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Jennifer Durham, Ira Herman; Manipulating Pericyte Contractility Alters Endothelial Growth and Angiogenic Potential. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5571.
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© ARVO (1962-2015); The Authors (2016-present)
Diabetic retinopathy continues to be the leading cause of adult-onset blindness, globally. Photocoagulation therapies destroy pathologic vessels through laser ablation, yet pose risks for retinal detachment, while chronic anti-VEGF treatment may impair neural retinal survival/function. Thus, it is imperative to divulge mechanisms driving pathologic angiogenesis, to discover innovative medicines capable of preventing/protecting retinal function by promoting microvascular stability. To these ends, we investigated the role of retinal pericyte (RP) contractility on retinal endothelial cell (REC) dynamics and angiogenic potential.
As the myosin-phosphatase RhoA interacting protein, MRIP, has been shown to regulate the RhoA/ROCK mediated inactivation of the myosin phosphatase and muscle cell contractility, we employed siRNA to silence MRIP in RP. We combined 2D and 3D co-culture based approaches in combination with biophysical, biochemical and high-resolution imaging to assess the role of RhoGTP and cytoskeletal effectors in modulating RP-REC interactions and angiogenic activation in vitro.
MRIP silencing induces RP hypertrophy including stress fiber assembly with increased isoactin incorporation/expression. MRIP-silencing also induces a marked enhancement in force generation since there is a 2.2 fold increase in substrate deformation. When MRIP-silenced RP are co-cultured with REC there is a ~2.5 fold increase in endothelial cell cycle re-entry. Similarly, MRIP-silenced RP induce a 1.5 fold increase in angiogenic sprouting when cells are placed together in a 3D model of angiogenesis.
Altering RP contractile phenotype via manipulation of the Rho GTP cytoskeletal effector pathway markedly promotes angiogenesis, in part, by stimulating endothelial cell-cycle re-entry and angiogenic sprouting. Thus, subtle changes in RP mechanochemistry could represent key, initiating events in re-activating REC proliferation, promoting diabetes-induced, pathologic angiogenesis. In turn, this paradigm-shifting hypothesis suggests a mechanical component to the ‘angiogenic switch’ and calls into question whether pericyte loss/dropout is required for ocular pathologic angiogenic induction. Furthermore, we envision that manipulating RP cytoskeletal effector function could represent an innovative cell-based therapy for preventing and/or protecting retinal function during diabetes.
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