Increased choroidal neovascularization following laser induction in mice lacking lysyl oxidase-like 1.
OBJECTIVE
Age-related degradation of the elastic lamina in Bruch's membrane may have a permissive effect on the growth of choroidal neovascularization (CNV). This study investigated the influence of defective elastic fiber maintenance in the development of laser-induced CNV.


METHODS
A mouse lacking lysyl oxidase-like (LOXL)-1, an enzyme essential for elastin polymerization, was studied. The morphologic characteristics of the elastic lamina within Bruch's membrane were examined in mutant and wild-type (WT) eyes. Laser-induced CNV was evaluated by fluorescein angiography and choroidal flat mounts. Immunohistochemistry for elastin was performed on the CNV lesions, and vascular endothelial growth factor (VEGF) levels were determined by ELISA. Soluble elastin and matrix metalloproteinase (MMPs) levels were also analyzed by immunoblotting.


RESULTS
The elastic lamina of Bruch's membrane in the LOXL1-deficient mice was fragmented and less continuous than in the WT controls. The mutant mice showed increased levels of soluble elastin peptides and reduced elastin polymer deposition in neovascular membranes. Significantly larger CNV with greater leakage on fluorescein angiography developed in mutant mice. VEGF levels in the RPE/choroid were higher in the knockout mice on days 7 and 14 after laser (P < 0.05). MT1-MMP (MMP14) was also elevated after laser in the LOXL1 mutant eyes compared to the WT controls.


CONCLUSIONS
These results show that a systemic defect in elastic fiber deposition affects Bruch's membrane integrity and leads to more aggressive CNV growth. The latter may be partially mediated by abnormal signaling from the accumulation of soluble elastin peptides.
Yu
Hyeong Gon
HG
Angiogenesis Laboratory and Laser Laboratory, Retina Research Institute, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts 02114, USA.
Liu
Xiaoqing
X
Kiss
Szilard
S
Connolly
Edward
E
Gragoudas
Evangelos S
ES
Michaud
Norman A
NA
Bulgakov
Oleg V
OV
Adamian
Michael
M
DeAngelis
Margaret M
MM
Miller
Joan W
JW
Li
Tiansen
T
Kim
Ivana K
IK
D000594:Amino Acid Oxidoreductases / Q000502:physiology*; D000818:Animals; D016570:Bruch Membrane / Q000201:enzymology* / Q000648:ultrastructure; D020256:Choroidal Neovascularization / Q000201:enzymology* / Q000209:etiology / Q000503:physiopathology*; D004547:Elastic Tissue / Q000201:enzymology* / Q000648:ultrastructure; D004549:Elastin / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005451:Fluorescein Angiography; D019084:Fluorescent Antibody Technique, Indirect; D015151:Immunoblotting; D017075:Laser Coagulation; D008297:Male; D020782:Matrix Metalloproteinases / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016253:Microscopy, Immunoelectron; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D004549:Elastin; D000594:Amino Acid Oxidoreductases; C482019:Loxl1 protein, mouse; D020782:Matrix Metalloproteinases