Physical contact between human vascular endothelial and smooth muscle cells modulates cytosolic and nuclear calcium homeostasis.

The interaction between vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs) plays an important role in the modulation of vascular tone. There is, however, no information on whether direct physical communication regulates the intracellular calcium levels of human VECs (hVECs) and (or) human VSMCs (hVSMCs). Thus, the objective of the study is to verify whether co-culture of hVECs and hVSMCs modulates cytosolic ([Ca2+ ]c ) and nuclear calcium ([Ca2+ ]n ) levels via physical contact and (or) factors released by both cell types. Quantitative 3D confocal microscopy for [Ca2+ ]c and [Ca2+ ]n measurement was performed in cultured hVECs or hVSMCs or in co-culture of hVECs-hVSMCs. Our results show that: (1) physical contact between hVECs-hVECs or hVSMCs-hVSMCs does not affect [Ca2+ ]c and [Ca2+ ]n in these 2 cell types; (2) physical contact between hVECs and hVSMCs induces a significant increase only of [Ca2+ ]n of hVECs without affecting the level of [Ca2+ ]c and [Ca2+ ]n of hVSMCs; and (3) preconditioned culture medium of hVECs or hVSMCs does not affect [Ca2+ ]c and [Ca2+ ]n of both types of cells. We concluded that physical contact between hVECs and hVSMCs only modulates [Ca2+ ]n in hVECs. The increase of [Ca2+ ]n in hVECs may modulate nuclear functions that are calcium dependent.