Abstract 053: Carbaprostacyclin Promotes Vascular Growth in Mouse Hindlimb Ischemia

Abstract

Background: Prostacyclin and its stable analogues are vascular protective agents that have been used clinically to reduce blood vessel constriction. Recent studies indicate they stimulate angiogenesis in response to tissue ischemia, but their role in arteriolar growth remains unclear. In the current study, we test the hypothesis that the prostacyclin stable analogue carbaprostacyclin (cPGI2) facilitates arteriolar growth in ischemic hindlimbs. Methods and Results: Catheters were attached to osmotic pumps in order to continuously deliver either cPGI2 or saline (control) locally into ischemic mouse hindlimbs for 7 and 14 days (n=5/group). At 7 days of cPGI2 delivery, live microscopic images showed more distinct structural remodeling at the arteriolar level in the cPGI2 group than in the saline group, including tortuosity of arteriolar-to-arteriolar connections and increased intersecting of adjacent arterioles. Vascular casting with a silicone radiopaque agent into the distal region of the infrarenal abdominal aorta revealed a more pronounced arterial anastomoses in the cPGI2 treated versus the saline treated ischemic legs. After immunofluorescence staining, laser scanning confocal microscopic analysis found more transmembrane proteoglycan NG2 positive vessels in cross sections of anterior thigh muscles in cPGI2-treated mice than in saline-treated mice. At 14 days, quantitative micro-computed tomography analysis indicated cPGI2-treated legs had markedly increased vascular volume (41.28 ± 2.22 vs 27.11 ± 2.85 mm3), significantly more blood vessels (0.16 ± 0.014 vs 0.09± 0.011 1/mm) and less distance between vessels (6.60 ± 0.52 vs 10.15 ±1.14 mm) than did saline-treated legs. To further verify the pro-arteriogenic effect of cPGI2, a quantitative histogram was generated and exhibited that cPGI2-treated ischemic legs have a significant increase in small vessels, with vessel diameter bins ranging from 40-60 microns. We similarly evaluated contralateral nonischemic legs and found no significant differences in vessel distribution in the cPGI2 and saline groups. Conclusion: Multi-imaging technical analyses indicated that local delivery of carbaprostacylin promotes arteriolar growth in mouse hindlimb ischemia.