Pilot assessment of a human extracellular matrix-based vascular graft in a rabbit model.

BACKGROUND: Herein we describe a small-diameter vascular graft constructed from rolled human amniotic membrane (hAM), with in vitro evaluation and subsequent in vivo assessment of its mechanical and initial biologic viability in the early postimplantation period. This approach for graft construction allows customization of graft dimensions, with wide-ranging potential clinical applicability as a nonautologous, allogeneic, cell-free graft material. METHODS: Acellular hAMs were rolled into layered conduits (3.2-mm diameter) that were bound with fibrin and lyophilized. Constructs were seeded with human smooth muscle cells and cultured under controlled arterial hemodynamic conditions in vitro. Additionally, the acellular hAM conduits were surgically implanted as arterial interposition grafts into the carotid arteries of immunocompetent rabbits. RESULTS: On in vitro analysis, smooth muscle cells were shown to adhere to, proliferate within, and remodel the scaffold during a 4-week culture period. At the end of the culture period, there was histologic and biomechanical evidence of graft wall layer coalescence. In vivo analysis demonstrated graft patency after 4 weeks (n = 3), with no hyperacute rejection or thrombotic occlusion. Explants displayed histologic evidence of active cellular remodeling, with endogenous cell repopulation of the graft wall concurrent with degradation of initial graft material. Cells were shown to align circumferentially to resemble a vascular medial layer. CONCLUSIONS: The vascular grafts were shown to provide a supportive scaffold allowing cellular infiltration and remodeling by host cell populations in vivo. By use of this approach, "off-the-shelf" vascular grafts can be created with specified diameters and wall thicknesses to satisfy specific anatomic requirements in diverse populations of patients.

Association of magnesium in serum and urine with carotid intima-media thickness and serum lipids in middle-aged and elderly Chinese: a community-based cross-sectional study.

OBJECTIVE: Previous studies suggested that magnesium (Mg) might protect against atherosclerosis, but data were scarce in an Asian population. We examined the association of Mg levels in serum and urine with carotid intima-media thickness (cIMT) and serum lipids in Chinese adults. METHODS: This community-based cross-sectional study recruited 2,837 participants aged 40-75 years in Guangzhou, China. General information, lifestyle factors, serum and urinary concentrations of Mg and cardiometabolic factors were determined. The cIMTs of the common carotid artery (CCA) and the carotid bifurcation (BIF) were measured ultrasonographically. RESULTS: The mean (SD) concentration of serum Mg was 0.85 (0.07) mmol/L and median (IQR) for urinary Mg excretion was 2.29 (1.56-3.51) mmol/L. After adjustment for potential covariates, both serum and the urinary concentrations of Mg were inversely associated with CCA-IMT, but not with BIF-IMT. The regression coefficients (standard errors) were -100 (29) µm (total), -86 (34) µm (women) and -117 (52) µm (men) CCA-IMT per 1 mmol/L of serum Mg, and -41 (8) µm (total), -41 (10) µm (women) and -44 (15) µm (men) CCA-IMT per 1 unit of urinary Mg/creatinine (log mmol/mmol) (all p < 0.05), respectively. Higher serum Mg levels were associated with higher total cholesterol, HDLc, LDLc and triglyceride, but lower non-HDLc/HDLc in total population (all p < 0.05). Similar relationships of urinary Mg with lipoproteins were also found in total population (all p < 0.05). CONCLUSION: Higher levels of serum and urinary Mg are associated with lower CCA-IMTs, and the role of Mg in lipid metabolism needs further investigation.

Cardiovascular risk in nonobese hypertensive adolescents: a study based on plasma biomarkers and ultrasonographic assessment of early atherosclerosis.

The objective of this study was to investigate the vascular status, left-ventricular mass and biomarkers of endothelial activation in hypertensive (HT) adolescents, with particular attention to comparing nonobese with obese patients. Seventy-nine newly diagnosed HT adolescents aged 15.1±2.1 years (divided into 34 nonobese and 45 obese) were compared with 35 healthy volunteers. Intima-media thickness (IMT), flow-mediated dilation (FMD) and left-ventricular mass index (LVMi) were determined using ultrasound. Adhesion molecules and inflammatory interleukins (ILs), together with lipids and insulin resistance (HOMA), were also studied. HT obese adolescents had higher triglycerides, HOMA, and elevated levels of interleukin-6, tumor necrosis factor-α, soluble intercellular adhesion molecule-1 and soluble E-selectin compared with controls and nonobese HT patients. FMD was lower in HT groups (8.5±4.5% in nonobese, P=0.004; 8.1±4.9%, P=0.01 in obese vs 12.5±4.9%; in control), and IMT was higher (0.52±0.06 mm, P<0.001 in nonobese; 0.54±0.05 mm, P<0.001 in obese vs 0.42±0.05 mm in control). Higher LVMi was found in both HT groups, with the highest value in the nonobese group being 37.8±5.3 g m(-2.7) vs 28.4±5.3 g m(-2.7) in controls (P=0.003). In conclusion, nonobese HT adolescents had the same early cardiovascular deteriorations assessed ultrasonographically as their obese HT peers, although metabolic alterations and endothelial activation measured as plasma biomarkers were more pronounced in obese individuals. The potential mechanisms of early atherosclerosis in nonobese HT adolescents need further evaluation in prospective studies because these factors may differ considerably from those found in young obese individuals with HT.

Mechanical assessment of elastin integrity in fibrillin-1-deficient carotid arteries: implications for Marfan syndrome.

AIMS: Elastin is the primary component of elastic fibres in arteries, which contribute significantly to the structural integrity of the wall. Fibrillin-1 is a microfibrillar glycoprotein that appears to stabilize elastic fibres mechanically and thereby to delay a fatigue-induced loss of function due to long-term repetitive loading. Whereas prior studies have addressed some aspects of ageing-related changes in the overall mechanical properties of arteries in mouse models of Marfan syndrome, we sought to assess for the first time the load-carrying capability of the elastic fibres early in maturity, prior to the development of ageing-related effects, dilatation, or dissection. METHODS AND RESULTS: We used elastase to degrade elastin in common carotid arteries excised, at 7-9 weeks of age, from a mouse model (mgR/mgR) of Marfan syndrome that expresses fibrillin-1 at 15-25% of normal levels. In vitro biaxial mechanical tests performed before and after exposure to elastase suggested that the elastic fibres exhibited a nearly normal load-bearing capability. Observations from nonlinear optical microscopy suggested further that competent elastic fibres not only contribute to load-bearing, they also increase the undulation of collagen fibres, which endows the normal arterial wall with a more compliant response to pressurization. CONCLUSION: These findings support the hypothesis that it is an accelerated fatigue-induced damage to or protease-related degradation of initially competent elastic fibres that render arteries in Marfan syndrome increasingly susceptible to dilatation, dissection, and rupture.