Porcine coronary artery organ culture: A model for the study of angioplasty injury

Inhibitory Effects of PRG4 on Migration and Proliferation of Human Venous Cells

BACKGROUND

Proteoglycan 4 (PRG4; lubricin) is a member of two gene co-expression network modules associated with human vein graft failure. However, little is known about PRG4 and the vascular system. Therefore, we have investigated the effects of recombinant human PRG4 (rhPRG4) on cell migration and proliferation in human veins.

METHODS

Effects of rhPRG4 on cell migration, proliferation, and neointima formation were determined in human venous tissue and cultured venous smooth muscle cells (SMCs), adventitial cells, and endothelial cells. Expression of PRG4 by cultured human saphenous veins, failed vein grafts, and varicose veins was determined by immunostaining or Western blotting.

RESULTS

Limited expression of PRG4 in fresh saphenous veins was dramatically increased around medial SMCs after culture ex vivo. rhPRG4 inhibited the migration of cultured SMCs, adventitial cells, and endothelial cells, as well as the proliferation of endothelial cells. rhPRG4 also inhibited the migration of SMCs and adventitial cells from tissue explants, but there was no effect on cell proliferation or neointima formation in ex vivo whole veins. Finally, PRG4 was largely absent in two examples of venous pathology, that is, failed human vein grafts and varicose veins.

CONCLUSIONS

Although rhPRG4 can inhibit the migration of venous SMCs, endothelial cells, and adventitial cells, and the proliferation of endothelial cells, PRG4 was only increased around medial SMCs in veins after ex vivo culture. PRG4 was not observed around medial SMCs in failed human vein grafts and varicose veins, suggesting the possibility that a failure of PRG4 upregulation may promote these pathologies.

Thrombus organization plays no major role in late neointimal formation after angioplasty in porcine coronary arteries

Thrombus organization has been suggested to play a major role in late neointimal formation after coronary angioplasty. We sought to describe the time sequence of lesion formation after angioplasty in porcine coronary arteries and to quantify the relation between early thrombosis and late neointimal formation. Deep vessel wall injury was induced by conventional balloon angioplasty in the circumflex (CX) and right coronary (RCA) arteries and by retraction of a chain-encircled balloon in the left anterior descendent artery (LAD). Lesions were assessed by histomorphometry at days 0, 1, 4, 7, 14, 28, and 56 after angioplasty. A response-to-injury index (lesion area/injury length) was determined for each artery. Angioplasty led to rupture/removal of media. Thrombus was present at the exposed adventitia at days 0, 1, and 4. From day 7, neointima was observed on the luminal side of the arterial wall. All thrombus had disappeared at day 28, at which only neointima was observed. Histomorphometry revealed that lesion formation after angioplasty was a gradually increasing process from day 0 to day 28 with no further growth from day 28 to day 56. Maximal thrombus size (day 4, RCA: 0.07+/-0.04 mm, CX: 0.23+/-0.16 mm, LAD: 0.15+/-0.11 mm) was significantly smaller than late neointimal formation (day 28, RCA: 0.68+/-0.18 mm, CX: 0.63+/-0.23 mm, LAD: 0.71+/-0.18 mm) in all three arteries (p < .03). Lesion formation after angioplasty is a gradually increasing process for 4 weeks. Maximal thrombus size is about four times smaller than late neointimal formation. Thus, thrombus organization plays no major role in late neointimal formation.

Antithrombotic and thrombolytic therapy in patients undergoing coronary artery interventions: a review

The controlled arterial injury that occurs with balloon angioplasty and other coronary interventions is characterized by evanescent endothelial denudation and vascular disruption. As a consequence, platelet activation occurs at the treated site, and there is a risk of thrombotic occlusion. This risk is heightened by several factors including unstable clinical presentation, lesion complexity, deep injury, and dissection. Aspirin has been shown to unquestionably reduce, although not eliminate, acute complications and is now part of the routine periprocedural regimen. Heparinization with more intense anticoagulation than is conventionally used is also standard treatment and is initiated before vessel instrumentation. Adjunctive thrombolysis is rarely necessary unless refractory thrombus precedes or complicates the procedure. However, thrombolysis may have a role in the treatment of saphenous vein graft obstructive lesions in which guide wire- or catheter-induced distal thromboembolization may cause infarction in spite of successful graft recanalization. In contrast to their success in the periprocedural phase of coronary interventions, anticoagulants and a wide variety of platelet active agents have been ineffective in reducing the 30% to 40% incidence of restenosis. Only 7E3, which targets the final common pathway of platelet aggregation by irreversibly blocking the IIb/IIIa receptor, has been shown to decrease the 6-month clinical event rate after balloon angioplasty, possibly by a surface pacification mechanism. This suggests that newer more potent antiplatelet and anticoagulant agents may also find a role in the long-term management of these patients.