TGFβ signaling impacts barrier stability by regulating the endothelial – myeloid cell interplay

• Applicant: Professorin Dr. Barbara Braunger
• Subject Area: Nuclear Medicine, Radiotherapy, Radiobiology ; Ophthalmology ; Endocrinology, Diabetology, Metabolism
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 502316201

Age-related macular degeneration (AMD) is one of the leading causes of blindness in western nations. In the late course of the disease, choroidal neovascularization (CNV) may sprout into the retina, causing additional damage to the function of retinal neurons. For CNV development, at least two events must occur: (1) proliferation of endothelial cells and (2) disruption of barrier structures such as the Bruch's membrane and the outer blood-retinal barrier. The currently recommended therapy for CNV involves regular intraocular injections. However, up to 33% of affected patients are not responsive to these injections and thus hardly treatable. My group recently showed that conditional deletion of transforming growth factor (TGF)-beta receptor 2 (TGFBR2) and thus inhibition of the TGFb signaling pathway specifically in endothelial cells leads to spontaneously developing CNV. Moreover, published and our preliminary data show that numerous myeloid cells accumulate close to these CNV. We therefore hypothesize that the TGFb signaling pathway in endothelial cells and/or the interaction of Tgfbr2-deficient endothelial cells and myeloid cells is essential to inhibit uncontrolled endothelial proliferation and to ensure the strength of barrier structures. To this end, we will perform in vitro, ex vivo, and in vivo experiments. In choroidal endothelial cells, we will analyze proliferation, migration, transcriptional changes, and extracellular matrix barrier integrity in relation to the TGFb signaling pathway. We will use ex vivo aortic ring assays to study the interaction of endothelial cells and myeloid cells (adventitial macrophages) and determine proliferation area and capacity at mouse aortic rings. In addition, myeloid cells will be depleted using a specific inhibitor. Furthermore, we will investigate in vivo whether depletion of myeloid cells modulates the phenotype of CNV development in a mouse model. Here, single cell RNA analysis will provide us with valuable information on transcriptional changes of different cell populations of the retina and choroid in dependence of the TGFb signaling pathway and with and without depletion of myeloid cells.Our analysis of the interplay between endothelial and myeloid cells and their influence on pathomechanisms leading to CNV formation will provide valuable information to the cell population driving the progression of the disease. In particular, RNAseq/single cell analyses will provide important information about transcriptional changes in cell types that promote proliferation and/or barrier disruption. Thus, we will identify potential new therapeutic options that will also be applicable to other pathologies associated with vascular proliferation and barrier destruction, in the eye and beyond.

• DFG Programme: Research Grants