Il ruolo delle neurotrofine e di VEGF nel mantenimento dell'omeostasi oculare

Neurotrophins (NTs), the proteins involved in survival and growth of neuronal and no neuronal cell types, and vascular endothelial growth factor (VEGF), which mediates blood vessel growth in healthy and pathological tissues, play a central role in ocular homeostasis. Deregulation of NTs and VEGF signalling has been observed in many eye disorders characterised by angiogenesis, which are commonly treated by intraocular anti-VEGF drug administration. Several investigations evaluated the safety profile of anti-VEGF drug ocular treatment, also showing adverse effects like a reduced cell viability, but a very few studies addressed the molecular mechanisms at the basis of anti-VEGF actions. To fill the gap in the literature about this topic, the present PhD project explored the hypothesis that the observed adverse effects following intraocular VEGF blockade might be related to the alteration of neurotrophic pathways. With this aim, the effects of intracameral (IC) or intravitreal (IVT) injections of the anti-VEGF drugs aflibercept and ranibizumab were performed in rabbits to investigate their effects on the cornea (Study I) and the retina (Study II). In summary, the results of molecular and histological analysis revealed a decreased cell viability and increased levels of apoptosis and autophagy markers in the corneal endothelium and retina. These effects were associated with an unbalance in the expression of both pro/mature NTs, and the receptors p75 neurotrophin receptor (p75NTR) and tropomyosin receptor kinase A/B (TrkA/B). These structural and molecular changes were stronger after aflibercept injection than following the ranibizumab one, probably due to the difference related to drug structures and molecular targets. These data suggest that anti-VEGF- dependent impairment in neurotrophic signalling could be responsible for the activation of death pathways in ocular tissues, and corroborate the integrate activity of VEGF and the NTs nerve growth factor/brain derived neurotrophic factor (NGF/BDNF) in ocular homeostasis. To further characterise the NGF/VEGF mechanism, a study addressed to evaluate the effects of treatment with NGF in retina degeneration has been part of the PhD project. Since today, the recombinant human NGF (rhNGF) produced by Dompé Farmaceutici - the industrial partner of this Industrial PhD course – is the first approved drug to treat neurotrophic keratitis (NK), a rare disorder of the eye. This molecule has been used to perform Study III, where different routes of administration of rhNGF, such as ocular and systemic, intraperitoneal and subcutaneous, were tested in an animal model of glaucoma. Study III is actually ongoing and the related results are Dompé Farmaceutici’s intellectual property.