Orbital Angiogenesis and Lymphangiogenesis in Thyroid Eye Disease
Ophthalmology, September 2016
In a study designed to assess the role of vascular growth factors in thyroid eye disease (TED), Wong et al. analyzed the composition of orbital fat from patients with acute TED or chronic TED and from individuals without thyroid disease (controls). They also investigated the tenet that orbital adipose tissue lacks lymphatic vessels. They found that in acute TED, there is a greater vascular density and a paucity of lymphatic vessels compared with either chronic TED or controls.
This retrospective cohort study included fat specimens removed during orbital decompression from 26 orbits of 15 patients with TED. Orbital fat specimens from patients without TED, as well as cadaveric orbital fat, served as controls. Tissue specimens were processed for use in immunohistochemistry and for reverse-transcriptase polymerase chain reaction (RT-PCR). These samples were examined for a variety of vascular and lymphatic molecular markers, as well as for mRNA levels of vascular endothelial growth factor (VEGF) and VEGF receptors.
Clinicopathologic correlations in patients with TED were also assessed. In samples from patients with acute TED with a clinical activity score of more than 4, there was increased staining of CD31-positive blood vessels, as well as rare staining of podoplanin-positive lymphatic vessels within acutely inflamed orbital fat tissue. In addition, RT-PCR demonstrated increased expression of VEGF receptor 2 as well as VEGF signaling molecules VEGF-A, VEGF-C, and VEGF-D.
The researchers concluded that the inflamed orbits in acute TED, as compared with chronic TED and control orbits, exhibit increased blood vessels, likely mediated by VEGFR-2 and increased VEGF-A signaling. They also established the presence of some lymphatic vessels. These findings imply that orbital edema in acute TED may be mediated, in part, by both the formation of new, immature blood vessels and the formation of lymphatic capillaries that are functionally incapable of draining interstitial fluid.
The original article can be found here.