Les effets anti-angiogéniques des microparticules dérivées des lymphocytes T sur la néovascularisation choroïdienne

In developed countries, choroidal neovascularization (CNV) is the most common cause of irreversible vision loss for individuals aged 50 or older. This pathology involves the formation of new blood vessels that originate from the choroid and penetrate Bruch's membrane as well as the retinal pigment epithelium (RPE) layer, after which it invades the sub-retinal space. Despite extensive research, the pathogenesis and risk factors causing CNV are still unknown. While various genetic and environmental factors have been identified, current treatment is limited to intravitreal administration of anti-VEGF molecules (antibodies binding and sequestrating this growth factor). Nonetheless, blocking VEGF signaling pathway can cause alterations in the existing vascular network that maintain choroidal health and neuron survival. Our laboratory has long been focusing on developing a new anti-angiogenic therapy based on lymphocyte microparticles (LMPs). In summary, microparticles are membrane fragments released into the vascular network during activation process or apoptosis and are responsible for various biological functions. Our team has previously demonstrated the anti-angiogenic effect of LMPs in several models of corneal neovascularization, retinopathy of prematurity and cancer. The objective of this thesis was to determine the anti-angiogenic potential of LMPs in ex vivo and in vivo models of induced CNV. We then focused on how the LMPs modulate their angiogenic microenvironment in these models. In the first study we demonstrated the anti-angiogenic effect of LMPs in an ex vivo model of choroid explant. Our results indicated that the anti-angiogenic effect originates mainly from the RPE and that PEDF and NGF, derived factors from RPE, and the p75NTR receptor play key roles in LMPs signalling pathway. Our findings demonstrated that the inhibition of PEDF and p75NTR completely abolish the anti-angiogenic effect of the LMPs. In the second study, we focused on understanding how LMPs modulate their inflammatory environment to initiate this effect in a CNV in vivo model. Firstly, we demonstrated the anti-angiogenic effect of LMP in a laser-induced CNV in vivo model. Secondly, we assessed the inflammatory component of CNV and further investigated the effect of LMPs on macrophage polarization. Our in vivo and in vitro results showed that LMPs polarized macrophages towards an M1 phenotype associated with an anti-angiogenic response. Lastly, we found that CD36 receptor signaling pathway is responsible for the anti-angiogenic effect of the LMPs. Our results showed that blocking this receptor abolished the anti-angiogenic effect of macrophage treated with LMPs. In conclusion, this doctoral thesis demonstrates the anti-angiogenic effect of LMPs through the release of anti-angiogenic neurotrophins by EPR and the modulation of macrophage activation. The presented results set new directions for the development of novel anti-angiogenic treatments of CNV in a VEGF-indepandant manner.

Keyphrases: macrophages, p75NTR, CD36, angiogenesis, microparticles, choroidal neovascularization, macrophages, neurotrophins