Inhibition of extracellular matrix integrity attenuates the early phase of aortic medial calcification in a rodent model.

Abstract Background and aims The mechanism of vascular calcification (VC) resembles that of bone metabolism, and a correlation has frequently been reported between calcification and vascular extracellular matrix (ECM) regulating its integrity; however, the detailed mechanisms remain unclear. In this study, we examined how the vascular ECM, especially collagen metabolism, is involved in the process of VC. Methods VC was modeled using 5-week-old male Sprague–Dawley rats fed a diet containing warfarin and vitamin K1 (WVK). Additionally, β-aminopropionitrile (BAPN) was administered to inhibit lysyl oxidase (LOX), which is an enzyme that mediates collagen cross-linking. Harvested aortic samples were analyzed by staining with alizarin red (AR), immunohistochemistry (IHC), transmission electron microscopy (TEM), and ex vivo microcomputed tomography (μCT). Results Rats fed WVK developed increasing numbers of aortic medial calcifications (AMCs) over time. TEM images indicated punctate calcification within collagen fibers in the early phase of AMC. AR staining of translucent samples revealed the distribution and severity of calcification, and these lesions were significantly decreased in the BAPN group. Three-dimensional reconstructed μCT images that allowed the quantification of calcified volumes revealed that BAPN significantly reduced the bulk of calcification. Moreover, IHC showed that both LOX and collagen I were present around the sites of AMC, and thus the IHC-positive area was reduced in the BAPN group compared to the WVK group. Conclusions The results indicated that inhibition of LOX by BAPN attenuated AMC, and that collagen metabolism plays a significant role in the early pathogenesis of VC.