Abstract 13133: Impact of Circadian Rhythm Disorders on Reparative Angiogenesis

Introduction: Circadian rhythm disorder seen in shift-worker or jet-lag is major social health concerns in advanced industrialized countries. The aim of this study was to examine if circadian rhythm disorders would influence on angiogenesis and blood perfusion recovery in a mouse model of hind limb ischemia (HLI). Methods and Results: First, we established a jet-lag model in C57BL/6J (wild type; WT) mice (8-10 weeks old, N=10 for each) using a light controlled isolation box. Mice were exposed to advanced 8-hr light phase once every 4 days in a jet-lag group as previously described. Conversely, control mice were kept a regular condition of LD 12:12 (12-hr light and 12-hr dark). Then, we surgically induced HLI in each group. The results showed that the condition jet-lag deteriorated capillary formation detected by CD31-immunohistochemistry at post-operative day (POD) 28 and tissue blood perfusion recovery demonstrated by laser Doppler perfusion imaging (LDPI) in HLI. The expression of clock genes (i.e. Clock, Bmal1, Per2, Cry1 and 2 ) in ischemic muscles were regulated by jet-lag condition at POD7.Next, we examined whether inhibition of clock gene had any effects on angiogenesis. For this study, we focused on Cryptochrome ( Cry ), which is well known as one of the core-loop forming clock genes producing circadian rhythm in mammals. Our loss-of-function study revealed that the abilities of proliferation, migration and tube formation were significantly inhibited by CRY1 and CRY2 double knockdown in HUVECs. Interestingly, although the knockdown of CRY1 and CRY2 changed the mRNA expression of PERIOD2 , it did not affect those of BMAL1 and CLOCK in HUVECs. Finally, we tested if Cry1 and Cry2 double knockout ( Cry1/2 -DKO) mice of HLI models displayed worse blood perfusion recoveries with deterioration of angiogenesis. Cry1/2 -DKO mice were reported to display circadian rhythm disorder in previous reports. As results, compared with control WT mice, Cry1/2 -DKO mice revealed suppressed capillary density and tissue blood perfusion recovery in HLI model. Conclusion: Our data suggest that a maintenance of circadian rhythm plays an important role in reparative angiogenesis of the tissue ischemia model.