Identification of proteins and genes involved in proliferative diabetic retinopathy

Proliferative diabetic retinopathy (PDR) is the most serious of the ocular
complications of diabetes. Retinal traction often occurs late in the disease
and is due to neovascular growth, bleeding from the new vessels, development of
neovascular epiretinal membranes (ERMs), and vitreous contraction. ERMs form on
the surface of the neuroretina and have been postulated to represent part of
the wound healing process. Research on epiretinal membranes or fibrovascular
membranes has mainly been focussed on their angiogenic potential. To date, no
extensive analysis has been done to investigate the involvement of neuronal
growth factors. We recently reported however that the epiretinal proliferation
of membranes cannot occur without the presence of neuronal cells, such as
ganglion cells or Müller cells, which serve as a support and guide formation of
new blood vessels. Neurites did not only sprout within the retina, but were
also found to grow out of the retina into fibrovascular membranes in
proliferative diabetic retinopathy (PDR) as well as in epiretinal membranes
from other causes. In previous studies we found simultaneous growth of
epiretinal membranes (ERMs) and certain retinal nerve cells (ganglion cells).
These nerve cells may have very long neurites. Along these neurites
bloodvessels can grow in PDR. Untill now facors involved in neurite outgrowth
and the development op ERMs have not yet been identified.

Recent technological developments like micro-array analysis and antibody-arrays
give rise to new opportunities in identifying genes and their protein products
in specific tissues. To determine which factors are involved in the outgrowth
of neural cells, we want to perform a micro-array analysis on surgically
removed membranes in patients with PDR. We also want to do research on the
vitreous of these patients. Antibody-array can screen large numbers of proteins
in the vitreous. To combine the results of both techniques, we hope to find
factors involved in neurite outgrowth in these patients. Because patients with
PDR often have bleedings in the eye , and increased vascular permeability
occurs in DR , plasma of these patients will be analyzed as well to check
whether an increase of certain proteins in the vitreous may be caused by
leakage from the blood. In addition an extra tube of blood is collected for
analysis of DNA. This allows us to determine genetic variants of the proteins
have been found and correlate these with protein levels and clinical parameters
such as the degree of vessel growth, connective tissue formation, and neurite
outgrowth.

Vitreous humor and epiretinal membranes are residual materials that are
normally removed during surgery and will provide no additional burden for the
patient. Preoperatively blood will be collected for standard screening. Two
extra tubes will be collected for research. This needs no extra injection and
gives minimal burden for the patient.

Identification of the proteins that are involved in neurite outgrowth in PDR.
We want to determine what protein levels are increased in the vitreous by local
production and which RNA transcripts are present in the fibrotic membranes of
patients with PDR compared to non-diabetic individuals.

Case control-study

There will be no extra risk involved for the patient. The material which is
used in this study is residual material, this material is normally destroyed at
the end of surgery. We will use it for research. The only extra burden for the
patient is reading the research information folders. Normally blood is taken
before surgery. In case of participation in the study extra blood will be drawn
from the patient. So practically there is no real extra burden for the patient.