Figure: Inferior epigastric arteries stained with VVG for elastic fibres; representative images a-b pre-emptive group; c-d dialysis group.

DIFFERENCES IN ELASTIC FIBRES IN THE ARTERIAL SMOOTH MUSCLE LAYER BETWEEN PATIENTS WITH PRE-DIALYSIS AND DIALYSIS-DEPENDENT CKD.

INTRODUCTION: Loss of arterial compliance is strongly associated with death in patients with chronic kidney disease (CKD). In mice with experimentally induced uraemia loss of elastin fibres precedes medial calcification. Furthermore there have been qualitative reports of altered elastin organisation in human arteries retrieved from patients with CKD. We set out to quantify the differences in elastin fibres initially by measuring width and length of fibres in the arterial smooth muscle layer in elastic arteries retrieved during transplant operations to provide additional insights into the pathophysiological changes in the vessels of CKD patients. METHODS: Inferior epigastric artery samples were retrieved during surgery from patients undergoing live donor renal transplant procedure. Tissues were fixed, paraffin-embedded and 5µm sections cut. Elastic fibres were stained using Verhoeff's Van Gieson Stain (VVG). Fibre thickness was quantified in Image J using the ‘analyze particles’ function. Measurements were log transformed and the assessment of fibre length and width as well as differences between the pre-dialysis and dialysis groups were examined using a mixed linear regression model using a random intercept and lengths/widths clustered within subjects. RESULTS: Arterial samples were collected from 18 live donor kidney recipients (7 female, 11 male, mean age 47.7 years); 6 pre-emptive and 12 on dialysis (4 haemodialysis and 8 peritoneal dialysis). Overall the geometric mean fibre width was 5.9μm (95% CI: 4.9-7.0) and fibre length 6.7μm (95% CI: 5.5-8.0) (Figure). Dialysis patients demonstrated both thinner and shorter length fibres in the sections analyzed (Table).

Dialysis Pre-dialysisGeometric mean µm 95% CI Geometric Mean μm 95% CI P-value

Fibre Width 4.9 4.2-5.8 8.3 6.2-10.9 <0.001Fibre Length 5.8 4.9-6.8 8.7 6.0-12.5 0.03

CONCLUSION: We used a 2-dimensional approach so apparent differences in fibre length could also represent changes in 3-dimensional fibre organization. However, consistent with previous qualitative reports we found thicker medial elastic fibers in patients transplanted pre-emptively. These data suggest elastin fibre thinning may be the consequence of dialysis requiring CKD. Investigating these processes in greater detail may provide important clues to the understanding of the pathogenesis of CKD-associated vascular disease. 1 Pai A. Am J Pathol. 2011 178:764-773. 2 London GM. Nephrol Dial Transplant. 2002 17:1713-24.

Table: Geometric mean of fibre width and length in dialysis and pre-dialysis patients, scale bar 200 µm.

3 Chung AW. Circulation. 2009 120:792-801.