Key result
Distal renal arteries show ~15% lower sympathetic nerve density than proximal segments.
Why the study?
The human anatomy of peri-arterial renal sympathetic nerves is poorly understood despite the use of renal sympathetic denervation therapy in resistant hypertension.
Observational (n=20)
Answers are grounded in this paper and cite their sources.
The anatomic distribution of peri-arterial renal nerves shows lower density in distal and dorsal locations with a predominance of efferent fibers, providing important anatomical context for refining renal denervation procedures.
BACKGROUND: Although renal sympathetic denervation therapy has shown promising results in patients with resistant hypertension, the human anatomy of peri-arterial renal nerves is poorly understood. OBJECTIVES: The aim of our study was to investigate the anatomic distribution of peri-arterial sympathetic nerves around human renal arteries. METHODS: Bilateral renal arteries were collected from human autopsy subjects, and peri-arterial renal nerve anatomy was examined by using morphometric software. The ratio of afferent to efferent nerve fibers was investigated by dual immunofluorescence staining using antibodies targeted for anti-tyrosine hydroxylase and anti-calcitonin gene-related peptide. RESULTS: A total of 10,329 nerves were identified from 20 (12 hypertensive and 8 nonhypertensive) patients. The mean individual number of nerves in the proximal and middle segments was similar (39.6 ± 16.7 per section and 39.9 ± 1 3.9 per section), whereas the distal segment showed fewer nerves (33.6 ± 13.1 per section) (p = 0.01). Mean subject-specific nerve distance to arterial lumen was greatest in proximal segments (3.40 ± 0.78 mm), followed by middle segments (3.10 ± 0.69 mm), and least in distal segments (2.60 ± 0.77 mm) (p < 0.001). The mean number of nerves in the ventral region (11.0 ± 3.5 per section) was greater compared with the dorsal region (6.2 ± 3.0 per section) (p < 0.001). Efferent nerve fibers were predominant (tyrosine hydroxylase/calcitonin gene-related peptide ratio 25.1 ± 33.4; p < 0.0001). Nerve anatomy in hypertensive patients was not considerably different compared with nonhypertensive patients. CONCLUSIONS: The density of peri-arterial renal sympathetic nerve fibers is lower in distal segments and dorsal locations. There is a clear predominance of efferent nerve fibers, with decreasing prevalence of afferent nerves from proximal to distal peri-arterial and renal parenchyma. Understanding these anatomic patterns is important for refinement of renal denervation procedures.
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Sakakura et al. (2014) conducted an observational in Hypertension (n=20). Anatomic location (distal vs proximal/middle segments) vs. Proximal and middle segments was evaluated on Number of nerves per section (p=0.01). Peri-arterial renal sympathetic nerve density was lower in distal segments compared to proximal segments (33.6 vs 39.6 nerves per section; p=0.01), with a predominance of efferent fibers.
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