Arrest of progression of pre-induced abdominal aortic aneurysm in apolipoprotein E-deficient mice by low level laser phototherapy.

BACKGROUND AND OBJECTIVES: Using non-invasive, high-frequency ultrasonography (HF-u/s), we showed that low-level laser phototherapy (LLL) inhibits de-novo formation of abdominal aortic aneurysms (AAA) in apolipoprotein-E-deficient (Apo-E(-/-)) mice. The current study tests the effect of LLL on the progression of pre-induced AAA. STUDY DESIGN/MATERIAL AND METHODS: AAA was induced in Apo-E(-/-) mice (age 16-20 weeks) by subcutaneous infusion of angiotensin-II using osmotic minipumps (1000 ng/kg/minutes, 4 weeks). HF-u/s (40 MHz, 0.01 mm resolution, Vevo-770, VisualSonics) was used to measure the maximum cross-sectional-diameter (MCD) of the suprarenal abdominal aorta, the anterior wall displacement (AWD), and radial wall velocity (RWV). The aortas of mice that developed >35% dilatation at 2 weeks over baseline were exposed retroperitoneally and treated with LLL (780 nm, 2.2 J/cm(2), 9 minutes) or sham-operated. HF-u/s was repeated at 4 weeks, the mice sacrificed by perfusion fixation, and the aortas excised for histopathology. RESULTS: Of all mice with >35% MCD expansion of the suprarenal aorta at 2 weeks, 7(58%) of 12 non-treated, but only 1(7%) of 14 LLL, had increased MCD(> 1 SD) at 4 weeks (P < 0.009 by Fisher's Exact Test [FET]). The mean change in MCD from 2-4 weeks was also markedly reduced in the LLL-treated mice (control vs. LLL, 0.24 ± 0.25 vs. -0.06 ± 0.39 mm, P = 0.029 by unpaired t-test). Similar results were obtained when limiting the analysis to animals with ≥ 50% expansion at 2 weeks. The deterioration in AWD from 2-4 weeks in non-treated controls was not observed in LLL-treated animals (ΔAWD: control, 0.03 ± 0.05 mm, P < 0.036 vs. LLL, 0.00 ± 0.05, P = 0.91 by paired t-test). By the modified Daugherty classification, we found significantly fewer severe aneurysms at 4 weeks in the LLL-treated animals versus control (3 of 10 vs. 9 of 11, P = 0.03 by FET). CONCLUSIONS: LLL not only prevents de novo development of AAA, but, from this study, also arrests further progression of pre-induced AAA and its associated deterioration in the biomechanical integrity of the aortic wall in Apo-E(-/-) mice.

A transgenic platform for testing drugs intended for reversal of cardiac remodeling identifies a novel 11ßHSD1 inhibitor rescuing hypertrophy independently of re-vascularization.

RATIONALE: Rescuing adverse myocardial remodeling is an unmet clinical goal and, correspondingly, pharmacological means for its intended reversal are urgently needed. OBJECTIVES: To harness a newly-developed experimental model recapitulating progressive heart failure development for the discovery of new drugs capable of reversing adverse remodeling. METHODS AND RESULTS: A VEGF-based conditional transgenic system was employed in which an induced perfusion deficit and a resultant compromised cardiac function lead to progressive remodeling and eventually heart failure. Ability of candidate drugs administered at sequential remodeling stages to reverse hypertrophy, enlarged LV size and improve cardiac function was monitored. Arguing for clinical relevance of the experimental system, clinically-used drugs operating on the Renin-Angiotensin-Aldosterone-System (RAAS), namely, the ACE inhibitor Enalapril and the direct renin inhibitor Aliskerin fully reversed remodeling. Remodeling reversal by these drugs was not accompanied by neovascularization and reached a point-of-no-return. Similarly, the PPARγ agonist Pioglitazone was proven capable of reversing all aspects of cardiac remodeling without affecting the vasculature. Extending the arsenal of remodeling-reversing drugs to pathways other than RAAS, a specific inhibitor of 11ß-hydroxy-steroid dehydrogenase type 1 (11ß HSD1), a key enzyme required for generating active glucocorticoids, fully rescued myocardial hypertrophy. This was associated with mitigating the hypertrophy-associated gene signature, including reversing the myosin heavy chain isoform switch but in a pattern distinguishable from that associated with neovascularization-induced reversal. CONCLUSIONS: A system was developed suitable for identifying novel remodeling-reversing drugs operating in different pathways and for gaining insights into their mechanisms of action, exemplified here by uncoupling their vascular affects.

Low level laser arrests abdominal aortic aneurysm by collagen matrix reinforcement in apolipoprotein E-deficient mice.

BACKGROUND AND OBJECTIVES: Recent in vitro studies by our group indicated that low level laser irradiation (LLLI) modifies cellular processes essential to the progression of abdominal aortic aneurysm (AAA). Using high-frequency ultrasonography (HF-u/s) in the angiotensin-II (Ang-II)-infused, apolipoprotein-E-deficient (Apo-E(-/-) ) mouse model of AAA, we found that LLLI markedly inhibited aneurysm formation and preserved arterial wall elasticity. We now report, using quantitative histopathology, the likely mechanism underlying the preventative effect of LLLI on aneurysm formation in this model. STUDY DESIGN/MATERIALS AND METHODS: This study was performed on 32 Apo-E(-/-) mice of which 10 were Ang-II-infused and LLL-irradiated (780 nm, 2 J/cm(2) , 9-minutes), 12 were Ang-II-infused but not irradiated, and 10 were saline infused. The aortas were excised at 28d, sectioned at 250 µm intervals, and stained with H + E, Movat-pentachrome and picrosirius-red for histomorphometry, and immunostained with Mac-2 and α-actin for detection of macrophages and SMCs, respectively. RESULTS: Transmural disruptions of the aorta occurred with distinct predilection for branch orifices. In the LLLI-treated animals, the frequency of these disruptions was lower (#branches with break points: 17 of 40 vs. 32 of 48, P = 0.023 by Chi-squared), their size smaller (length [mm]: 0.48 ± 0.26 vs. 0.98 ± 1.42, P = 0.044 by ANOVA with FPLSD), and the number of Mac-2-positive macrophages in the intramural areas of these disruptions lower than in the non-treated control (#Macrophages/0.01 mm(2) at break points: 11.6 ± 7.2 vs. 26.0 ± 15.7, P = 0.016 by Kruskal-Wallis). The average size of the medial SMCs was larger reflecting a heightened synthetic state (SMC size [µm(2) ]: 463.9 ± 61.4 vs. 354.9 ± 71.7, P = 0.001 by ANOVA with FPLSD). Furthermore, at sites of transmural disruption, the %area occupied by collagen of the overall area of attempted repair (%Col/WO) was significantly greater in the LLLI-treated animals versus control (%Col/WO: 41 ± 13 vs. 32 ± 16, P = 0.009 by ANOVA with FPLSD). CONCLUSION: Enhanced matrix reinforcement and modification of the inflammatory response at sites of transmural injury are prominent mechanisms by which LLLI reduces AAA progression in this model.

Low-level laser irradiation inhibits abdominal aortic aneurysm progression in apolipoprotein E-deficient mice.

AIMS: Increased early detection of abdominal aortic aneurysm (AAA) and the severe complications of its current treatment have emphasized the need for alternative therapeutic strategies that target pathogenetic mechanisms of progression and rupture. Recent in vitro studies from our laboratory have shown that low-level laser irradiation (LLLI) (780 nm) modifies cellular processes fundamental to aneurysm progression. The present study was designed to determine whether LLLI retards the progression of suprarenal AAA in vivo. METHODS AND RESULTS: High-frequency ultrasonography (0.01 mm resolution) was used to quantify the effect of LLLI on aneurysmatic aortic dilatation from baseline to 4 weeks after subcutaneous infusion of angiotensin II by osmotic minipumps in the apolipoprotein E-deficient mouse. At 4 weeks, seven of 15 non-irradiated, but none of the 13 LLLI, mice had aneurysmal dilatation in the suprarenal aneurysm-prone segments that had progressed to >or=50% increase in maximal cross-sectional diameter (CSD) over baseline (P = 0.005 by Fisher's exact test). The mean CSD of the suprarenal segments (normalized individually to inter-renal control segments) was also significantly lower in irradiated animals (LLLI vs. non-irradiated: 1.32 +/- 0.14 vs. 1.82 +/- 0.39, P = 0.0002 by unpaired, two-tailed t-test) with a 94% reduction in CSD at 4 weeks compared with baseline. M-mode ultrasound data showed that reduced radial wall velocity seen in non-treated was significantly attenuated in the LLLI mice, suggesting a substantial effect on arterial wall elasticity. CONCLUSION: These in vivo studies, together with previous in vitro studies from this laboratory, appear to provide strong evidence in support of a role for LLLI in the attenuation of aneurysm progression. Further studies in large animals would appear to be the next step towards testing the applicability of this technology to the human interventional setting.