Contraction of cerebroparenchymal pericytes and formation of vascular tube

Pericytes were isolated and cultured from the mouse cerebroparenchymal microvessel. The pericytes were cultured three-dimensionally in a collagen gel by adding tensile stress, resulting in reconstruction of narrow stringy fibers. When the contractility of these fibers was isometrically evaluated, they contracted in response to norepinephrine or acetylcholine. However, vascular tubelike structures were formed when pericytes were cultured three-dimensionally in a low-concentration collagen gel without adding mechanical stress. Immunostaining demonstrated that the expression of a-smooth muscle actin, a marker protein of pericytes, decreased with the formation of luminal structures, although the expression of PECAM- 1 and VE-cadherin, marker proteins of the endothelium, increased with the formation of tube-like structures. These findings suggest that cerebroparenchymal pericytes may regulate microcirculation in the cerebral parenchyma by contracting in response to contractile agonists. Moreover, pericytes may also be involved in vascularization in the cerebral parenchyma by transforming into endothelial cells.