Download Background Ophthalmological Changes Following Subretinal

Background Ophthalmological Changes Following Subretinal Injection in the
Brown Norway Rat
1
Vézina ,
1
Li ,
2
Bussières
M.
C.
M.
1Charles River, Senneville (Montreal), Canada; 2V&O Services, St. Lazare, Canada
EVER: NICE, FRANCE
Introduction
10/2015
Subretinal injection has become more
common in recent years as it is the route of
choice for cell and gene therapy products
targeting the retina. A subretinal dose
allows for localized placement and
containment of the administered product.
The purpose of the study was to evaluate the
background changes associated with
transscleral subretinal injection in Brown
Norway (BN) rats. Brown Norway rats were
chose since they are a common species
used for ocular studies and their pigmented
eyes facilitate the subretinal dosing
procedure.
Methods
Fifteen Brown Norway rats, 12 weeks of age,
received a bilateral subretinal injection of
0.9% sterile saline at a volume of 6 uL while
under isoflurane anesthesia. The injection
was performed using a 10 µL Hamilton
syringe with a 32G, ½-inch needle. Prior to
injection, a pilot hole was made in the sclera
using a 30G needle to facilitate insertion of
the dosing needle into the eye. The eyes
were examined by slit lamp and indirect
ophthalmoscope the day following injection
and 1, 2, 3, 4, 8 and 12 weeks post injection.
Results
Results (cont.)
A summary of results is presented in Table 1
Table 1: Incidence of Ophthalmological Observations
N=30 eyes
Observation
Day 2
1 Wk
2 Wks
3 Wks 4 Wks 8 Wks 12Wks
Total
Incidence
Corneal opacity
5
5
4
-
-
-
-
5/30
Cataract
1
3
5
1
1
2
2
5/30
Vitreous
hemorrhage
28
21
15
13
11
2
2
28/30
Irregular
pigmentation in
bleb
1
3
5
5
9
2
2
13/30
Retina / choroid
hemorrhage at
injection site
19
20
18
13
4
-
-
20/30
Focal
depigmentation at
injection site
-
12
12
12
12
7
7
12/30
Focal retinal
opacity
6
14
13
13
16
9
9
18/30
Retinal elevation
(bleb)
27
12
-
-
-
-
-
27/30
The bleb, described as retinal elevation, was observed in 27/30 eyes the day after
dosing and in 12/30 up to 1 week post dose (it was observed in all eyes
immediately post dose). Transient corneal opacities occurred in 5/30 eyes that
were considered related to the anesthesia. Cataracts developed in 5/30 eyes and
were associated with lens trauma at the time of dosing. Slight vitreous
hemorrhages occurred post dose in 28/30 eyes, resolving in all but 2 eyes by 4
weeks.
An area of focal depigmentation of the
retina/choroid or white focal retinal opacity was
seen at the needle insertion site in the retina in
12/30 or 18/30 eyes, respectively, resolving by
4 weeks in 50% of the eyes and persisting up to
12 weeks for the remaining eyes. In the bleb
itself, there were focal areas of irregular
pigmentation in 13/30 eyes resolving in all but 2
eyes by week 4. The remaining 2 persisted up
to week 12. Slight retinal/choroidal
hemorrhages were also seen at the injection
site in most eyes up to week 4. The severity of
the ocular changes also diminished from
slight/moderate to very slight/slight over the
course of the 12 week observation period.
Conclusion
Transscleral subretinal injection in BN rats
generally resulted in slight ocular trauma that
resolved in most eyes by 4 weeks post
injection. It is important to take these changes
into account when evaluating therapeutics
administered by this dose route.
Acknowledgements
The authors wish to thank the technical staff of the
Ocular and Neuroscience Department for their
participation in generating data for this evaluation.