Loss of pericytes in the early phases of diabetic retinopathy (DR) may disrupt their stable association with endothelial cells (EC), leading to EC proliferation and, eventually, angiogenesis. Extracellular vesicles (EV) are small membrane particles derived from different cells which contain biologically active proteins and RNA and are known to promote phenotypic changes in target cells. In diabetic-like conditions, EV derived from MSC may play a role in vessel destabilization by interfering with the strict interactions between EC/pericytes and pericyte/extracellular matrix.
We examined the behaviour of retinal pericytes exposed to EV derived from MSC cultured in physiological and diabetic-like conditions (high glucose and/or hypoxia).
MSC-derived EV are able to enter the pericytes, cause their detachment and migration from the substrate, and increase blood-barrier permeability. Moreover, EV added to EC/pericytes co-cultures in Matrigel promote in vitro angiogenesis. These effects may be mediated by matrix metalloproteinase-2, expressed by both EV and EV-stimulated pericytes, and are exacerbated if MSC are previously cultured in conditions (high glucose and/or hypoxia) mimicking the diabetic microvascular milieu.
We confirm that MSC-derived EV contribute to angiogenesis, showing that they may not only exert a direct stimulus to EC proliferation, but also induce pericyte detachment, thus leaving EC free to proliferate. In addition, we demonstrate a possible link between EV and the early stages of the pathogenesis of DR. Diabetic-like conditions may influence vessel remodelling during angiogenesis through EV paracrine signalling.