Matrix biophysics and pericyte mechanobiology in (patho)physiological angiogenesis

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PROJECT SUMMARY The long-term arc of this project is expected to engineer vascularization of tissue deficits and advance treatment of microvascular diseases including myocardial infarction, atherosclerosis, pulmonary arterial hypertension, aneurysm, peripheral artery disease, bone repair, volumetric muscle loss, diabetic wounds, and cancer. To achieve this goal, the project will advance our fundamental understanding of how local fibrous extracellular matrix (ECM) biophysical cues dynamically influence pericytes during neovessel formation. The role of the endothelial cell in vasculogenesis and angiogenesis is well recognized, yet the pericyte’s full scope of work is less understood, despite its known essential role in proper vascular development. We made a surprising observation that pericytes exhibit phenotypic plasticity when they spontaneously assemble into 3D spheroids and reversibly form and adopt endothelial markers when cultured on native and synthetic fibrous biomaterials in vitro, but not on 2D substrates. Akin to vasculogenic blood islands, tip cell-like protrusions sprout and retract from these spheroids comprised of pericytes that transdifferentiate to express endothelial markers. Other studies by our team revealed that matrix fiber diameter and architecture dictate cell morphology, the mode and rate of cell migration, cell force exertion, protrusion dynamics, and nuclear shape associated with heterochromatic rearrangements. These published and preliminary studies gave rise to a central hypothesis that various matrix biophysical parameters differentially direct neovessel formation by modulating pericyte migration, contraction, protrusion, and phenotypic plasticity. To test this hypothesis, we will further develop a nanofiber cell force sensing platform to mimic (patho)physiological ECMs through exquisite tunable control of ECM fiber biophysical parameters (e.g., diameter, density, alignment). With consideration of disease-simulating biochemical milieu (e.g., oxygen tension, reactive oxygen species, and inflammatory cytokines), experiments performed under Aim 1 will identify how matrix biophysical cues alter pericyte migration, contractility, and protrusion dynamics. Aim 2 experiments will develop the in vitro nanofiber scaffold system to selectively transplant patterned spheroids in vivo for neovessel formation through engineered control of pericyte plasticity and transdifferentiation. The project’s translational impact will be novel methods of controlling microvascular expansion and regression in diseased, damaged, and engineered tissues.