Mural delivery of iloprost with use of hydrogel-coated balloon catheters suppresses local platelet aggregation

Iloprost up-regulates vascular endothelial growth factor expression in human dental pulp cells in vitro and enhances pulpal blood flow in vivo

INTRODUCTION

Prostacyclin (PGI2) is a biomolecule capable of enhancing angiogenesis and cellular proliferation.

METHODS

We investigated the influence of a PGI2 analogue (iloprost) on dental pulp revascularization in vitro and in vivo by using human dental pulp cells (HDPCs) and a rat tooth injury model, respectively. Iloprost stimulated the human dental pulp cell mRNA expression of vascular endothelial growth factor (VEGF), fibroblast growth factor-2 (FGF-2), and platelet-derived growth factor (PDGF) in a significant dose-dependent manner. This mRNA up-regulation was significantly inhibited by pretreatment with a PGI2 receptor antagonist and forskolin (a protein kinase A activator). In contrast, a protein kinase A inhibitor significantly enhanced the iloprost-induced mRNA expression of VEGF, FGF-2, and PDGF. Pretreatment with a fibroblast growth factor receptor inhibitor attenuated the VEGF, FGF-2, and PDGF mRNA expression, indicating opposing regulatory mechanisms.

RESULTS

The effect of iloprost on the dental pulp was investigated in vivo by using a rat molar pulp injury model. The iloprost-treated group exhibited a significant increase in pulpal blood flow at 72 hours compared with control.

CONCLUSIONS

The present study indicates that iloprost may be a candidate agent to promote neovascularization in dental pulp tissue, suggesting the potential clinical use of iloprost in vital pulp therapy.

Site-specific delivery of iloprost during experimental angioplasty suppresses smooth muscle cell proliferation

PURPOSE

The authors have previously reported that intramural delivery of iloprost during angioplasty suppresses local platelet aggregation at 1 hour in undiseased porcine arteries. In this study, the authors sought to quantify the effect of such treatment on medial vascular smooth muscle cell proliferation, an event implicated in the development of intimal hyperplasia.

MATERIALS AND METHODS

Three Yorkshire pigs underwent percutaneous transluminal angioplasty with hydrogel-coated balloons for a total of 10 iloprost-treated (experimental) and 10 saline-treated (control) arterial sites. The balloons were prepared with previously reported techniques and loaded with 2.25 microg of iloprost for the experimental sites. On the eighth day after angioplasty, these sites were harvested and prepared for immunohistochemical staining. Thin (4 microm) sections of the specimens were stained with use of monoclonal antibody to proliferating cell nuclear antigen (PCNA). Appropriate positive and negative controls were used. Approximately 350-500 vascular smooth muscle cells were randomly counted under high power (100x) by an experienced physician who was blinded to the origin of the specimen. A PCNA index (%) was calculated as follows: [(#PCNA [+] cells)/(#PCNA [+] cells + #PCNA [-] cells)]x 100. A paired t test was used for statistical comparison.

RESULTS

The PCNA indices for eight (n = 8) paired large vessels (iliac, carotid, subclavian) were 7.98 (+/- 1.8)%, for the iloprost-treated experimental sites, and 14.58 (+/- 3.8)% for the saline-treated control sites. This difference was statistically significant (P = .003). One large vessel pair was not available for analysis. When the pair of renal arteries of animal 3 were included (n = 9), the PCNA indices were 8.32 (+/- 2.3)% for the experimental sites, and 13.79 (+/- 4.2)% for the control sites. The differences were again significant (P = .01).

CONCLUSION

Intraarterial site-specific delivery of iloprost during angioplasty with drug-loaded, hydrogel-coated balloons significantly suppresses medial smooth muscle cells in swine at the expected peak period of proliferation of 7 days after angioplasty.