Advanced glycation end products, aortic stiffness, and wave reflection in peritoneal dialysis as compared to hemodialysis.

BACKGROUND: Modification of vascular extracellular matrix by advanced glycation end products (AGEs) may result in vascular stiffness. Because of higher exposure to glucose, we hypothesized that patients on peritoneal dialysis (PD) may have higher tissue levels of AGEs, increased vascular stiffness, and enhanced central augmentation pressure as compared to hemodialysis patients (HD). METHODS: In a cross-sectional study, 43 PD were matched to 43 HD based on age, gender, diabetes, and dialysis vintage. Tissue levels of AGEs were assessed by skin autofluorescence (skin AF). Aortic stiffness was measured by carotid-femoral pulse wave velocity (cf-PWV), and heart rate-adjusted augmentation pressure (AP@75) was performed by arterial tonometry. RESULTS: Baseline characteristics were similar in both groups except for lower prevalence of cardiovascular disease (CVD) and higher exposure to smoking in PD. Skin AF and cf-PWV were not statistically different, but PD patients had a lower AP@75 (P = 0.023). However, after adjustments for prevalence of CVD and smoking status, skin AF was higher in PD by 0.587 AU (95 % CI 0.091-1.215, P = 0.020), and cf-PWV was higher in PD by 2.20 m/s (95 % CI 0.56-3.84, P = 0.009), while AP@75 was not different. Overall, there was a significant association between skin AF and cf-PWV and AP@75. CONCLUSION: Skin AF and aortic stiffness were higher in PD after adjustments for imbalances in baseline characteristics. Independent of dialysis modality, there was a positive association between skin AF, aortic stiffness, and enhanced wave reflection.

Determinants of progression of aortic stiffness in hemodialysis patients: a prospective longitudinal study.

Aortic stiffness is associated with increased cardiovascular mortality in patients with chronic kidney disease. However, the rate of progression of arterial stiffness and the role of cardiovascular risk factors in the progression of arterial stiffness has never been established in a longitudinal study. In a prospective, longitudinal, observational study, carotid-femoral pulse wave velocity and carotid-radial pulse wave velocity were assessed in 109 hemodialysis patients at baseline and after a mean follow-up of 1.2 years. We examined the impact of age, atherosclerotic cardiovascular disease, diabetes mellitus, dialysis vintage, and pentosidine (a well-characterized, advanced glycation end products) on the rate of progression of aortic stiffness. The annual rate of changes in carotid-femoral pulse wave velocity and carotid-radial pulse wave velocity were 0.84 m/s per year (95% confidence interval, 0.50-1.12 m/s per year) and -0.66 m/s per year (95% confidence interval, -0.85 to -0.47 m/s per year), respectively. Older subjects, and patients with diabetes mellitus or atherosclerotic cardiovascular disease had higher aortic stiffness at baseline, however, the rate of progression of aortic stiffness was only determined by plasma pentosidine levels (P=0.001). The degree of baseline aortic stiffness was a significant determinant of the regression of brachial stiffness (P<0.001) suggesting that the regression of brachial stiffness occurs in response to central aortic stiffness. These findings suggest that traditional cardiovascular risk factors may play some role in the progression of aortic stiffness before development of advanced chronic kidney disease, and that the enhanced rate of progression of aortic stiffness in chronic kidney disease patients on dialysis are probably determined by more specific chronic kidney disease-related risk factors such as advanced-glycation end products.

Normal human Merkel cells are present in epidermal cell populations isolated and cultured from glabrous and hairy skin sites.

The Merkel cell is a highly specialized cell that primarily acts as a slowly adapting mechanoreceptor. Merkel cells are scarce in normal skin but can be identified by the expression of distinct keratin filaments. Merkel cells constitute a very unique population and many questions still remain as to their origin, number, proliferative capacity, and functions in cutaneous biology. The dissociation of epidermal cells from skin is a widely used technique to extract and culture keratinocytes. We took advantage of a two-step extraction method to quantify keratin-20-expressing Merkel cells among total cutaneous cells obtained from either hairy or glabrous skin biopsies. Flow cytometry analysis revealed that keratin-20-labeled Merkel cells represent between 3.6% and 5.7% of freshly dissociated basal epidermal cells. No significant differences were seen between samples derived from glabrous palmar and hairy anatomic sites, from children and adult, respectively. We also report on the presence of Merkel cells in primary and first subcultures of epidermal cells indicating their capacity to remain viable after extraction from skin of various anatomic sites. To our knowledge, this is the first demonstration of nontumorigenic human Merkel cells in culture in vitro. The persistence of a small number of Merkel cells in culture suggests that, with the development of appropriate culture conditions, these cells could be amplified and further studied to unravel long-standing questions relative to their paracrine function or epithelial origin.