation of the OCT technique
Discussion
Disclosures