A novel organ culture method to study intimal hyperplasia at the site of a coronary artery bypass anastomosis

Background. Intimal hyperplasia or restenosis at the site of a coronary artery bypass anastomosis contributes to early graft failure, and growth factor release in response to construction of the anastomotic site strongly influences this process. Due to the difficulties in studying restenosis after coronary artery bypass graft surgery, we have tested whether an organ culture model we have developed can simulate the early events associated with intimal hyperplasia. Methods. End-to-side anastomosis of porcine radial artery to porcine coronary artery were constructed. The vessels were trimmed and incubated under standard tissue culture conditions for 14 days. Appropriate controls were treated similarly. The vessels were frozen, cryosectioned, and immunostained for the expression of the proliferation marker proliferating cell nuclear antigen (PCNA). A proliferative index (PCNA positive nuclei/total nuclei) was calculated for comparative purposes. Results. Limited PCNA staining was observed in noncultured vessel segments (0.046 ± 0.045). A slight increase in this index was observed in vessels that had been placed into culture without manipulation (0.230 ± 0.141) and in vessels subjected to an arteriotomy (0.462 ± 0.249). However, the most significant increase was obtained after construction of an anastomosis (4.98 ± 6.66). No change in total cell number was evident over the course of the experiment or in relation to the treatment. Conclusions. Culture conditions and incision slightly stimulate cell proliferation in porcine coronary artery segments when compared with basal conditions of a native artery. In contrast, construction of an anastomosis increases proliferation 108-fold. Therefore, surgical manipulation of arterial conduits during construction of an anastomotic site is the primary trigger for intimal hyperplasia, independent of dissection and incision of the vessel. Furthermore, these data indicate the organ culture model we have developed will be useful for examining the cellular and molecular mechanisms that mediate intimal hyperplasia at the site of a coronary artery bypass graft anastomosis.