1. Investigación

Renal fibrosis is characterized by glomerulosclerosis and tubulointerstitial fibrosis and its pathoge-nesis is associated with the activity of mesenchymal cells (fibroblasts), being essentiallycharacterized by a process of excessive accumulation resulting from the deposition of extracellularmatrix components. The aim of this study was to characterize the morphological presentation ofchronic and fibrotic lesions in the glomerular, tubular, interstitial, and vascular compartments infeline CKD, as well as the possible participation of myofibroblasts in renal fibrotic processes in thisspecies. Cat kidneys were collected and processed according to the conventional techniques forlight microscopy, circular polarization, immunohistochemistry, and electron microscopy. Fibroticalterations were present in all compartments analyzed. The main findings in the glomerular com-partment were different degrees of glomerular sclerosis, synechia formation, Bowman’s capsulecalcification, in addition to glomerular basement membrane thickening and pericapsular fibrosis.The tubulointerstitial compartment had intense tubular degeneration and the immunostaining intubular cells for mesenchymal cell markers demonstrated the possibility of mesenchymal epithelialtransition and consequent involvement of myofibroblasts in the development of interstitial tubuledamage. Infiltration of inflammatory cells, added to vessel thickening and fibrosis, demonstratedthe severity and role of inflammation in the development and perpetuation of damage. Thus, wemay conclude that fibrotic lesions play a relevant role in feline CKD and the mechanism of perpet-uation of these lesions need further elucidation regarding the origin and participation ofmyofibroblasts and consequent mesenchymal epithelial transition in this species.

The aim of this study was to evaluate the effect of Compound 21 (C21), a selective AT2R agonist, on the prevention of endothelial dysfunction, extracellular matrix (ECM) remodeling and arterial stiffness associated with diet-induced obesity (DIO). 5-week-old male C57BL/6J mice were fed a standard (Chow) or high-fat diet (HF) for 6 weeks.Half of the animals of each group were simultaneously treated with C21 (1mg/kg/day, in the drinking water), generating 4 groups: Chow C, Chow C21, HF C, HF C21. Vascular function and mechanical properties were determined in the abdominal aorta. To evaluate ECM remodeling, collagen deposition, activity of metalloproteinases (MMP) 2 and 9 and TGF-1 concentration were analyzed in the plasma. Abdominal aortas from HF C mice showed endothelial dysfunction as well as enhanced contractile but reduced relaxant responses to Ang II.This effect was abrogated with C21 treatment by preserving NO availability. A left-shift inthe tension-stretch relationship, paralleled by an augmented β-index (marker of intrinsic arterial stiffness), and enhanced collagen deposition and MMP-2/-9 activities were also detected in HF mice. However, when treated with C21, HF mice exhibited lower TGF-1 levels in abdominal aortas together with reduced MMP activities and collagen deposition compared with HF C mice. In conclusion, these data demonstrate that AT2R stimulation by C21 in obesity preserves NO availability and prevents unhealthy vascular remodeling, thus protecting the abdominal aorta in HF mice against the development of endothelial dysfunction, ECM remodeling and arterial stiffness.

To determine whether overexpression of the chitin degrading enzyme, chitotriosidase (CHIT1), modulates macrophage function and ameliorates atherosclerosis. Using a mouse model that conditionally overexpresses CHIT1 in macrophages (CHIT1-Tg) crossbred with the Ldlr􀀀=􀀀 mouse provided us with a means to investigate the effects of CHIT1 overexpression in the context of atherosclerosis. In vitro, CHIT1 overexpression by murine macrophages enhanced protein expression of IL-4, IL-8, and G-CSF by BMDM upon stimulation with a combination of lipopolysaccharide (LPS) and interferon-g (IFN-g). Phosphorylation of ERK1/2 and Akt was also down regulated when exposed to the same inflammatory stimuli. Hyperlipidemic, Ldlr/--CHIT1-Tg (CHIT1-OE) mice were fed a high-fat diet for 12 weeks in order to study CHIT1 overexpression in atherosclerosis. Although plaque size and lesion area were not affected by CHIT1 overexpression in vivo, the content of hyaluronic acid (HA) and collagen within atherosclerotic plaques of CHIT1- OE mice was significantly greater. Localization of both ECM components was markedly different between groups. These data demonstrate that CHIT1 alters cytokine expression and signaling pathways of classically activated macrophages. In vivo, CHIT1 modifies ECM distribution and content in atherosclerotic plaques, both of which are important therapeutic targets.