Perivascular cells along venules upregulate NG2 expression during microvascular remodeling

Objective: Recently the authors have shown that neuron-glial antigen 2 (NG2) is expressed by perivascular cells along arterioles and capillaries, but not along venules in quiescent rat mesenteric microvascular networks. To investigate how the spatial distribution of this proteoglycan changes during microvascular remodeling, the objective of this study was to characterize the expression of NG2 in adult rat mesenteric microvascular networks undergoing active remodeling. Methods: The distribution of NG2 expression was evaluated in adult rat mesenteric microvascular networks. Tissues were harvested from 250 g, female, Sprague-Dawley rats at 1, 3, and 5 days poststimulation and double immunolabeled for NG2 and CD31 (endothelial cell marker). Results: After 1 day, NG2 expression was observed along 27 +/- 11% of network draining venules (14-55 mu m) and after 3 days, 59 +/- 10% of draining venules (13-59 mu m) stained positive for the proteoglycan. By 5 days poststimulation, the percentage of network draining venules (18-59 mu m) staining positive for NG2 returned to 18 +/- 7%, indicating a downregulation of the proteoglycan toward quiescent levels along larger-sized venules. Conclusions: The results suggest that NG2 proteoglycan expression is transiently upregulated along venules during microvascular remodeling, implicating NG2 as a marker of activated venules.