Conjugated polymers mediate intracellular Ca 2+ signals in circulating endothelial colony forming cells through the reactive oxygen species-dependent activation of Transient Receptor Potential Vanilloid 1 (TRPV1).

Endothelial colony forming cells (ECFCs) represent the most suitable cellular substrate to induce revascularization of ischemic tissues. Recently, optical excitation of the light-sensitive conjugated polymer, regioregular Poly (3-hexyl-thiophene), rr-P3HT, was found to stimulate ECFC proliferation and tube formation by activating the non-selective cation channel, Transient Receptor Potential Vanilloid 1 (TRPV1). Herein, we adopted a multidisciplinary approach, ranging from intracellular Ca ²⁺ imaging to pharmacological manipulation and genetic suppression of TRPV1 expression, to investigate the effects of photoexcitation on intracellular Ca ²⁺ concentration ([Ca ²⁺ ] _i ) in circulating ECFCs plated on rr-P3HT thin films. Polymer-mediated optical excitation induced a long-lasting increase in [Ca ²⁺ ] _i that could display an oscillatory pattern at shorter light stimuli. Pharmacological and genetic manipulation revealed that the Ca ²⁺ response to light was triggered by extracellular Ca ²⁺ entry through TRPV1, whose activation required the production of reactive oxygen species at the interface between rr-P3HT and the cell membrane. Light-induced TRPV1-mediated Ca ²⁺ entry was able to evoke intracellular Ca ²⁺ release from the endoplasmic reticulum through inositol-1,4,5-trisphosphate receptors, followed by store-operated Ca ²⁺ entry on the plasma membrane. These data show that TRPV1 may serve as a decoder at the interface between rr-P3HT thin films and ECFCs to translate optical excitation in pro-angiogenic Ca ²⁺ signals.
(Copyright © 2021. Published by Elsevier Ltd.)