Cellular aspects of vascular remodeling in hypertension revealed by confocal microscopy

Cellular aspects of remodeling in intact arteries have not been fully investigated, mainly due to the lack of an appropriate methodology that allows for simple measurements. The aim of this study was to develop a method based on laser scanning confocal microscopy (LSCM), compare it with previous methodology, and apply it to the study of remodeling in hypertension. The morphology of mesenteric resistance arteries from stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto rats (WKY) was determined with wire myography on one segment with a standardized diameter setting (0.9[d100]) and with perfusion myography on a second segment from the same artery at the calculated equivalent pressure. The second segments were stained with the nuclear dye Hoechst 33342 (live tissue) or propidium iodide (fixed tissue) and measured with LSCM and MetaMorph software. Compared with wire myography, perfusion myography showed similar differences from those previously reported. Compared with LSCM, perfusion myography showed a similar lumen but significantly smaller wall thickness in both live and fixed tissue, probably due to measurement underestimation. In the study with LSCM, arteries from SHRSP compared with those from WKY showed (1) reduced lumen, (2) altered cell density that was significantly increased in the adventitia, decreased in the media, and unchanged in the intima, (3) significantly increased medial volume, (4) significantly smaller endothelial cell nuclei, and (5) adventitial-like cells in the media. We conclude that (1) LSCM is a reliable and straightforward method to study morphology in intact vessels, (2) it provides new information on the cellular changes in remodeling, (3) adventitia might play an active role in the process of remodeling in hypertension, and (4) endothelium "remodels" in hypertension.