Identification of class III β-tubulin as a marker of angiogenic perivascular cells.

A full understanding of the functional role for pericytes in microvascular network growth requires identifying the specific cell phenotypes involved in angiogenesis. The objective of this study was to evaluate class III β-tubulin expression along remodeling adult rat mesenteric microvascular networks. Mesenteric tissues were harvested from unstimulated adult male Wistar rats and at 2, 10 and 30 days post-compound 48/80 stimulation (n=4 per experimental group). Tissues were immunohistochemically labeled with antibodies for class III β-tubulin, NG2 and PECAM. In unstimulated microvascular networks, class III β-tubulin was nerve specific, and did not identify vascular cells along PECAM positive arterioles, venules, and capillaries. Two days post 48/80 stimuli, class III β-tubulin labeling of perivascular cells, including pericytes and smooth muscle cells, was observed along capillary sprouts, capillaries, venules, and arterioles in network regions characterized by increased vessel density and tortuosity. Pericyte identity along capillaries and capillary sprouts was confirmed by cell morphology and co-labeling with NG2. The percentage of vessels with class III β-tubulin positive labeling decreased at subsequent time points and temporally correlated with the time course of capillary sprouting. The results identify class III β-tubulin as a marker of angiogenic perivascular cells and suggest that specific pericyte phenotypes are associated with capillary sprouting.