- Email: [email protected]
Optical coherence tomography for serial in vivo imaging of aortic plaque in the rabbit
Abstract
S354
and simultaneously offer potent thrombolytic efficacy without bleeding complications, and enable direct monitoring of thrombolysis. Our therapeutic agents/imaging particles, targeted theranostic microbubbles (TT-MB), consist of a fibrinolytic drug urokinase, MBs for visualisation, and an activatedplatelet-specific single-chain antibody for targeting. In the ferric-chloride induced carotid artery thrombosis mouse model, treatment with TT-MB significantly reduced thrombus size after 45 min, while no significant difference was observed in the targeted-MB without urokinase (37 ± 5 vs. 97 ± 4, mean % change ± SEM, normalised to baseline thrombus size, p<0.001). The same degree of efficient thrombolysis was only achievable using a high dose of urokinase (NS). We also show that the targeting and thus clot-enrichment effect of TT-MBs results in a highly potent fibrinolysis that could only be matched using high doses of non-targeted urokinase. However, the latter is associated with a highly prolonged bleeding time (79 ± 6 vs. 1079 ± 260, seconds ± SEM, p<0.001). In contrast, TT-MB does not prolong bleeding time (NS). In conclusion, TT-MBs represent a novel and unique approach to simultaneously diagnose and treat thrombosis as well as to immediately monitor success or failure of thrombolysis. This unique technology holds promise for major progress towards rapid diagnosis and bleeding-free, potent therapy of the vast number of patients suffering from thrombotic diseases. http://dx.doi.org/10.1016/j.hlc.2015.06.565 563 Optical coherence tomography for serial in vivo imaging of aortic plaque in the rabbit J. Fulcher 1,2,∗ , S. Patel 1 , S. Nicholls 3 , S. Bao 4 , D. Celermajer 1 1 Deaprtment
of Cardiology, Royal Prince Alfred Hospital, NSW, Australia 2 NHMRC Clinical Trials Centre, University of Sydney, NSW, Australia 3 SAHMRI, Adelaide, SA, Australia 4 Discipline of Pathology, University of Sydney, NSW, Australia Background We aimed to establish a novel method for studying serial development of atheromatous plaque in vivo, using optical coherence tomography (OCT) in the rabbit abdominal aorta. Methods Eight cholesterol-fed New Zealand White rabbits were assigned to abdominal aortic balloon injury at baseline (n=3), balloon injury at baseline + statin therapy weeks 6-12 (n=3) or control (n=2). OCT of the abdominal aorta in the same rabbit was performed at baseline +/- week 6 +/- week 12 via alternate vascular access points (left or right femoral artery or left carotid artery). OCT sequences were analysed to derive an indexed plaque volume and other measures of plaque complexity, and results were compared by treatment groups. Histopathological correlations with OCT images were made following terminal procedures.
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..
Results Serial OCT was feasible. We defined optimal volumes, contrast media and vascular access protocols. Balloon injured rabbits developed significantly greater and more complex plaque than non-balloon injured rabbits. Treatment with statin therapy from weeks 6-12 was associated with a reduced rate of plaque development and significantly less plaque volume than in controls (p<0.0001). Mean modified lumen stenosis and maximal intima-media thickness were also significantly lower in statin treated rabbits. A significant correlation between measures of plaque area by OCT and histology was demonstrated (Pearson correlation 0.992, p<0.0001). Conclusion Our preliminary experience suggests that serial OCT of the abdominal aorta in rabbits is a feasible and promising means of investigating the effects of atherosclerosis interventions over time. http://dx.doi.org/10.1016/j.hlc.2015.06.566 564 Optical super resolution imaging of cardiac myocyte excitation contraction structures Y. Hou 1,∗ , I. Jayasinghe 2 , D. Crossman 1 , D. Baddeley 3 , C. Soeller 2 1 The
University of Auckland, New Zealand of Exeter, United Kingdom 3 Yale University, USA 2 University
Cardiac myocytes require precise co-ordination between electrical depolarisation and initiation of contraction – a process known as excitation contraction coupling. Central to this is the role of calcium ions as a second messenger being released by the cell; both externally and from the sarcoplasmic reticulum (SR); and activating contraction. To facilitate this, the subcellular organelles and calcium release sites are held in highly organised nanometre scale structures not easily visualised by conventional diffraction limited setups. To overcome this resolution limitation, we have used multicolour dSTORM super resolution imaging to visualise the SR, t-system, and myofibrils in human and rat fixed tissue. Our results of rat cells show mean size of the SR calcium release site of 63 channels with variations including sites of over 400 individual channels. These sizes were several times larger than those previously reported in peripheral couplings. Distances between adjacent clusters showed a mean separation of 140nm. Human cardiac myocytes tested for interspecies consistency show considerable difference from the rat myocytes in terms of morphology with much larger but less interconnected t-tubular systems, greater apparent separation between aligned release sites, and increased amount of small non t-system associated release sites. These results are likely associated with specific calcium dynamic requirements of the cell arising from the differences in resting heart rate between humans and rat; where humans with slower resting heart rate requires less synchronous release and more stability in comparison to faster heart rates seen in rats. http://dx.doi.org/10.1016/j.hlc.2015.06.567
S354
and simultaneously offer potent thrombolytic efficacy without bleeding complications, and enable direct monitoring of thrombolysis. Our therapeutic agents/imaging particles, targeted theranostic microbubbles (TT-MB), consist of a fibrinolytic drug urokinase, MBs for visualisation, and an activatedplatelet-specific single-chain antibody for targeting. In the ferric-chloride induced carotid artery thrombosis mouse model, treatment with TT-MB significantly reduced thrombus size after 45 min, while no significant difference was observed in the targeted-MB without urokinase (37 ± 5 vs. 97 ± 4, mean % change ± SEM, normalised to baseline thrombus size, p<0.001). The same degree of efficient thrombolysis was only achievable using a high dose of urokinase (NS). We also show that the targeting and thus clot-enrichment effect of TT-MBs results in a highly potent fibrinolysis that could only be matched using high doses of non-targeted urokinase. However, the latter is associated with a highly prolonged bleeding time (79 ± 6 vs. 1079 ± 260, seconds ± SEM, p<0.001). In contrast, TT-MB does not prolong bleeding time (NS). In conclusion, TT-MBs represent a novel and unique approach to simultaneously diagnose and treat thrombosis as well as to immediately monitor success or failure of thrombolysis. This unique technology holds promise for major progress towards rapid diagnosis and bleeding-free, potent therapy of the vast number of patients suffering from thrombotic diseases. http://dx.doi.org/10.1016/j.hlc.2015.06.565 563 Optical coherence tomography for serial in vivo imaging of aortic plaque in the rabbit J. Fulcher 1,2,∗ , S. Patel 1 , S. Nicholls 3 , S. Bao 4 , D. Celermajer 1 1 Deaprtment
of Cardiology, Royal Prince Alfred Hospital, NSW, Australia 2 NHMRC Clinical Trials Centre, University of Sydney, NSW, Australia 3 SAHMRI, Adelaide, SA, Australia 4 Discipline of Pathology, University of Sydney, NSW, Australia Background We aimed to establish a novel method for studying serial development of atheromatous plaque in vivo, using optical coherence tomography (OCT) in the rabbit abdominal aorta. Methods Eight cholesterol-fed New Zealand White rabbits were assigned to abdominal aortic balloon injury at baseline (n=3), balloon injury at baseline + statin therapy weeks 6-12 (n=3) or control (n=2). OCT of the abdominal aorta in the same rabbit was performed at baseline +/- week 6 +/- week 12 via alternate vascular access points (left or right femoral artery or left carotid artery). OCT sequences were analysed to derive an indexed plaque volume and other measures of plaque complexity, and results were compared by treatment groups. Histopathological correlations with OCT images were made following terminal procedures.
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..
Results Serial OCT was feasible. We defined optimal volumes, contrast media and vascular access protocols. Balloon injured rabbits developed significantly greater and more complex plaque than non-balloon injured rabbits. Treatment with statin therapy from weeks 6-12 was associated with a reduced rate of plaque development and significantly less plaque volume than in controls (p<0.0001). Mean modified lumen stenosis and maximal intima-media thickness were also significantly lower in statin treated rabbits. A significant correlation between measures of plaque area by OCT and histology was demonstrated (Pearson correlation 0.992, p<0.0001). Conclusion Our preliminary experience suggests that serial OCT of the abdominal aorta in rabbits is a feasible and promising means of investigating the effects of atherosclerosis interventions over time. http://dx.doi.org/10.1016/j.hlc.2015.06.566 564 Optical super resolution imaging of cardiac myocyte excitation contraction structures Y. Hou 1,∗ , I. Jayasinghe 2 , D. Crossman 1 , D. Baddeley 3 , C. Soeller 2 1 The
University of Auckland, New Zealand of Exeter, United Kingdom 3 Yale University, USA 2 University
Cardiac myocytes require precise co-ordination between electrical depolarisation and initiation of contraction – a process known as excitation contraction coupling. Central to this is the role of calcium ions as a second messenger being released by the cell; both externally and from the sarcoplasmic reticulum (SR); and activating contraction. To facilitate this, the subcellular organelles and calcium release sites are held in highly organised nanometre scale structures not easily visualised by conventional diffraction limited setups. To overcome this resolution limitation, we have used multicolour dSTORM super resolution imaging to visualise the SR, t-system, and myofibrils in human and rat fixed tissue. Our results of rat cells show mean size of the SR calcium release site of 63 channels with variations including sites of over 400 individual channels. These sizes were several times larger than those previously reported in peripheral couplings. Distances between adjacent clusters showed a mean separation of 140nm. Human cardiac myocytes tested for interspecies consistency show considerable difference from the rat myocytes in terms of morphology with much larger but less interconnected t-tubular systems, greater apparent separation between aligned release sites, and increased amount of small non t-system associated release sites. These results are likely associated with specific calcium dynamic requirements of the cell arising from the differences in resting heart rate between humans and rat; where humans with slower resting heart rate requires less synchronous release and more stability in comparison to faster heart rates seen in rats. http://dx.doi.org/10.1016/j.hlc.2015.06.567