Valeria Mastrullo

Despite the steady increase in the number of studies focusing on the development of tissue engineered constructs, solutions delivered to the clinic are still limited. Specifically, the lack of mature and functional vasculature greatly limits the size and complexity of vascular scaffold models. If tissue engineering aims to replace large portions of tissue with the intention of repairing significant defects, a more thorough understanding of the mechanisms and players regulating the angiogenic process is required in the field. This review will present the current material and technological advancements addressing the imperfect formation of mature blood vessels within tissue engineered structures.

Dengue is the most prevalent arthropod-borne viral disease affecting humans, with severe dengue typified by potentially fatal microvascular leakage and hypovolaemic shock. Blood vessels of the microvasculature are composed of a tubular structure of endothelial cells ensheathed by perivascular cells (pericytes). Pericytes support endothelial cell barrier formation and maintenance through paracrine and contact-mediated signalling, and are critical to microvascular integrity. Pericyte dysfunction has been linked to vascular leakage in noncommunicable pathologies such as diabetic retinopathy, but has never been linked to infection-related vascular leakage. Dengue vascular leakage has been shown to result in part from the direct action of the secreted dengue virus (DENV) non-structural protein NS1 on endothelial cells. Using primary human vascular cells, we show here that NS1 also causes pericyte dysfunction, and that NS1-induced endothelial hyperpermeability is more pronounced in the presence of pericytes. Notably, NS1 specifically disrupted the ability of pericytes to support endothelial cell function in a 3D microvascular assay, with no effect on pericyte viability or physiology. These effects are mediated at least in part through contact-independent paracrine signals involved in endothelial barrier maintenance by pericytes. We therefore identify a role for pericytes in amplifying NS1-induced microvascular hyperpermeability in severe dengue, and thus show that pericytes can play a critical role in the aetiology of an infectious vascular leakage syndrome. These findings open new avenues of research for the development of drugs and diagnostic assays for combating infection-induced vascular leakage, such as severe dengue.