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VOL. 75 (4), 901-910, 2009 OVER-EXPRESSION OF P2Y2 RECEPTOR AFTER SILENCING...

the entry of a foreign body, any traumatic process, a defect in contact
lenses or the use of refractive surgery to correct refractive alterations.

When this happens, a process named corneal wound healing
starts to regenerate normal epithelium in order to maintain the
correct refraction of light. Corneal wound healing involved three
consecutive phases that are part of a continuous process. Animal
studies have shown that these three stages are: lag phase (from
0 hours to 10 hours after the wound), cell migration (until 24 to
36 hours after the wound) and cell proliferation (lasting from 24-36
hours after the wound to weeks) (1).

There are many substances present in tears, aqueous humour or
released from corneal nerves, that modified the wound healing
process after ocular surface injuries (2, 3). Within these molecules
we find nucleotides and dinucleotides (3, 4). In our previous works
we demonstrated that the dinucleotides can modify rate of corneal
re-epithelialization in New Zealand White Rabbits both in vivo and
in vitro (3, 5). We have demonstrated, both pharmacologically and
with the used of the RNA interference (RNAi) technology, that Ap4A
produces acceleration in the rate of corneal re-epithelialization by
stimulating to P2Y2 receptors. On the contrary other dinucleotides,
Ap3A and Ap5A exert the opposite effect delaying corneal re-
epithelialization by binding to a P2Y6 receptor (5, 6).

The aim of this manuscript is to describe the presence of the
P2Y2 receptor in the cornea and to see the effect of a siRNA against
the P2Y2 receptor in the presence and in the absence of Ap4A.

2. MATERIALS AND METHODS

2.1. Animals

Male, adult New Zealand White Rabbits were used. All the animals
were kept in individual cages with free access to food and water, under
controlled cycles (12 hours light:12 hours dark), and the experimental
procedures were carried out in accordance with the ARVO Statement
for the Use of Animals in Ophthalmic and Vision Research, and the
European Communities Council Directive (89/609/EEC).

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