A novel mouse model of stenting 43 Figure 5 Immunohistochemical staining showing inﬂammatory cells trapped in a transient thrombus and on the stented surface (arrowed) at 3 days (A), endothelial cells lining the lumen at 7 days (B), and smooth muscle cells of the media and neointima at 28 days post-stenting (C and D). Open triangles depict the IEL; ﬁlled triangles the external elastic lamina; and S denotes stent metal. Scale bar represents 100 mm. The presence of the coiled stent metal could potentially present a difﬁculty with analysis of sections using this model. However, the mean strut area of each section remains constant, as does the variability in neointima between sections. Thus, there is no signiﬁ- cant variation between sections, despite the eccentric lesion in relation to the spiral shape of the stent, meaning that the model is both reproducible and reliable. Mice are small, inexpensive, and easy to handle, making them ideal for use in disease models. Mice are also amenable to genetic manipulation and can be rendered susceptible to athero- sclerosis.3,4 Therefore, a mouse stent model will allow more detailed investigation into the development of in-stent restenosis following stenting of a diseased vessel. The mouse carotid is the best characterized vessel in models employing surrogate injuries, but is too small to stent. The aorta, like the carotid, is an elastic artery and is over twice the diameter of the carotid. The aorta, therefore, is currently the vessel of choice for a mouse stent model. The aorta is also used in several rat models of stenting.11 – 14 All these models use a commercially available balloon expandable stent rather than the coil stent used in our model. Two models involve substantial abdominal surgery, deploying the stent directly into the abdominal aorta via arteriotomy,11,13 another deploys the stent into the thoracic aorta via carotid artery access,12 and a fourth deploys the stent in the abdominal aorta via femoral access in a procedure similar to the one described in our mouse model.14 All these models report a failure rate of 8 – 15%, which is comparable to the 10% rate of our model. The neointima for- mation in all these models is modest and develops slowly over time, with the neointima mainly associated with the stent strut up to 7 days post-procedure. Inﬂammation is also apparent, associ- ated with the stent struts, in these models up to 3 days after place- ment of the stent. This is directly comparable to our mouse model, which also has stent-associated inﬂammation and a small neointima that is initially associated with the stent before becoming a mature, concentric neointima at 28 days. Only one other model of mouse stenting has been developed.5 This model deploys a balloon expandable stent into the thoracic aorta of a donor mouse, which is subsequently grafted into the carotid circulation of a recipient mouse. This model demands a high level of microsurgical skill and uses two mice for each pro- cedure. Our model, in contrast, employs a more simple technique in which a self-expanding stent is deployed ‘directly’ into the aorta of the mouse under investigation. Thus, the stent is deployed in situ, without complicating features of transplantation and marked changes in vessel diameter and ﬂow dynamics. In addition, although our model involves an initial steep learning curve (equivalent to other reported models), it has a high rate of success (92% survival rate compared with 80 – 90% reported by other small animal models) and all vessels were patent on harvest.