Abstract
Purpose :
In accordance with the growth of the elderly population, the importance of vitreous replacements increases. With an incidence of 1/100.000 the rhegmatogenous retinal detachment is one of the prevalent reasons for a visus-threatening ophthalmological urgency.
The aim of the study was to evaluate the biocompatibility of two hyaluronic acid (HA) based crosslinked hydrogels used as artificial vitreous substitute. The two gels (gel 1 and gel 2) mainly differed with respect to rheological properties and HA content. In the first part of the study, we used pig eyes as an alternative animal model to test the swelling of the vitreous substitutes in a pressure model. The biosafety was assessed via qRT-PCR Western Blot and Histology.
Methods :
Fresh pig eyes were obtained from the local abattoir and immediately processed after arrival. Standard vitrectomy was performed followed by injection of either gel 1, gel 2 or BSS (as a control). Afterwards, the intraocular pressure was monitored for 24 h. To ensure survival of the retina, the eye was perfused with DMEM for the whole time-span. Afterwards, one half of the eyecup was processed for histological evaluation. Cryosections were stained with antibodies specific for microglia (anti-CD11b), astrocytes (anti-GFAP) and retinal ganglion cells (Brn3a). The other half of the eyecup was used to prepare tissue punches which were then used either for qRT-PCR or Western-Blot analysis. Expression of Bax/Bcl–2-ratio, GFAP-, b-3 tubulin- and PGP9.5 was analyzed.
Results :
The histological evaluation of the treated ex-vivo eyes did not reveal an increase of any of the investigated glia markers. In accordance, no decrease in the amount of retinal ganglion cells (RGC) was found. In addition, there was no significant difference within the Bax/Bcl-2-ratio of eyes treated with either of the two different gels. Interestingly, GFAP was more strongly expressed in eyes operated with gel 1. Nevertheless, there was no significant difference between the control eyes and the gel-treated eyes (p < 0.05, n = 5). In agreement with immunohistochemical results, no significant differences in expression of b-3–Tubulin were determined by qRT-PCR, indicating that there has not been any loss of RGC.
Conclusions :
In conclusion, no signs of a negative or toxic influence on the retina after implantation of the hydrogels was observable. Therefore, further in-vivo experiments can be safely conducted.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.