To analyze short term toxicity of the mannitol included (3,375 μg; 0,225%) in an unilateral single intravitreal (ITV) injection (1.5μl) of freezed dry polyester amide (PEA) microparticles (“MPs”).Methods
SD rats were divided into: G1: ITV Mannitol plus BSS; G2: ITV BSS; G3: Aged-matched control. Clinical examination and animal sacrifice were performed 24 hours, 3 and 7 days post-injection (PI). Tissue sections were processed for H&E and immunofluorescence with antibodies against GFAP, Iba-1 and MHC class II.Results
No clinical signs of inflammation were observed at any time point of the study. H&E: The conjunctiva in G1 and G2 had an inflammatory infiltrate that peaked at 24 hours and decreased by day 3. On day 7, tissues looked as aged-matched control. In both groups, some inflammatory cells were found in the vitreous 24h and 3 days PI, the latter being more intense in G1. Immunostaining: the reactivity of astrocytes and Müller cells in G1 was higher than in G2 up to day 3. In day 7 PI, there was a mild and sectorial reaction of Müller cells in G1. Microglia in G1 and G2 showed morphological signs of activation 24h and 3 days PI, the reaction being stronger in G1. On day 7 PI: i) all microglia in G2 and the microglia in the outer retina in G1 looked like control; ii) the microglia in the inner retina showed signs of activation in G1. No MHC-II upregulation was found in either group.Conclusion
Intravitreal injection of 1.5μL of mannitol (3,375 μg; 0,225%) induces changes in the glial cells of SD rat retina that should be taken into account in biocompatibility assays after intravitreal injections of mannitol freezed dry microparticles.